JP4427417B2 - Power supply device and induction heating device - Google Patents

Description

  The present invention relates to a power supply device and an induction heating device that supply power of different frequencies.

  2. Description of the Related Art Conventionally, a power supply device that can change the frequency of AC power supplied to a load when controlling the output of one induction load such as an induction motor or induction heating device is known (for example, Patent Document 1).

  In the device described in Patent Document 1, a first converter that supplies a high frequency and a second converter that supplies a medium frequency are connected in parallel to one induction coil. That is, the first converter that supplies high frequency is used as a series resonance circuit, and the medium frequency feedback from the second converter that supplies medium frequency is reduced by a capacitor that compensates the reactive power of the induction coil in series. Yes. Further, a capacitor is connected in parallel to the second converter to compensate the reactive power of the induction coil, and between the second converter and the common contact of the first converter and the second converter. A series circuit of a reactor that suppresses high-frequency feedback and an additional compensation capacitor that compensates for the reactive power of the reactor is connected in series.

Japanese Patent No. 3150968 (page 2 right column-page 3 right column, Fig. 3)

  However, in the thing of the said patent document 1, the power supply or converter which supplies two different frequencies of the 1st converter which supplies a high frequency, and the 2nd converter which supplies a medium frequency is required, Simplification of the structure is desired. In addition, device design is difficult due to mutual interference between converters supplying different frequencies operating simultaneously. That is, the frequency synchronization circuit of the converter on the high frequency side is easily affected by low-frequency AC ripples, so that frequency variation, that is, synchronization instability is likely to occur. In order to reduce the influence of this mutual interference, it is necessary to add a filter circuit to each matching circuit as described above, and it is also required to set both frequencies as far as possible. As described above, the circuit configuration becomes complicated, the apparatus becomes larger, the productivity cannot be improved, and the apparatus cost cannot be reduced, and there are many restrictions on the frequency setting and the versatility is poor.

  An object of the present invention is to provide a power supply device and an induction heating device that can supply AC power of different frequencies with a simple configuration in view of the above-described problems.

The invention according to claim 1 is a power supply device that operates by supplying electric power of different frequencies to an inductive load, and an oscillation circuit unit that outputs AC power of different frequencies, and the induction corresponding to the different frequencies A matching circuit unit that configures a plurality of resonance circuits with a load, and a state in which the frequency of AC power supplied from the oscillation circuit unit to any one of the matching circuit units is controlled at a predetermined resonance frequency. And a control circuit unit , wherein the matching circuit unit includes a transformer that converts a plurality of load resonance impedances into substantially the same oscillator output impedance .

  In the present invention, the control circuit unit is in a state where the resonance circuit of the matching circuit unit constituted by a plurality of inductive loads resonates at a predetermined resonance frequency corresponding to different frequencies of the AC power output from the oscillation circuit unit. Control is performed to output AC power of different frequencies from the oscillation circuit section. As a result, one inductive load can be applied with two different frequencies in one oscillation circuit unit, and the configuration is simplified. Also, there is no need to provide a plurality of oscillation circuit units corresponding to different frequencies, no mutual interference occurs between the oscillation circuit units, the device design is easy, the configuration is simplified, the productivity is improved, and the cost is reduced. Reduction can be easily achieved.

  In the present invention, the matching circuit unit is provided with a transformer for converting the oscillator output impedance to substantially the same as the load resonance impedance of the plurality of resonance circuits. As a result, the maximum power is easily supplied to the inductive load at different frequencies, and the efficient operation of the inductive load is easily obtained.

Invention of Claim 2 is an electric power supply apparatus of Claim 1 , Comprising: The said transformer is connected to the said oscillation circuit part, and the primary winding to which alternating current power is supplied, and several different load And a secondary winding having a tap for converting the resonance impedance into substantially the same oscillator output impedance.

  In the present invention, as the transformer, the primary winding is connected to the oscillation circuit unit, AC power is supplied, and the secondary winding is provided with a tap for converting the load resonance impedance to substantially the same oscillator output impedance. . As a result, it is possible to easily obtain a configuration in which the maximum power is supplied to the inductive load at different frequencies and efficiently operates.

The invention described in claim 3 is the power supply apparatus according to claim 1, wherein the transformer is characterized in that provided in a plurality for each resonant circuit for converting the load resonance impedance to the oscillator output impedance .

  In the present invention, a plurality of transformers having substantially the same oscillator output impedance are provided for each load resonance impedance of the matching circuit section. As a result, frequency currents other than the resonance frequency do not flow, the configuration of the transformer is simplified, and the cost can be easily reduced.

According to a fourth aspect of the present invention, the control circuit unit includes a frequency power ratio control circuit unit that switches a frequency of AC power output from the oscillation circuit unit in accordance with a state in which the inductive load is applied. It is characterized by.

  In the present invention, the frequency power ratio control circuit unit of the control circuit unit switches and controls the frequency of the AC power output from the oscillation circuit unit corresponding to the state in which the inductive load is applied. Thus, frequency synchronization can be easily achieved according to the load target, efficient resonance at different frequencies can be obtained, and an efficient inductive load action can be obtained.

Invention of Claim 5 is the electric power supply apparatus of Claim 4 , Comprising: The said frequency power ratio control circuit part is the setting regarding the state which makes the said inductive load set by the input operation of an input means act A frequency of AC power output from the oscillation circuit unit is set based on an input signal.

  In this invention, when the state in which the inductive load is applied is set by the input operation of the input means, the frequency power ratio control circuit unit sets the frequency of the AC power output from the oscillation circuit unit based on the setting input signal related to this state To do. As a result, the frequency of the AC power to be output can be set as appropriate according to the load target, and versatility is improved.

The invention according to claim 6 is the power supply device according to claim 4 or claim 5 , wherein the frequency power ratio control circuit unit is configured such that a low frequency output frequency output from the oscillation circuit unit has an impedance. given by the low-frequency synchronizing circuit for the frequency characteristic is controlled oscillation frequency of the oscillation circuit to a state where a predetermined series resonance frequency, the frequency characteristic of the output frequency of the predetermined impedance of the high frequency to be outputted from the oscillator circuit to the the high-frequency synchronizing circuit which controls the oscillation frequency of the oscillation circuit to a state where the series resonance frequency, and the frequency electric power control circuit for switching the low and high frequency, comprising the.

In this invention, the low frequency and the high frequency are appropriately switched by the frequency power control circuit, and the output frequency output from the oscillation circuit unit at the low frequency synchronization circuit unit and the high frequency synchronization circuit unit is a frequency characteristic of impedance and a predetermined series resonance frequency. controlling the oscillation frequency of the oscillator circuit portion comprising state. For this reason, with a simple configuration, different frequencies can be easily switched in the frequency power control circuit, and different frequencies can be easily synchronized in the low frequency synchronization circuit unit and the high frequency control circuit unit.

A seventh aspect of the present invention is the power supply apparatus according to any one of the first to third aspects, wherein the control circuit unit sets the frequency of the AC power output from the oscillation circuit unit in units of cycles. And a frequency power ratio control circuit unit that performs switching control in (1).

  In this invention, the frequency power ratio control circuit unit switches and controls the frequency of the AC power output from the oscillation circuit unit on a period basis. As a result, the frequency is controlled to be switched within one cycle, and the inductive load acts appropriately by repeating the cycle, so that a good inductive load can be obtained by the high-speed switching control.

Invention of Claim 8 is the electric power supply apparatus of Claim 7 , Comprising: The said frequency power ratio control circuit part is the setting regarding the state which makes the said inductive load set by the input operation of an input means act Based on the input signal, the time distribution of each frequency to be switched can be changed.

  In the present invention, when a state in which an inductive load is applied is set by an input operation of the input means, the time distribution of each frequency to be switched by the frequency power ratio control circuit unit is changed based on a setting input signal related to this state. As a result, the operating state corresponding to the frequency of the inductive load can be changed, and versatility is improved.

A ninth aspect of the present invention is the power supply device according to any one of the first to eighth aspects, wherein the control circuit unit is connected to the oscillation circuit unit based on a frequency current flowing through the resonance circuit. It controls the frequency of the alternating current power to output.

  In the present invention, the frequency of the AC power output from the oscillation circuit unit is controlled by the control circuit unit based on the frequency currents respectively flowing through the resonance circuits. This facilitates efficient series resonance at different frequencies.

Synchronization invention according to claim 1 0, a power supply device according to claim 9, wherein the control circuit unit, provided in correspondence with each frequency of the AC power supplied from the oscillation circuit unit A control circuit unit; and storage means for storing period information relating to the predetermined frequency when the oscillation circuit unit shifts to an idle period in which AC power is not supplied to the predetermined frequency. On the other hand, the synchronization control circuit unit performs synchronization control based on the synchronization information stored in the storage means when shifting to an operation period in which AC power is supplied.

  In the present invention, when shifting to an idle period in which AC power is not supplied from the oscillation circuit unit to a predetermined frequency, the synchronization information relating to the predetermined frequency is stored in the storage means, and the AC power is supplied to the predetermined frequency. Synchronization control is performed in the synchronization control circuit unit based on the synchronization information stored in the storage means when the period is shifted. As a result, high-speed switching control of different frequencies can be easily obtained, and good effects corresponding to different frequencies of the inductive load can be easily obtained.

The invention according to claim 1 1, a power supply device according to any one of claims 1 to 1 0, wherein the control circuit section changes the output of the AC power to be outputted from the oscillator circuit An output control circuit unit is provided.

  In this invention, the output of the AC power output from the oscillation circuit unit is appropriately changed by the output control circuit unit of the control circuit unit. This makes it possible to set the heating conditions corresponding to the shape of the object to be heated when the object to be heated is induction-heated at different frequencies using an induction heating coil as an induction load, for example. The action state can be changed, and versatility is improved.

Invention according to claim 1 2, a power supply device according to claim 1 1, wherein the oscillation circuit includes a forward conversion circuit for converting the AC power into predetermined DC power, the forward conversion circuit An inverse conversion circuit unit that converts the DC power converted by the unit into predetermined AC power, and the output control circuit unit feedback-controls the output value of the DC power output from the forward conversion circuit unit. To do.

  In the present invention, the output control circuit unit feedback-controls the output of the DC power output from the forward conversion circuit unit of the oscillation circuit unit that converts the DC power converted into the AC power by the inverse conversion circuit unit from the AC power. To change and control the output of the AC power output from the oscillation circuit section. As a result, the output of AC power can be easily changed with a simple configuration.

Conversely The invention according to claim 1 3, a power supply device according to any one of claims 1 to 1 2, wherein the oscillator circuit unit for converting DC power into AC power of voltage square wave A conversion circuit unit is provided.

  In the present invention, the inverse conversion circuit unit of the oscillation circuit unit is a voltage type that converts DC power into voltage square wave AC power. As a result, it is possible to easily switch and output AC power of different frequencies at high speed, and to obtain an efficient inductive load action.

The invention described in claim 1 4, and the power supply device according to any one of claims 1 to 1 3, induction of induction heating an object to be heated by the electric power having different frequencies supplied from the power supply An induction heating device comprising a heating coil.

In this invention, the object to be heated is induction-heated by the induction heating coil with different frequency power supplied from the power supply device according to the present invention . This simplifies the configuration for induction heating, and can easily improve the productivity and reduce the cost.

  According to the present invention, one inductive load is generated by two different frequencies in one oscillation circuit unit in order to output alternating-current power of different frequencies from the oscillation circuit unit in a state where the resonance circuits have a predetermined resonance frequency. The structure can be simplified, the mutual interference between the oscillation circuit portions does not occur, the device design is easy, the structure is simplified, the productivity can be improved, and the cost can be easily reduced.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, for example, an induction heating apparatus that heats a complex material such as gears, screws, bolts, nuts and the like having a plurality of irregularities on the surface as an object to be heated is exemplified. Although explained, not only this but any to-be-heated material can be made into object. In addition to induction heating, the present invention can be applied to a configuration for supplying power to any load. Furthermore, although the structure which supplies electric power with two different frequencies, a low frequency and a high frequency, is demonstrated, it is not restricted to this but electric power can also be supplied with several frequencies.

[First Embodiment]
FIG. 1 is a circuit diagram showing a schematic configuration of the induction heating apparatus in the first embodiment. FIG. 2 is a graph showing frequency characteristics of impedance in the matching circuit unit.

(Configuration of induction heating device)
In FIG. 1, reference numeral 100 denotes an induction heating device. The induction heating device 100 includes an induction heating coil 200 that induction-heats an object to be heated 201, and electric power that supplies the induction heating coil 200 with electric power having a different frequency to induce induction heating. A supply device 300.

  Induction heating coil 200 is connected to power supply device 300. For example, the induction heating coil 200 having an equivalent inductance L0 of several tens to several hundreds of nH is used, and AC power having different frequencies is supplied from the power supply device 300 to induction-heat the object 201 to be heated. In addition, the power supply device 300 includes an oscillation circuit unit 310, a matching circuit unit 320, and a control circuit unit 330.

  The oscillation circuit unit 310, for example, in voltage form, switches and outputs a predetermined different frequency, that is, high frequency and low frequency power from the commercial AC power source e at a high speed with a predetermined duty ratio. The oscillation circuit unit 310 includes a converter 311 as a forward conversion circuit unit, an inverter 312 as a voltage type reverse conversion circuit unit, and a smoothing capacitor Cf. The converter 311 is a forward conversion circuit using, for example, various bridge rectifier circuits, and is connected to the commercial AC power source e to convert the commercial AC power source e into DC power. The converted DC power is appropriately smoothed through the smoothing capacitor Cf and output to the inverter 312. The inverter 312 converts the DC power output from the converter 311 into a single-phase AC power having a constant frequency, for example, a voltage square wave with a frequency of 10 kHz to 300 kHz. Specifically, the inverter 312 includes a transistor (not shown) that is a switching element, and outputs AC power through on / off control of the switching element.

  The matching circuit unit 320 has two different series resonance frequencies corresponding to the low frequency and the high frequency, and the resonance circuit unit 320 resonates in series with the induction heating coil 200 by the high frequency or low frequency power output from the oscillation circuit unit 310. The heated object 201 is induction-heated. The matching circuit unit 320 includes a matching transformer 321, a reactor L, a first capacitor C 1, a second capacitor C 2, and a current transformer 322.

The induction heating coil 200 is connected to the secondary winding 322B of the current transformer 322. When the turn ratio of the secondary winding 322B is N and the equivalent inductance of the induction heating coil 200 is L0, the induction heating coil 200 is connected to the primary side of the current transformer 322 connected to the secondary side. ² The load coil equivalent inductance of L0 is generated. The first capacitor C1 is, for example, several tens of [mu] F, and the impedance is much larger than the second capacitor C2 of several [mu] F, for example, 10 to 20 times larger. Further, the reactor L is, for example, several μH, and the inductance is set larger than the load coil equivalent inductance N ² L0, for example, about 4 to 5 times.

  The matching transformer 321 matches (matches) the impedances of the two resonant frequency loads of the high frequency and the low frequency that are the load resonant impedance and the output impedance of the AC power that is output from the oscillation circuit unit 310 that is the oscillator output impedance. . The matching transformer 321 has the primary winding 321 </ b> A connected to the oscillation circuit unit 310 and receives the converted AC power. In addition, the matching transformer 321 has a tap 321C in the secondary winding 321B, and this tap 321C is provided at the position of the secondary winding 321B corresponding to the two high-frequency and low-frequency resonance frequencies. That is, the matching transformer 321 includes an output equivalent impedance between a pair of output terminals S1 and S2 to which a lead wire (not shown) of the secondary winding 321B is connected, and an output equivalent impedance between the tap 321C and the output terminal S1. have.

  Between the pair of output terminals S1 and S2 to which lead wires (not shown) at both ends of the secondary winding 321B in the matching transformer 321 are connected, the second capacitor C2 and the primary winding 322A of the current transformer 322 are connected. A series circuit is connected. That is, the second capacitor C2 having a relatively small impedance is connected between both ends of the secondary winding 321B having a relatively large output equivalent impedance of the matching transformer 321. A series circuit of the reactor L and the first capacitor C1 is connected between the tap 321C of the matching transformer 321 and the connection point between the first capacitor C1 and the primary winding 322A of the current transformer 322. Yes. That is, a series circuit of the first capacitor C1 and the reactor L having a relatively large impedance is connected between one output terminal S1 of the secondary winding 321B and the tap 321C of the matching transformer 321 whose output equivalent impedance is relatively small. To do.

Thus, the matching circuit section 321, a reactor L, a low-frequency series resonance circuit 325 to the series resonance at a low frequency is constituted by a first capacitor C1 and the load coil equivalent inductance N ² L0, a second capacitor C2 and A high-frequency series resonance circuit 326 configured by a load coil equivalent inductance N ² L 0 and resonating in series at a high frequency is configured. That is, since the low-frequency series resonance circuit 325 has a low load resonance impedance, the low-frequency series resonance circuit 325 is connected between one output terminal S1 of the secondary winding 321B having a large impedance conversion ratio and the tap 321C. Further, the high frequency series resonance circuit 326 is connected between the output terminals S1 and S2 between both ends of the secondary winding 321B having a small impedance conversion ratio because the load resonance impedance is high.

  As described above, the matching circuit unit 320 has different resonance impedances for the two low-frequency and high-frequency resonance frequencies by the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326. These resonance impedances are configured to match the output equivalent impedance of the matching transformer 321. That is, the tap 321C where the output equivalent impedance of the matching transformer 321 is reduced and the low frequency series resonance circuit 325 where the resonance impedance is low are connected between the output terminal S1 and the output terminals S1, S2 where the output equivalent impedance is high. Is connected to a high-frequency series resonance circuit 326 having a large resonance impedance.

  Since the maximum power can be supplied to the load when the output impedance of the supplied power matches the load impedance, the matching circuit unit 320 outputs based on the frequency characteristics of the impedance in the matching circuit unit 320 shown in the graph of FIG. The matching transformer 321 matches the impedance and the resonance impedance of the low frequency series resonance circuit 325 and the low frequency series resonance circuit 326 to efficiently supply the maximum power. Further, in the matching circuit unit 320, the circuit impedance at the resonance point of the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 is a pure resistance of AC power, and is proportional to the square root of the frequency. The impedance is larger than the resonance impedance of the low-frequency series resonance circuit 325 in proportion to the square root of {(high frequency) / (low frequency)}.

  The control circuit unit 330 synchronizes the low frequency and the high frequency that are serially resonated by the matching circuit unit 320, and controls the oscillation circuit unit 310 to switch and output the low frequency and the high frequency at high speed with a predetermined time ratio distribution. The control circuit unit 330 is connected to input means (not shown). This input means outputs a predetermined signal corresponding to an input operation corresponding to various settings such as heating power setting and power ratio setting by the operator. And the control circuit part 330 controls the oscillation circuit part 310 based on the setting input signal from an input means, and controls heating power and a power ratio. The control circuit unit 330 includes a forward conversion control circuit unit 331, a frequency power ratio control circuit unit 332 as a frequency power ratio control circuit, a low frequency synchronization circuit unit 333, and a high frequency synchronization circuit unit 334. .

  The forward conversion control circuit unit 331 is connected to the converter 311 of the oscillation circuit unit 310. The forward conversion control circuit unit 331 recognizes the output value of the DC power output from the converter 311, and converts the converter 311 into a state in which the output value becomes a predetermined output value based on the setting input signal related to the heating power output from the input unit. To control. Specifically, the voltage value on the output side of the converter 311 is detected, and the current value is detected by a current detection means 331A such as a DC current sensor provided on the output side of the converter 311 to set the input signal from the input means. The output value of DC power output by DC voltage and current feedback control is controlled by a thyristor or the like based on the above.

  The frequency power ratio control circuit unit 332 is connected to the inverter 312 of the oscillation circuit unit 310. The frequency power ratio control circuit unit 322 converts the low-frequency or high-frequency AC power output from the inverter 312 at a predetermined power ratio, that is, a duty ratio, based on a setting signal related to the power ratio corresponding to the input operation of the input means. For example, control is performed to switch in 1 ms. Specifically, based on a set input signal from the input means, a period for outputting each AC power within one cycle of low frequency and high frequency, for example, 100 ms, is set, and switching between low frequency and high frequency and power ratio are set. Control.

  Further, the frequency power ratio control circuit unit 332 outputs a signal related to the timing for switching between the low frequency and the high frequency, for example, a signal related to the duty ratio, to the forward conversion control circuit unit 331. The forward conversion control circuit unit 331 that has acquired the signal related to the timing controls the output value of the DC power output from the converter 311 to be a predetermined output value at low and high frequency timings.

  The low frequency synchronization circuit unit 333 is connected to the matching circuit unit 320 and to the frequency power ratio control circuit unit 332. Then, the low frequency synchronization circuit unit 333 detects the frequency current of the low frequency series resonance circuit 325 of the matching circuit unit 320 by the low frequency current detection means 333A such as a low frequency current sensor, and the frequency power ratio control circuit unit 332 To output a predetermined control signal. This control signal is such that the low frequency output frequency output from the oscillation circuit unit 310 by the frequency power ratio control circuit unit 332 becomes a series resonance frequency as indicated by F1 in the impedance frequency characteristic graph of FIG. , A signal for controlling the oscillation frequency of the inverter 312. Further, the low-frequency synchronization circuit unit 333 cannot detect the frequency current, and when shifting to the idle period in which the output of the control signal is stopped, the low-frequency synchronization circuit unit 333 separately stores frequency information that is synchronization information regarding the detected frequency current, such as a memory. When the operation is shifted to the operation period in which the frequency current is detected again and the control signal is output, the frequency information stored in the storage means is read and a control signal for frequency synchronization is output.

  The high frequency synchronization circuit unit 334 is connected to the matching circuit unit 320 and to the frequency power ratio control circuit unit 332. The high-frequency synchronization circuit unit 334 detects the frequency current of the high-frequency series resonance circuit 326 of the matching circuit unit 320 with high-frequency current detection means 334A such as a high-frequency current sensor, and performs predetermined control on the frequency power ratio control circuit unit 332. Output a signal. This control signal indicates the high frequency output frequency output from the oscillation circuit unit 310 in the frequency power ratio control circuit unit 332 as F2 in the impedance frequency characteristic graph of FIG. This is a signal for controlling the oscillation frequency of the inverter 312 so as to have such a series resonance frequency. Further, like the low frequency synchronization circuit unit 333, the high frequency synchronization circuit unit 334 cannot detect the frequency current, and stores frequency information regarding the frequency current to be detected when shifting to a pause period in which the output of the control signal is stopped. When the operation is shifted to the operation period in which the frequency current is detected again and the control signal is output, the frequency information stored in the storage means is read and a control signal for frequency synchronization is output.

  The frequency power ratio control circuit unit 332, the low frequency synchronization circuit unit 333, and the high frequency synchronization circuit unit 334 constitute the frequency power control circuit unit of the present invention. The frequency power ratio control circuit unit of the present invention is not limited to this configuration.

(Operation of induction heating device)
Next, the operation of the induction heating device 100 in the first embodiment will be described.

  First, the operator turns on the power and appropriately inputs the input means according to the object to be heated 201 to be heated by induction, whereby the heating power and the power ratio are input. Of the setting input signals output from the input means by this input operation, the setting input signal related to the heating power is input to the forward conversion control circuit unit 331 of the control circuit unit 330, and the setting input signal related to the power ratio is input to the control circuit unit 330. It is input to the frequency power ratio control circuit unit 332.

  Then, the converter 311 of the oscillation circuit unit 310 to which the commercial AC power source e is supplied controls the commercial AC power source e to DC power having a predetermined output by control based on the setting input signal related to the heating power by the forward conversion control circuit unit 331. Convert and output. That is, the forward conversion control circuit unit 331 detects the DC voltage on the output side of the converter 311, detects the current value with the current detection means 331 A, and controls the DC voltage and current feedback control with a thyristor etc. Adjust the output power to be output.

  The DC power output from the converter 311 is appropriately smoothed by the smoothing capacitor Cf and supplied to the inverter 312. The inverter 312 to which the DC power is supplied converts the DC power into a low frequency or high frequency AC power and performs switching output under control based on a setting input signal relating to the power ratio by the frequency power ratio control circuit unit 332. That is, the frequency power ratio control circuit unit 332 sets the low frequency and high frequency output ratios of the AC power output from the inverter 312 within 100 ms that is one cycle based on the set input signal, and the high frequency synchronization circuit 334 and the low frequency The low-frequency or high-frequency AC power is switched and output at high speed while synchronizing at a predetermined output frequency based on the control signal from the synchronization circuit 333.

  The AC power output from the inverter 312 is supplied to the matching circuit unit 320, and the matching circuit unit 320 is brought into a series resonance state at a low frequency or a high frequency by the induction heating coil 200 connected to the matching circuit unit 320. The heated object 201 is induction-heated. In the series resonance in the matching circuit unit 320, when the AC power output from the inverter 312 has a low frequency, the second capacitor C2 is much smaller than the first capacitor C1, for example, 1/10 to 1/20. Impedance. As a result, the second capacitor C2 constituting the high-frequency series resonance circuit 326 for the low frequency is opened, and almost no low-frequency AC power flows through the second capacitor C2. AC power is supplied to the first capacitor C <b> 1 side that constitutes 325. That is, in the matching circuit unit 320, the low-frequency series resonance circuit 325 enters a series resonance state by the low-frequency AC power, and the object to be heated 201 is induction-heated.

When the AC power output from the inverter 312 is a high frequency, the output equivalent impedance is equal to the output terminal S1 to which one lead wire of the secondary winding 321B is connected from the secondary winding 321B of the matching transformer 321 and the tap 321C. Since the reactor L is 4 to 5 times larger than the load coil equivalent inductance N ² L0, for example, the series of the reactor L and the first capacitor C1 constituting the low-frequency series resonance circuit 325 with respect to the high frequency is small. The circuit is opened, and almost no high-frequency AC power flows through the series circuit of the reactor L and the first capacitor C 1, and AC power is supplied to the second capacitor C 2 constituting the high-frequency series resonance circuit 326. . That is, in the matching circuit unit 320, the high-frequency series resonance circuit 326 enters a series resonance state by high-frequency AC power, and the object to be heated 201 is induction-heated.

In this way, the induction heating coil 200 that induction-heats the article to be heated 201 can generate AC power of both high frequency and low frequency through the matching circuit unit 320, and between high-frequency power and low-frequency power. It is connected to a voltage-type oscillation circuit unit 310 that can be switched at a high speed such as 1 ms, and the matching circuit unit 320 includes two series resonance circuits of a low-frequency first series resonance and a high-frequency second series resonance. It has a configuration with. The oscillation circuit unit 310 in the induction heating apparatus 100 is a voltage type that can operate independently at both low frequency and high frequency, and at the same time, the high frequency and low frequency have an arbitrary power ratio (duty ratio) and high and low. A function for switching between frequencies at a high speed of about 1 ms is provided. In order to realize this function, the control circuit unit 330 is provided with a high frequency synchronization circuit unit 334 and a low frequency synchronization circuit unit 333, which are their own frequency synchronization (PLL) circuits, and both PLL circuits. Operates alternately in a time proportional distribution set (time shelling), and the PLL circuit synchronizes with the frequency during each frequency operation period, and stores the frequency synchronization information immediately before the operation period enters the idle period (Hold), and then return to the operation period again, the previously stored synchronization information is restored, and frequency synchronization is resumed. Since the interval between the operation period and the pause period is set to a very short cycle (100 ms or less), the fluctuation of the inductive load resonance frequency due to a change in temperature is small during that period, and the time for synchronous tracking is short, and the speed can be increased .

(Operational effects of the first embodiment)
As described above, in the above-described embodiment, the control circuit unit 330 causes the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 of the matching circuit unit 320 to have a predetermined low frequency that resonates in series with the induction heating coil 200. In a state where the resonance frequency or a predetermined high-frequency resonance frequency is obtained, the oscillation circuit unit 310 outputs AC power having different frequencies of low frequency and high frequency. For this reason, the object to be heated 201 can be induction-heated by one induction heating coil 200 with two different frequencies in one oscillation circuit unit 310, the configuration is simplified, and manufacturability is improved and cost is easily reduced. Can be aimed at. In addition, it is not necessary to provide a pair of oscillation circuit units 310 for outputting low-frequency and high-frequency AC power, and a single oscillation circuit unit 310 supplies different low-frequency and high-frequency AC powers. Therefore, the device design is easy, the configuration can be simplified, the productivity can be improved, and the cost can be easily reduced.

  The matching circuit unit 320 is provided with a matching transformer 321 having a plurality of equivalent output equivalent impedances corresponding to the resonance impedances of the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 and supplied from the oscillation circuit unit 310. Inductive heating is performed by resonating in series with the AC power generated. For this reason, maximum electric power can be supplied to the induction heating coil 200 which is an induction load, and the to-be-heated object 201 can be induction-heated efficiently.

Further, as a configuration in which the output equivalent impedance equivalent to each resonance impedance is set in the matching transformer 321, the tap 321 </ b> C is provided in the secondary winding 321 </ b> B under the condition that the output equivalent impedance is substantially equivalent to each resonance impedance. For this reason, the structure which supplies the maximum electric power to the induction heating coil 200 and performs induction heating efficiently at different frequencies can be easily obtained. In particular, even in a configuration comprising a plurality of resonant circuits of the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326, the configuration Ru is supplied with maximum power respectively for different frequencies with a single transformer can be easily obtained.

  Further, based on the frequency current flowing through the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326, the resonance frequencies of the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 as shown by F1 or F2 in FIG. As described above, the frequency power ratio control circuit unit 332 of the control circuit unit 330 controls the inverter 312 to control the frequency of the AC power that is output. For this reason, frequency synchronization can be easily achieved, series resonance can be efficiently performed at low frequency or high frequency, and induction heating can be performed efficiently.

  Furthermore, as control of the frequency of the alternating current power to be output, the low-frequency current detection means 333A and the high-frequency current detection means 334A such as a sensor detect the frequency current flowing through the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326. Based on the detected frequency current, the low frequency synchronization circuit unit 333 and the high frequency synchronization circuit unit 334 of the control circuit unit 330 output and control the control signal for setting the control state of the inverter 312 in the output ratio control circuit unit 332. . For this reason, different induction heating states by efficient low frequency and high frequency can be easily obtained with a simple configuration.

  Then, the state of the induction heating coil 200 induction heating the object to be heated 201, for example, the duty ratio that is the power ratio corresponding to the heating condition set and input by the input operation according to the shape of the gear, etc. Switching between low frequency and high frequency is performed by the frequency power ratio control circuit unit 332. For this reason, it can induction-heat appropriately corresponding to the to-be-heated material 201, and can improve versatility. Since the power ratio can be changed by an input operation using the input means, the induction heating state can be easily changed with a simple configuration, and versatility can be easily improved.

  Furthermore, the forward conversion control circuit unit 331 uses the output value of the AC power output from the oscillation circuit unit 310 in the control circuit unit 330 as an output value corresponding to the heating condition set and input by an input operation based on, for example, the shape of a gear. Change control with. For this reason, it can induction-heat appropriately corresponding to the to-be-heated material 201, and can improve versatility. Since the output value can be changed by an input operation, the induction heating state can be easily changed with a simple configuration, and versatility can be easily improved. Since the output of the AC power output from the oscillation circuit unit 310 is controlled by changing the output value of the DC power output from the converter 311, the output of the AC power can be easily changed with a simple configuration.

  And since the voltage type | mold which converts into voltage square wave alternating current power is used as the inverter 312, the structure which can switch a low frequency and a high frequency easily at high speed, for example, 1 ms is obtained. For this reason, since the induction heating stop period when switching between the low frequency and the high frequency is as short as 1 ms, the fluctuation of the induction load frequency, that is, the resonance frequency of the induction load is hardly caused by the temperature change during the induction heating stop period. Absent. That is, since the impedance matches the resonance frequency, there is almost no fluctuation in the resonance frequency of the inductive load. Therefore, good induction heating can be performed, and the time for synchronous tracking can be shortened, so that induction heating can be performed efficiently.

Further, the inductance of the reactor L is set larger than the load coil equivalent inductance N ² L0, the impedance of the first capacitor C1 larger set much than the impedance of the second capacitor C2, the low-frequency series resonance circuit 325 By configuring the high-frequency series resonance circuit 326, the matching circuit unit 320 is configured to resonate at different low and high frequencies. For this reason, it is possible to configure a resonance circuit that resonates at different low and high frequencies even with one oscillation circuit unit 310 with a simple configuration.

[Second Embodiment]
(Configuration of induction heating device)
Next, a schematic configuration of the induction heating apparatus according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a circuit diagram showing a schematic configuration of the induction heating apparatus in the second embodiment.

  In FIG. 3, reference numeral 400 denotes an induction heating device. The induction heating device 400 includes an induction heating coil 200 similar to the induction heating device 100 in the first embodiment shown in FIGS. 1 and 2, and the induction heating coil 200. And a power supply device 500 that supplies power of predetermined different frequencies to cause induction heating. And the electric power supply apparatus 500 is provided with the oscillation circuit part 310 and the control circuit part 330 similar to the induction heating apparatus 100 in 1st Embodiment, and the matching circuit part 520. In addition, in the induction heating apparatus 400, about the structure same as the induction heating apparatus 100 shown in FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The matching circuit unit 520 has two different series resonance frequencies corresponding to the low frequency and the high frequency, and resonates in series with the induction heating coil 200 by the high frequency or low frequency power output from the oscillation circuit unit 310. Then, the object to be heated 201 is induction-heated. The matching circuit unit 520 includes a low-frequency matching transformer 521, a high-frequency matching transformer 522, a reactor L, a first capacitor C1, a second capacitor C2, and a current transformer 322. .

  The low frequency matching transformer 521 matches (matches) the impedance of the low frequency resonance frequency load with the output impedance of the DC power output from the oscillation circuit unit 310. In this low-frequency matching transformer 521, the primary winding 521A is connected to the oscillation circuit unit 310, and the converted AC power is input.

A reactor L, a first capacitor C1, and a primary winding 322A of a current transformer 322 are connected in series to the secondary winding 521B of the low-frequency matching transformer 521. A low-frequency series resonance circuit 325 configured by the reactor L, the first capacitor C1, and the load coil equivalent inductance N ² L0 and performing series resonance at a low frequency is configured. The output equivalent impedance of the secondary winding 521B of the low frequency matching transformer 521 is set so as to match the resonance impedance of the low frequency series resonance circuit 325.

  The high frequency matching transformer 522 matches (matches) the impedance of the high frequency resonant frequency load with the DC power output impedance output from the oscillation circuit unit 310. In this high-frequency matching transformer 522, the primary winding 522A is connected to the oscillation circuit unit 310 in parallel with the primary winding 521A of the low-frequency matching transformer 521, and converted AC power is input.

The second capacitor C2 and the primary winding 322A of the current transformer 322 are connected in series to the secondary winding 522B of the high-frequency matching transformer 522. A high-frequency series resonance circuit 326 configured by the second capacitor C2 and the load coil equivalent inductance N ² L0 and resonating in series at a high frequency is formed. The output equivalent impedance of the secondary winding 522B of the high frequency matching transformer 522 is set so as to coincide with the resonance impedance of the high frequency series resonance circuit 326.

(Operation of induction heating device)
Next, operation | movement of the induction heating apparatus 400 in the said 2nd Embodiment is demonstrated.

  When low-frequency AC power that is converted and output in the same manner as in the first embodiment is supplied to the matching circuit unit 520, the second capacitor C2 has a much smaller impedance than the first capacitor C1. For this reason, the second capacitor C2 constituting the high-frequency series resonance circuit 326 is opened for low frequencies. For this reason, the low frequency current does not flow through the high frequency matching transformer 522, the low frequency current flows through the low frequency matching transformer 521, and the low frequency AC power is supplied to the low frequency series resonance circuit 325. By supplying the low-frequency AC power, the low-frequency series resonance circuit 325 enters a series resonance state to inductively heat the article to be heated 201.

When high-frequency AC power is supplied from the oscillation circuit unit 310 to the matching circuit unit 520, the output equivalent impedance of the low-frequency matching transformer 521 is smaller than that of the high-frequency matching transformer 522, and the reactor L has a load coil equivalent inductance. Since it is 4 to 5 times larger than N ² L 0, for example, the series circuit of the reactor L and the first capacitor C 1 constituting the low-frequency series resonance circuit 325 with respect to the high frequency is opened. Therefore, no high frequency current flows through the low frequency matching transformer 521, high frequency current flows through the high frequency matching transformer 522, and high frequency AC power is supplied to the high frequency series resonance circuit 326. By supplying the high-frequency AC power, the high-frequency series resonance circuit 326 enters a series resonance state, and the object to be heated 201 is induction-heated.

(Operational effects of the second embodiment)
As described above, instead of the matching transformer 321 of the matching circuit unit 320 of the induction heating device 100 according to the first embodiment, the output corresponding to the resonance impedance of the low frequency series resonance circuit 325 and the high frequency series resonance circuit 326 is output. A low-frequency matching transformer 521 and a high-frequency matching transformer 522 having equivalent impedance are provided. For this reason, in the induction heating apparatus 400 in the second embodiment described above, in addition to the effects of the induction heating apparatus 100 in the first embodiment, no high-frequency current flows through the low-frequency matching transformer 521. Since no low-frequency current flows through the high-frequency matching transformer 522, each matching transformer 521, 522 can use an inexpensive product with a simple configuration, and can easily reduce the device cost.

[Third Embodiment]
(Configuration of induction heating device)
Next, a schematic configuration of an induction heating apparatus according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a circuit diagram showing a schematic configuration of the induction heating apparatus in the third embodiment.

  In FIG. 4, 600 is an induction heating device, and this induction heating device 600 includes an induction heating coil 200 similar to the induction heating device 100 in the first embodiment shown in FIGS. 1 and 2, and the induction heating coil 200. And an electric power supply device 700 that supplies electric power of predetermined different frequencies to cause induction heating. And the electric power supply apparatus 700 is provided with the oscillation circuit part 310 and the control circuit part 330 similar to the induction heating apparatus 100 in 1st Embodiment, and the matching circuit part 720. In addition, in the induction heating apparatus 600, about the structure same as the induction heating apparatus 100 shown in FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The matching circuit unit 720 has two different series resonance frequencies corresponding to the low frequency and the high frequency, and series resonates with the induction heating coil 200 by the high frequency or low frequency power output from the oscillation circuit unit 310. Then, the object to be heated 201 is induction-heated. The matching circuit unit 720 includes a reactor L, a first capacitor C1, a second capacitor C2, and a current transformer 322. That is, the induction heating device 600 shown in FIG. 4 has a configuration in which the matching transformer 321 of the induction heating device 100 shown in FIG. 1 is not provided.

Specifically, a reactor L, a first capacitor C 1, and a primary winding 322 A of a current transformer 322 are connected in series to the oscillation circuit unit 310. Furthermore, a second capacitor C2 is connected in parallel to the series circuit of the reactor L and the first capacitor C1. Then, the matching circuit 720, a reactor L, together with the low-frequency series resonance circuit 325 to the series resonance is constituted by the low-frequency is constituted by a first capacitor C1 and the load coil equivalent inductance N ² L0, a second capacitor A high-frequency series resonance circuit 326 configured by C2 and a load coil equivalent inductance N ² L0 and resonating in series at a high frequency is formed.

(Operation of induction heating device)
Next, the operation of the induction heating device 600 in the third embodiment will be described.

  When low-frequency AC power that is converted and output in the same manner as in the first embodiment is supplied to the matching circuit unit 720, the second capacitor C2 has a much smaller impedance than the first capacitor C1. For this reason, the second capacitor C2 constituting the high-frequency series resonance circuit 326 is opened for low frequencies. For this reason, the low frequency current flows through the reactor L of the low frequency series resonance circuit 325 and the series circuit side of the first capacitor C 1, and low frequency AC power is supplied to the low frequency series resonance circuit 325. By supplying the low-frequency AC power, the low-frequency series resonance circuit 325 enters a series resonance state to inductively heat the article to be heated 201.

In addition, when high-frequency AC power is supplied from the oscillation circuit unit 310 to the matching circuit unit 720, the reactor L is, for example, 4 to 5 times larger than the load coil equivalent inductance N ² L0. The series circuit of the reactor L and the first capacitor C1 constituting 325 is opened. Therefore, the high frequency current flows through the second capacitor C 2 of the high frequency series resonance circuit 326, and high frequency AC power is supplied to the high frequency series resonance circuit 326. By supplying the high-frequency AC power, the high-frequency series resonance circuit 326 enters a series resonance state, and the object to be heated 201 is induction-heated.

(Operational effect of the third embodiment)
As described above, the low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 are configured without providing the matching transformer 321 of the induction heating device 100 matching circuit unit 320 in the first embodiment. For this reason, a structure can be simplified more and a manufacturability improvement and cost reduction can be performed more easily.

  A second capacitor C2 is connected to the series circuit of the reactor L and the first capacitor C1 connected to the oscillation circuit unit 310, the reactor L of the series circuit of the primary winding 322A of the current transformer 322, and the first capacitor C1. The low-frequency series resonance circuit 325 and the high-frequency series resonance circuit 326 are connected in parallel. For this reason, the structure which carries out induction heating by two frequencies, the different low frequency and high frequency, with one oscillation circuit part 310 and one induction heating coil 200 is obtained easily.

  In particular, if it is used under the condition that the output power of the two frequencies to be heated does not have the same maximum power, it is effective because it has a simpler configuration than the first and second embodiments.

[Other Embodiments]
The present invention is not limited to the above-described embodiments, and various improvements and design changes can be made without departing from the scope of the present invention.

  For example, as described above, the object to be heated 201 is not limited to a configuration in which a heat treatment is performed on a gear having a plurality of irregularities on the surface or a member made of a composite material. May be. Furthermore, the induction load is not limited to the induction heating coil 200, and any configuration that causes an induction motor or the like to operate can be targeted.

  The alternating-current power to be supplied can be supplied in any frequency band. Further, the configuration for supplying the AC power is not limited to the configuration including the converter 311, the inverter 312, and the smoothing capacitor Cf described above.

  Further, the inverter 312 is not limited to a voltage type that converts to a voltage square wave.

  Moreover, it is good also as a structure which supplies electric power not only with two frequencies of a low frequency and a high frequency but with three or more different frequencies. Specifically, as shown in FIG. 5, for example, a plurality of taps are provided in the secondary winding 321B of the matching transformer 321 to connect a plurality of series resonance circuits in parallel, and a current value is detected in each series resonance circuit. Current detecting means is provided, and a plurality of synchronous circuit portions are provided corresponding to each series resonance circuit. As shown in FIG. 5, a plurality of series resonance circuits can be provided as appropriate in response to a state desired to be acted on by an inductive load, and AC power corresponding to each resonance frequency can be supplied and acted. Can be improved.

  Further, in the first embodiment shown in FIG. 1 and FIG. 2, for example, the frequency current of the low frequency series resonance circuit 325 of the matching circuit unit 320 detected by the low frequency current detection means 333A such as a low frequency current sensor, and For example, the frequency current of the high-frequency series resonance circuit 326 of the matching circuit unit 320 detected by the high-frequency current detection means 334A such as a high-frequency current sensor is used as the primary winding 322A of the current transformer 322, the first capacitor C1, and the second capacitor. However, the detection may be performed between the primary winding 321A of the matching transformer 321 and the inverter 312 as shown in FIG. That is, a switching means 800 such as a switch is connected between the low frequency current detection means 333A and the high frequency current detection means 334A and the low frequency synchronization circuit section 333 and the high frequency synchronization circuit section 334, and the switching operation by the switching means 800 is performed. As in the first embodiment, the low frequency synchronization circuit unit 333 and the high frequency synchronization circuit unit 334 may perform synchronization processing.

  In addition, the specific structure and procedure for carrying out the present invention may be changed to other configurations as long as the object of the present invention can be achieved.

It is a circuit diagram which shows schematic structure of the induction heating apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows the frequency characteristic of the impedance in the matching circuit part of the said 1st Embodiment. It is a circuit diagram which shows schematic structure of the induction heating apparatus which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows schematic structure of the induction heating apparatus which concerns on the 3rd Embodiment of this invention. It is a circuit diagram which shows schematic structure of the induction heating apparatus which concerns on other embodiment of this invention. It is a circuit diagram which shows schematic structure of the induction heating apparatus which concerns on other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,400,600 Induction heating apparatus 200 Induction heating coil as induction load 201 To-be-heated object 300,500,700 Electric power supply apparatus 310 Oscillation circuit part 311 Converter as a forward conversion circuit part 312 Inverter 320 as an inverse conversion circuit part, 520, 720 Matching circuit section 321 Matching transformer 321A, 521A Primary winding 321B, 521B Secondary winding 321C Tap 330 Control circuit section 331 Forward conversion control circuit section 332 as output control circuit section Frequency power ratio Frequency power ratio control circuit section 521 as a control circuit Low frequency matching transformer 521 which is a transformer High frequency matching transformer which is a 522 transformer

Claims (14)

A power supply device that operates by supplying power of different frequencies to an inductive load,
An oscillation circuit unit that outputs AC power of different frequencies;
A matching circuit unit that configures a plurality of resonant circuits with the inductive load corresponding to the different frequencies,
A control circuit unit that controls a state in which the frequency of the alternating current power supplied from the oscillation circuit unit to any one of the resonance circuits of the matching circuit unit is supplied at a predetermined resonance frequency ,
The matching circuit unit includes a transformer that converts a plurality of load resonance impedances into substantially the same oscillator output impedance. The power supply device according to claim 1 ,
The transformer includes a primary winding connected to the oscillation circuit unit and supplied with AC power, and a secondary winding having a tap for converting a plurality of different load resonance impedances to substantially the same oscillator output impedance. A power supply device characterized by comprising. The power supply device according to claim 1 ,
A plurality of the transformers are provided for each resonance circuit that converts load resonance impedance into oscillator output impedance. The power supply device according to any one of claims 1 to 3 ,
The control circuit unit includes a frequency power ratio control circuit unit that switches a frequency of AC power output from the oscillation circuit unit in accordance with a state in which the inductive load is applied. The power supply device according to claim 4 ,
The frequency power ratio control circuit unit sets a frequency of AC power to be output from the oscillation circuit unit based on a setting input signal related to a state in which the inductive load is applied which is set by an input operation of an input unit. Power supply device. The power supply device according to claim 4 or 5 , wherein
It said frequency power ratio control circuit section includes a low frequency synchronous to control the oscillation frequency of the oscillation circuit to a state where the low frequency of the output frequency becomes a predetermined series resonance frequency in the frequency characteristic of the impedance output from the oscillator circuit a circuit portion, and a high-frequency synchronizing circuit the output frequency of the high frequency to control the oscillation frequency of the oscillation circuit to a state where a predetermined series resonance frequency in the frequency characteristic of the predetermined impedance to be output from the oscillator circuit unit, low-frequency And a frequency power control circuit for switching between high frequencies. The power supply device according to any one of claims 1 to 3 ,
The control circuit section includes a frequency power ratio control circuit section that switches and controls the frequency of AC power output from the oscillation circuit section in units of cycles. The power supply device according to claim 7 ,
The frequency power ratio control circuit unit is capable of changing the time distribution of each frequency to be switched based on a setting input signal related to a state in which the inductive load set by an input operation of an input unit is applied. Power supply device. The power supply device according to any one of claims 1 to 8 ,
The control circuit unit controls a frequency of AC power output from the oscillation circuit unit based on a frequency current flowing in the resonance circuit. The power supply device according to claim 9 ,
The control circuit unit is
A synchronous control circuit unit provided corresponding to each frequency of AC power supplied from the oscillation circuit unit;
Storage means for storing period information relating to the predetermined frequency when shifting to an idle period in which AC power is not supplied to the predetermined frequency from the oscillation circuit unit;
The synchronization control circuit unit performs synchronization control on the basis of synchronization information stored in the storage means when shifting to an operation period in which AC power is supplied to the predetermined frequency. . The power supply device according to any one of claims 1 to 1 0,
The power supply apparatus according to claim 1, wherein the control circuit unit includes an output control circuit unit that changes an output of AC power output from the oscillation circuit unit. The power supply device according to claim 1 1,
The oscillation circuit unit includes a forward conversion circuit unit that converts AC power into predetermined DC power, and an inverse conversion circuit unit that converts DC power converted by the forward conversion circuit unit into predetermined AC power,
The output control circuit unit performs feedback control of an output value of DC power output from the forward conversion circuit unit. The power supply device according to any one of claims 1 to 1 2,
The oscillation circuit unit includes an inverse conversion circuit unit that converts DC power into voltage square wave AC power. A power supply device according to any one of claims 1 to 1 3,
An induction heating coil that induction-heats an object to be heated with electric power of different frequencies supplied from the power supply device;
An induction heating apparatus comprising:

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