JP2008099510A - Dc power supply and equipment using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease the maximum value of a ripple current that flows a capacitor in a DC power supply intended for reduced harmonic current and higher power factor. <P>SOLUTION: The DC power supply comprises a diode bridge 6 connected to an AC power supply 1 through a reactor 8, a capacitor 10 connected between an AC input terminal of the diode bridge 6 and a DC output terminal through a switch 9, a zero cross detecting means 13, a switch control means 16, a DC voltage detecting means 17, and an AC voltage estimating means 19. The ripple current flowing the capacitor 10 can be prevented from increasing by lowering a target voltage when the voltage of the AC power supply 1 drops. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a DC power supply device that converts AC to DC and reduces harmonic current flowing in an AC power supply to improve the power factor, and an apparatus using the DC power supply.

  Conventionally, in a DC power supply device of up to about several kW output, one or two switches are used, and the harmonic current of the AC power supply is generated by operating the switch once or several times in a half cycle of the AC power supply. A method of reducing AC power and improving power factor and converting AC to a target DC voltage has been adopted.

  For example, as a conventional single-phase input DC power supply device, a bridge rectifier circuit formed of four diodes for full-wave rectification of AC from an AC power supply, a smoothing capacitor connected to a DC output terminal of the bridge rectifier circuit, A reactor connected between the AC power source and the AC input end of the bridge rectifier circuit, a switch connected via a capacitor between the AC input end and the DC output end of the bridge rectifier circuit, and AC Some include zero-cross detection means for detecting the zero point of the voltage of the power supply, switch drive signal generation means for generating a drive signal for the switch based on the output of the zero-cross detection means, and switch drive means for driving the switch (for example, , See Patent Document 1).

  Hereinafter, a conventional DC power supply device will be described with reference to the drawings. FIG. 6 shows a configuration of a DC power supply device for an inverter air conditioner described in FIG. The DC power supply device for an inverter air conditioner shown in FIG. 6 includes a bridge rectifier circuit 6 formed of four diodes 2 to 5 and an AC power supply 1. A reactor 8 is connected between the AC power source 1 and the AC input terminal of the bridge rectifier circuit 6, and a capacitor 10 is connected between the AC input terminal and DC output terminal of the bridge rectifier circuit via a switch 9.

  A smoothing capacitor 7 is connected between the positive DC output terminal 6d and the negative DC output terminal 6c of the bridge rectifier circuit 6. The smoothing capacitor 7 can make the direct current of drastic change obtained by the bridge rectifier circuit 6 a smooth direct current.

  Further, there are provided zero-cross detection means 13 for detecting the zero-cross point of the voltage of the AC power supply 1, switch drive signal generation means 14 for generating a drive signal for the switch 9 based on the output of the zero-cross detection means 13, and switch drive means 15. is doing.

  In the switch drive signal generation means 14, based on the zero cross timing signal detected by the zero cross detection means 13, the drive delay time of the switch 9 from the zero cross timing signal so that the target value of the DC voltage matches the detected value of the DC voltage. And the drive time is calculated, and a drive signal is sent to the switch drive means 15.

  Next, the behavior of the voltage and current of each part will be described with reference to FIGS. Here, FIGS. 7 and 8 show operations during a half cycle in which the power source voltage Vi of the AC power source 1 is positive, and FIGS. 9 and 10 show operations during a half cycle in which the power source voltage Vi is negative. FIG. 11 shows a conventional power source voltage Vi and a reactor current IL flowing through the reactor 8, a capacitor current Ic and a capacitor voltage Vc flowing through the capacitor 10, a driving output Vg of the switch driving means 15 and a DC voltage Vdc. It is a voltage-current waveform diagram of a DC power supply device.

FIG. 7 shows a state in which the switch 9 is turned on by the drive output Vg from the switch drive means 15 after the drive delay time has elapsed from the voltage zero cross point. The arrows in FIG. 7 indicate the current flow at that time. (Hereinafter, the flow of current is also indicated by arrows in FIGS. 8 to 10.) Charging of the capacitor 10 is started via the reactor 8 by the conduction of the switch 9, and the capacitor current Ic starts to flow. Then, the drive output Vg is stopped so that the switch 9 is opened after the drive time has elapsed.

  FIG. 8 shows the state after the drive time has elapsed, and the reactor 8 releases the energy stored by the reactor current IL when the switch 9 is opened, so that a difference voltage between the power supply voltage Vi and the DC voltage Vdc is generated. Then, a current is supplied to charge the smoothing capacitor 7.

  Next, an operation in which the power supply voltage Vi is a negative half cycle will be described. FIG. 9 shows a state in which the switch 9 is turned on by the drive output Vg after the drive delay time from the zero cross of the power supply voltage Vi has elapsed. At this time, since the capacitor 10 is charged to a voltage close to the DC voltage Vdc, the capacitor 10 flows a capacitor current Ic for discharging. Then, the switch 9 is opened by stopping the drive output Vg after the drive time has elapsed. FIG. 10 shows a state in which the switch 9 is opened after the drive time has elapsed.

  In FIG. 10, the reactor 8 releases the energy accumulated by the reactor current IL that was flowing when the switch 9 was opened, so that a voltage difference between the power supply voltage Vi and the DC voltage Vdc is generated to charge the smoothing capacitor 7. When the reactor current IL stops flowing, the initial state before the switch 9 is turned on is restored.

  Through the series of operations described above, in the present embodiment, the flow angle of the reactor current IL can be greatly widened, and the harmonic current can be reduced and the power factor can be improved as the reactor current IL approaches a sine wave.

  Further, for example, as a conventional three-phase input DC power supply device, there is a DC power supply device described in FIG. 1 of Patent Document 2 (for example, see Patent Document 2).

  This is shown in FIG. 12, and the outline thereof will be described below. In this three-phase input DC power supply, reactors 8u, 8v, and 8w are respectively connected between a three-phase AC power supply 21 and each of the AC input terminals of a three-phase bridge rectifier circuit 22 composed of six diodes, and a switch 9u. , 9v, 9w and capacitors 10u, 10v, 10w connected in series are connected between the AC input end and the DC output end of each phase of the three-phase bridge rectifier circuit 22.

  The switches 9u, 9v, 9w are driven for a predetermined time by the switch control means 16 for controlling the switch drive based on the zero cross signal obtained from the phase voltage zero cross detection means 29 for detecting the zero cross point of each phase voltage. Thus, the capacitors 10u, 10v, and 10w are controlled to be alternately charged and discharged at commercial frequencies.

By operating in this way, each phase current can be raised from near the voltage zero cross of the phase voltage, and the input current waveform can be brought close to a sine wave by the action of the reactors 9u, 9v, 9w, and the power factor Can be improved and harmonics can be reduced.
JP 2003-106616 A JP 2006-121890 A

The conventional DC power supply device is designed to reduce the harmonic current under a constant AC power supply voltage and maintain the output voltage at the DC voltage target value for both a single-phase input and a three-phase input. The operation of the switch is controlled.

  However, the AC power supply voltage is not always constant, and when the AC power supply voltage decreases or when the AC power supply voltage is constantly being used at the consumer with a voltage value lower than the rated voltage. In order to maintain the output voltage, the conduction period of the switch increases, and the ripple current flowing in the capacitor increases.

  On the other hand, in the DC power supply device, the reactor and the capacitor are the parts with the largest volume, and the cost ratio is generally large as a single part. However, since it is necessary to design the capacitor ripple current with a margin as described above, this causes an increase in the volume and cost of the entire device.

  In order to solve the above-described conventional problems, the DC power supply device of the present invention detects the AC power supply voltage, thereby reducing the target DC voltage in accordance with the decrease in the AC power supply voltage value, and the maximum value of the ripple current flowing in the capacitor. It is comprised so that may be reduced.

  The direct current power supply device of the present invention can prevent an increase in ripple current flowing in the capacitor even when the voltage of the alternating current power supply decreases, so that it is possible to design an optimum capacitor characteristic, and to reduce the volume and cost of the capacitor. As a result, the entire DC power supply device can be reduced in size and cost.

  The first invention is an AC power supply, a bridge rectifier circuit formed of four diodes for full-wave rectification of AC, a smoothing capacitor for smoothing the output of the bridge rectifier circuit, and an AC power supply and a bridge rectifier circuit. A reactor connected between one of the AC input terminals, a switch connected via a capacitor between the AC input terminal of the bridge rectifier circuit and one of the DC output terminals, and the voltage of the AC power supply Zero cross detection means for detecting the zero point, DC voltage detection means for detecting the output voltage, AC voltage estimation means for estimating the value of the AC power supply voltage from the output voltage at start-up, and a target voltage based on the estimated voltage value And a switch control means for controlling the drive of the switch, and the output voltage is changed according to the AC power supply voltage. It can limit the ripple current flowing to the capacitor whereby it is possible to reduce the size and cost of the entire device by the possible optimal design of the capacitor characteristics.

  The second invention is characterized in that the target voltage is set to a value uniquely determined according to the AC power supply voltage value only when the voltage of the AC power supply falls below a predetermined value in the first invention. The power supply device can stabilize the DC output voltage while limiting the ripple current of the capacitor.

The third invention is an AC power source, a bridge rectifier circuit formed of four diodes for full-wave rectification of AC, a smoothing capacitor for smoothing the output of the bridge rectifier circuit, an AC power source and a bridge rectifier circuit. A reactor connected between one of the AC input terminals, a switch connected via a capacitor between the AC input terminal of the bridge rectifier circuit and one of the DC output terminals, and the voltage of the AC power supply AC voltage detecting means for detecting, zero cross detecting means for detecting the zero point of the AC power supply, DC voltage detecting means for detecting the output voltage, and determining the target voltage based on the detected voltage value to drive the switch And a switch control means for controlling the output power supply according to the voltage value detected by the AC voltage detection means not only during startup but also during operation. The by changing can limit the ripple current flowing through the capacitor, it is possible to reduce the size and cost of the entire device by the possible optimal design of the capacitor characteristics.

  The fourth invention is characterized in that the target voltage is set to a value uniquely determined according to the AC power supply voltage value only when the voltage of the AC power supply falls below a predetermined value in the third invention. The power supply device can stabilize the DC output voltage while limiting the ripple current of the capacitor.

  A fifth invention is a three-phase AC power source, a three-phase bridge rectifier circuit formed of six diodes, a smoothing capacitor connected to a DC output terminal of the three-phase bridge rectifier circuit, a three-phase AC power source and a three-phase AC power source. A reactor connected between the AC input terminals of each phase of the phase bridge rectifier circuit, and a capacitor connected via a switch between the AC input terminals and DC output terminals of each phase of the three-phase bridge rectifier circuit; Phase voltage zero cross detection means for detecting the voltage zero cross point of each phase of the three-phase AC power supply, DC voltage detection means for detecting the output voltage, and AC voltage estimation for estimating the value of the AC power supply voltage from the output voltage at start-up And a switch control means for determining the target voltage based on the voltage value estimated by the AC voltage estimation means and controlling the drive of the switch. Output voltage can be limited ripple current flowing to the capacitor by changing, it is possible to reduce the size and cost of the entire device by the possible optimal design of the capacitor characteristics in accordance with.

  A sixth invention is a DC power supply device according to the fifth invention, wherein the switch control means operates to reduce the target voltage when the estimated three-phase AC power supply voltage falls below a predetermined value. The DC output voltage can be stabilized while limiting the ripple current of the capacitor.

  The seventh invention is a three-phase AC power source, a three-phase bridge rectifier circuit formed of six diodes, a smoothing capacitor connected to a DC output terminal of the three-phase bridge rectifier circuit, a three-phase AC power source and a three-phase AC power source. A reactor connected between the AC input terminals of each phase of the phase bridge rectifier circuit, and a capacitor connected via a switch between the AC input terminals and DC output terminals of each phase of the three-phase bridge rectifier circuit; AC voltage detection means for detecting the voltage of the three-phase AC power supply, phase voltage zero cross detection means for detecting the voltage zero cross point of each phase of the three-phase AC power supply, DC voltage detection means for detecting the output voltage, and AC voltage A DC power supply device characterized by comprising a switch control means for determining a target voltage according to a voltage value detected by the detection means and controlling the drive of the switch. By changing the output voltage according to the voltage value detected by the pressure detection means, the ripple current flowing in the capacitor can be limited, and the optimum design of the capacitor characteristics can be achieved, thereby reducing the size and cost of the entire device. Can be achieved.

  An eighth invention is a DC power supply device according to the seventh invention, wherein the switch control means operates to reduce the target voltage when the voltage value detected by the AC voltage detection means falls below a predetermined value. In addition, the DC output voltage can be stabilized while limiting the ripple current of the capacitor.

(Embodiment 1)
FIG. 1 is a block diagram of a DC power supply device according to a first embodiment of the present invention. In FIG. 1, the basic configuration for supplying the DC voltage to the load 18 after the AC power source 1 is rectified by the bridge rectifier circuit 6 and then smoothed to DC by the smoothing capacitor 7 is the same as the conventional example shown in FIG. Further, a switch 9 is connected between the AC input terminal and the negative output terminal of the bridge rectifier circuit 6 via the capacitor 10, and the on / off time of the switch 9 is adjusted by the switch control means 16 so that the load 18 can be applied to the load 18 with a high input power factor. The operation capable of supplying DC power is the same as that of the prior art.

  However, in the present embodiment, the AC power supply voltage is calculated from the DC voltage detection means 17 for detecting the DC voltage and the output voltage detected by the DC voltage detection means 17 when the DC power supply device is activated, compared to the conventional example. An AC power supply voltage estimation means 19 for estimation is added, and the functions of the switch drive signal generation means 14 and the switch drive means 15 in FIG. 6 are included in the switch control means 16.

  Further, the present embodiment is different from the prior art in that the switch control means 16 controls the drive time of the switch 9 so that the output voltage becomes equal to the target voltage.

  Next, the effect of changing the target voltage will be described with reference to FIGS. FIG. 2 is a ripple current characteristic diagram showing changes in ripple current for each target voltage when the AC power supply voltage changes. In FIG. 1, the reactor 8 in FIG. The characteristic when electric power is 3 kW is shown.

  When the AC power supply voltage decreases, the ripple current flowing in the capacitor 7 increases as the conduction time of the switch 9 increases to maintain the output voltage. However, there is an overall current difference of slightly over 1 A between the case where the target voltage is 312V and the case where the target voltage is 300V, and the ripple current can be reduced by lowering the target voltage.

  This embodiment utilizes such ripple current characteristics, and lowers the target voltage as the power supply voltage decreases, thereby reducing the ripple current of the capacitor 7. As a result, the capacitor 7 can be optimally designed, and as a result, the entire device can be reduced in size and cost.

  In this embodiment, the target voltage is determined by estimating the AC power supply voltage. However, as shown in FIG. 3, the AC power supply voltage may be directly detected using the AC voltage detection means 20. .

  In this embodiment, the target voltage may be changed whenever the AC power supply voltage changes. However, the target voltage is kept constant with respect to a decrease in the AC power supply voltage within a range where the ripple current is lower than the allowable value. The target voltage may be lowered only when the AC power supply voltage drop exceeds the allowable value. By doing so, it becomes possible to stabilize the output voltage.

(Embodiment 2)
FIG. 4 is a block diagram of a DC power supply device according to the second embodiment of the present invention. 4, in contrast to the conventional three-phase input DC power supply device shown in FIG. 12, the DC voltage detection means 17 for detecting a DC voltage and the DC voltage detection means 17 detected when the DC power supply device is activated. AC power supply voltage estimation means 19 for estimating the AC power supply voltage from the output voltage thus added is added.

  In the present embodiment, the switch control unit 16 controls the drive time of the switches 9u, 9v, 9w so that the output voltage becomes equal to the target voltage. However, the switches 9u, 9v are based on the zero cross of the phase voltage. The effect of reducing the harmonic current while taking the drive timing of 9w and increasing the input power factor is the same as that of the first embodiment.

If the target voltage is not changed also in the present embodiment, the ripple current flowing in the capacitors 7u, 7v, 7w as shown in the first embodiment maintains the output voltage when the AC power supply voltage decreases, so that the switch 9u , 9v, 9w increase with increasing conduction time.

  Therefore, also in the present embodiment, the ripple current is reduced by lowering the target voltage when the AC input voltage is lowered using the ripple current characteristics. Therefore, in this embodiment, the ripple current of the capacitors 7u, 7v, and 7w can be reduced even in a DC power supply device in which the input power supply is a three-phase AC power supply. As a result, the capacitors 7u, 7v, and 7w can be optimally designed, and as a result, the entire apparatus can be reduced in size and cost.

  In this embodiment, the target voltage is determined by estimating the AC power supply voltage. However, the AC power supply voltage may be directly detected using the AC voltage detection means 20 as shown in FIG.

  Further, in the present embodiment, the target voltage may be changed whenever the AC power supply voltage changes. However, the target voltage is set to decrease the AC power supply voltage within a range where the ripple current is lower than the allowable value. The target voltage may be lowered only when the AC power supply voltage drop exceeds the allowable value and the ripple current exceeds the allowable value. By doing so, it becomes possible to stabilize the output voltage.

  As described above, the DC power supply according to the present invention is capable of reducing the maximum ripple current of the capacitor in the DC power supply that achieves harmonic current reduction and power factor improvement. The present invention can be applied to an input stage circuit of a home appliance using a stage circuit, a compressor such as an air conditioner or a refrigerator.

1 is a block diagram of a DC power supply device according to Embodiment 1 of the present invention. Capacitor ripple current characteristics The block diagram at the time of changing the alternating voltage detection method of Embodiment 1 of this invention Block diagram of DC power supply apparatus according to Embodiment 2 of the present invention The block diagram at the time of changing the alternating voltage detection method of Embodiment 2 of this invention Block diagram of a conventional single-phase input DC power supply Operation explanatory diagram at the time of switch-on in the positive half cycle of the conventional single-phase input DC power supply device Operation explanatory diagram at the time of switch-off in the positive half cycle of the conventional single-phase input DC power supply device Operation explanation diagram at the time of switch-on in the negative half cycle of the conventional single-phase input DC power supply Operation explanatory diagram at the time of switch-off in the negative half cycle of the conventional single-phase input DC power supply device Voltage and current waveform diagram of conventional single-phase input DC power supply Block diagram of a conventional three-phase input DC power supply

Explanation of symbols

1 AC power source 2, 3, 4, 5, 23, 24, 25, 26, 27, 28 Diode 6 Bridge rectifier circuit 7 Smoothing capacitor 8, 8u, 8v, 8w Reactor 9, 9u, 9v, 9w Switch 10, 10u, 10v, 10w Capacitor 13 Zero cross detection means 16 Switch control means 17 DC voltage detection means 18 Load 19 AC voltage estimation means 20 AC voltage detection means 21 Three-phase AC power supply 22 Three-phase bridge rectifier circuit 29 Phase voltage detection means

Claims (9)

An AC power supply, a bridge rectifier circuit formed by four diodes for full-wave rectification of AC from the AC power supply, a smoothing capacitor for smoothing the output of the bridge rectifier circuit, the AC power supply, and the bridge rectifier circuit A reactor connected between one of the two AC input terminals, a switch connected via a capacitor between the AC input terminal of the bridge rectifier circuit and one of the DC output terminals, and the AC Zero cross detection means for detecting a zero point of the voltage of the power supply, DC voltage detection means for detecting the output voltage, AC voltage estimation means for estimating the value of the AC power supply voltage from the output voltage at the start, and the AC voltage estimation means And a switch control means for determining the target voltage based on the voltage value estimated in step 1 and controlling the drive of the switch. 2. The DC power supply apparatus according to claim 1, wherein the switch control unit operates to reduce a target voltage when a voltage value estimated by the AC voltage estimation unit falls below a predetermined value. An AC power supply, a bridge rectifier circuit formed by four diodes for full-wave rectification of AC from the AC power supply, a smoothing capacitor for smoothing the output of the bridge rectifier circuit, the AC power supply, and the bridge rectifier circuit A reactor connected between one of the two AC input terminals, a switch connected via a capacitor between the AC input terminal of the bridge rectifier circuit and one of the DC output terminals, and the AC Based on the voltage value detected by the AC voltage detecting means for detecting the voltage of the power supply, the zero cross detecting means for detecting the zero point of the AC power supply, the DC voltage detecting means for detecting the output voltage, and the AC voltage detecting means. And a switch control means for controlling the drive of the switch by determining a target voltage. 4. The DC power supply apparatus according to claim 3, wherein the switch control means operates to reduce a target output voltage when a voltage value detected by the AC voltage detection means falls below a predetermined value. A three-phase AC power source, a three-phase bridge rectifier circuit formed of six diodes, a smoothing capacitor connected to a DC output terminal of the three-phase bridge rectifier circuit, the three-phase AC power source and the three-phase bridge rectifier A reactor connected between an AC input terminal of each phase of the circuit, a capacitor connected via a switch between an AC input terminal and a DC output terminal of each phase of the three-phase bridge rectifier circuit, and Phase voltage zero-cross detection means for detecting the voltage zero-cross point of each phase of the three-phase AC power supply, DC voltage detection means for detecting the output voltage, and AC voltage for estimating the voltage of the three-phase AC power supply from the output voltage at start-up A DC power supply apparatus comprising: an estimation unit; and a switch control unit that determines a target voltage based on a voltage value estimated by the AC voltage estimation unit and controls driving of the switch. 6. The DC power supply device according to claim 5, wherein the switch control means operates to reduce a target voltage when a voltage value estimated by the AC voltage estimation means falls below a predetermined value. A three-phase AC power source, a three-phase bridge rectifier circuit formed of six diodes, a smoothing capacitor connected to a DC output terminal of the three-phase bridge rectifier circuit, the three-phase AC power source and the three-phase bridge rectifier A reactor connected between an AC input terminal of each phase of the circuit, a capacitor connected via a switch between an AC input terminal and a DC output terminal of each phase of the three-phase bridge rectifier circuit, and AC voltage detection means for detecting the voltage of the three-phase AC power supply, phase voltage zero-cross detection means for detecting the voltage zero-cross point of each phase of the three-phase AC power supply, DC voltage detection means for detecting the output voltage, and the AC A DC power supply apparatus comprising: a switch control unit that determines a target voltage based on a voltage value detected by the voltage detection unit and controls driving of the switch. 8. The DC power supply device according to claim 7, wherein the switch control unit operates to reduce a target voltage when a voltage value detected by the AC voltage detection unit falls below a predetermined value. The apparatus provided with the direct-current power supply device of any one of Claims 1-8.

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