JP2016101070A - Step-down chopper circuit and power supply device for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a step-down chopper circuit capable of reducing a loss of a switch and a diode.SOLUTION: In a step-down chopper circuit 12 arranged with a switch, a reflux diode, and a reactor in this order, first and second switches TR1 and TR2 are provided in parallel on a power supply wire La as the switch, and first and second reactor L1 and L2 are provided in parallel on a power supply wire Lb as the reactor. An auxiliary capacitor C2 is connected between the power supply wires La and Lb between the switches TR1 and TR2, and the reflux diode DR 1 is connected between the power supply wires La and Lb between the reactors L1 and L2. As a chopper action, the second switch TR2 is turned on/off with a prescribed-time delay to the first switch TR1, thereby generating the resonance action of the auxiliary capacitor C2 and the first reactor L1. A switching loss or a recovery loss when the first and second switches TR1 and TR2 and the reflux diode DR1 are turned on/off are reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a step-down chopper circuit and a welding power source apparatus including the circuit.

  In a welding power supply apparatus that can be used with different input voltages, a step-down chopper circuit for adjusting an internal voltage in accordance with the input voltage is used. The step-down chopper circuit is built in between the rectifier circuit and the inverter circuit of the welding power source device including, for example, a rectifier circuit, an inverter circuit, and a welding transformer in order from the input side, and an appropriate voltage is applied to the inverter circuit. Step-down operation is performed to adjust within the range.

  As a circuit configuration of the step-down chopper circuit, for example, the one shown in Patent Document 1 is generally known. Incidentally, the step-down chopper circuit disclosed in Patent Document 1 is incorporated in a lighting device. The step-down chopper circuit is connected to a switch for operating a chopper connected on a power supply line on one side, a free wheel diode connected between power supply lines on the subsequent stage of the switch, and a power supply line on one side of the subsequent stage of the diode. And an output voltage that is stepped down by the chopper operation of the switch.

JP 2012-222322 A (see FIG. 2)

  Incidentally, in the general step-down chopper circuit disclosed in Patent Document 1, the switching loss during the chopper operation of the switch is large, which causes heat generation. Therefore, realization of so-called soft switching has been studied in order to reduce the switching loss of the switch. At the same time, it has been studied to reduce the recovery loss of the freewheeling diode.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a step-down chopper circuit capable of reducing the loss of a switch and a diode, and a welding power supply apparatus including the circuit. It is in.

  A step-down chopper circuit that solves the above problem includes a switch connected on a power supply line, a freewheeling diode connected between power supply lines subsequent to the switch, and a reactor connected on a power supply line subsequent to the diode. A step-down chopper circuit that performs a step-down operation by the chopper operation of the switch, wherein the first and second switches are juxtaposed on the power line as the switch, and the first and second reactors are the reactors. Are arranged in parallel on the power supply line, an auxiliary capacitor is provided between the power supply lines between the first and second switches, and the free wheel diode is further provided between the power supply lines between the first and second reactors. The second switch is turned on and off with a delay with respect to the first switch, and the first and second switches and the reflux diode are connected. It said auxiliary capacitor and configured to perform a resonance operation of the first reactor causes a loss reduction effect at the time off of.

  According to this configuration, in the step-down chopper circuit arranged in the order of the switch, the freewheeling diode, and the reactor, the first and second switches are juxtaposed on the power supply line as switches, and the first and second reactors are on the power supply line as reactors. In addition to being arranged in parallel, an auxiliary capacitor is connected between the power lines between the first and second switches, and a free wheeling diode is connected between the power lines between the first and second reactors. Then, the second switch is turned on / off with a delay with respect to the first switch to cause the resonance operation of the auxiliary capacitor and the first reactor, and the switching loss and recovery loss when the first and second switches and the free wheel diode are turned on / off. Is reduced.

  In the step-down chopper circuit, the first switch and the second switch are first turned on, and then the second switch is turned on after the auxiliary capacitor is completely charged by turning on the first switch. Next, it is preferable that the first switch is turned off while the auxiliary capacitor is charged, and then the second switch is turned off after the auxiliary capacitor is completely discharged by turning off the first switch.

  According to this configuration, the first switch is turned on, and then the second switch is turned on after the auxiliary capacitor is fully charged by turning on the first switch. Then, the first switch is turned off in the charged state of the auxiliary capacitor, and then the first switch is turned off. The second switch is turned off after the auxiliary capacitor is completely discharged. That is, an appropriate resonance operation is performed by the auxiliary capacitor and the first reactor in order to reduce the loss of the switch and the diode.

  In the step-down chopper circuit, it is preferable that the first and second reactors are configured by causing one reactor with a middle tap to partially function as each reactor.

  According to this configuration, since the first and second reactors are configured by partially functioning one reactor with an intermediate tap as each reactor, the configuration of these reactors can be simply realized.

Further, a welding power supply device that solves the above-described problems is configured by arranging the step-down chopper circuit in the preceding stage of an inverter circuit that supplies high-frequency AC power to a welding transformer.
According to this configuration, since the step-down chopper circuit capable of reducing the loss of the switch and the diode is provided, the efficiency of the welding power supply device can be expected to be improved.

  According to the step-down chopper circuit and the welding power supply device of the present invention, it is possible to reduce the loss of the switch and the diode.

It is a block diagram of the power supply apparatus for welding provided with the pressure | voltage fall chopper circuit of one Embodiment. It is a wave form diagram which shows the change of the voltage and current of each place of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode1] of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode2] of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode3] of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode4] of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode5] of a step-down chopper circuit. It is a circuit diagram for demonstrating operation | movement [mode6] of a step-down chopper circuit. It is a circuit diagram which shows a part of step-down chopper circuit of another example.

Hereinafter, an embodiment of a power supply device including a step-down chopper circuit will be described.
As shown in FIG. 1, a welding power supply device 10 as a power supply device includes a rectifier circuit 11, a step-down chopper circuit 12, an inverter circuit 13, and a welding transformer 14 in this order from the input side. Appropriate output power is generated from the power to the welding load 15. The welding power supply apparatus 10 includes a step-down chopper circuit 12 so that it can be used even with different input voltages. The step-down chopper circuit 12 performs a step-down operation so as to adjust the voltage applied to the inverter circuit 13 in the subsequent stage within an appropriate range. I do. Details of the step-down chopper circuit 12 will be described later.

  Incidentally, the rectifier circuit 11 is a full-wave rectifier circuit made of, for example, a diode bridge, and converts the input power of three-phase alternating current into direct current. The inverter circuit 13 is a full bridge circuit using, for example, an IGBT (semiconductor switch), and converts DC power input from the rectifier circuit 11 through the step-down chopper circuit 12 into high-frequency AC power. The welding transformer 14 receives high-frequency AC power from the inverter circuit 13 on the primary side, and performs voltage conversion for generating DC output power suitable for the welding load 15 on the secondary side.

  The step-down chopper circuit 12 includes first and second switches TR1 and TR2, a freewheeling diode DR1, first and second reactors L1 and L2, smoothing capacitors C1 and C3, and an auxiliary capacitor C2.

  As a connection mode of the step-down chopper circuit 12, for a pair of power supply lines La and Lb between the output terminal of the rectifier circuit 11 and the input terminal of the inverter circuit 13, a smoothing capacitor C1 is first connected between the power supply lines La and Lb. ing. A first switch TR1 made of, for example, IGBT is connected to the power supply line La at the subsequent stage of the smoothing capacitor C1. An auxiliary capacitor C2 is connected between the power supply lines La and Lb at the subsequent stage of the first switch TR1. A second switch TR2 made of, for example, IGBT is connected to the power supply line La subsequent to the auxiliary capacitor C2, and a first reactor L1 is connected to the power supply line Lb subsequent to the auxiliary capacitor C2. A free-wheeling diode DR1 is connected between the second switch TR2 and the power supply lines La and Lb at the subsequent stage of the first reactor L1, in which case the anode side is connected to the power supply line Lb and the cathode side is connected to the power supply line La. A second reactor L2 is connected to the power supply line Lb at the subsequent stage of the freewheeling diode DR1. A smoothing capacitor C3 is connected between the power supply lines La and Lb at the subsequent stage of the second reactor L2.

  The step-down chopper circuit 12 includes voltage sensors 21 and 22 on the input side and the output side, respectively. The voltage sensor 21 detects the input voltage of the step-down chopper circuit 12, the voltage sensor 22 detects the output voltage of the step-down chopper circuit 12, and the detection signals from the voltage sensors 21 and 22 are input to the chopper control unit 25. The chopper controller 25 recognizes the input / output voltage of the step-down chopper circuit 12 based on the detection signals from the voltage sensors 21 and 22.

  The chopper control unit 25 generates a control signal to be output to the control terminals (gate terminals) of the first and second switches TR1 and TR2, and controls the switches TR1 and TR2 by each control signal. Such a chopper control unit 25 recognizes which voltage is the input voltage to the welding power supply device 10 from the input voltage of the step-down chopper circuit 12, and outputs the output voltage of the step-down chopper circuit 12 (to the inverter circuit 13 in the subsequent stage). Adjustment of the chopper operation of the first and second switches TR1 and TR2 (adjustment of on-time) is performed so that (applied voltage) is within an appropriate range. That is, the welding power supply device 10 of the present embodiment is configured as a so-called different-voltage power supply device that can handle different input voltages.

  Incidentally, the chopper control unit 25 is either provided individually for controlling the step-down chopper circuit 12 or provided integrally with a control circuit (not shown) for controlling the whole welding power supply device 10. May be.

  Next, the operation of the step-down chopper circuit 12 (control mode of the chopper control unit 25) will be described with reference to voltage / current waveform diagrams in FIG. 2 and operation explanatory diagrams of each mode (mode) in FIGS. To do. The waveform diagram of FIG. 2 is a waveform for one cycle of the chopper operation (chopper control).

In FIG. 2, the waveforms of “TR1” and “TR2” indicate the on / off states of the first and second switches TR1 and TR2. The waveform “V _C2 ” indicates the voltage across the terminal of the auxiliary capacitor C2. _{"V TR1"} waveform _{"V TR2"} indicates the first and second switch TR1, between TR2 of the terminal voltage, _{"I TR1"} is a waveform of the _{"I TR2"} current flowing through the first and second switches TR1, TR2 Indicates. The waveform of “V _DR1 ” indicates the voltage between the terminals of the freewheeling diode DR1, and the waveform of “ _IDR1 ” indicates the current flowing through the freewheeling diode DR1. The waveform of “V _L1 ” indicates the voltage between the terminals of the first reactor L1.

  In addition, regarding the capacitors C1 and C2 and the reactors L1 and L2 that are related to each other in the operation of the step-down chopper circuit 12, in this embodiment, the capacity of the auxiliary capacitor C2 is smaller than the capacity of the smoothing capacitor C1, and the first reactor L1 The inductance of the second reactor L2 is set to be larger than the inductance (C1> C2, L1 <L2).

[Mode1] shown in FIG. 3 is a mode based on turn-on of the first switch TR1.
As for the state of the step-down chopper circuit 12, the second switch TR2 is turned off, and the return current due to the electromagnetic energy accumulated in the second reactor L2 in the previous cycle flows on the return diode DR1 (arrow a). Note that no reflux current is generated at the time of startup.

  In this state, when the first switch TR1 is turned on, that is, the first switch TR1 is turned on before the second switch TR2, a charging current (arrow b) toward the auxiliary capacitor C2 is generated. Although the ON state of the first switch TR1 is hard switching, only the auxiliary capacitor C2 having a small capacity is charged, so that the switching loss when the first switch TR1 is ON is small.

[Mode2] shown in FIG. 4 is a mode based on turn-on of the second switch TR2.
When the second switch TR2 is turned on, the power supply line La in the step-down chopper circuit 12 becomes conductive, and currents (c and d arrows) are generated on the power supply lines La and Lb.

  When the second switch TR2 is turned on, the rising of the current is gentle due to the action of the first reactor L1, so that the second switch TR2 is turned on by zero current switching (ZCS). Further, since a counter electromotive force is generated at the beginning of the current flow to the first reactor L1, an instantaneous moment when the second switch TR2 is turned on by the counter electromotive voltage (e arrow) and the charging voltage (f arrow) at this time is generated. Both-end voltage is also zero voltage. That is, the ON state of the second switch TR2 is zero voltage switching (ZVS), and the switching loss when it is ON is extremely small.

  In addition, the return current (arrow a) flowing through the return diode DR1 continues to flow due to the second inductor L2 having a large inductance, but the return current gradually decreases and the current (c) generated by turning on the second switch TR2 gradually decreases. Arrow) increases.

[Mode3] illustrated in FIG. 5 is a recovery (reverse recovery) period of the freewheeling diode DR1.
The return period of the return diode DR1 ends, and the recovery period starts. In this recovery period, a reverse voltage is applied to the freewheeling diode DR1 to generate a recovery current (arrow g). However, a part of the reverse voltage is canceled out by the back electromotive force of the first reactor L1, and the recovery current is reduced. It is suppressed. That is, the recovery loss of the freewheeling diode DR1 is also kept small.

[Mode4] illustrated in FIG. 6 is a mode in which power (electric power) is transmitted from the input side to the output side.
This is a power (power) transmission period in which the recovery period of the freewheeling diode DR1 ends and the transient period of the circuit 12 ends, and only currents (c and d arrows) on the power supply lines La and Lb are generated.

  Although there is a concern that the conduction loss is doubled by arranging the first and second switches TR1 and TR2 in parallel, the effect of reducing the switching loss of the first and second switches TR1 and TR2 The effect of reducing the recovery loss of the freewheeling diode DR1 is sufficiently large.

[Mode5] shown in FIG. 7 is a mode in which the first switch TR1 is turned off and the free wheeling diode DR1 is turned on.
First, the first switch TR1 is turned off. Since there is no voltage difference between the smoothing capacitor C1 and the auxiliary capacitor C2 when the first switch TR1 is turned off, the first switch TR1 is turned off by zero voltage switching (ZVS). That is, the switching loss when the first switch TR1 is off is also extremely small.

  After the first switch TR1 is turned off, the output current continues to flow with the current (h arrow) generated by the current from the auxiliary capacitor C2 and the accumulated energy of the first and second reactors L1 and L2. In this case, since the auxiliary capacitor C2 and the first reactor L1 are set to have a small constant, the current related to them decreases immediately. On the other hand, the second reactor L2 having a large constant tends to maintain the output current because the stored energy is large, but the current hardly flows to the second switch TR2 due to the presence of the first reactor L1, and the free wheel diode DR1. Flows over (i arrow).

  Further, since the back electromotive force is generated in the first reactor L1 due to the current generated in the second reactor L2 when the free wheel diode DR1 is turned on, when the free wheel diode DR1 is turned on by the back electromotive voltage (j arrow) at this time. The both-ends voltage becomes zero voltage, and ON of the free wheel diode DR1 is zero voltage switching (ZVS).

[Mode 6] shown in FIG. 8 is a reflux mode in which the second switch TR2 is turned off and only a reflux current is generated.
When all of the current has commutated to the freewheeling diode DR1, the second switch TR2 is turned off. That is, since the OFF of the second switch TR2 is zero voltage switching (ZVS) and zero current switching (ZCS), the switching loss when the second switch TR2 is OFF is extremely small.

  After the second switch TR2 is turned off, a current (arrow a) generated by the energy stored in the second reactor L2 continues to flow through the freewheeling diode DR1. Then, the output current is maintained by the second reactor until the first switch TR1 is turned on [mode1]. As the chopper operation (chopper control), [mode1] to [mode6] indicating one cycle described above are repeated, and when increasing or decreasing the output, the on period from [mode1] to [mode5] is the first. It is long and short in the cycle.

  As described above, the step-down chopper circuit 12 of the present embodiment performs the above-described control using the two switches (switches TR1 and TR2), the auxiliary capacitor C2, and the two reactors (reactors L1 and L2). The configuration can reduce both the switching loss of TR2 and the recovery loss of the return diode DR1.

Next, characteristic effects of the present embodiment will be described.
(1) In the step-down chopper circuit 12 of the present embodiment, the first and second switches TR1 and TR2 are arranged in parallel on the power supply line La as switches, and the first and second reactors L1 and L2 are arranged on the power supply line Lb as reactors. The auxiliary capacitor C2 is connected between the power supply lines La and Lb between the switches TR1 and TR2, and the freewheeling diode DR1 is connected between the power supply lines La and Lb between the reactors L1 and L2. Then, the second switch TR2 is turned on and off with a predetermined time delay with respect to the first switch TR1, thereby causing the resonance operation of the auxiliary capacitor C2 and the first reactor L1 as shown in the above modes. Switching loss and recovery loss when the switches TR1 and TR2 and the freewheeling diode DR1 are turned on and off are reduced. That is, the loss of the step-down chopper circuit 12 can be reduced, and the efficiency of the welding power supply device 10 is improved.

  (2) As the chopper operation of the present embodiment, the first switch TR1 is turned on, and then the second switch TR2 is turned on after the charging of the auxiliary capacitor C2 by the first switch TR1 being turned on. The switch TR1 is turned off, and then the second switch TR2 is turned off after the discharge of the auxiliary capacitor C2 is completed by turning off the first switch TR1. That is, an appropriate resonance operation is performed by the auxiliary capacitor C2 and the first reactor L1, and a more reliable loss reduction effect of each of the switches TR1 and TR2 and the diode DR1 can be obtained.

In addition, you may change the said embodiment as follows.
Although the configuration of the first and second reactors L1 and L2 was not particularly mentioned, the first and second reactors L1 and L2 may be used individually, and as shown in FIG. It can also comprise using the reactor Lx with an intermediate tap. That is, the free-wheeling diode DR1 is connected to the intermediate tap of the reactor Lx with the intermediate tap so that one side of the intermediate tap functions as the first reactor L1 and the other side functions as the second reactor L2. In this way, the first and second reactors L1 and L2 can be realized with a simple configuration.

  Although the first and second switches TR1 and TR2 are provided on the power supply line La, they may be provided on the power supply line Lb. Moreover, although the 1st and 2nd reactor L1, L2 was provided in the power wire Lb, you may provide in the power wire La.

  Although IGBTs are used for the first and second switches TR1 and TR2, other semiconductor switches may be used. Further, the return diode DR1 may be a semiconductor switch and may function as a return diode.

  The voltage sensor 21 that detects the input voltage is installed at the input terminal of the step-down chopper circuit 12 and the voltage sensor 22 that detects the output voltage is installed at the output terminal. Detection may be substituted. For example, the aspect which detects the input voltage (alternating current) of the power supply device 10 may be sufficient.

-You may apply to power supply devices other than the power supply apparatus 10 for welding.
Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(A) A power supply device comprising the step-down chopper circuit according to any one of claims 1 to 3.

12 Step-down chopper circuit 13 Inverter circuit 14 Welding transformer La, Lb Power line TR1 1st switch TR2 2nd switch L1 1st reactor L2 2nd reactor Lx Reactor with intermediate tap DR1 Reflux diode C2 Auxiliary capacitor

Claims (4)

A switch connected on a power supply line, a freewheeling diode connected between power supply lines on the subsequent stage of the switch, and a reactor connected on a power supply line on the subsequent stage of the diode, and a step-down operation by a chopper operation of the switch A step-down chopper circuit that performs
The first and second switches are arranged in parallel on the power line as the switch, and the first and second reactors are arranged in parallel on the power line as the reactor, and the first and second switches An auxiliary capacitor is connected between the power lines, and the free wheel diode is connected between the power lines between the first and second reactors.
Resonant operation of the auxiliary capacitor and the first reactor causing the second switch to be turned on / off with a delay with respect to the first switch, and causing a loss reducing action when the first and second switches and the free-wheeling diode are turned on / off A step-down chopper circuit configured to perform The step-down chopper circuit according to claim 1,
The first and second switches are first turned on, then turned on after the auxiliary capacitor is fully charged by turning on the first switch, and then turned on in the charged state of the auxiliary capacitor. A step-down chopper circuit configured to turn off the first switch and then turn off the second switch after the auxiliary capacitor is completely discharged by turning off the first switch. In the step-down chopper circuit according to claim 1 or 2,
The step-down chopper circuit is characterized in that the first and second reactors are configured by causing one reactor with an intermediate tap to partially function as each reactor.   A welding power supply apparatus comprising: a step-down chopper circuit according to any one of claims 1 to 3 disposed in front of an inverter circuit that supplies high-frequency AC power to a welding transformer. .