JP4833760B2 - Power control apparatus and power control method - Google Patents

Description

  The present invention relates to an improvement of an AC step-down chopper type power control device including a dimming device that outputs a sine wave, and more specifically, a dimming device that is used in a theater or a television studio and has a very wide load capacity and control range. The present invention relates to an improvement of an AC step-down chopper type power control device used for, for example.

  Conventionally, as an AC power control device such as a dimmer used in a theater or a television studio, a power control method using a thyristor element as a switching element and controlling its phase angle has been adopted.

  However, the load range and control range of dimmers in theaters and television studios are very wide, the dimmers range from tens to hundreds, and the power reception capacity reaches tens to hundreds kW. In addition, illuminating lamps with tens of watts to several kW are used and phase control is performed over a wide range of loads, so that sawtooth wave current flows through the main and load lines of the dimmer, and is used for sound equipment, etc. There are problems such as inductive disturbances of harmonics and the occurrence of roaring noise caused by sawtooth wave current when dimming an incandescent bulb.

  Therefore, an attempt has been made to perform power control such as dimming operation by controlling the duty ratio using an AC step-down chopper circuit using a power IGBT (Insulated Gate Bipolar Transistor) element. A power control device as a dimming device whose load is an illuminating lamp has been called a sine wave dimmer because its output is a sine wave. However, in the case of this sine wave dimmer, since the load range and control range are very wide as described above, the operation of the AC step-down chopper circuit tends to become unstable. In general, an IGBT element has a narrower allowable range for an overcurrent and a surge voltage than a thyristor element. Therefore, once an overvoltage or an overcurrent is generated, the IGBT element may be damaged due to the occurrence of the voltage.

  FIG. 1 shows an example of a power control apparatus using a conventional general AC step-down chopper circuit. A filter circuit including a reactor 2 and a capacitor 3 is connected between input terminals of the AC power source 1. The filter circuit reduces the high-frequency current accompanying the operation of the AC step-down chopper from flowing out to the power source. A rectifier bridge circuit 4 applies a positive voltage to the IGBT 5 as a main switch as a switching element regardless of the polarity of the power source. A signal with a controllable duty ratio of 30 to 50 kHz is applied between the gate and emitter of the IGBT 5 to turn on / off the main switch IGBT 5 to create a comb-shaped waveform asynchronous to the power supply waveform. Smoothing is performed by a smoothing circuit including the reactor 8 and the capacitor 9, and a sine wave voltage is supplied to the load 10.

  Between the rectifier bridge circuit 4 and the smoothing circuit, IGBTs 6 and IGBTs 7 which are sub switches are connected in antiparallel with these. The IGBT 7 is turned on in the positive half cycle of the power supply voltage, the IGBT 6 is turned on in the negative half cycle, and a fly that supplies the energy stored in the reactor 8 and the capacitor 9 to the load during the period when the IGBT 5 as the main switch is turned off. A wheel circuit 14 is formed.

  FIG. 2 shows the state of the output voltage when a resistive load is connected to a conventional power control apparatus. Reference numeral 12 denotes a power supply voltage, and reference numeral 11 denotes an output waveform of the IGBT 5 which is a main switch. This figure shows a case where the duty ratio of on / off of the main switch is 50%, and 13 shows a waveform of an output voltage obtained by smoothing this voltage. In this case, there is no delay between the power supply voltage 12 and the output voltage 13, that is, no phase difference is observed.

  FIG. 5 shows a case where the load voltage 62 is delayed with respect to the power supply voltage 61 and occurs when the load is connected to a light load or an inductive load. In this case, the energy stored in the reactor 8 and the capacitor 9 or the load 10 during the period when the IGBT 5 which is the main switch is OFF is not sufficiently discharged by the flywheel circuit 14, and therefore the load voltage 62 with respect to the power supply voltage 61. Will be delayed in phase.

  A waveform 63 represents the operation of the IGBT 5 that is the main switch, and is asynchronous with respect to the power supply voltage 61. The waveform 63 usually has a frequency of 30 kHz to 50 kHz, but for the sake of explanation, the frequency is reduced and displayed (the waveform 73 in FIG. 6 is also the same).

  The waveform 64 is the gate-emitter voltage of the IGBT 7 of the flywheel circuit 14. When the power supply voltage is positive, the logic is “1”, the collector-emitter is turned on, and the power supply voltage is negative. It becomes “0” and the collector-emitter is turned off. A waveform 65 is also the operation of the IGBT 6 of the flywheel circuit 14, and the collector-emitter is turned off during the positive period of the power supply voltage, and the collector-emitter is turned on during the negative period. The operations of the sub-switches 6 and 7 are synchronized with the power supply voltage and are switched when the power supply voltage crosses the zero point.

  In the conventional power control device configured as described above, the operations of the sub switches 6 and 7 of the flywheel circuit 14 are switched in a state where the load voltage 62 is applied, so that the main switch operating asynchronously with the power supply voltage is provided. At the moment of turning off, the load current becomes zero, and a very large surge voltage is generated and applied between the collectors and emitters of the IGBTs 5, 6 and 7 of the main switch and the sub switch. If it is high, it may cause damage beyond the maximum rating of the device.

  As a countermeasure against this surge voltage, US Patent No. 6346778 detects the current flowing through the main switch, and if a phase difference occurs between the current and the power supply voltage when the zero point crosses, the main switch is forcibly turned on. As a method, a method of releasing energy stored in a smoothing circuit to a power source has been proposed. However, this method must detect either the current flowing through the main switch or the corresponding collector-emitter voltage of the main switch, and only when the main switch is on. There is a drawback that the circuit configuration becomes very complicated.

US Patent No.6346778

  The present invention has been made in view of the above-described conventional circumstances, and the problem is that the phase difference between the zero point of the power supply voltage and the load voltage is detected with a very simple circuit configuration, and the phase difference is This type of power control is achieved by turning on the main switch to prevent the occurrence of surge voltage during the detected period, that is, during the phase difference, and regenerating the energy stored in the smoothing circuit to the power source. This is to improve the efficiency of the apparatus and the control characteristics.

In order to solve the above problem, the first invention is:
Switching element comprising at least a main switch and two sub switches, a flywheel circuit including the two sub switches, a full-wave rectifier circuit for rectifying an alternating current applied to the main switch, and turning on and off the main switch A power control method for an AC step-down chopper type power control device having a smoothing circuit for smoothing a comb waveform obtained by the above, wherein the phase difference when each AC voltage at the power input terminal and the output terminal crosses zero In the period when this phase difference is detected, the main switch is forcibly turned on and the two sub switches are forcibly turned off. .

The switching elements include not only IGBT elements but also power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) elements. The flywheel circuit is a circuit for regenerating electric power stored in the smoothing circuit to the power source while the main switch is off.
The phase difference is compared using the zero point of the AC voltage as a reference. The time difference between the zero points of the power supply side voltage and the output side voltage is the phase difference. Therefore, “during the period in which the phase difference is detected” refers to the time between the zero point of the power supply side voltage value and the zero point of the output side voltage value.

As a second invention,
Switching element comprising at least a main switch and two sub switches, a flywheel circuit including the two sub switches, a full-wave rectifier circuit for rectifying an alternating current applied to the main switch, and turning on and off the main switch In the AC step-down chopper type power control device provided with a smoothing circuit that smoothes the comb waveform obtained by the above, the power supply side polarity discriminator is provided between the power input terminals, and the output side polarity discriminator is provided between the output terminals, respectively. A power supply side polarity discriminator and a previous term output side polarity discriminator generate a polarity discrimination signal according to the positive / negative of the AC voltage, and the control circuit is configured based on the polarity discrimination signal. Detecting the phase difference when the AC voltages cross each zero point, and forcibly turning on the main switch during the period in which the phase difference is detected, And an AC step-down chopper type power control device for a force off serial two sub-switch.

  The switching elements include not only IGBT elements but also power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) elements. The flywheel circuit is a circuit for regenerating electric power stored in the smoothing circuit to the power source while the main switch is off.

  The polarity discriminator only needs to discriminate between positive and negative of the AC voltage and generate logic “1” when positive and logic “0” when negative. In this case, since it is sufficient to make a positive / negative discrimination, the logic may be “0” when positive and logic “1” when negative depending on the state of the logic circuit to be handled.

  The control circuit receives a positive / negative signal from the polarity discriminator, and calculates the phase difference when the AC voltage on the power source side and the output side crosses the zero point, that is, the time difference between the times when the voltage changes from positive to negative. Anything that outputs as “0” may be used. During the phase difference generation period, that is, during the time when this signal is logic “1” or logic “0”, a signal for turning on the main switch and a signal for turning off the sub switch are generated. These signals may be supplied to the drive circuits of the switching elements to control the main switch and the sub switch.

  The phase difference is compared using the zero point of the AC voltage as a reference. The difference between the zero point of the power supply side voltage and the output side voltage is the phase difference. Therefore, “during the period in which the phase difference is detected” refers to the time between the zero point of the power supply side voltage value and the zero point of the output side voltage value.

Furthermore, as a third invention,
3. The AC step-down chopper type power control device according to claim 2, wherein at least the polarity discriminator and the control circuit are configured by a one-chip microcomputer.

The polarity discriminator and the control circuit may be constituted by a wired logic circuit. In this case, each individual logic element can be mounted with an IC. However, a logic circuit may be realized using a microcomputer. In particular, mounting with a one-chip microcomputer is preferable because the entire apparatus can be made compact, so that space saving can be achieved and the economy is high.

  In a power control device such as a sine wave dimmer using an AC step-down chopper, a polarity discriminator that discriminates the polarity of the voltage is connected to the input power supply side and the output side, and the difference between the outputs of both discriminators is detected. While the differential output is logic “1” or logic “0”, the main switch is forcibly turned on and the sub switch is turned off, so that the energy of the smoothing circuit connected to the output side of the power control device is safe In addition, since there is no moment when both the main and sub switches are turned off, the power control device can be provided with high efficiency and good control characteristics without generating a surge voltage. Moreover, the polarity discriminator and the control circuit of the power source and the output can be easily realized by a simple digital circuit such as a comparator element, so that the economy is excellent.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 3 shows a power control apparatus according to the present invention, in which an AC power supply 15 is applied to an input terminal 16. In the next stage, the reactor 18 and the capacitor 19 constitute a filter circuit for reducing high-frequency current from flowing to the power source. Further, a full-wave rectifier block 20 including rectifiers D1, D2, D3, and D4 is connected to the next stage. In this full-wave rectifier block 20, an IGBT 21 as a main switch is connected between the positive and negative electrodes, and a drive circuit 22 is connected between the gate and the emitter. In the subsequent stage, a flywheel circuit 40 including sub switches 23 and 25 and rectifiers 24 and 26 is formed. The sub-switch IGBTs 23 and 25 are connected to rectifiers 24 and 26 for flowing a reverse current, respectively. Like the main switch, sub-switch drive circuits 27 and 28 are connected between the gate and the emitter, respectively.

  Further, a smoothing circuit 39 including a capacitor 29 and a reactor 30 is connected to the subsequent stage. The smoothing circuit 39 performs a smoothing action on the comb waveform accompanying the operation of the IGBT 21 as the main switch. An external load 32 is connected through an output terminal 37 of the power control device.

  A power source polarity discriminator 17 is connected between the power input terminals, and an output side polarity discriminator 31 is connected between the output terminals. The polarity discriminator is for detecting the zero point (zero cross point) of the voltage waveform. If the voltage waveform is positive, the logic “1” or logic “0” is set. If the voltage waveform is negative, the logic “0” or the logic is set. “1” is output. Details will be disclosed in the description of FIG. 4 (described later).

  The control circuit 33 receives a signal applied to the control input terminal 34 of the power control unit, and supplies it to the drive circuits 22, 27, 28 of the main switch 21 and the sub switches 23, 25 from the outputs of the polarity discriminators 17, 31. To generate a signal. Reference numerals 35 and 36 denote external control signal generators, which may be supplied as analog signals from the DC power supply 35 and the sliding resistor 36 as shown in the figure, or may be supplied as digital signals such as DMX. When the control circuit is realized using a microcomputer, it is preferably supplied as a digital signal. Details of the control circuit will also be disclosed in the description of FIG. 4 (described later).

  The operation of the power control apparatus according to the present invention will be described with reference to the waveform diagram of FIG. In FIG. 6, 61 is a power supply voltage waveform, and 62 is an output waveform. As seen in the vicinity of the zero point of the waveforms 61 and 62 in the same figure, there is a phase difference between the power supply voltage waveform 61 and the output waveform 62. 70 is the output of the power supply side polarity discriminator 17 of FIG. 3, which is a logic “1” when the power supply voltage 61 is positive and a logic “0” during a negative period. Reference numeral 71 denotes an output of the output side polarity discriminator 31 of FIG. 3, which is a logic “1” when the output voltage 62 is positive and a logic “0” during a negative period. When the difference between the waveform 70 and the waveform 71 is taken, a waveform 72 is obtained. While the waveform 72 is positive, the control signal 73 of the IGBT 21 that is the main switch is forcibly turned on, and the IGBTs 23, 25 control signals 74 and 75 are forcibly turned off. By operating in this way, the energy stored in the smoothing circuit is forcibly regenerated to the power source near the zero point, and the IGBTs 23 and 25 that are the sub switches are forced to be turned off, thereby the IGBT 21 that is the main switch. Even if is kept on, no short-circuit current flows.

  A specific representation of the polarity discriminators 17, 31 and the control circuit 33 is shown in FIG. In addition, the part and component which attached | subjected the same code | symbol as FIG. 3 shall have the same effect.

  In FIG. 4, resistors 41 and 42 constitute an input voltage divider of the power supply side polarity discriminator 17. The comparator 43 outputs a logic “1” when the power supply voltage is positive and outputs a logic “0” during the negative period. The resistors 44 and 45 constitute an input voltage divider of the output side polarity discriminator 31, and the comparator 46 outputs a logic "1" when the output voltage is positive and outputs a logic "1" during the negative period. “0” is output. When these comparator outputs are input to the exclusive OR circuit 47, the difference between the comparator outputs is taken, and the waveform 72 of FIG. 6 is obtained as the output of the exclusive OR circuit 47.

  4 is a PWM signal generator for generating a PWM (Pulse Width Modulation) signal to be supplied to the IGBT 21 as a main switch according to the signal voltage applied to the input signal terminal. The output and the exclusive OR circuit 47 described above are generated. 6 is input to the OR circuit 48, the control output waveform 73 of the main switch 21 shown in FIG. 6 is obtained, and the main switch 21 is forced to turn on during the period in which the phase difference of the zero crossing is detected. .

  Further, the output of the exclusive OR circuit 47 is connected to one input of the AND circuit 51 via the inverter circuit 49, and the output of the comparator 43 is connected to the other input, so that the output of the sub switch 25 of FIG. The control output waveform 74 is obtained. Further, the output of the comparator 43 is input to the inverter circuit 50, the output is connected to one input of the AND circuit 52, and the output of the inverter circuit 49 is connected to the other input. A control output 75 of the switch 23 is obtained.

  These control signals are supplied to the drive circuit 22 of the IGBT 21, which is the main switch, the drive circuit 27 of the sub switch 23, and the drive circuit 28 of the sub switch 25, respectively, and there is a phase difference near the zero point between the power supply voltage and the output voltage. However, both the main switch 21 and the sub switches 23 and 25 are not turned off, and the surplus energy stored in the smoothing circuit 39 is smoothly regenerated to the power source, and the sine wave modulation with good efficiency and good control characteristics is achieved. It is possible to provide a power control apparatus including an optical device.

  The control circuit including the comparators 43 and 46, the logic circuits 47 to 52, and the PWM signal generator 53 shown in FIG. 4 is the control circuit 33 shown in FIG. 3, and the control circuit 33 includes individual logic circuit ICs. Although it may be used and mounted, it may be constituted by a one-chip microcomputer.

  Further, in this description, the case where IGBT is used as the semiconductor switching element is described, but the circuit configuration according to the present invention can be similarly adopted even when a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used.

  Furthermore, various circuit systems have been proposed and put into practical use for the AC step-down chopper type power control device, but include a chopper smoothing circuit, or an inductive load is connected as a load. In a power control apparatus in which a phase difference may occur, the proposal of the present invention can be applied, and this is also within the scope of the present invention.

It is an example of the conventional power control apparatus. It is a waveform of the conventional power control apparatus when resistance addition is connected. 1 is a schematic block diagram of the present invention. It is a detailed block diagram of the present invention. It is a waveform of the conventional power control device when there is an inductive load. It is a waveform of the electric power control apparatus of this invention when there exists an inductive load.

Explanation of symbols

14: Flywheel circuit 15: AC power supply 16: Input terminal 17: Power supply side polarity discriminator 18: Reactor 19: Capacitor 20: Full wave rectifier block 21: Main switch 22: Drive circuit 23: Sub switch 24: Rectifier 25: Sub Switch 26: Rectifier 27: Drive circuit 28: Drive circuit 29: Capacitor 30: Reactor 31: Output side polarity discriminator 32: External load 33: Control circuit 34: Control input terminal 35: DC power supply 36: Resistor 37: Output terminal 38: Power control device
39: smoothing circuit 40: flywheel circuit 41: resistor 42: resistor 43: comparator 44: resistor 45: resistor 46: comparator 47: exclusive OR circuit 48: OR circuit 49: inverter circuit 50: inverter circuit 51: AND circuit 52: AND circuit 53: PWM signal generator 61: Power supply voltage waveform 62: Output waveform 70: Power supply side polarity discriminator output 71: Output side polarity discriminator output 72: Difference waveform 73: Control output of main switch Waveform 74: Subswitch control output waveform 75: Subswitch control output waveform

Claims (3)

Switching element comprising at least a main switch and two sub switches, a flywheel circuit including the two sub switches, a full-wave rectifier circuit for rectifying an alternating current applied to the main switch, and turning on and off the main switch A power control method for an AC step-down chopper type power control device having a smoothing circuit for smoothing a comb waveform obtained by the above, wherein the phase difference when each AC voltage at the power input terminal and the output terminal crosses zero During the period when this phase difference is detected, the main switch is forcibly turned on and the two sub switches are forcibly turned off, thereby preventing the occurrence of surge voltage and the smoothing. A power control method for an AC step-down chopper type power control device, wherein electrical energy stored in a circuit is regenerated to a power source. Switching element comprising at least a main switch and two sub switches, a flywheel circuit including the two sub switches, a full-wave rectifier circuit for rectifying an alternating current applied to the main switch, and turning on and off the main switch In the AC step-down chopper type power control device provided with a smoothing circuit for smoothing the comb waveform obtained by the above, the power supply side polarity discriminator is provided between the power input terminals, and the output side polarity discriminator is provided between the output terminals. The power supply side polarity discriminator and the output side polarity discriminator generate a polarity discrimination signal according to the polarity of the AC voltage, and the control circuit outputs the power source side and the output side based on the polarity discrimination signal. The phase difference when the AC voltage on the side crosses each zero point is detected, and the main switch is forcibly turned on during the period when the phase difference is detected. An AC step-down chopper type power control device characterized by preventing the generation of a surge voltage by forcibly turning off the two sub-switches and regenerating electrical energy stored in the smoothing circuit to a power source . 3. The AC step-down chopper type power control apparatus according to claim 2, wherein at least the polarity discriminator and the control circuit are configured by a one-chip microcomputer.

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