JP2011200069A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize improvement in power factor and suppression in higher harmonics of a power supply.SOLUTION: The power supply generates a DC output voltage by PWM-controlling a switching element using a step-up chopper method with respect to a pulsating voltage which is obtained by rectifying an AC input voltage. A time difference between a peak timing of input voltage and that of an input current is detected. According to the time difference, one switching pattern is selected from among a plurality of switching patterns prepared in advance. The duty of each pulse of the selected switching pattern is adjusted according to the voltage difference between the output voltage and a target voltage. The switching element is PWM-controlled by the switching pattern that has been adjusted.

Description

  The present invention relates to a power supply apparatus that rectifies an AC input voltage and generates a DC output voltage by a boost chopper method.

  Harmonic current generated by the power supply unit causes many obstacles to other electrical equipment connected to a common AC power supply, so suppression of these harmonic currents is important, and standards for that are established. . When manufacturing electrical equipment, this harmonic standard must be cleared.

  A power supply circuit that converts AC power into DC is generally of a capacitor input type. However, such a power supply circuit has a distorted wave of input current, resulting in poor input power factor and generation of harmonic current. Therefore, in order to improve the input power factor and reduce the harmonic current, in the step-up chopper type power supply device that performs PWM control of the switching element, the input current and the input voltage are substantially in phase with a substantially sine wave. In addition, switching is controlled (see, for example, Patent Document 1).

  Specifically, the input current sensor detects the input current value, the zero-cross detection circuit detects the input AC zero-cross point, performs input frequency discrimination and interrupt processing, and when the zero-cross point is detected, the detected input The input current waveform is controlled by PWM control of the switching element with a switching pattern corresponding to the current.

JP-A-5-68375

  However, when the input current waveform is controlled using the zero cross point as a reference, when the input current waveform is distorted (the peak timing is shifted from the center of the zero cross points on both sides), the input current is detected only by detecting the zero cross point. As a result, the switching control in which the input current is similar to the input voltage cannot be performed.

  An object of the present invention is to provide a power supply device that sufficiently realizes power factor improvement and harmonic suppression by PWM control of a switching element according to a comparison result of peak timing of input voltage and peak timing of input current. It is.

In order to achieve the above object, a power supply apparatus according to a first aspect of the present invention generates a DC output voltage by PWM-controlling a switching element by a boost chopper method with respect to a voltage obtained by rectifying an AC voltage. In the power supply apparatus, the input voltage peak timing detecting means for detecting the peak timing of the input voltage, the input current peak timing detecting means for detecting the peak timing of the input current, the input voltage peak timing detecting means, and the input current peak timing And a peak timing comparing means for comparing the input voltage peak timing detected by the detecting means with the input current timing, and PWM controlling the switching element according to the comparison result of the peak timing comparing means. To do.
According to a second aspect of the present invention, in the power supply device according to the first aspect, in accordance with a time difference between the peak timing of the input voltage and the peak timing of the input current, which is a comparison result of the peak timing comparison unit, The switching element is PWM controlled.
According to a third aspect of the present invention, in the power supply device according to the second aspect, the storage unit stores a plurality of switching patterns in advance, and the plurality of switching patterns stored in the storage unit according to the time difference. Switching pattern selection means for selecting one switching pattern, and PWM control of the switching element is performed by the selected switching pattern.
According to a fourth aspect of the present invention, there is provided the power supply device according to the third aspect, further comprising duty adjustment means for adjusting a duty of each pulse of the selected switching pattern according to a voltage difference between the output voltage and the target voltage. And the switching element is PWM-controlled by a switching pattern in which the duty of each pulse is adjusted by the duty adjusting means.

  According to the power supply device of the present invention, since the switching element is PWM-controlled according to the comparison result of the peak timing of the input voltage and the input current, the phase of the input voltage and the input current can be made uniform, the power factor improvement and the harmonics Can be suppressed. Further, since switching need not be performed more than necessary, switching noise can be suppressed. Further, since the control is performed so that the current phase is similar to the voltage phase even when the input current is disturbed (distortion or the like) that cannot be read only by the zero cross point, harmonics can be suppressed in this aspect as well. Thus, this invention can implement | achieve power factor improvement and harmonic suppression more fully.

It is a block diagram which shows the structure of the power supply device of the Example of this invention. It is a block diagram which shows the detail of the control part of the power supply device of FIG. It is operation | movement explanatory drawing when the peak timing of input current is ahead with respect to the peak timing of input voltage. In operation explanatory diagram when the peak timing of input voltage and input current match It is operation | movement explanatory drawing when the peak timing of input current is late with respect to the peak timing of input voltage. It is a flowchart of operation | movement of the power supply device of FIG.

  In the present invention, the switching pattern of the PWM signal for controlling the switching element is predicted according to the shift of the input current peak timing with respect to the peak timing of the input voltage, that is, the delay or advance of the input current phase. Then, the duty of each pulse of the switching pattern is adjusted according to the voltage difference between the output voltage and the target voltage.

  FIG. 1 shows a configuration block of a boost chopper type power supply device according to an embodiment of the present invention. 1 is a diode bridge circuit for full-wave rectification of the input voltage of a commercial AC power supply (50 Hz or 60 Hz), 2 is a boosting reactor, 3 is a diode for preventing reverse current flow, 4 is a switching transistor, 5 is for detecting input current A resistor, 6 is a capacitor for smoothing the output voltage, 7 is a voltage dividing circuit for dividing the output voltage across the capacitor 6, 8 is a motor drive circuit (inverter), 9 is a three-phase motor, and 10 is a control unit.

  The control unit 10 includes a zero-cross detection unit 11 that detects a zero-cross point of an AC input voltage, an input voltage detection unit 12 that detects a full-wave rectified rectified voltage, and an AC input current that is generated at both ends of the resistor 5. Each detection signal from the input current detection unit 13 to detect and the output voltage detection unit 15 to detect the DC output voltage by the voltage obtained by the voltage dividing circuit 7 is taken in and processed.

  And according to the result of the process in the control part 10, the drive circuit 14 switches the switching transistor 4 by PWM control. Further, the control unit 10 controls the inverter driving unit 16 that drives the motor driving circuit 8. The control unit 10 further includes a storage unit 10a for storing a processing program, input values, calculation results, other data, and a CPU (not shown) for control.

  FIG. 2 shows functional blocks of the control unit 10. The control unit 10 includes a switching permission signal generation unit 101, an input voltage peak timing detection unit 102, an input current peak timing detection unit 103, a peak timing difference detection unit 104, a switching pattern selection unit 105, an output voltage average calculation unit 106, an adder 107, a PI control unit 108, and a switching duty adjustment unit 109.

  The switching permission signal generation unit 101 generates a switching permission signal based on the detection signal from the zero cross detection unit 11. The switching permission signal is a signal for permitting the start of switching, and is output after a predetermined time elapses after the zero cross is detected by the zero cross detection unit 11.

  The input voltage peak timing detection unit 102 takes in the detection signal from the zero-cross detection unit 11 and the detection signal from the input voltage detection unit 12, thereby 1 ms for every half cycle from the zero-cross point of the input voltage to the next zero-cross point. The input voltage is measured in units and stored in the storage unit 10a. Then, the maximum value is detected from the stored measurement result during the half cycle of the power supply, and the time at that time is set as the voltage peak timing t1.

  The input current peak timing detection unit 103 takes in the detection signal from the zero-cross detection unit 11 and the detection signal from the input current detection unit 13, so that it takes 1 ms for every half cycle from the zero-cross point of the input voltage to the next zero-cross point. The input current is measured in units and stored in the storage unit 10a. Then, the maximum value is detected from the stored measurement result during the half cycle of the power supply, and the time at that time is set as the current peak timing t2.

  The peak timing difference detection unit 104 is a time difference Δt (= t1-t2) between the voltage peak timing t1 obtained by the input voltage peak timing detection unit 102 and the current peak timing t2 obtained by the input current peak timing detection unit 103. Is calculated.

  The switching pattern selection unit 105 selects one switching pattern from a plurality of switching patterns (duty patterns of PWM signals) stored in advance in the storage unit 10a according to the time difference Δt detected by the peak timing difference detection unit 104. . The duty of each pulse of the switching pattern stored in the storage unit 10a is determined in advance based on the polarity and magnitude of the time difference of the peak timing, the capacity of the reactor 2, and the like.

  In the step-up chopper type power supply device, the higher the input current (the larger the load), the higher the harmonics. In addition, when the switching frequency of the switching element is constant, the phase delay of the input current increases and the harmonics increase as the reactor capacity increases. Normally, the reactor capacity is constant. In this case, the lower the switching frequency, the higher the harmonics and the greater the reactor noise. Since there is such a relationship, this is reflected in a plurality of switching patterns stored in the storage unit 10a.

  The output voltage average calculation unit 106 detects the output voltage in units of 1 ms based on the detection signal from the output voltage detection unit 15 and stores it in the storage unit 10a. Then, the average output voltage is calculated every 1 ms by averaging the stored measurement results for the past 100 ms.

  The adder 107 obtains a voltage difference by adding the target output voltage and the average output voltage, and the PI control unit 108 obtains an integrated value of the voltage difference to generate a control amount (reference duty: reference PWM pulse width). And sent to the switching duty adjustment unit 109.

  The switching duty adjustment unit 109 sets the switching pattern selected by the switching pattern selection unit 105 and adjusts the duty of each pulse of the switching pattern with a control amount corresponding to the voltage difference input from the PI control unit 108.

  FIG. 3 shows a waveform when the peak timing of the input current is advanced with respect to the input voltage (current phase advance). In this case, the switching pattern selection unit 105 uses the switching pattern that causes the input current waveform to approach the input voltage waveform for the phase delay, for example, the duty of the pulse width is “large / medium / small / small / medium / medium”. A switching pattern of a combination of pulses is selected and set in the switching duty adjustment unit 109.

  FIG. 4 shows a waveform when the peak timing of the input voltage and the input current coincide. In this case, the switching pattern selection unit 105 uses the switching pattern for adjusting the phase so that the input current waveform is brought close to the input voltage waveform, for example, a duty having a pulse width of “large / medium / medium / small / small / small”. The switching pattern of the combination of pulses is selected and set in the switching duty adjustment unit 109.

  FIG. 5 shows a waveform when the peak timing of the input current is delayed with respect to the input voltage (current phase delay). In this case, the switching pattern selection unit 105 causes the phase advance, such as a switching pattern that brings the input current waveform closer to the input voltage waveform, for example, a pulse with a duty of “large / medium / medium / small / small”. A combination switching pattern is selected and set in the switching duty adjustment unit 109.

  Since the control amount from the PI control unit 108 is also input to the switching duty adjustment unit 109 as a reference duty (reference PWM pulse width) corresponding to the output voltage, the switching duty adjustment unit 109 includes a switching pattern selection unit 105. The duty of each pulse of the switching pattern selected by is adjusted according to the reference duty. For example, if the average output voltage is higher than the target output voltage, the duty of each pulse is adjusted to be small, and if it is low, the duty is adjusted to be large.

  As described above, the switching transistor 4 is PWM-controlled so that the input current waveform approaches the input voltage waveform and the value of the output voltage approaches the target voltage. FIG. 6 shows a flowchart of the control operation. Processing from calculation of the peak timing of voltage and current (S2) to calculation of switching pattern (S4) via calculation of time difference of peak timing (S3), and determination of reference duty from calculation of output voltage (S5) ( The processes up to S6) are performed in parallel. Note that there is a difference in processing time between the route of step S2 → S3 → S4 and the route of step S5 → S6, but the latter route is continuously processed, and the processing of the former route is finished. The reference duty is used when the switching pattern is determined.

  In this embodiment, from the time difference between the peak timing of the input voltage and the input current, a switching pattern is determined so that the input current waveform approximates the input voltage waveform, so that switching control is performed so that the current waveform is similar to the voltage waveform, Harmonic suppression and power factor improvement are possible. Further, since control is performed by selecting a switching pattern stored in advance based on the time difference between the peak timings of the input voltage and the input current, the followability of the control is better than in the prior art. By mounting such a power supply device on, for example, an outdoor unit of an air conditioner, it exerts a great effect on harmonic suppression and power factor improvement with respect to load fluctuation and input power supply voltage fluctuation.

1: diode bridge circuit, 2: reactor, 3: diode, 4: switching transistor, 5: resistor, 6: capacitor, 7: voltage divider circuit, 8: motor drive circuit, 9: three-phase motor, 10: control unit 11 : Zero cross detection unit, 12: input voltage detection unit, 13: input current detection unit, 14: drive circuit, 15: output voltage detection unit, 16: inverter drive unit 101: switching permission signal generation unit, 102: input voltage peak timing Detection unit, 103: Input current peak timing detection unit, 104: Peak timing difference detection unit, 105: Switching pattern selection unit, 106: Output voltage average calculation unit, 107: Adder, 108: PI control unit, 109: Switching duty Adjustment section

Claims (4)

In a power supply device that generates a DC output voltage by PWM control of a switching element by a boost chopper method with respect to a voltage obtained by rectifying an AC voltage,
Input voltage peak timing detection means for detecting the peak timing of the input voltage;
Input current peak timing detection means for detecting the input current peak timing;
Peak timing comparison means for comparing the input voltage peak timing and the input current timing detected by the input voltage peak timing detection means and the input current peak timing detection means,
A power supply apparatus that performs PWM control of the switching element in accordance with a comparison result of the peak timing comparison means. The power supply device according to claim 1,
The power supply apparatus according to claim 1, wherein the switching element is PWM-controlled according to a time difference between the peak timing of the input voltage and the peak timing of the input current, which is a comparison result of the peak timing comparison means. The power supply device according to claim 2,
Furthermore, storage means for storing a plurality of switching patterns in advance, and switching pattern selection means for selecting one switching pattern from the plurality of switching patterns stored in the storage means according to the time difference,
The power supply apparatus according to claim 1, wherein the switching element is PWM-controlled by the selected switching pattern. The power supply device according to claim 3,
Furthermore, it comprises a duty adjustment means for adjusting the duty of each pulse of the selected switching pattern according to the voltage difference between the output voltage and the target voltage,
The power supply apparatus according to claim 1, wherein the switching element is PWM-controlled by a switching pattern in which the duty of each pulse is adjusted by the duty adjusting means.

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