JP5917097B2 - Power supply device and power supply device for arc machining - Google Patents

Description

  The present invention relates to a power supply device including a half-bridge type inverter circuit and a power supply device for arc machining.

  A power supply device used for an arc machine or the like converts DC power generated from AC input power into high-frequency AC power by switching operation of an inverter circuit, and arc-welding high-frequency AC power adjusted by a welding transformer in a subsequent circuit. It is converted to DC output power suitable for arc machining such as. The adjustment of the output power is performed by controlling the switching operation of the inverter circuit.

  For example, the power supply device disclosed in Patent Document 1 includes a half-bridge type inverter circuit, and pulse width modulation control (PWM control) for adjusting the on-pulse width of the switching element of the circuit is performed, and output power is adjusted. Yes. In addition, the power supply device includes a switching element (power switching element) and an auxiliary switching circuit such as a capacitor between the primary rectifier circuit and the inverter circuit. And soft switching control which reduces the switching loss of each switching element is performed from the ON / OFF operation | movement of the auxiliary switching element linked with the switching element of the inverter circuit, and the charging / discharging operation | movement of the auxiliary capacitor accompanying this.

JP 2005-279774 A

  By the way, in PWM control, normally, when adjusting the output of the power supply device to be extremely small, the on-pulse width of each control pulse signal output to the inverter circuit and the auxiliary switching circuit is set to be extremely narrow. Therefore, an event that the switching element cannot be turned on occurs, and there is a possibility that problems such as output instability and magnetic demagnetization may occur.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a power supply device and an arc machining power supply device capable of stabilizing the output at the time of low output.

  In order to solve the above-described problem, the invention according to claim 1 is a half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off, and converts input DC power into high-frequency AC power; An auxiliary switching circuit provided on a power supply line upstream of the inverter circuit and having a switching element operating in conjunction with the switching operation of the inverter circuit and an auxiliary capacitor connected between the power supply lines downstream of the element; The output of the inverter circuit that controls the switching operation of the auxiliary switching circuit in conjunction with this and performs output control that adjusts the output power to the load, and that turns off the switching element of the auxiliary switching circuit first and turns it off later. Operation to reduce switching loss of switching elements A power supply device configured to perform soft switching control including adjusting an on-pulse width of a control pulse signal output to the switching element of the inverter circuit and outputting the control pulse signal to the switching element of the auxiliary switching circuit accordingly A pulse width modulation control means for adjusting an on-pulse width of the control pulse signal to be adjusted, and a phase shift control for adjusting a mutual phase difference between the control pulse signal paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit The gist of the present invention is that it comprises means for controlling the pulse width modulation when the output request is large, and control switching means for switching to the phase shift control means when the output request is small.

  In the present invention, when the output request is large, pulse width modulation control (PWM control) is performed to adjust the on-pulse width of each control pulse signal output to the inverter circuit and the auxiliary switching circuit linked to the inverter circuit. When it is small, the phase shift control (PSM control) for adjusting the mutual phase difference between the control pulse signals paired between the inverter circuit and the auxiliary switching circuit is switched. That is, if PWM control is performed as it is when a low output is required, an event may occur in which the switching elements of the inverter circuit and the auxiliary switching circuit cannot be turned on. Therefore, when the low output is requested, the control is switched to the PSM control, and the current peak value / average value is reduced by the phase adjustment in a state where the on-pulse width of each control pulse signal is secured, so that the output is low. As a result, the switching elements of the inverter circuit and the auxiliary switching circuit can be reliably turned on even when a low output is required, so that a stable output can be obtained.

According to a second aspect of the present invention, in the power supply device according to the first aspect, the control switching unit determines whether to switch the pulse width modulation control unit and the phase shift control unit with the inverter circuit and the auxiliary switching circuit. The on-pulse width of each of the switching elements is set to the on-pulse width that is larger than a predetermined narrow pulse width at which each of the switching elements of the inverter circuit and the auxiliary switching circuit can be sufficiently turned on. The pulse width modulation control means is used when an output is requested, and the phase of the control pulse signal is adjusted in a state where the on pulse width is fixed to the predetermined narrow pulse width when the on pulse width can be smaller than the predetermined narrow pulse width. The gist is to switch to the phase shift control means to be performed.

  In the present invention, the PWM control is performed in the output request period set to an on-pulse width larger than a predetermined narrow pulse width at which each switching element of the inverter circuit and the auxiliary switching circuit can be sufficiently turned on, and the on-pulse width is reduced to the predetermined narrow pulse width. In a low output request period that can be smaller than the pulse width, PSM control is performed in which the phase of each control pulse signal is adjusted while the on-pulse width is fixed to the predetermined narrow pulse width. As a result, by inheriting a predetermined narrow pulse width when switching from PWM control and switching to PSM control, the output of each switching element of the inverter circuit and auxiliary switching circuit is reliably turned on, and the output is stabilized. It is possible to stabilize the output when the is switched.

According to a third aspect of the present invention, there is provided a half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off and converts input DC power into high-frequency AC power, and a power supply line before the inverter circuit. An auxiliary switching circuit having a switching element that operates in conjunction with the switching operation of the inverter circuit and an auxiliary capacitor connected between power supply lines downstream of the element, the inverter circuit and the auxiliary switching circuit that is interlocked therewith The switching operation of the inverter circuit is adjusted to adjust the output power to the load, and the switching element of the inverter circuit that turns off the switching element of the auxiliary switching circuit first and then turns off is reduced. Soft switching system including operation And a control pulse signal output to the switching element of the auxiliary switching circuit according to the on-pulse width of the control pulse signal output to the switching element of the inverter circuit. A pulse width modulation control means for adjusting the on-pulse width, a phase shift control means for adjusting a mutual phase difference between control pulse signals paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit, and an output The pulse width modulation control means is provided when the request is large, and the control switching means is switched to the phase shift control means when the output request is small. The phase shift control means outputs a control pulse signal to the inverter circuit. In contrast, the control pulse signal output to the auxiliary switching circuit The shifting relatively advanced side as its gist.

In the present invention, when the output request is large, pulse width modulation control (PWM control) is performed to adjust the on-pulse width of each control pulse signal output to the inverter circuit and the auxiliary switching circuit linked to the inverter circuit. When it is small, the phase shift control (PSM control) for adjusting the mutual phase difference between the control pulse signals paired between the inverter circuit and the auxiliary switching circuit is switched. That is, if PWM control is performed as it is when a low output is required, an event may occur in which the switching elements of the inverter circuit and the auxiliary switching circuit cannot be turned on. Therefore, when the low output is requested, the control is switched to the PSM control, and the current peak value / average value is reduced by the phase adjustment in a state where the on-pulse width of each control pulse signal is secured, so that the output is low. As a result, the switching elements of the inverter circuit and the auxiliary switching circuit can be reliably turned on even when a low output is required, so that a stable output can be obtained. In PSM control, the control pulse signal output to the auxiliary switching circuit is relatively shifted to the advance side with respect to the control pulse signal output to the inverter circuit. As a result, the soft switching operation in which the switching element of the inverter circuit is turned off after the switching element of the auxiliary switching circuit is turned off is continued even during the PSM control, thereby contributing to the reduction of switching loss.

According to a fourth aspect of the present invention, there is provided a half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off and converts input DC power into high-frequency AC power, and a power supply line upstream of the inverter circuit. An auxiliary switching circuit having a switching element that operates in conjunction with the switching operation of the inverter circuit and an auxiliary capacitor connected between power supply lines downstream of the element, the inverter circuit and the auxiliary switching circuit that is interlocked therewith The switching operation of the inverter circuit is adjusted to adjust the output power to the load, and the switching element of the inverter circuit that turns off the switching element of the auxiliary switching circuit first and then turns off is reduced. Soft switching system including operation And a control pulse signal output to the switching element of the auxiliary switching circuit according to the on-pulse width of the control pulse signal output to the switching element of the inverter circuit. A pulse width modulation control means for adjusting the on-pulse width, a phase shift control means for adjusting a mutual phase difference between control pulse signals paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit, and an output The pulse width modulation control means when the demand is large, and the control switching means for switching to the phase shift control means when the output demand is small, the phase shift control means, the control pulse signal output to the inverter circuit And a control pulse signal output to the auxiliary switching circuit. Fixed side, to shift the other side as its gist.
In the present invention, when the output request is large, pulse width modulation control (PWM control) is performed to adjust the on-pulse width of each control pulse signal output to the inverter circuit and the auxiliary switching circuit linked to the inverter circuit. When it is small, the phase shift control (PSM control) for adjusting the mutual phase difference between the control pulse signals paired between the inverter circuit and the auxiliary switching circuit is switched. That is, if PWM control is performed as it is when a low output is required, an event may occur in which the switching elements of the inverter circuit and the auxiliary switching circuit cannot be turned on. Therefore, when the low output is requested, the control is switched to the PSM control, and the current peak value / average value is reduced by the phase adjustment in a state where the on-pulse width of each control pulse signal is secured, so that the output is low. As a result, the switching elements of the inverter circuit and the auxiliary switching circuit can be reliably turned on even when a low output is required, so that a stable output can be obtained.

  In the present invention, in the PSM control, one side of each control pulse signal output to the inverter circuit and the auxiliary switching circuit is fixed and the other side is shifted. As a result, the phase adjustment is easy because only one control pulse signal needs to be adjusted.

According to a fifth aspect of the present invention, in the power supply device according to the third or fourth aspect, the control switching means has a predetermined narrow pulse width at which each switching element of the inverter circuit and the auxiliary switching circuit can be sufficiently turned on. The pulse width modulation control means is used when an output request is set to a large on-pulse width, and the on-pulse width is fixed to the predetermined narrow pulse width when the output request can be smaller than the predetermined narrow pulse width. The gist of the present invention is to switch to the phase shift control means for adjusting the phase of the control pulse signal in such a state.
In the present invention, the PWM control is performed in the output request period set to an on-pulse width larger than a predetermined narrow pulse width at which each switching element of the inverter circuit and the auxiliary switching circuit can be sufficiently turned on, and the on-pulse width is reduced to the predetermined narrow pulse width. In a low output request period that can be smaller than the pulse width, PSM control is performed in which the phase of each control pulse signal is adjusted while the on-pulse width is fixed to the predetermined narrow pulse width. As a result, by inheriting a predetermined narrow pulse width when switching from PWM control and switching to PSM control, the output of each switching element of the inverter circuit and auxiliary switching circuit is reliably turned on, and the output is stabilized. It is possible to stabilize the output when the is switched.
According to a sixth aspect of the present invention, in the power supply device according to the second or fifth aspect, the predetermined narrow pulse width is set to a minimum pulse width at which each switching element of the inverter circuit and the auxiliary switching circuit can be turned on. This is the gist.
The invention according to claim 7 is the power supply device according to any one of claims 1 to 6 , wherein the high-frequency AC power generated by the inverter circuit is voltage-adjusted and output to the secondary side. The gist of the invention is that it includes an output conversion circuit that converts high-frequency AC power that has undergone voltage adjustment through the transformer into output power corresponding to a load.

  The present invention includes a transformer that adjusts the voltage of the high-frequency AC power generated by the inverter circuit, and an output conversion circuit that converts the high-frequency AC power voltage-adjusted by the transformer into output power corresponding to the load. Output stabilization at the time of low output of a power supply device including these becomes possible.

The invention described in claim 8 is an arc machining power supply device configured to generate the output power for arc machining using the power supply device according to any one of claims 1 to 7 .
According to the present invention, it is possible to provide a power supply device for arc machining capable of stabilizing output at low output.

  ADVANTAGE OF THE INVENTION According to this invention, the power supply device and arc processing power supply device which can aim at the output stabilization at the time of a low output can be provided.

It is a circuit diagram of the power supply device for arc processing in an embodiment. It is a voltage / current waveform diagram of each part of the power supply device, (a) at the time of PWM operation (when output is large), (b) at the time of PWM-PSM critical operation (when output is small), (c) at the time of PSM operation (minimum output) Time). It is explanatory drawing of a PWM-PSM control aspect. FIG. 6 is a waveform diagram of a control pulse signal in another example, where (a) is during PWM operation (when output is large), (b) is during PWM-PSM critical operation (when output is small), and (c) is during PSM operation (minimum output). Time). FIG. 6 is a waveform diagram of a control pulse signal in another example, where (a) is during PWM operation (when output is large), (b) is during PWM-PSM critical operation (when output is small), and (c) is during PSM operation (minimum output). Time).

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, the arc machine supplies the output power generated by the arc machining power supply 11 to the torch TH, generates an arc from the torch TH toward the workpiece M, and processes the workpiece. It is an apparatus that performs arc processing such as arc welding and arc cutting on M.

The power supply device 11 includes a DC conversion circuit 12, an inverter circuit 13, an auxiliary switching circuit 14, a transformer INT, and an output conversion circuit 15.
The DC conversion circuit 12 includes a rectifier circuit DR1 formed of a diode bridge and smoothing capacitors C1 and C2. Smoothing capacitors C1 and C2 are connected in series between power supply lines L1 and L2 extending from the output terminal of the rectifier circuit DR1, and a power supply line L3 extends between the smoothing capacitors C1 and C2. The DC conversion circuit 12 converts the three-phase AC input power supplied from the commercial power source into DC power by the rectifier circuit DR1, and charges the smoothing capacitors C1 and C2. The DC power charged by the smoothing capacitors C1 and C2 is output to the auxiliary switching circuit 14 and the subsequent inverter circuit 13 via the power supply lines L1 and L3 or the power supply lines L3 and L2, and the output of the rectifier circuit DR1. A voltage value that is half the voltage is output to these subsequent circuits.

  The inverter circuit 13 includes two switching elements TR1 and TR2 such as IGBTs, and is configured by a half bridge circuit in which the switching element TR1 is disposed on the power supply line L1 side and the switching element TR2 is disposed on the power supply line L2. Reflux diodes D1 and D2 are reversely connected to the switching elements TR1 and TR2, respectively. The power line L3 connected between the smoothing capacitors C1 and C2 is connected to one end of the primary coil of the transformer INT, whereas the output terminal of the inverter circuit 13 (a node between the switching elements TR1 and TR2). Is connected to the other end of the primary coil. A control pulse signal is input from the control circuit 21 to the gates of the switching elements TR1 and TR2, and the switching elements TR1 and TR2 are alternately turned on and off to generate high-frequency AC power from DC power. Is supplied to the primary coil of the transformer INT.

  An auxiliary switching circuit 14 having switching elements TR3 and TR4 such as IGBTs, diodes D5 and D6, and auxiliary capacitors C3 and C4 is provided between the inverter circuit 13 and the DC conversion circuit 12. The switching elements TR3 and TR4 have their freewheeling diodes D3 and D4 reversely connected to each other, the switching element TR3 is on the power supply line L1 in the subsequent stage of the DC conversion circuit 12, and the switching element TR4 is the power supply in the subsequent stage of the DC conversion circuit 12. Arranged on the line L2. At the subsequent stage of the switching elements TR3 and TR4, a diode D5 having an anode connected to the power supply line L3, a cathode connected to the power supply line L1, and a diode D6 having an anode connected to the power supply line L2 and a cathode connected to the power supply line L3. Has been placed. Further, an auxiliary capacitor C3 is connected between the power supply lines L1 and L3, and an auxiliary capacitor C4 is connected between the power supply lines L3 and L2 at the subsequent stage of the diodes D5 and D6. A control pulse signal is input from the control circuit 21 to the gates of the switching elements TR3 and TR4. The switching element TR3 is driven on and off in conjunction with the switching element TR1 of the inverter circuit 13 and the switching element TR4 in conjunction with the switching element TR2. The As a result, soft switching is performed to reduce the switching loss of the switching elements TR1 and TR2 of the inverter circuit 13 including the switching elements TR3 and TR4 themselves.

  The transformer INT adjusts the voltage of the high-frequency AC power generated by the inverter circuit 13 and outputs the high-frequency AC power adjusted to a predetermined voltage from the secondary coil to the output conversion circuit 15.

  The output conversion circuit 15 includes a rectifier circuit DR2 composed of two diodes and a direct current reactor DCL. The rectifier circuit DR2 includes two diodes whose anodes are connected to both ends of the secondary coil of the transformer INT, and the cathode of each diode is connected to the DC reactor DCL. The direct current reactor DCL is disposed on the output line L4, and the output line L5 is connected to the intermediate point of the secondary coil of the transformer INT. The output conversion circuit 15 converts the high-frequency AC power output from the transformer INT into DC output power suitable for arc machining by the rectifier circuit DR2 and the DC reactor DCL.

  The output line L4 is connected to the torch TH, the output line L5 is connected to the workpiece M, and the output line L4 is connected to the workpiece M based on the output power supplied to the torch TH. An arc is generated, and arc processing such as arc welding and arc cutting of the workpiece M is performed. The output power is adjusted by controlling the switching of the inverter circuit 13 by the control circuit 21.

  The control circuit 21 performs switching control in which the inverter circuit 13 and the auxiliary switching circuit 14 are linked. That is, the power supply device 11 is provided with a detection sensor (not shown) that detects the actual value of the output voltage and output current at each time, and the control circuit 21 changes the value based on the detected value (actual value). Switching control is performed to obtain suitable output power.

The control circuit 21 includes a deviation calculation unit 22, a control switching unit 23, a pulse width calculation unit 24, and a phase difference calculation unit 25.
The deviation calculation unit 22 calculates the deviation X between the target value and the actual value from time to time. Based on the magnitude of the deviation X from the actual value, the control switching unit 23, as shown in FIG. 3, is a region where the deviation X is large with a predetermined value Xa as a boundary, that is, when a small to large output is requested. The switching control of the inverter circuit 13 is pulse width modulation control (PWM control). In this case, the pulse width calculation unit 24 calculates the on-pulse width Wm of the switching elements TR1 and TR2 of the inverter circuit 13 based on the deviation X from the actual value calculated by the deviation calculation unit 22, and based on this The on-pulse width Ws of the switching elements TR3 and TR4 of the auxiliary switching circuit 14 is calculated. When the deviation X from the actual value increases, the on-pulse widths Wm and Ws are set wide, and when the deviation X from the actual value decreases, the on-pulse widths Wm and Ws are set narrow. When the deviation X from the actual value reaches a predetermined value Xa that is a lower limit value during PWM control, the on-pulse widths Wm and Ws are set to the minimum pulse widths Wm0 and Ws0.

  Here, at the time of this PWM control, the switching elements TR3 and TR4 of the auxiliary switching circuit 14 are turned on simultaneously with the switching elements TR1 and TR2 of the inverter circuit 13 (phase difference is zero). The switching elements TR1 and TR2 are turned off prior to turning off. In other words, the on-pulse of the switching elements TR1 and TR2 of the inverter circuit 13 coincides with the rising edge, but the auxiliary switching is performed so that the falling edge is advanced for a predetermined time (so that the auxiliary capacitors C3 and C4 are sufficiently or completely discharged). The on-pulse width Ws of the switching elements TR3 and TR4 of the circuit 14 is set narrower than the previous on-pulse width Wm.

  Therefore, when the deviation X from the actual value becomes small and the on-pulse widths Wm and Ws become narrower, the switching elements TR3 and TR4 of the auxiliary switching circuit 14 in which the on-pulse is set to be narrower can be sufficiently turned on. There is a concern. In the present embodiment, in consideration of this, the lower limit minimum pulse width Ws0 at which the switching elements TR3 and TR4 can be sufficiently turned on is set, and the on pulse width Wm of the corresponding switching elements TR1 and TR2 is set to the minimum pulse width Wm0. A predetermined value Xa is set as the lower limit value of the control.

  Therefore, in a region where the deviation X from the actual value is smaller than the predetermined value Xa, that is, when a minimum output is requested, the control switching unit 23 changes the switching control of the inverter circuit 13 from PWM control to phase shift control (PSM control). Switch. In this case, the switching elements TR1 and TR2 of the inverter circuit 13 are the reference phase, and the switching elements TR3 and TR4 of the auxiliary switching circuit 14 are the control phase. The phase difference calculation unit 25 shifts the phase difference α that shifts the control pulse signal on the control phase side to the advance side with respect to the control pulse signal on the reference phase side in order to speed up the on / off of the switching elements TR3 and TR4 on the control phase side. Calculation is based on the deviation X. Then, as the deviation X from the actual value decreases from the predetermined value Xa, the phase difference α of the control pulse signal on the control phase side with respect to the reference phase side is set to gradually increase from zero (during PWM control), The maximum phase difference αx is set. The pulse width calculation unit 24 fixes the on pulse widths Wm and Ws of the switching elements TR1 and TR2 of the inverter circuit 13 and the switching elements TR3 and TR4 of the auxiliary switching circuit 14 to the minimum pulse widths Wm0 and Ws0.

  Thereby, the switching elements TR3 and TR4 on the control phase side are shifted to the advance side by the phase difference α while the ON pulses of the switching elements TR1 to TR4 are kept at the minimum pulse widths Wm0 and Ws0 that can be sufficiently turned on. The minimum output is adjusted by adjusting the simultaneous on-time with the phase-side switching elements TR1 and TR2. Further, since the shift is made to the advance side, the switching elements TR3 and TR4 of the auxiliary switching circuit 14 are maintained to be turned off before the switching elements TR1 and TR2 of the inverter circuit 13 are turned off even during the PSM control. Similarly to the PWM control, the soft switching by the auxiliary switching circuit 14 is continuously performed.

  Next, various controls of the control circuit 21 of the present embodiment will be described with reference to FIG. 2 showing voltage and current waveforms at various points of the power supply device 11. 2A to 2C each show one control cycle, and a half cycle in which the switching elements TR1 and TR3 are operated will be described by subdividing into periods t1 to t10. For the periods t1 to t10, only numbers are shown in the lower part of FIG. Further, TR1 to TR4 (VGE) in FIG. 2 are control pulse signals (gate voltages) output to the switching elements TR1 to TR4. In FIG. 2, C3 and C4 (V) are the voltages between the terminals of the auxiliary capacitors C3 and C4, TR1 (VCE) and TR3 (VCE) are the voltages between the terminals of the switching elements TR1 and TR3, TR1 (Ic) and TR3 (Ic). Is a current flowing through the switching elements TR1 and TR3. INT (I) is a current flowing through the primary coil of the transformer INT.

[PWM control]
FIG. 2A shows a case where a request for a large output is made, and a case where the ON pulse width Wm of the switching element TR1 is set to continue from the period t2 to t9. The on-pulse width Ws of the switching element TR3 is set so as to continue from the period t2 to t8.

  Period t1: The switching elements TR1 and TR3 are turned off during the PWM control. At this time, the auxiliary capacitor C3 is in a charged state, and the inter-terminal voltage is the same voltage as the inter-terminal voltage of the smoothing capacitor C1 (half the inter-terminal voltage of the rectifier circuit DR1).

  Period t2: The switching element TR1 of the inverter circuit 13 and the switching element TR3 of the auxiliary switching circuit 14 are simultaneously turned on. At this time, since the rising of the current applied to the switching elements TR1 and TR3 from zero is slow due to the leakage inductance of the primary coil of the transformer INT, the switching elements TR1 and TR3 are zero or minimal current (hereinafter referred to as zero current). The switching loss is reduced. In the switching element TR3, the voltage between the terminals of the smoothing capacitor C1 and the auxiliary capacitor C3 is the same voltage, so that the switching element TR3 is turned on at zero or a minimal voltage (hereinafter referred to as zero voltage). Has been reduced. Then, based on the switching elements TR1 and TR3 being turned on, DC power from the smoothing capacitor C1 is supplied to the primary coil of the transformer INT via the switching element TR3 and the switching element TR1.

  Period t3 to t8: an ON period continued from the period t2 between the switching element TR1 of the inverter circuit 13 and the switching element TR3 of the auxiliary switching circuit 14. The DC power from the smoothing capacitor C1 is continuously supplied to the primary coil of the transformer INT. That is, the output power of the power supply device 11 generated after the secondary side of the transformer INT including the power supply from the auxiliary capacitor C3 in the subsequent period t9 becomes large.

  Period t9: The switching element TR3 of the auxiliary switching circuit 14 is turned off prior to the switching element TR1 of the inverter circuit 13. At this time, since the voltage between the terminals of the smoothing capacitor C1 and the auxiliary capacitor C3 is the same voltage, the switching element TR3 is turned off at zero voltage, and the switching loss is reduced. Although the supply of the DC power from the smoothing capacitor C1 to the subsequent stage is cut off based on the switching element TR3 being turned off, the supply of the DC power to the transformer INT is continued from the auxiliary capacitor C3 in the charged state. In the period t9, the inter-terminal voltage gradually decreases as the auxiliary capacitor C3 is discharged, and becomes zero or a minimum inter-terminal voltage by the next period t10. The current flowing through the primary coil of the transformer INT is maintained.

  Period t10: The switching element TR1 of the inverter circuit 13 is turned off. At this time, since the auxiliary capacitor C3 is discharged in the previous period t9, the switching element TR1 is turned off at zero voltage, and the switching loss is reduced. When the switching element TR1 is turned off, a return current passing through the return diode D2 is generated based on the electromagnetic energy accumulated in the primary coil (leakage inductance) of the transformer INT, and the auxiliary capacitor C4 is charged. By the end of the period t10, the voltage across the auxiliary capacitor C4 is charged to the same voltage as the voltage across the smoothing capacitor C2. The reflux current gradually decreases. If the electromagnetic energy accumulated in the primary coil (leakage inductance) of the transformer INT is insufficient, a reactor is inserted in series with the primary coil of the transformer INT.

  In this way, the half cycle in which the group of switching elements TR1 and TR3 operates is completed, and in the next half cycle, the group of switching elements TR2 and TR4 operates, and switching elements TR1 and TR2 are alternately turned on and off repeatedly.

  FIG. 2B shows a case where a request for a small output is made, and a case where PWM control at the criticality between PWM control and PSM control is performed. That is, the on-pulse width Wm of the switching element TR1 is set to the minimum pulse width Wm0 that continues from the period t2 to t4. The on-pulse width Ws of the switching element TR3 is set to the minimum pulse width Ws0 that continues from the period t2 to t3.

Period t1: The switching elements TR1 and TR3 are turned off. At this time, the auxiliary capacitor C3 is in a charged state.
Period t2: The switching element TR1 of the inverter circuit 13 and the switching element TR3 of the auxiliary switching circuit 14 are simultaneously turned on. The switching element TR1 is on at zero current, the switching element TR3 is on at zero current and zero voltage, and the switching loss is reduced. Based on the switching elements TR1 and TR3 being turned on, DC power from the smoothing capacitor C1 is supplied to the primary coil of the transformer INT.

  Period t3: an ON period continued from the period t2 between the switching element TR1 of the inverter circuit 13 and the switching element TR3 of the auxiliary switching circuit 14, and is a period shorter than the case of FIG. That is, the output power of the power supply device 11 generated after the secondary side of the transformer INT including the power supply from the auxiliary capacitor C3 in the subsequent period t4 is small.

  Period t4: The switching element TR3 of the auxiliary switching circuit 14 is turned off prior to the switching element TR1 of the inverter circuit 13. The switching element TR3 is turned off at zero voltage, and the switching loss is reduced. Based on the turning-off of the switching element TR3, the supply of DC power to the transformer INT is continued from the auxiliary capacitor C3 in the charged state. The auxiliary capacitor C3 is discharged.

  Period t5: The switching element TR1 of the inverter circuit 13 is turned off. At this time, the switching element TR1 is turned off at zero voltage due to the discharge of the auxiliary capacitor C3, and the switching loss is reduced. Further, a return current passing through the return diode D2 is generated, and the auxiliary capacitor C4 is charged.

Period t6 to t10: The switching elements TR1 and TR3 are kept off. As a result, no output power is generated in the period t6 to t10.
In this way, the half cycle in which the combination side of switching elements TR1 and TR3 operates ends, and in the next half period, the combination side of switching elements TR2 and TR4 operates.

  During this PWM control, the on-pulse width Wm of the switching elements TR1 and TR2 calculated based on the deviation X from the actual value is changed from the period t2 to t4 to the period t2 to t9, and the magnitude of the output power is changed. Adjusted. In conjunction with this, the on-pulse width Ws of the switching elements TR3 and TR4 is changed from the period t2 to t3 to the period t2 to t8. Even if the on-pulse widths Wm and Ws are set to the minimum pulse widths Wm0 and Ws0, the switching elements TR1 and TR2, particularly the switching elements TR3 and TR4 on the narrow side can be sufficiently turned on. If the minimum output is less than this, it is switched to PSM control.

[PSM control]
FIG. 2C shows a case where a request for minimum output is made, and a case where PSM control is performed. The on-pulse width Wm of the switching element TR1 of the inverter circuit 13 serving as the reference phase is set to the periods t2 to t4, and the on-pulse width Wm of the switching element TR3 of the auxiliary switching circuit 14 serving as the control phase is set to the periods t1 to t2. That is, while the ON pulses of the switching elements TR1 and TR3 both maintain the minimum pulse widths Wm0 and Ws0, the ON pulse on the switching element TR3 side is phase-shifted to the advancing side, causing a phase difference α.

  Period t1: Prior to turning on the switching element TR1 of the inverter circuit 13, the switching element TR3 of the auxiliary switching circuit 14 is turned on. The auxiliary capacitor C3 is in a charged state. Therefore, the switching element TR3 is on at zero current and zero voltage, and the switching loss is reduced.

  Period t2: The switching element TR1 of the inverter circuit 13 is turned on. At this time, the switching element TR1 is turned on at zero current due to the leakage inductance of the primary coil of the transformer INT, and the switching loss is reduced. Then, based on the switching element TR1 being turned on, the DC power from the smoothing capacitor C1 is supplied to the primary coil of the transformer INT via the switching element TR3 and the switching element TR1. The period during which both the switching elements TR1 and TR3 are on is only this period t2. Since the current supplied to the transformer INT also occurs in the subsequent periods t3 and t4, the period is the same as the PWM-PSM critical time in FIG. 2B, but the current peak value and average value become smaller. As a result, the output power of the power supply device 11 is minimized.

  Period t3: The switching element TR3 of the auxiliary switching circuit 14 is turned off prior to the switching element TR1 of the inverter circuit 13. The switching element TR3 is turned off at zero voltage, and the switching loss is reduced. Based on the switching element TR3 being turned off, the supply of the DC power to the transformer INT is continued from the auxiliary capacitor C3 in the charged state, and the auxiliary capacitor C3 is discharged.

Period t4: The switching element TR1 is on and the switching element TR3 is off. The auxiliary capacitor C3 is completely discharged.
Period t5: The switching element TR1 of the inverter circuit 13 is turned off. At this time, the switching element TR1 is turned off at zero voltage due to the discharge of the auxiliary capacitor C3, and the switching loss is reduced. At this time, a return current passing through the return diode D2 is generated and the auxiliary capacitor C4 is charged.

Period t6 to t10: The switching elements TR1 and TR3 are kept off. As a result, no output power is generated in the period t6 to t10.
In this way, the half cycle in which the combination side of switching elements TR1 and TR3 operates ends, and in the next half period, the combination side of switching elements TR2 and TR4 operates.

  In this PSM control, the on-pulse width Wm of the switching elements TR1 and TR2 and the on-pulse width Ws of the switching elements TR3 and TR4 are fixed at the minimum pulse widths Wm0 and Ws0, and each control based on the deviation X from the actual value. By changing the phase difference α of the pulse signal, the magnitude of the output power when the minimum output is requested is adjusted. Therefore, even if the output of the power supply device 11 is further reduced, the switching elements TR1 and TR2, particularly the switching elements TR3 and TR4 on the narrow side can still be sufficiently turned on.

  As described above, in the power supply device 11 according to the present embodiment, when a request is made from the small output to the large output where the deviation X from the actual value is larger than the predetermined value Xa, the inverter circuit 13 and the auxiliary switching associated therewith. PWM control for adjusting the on-pulse widths Wm and Ws is performed on the circuit 14. On the other hand, when a request for an output minimum that is smaller than the predetermined value Xa is made, PSM control using on-pulses with minimum pulse widths Wm0 and Ws0 during PWM control is performed on the inverter circuit 13 and the auxiliary switching circuit 14. It has come to be. As a result, even when the output is minimally required, the switching elements TR1 and TR2 of the inverter circuit 13, particularly the switching elements TR3 and TR4 of the auxiliary switching circuit 14 in which the ON pulse is narrowed can be reliably turned on. Problems such as magnetism are suppressed.

Next, characteristic effects of the present embodiment will be described.
(1) When the output request is large, PWM control is performed to adjust the on-pulse widths Wm and Ws of each control pulse signal output to the inverter circuit 13 and the auxiliary switching circuit 14 linked to the inverter circuit 13 and the output request is small. At times, the inverter circuit 13 and the auxiliary switching circuit 14 can be switched to PSM control for adjusting the mutual phase difference α of the control pulse signals that are paired. That is, if PWM control is performed as it is when a low output is required, an event may occur in which the switching elements TR1 to TR4 of the inverter circuit 13 and the auxiliary switching circuit 14 cannot be turned on. Therefore, when a low output is required, switching to PSM control is performed, and the current peak is adjusted by phase adjustment in a state in which the on-pulse widths Wm and Ws of each control pulse signal are secured, in this embodiment, fixed to the minimum pulse widths Wm0 and Ws0 that can be turned on. The value / average value is reduced and the output is reduced. As a result, the switching elements TR1 to TR4 of the inverter circuit 13 and the auxiliary switching circuit 14 can be reliably turned on even when a low output is required, so that a stable output can be obtained.

  (2) The on-pulse widths Wm and Ws are switched from PWM control to PSM control with the minimum pulse widths Wm0 and Ws0 as the boundary. At the time of PSM control, the switching elements TR1 to TR4 are sufficiently turned on to have the minimum pulse widths Wm0 and Ws0. The phase of each control pulse signal is adjusted in a fixed state. As a result, the switching elements TR1 to TR4 of the inverter circuit 13 and the auxiliary switching circuit 14 are reliably turned on by inheriting the minimum pulse widths Wm0 and Ws0 when switching from PWM control and switching to PSM control. In addition to stabilizing the output, it is possible to stabilize the output when the control is switched.

  (3) During PSM control, the control pulse signal output to the auxiliary switching circuit 14 is shifted to the advance side with respect to the control pulse signal output to the inverter circuit 13. As a result, the soft switching operation in which the switching elements TR1 and TR2 of the inverter circuit 13 are turned off after the switching elements TR3 and TR4 of the auxiliary switching circuit 14 are turned off can be continued even during the PSM control, thereby reducing the switching loss. Can contribute.

  (4) During PSM control, the control pulse signal output to the inverter circuit 13 is fixed, and the control pulse signal output to the auxiliary switching circuit 14 is shifted. As a result, the phase adjustment can be easily performed because only one control pulse signal needs to be phase-adjusted.

  (5) During PSM control, a period from when the switching elements TR3 and TR4 of the auxiliary switching circuit 14 are turned off to when the switching elements TR1 and TR2 of the inverter circuit 13 are turned off (a period during which only the switching elements TR1 and TR2 are turned on) If the length becomes longer, useless reflux current may be generated on the primary side. However, in this embodiment, since the ON pulse width Wm of the switching elements TR1 and TR2 at the time of PSM control is set to the minimum pulse width Wm0, generation of unnecessary return current can be prevented, and conduction loss is reduced when the return current is generated. Power saving can be achieved. Further, in the arc machining power supply device 11 as in the present embodiment, since a large output current can be generated at the time of low output, the time during which the return current is generated tends to be long. Since it can be effectively reduced, it is significant to apply to the arc machining power supply device 11 as in the present embodiment.

In addition, you may change embodiment of this invention as follows.
In the PSM control of the above embodiment, the control pulse signal output to the switching elements TR1 and TR2 of the inverter circuit 13 is fixed, and the control pulse signal output to the switching elements TR3 and TR4 of the auxiliary switching circuit 14 is shifted forward. However, it may be changed as appropriate.

  For example, as shown in FIG. 4, during PSM control, the control pulse signal output to the switching elements TR1 and TR2 of the inverter circuit 13 is fixed, and the control pulse signal output to the switching elements TR3 and TR4 of the auxiliary switching circuit 14 is delayed. You may shift to the side. In this way, phase adjustment is easy because only one control pulse signal needs to be adjusted.

  Further, as shown in FIG. 5, the control pulse signal output to the switching elements TR3 and TR4 of the auxiliary switching circuit 14 is fixed, and the control pulse signal output to the switching elements TR1 and TR2 of the inverter circuit 13 is shifted to the delay side. Also good. That is, as in the above embodiment, the control pulse signal output to the auxiliary switching circuit 14 is relatively shifted to the advance side with respect to the control pulse signal output to the inverter circuit 13. Even in this case, the soft switching operation can be continued during the PSM control.

  In this PSM control, one side of each control pulse signal of the inverter circuit 13 and the auxiliary switching circuit 14 is fixed and the other side is shifted, but both may be relatively shifted. In this case, when a continuous soft switching operation is expected even during PSM control, the control pulse signal output to the auxiliary switching circuit 14 is relatively shifted to the advance side with respect to the control pulse signal output to the inverter circuit 13. Is preferred.

Furthermore, the above various modes for shifting the control pulse signals of the inverter circuit 13 and the auxiliary switching circuit 14 may be combined and changed during the control.
In the above-described embodiment, the minimum pulse widths Wm0 and Ws0 are used as the predetermined narrow pulse width used for switching determination from the PWM control to the PSM control. However, a narrow pulse width that is somewhat narrower than the minimum may be used. . Further, switching between PWM control and PSM control may be performed with a pulse other than the on-pulse widths Wm and Ws of the control pulse signal. For example, the control may be switched based on an output set value (target value) at which the user of the arc machine sets the output. Specifically, the PWM control is performed when the output is set from large to small, and the control is switched to PSM control when the output is set to the minimum.

  -You may change suitably the structure of the power supply device 11 of the said embodiment. For example, although the output conversion circuit 15 is configured by the rectifier circuit DR2 and the DC reactor DCL, it may be appropriately changed according to the load. Further, although the DC conversion circuit 12 that converts AC input power from a commercial power source into DC power is used, it may be omitted if the input is DC power, or may be a voltage conversion circuit or the like.

  -Although the power supply device 11 of the said embodiment was a power supply device for arc processing, another power supply device may be sufficient.

11 Arc machining power supply (power supply)
13 Inverter circuit 14 Auxiliary switching circuit 15 Output conversion circuit 21 Control circuit (pulse width modulation control means, phase shift control means, control switching means)
23 Control switching part (control switching means)
24 Pulse width calculation unit (pulse width modulation control means)
25 Phase difference calculation unit (phase shift control means)
L1-L3 Power line C3, C4 Auxiliary capacitor INT Transformer TR1, TR2 Switching element (inverter circuit)
TR3, TR4 Switching element (auxiliary switching circuit)
Wm, Ws On pulse width Wm0, Ws0 Minimum pulse width (predetermined narrow pulse width)
α phase difference

Claims (8)

A half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off and converts input DC power into high-frequency AC power, and a switching operation of the inverter circuit provided on a power supply line before the inverter circuit, An auxiliary switching circuit having a switching element that operates in conjunction and an auxiliary capacitor connected between power supply lines at the subsequent stage of the element;
Output control for adjusting the output power to the load by controlling the switching operation of the inverter circuit and the auxiliary switching circuit linked to the inverter circuit, and the switching element of the auxiliary switching circuit is turned off first and then turned off later. A power supply device configured to perform soft switching control including an operation of reducing a switching loss of a switching element of the inverter circuit,
Adjusting the on-pulse width of the control pulse signal output to the switching element of the inverter circuit, and adjusting the on-pulse width of the control pulse signal output to the switching element of the auxiliary switching circuit according to this,
Phase shift control means for adjusting a mutual phase difference between control pulse signals paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit;
A power supply apparatus comprising: the pulse width modulation control means when the output request is large; and the control switching means for switching to the phase shift control means when the output request is small. The power supply device according to claim 1,
The control switching means performs switching determination between the pulse width modulation control means and the phase shift control means using on-pulse widths of the switching elements of the inverter circuit and the auxiliary switching circuit, and the inverter circuit and When an output request is made such that each switching element of the auxiliary switching circuit is set to the on-pulse width that is larger than a predetermined narrow pulse width that can be sufficiently turned on, the pulse width modulation control means is used, and the on-pulse width is the predetermined narrow pulse. A power supply apparatus characterized by switching to the phase shift control means for adjusting the phase of the control pulse signal in a state where the on-pulse width is fixed to the predetermined narrow pulse width when an output request that can be smaller than the width is made. A half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off and converts input DC power into high-frequency AC power, and a switching operation of the inverter circuit provided on a power supply line before the inverter circuit, An auxiliary switching circuit having a switching element that operates in conjunction and an auxiliary capacitor connected between power supply lines at the subsequent stage of the element;
Output control for adjusting the output power to the load by controlling the switching operation of the inverter circuit and the auxiliary switching circuit linked to the inverter circuit, and the switching element of the auxiliary switching circuit is turned off first and then turned off later. A power supply device configured to perform soft switching control including an operation of reducing a switching loss of a switching element of the inverter circuit,
Adjusting the on-pulse width of the control pulse signal output to the switching element of the inverter circuit, and adjusting the on-pulse width of the control pulse signal output to the switching element of the auxiliary switching circuit according to this,
Phase shift control means for adjusting a mutual phase difference between control pulse signals paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit;
Control switching means for switching to the pulse width modulation control means when the output request is large, and switching to the phase shift control means when the output request is small;
With
The phase shift control means shifts the control pulse signal output to the auxiliary switching circuit to a relatively advanced side relative to the control pulse signal output to the inverter circuit. A half-bridge type inverter circuit that performs a switching operation in which switching elements are alternately turned on and off and converts input DC power into high-frequency AC power, and a switching operation of the inverter circuit provided on a power supply line before the inverter circuit, An auxiliary switching circuit having a switching element that operates in conjunction and an auxiliary capacitor connected between power supply lines at the subsequent stage of the element;
Output control for adjusting the output power to the load by controlling the switching operation of the inverter circuit and the auxiliary switching circuit linked to the inverter circuit, and the switching element of the auxiliary switching circuit is turned off first and then turned off later. A power supply device configured to perform soft switching control including an operation of reducing a switching loss of a switching element of the inverter circuit,
Adjusting the on-pulse width of the control pulse signal output to the switching element of the inverter circuit, and adjusting the on-pulse width of the control pulse signal output to the switching element of the auxiliary switching circuit according to this,
Phase shift control means for adjusting a mutual phase difference between control pulse signals paired by the switching element of the inverter circuit and the switching element of the auxiliary switching circuit;
Control switching means for switching to the pulse width modulation control means when the output request is large, and switching to the phase shift control means when the output request is small;
With
The phase shift control means fixes one side of the control pulse signal output to the inverter circuit and the control pulse signal output to the auxiliary switching circuit, and shifts the other side. The power supply device according to claim 3 or 4,
The control switching means includes the pulse width modulation control means at the time of an output request such that each switching element of the inverter circuit and the auxiliary switching circuit is set to the on-pulse width that is larger than a predetermined narrow pulse width that can be sufficiently turned on. When the output request is such that the on-pulse width can be smaller than the predetermined narrow pulse width, switching to the phase shift control means for adjusting the phase of the control pulse signal in a state where the on-pulse width is fixed to the predetermined narrow pulse width. A power supply characterized by. The power supply device according to claim 2 or 5,
The predetermined narrow pulse width is set to a minimum pulse width at which each switching element of the inverter circuit and the auxiliary switching circuit can be turned on. The power supply device according to any one of claims 1 to 6 ,
A transformer that adjusts the voltage of the high-frequency AC power generated by the inverter circuit and outputs it to the secondary side, and an output conversion circuit that converts the high-frequency AC power that has been voltage-controlled through the transformer into output power corresponding to the load A power supply device comprising: An arc machining power supply device configured to generate output power for arc machining using the power supply device according to any one of claims 1 to 7 .