JP2009296704A - Power supply, and power supply for arc processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply, which ensures charge and discharge of an auxiliary capacitor for use in soft switching control regardless of the load state, and which reduces switching loss or minimizes voltage surge. <P>SOLUTION: A resonance circuit 15 is provided between the middle points N1 and N2 of the bridge arms of an inverter circuit 13 (between the output terminals). The resonance circuit 15 begins resonance operation in advance of turn-off of a switching element S6 for starting discharge of an auxiliary capacitor C1, and causes to produce a resonance current for increasing the output currents from switching elements S1-S4 based on the discharge current of the auxiliary capacitor C1. Consequently, the discharge rate of the auxiliary capacitor C1 is increased and the discharge time of the auxiliary capacitor C1 is shortened. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device having an inverter circuit and a power supply device for arc machining.

  For example, as disclosed in Patent Document 1, a power supply device used for an arc machine or the like is a DC converter that converts a commercial power supply (three-phase AC power supply) into a DC voltage that is rectified by a rectifier circuit and smoothed by a smoothing capacitor. A circuit and an inverter circuit composed of a full bridge circuit of a switching element. The inverter circuit converts the DC voltage from the DC conversion circuit into a predetermined high-frequency AC voltage by alternately switching on and off each switching element for each group. A predetermined high-frequency AC voltage from the inverter circuit is further converted into a DC voltage for arc machining suitable for arc machining such as arc welding or arc cutting.

Further, in the power supply device shown in FIG. 1 and FIG. 16 of Patent Document 1, an auxiliary capacitor is connected between a pair of power supply lines between a smoothing capacitor and an inverter circuit constituting a DC conversion circuit, and a smoothing is performed. An auxiliary switching element is disposed on the power line between the auxiliary capacitor and the auxiliary capacitor. The auxiliary switching element is turned on simultaneously with the switching element of the inverter circuit being turned on, and is turned off before the switching element of the inverter circuit is turned off. By utilizing the charge / discharge operation of the auxiliary capacitor based on the on / off control of the auxiliary switching element, soft switching control for reducing the switching loss in each switching element can be performed. 1 is compatible with a 200 V input AC power supply, and the power supply apparatus of FIG. 16 is compatible with a 400 V input AC power supply.
JP 2003-31408 A

  However, the charging and discharging of the auxiliary capacitor may be incomplete during light load or no load. This incomplete charging / discharging operation of the auxiliary capacitor leads to an increase in switching loss and breakage of the switching element due to the generation of a surge voltage. Therefore, it is desired to solve these problems.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to ensure charging / discharging of the auxiliary capacitor used in soft switching control regardless of the load state, to reduce switching loss and to suppress voltage surge. An object of the present invention is to provide a power supply device and an arc machining power supply device capable of achieving the above.

  In order to solve the above-mentioned problem, the invention described in claim 1 includes a rectifier circuit and a smoothing capacitor connected between a pair of power supply lines on the output side thereof, and a DC voltage obtained by rectifying and smoothing an input AC power supply. A DC converter circuit for converting to a full bridge circuit using a plurality of switching elements, wherein the first set and the second set of switching elements are alternately turned on and off and supplied via the power lines. An inverter circuit that converts a DC voltage into a predetermined AC voltage; and an auxiliary capacitor connected between the power supply lines between the smoothing capacitor and the inverter circuit; and between the smoothing capacitor and the auxiliary capacitor. Auxiliary switching elements, in which auxiliary switching elements that are operated in conjunction with the first and second sets of switching elements of the inverter circuit, are disposed on the power supply line. A switching circuit, and turns off the auxiliary switching element prior to turning off the switching element of the inverter circuit in a charged state of the auxiliary capacitor. A power supply device configured to perform soft switching control to turn off a switching element of an inverter circuit, and is provided between output terminals of the inverter circuit and resonates before the auxiliary switching element is turned off to start discharging of the auxiliary capacitor. The gist of the invention is to provide a resonance circuit that starts operation and generates a resonance current that increases the output current of the switching element of the inverter circuit based on the discharge current of the auxiliary capacitor.

  In the present invention, a resonance circuit is provided between the output terminals of the inverter circuit (between the intermediate points of the bridge arm), and the resonance circuit is before the auxiliary switching element that starts the discharge of the auxiliary capacitor is turned off (at the same time as off or off). In advance, the resonance operation is started, and a resonance current is generated such that the output current of the switching element of the inverter circuit is increased based on the discharge current of the auxiliary capacitor. Thereby, the discharge speed of the auxiliary capacitor is increased, and the discharge time of the auxiliary capacitor is shortened. Therefore, the auxiliary capacitor is discharged quickly in a short time, and the auxiliary capacitor can be surely discharged even during light load or no load.

  The invention according to claim 2 is characterized in that, in the power supply device according to claim 1, the resonance circuit starts the resonance operation prior to turning off the auxiliary switching element.

  In the present invention, the resonance circuit starts a resonance operation before the auxiliary switching element is turned off. That is, it is possible to increase in advance the resonance current generated by the resonance operation prior to turning off the auxiliary switching element, so that the discharge of the auxiliary capacitor is started quickly when the discharge of the auxiliary capacitor is started by turning off the auxiliary switching element. It becomes. Therefore, the discharge time of the auxiliary capacitor is further shortened.

  According to a third aspect of the present invention, in the power supply device according to the first or second aspect, the resonant circuit supplies the resonant current as a charging current for the auxiliary capacitor based on the switching element of the inverter circuit being turned off. The gist of this is to be configured.

  In the present invention, the resonance circuit supplies the resonance current generated in the resonance operation as the charging current of the auxiliary capacitor to the auxiliary capacitor that has already been discharged when the switching element of the inverter circuit is turned off. Thereby, since the resonance current from the resonance circuit is also used as the charging current of the auxiliary capacitor, the charging speed of the auxiliary capacitor is increased and the charging time of the auxiliary capacitor is shortened. Therefore, the auxiliary capacitor can be charged quickly in a short time, and the auxiliary capacitor can be reliably charged even during light loads or no loads.

  According to a fourth aspect of the present invention, in the power supply device according to any one of the first to third aspects, the resonance circuit includes a free wheel diode and is operated alternately in conjunction with the auxiliary switching element. The resonance switching elements are connected to opposite sides of the resonance inductor in opposite directions, and the resonance switching elements are connected to the output terminals of the inverter circuit, respectively.

  In the present invention, the resonant circuit includes a pair of resonant switching elements that have a free-wheeling diode and operate alternately in conjunction with the auxiliary switching element, and are connected in opposite directions to both sides of the resonant inductor. It is configured to be connected to each output terminal of the inverter circuit. That is, the resonance circuit can be simply configured with two switching elements and the resonance inductor.

  According to a fifth aspect of the present invention, in the power supply device according to any one of the first to fourth aspects, the DC conversion circuit is configured such that one smoothing capacitor is connected between the power supply lines. The auxiliary switching circuit is configured such that one auxiliary switching element operated in conjunction with both the first set and the second set of switching elements of the inverter circuit is disposed on one of the power supply lines. The gist.

  In this invention, the DC converter circuit has one smoothing capacitor connected between the power supply lines, and the auxiliary switching circuit is operated in conjunction with both the first set and the second set of switching elements of the inverter circuit. One auxiliary switching element is arranged on one power supply line. That is, the DC conversion circuit and the auxiliary switching circuit are simply configured, which can contribute to the simplification of the configuration of the power supply device.

  According to a sixth aspect of the present invention, in the power supply device according to any one of the first to fourth aspects, the DC converter circuit includes two smoothing capacitors connected in series between the power supply lines. Each of the smoothing capacitors is connected to be able to supply its own DC voltage to the subsequent inverter circuit, and the auxiliary switching circuit corresponds to the first set and the second set of switching elements of the inverter circuit. The gist of the invention is that the auxiliary switching elements operated in conjunction with the elements are respectively arranged on the power supply lines.

  In the present invention, in the DC conversion circuit, two smoothing capacitors are connected in series between the respective power supply lines, and each smoothing capacitor is connected so as to be able to supply its own DC voltage to the subsequent inverter circuit. In the auxiliary switching circuit, auxiliary switching elements that are operated in conjunction with the corresponding elements of the first set and the second set of switching elements of the inverter circuit are arranged on the respective power supply lines. As a result, the DC voltage from each smoothing capacitor is alternately used in the inverter circuit in the subsequent stage, so that it is possible to cope with a high voltage input AC power source while the inverter circuit is configured with a low breakdown voltage.

  The invention according to claim 7 is constituted by a full bridge circuit using a plurality of switching elements, and the first set and the second set of switching elements are alternately turned on and off and supplied via a pair of power supply lines. An inverter circuit for converting a DC voltage into a predetermined AC voltage; and an auxiliary capacitor connected between the power supply lines before the inverter circuit; and a first set of the inverter circuits on the power line before the auxiliary capacitor. And an auxiliary switching circuit in which an auxiliary switching element that is operated in conjunction with the second set of switching elements is disposed, and the auxiliary switching is performed before the switching element of the inverter circuit is turned off in a charged state of the auxiliary capacitor. As the auxiliary capacitor is discharged by turning off the auxiliary switching element, the element is turned off. A power supply apparatus configured to perform soft switching control to turn off a switching element of the inverter circuit after discharging, and is provided between output terminals of the inverter circuit and turns off the auxiliary switching element that starts discharging of the auxiliary capacitor. The gist of the present invention is to provide a resonance circuit that starts a resonance operation before and generates a resonance current that increases the output current of the switching element of the inverter circuit based on the discharge current of the auxiliary capacitor.

In this invention, it is a direct-current power input type power supply device, and this power supply device has the same effect as that of the first aspect.
The invention according to claim 8 uses the power supply device according to any one of claims 1 to 7, and is configured to generate an arc machining voltage for performing arc machining on a workpiece. Power supply device.

  In this invention, since the power supply device according to any one of claims 1 to 7 is used to constitute the power supply device for arc machining, the power supply device for arc machining that can obtain the effects of the above-mentioned claims is provided. Can be provided.

  According to the present invention, it is possible to provide a power supply apparatus and an arc machining power supply apparatus that can reliably charge and discharge an auxiliary capacitor used in soft switching control regardless of a load state, and can reduce switching loss and voltage surge. be able to.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows an arc machine 10 provided with a power supply device 11 for arc machining of this embodiment. The arc machine 10 supplies the machining DC voltage output from the power supply device 11 to the torch TH, and generates an arc from the torch TH toward the workpiece M, thereby causing the workpiece M to be processed. It is a device that performs arc processing such as arc welding and arc cutting.

  The arc machining power supply device 11 is compatible with a 200 V input AC power supply, and includes a DC conversion circuit 12 that converts the AC voltage into a DC voltage, and an inverter circuit 13 that converts the DC voltage into a predetermined high-frequency AC voltage. It becomes.

  The DC conversion circuit 12 is configured by a bridge circuit using a diode, and is connected between a primary side rectifier circuit DR1 for full-wave rectification of a three-phase input AC power supply, and power supply lines L1 and L2 on the output side of the rectifier circuit DR1. It has one smoothing capacitor C0 that smoothes the output voltage of the rectifier circuit DR1. The DC conversion circuit 12 generates a DC voltage from the input AC power supply by the rectifier circuit DR1 and the smoothing capacitor C0.

  The inverter circuit 13 is connected to the power supply lines L1 and L2, and is configured by a full bridge circuit using four switching elements S1 to S4 made of IGBT. In this case, the switching elements S1 and S2 are connected in series between the power supply lines L1 and L2 to form one bridge arm, and the switching elements S3 and S4 are connected in series between the power supply lines L1 and L2. One bridge arm is configured. These switching elements S1 to S4 are reversely connected to freewheeling diodes D1 to D4, respectively. Each of the switching elements S1 to S4 is alternately turned on / off by the switching elements S1 and S4 and the switching elements S2 and S3 being paired based on a control signal from the output control circuit SC input to the gate. The DC voltage output from the conversion circuit 12 is converted into a predetermined high-frequency AC voltage, and the high-frequency AC voltage is supplied to the primary coil of the transformer INT.

  In this embodiment, an auxiliary switching circuit 14 is provided between the inverter circuit 13 and the DC conversion circuit 12, and between the intermediate points N 1 and N 2 of the pair of bridge arms of the inverter circuit 13, that is, the inverter circuit 13. A resonant circuit 15 is provided between the output terminals.

  The auxiliary switching circuit 14 includes one switching element S6 made of IGBT and one auxiliary capacitor C1. The switching element S6 is disposed on the power supply line L2 at the subsequent stage of the smoothing capacitor C0, and a free wheel diode D6 is reversely connected to the switching element S6. The switching element S6 is alternately turned on and off based on a control signal from the output control circuit SC input to the gate. An auxiliary capacitor C1 is connected between the power supply lines L1 and L2 at the subsequent stage of the switching element S6.

  The resonance circuit 15 is connected between an intermediate point (output terminal) N1 between the switching elements S1 and S2 of the inverter circuit 13 and an intermediate point (output terminal) N2 between the switching elements S3 and S4. The resonance circuit 15 includes two switching elements S7 and S8 made of IGBT and two inductors (resonance inductor Lr and series inductor Ls). The switching element S7 has a collector connected to the intermediate point N1, an emitter connected to the emitter of the switching element S8 via the resonant inductor Lr, and a collector of the switching element S8 connected to the intermediate point N2. Reflux diodes D7 and D8 are reversely connected to the switching elements S7 and S8, respectively. The switching elements S7 and S8 are alternately turned on and off based on a control signal from the output control circuit SC input to the gate. The series inductor Ls has one end connected to the intermediate point N1 and the other end connected to the intermediate point N2 via the primary coil of the transformer INT.

  The switching element S6 of the auxiliary switching circuit 14 and the switching elements S7 and S8 of the resonance circuit 15 are turned on / off in association with the operation of the switching elements S1 to S4 of the inverter circuit 13, and the switching elements S1 to S4 are switched. Soft switching control is performed to reduce the loss and reduce the switching loss of the switching elements S6 to S8 themselves. Details of this control will be described later together with the control of the inverter circuit 13.

  The high-frequency AC voltage generated by the inverter circuit 13 is supplied to the primary coil of the transformer INT, and the secondary side rectifier circuit DR2 and the DC reactor DCL are provided on the secondary side of the transformer INT. The secondary side rectifier circuit DR2 includes two diodes D11 and D12 each having an anode connected to both ends of the secondary coil of the transformer INT, and the rectifier circuit DR2 to which the cathodes of the diodes D11 and D12 are connected. A DC reactor DCL is connected to the output side. DC reactor DCL is connected to torch TH via output line L3. The secondary side rectifier circuit DR2 and the DC reactor DCL convert the high-frequency AC voltage from the inverter circuit 13 into an arc machining DC voltage and output it to the torch TH. On the other hand, the output line L4 connected to the intermediate tap of the secondary coil of the transformer INT is connected to the workpiece M, and from the torch TH to the workpiece M based on the supply of the arc machining DC voltage to the torch TH. An arc is generated toward it.

  Next, the control of the output control circuit SC that controls the switching elements S1 to S4 of the inverter circuit 13, the switching element S6 of the auxiliary switching circuit 14, and the switching elements S7 and S8 of the resonance circuit 15 will be described with reference to FIG. Will be described with reference to FIG. In FIG. 2, “S1” to “S4”, “S6” to “S8” indicate the on / off states of the switching elements S1 to S4 and S6 to S8, and the voltage “V” and the current “I”. The subscripts “s1 to s4, s6 to s8, c1” are associated with the symbols of the respective elements, and indicate the voltage and current applied to each element. Note that the subscripts “s1 to s4, s6 to s8” of the voltage “V” and the current “I” include freewheeling diodes D1 to D4 and D6 to D8.

  The output control circuit SC first generates a high-frequency AC voltage from a DC voltage as a main operation of the inverter circuit 13, and sets the switching elements S1 and S4 and the switching elements S2 and S3 of the inverter circuit 13 to a predetermined frequency. Turn on and off alternately with. Here, the output control circuit SC detects the actual output current value from the output line L4 and the like, and performs the PWM control based on the actual output current value and the output set value, that is, the on-pulse width W (duty). The on-time of the switching elements S1 to S4 is adjusted by the change, and the high-frequency AC voltage is controlled.

  The output control circuit SC operates the switching element S6 in association with the on / off operation of the switching elements S1 to S4 of the inverter circuit 13, and sets the switching element S7 in combination with the switching elements S1 and S4. Soft switching control for operating the switching elements S6 to S8 of the auxiliary switching circuit 14 and the resonance circuit 15 in association with the main operation of the inverter circuit 13 is also performed by operating the switching element S8 in combination with S3.

  More specifically, the output control circuit SC simultaneously turns on the switching element S6 of the auxiliary switching circuit 14 on the on side of the switching elements S1 and S4 of the inverter circuit 13. On the other hand, on the off side of the switching elements S1 and S4 of the inverter circuit 13, the output control circuit SC turns off the switching element S6 a predetermined time T1 before the off, and further turns off the switching element S6 for a predetermined time from the off. The switching element S7 of the resonance circuit 15 is turned on before T2. Then, the output control circuit SC turns off the switching element S7 simultaneously with turning on the other pair of switching elements S2, S3. Incidentally, at least the other pair of switching elements S2, S3, and S8 is maintained in the OFF state during a period from when the switching elements S1 and S4 are turned on to when the switching element S7 is turned off. The on / off operation of the other pair of switching elements S2, S3, S8 is performed after the switching elements S2, S3 are turned on in the same manner as the on / off operation of the switching elements S1, S4, S7.

  With the switching control of the output control circuit SC, when the current and voltage changes in various parts of the circuit at each timing are viewed, first, the switching elements S1, S4, S6 are in the ON state, and the switching elements S2, S3, S7, Before time t0 when S8 is in the off state, the voltage across the terminals of the smoothing capacitor C0 (auxiliary capacitor C1) is supplied to the switching elements S1 and S4 of the inverter circuit 13. The output voltage from the switching elements S1 and S4 is supplied to the primary coil of the transformer INT via the series inductor Ls. Accordingly, on the secondary side of the transformer INT, on the diode D11 side of the secondary rectifier circuit DR2 The DC voltage for arc machining is output to the torch TH through the DC reactor DCL.

  At “time t0”, the switching element S7 is turned on. Based on this ON, the resonance circuit 15 starts a resonance operation, a resonance current is generated in the resonance inductor Lr, and this resonance current flows from the intermediate point N1 through the path of the switching element S7, the resonance inductor Lr, and the return diode D8. As a result, the current Is7 that flows through the switching element S7 increases, and the currents (output currents) Is1 and Is4 that flow through the switching elements S1 and S4 increase accordingly. Note that since the resonance current generated by the resonance inductor Lr rises slowly from zero, the switching element S7 is turned on at zero current, and its switching loss is reduced. The switching elements S1 and S4 continue to supply the output voltage based on the voltage across the smoothing capacitor C0 to the primary coil side of the transformer INT, and the DC reactor DCL from the diode D11 side on the secondary side of the transformer INT. The current supply to is continued. The voltage between the terminals of the auxiliary capacitor C1 is still maintained equal to the voltage between the terminals of the smoothing capacitor C0.

  At “time t1”, the switching element S6 is turned off. Although the supply of the inter-terminal voltage from the smoothing capacitor C0 to the switching elements S1 and S4 is cut off based on this off, the discharge of the auxiliary capacitor C1 is started and replaced with the supply of the inter-terminal voltage of the capacitor C1. When the switching element S6 is turned off, the voltage across the auxiliary capacitor C1 is charged up to the voltage across the smoothing capacitor C0 before time t1, so that the switching element S6 is set to zero voltage (the potential difference between the terminals is zero). ) And the switching loss is reduced. From the switching elements S1 and S4, the supply of the output voltage based on the voltage across the terminal of the auxiliary capacitor C1 is continued to the primary coil side of the transformer INT, and the secondary side of the transformer INT similarly starts from the diode D11 side. The current supply to the direct current reactor DCL is continued.

  Also at this time, the current values Is1 and Is4 that flow through the switching elements S1 and S4 are larger than the current value when the current flows only on the primary coil side of the transformer INT, and in this embodiment, the switching element S7 is Since the flowing current Is7 is set to further increase than immediately before time t1, the currents Is1 and Is4 flowing through the switching elements S1 and S4 are further increased in conjunction with this. Thereby, the discharge speed of the auxiliary capacitor C1 is increased, and the discharge time of the auxiliary capacitor C1 is shortened. Accordingly, the auxiliary capacitor C1 is quickly discharged in a short time before the switching elements S1 and S4 are turned off.

  When the discharge of the auxiliary capacitor C1 is completed at “time t2,” the path using the switching element S1 in the on state, the primary coil (series inductor Ls) of the transformer INT, and the freewheeling diode D3, and the switching element in the on state A return current flows through S4, a path using the primary coil (series inductor Ls) of the transformer INT and the return diode D2. Further, the return current also flows through the path branched to the switching element S7 side based on the resonance current of the resonance inductor Lr. On the secondary side of the transformer INT, based on the release of the electromagnetic energy accumulated in the DC reactor DCL before time t2, a reflux current flows through both the diodes D11 and D12.

  At “time t3”, the switching elements S1 and S4 are turned off. Since the auxiliary capacitor C1 is already discharged at time t2 when the switching elements S1 and S4 are turned off, the switching elements S1 and S4 can be turned off with zero voltage (the potential difference between the terminals is zero), and the switching loss is reduced. Has been. Also, based on this off, based on the release of electromagnetic energy stored in the series inductor Ls, a return current flows through the path using the return diodes D2 and D3, and based on the release of electromagnetic energy stored in the resonant inductor Lr. Thus, the reflux current continues to flow through the path branched to the switching element S7 side. Then, charging of the auxiliary capacitor C1 is started again based on both of these return currents, which are larger than the current value in the case where only the primary coil side of the transformer INT flows. Thereby, the charging speed of the auxiliary capacitor C1 is increased, and the charging time of the auxiliary capacitor C1 is shortened. Therefore, the auxiliary capacitor C1 is quickly charged in a short time before the switching elements S2, S3, and S6 are turned on next time. On the secondary side of the transformer INT, a return current flowing through both paths of the diodes D11 and D12 is continuously generated.

  At “time t4”, the charging of the auxiliary capacitor C1 is completed. As a result, the return current generated based on the release of the electromagnetic energy accumulated in the series inductor Ls and the resonant inductor Lr is switched to a path using the return diode D6, and thereby the charging of the smoothing capacitor C0 is started. Note that, on the secondary side of the transformer INT, a reflux current still flows through both paths of the diodes D11 and D12.

  When the electromagnetic energy of the series inductor Ls and the resonant inductor Lr eventually disappears at “time t5”, the charging of the smoothing capacitor C0 is completed, and the return current (resonant current) generated on the primary side of the transformer INT disappears. .

  At “time t6”, the switching element S7 is turned off and the switching elements S2, S3, and S6 are both turned on. In this case, since the return current (resonance current) on the primary side of the transformer INT has disappeared, the switching element S7 is turned off at zero current, and the switching loss is reduced. In addition, since the rise from zero of the current applied to the switching elements S2, S3, and S6 is gentle due to the series inductor Ls, the switching elements S2, S3, and S6 are turned on at zero current, and these switching losses are reduced. ing. Further, in the switching element S6, since the voltage between the terminals of the auxiliary capacitor C1 and the smoothing capacitor C0 is the same voltage, the switching element S6 is turned on at zero voltage, which also reduces the switching loss.

  Based on the switching elements S2, S3, and S6 being turned on, the voltage across the terminals of the smoothing capacitor C0 is supplied to the switching elements S2 and S3 of the inverter circuit 13. The output voltage from the switching elements S2 and S3 is supplied to the primary coil of the transformer INT via the series inductor Ls. Accordingly, on the secondary side of the transformer INT, the diode D12 side of the secondary rectifier circuit DR2 is provided. The DC voltage for arc machining is output to the torch TH through the DC reactor DCL.

  At “time t7”, the switching element S8 is turned on, and thereafter, the switching elements S2, S3, S6, and S8 perform the same operation as described above, and the output of the arc machining DC voltage is continued. ing.

Next, characteristic effects of the present embodiment will be described.
(1) In this embodiment, the resonance circuit 15 is provided between the intermediate points N1 and N2 (between output terminals) of each bridge arm of the inverter circuit 13. The resonant circuit 15 starts a resonant operation by a time T2 prior to turning off the switching element S6 of the auxiliary switching circuit 14 that starts discharging of the auxiliary capacitor C1, and switches the switching element S1 of the inverter circuit 13 based on the discharge current of the auxiliary capacitor C1. A resonance current is generated such that the output current (currents Is1 to Is4) of .about.S4 increases. Thereby, the discharge speed of the auxiliary capacitor C1 is increased, and the discharge time of the auxiliary capacitor C1 is shortened. Therefore, the auxiliary capacitor C1 is discharged quickly in a short time, and the auxiliary capacitor C1 can be reliably discharged even during light load or no load. As a result, it is possible to provide the arc machining power supply device 11 that can reduce switching loss and suppress voltage surge.

  (2) In the present embodiment, the switching elements S7 and S8 of the resonance circuit 15 are turned on before the switching element S6 is turned off at the time of turning on, and the resonance by the resonance inductor Lr before the switching element S6 is turned off. Operation starts. That is, the switching elements S7 and S8 of the resonance circuit 15 are turned on from time to time before the switching element S6 of the auxiliary switching circuit 14 is turned off, thereby assisting the resonance current (resonance energy) of the inductor Lr that gradually rises. It can be increased in advance before the start of the discharge of the capacitor C1, so that the discharge becomes quicker when the discharge of the auxiliary capacitor C1 is started by turning off the switching element S6. Therefore, in the present embodiment, the discharge time of the auxiliary capacitor C1 can be further shortened.

  (3) In the present embodiment, the resonance circuit 15 supplies the resonance current generated in the resonance operation to the auxiliary capacitor C1 with respect to the auxiliary capacitor C1 that has already been discharged when the switching elements S1 to S4 of the inverter circuit 13 are turned off. Supply as charging current. Thereby, since the resonance current from the resonance circuit 15 is also used as the charging current of the auxiliary capacitor C1, the charging speed of the auxiliary capacitor C1 is increased, and the charging time of the auxiliary capacitor C1 is shortened. Therefore, the auxiliary capacitor C1 is charged quickly in a short time, and the auxiliary capacitor C1 can be reliably charged even at a light load or no load.

  (4) In the present embodiment, the resonance circuit 15 includes the free-wheeling diodes D7 and D8, and the switching elements S7 and S8 that are alternately operated in conjunction with the switching element S6 are connected in opposite directions on both sides of the resonance inductor Lr. The switching elements S7 and S8 are connected between the intermediate points N1 and N2 of the bridge arms of the inverter circuit 13. Further, the resonance circuit 15 of the present embodiment includes a series inductor Ls connected in series to the primary coil of the transformer INT. That is, the resonance circuit 15 can be simply configured by the two switching elements S7 and S8 and the inductors Lr and Ls.

  (5) In the present embodiment, the DC conversion circuit 12 is configured simply using one smoothing capacitor C0, and the auxiliary switching circuit 14 is configured simply using one switching element S6, thereby simplifying the configuration of the power supply device 11. Can contribute.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 shows an arc machine 10 provided with the arc machining power supply device 11a of the present embodiment. The arc machining power supply device 11a of this embodiment is compatible with a 400V input AC power supply.

More specifically, in the DC converter circuit 12a, two smoothing capacitors Ca and Cb having the same capacity are connected in series between the power supply lines L1 and L2 on the output side of the primary side rectifier circuit DR1.
In the auxiliary switching circuit 14a, the switching element S5 made of IGBT is arranged on the power supply line L1 after the smoothing capacitors Ca and Cb, and the switching element S6 made of IGBT is arranged on the power supply line L2 after the smoothing capacitors Ca and Cb. Has been. Reflux diodes D5 and D6 are reversely connected to the switching elements S5 and S6, respectively. The switching elements S5 and S6 are alternately turned on and off based on a control signal from the output control circuit SC input to the gate. Diodes D9 and D10 are connected in series between the power supply lines L1 and L2 between the switching elements S5 and S6 and the auxiliary capacitor C1, and the diodes D9 and D10 are sequentially connected from the power supply line L2 toward the power supply line L1. Connected to be in the direction. The diodes D9 and D10 and the smoothing capacitors Ca and Cb are connected to each other.

  Next, the control of the output control circuit SC that controls the switching elements S1 to S4 of the inverter circuit 13, the switching elements S5 and S6 of the auxiliary switching circuit 14a, and the switching elements S7 and S8 of the resonance circuit 15 will be described. This will be described with reference to FIG. In FIG. 4, “S1” to “S8” also indicate the on / off states of the switching elements S1 to S8 in this embodiment, and the subscripts “s1 to s8,” indicating the voltage “V” and the current “I”. “c1” is associated with the symbol of each element, and indicates the voltage and current applied to each element. The subscripts “s1 to s8” of the voltage “V” and the current “I” include the freewheeling diodes D1 to D8.

  The output control circuit SC of the present embodiment simultaneously turns on the switching element S5 of the auxiliary switching circuit 14a on the on side of the switching elements S1 and S4 of the inverter circuit 13. On the other hand, on the off side of the switching elements S1 and S4 of the inverter circuit 13, the output control circuit SC turns off the switching element S5 a predetermined time T1 before the off and further turns off the switching element S5 for a predetermined time from the off. The switching element S7 of the resonance circuit 15 is turned on before T2. Then, the output control circuit SC turns off the switching element S7 simultaneously with turning on the other pair of switching elements S2, S3. Incidentally, at least the other pair of switching elements S2, S3, S6, and S8 is maintained in the OFF state during a period from when the switching elements S1 and S4 are turned on to when the switching element S7 is turned off. The on / off operation of the other set of switching elements S2, S3, S6, and S8 is performed in the same manner as the on / off operation of the switching elements S1, S4, S5, and S7 after the switching elements S2 and S3 are turned on.

  That is, by performing the control as described above, during the on / off operation of the set of the switching elements S1 and S4 of the inverter circuit 13, the output of the primary side rectifier circuit DR1 through a path using one smoothing capacitor Ca and the diode D10. A DC voltage that is half of the voltage is supplied to the inverter circuit 13 and when the switching elements S2 and S3 are turned on and off, the output voltage of the primary side rectifier circuit DR1 is obtained through a path using one of the smoothing capacitors Cb and the diode D9. Half of the DC voltage is supplied to the inverter circuit 13 so that the input AC power supply of 400 V operates in the same manner as in the first embodiment.

Next, characteristic effects of the present embodiment will be described.
(1) In this embodiment, the configurations of the DC conversion circuit 12a and the auxiliary switching circuit 14a are slightly different from those of the first embodiment, but the same effects as the effects (1) to (4) of the first embodiment. Can be obtained.

  (2) In the present embodiment, the DC converter circuit 12a uses two smoothing capacitors Ca and Cb, and the auxiliary switching circuit 14a uses the two switching elements S5 and S6 and the diodes D9 and D10 to make the above connection. As a result, the inverter circuit 13 and the resonance circuit 15 and the like subsequent to the auxiliary switching circuit 14a have the same circuit configuration, and can correspond to an input AC power supply of 400V higher than that of the first embodiment.

In addition, you may change embodiment of this invention as follows.
In each of the above embodiments, the resonance circuit 15 is configured by the two switching elements S7 and S8 and the inductors Lr and Ls. However, the number and arrangement of the switching elements and inductors may be appropriately changed. In addition to these elements, a capacitor, a resistor, or the like may be added or replaced.

  In each of the above embodiments, the switching elements S7 and S8 of the resonance circuit 15 are turned on prior to the switching elements S5 and S6 being turned off to start the resonance operation, but the switching elements S7 and S8 are turned on by the switching elements S5 and S6. It may be simultaneously with turning off S6. Further, before the switching elements S1 to S4 are turned off, the switching elements S7 and S8 can be turned on slightly later than the switching elements S5 and S6 are turned off. Further, the switching elements S7 and S8 may be turned off not before the switching elements S1 to S4 to be turned on next, but before the switching elements S1 to S4 in which the resonance current has disappeared.

  In each of the above embodiments, the resonance circuit 15 is configured to supply the resonance current as the charging current of the auxiliary capacitor C1 based on the switching elements S1 to S4 being turned off. It is also possible to adopt a configuration that occurs only at the time of discharging, and that does not use the resonance current as the charging current.

In each of the above embodiments, the IGBT is used for the switching elements S1 to S8. However, a switching element other than the IGBT may be used.
In each of the above embodiments, the arc machining power supply device 11 is used. However, the arc machining power supply device 11 may be used for purposes other than arc machining. Moreover, you may implement in the DC-AC conversion power supply device which abbreviate | omitted DC conversion circuits 12 and 12a.

It is a circuit diagram which shows the power supply apparatus for arc processing (corresponding to 200V input) in the first embodiment. It is a wave form diagram of each place of the power supply device in 1st Embodiment. It is a circuit diagram which shows the power supply apparatus (400V input corresponding) for arc processing in 2nd Embodiment. It is a wave form diagram of the power supply device various places in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 11a ... Power supply device, 12 ... DC conversion circuit, 13 ... Inverter circuit,
14, 14a ... auxiliary switching circuit, 15 ... resonance circuit, C1 ... auxiliary capacitor,
C0, Ca, Cb ... smoothing capacitor,
D7, D8 ... freewheeling diode, DR1 ... primary side rectifier circuit (rectifier circuit),
L1, L2 ... power line, Lr ... resonant inductor, M ... workpiece,
N1, N2 ... Intermediate point (output terminal),
S1 to S4 ... switching elements,
S5, S6 ... switching elements (auxiliary switching elements),
S7, S8... Switching elements (resonance switching elements).

Claims (8)

A DC conversion circuit having a smoothing capacitor connected between the rectifier circuit and a pair of power supply lines on its output side, and converting the input AC power supply into a DC voltage obtained by rectifying and smoothing;
It is composed of a full bridge circuit using a plurality of switching elements, and the first set and the second set of switching elements are alternately turned on and off to convert the DC voltage supplied through the power lines into a predetermined AC voltage. An inverter circuit to convert;
And having an auxiliary capacitor connected between the power supply lines between the smoothing capacitor and the inverter circuit, and a first set of the inverter circuit and a first capacitor on the power supply line between the smoothing capacitor and the auxiliary capacitor. An auxiliary switching circuit in which auxiliary switching elements that are operated in conjunction with two sets of switching elements are arranged;
The auxiliary switching element is turned off prior to turning off the switching element of the inverter circuit in a charged state of the auxiliary capacitor, and the switching element of the inverter circuit is discharged after the discharge of the auxiliary capacitor due to the auxiliary switching element being turned off. A power supply device configured to perform soft switching control to be turned off,
An output current of the switching element of the inverter circuit, which is provided between the output terminals of the inverter circuit, starts a resonance operation before the auxiliary switching element is turned off and starts discharging of the auxiliary capacitor, and is based on a discharge current of the auxiliary capacitor A power supply apparatus comprising: a resonance circuit that generates a resonance current that increases the current. The power supply device according to claim 1,
The resonance circuit starts the resonance operation prior to turning off the auxiliary switching element. The power supply device according to claim 1 or 2,
The resonance circuit is configured to supply the resonance current as a charging current for the auxiliary capacitor based on turning off of a switching element of the inverter circuit. The power supply device according to any one of claims 1 to 3,
The resonant circuit includes a freewheeling diode, and a pair of resonant switching elements that are alternately operated in conjunction with the auxiliary switching element are connected in opposite directions to both sides of the resonant inductor, and the resonant switching elements are connected to the resonant circuit. A power supply device comprising: an inverter circuit connected to each output terminal. In the power supply device according to any one of claims 1 to 4,
The DC conversion circuit is formed by connecting one smoothing capacitor between the power lines.
The auxiliary switching circuit is characterized in that one auxiliary switching element that operates in conjunction with both the first set and the second set of switching elements of the inverter circuit is disposed on one of the power supply lines. Power supply. In the power supply device according to any one of claims 1 to 4,
The DC conversion circuit includes two smoothing capacitors connected in series between the power supply lines, and each of the smoothing capacitors is connected to be able to supply its own DC voltage to the subsequent inverter circuit. ,
The auxiliary switching circuit is configured such that the auxiliary switching elements that are operated in conjunction with corresponding elements of the first set and the second set of switching elements of the inverter circuit are respectively arranged on the power supply lines. Power supply. Consists of a full-bridge circuit using a plurality of switching elements. The first and second sets of switching elements are alternately turned on and off to convert a DC voltage supplied via a pair of power lines into a predetermined AC voltage. An inverter circuit to
It has an auxiliary capacitor connected between the power supply lines in the previous stage of the inverter circuit, and is operated in conjunction with the first and second sets of switching elements of the inverter circuit on the power supply line in the previous stage of the auxiliary capacitor. An auxiliary switching circuit in which an auxiliary switching element is disposed;
The auxiliary switching element is turned off prior to turning off the switching element of the inverter circuit in a charged state of the auxiliary capacitor, and the switching element of the inverter circuit is discharged after the discharge of the auxiliary capacitor due to the auxiliary switching element being turned off. A power supply device configured to perform soft switching control to be turned off,
An output current of the switching element of the inverter circuit based on a discharge current of the auxiliary circuit, which is provided between the output terminals of the inverter circuit, starts a resonance operation before turning off of the auxiliary switching element to start discharging of the auxiliary capacitor A power supply apparatus comprising: a resonance circuit that generates a resonance current that increases the current.   An arc machining power supply device configured to generate an arc machining voltage for performing arc machining on a workpiece using the power supply device according to any one of claims 1 to 7.

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