JP2012090504A - Power supply device - Google Patents

Abstract

A power supply device that changes the on / off frequency of a switching element according to a required voltage is provided.
In a power supply device 10 for supplying a predetermined voltage power by boosting DC power obtained by converting AC power by a rectifier circuit 11 by switching on and off a switching element 13 provided in a boost chopper circuit 12. A plurality of on / off operating frequencies of the switching element 13 are set, and one of the operating frequencies is selected according to the voltage required by the load device 15, and the on / off duty ratio of the switching element 13 is set at the selected operating frequency. Change and output the required voltage of device 15 [Selection] Fig. 1

Description

The present invention relates to a power supply device that converts AC power into DC power.

Conventionally, a device such as a compressor or a motor whose required voltage value changes depending on the operating situation is provided with a boost chopper circuit (PAM circuit) as shown in Patent Document 1, for example, and the power of the voltage required by the device Is used.
This power supply apparatus has a reactor element and a switching element in a boost chopper circuit, and supplies DC power obtained by rectifying AC power from an AC power supply to the boost chopper circuit.
The step-up chopper circuit stores the DC power supplied by turning on the switching element and storing it as energy in the reactor element, turning off the switching element and releasing the energy stored in the reactor element. Supply to equipment.
The power supply device changes the step-up rate of the DC power by changing the on / off duty ratio of the switching element according to the voltage required by the device.

JP 2000-50668 A

However, it is common to adjust the duty ratio by fixing the on / off frequency of the switching element and changing the on time, and the power consumed by switching the on / off of the switching element is the magnitude of the voltage required by the device. It was almost the same regardless of.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power supply device that changes the on / off frequency of a switching element according to a required voltage.

A power supply apparatus according to the present invention that meets the above-described object is a power supply that supplies DC power by boosting DC power obtained by converting AC power by a rectifier circuit by switching on and off a switching element provided in a boost chopper circuit. In the supply device, a plurality of on / off operating frequencies of the switching element are set in advance, one of the operating frequencies is selected according to a voltage required by a device as a load, and the switching element is selected at the selected operating frequency. The required voltage of the device is output while changing the on / off duty ratio.

In the power supply device according to the present invention, it is preferable that the on / off switching of the switching element is performed at a timing that is based on a zero cross point detection time of the AC power voltage (that is, a start point).

In the power supply device according to the present invention, at the operating frequency in which the switching element is switched on and off a plurality of times at a time interval for detecting the zero-cross point, the on-time of the switching element per cycle is closer to the zero-cross point. Long is preferred.

In the power supply apparatus according to the present invention, the operation frequency is two types of low frequency and high frequency having different frequencies, and when the required voltage of the device is lower than a reference voltage to be compared, the low frequency operation is performed. When the frequency is selected and the required voltage of the device is higher than the reference voltage, it is preferable to select the high operating frequency.

The power supply device according to the present invention sets a plurality of switching element on / off operating frequencies in advance, selects one of the operating frequencies according to the voltage required by the device, and switches the switching element on / off at the selected operating frequency. Therefore, when the required voltage is low, it is possible to suppress the system power consumption by turning on and off the switching element at a frequency lower than the high frequency operating frequency required when the required voltage is high. is there.

In the power supply device according to the present invention, when switching of the switching element is performed at a timing based on the detection of the zero-cross point of the AC power voltage, the switching element is switched at a predetermined phase with respect to the AC power voltage waveform. It can be turned on and off, and it is possible to reliably improve harmonics

In the power supply device according to the present invention, when the on-off switching of the switching element is performed a plurality of times at a time interval for detecting the zero-cross point and the on-time of the switching element per cycle is longer as the zero-cross point is closer, the rectifier circuit The waveform of the current input to can be made close to a sine wave, and harmonics can be improved efficiently.

In the power supply device according to the present invention, when the operating frequency is two types of low frequency and high frequency having different frequencies, and the required voltage of the device is lower than the reference voltage, the operating frequency of the low frequency is selected, When the required voltage of the device is higher than the reference voltage, when selecting a high-frequency operating frequency, the control for selecting the operating frequency can be simplified, and the program design necessary for this control, etc. The cost can be suppressed.

1 is a circuit diagram of a power supply device according to an embodiment of the present invention. It is explanatory drawing which shows on-off switching and the output voltage of the switching element of the power supply device. It is a flowchart which shows on-off control of the switching element of the power supply device.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIG. 1, a power supply device 10 according to an embodiment of the present invention switches on / off of a switching element 13 provided in a boost chopper circuit 12 by converting DC power obtained by converting AC power by a rectifier circuit 11. It is a device that boosts the voltage and supplies power of a predetermined voltage. Hereinafter, these will be described in detail.

The power supply device 10 includes an AC power source 14 that outputs AC power, a rectifier circuit 11 that rectifies AC power from the AC power source 14 and converts the AC power into DC power (hereinafter also simply referred to as “power”), and a rectifier circuit 11. Is provided with a step-up chopper circuit 12 for stepping up the electric power sent from the device 15 and supplies electric power to a device 15 serving as a load.
The device 15 is a compressor in the present embodiment, and the slip amount of the compressor motor is adjusted by the magnitude of the voltage of the electric power supplied from the power supply device 10, and the operation rotational speed can be changed.
In addition, the power supply device 10 is provided with a control unit 17 that performs on / off switching (switching) control of the switching element 13 and the like. The control means 17 transmits a signal for on / off switching to the switching element 13 via the switching control circuit 16 signal-connected to the switching element 13. The switching element 13 performs on / off switching according to a signal from the switching control circuit 16.

The rectifier circuit 11 is provided with a plurality of diodes 18 connected in a bridge shape and input terminals 19 and 19a to which AC power from the AC power supply 14 is input.
The AC power supplied to the rectifier circuit 11 via the input terminals 19 and 19a is rectified by the diode 18 and supplied to the boost chopper circuit 12 as DC power via the output terminal 20 provided in the rectifier circuit 11. .

The step-up chopper circuit 12 includes a reactor 21 composed of a choke coil that is connected to an AC power supply 14 through input terminals 19 and 19a and an output terminal 20, and DC power transmitted from the output terminal 20 to the reactor 21 is provided. Can store energy.
The reactor 21 is provided in the step-up chopper circuit 12 and is connected to a smoothing capacitor 23 connected in parallel with the device 15.
By providing the smoothing capacitor 23, the boost chopper circuit 12 can smooth the power output from the reactor 21 and supply it to the device 15.
A diode 24 is disposed between the reactor 21 and the smoothing capacitor 23 to prevent power from flowing back from the smoothing capacitor 23 to the reactor 21.

The boost chopper circuit 12 is provided with a switching element 13 that electrically connects the output side of the reactor 21 and the rectifier circuit 11. The switching element 13 forms a short circuit that connects the output side of the reactor 21 and the rectifier circuit 11 in the ON state, and circulates the power output from the output terminal 20 of the rectifier circuit 11 and passing through the reactor 21 to the rectifier circuit 11. A circuit is provided to ensure that energy is stored in the reactor 21.
And the switching element 13 can cut | disconnect the short circuit which connects the output side of the reactor 21 and the rectifier circuit 11 in an OFF state, and can switch the output destination of the electric power from the reactor 21 to the smoothing capacitor 23 side.

The control means 17 is composed of, for example, a microcomputer, is loaded with a program for performing on / off control of the switching element 13, and mainly has an information storage function, a calculation function, and a data communication function.
In the control means 17, a plurality of on / off operating frequencies of the switching elements 13 having different frequencies are set in advance (two types of low frequency and high frequency having different frequencies in this embodiment). When the control means 17 receives a signal of the required voltage required for the power together with a signal for requesting power supply from the device 15, either the low frequency operating frequency or the high frequency operating frequency is determined according to the magnitude of the required voltage. In order to switch the switching element 13 on and off at the selected operating frequency, an on / off switching signal for that purpose is output to the switching element 13.

The power supply apparatus 10 is provided with an output voltage measurement circuit 25 that measures the voltage value of the power supplied from the boost chopper circuit 12 to the device 15.
The output voltage measurement circuit 25 is signal-connected to the control means 17, and the control means 17 is the magnitude of the voltage of power (hereinafter also referred to as “output voltage”) supplied to the device 15 via the output voltage measurement circuit 25. Can be detected.
The control means 17 measures the output voltage supplied to the device 15 via the output voltage measurement circuit 25 at a predetermined time interval while transmitting an on / off switching signal of the selected operating frequency to the switching element 13. The measured voltage is compared with the required voltage of the device 15.
Based on the comparison result of the measured output voltage and the required voltage of the device 15, the control means 17 changes the ratio of the on-time to the total on-off time of the switching element 13, that is, the on-off duty ratio, if necessary. The step-up chopper circuit 12 outputs the required voltage required by the device 15 to the device 15.

In addition, the power supply device 10 is provided with an input voltage measurement circuit 26 that measures an AC voltage output from the AC power supply 14.
The input voltage measurement circuit 26 is signal-connected to the control means 17, and the voltage of AC power output from the AC power supply 14 via the input voltage measurement circuit 26 by the control means 17 (hereinafter also referred to as “AC voltage”). Can be detected.
Since the input voltage measurement circuit 26 is equipped with an AD conversion chip that performs conversion processing between an analog signal and a digital signal, the control means 17 having a digital signal communication interface is connected to the AC power supply via the input voltage measurement circuit 26. AC voltage from 14 can be detected.
The switching control circuit 16 and the output voltage measurement circuit 25 are each equipped with an AD conversion chip that converts an analog signal and a digital signal.

The control means 17 detects the waveform of the alternating voltage based on the alternating voltage of the alternating current power supply 14 measured via the input voltage measuring circuit 26, and detects a zero cross point (see FIG. 2) at which the positive region and the negative region of the waveform are switched. To detect.
The control means 17 outputs a signal for on / off switching to the switching element 13 based on the detection time of the zero cross point, and the on / off switching of the switching element 13 is performed at a timing based on the time of detection of the zero cross point. .
As a result, the switching element 13 is operated a predetermined number of times from when the control means 17 detects the zero cross point until the next zero cross point is detected, that is, with respect to the half cycle (180 degrees) of the AC voltage waveform of the AC power supply 14 On-off switching can be performed reliably.

As shown in FIG. 2, the low-frequency operating frequency and the high-frequency operating frequency are the frequency at which the switching element 13 is turned on once for the half cycle of the AC voltage waveform of the AC power supply 14, and the switching element 13 The frequency that is turned on a plurality of times, and the high-frequency operating frequency is higher than the low-frequency operating frequency.
Note that the switching element may be turned on a plurality of times for a half cycle of the AC voltage waveform of the AC power source as long as the low frequency operating frequency is lower than the high frequency operating frequency.
In the present embodiment, two types of operating frequencies are stored in the control unit. However, three or more types of operating frequencies are set in the control unit, and one of the set three or more types of operating frequencies is set. It is also possible to control ON / OFF of the switching element by selecting.

As shown in FIG. 2, at a high frequency operating frequency in which the switching element 13 is switched on and off a plurality of times at a time interval (that is, around a half cycle of the AC voltage waveform of the AC power supply 14) when the control means 17 detects the zero cross point. The on-time of the switching element 13 immediately before or immediately after the point (that is, in the vicinity) is longer than the on-time of the switching element 13 in the intermediate time region near the center of one zero cross point and the next zero cross point. Actually, also in FIG. 2, the on-time of the switching element 13 is longer than the time T2 at the center of one zero-cross point and the next zero-cross point at the time T1 immediately before and after the zero-cross point.
Therefore, the ON time of the switching element 13 per cycle of switching the switching element 13 becomes longer as it approaches the zero cross point, and at the time t when the switching element 13 is turned ON during the half cycle of the AC voltage waveform. The t × V multiplied by the voltage V during this period is the same or a constant range (for example, a range of ± 30%).
As a result, the waveform of the current input to the rectifier circuit 11 approaches a sine wave, and harmonics are improved.

Next, a method for controlling the switching element 13 by the control means 17 will be described in detail.
As shown in FIG. 3, when the control means 17 receives a command signal for requesting power supply from the device 15, the control means 17 acquires magnitude information of the required voltage required for the power from the command signal (step S1). The magnitude of the required voltage is compared with a reference voltage previously set in the storage area of the control means 17 (step S2).

This reference voltage is set when the operating frequency is set in the control means 17, and it is determined whether the control means 17 selects an operating frequency of low frequency or high frequency for on / off switching control of the switching element 13. It becomes a criterion for determination.
The control means 17 selects a low-frequency operating frequency and a high-frequency operating frequency, respectively, when the required voltage is lower than the reference voltage and when it is equal to or higher than the reference value.
This is because a voltage lower than the reference voltage can be output to the device 15 when the switching element 13 is switched on and off at a low operating frequency, and a voltage higher than the reference voltage is switched on and off when the switching element 13 is switched on and off at a high frequency. This is because the data can be output to the device 15.
When N (N ≧ 3) operating frequencies are set in the control means, N−1 reference voltages are set in the control means, and the control means has a magnitude (high / low) relationship between the required voltage and each reference voltage. From the N operating frequencies, one operating frequency capable of outputting the required voltage to the device is selected.

When the required voltage is higher than the reference voltage to be compared (including the same case) in step S2, the control means 17 selects a high-frequency operating frequency and starts transmitting an on / off switching signal to the switching element 13 using the high-frequency operating frequency. (Step S3).
On the other hand, when the required voltage is lower than the reference voltage to be compared, the control means 17 selects a low-frequency operating frequency and starts transmitting an on / off switching signal with the low-frequency operating frequency to the switching element 13 (step S3 ′). .
In the present embodiment, the control means selects the high frequency operating frequency when the required voltage and the reference voltage are the same. However, when the required voltage and the reference voltage are the same, the control means selects the low frequency operating frequency. It may be.

Next, the control means 17 measures the output voltage output to the device 15 via the output voltage measurement circuit 25 (step S4 or step S4 ′), and adjusts the duty ratio so that the output voltage approaches the required voltage. Perform (Step S5 or Step S5 ′). Specifically, the duty ratio is increased to increase the output voltage, and the duty ratio is decreased to decrease the output voltage.
In the present embodiment, the adjustment of the duty ratio is performed by PID control based on the required voltage of the device 15 and the measured output voltage, but other feedback control can also be used.
Further, if the output voltage is within a range of ± α% with respect to the required voltage, control for maintaining the value of the duty ratio may be performed. α is a numerical value in the range of 2 to 10, for example.

The adjustment of the duty ratio by one operating frequency performed in step S5 (or step S5 ′) is performed when the control unit 17 receives a power supply stop signal from the device 15 or the like (step S6-1), or This is performed until a command signal for a new required voltage is received from the device 15 (step S7).
When the control means 17 receives the power supply stop signal (step S6-1), the duty ratio adjustment is stopped and the transmission of the on / off switching signal to the switching element 13 is stopped, and the power supply to the device 15 is ended. (Step S6-2).
On the other hand, when the control means 17 receives a command signal of a new required voltage from the device 15 (step S7), the control means 17 returns to step S1, acquires the value of the required voltage from the received command signal, A new required voltage is compared to select one of a high frequency operating frequency and a low frequency operating frequency.
By the on / off switching control of the switching element 13 by the control unit 17, the power supply device 10 can output the output power having the same magnitude (substantially the same) as the required voltage to the device 15.

FIG. 2 shows the relationship between the on / off switching of the switching element 13, the required voltage, and the output voltage for a certain time when the switching element 13 is switched on / off.
The time regions D1 and D2 shown in FIG. 2 are time zones in which the switching element 13 is switched on and off at a low operating frequency, and after each zero cross point is detected, the next zero cross point is detected. Is a time region until the next zero cross point is detected from the end point of D1.
Since the output voltage is lower than the required voltage in the time domain D1, the control unit 17 transmits an on / off switching signal for making the duty ratio larger than that in the time domain D1 to the switching element 13 in order to increase the output voltage in the time domain D2. For this reason, the ON time W2 of the switching element 13 in the time domain D2 is longer than the ON time W1 of the switching element 13 in the time domain D1.

When the required voltage becomes substantially the same value as the output voltage, the change in the output voltage becomes small together with the change rate of the duty ratio, and the output voltage becomes a stable state in which the change with time is minute.
In the example of FIG. 2, the output voltage and the required voltage are in a stable state just before the end of the time domain D <b> 2, and then a new required voltage signal is transmitted from the device 15 to the control means 17. Since the required voltage is higher than the reference voltage, the control unit 17 selects a high-frequency operating frequency and continues to control on / off switching of the switching element 13 at the selected high-frequency operating frequency.

Since the control means 17 selects the operating frequency of the switching element 13 according to the magnitude of the required voltage, when the required voltage is low, the switching element 13 is switched on and off at a low frequency, and the switching element 13 is turned on and off. Power consumption can be reduced.
Therefore, in the power supply device 10, system power consumption is suppressed, and as a result, the power factor can be improved. In the measurement by experiment, the system power consumption is 10 W in the power supply apparatus 10 while the system power consumption is 40 W in the power supply apparatus having a fixed operating frequency.
In addition, since the power supply device 10 is only changed from the conventional power supply device mainly in the program installed in the control means, the design cost and the like can be suppressed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and all changes in conditions and the like that do not depart from the gist are within the scope of the present invention.
For example, the power supply device can also be used for power supply to devices other than the compressor, such as a motor that changes the required voltage depending on the operation status.

DESCRIPTION OF SYMBOLS 10: Power supply device, 11: Rectifier circuit, 12: Boost chopper circuit, 13: Switching element, 14: AC power supply, 15: Apparatus, 16: Switching control circuit, 17: Control means, 18: Diode, 19, 19a: Input terminal, 20: output terminal, 21: reactor, 23: smoothing capacitor, 24: diode, 25: output voltage measurement circuit, 26: input voltage measurement circuit

Claims (4)

In a power supply device that boosts DC power obtained by converting AC power by a rectifier circuit by switching on and off a switching element provided in a boost chopper circuit and supplies power of a predetermined voltage,
A plurality of on / off operating frequencies of the switching element are set in advance, and one of the operating frequencies is selected according to a voltage required by a load device, and the on / off duty of the switching element is selected at the selected operating frequency. A power supply apparatus that outputs a required voltage of the device by changing a ratio. The power supply apparatus according to claim 1, wherein the switching element is switched on and off at a timing based on a time when a zero-cross point of the voltage of the AC power is detected. 3. The power supply device according to claim 2, wherein the on-time of the switching element per cycle is close to the zero-cross point at the operating frequency at which the switching element is switched on and off a plurality of times at time intervals for detecting the zero-cross point. A power supply device characterized by being so long. The power supply device according to any one of claims 1 to 3, wherein the operating frequency is two types of low frequency and high frequency having different frequencies, and the required voltage of the device is lower than a reference voltage to be compared. In the case, the power supply device is characterized in that the low-frequency operation frequency is selected, and the high-frequency operation frequency is selected when the required voltage of the device is higher than the reference voltage.

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