JP2021072768A - Power supply device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high power factor characteristic by extending a period in which an input current flows with respect to a cycle of an AC voltage. A transformer 206 has a primary winding 206a and a primary winding 206b, and is connected to a diode bridge 203 that full-wave rectifies an AC voltage, one end of which is connected to the primary winding 206a, and the other end. An electrolytic capacitor 207 connected to the primary winding 206b via a FET 208, an input inductor 204 having one end connected to the output end of the diode bridge 203, and an anode terminal connected to the other end of the input inductor 204 to form a cathode terminal. The primary winding 206a includes a diode 205 connected to a connection point between the primary winding 206a and the primary winding 206b, and the primary winding 206a has a larger number of turns than the primary winding 206b. [Selection diagram] Fig. 2

Description

The present invention relates to a power supply device and an image forming apparatus, and more particularly to a switching power supply and an image forming apparatus having an improved power factor.

Since a general switching power supply has a smoothing capacitor at the first stage of the input, the input current flows only when the input voltage exceeds the charging voltage of the smoothing capacitor. In the case of this configuration, the power factor tends to be low and the harmonic current tends to be high because the time for which the current flows is short with respect to the cycle of the AC voltage of the AC power supply. In order to solve this problem, the input filter is equipped with a coil for improving the power factor, or in order to further improve the power factor, a power factor improving circuit is installed so that the waveform of the input current becomes almost sinusoidal. Measures were taken by configuring it in the previous stage. Among these, as a measure to improve the power factor with the coil of the input filter, the power factor can be increased only to about 70 to 80%. On the other hand, the switching power supply equipped with the power factor improving circuit was able to obtain a power factor close to 100%. However, since the power factor improving circuit itself functions as one converter, the circuit is composed of two converters together with the switching power supply in the subsequent stage. Therefore, even if the power factor is good, the efficiency is low, and the cost and the area of the printed circuit board tend to be large. In order to solve these problems, a switching power supply that combines high power factor and high efficiency with one converter has been devised. For example, Patent Document 1 discloses a technique for bringing the waveform of an input current closer to a sinusoidal shape.

Japanese Patent No. 3949442

With the conventional technique, a high power factor may not be obtained depending on the ratio (number of turns ratio) between the primary winding and the auxiliary winding. Further, conventionally, the ratio of the primary winding to the auxiliary winding has not been clearly explained. Therefore, it is required to clarify the turns ratio between the primary winding and the auxiliary winding and to widen the conduction angle of the input current.

The present invention has been made under such a situation, and it is an object of the present invention to be able to extend the period in which an input current flows with respect to the cycle of an AC voltage and to obtain a high power factor characteristic.

In order to solve the above-mentioned problems, the present invention includes the following configurations.

(1) A transformer having a first primary winding, a second primary winding, and a secondary winding, a switching element connected in series with the primary winding, and all input AC voltages. A full-wave rectifier circuit for wave rectification, a smoothing circuit having one end connected to the first primary winding and the other end connected to the second primary winding via the switching element, and the whole. A circuit connected to the output end of a wave rectifier circuit, in which an inductor and a rectifier element are connected in series, is provided, and the first primary winding is wound more than the second primary winding. A power supply that is characterized by a large number.

(2) An image forming unit for forming a toner image on the recording material and a power supply device for supplying electric power to the image forming unit are provided, and the power supply device includes a first primary winding and a first power supply device. A transformer having a primary winding and a secondary winding of 2, a switching element connected in series with the primary winding, a full-wave rectifier circuit for full-wave rectifying the input AC voltage, and one end described above. A smoothing circuit connected to the first primary winding and the other end connected to the second primary winding via the switching element is connected to the output end of the full-wave rectifier circuit. An image forming apparatus comprising a circuit in which an inductor and a rectifying element are connected in series, wherein the first primary winding has a larger number of turns than the second primary winding.

(3) In an image forming apparatus to which an optional device for processing an image-formed recording material is connected, power is supplied to the image forming portion for forming a toner image on the recording material and the image forming portion. The second power supply device includes a first power supply device for supplying electric power to the optional device, and the second power supply device has a first primary winding and a second primary power supply. A transformer having a winding and a secondary winding, a switching element connected in series with the primary winding, a full-wave rectifier circuit for full-wave rectifying the input AC voltage, and one end of the first 1 A smoothing circuit connected to the next winding and the other end connected to the second primary winding via the switching element, and an inductor and a rectifier element connected to the output end of the full-wave rectifier circuit. An image forming apparatus comprising a circuit in which and are connected in series, wherein the first primary winding has a larger number of turns than the second primary winding.

According to the present invention, the period during which the input current flows can be lengthened with respect to the cycle of the AC voltage, and high power factor characteristics can be obtained.

Schematic of the Laser Beam Printer of Example 1 Circuit diagram of the switching power supply of the first embodiment A graph showing the current waveform and the voltage waveform of the first embodiment, and a graph showing the current waveform of the laser beam printer. Circuit diagram of the switching power supply of the second embodiment Configuration diagram of application example 2 to a printer of the first embodiment The figure which shows the waveform of the combined current in the application example 2 to the printer of Example 1.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings by way of examples.

[Image forming device]
In the first embodiment, a case where the power supply device of the present invention is applied to the image forming device will be described with reference to FIGS. 1 to 3. FIG. 1 shows a schematic configuration of a laser beam printer as an example of an image forming apparatus. The laser beam printer (hereinafter referred to as a printer) 100 includes a photosensitive drum 101 as an image carrier, a charging unit 102 as a charging means, and a developing unit 103 as a developing means. An electrostatic latent image is formed on the photosensitive drum 101. The charging unit 102 uniformly charges the photosensitive drum 101. The developing unit 103 develops the electrostatic latent image formed on the photosensitive drum 101 with toner. Then, the toner image developed on the photosensitive drum 101 is transferred from the cassette 104 to the sheet P as a recording material supplied by the roller 110 or the like as a transport means by the transfer unit 105 which is a transfer means. The toner image transferred to the sheet P is fixed by the fixing device 106, which is a fixing means, and the sheet P is discharged to the tray 107. The photosensitive drum 101, the charging unit 102, the developing unit 103, and the transfer unit 105 are image forming units. Further, the printer 100 includes a low-voltage power supply 108 which is a power supply device, and the low-voltage power supply 108 is a control unit (not shown) that controls an image forming operation or a sheet P conveying operation by a driving unit such as a motor or an image forming unit. ) Is supplied with power.

[Power supply]
FIG. 2 is a circuit diagram of the switching power supply 200 of the first embodiment as the low voltage power supply 108. The AC plug 201 is connected to an outlet to supply an AC voltage to the switching power supply 200. The AC voltage supplied to the switching power supply 200 is full-wave rectified by the diode bridge 203, which is a full-wave rectifier circuit, via the filter circuit 202. On the other hand, when the external load to which the power of the switching power supply 200 is supplied is substantially constant and the output voltage Vo is stable, the charging voltage charged to the electrolytic capacitor 207, which is a smoothing means, becomes a substantially constant voltage.

The switching power supply 200 includes an input inductor 204 (inductor), a diode 205 as a rectifying element, a transformer 206, and an electrolytic capacitor 207. The transformer 206 has primary windings 206a and 206b and secondary windings 206c. In the transformer 206, the primary windings 206a and 206b and the secondary winding 206c have different polarities. One end of the input inductor 204 is connected to the output end of the diode bridge 203, and the other end is connected to the anode terminal of the diode 205. The cathode terminal of the diode 205 is connected to the connection point between the primary winding 206a and the primary winding 206b. That is, the output voltage of the diode bridge 203 is supplied to the connection point between the primary winding 206a and the primary winding 206b via the input inductor 204 and the diode 205.

One end of the primary winding 206a of the transformer 206 is connected to the + side of the electrolytic capacitor 207, and the other end is connected to one end of the primary winding 206b. The other end of the primary winding 206b is connected to the drain terminal of a field effect transistor (hereinafter referred to as FET) 208. The FET 208, which is a switching element, has a source terminal connected to the − side of the electrolytic capacitor 207, and a gate terminal connected to a control IC (not shown) which is a control unit. That is, the FET 208 is connected in series to the primary winding 206b of the transformer. When a gate voltage is supplied to the gate terminal of the FET 208 from a control IC (not shown) and the FET 208 becomes conductive, the charging voltage of the electrolytic capacitor 207 is divided by the primary winding 206a and the primary winding 206b of the transformer 206. Will be done. When the output voltage of the diode bridge 203 is higher than the divided voltage, the input current flows through the input inductor 204 and the diode 205.

Here, by increasing the number of turns of the primary winding 206a to be larger than the number of turns of the primary winding 206b, the voltage value divided by the primary winding 206a and the primary winding 206b becomes low. The input current will flow from a voltage at which the output voltage of the diode bridge 203 is lower. Further, while the voltage values divided by the primary windings 206a and 206b are substantially constant, the output voltage of the diode bridge 203 changes with time in a sinusoidal shape, so that the waveform of the input current also becomes substantially sinusoidal. It will change. Therefore, in the switching power supply 200, it is possible to obtain a power supply characteristic having a high power factor.

Further, the voltage generated between the secondary windings 206c changes depending on the conditions such as the turns ratio between the primary windings 206a and the primary windings 206b and the secondary windings 206c, the input voltage, and the like. The control IC (not shown) that controls the switching power supply 200 controls the switching operation by changing the on width and duty of the FET 208 based on the feedback signal on the secondary side, and controls the voltage generated in the secondary winding 206c. To do. Then, the voltage generated in the secondary winding 206c is rectified / smoothed by the rectifying diode 209 and the secondary smoothing capacitor 210, so that the output voltage Vo is stabilized to a predetermined voltage. V, Vc, and Vin will be described later.

[Transition of each waveform]
FIG. 3A shows each waveform when the input current is Iin and the output voltage of the diode bridge 203 is Vin. The input current Iin means a current input from the diode bridge 203 to the connection point between the primary winding 206a and the primary winding 206b via the input inductor 204 and the diode 205. The output voltage Vin means a voltage input from the diode bridge 203 to the connection point between the primary winding 206a and the primary winding 206b via the input inductor 204 and the diode 205. The input current Iin is shown in FIGS. 3A and 3A, and the output voltage Vin is shown in FIG. 3B. In each case, the horizontal axis represents time t. Further, in FIGS. 3A and 3B, the electrolytic capacitor 207 shows the primary winding 206a, which is the first primary winding of the transformer 206, and the primary winding 206b, which is the second primary winding. The value obtained by dividing the voltage of (voltage division value) is indicated by a broken line.

As shown in FIG. 3A, the voltage of the electrolytic capacitor 207 is divided between the primary winding 206a and the primary winding 206b, and the voltage exceeds the voltage when the output voltage Vin of the diode bridge 203 exceeds (time t1). (T3, t5 ...)), The input current Iin flows. The input current Iin flows until the output voltage Vin becomes equal to or less than the divided value (time t2 (t4, t6 ...)). Paradoxically, the input current Iin does not flow (Iin = 0) until the output voltage Vin reaches the divided value (for example, from time t2 to time t3). Therefore, the lower the partial pressure value, the earlier the timing at which the input current Iin starts to flow, the later the timing at which the input current Iin stops flowing, and the phase angle at which the input current Iin flows, that is, the conduction angle increases. And it becomes possible to improve the power factor.

[Transformer design method]
Next, the design method of the transformer 206 for determining the power factor characteristics of the switching power supply 200 will be described in detail. The basic configuration of the circuit of the switching power supply 200 of FIG. 2 is a flyback converter. Therefore, the guideline of the input power with respect to the output power can be calculated by using the following equation (1).
Pin = V2 × ton2 × f / (2 × L) ・ ・ ・ Equation (1)

Here, Pin is the input power, ton is the on-time of the FET 208, f is the drive frequency of the switching operation of the FET 208, and L is the inductance of the primary winding 206b. The point to be noted here is that the voltage V described in the equation (1) is not the output voltage Vin but the midpoint voltage of the primary winding 206a and the primary winding 206b. The midpoint voltage V is a voltage obtained by dividing the voltage Vc of the electrolytic capacitor 207 by the primary winding 206a and the primary winding 206b. Assuming that the turns ratio (hereinafter, also referred to as a ratio) between the number of turns of the primary winding 206a and the number of turns of the primary winding 206b is N, the equation (1) becomes the following equation (2).
Pin = (Vc / (N + 1)) 2 × ton2 × f / (2 × L) ... Equation (2)

The relationship between the input power Pin and the output power Po is expressed by the following equation (3).
Pin = Po / η ・ ・ ・ Equation (3)
Here, η is the conversion efficiency from the primary side to the secondary side. Therefore, the equation (2) can be converted as shown in the following equation (4).
Po = η × (Vc / (N + 1)) 2 × ton2 × f / (2 × L) ・ ・ ・ Equation (4)
The inductance L of the primary winding 206b is calculated so as to satisfy the equation (4).

Further, the peak value of the current flowing through the primary winding 206b is determined by I = V × ton / L, and V here also sets the voltage Vc of the electrolytic capacitor 207 between the primary winding 206a and the primary winding 206b. It becomes a divided voltage. That is, the following equation (5) is obtained.
I = Vc / (N + 1) × ton / L ... Equation (5)
Further, when the FET 208 is turned on, the current flowing through the primary winding 206b is the current flowing through the input inductor 204. This current can be calculated by dividing the difference between the output voltage Vin of the diode bridge 203 and the midpoint voltage V by the inductance Lin of the input inductor 204 and multiplying it by the on-time ton. Assuming that the current flowing through the input inductor 204 is Iin, it is represented by the following equation (6).
Iin = (Vin-Vc × N206b / (N206a + N206b)) / Lin × ton ・ ・ ・ Equation (6)
Will be. Here, N206a is the number of turns of the primary winding 206a, and N206b is the number of turns of the primary winding 206b.

Next, the period during which the current on the primary side flows with respect to the cycle of the AC power supply, that is, the conduction angle, can be widened by winding a large number of turns of the primary winding 206a with respect to the primary winding 206b. .. Since the purpose of this circuit is to obtain a high power factor, it is desirable that the conduction angle is wide.

Here, we consider how large the turns ratio N can be. The total number of primary windings 206b and primary windings 206a (N206a + N206b) is the output voltage Vo and the input voltage, and here, the minimum value of the output voltage Vin of the diode bridge 203 can be used to calculate the guideline of the turns ratio N. it can. For example, when the output voltage Vin of the diode bridge 203 is AC 85V and the output voltage Vo is 24V, the turns ratio of the primary windings 206a and 206b to the secondary winding 206c is about 5. Assuming that the number of turns of the secondary winding 206c is 3 turns, the total number of turns of the primary windings 206a and 206b is 15 turns (= 3 turns x 5).

As a premise, consider the case where each condition is set as follows.
η: 0.85, Vc: 120V, ton: 7.5μs, f = 65kHz, Po: 100W
Here, the case where N = 2 to 4 is actually calculated and examined.

When N = 2, since the number of turns ratio N is 2 and the total number of primary windings 206a and 206b is 15 turns, primary winding 206b = 5 and primary winding 206a = 10. When the inductance L of the primary winding 206b is obtained from the equation (4), it becomes as in the equation (7).
L = 0.85 × (120 / (2 + 1)) 2 × 7.5μ 2 × 65000/2/100 = 24.9μH ≈ 25μH ... Equation (7)
Next, when the inductance L of the primary winding 206b obtained by the equation (7) is substituted into the equation (5) and the peak value of the current flowing through the primary winding 206b is obtained, it is as shown in the equation (8). Become.
I = 120 / (2 + 1) × 7.5μ / 25μ = 12A ... Equation (8)

Further, when the input current Iin flowing through the input inductor 204 is obtained using the equation (6), the equation (9) is obtained.
Iin = (120-120 × 5/15) / 40μ × 7.5μ = 15A ・ ・ ・ Equation (9)
Here, the inductance Lin of the input inductor 204 is set to 40 μH. From the equations (8) and (9), since Iin> I, it can be determined that the number of turns (N206b = 5) of the primary winding 206b is a feasible setting constant.

-In the case of N = 3 Similarly, in the case of N = 3, since the number of turns needs to be an integer and the total number is 15 turns, the number of turns of the primary winding 206b is N206b = 4, and the number of turns of the primary winding 206a is The number of turns N206a = 11, and the number of turns ratio N is N = 11/4 instead of the target 3. By substituting the value of the number of turns and other values into each equation in the same manner as when N = 2, I = 15A and Iin = 16.5A are obtained. In this case, since Iin> I, it can be determined that the number of turns (N206b = 4) of the primary winding 206b is a feasible setting constant.

When N = 4 When N = 4, the number of turns of the primary winding 206b is N206b = 3, and the number of turns of the primary winding 206a is N206a = 12. In this case, the value of the number of turns and other values are substituted into each equation in the same manner as when N = 2, and I = 20A and Iin = 18A are obtained. In this case, since Iin <I, the current I flowing through the primary winding 206b becomes larger than the input current Iin flowing through the input inductor 204. Therefore, it can be determined that the realization is impossible with these setting constants.

Here, from the equation (6), if the inductance Lin of the input inductor 204 is further lowered, the current Iin flowing through the input inductor 204 can be further increased. Therefore, the idea of making the current I or more flowing through the primary winding 206b or more is adopted. You can also do it. However, if the inductance Lin of the input inductor 204 is lowered and the input current Iin that flows is increased, the voltage of the electrolytic capacitor 207 rises due to the charging current when the FET 208 is off, and it becomes necessary to use an element having a high rated voltage for the FET 208. .. Further, when the peak current becomes large, the surge voltage of the FET 208 rises, and a higher rated current of the FET 208 is required. Furthermore, under these conditions, the peak current has reached around 20A in the first place, and considering the rating and loss of the semiconductor used, the loss of the winding wound around the transformer 206, etc., the limit of the practically usable current is reached. It is considered to be close. From the above consideration, it is considered that the maximum number of turns ratio N is 4 at the highest.

[Application example 1 to printer]
Next, an example in which the low-voltage power supply 108 having the increased conduction angle in this way is applied to the printer 100 will be described with reference to FIG. 3 (B). FIG. 3B shows a waveform of a combined current obtained by combining the current of the fuser 106 and the current of the low-voltage power supply 108. FIGS. 3B and 3A show waveforms of the combined current when the low voltage power supply 108 is a capacitor input type which is a general power supply system. Further, FIGS. 3B and 3B show waveforms of the combined current when the low-voltage power supply 108 is the power supply system of the first embodiment. In both cases, the vertical axis represents the current I and the horizontal axis represents the time t. Further, the current waveform of the fuser 106 is a waveform of fixing control called phase control, and is a current waveform in which no current flows for a predetermined period.

In FIGS. 3B and 3A, the conduction angle is narrowed because the period until the time t11'when no current flows is long. In contrast to FIGS. 3 (B) and 3 (a), in FIGS. 3 (B) and 3 (b), the current starts to flow from the time t10 before the time t11 due to the effect of the first embodiment, so that the period during which the current is flowing becomes longer. It can be confirmed that the length is increased and the conduction angle is widened. Further, the peak portion of the current has a shape close to a sinusoidal waveform, with the Ip of FIGS. 3 (B) and 3 (b) suppressed (Ip <Ip') with respect to the Ip'of FIGS. 3 (B) and 3 (a). .. Therefore, the power factor can be improved in the waveforms of FIGS. 3 (B) and 3 (b).

As described above, as the number of turns of the primary winding 206a is larger than that of the primary winding 206b, the conduction angle of the input current with respect to the cycle of the AC voltage input from the AC power supply can be widened. Further, as the number of turns of the primary winding 206a is larger than the number of turns of the primary winding 206b, the current flowing through the input inductor 204 and the diode 205 increases. Further, the lower the inductance of the input inductor 204, the larger the current flowing through the input inductor 204 and the diode 205. Further, under the above-mentioned premise, the turns ratio N of the primary winding 206a to the primary winding 206b can be expanded up to 4. That is, the number of turns of the primary winding 206a is four times or less the number of turns of the primary winding 206b. Further, when the low voltage power supply 108 of the first embodiment is applied to the printer 100, the power factor can be improved.

[Application example 2 to printer]
As shown in FIG. 5, the printer has a configuration in which a device to which the output option device 802 is connected is connected to the printer main body 800. In such a configuration, it has a low-voltage power supply 801 for supplying power to the printer main body 800 and a low-voltage power supply 803 for supplying power to the output option device 802. Since the basic configuration of the printer main body 800 is the same as that of the printer 100 of FIG. 1, the description thereof will be omitted. Since the low voltage power supply 803 has the same configuration as that of FIG. 2, the description thereof will be omitted. The output option device 802 is an option device having a sort function capable of sorting and outputting a sheet as a recording material as shown in FIG. FIG. 5 shows an output option device having three discharge bins 802a, 802b, 802c. The output option device having a sort function is not limited to the output option device having a function of stapling a plurality of sheets on which an image is formed, and the like may be an option processing device for processing sheets. In this configuration, the low voltage power supply 803 corresponds to the low voltage power supply shown in FIG. Further, the low voltage power supply 801 is a capacitor input type power supply which is a general power supply system.

The waveform of the combined current in such a configuration will be described. FIG. 6A shows a waveform of a combined current obtained by combining the current of the fuser (106 of FIG. 1) with the currents of the low-voltage power supply 801 and the low-voltage power supply 803. The vertical axis of the figure shows the current I, and the horizontal axis shows the time t. In FIG. 6A, (1) the current waveform to the fuser, (2) the current waveform of the low voltage power supply 801 and (3) the current waveform of the low voltage power supply 803, (4) (1) to (3). The waveform of the combined current is shown. On the other hand, FIG. 6B shows a combined current waveform when a general capacitor input type power supply is used as the low voltage power supply 803 instead of the low voltage power supply of this embodiment. In FIG. 6B, (1) the current waveform to the fuser, (2) the current waveform of the low voltage power supply 801 and (3) the current waveform of the constant voltage power supply of the capacitor input type, (4) (1) to ( The waveform of the combined current of 3) is shown.

Comparing FIG. 6 (a) and FIG. 6 (b), regarding the waveform of the combined current in FIG. 6 (a), since the current flows in the period 601a even in the period 601b in which the current does not flow in FIG. 6 (b), As a whole, the power factor is improved as compared with FIG. 6 (b). Further, since the peak value 602a of the current in FIG. 6A is smaller than the peak value 602b in FIG. 6B, the power factor is improved as compared with FIG. 6B.
As a result, even in a device in which the printer main body 800 and the output option device 802 are connected, the power factor when power is supplied from the power source can be improved by applying the power supply of this embodiment to the output option device 802. ..

As described above, according to the first embodiment, the period in which the input current flows can be lengthened with respect to the cycle of the AC voltage, and a high power factor characteristic can be obtained.

[Power supply]
In the first embodiment, the case where the primary winding 206a is composed of one winding has been described. In the second embodiment, the primary winding 206a is divided into a plurality of windings, for example, two windings. The description of the second embodiment will be described with reference to the circuit diagram of FIG. In FIG. 4, the primary winding corresponding to the primary winding 206a in FIG. 2 is divided into a primary winding 501a and a primary winding 501b, and the other components have the same configuration. It becomes an element and has the same code. The description of those with the same reference numerals will be omitted.

Even if the primary winding 206a is divided into the primary winding 501a and the primary winding 501b, the voltage dividing value V of the electrolytic capacitor 207 becomes the upper (・ side) voltage of the primary winding 206b, and the voltage dividing value. Is determined by the total number of the primary windings 501a, 501b and 206b and the turns ratio of the primary windings 206b. When the output voltage Vin of the diode bridge 203 exceeds this voltage dividing value, the input current Iin flows. Therefore, by increasing the total number of turns of the primary winding 501a and the primary winding 501b with respect to the number of turns of the primary winding 206b, the partial pressure value becomes low and the conduction angle of the input current Iin becomes wider. can do. In this way, when the number of turns of the primary windings 501a and 501b corresponding to the primary winding 206a is set to be larger, the windings are divided into two windings such as the primary winding 501a and the primary winding 501b. However, the same effect can be obtained.

As described above, even if the primary winding 206b is divided into two winding configurations of the primary winding 501a and the primary winding 501b, the total number of turns of the primary winding 501a and the primary winding 501b Is more than the primary winding 206b. Thereby, the conduction angle can be widened. In the description of the second embodiment, the case where the primary winding 206a is divided into two has been described, but the same effect can be obtained even if the primary winding 206a is further divided into a plurality of windings.

As described above, according to the second embodiment, the period in which the input current flows can be lengthened with respect to the cycle of the AC voltage, and a high power factor characteristic can be obtained.

In each of the circuits of Examples 1 and 2 (FIGS. 2 and 4), the input inductor 204 is connected to the diode bridge 203 side at the connection position of the circuit in which the input inductor 204 and the diode 205 are connected in series. Explained in. However, the same effect can be obtained not only in this configuration but also in a configuration in which the diode 205 is connected to the diode bridge 203 side.
The configuration in which the diode 205 is connected to the diode bridge 203 side is specifically the following connection configuration.
The anode terminal of the rectifying element is connected to the output end of the diode bridge 203, and the cathode terminal is connected to one end of the input inductor 204. The other end of the input inductor 204 is connected to the connection point between the primary winding 206a and the primary winding 206b.

203 Diode bridge 204 Input inductor 205 Diode 206 Transformer 206a Primary winding 206b Primary winding 206c Secondary winding 207 Electrolytic capacitor

Claims (13)

A transformer having a first primary winding and a second primary winding and a secondary winding,
A switching element connected in series with the primary winding and
A full-wave rectifier circuit that full-wave rectifies the input AC voltage,
A smoothing circuit having one end connected to the first primary winding and the other end connected to the second primary winding via the switching element.
A circuit connected to the output end of the full-wave rectifier circuit, in which an inductor and a rectifier element are connected in series, is provided.
The first primary winding is a power supply device having a larger number of turns than the second primary winding. The first aspect of claim 1, wherein the larger the number of turns of the first primary winding than the number of turns of the second primary winding, the larger the current flowing through the inductor and the rectifying element. Power supply. The power supply device according to claim 1 or 2, wherein the lower the inductance of the inductor, the larger the current flowing through the inductor and the rectifying element. The power supply device according to claim 3, wherein the number of turns of the first primary winding is three times or less the number of turns of the second primary winding. The power supply according to any one of claims 1 to 4, wherein the first primary winding and the second primary winding have a polarity different from that of the secondary winding. apparatus. The power supply device according to any one of claims 1 to 5, wherein the first primary winding has a plurality of windings connected in series. One end of the inductor is connected to the output end of the full-wave rectifier circuit, the anode terminal of the rectifier element is connected to the other end of the inductor, and the cathode terminal is the first primary winding and the second one. The power supply device according to any one of claims 1 to 6, wherein the power supply device is connected to a connection point with the next winding. An image forming part for forming a toner image on the recording material,
A power supply device for supplying electric power to the image forming unit is provided.
The power supply device
A transformer having a first primary winding and a second primary winding and a secondary winding,
A switching element connected in series with the primary winding and
A full-wave rectifier circuit that full-wave rectifies the input AC voltage,
A smoothing circuit having one end connected to the first primary winding and the other end connected to the second primary winding via the switching element.
A circuit connected to the output end of the full-wave rectifier circuit, in which an inductor and a rectifier element are connected in series, is provided.
The image forming apparatus, wherein the first primary winding has a larger number of turns than the second primary winding. 8. The eighth aspect of the present invention, wherein the larger the number of turns of the first primary winding than the number of turns of the second primary winding, the larger the current flowing through the inductor and the rectifying element. Image forming device. It has a fixing portion for fixing the image formed on the recording material to the recording material.
The image forming apparatus according to claim 8 or 9, wherein a current flows through the power supply device during a period in which a current does not flow through the fixing portion. In an image forming apparatus to which an optional apparatus for processing an image-formed recording material is connected,
An image forming part for forming a toner image on the recording material,
The image forming unit, the first power supply device for supplying electric power, and
A second power supply device for supplying electric power to the optional device, and
With
The second power supply device
A transformer having a first primary winding and a second primary winding and a secondary winding,
A switching element connected in series with the primary winding and
A full-wave rectifier circuit that full-wave rectifies the input AC voltage,
A smoothing circuit having one end connected to the first primary winding and the other end connected to the second primary winding via the switching element.
A circuit connected to the output end of the full-wave rectifier circuit, in which an inductor and a rectifier element are connected in series, is provided.
The image forming apparatus, wherein the first primary winding has a larger number of turns than the second primary winding. The eleventh aspect of claim 11, wherein the larger the number of turns of the first primary winding than the number of turns of the second primary winding, the larger the current flowing through the inductor and the rectifying element. Image forming device. It has a fixing portion for fixing the image formed on the recording material to the recording material.
The image forming apparatus according to claim 11 or 12, wherein a current flows through the power supply device during a period in which a current does not flow through the fixing portion.

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