JP2016144303A - Electric power supply and electric power supply for welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power supply and an electric power supply for welding, capable of compensating variation of an on-pulse width of a driving signal and suitably suppressing generation of bias magnetism.SOLUTION: An electric power supply 10 comprises a control part 30 that generates driving signals S1 to S4 for controlling a switching operation of switching elements TR1 to TR4 in an inverter circuit 12. The control part 30 includes: a control circuit 33 that generates command values Fa and Fb for setting an on-pulse width of the driving signals S1 to S4; a driving circuit 34 that outputs the driving signals S1 to S4 each having the on-pulse width based on the command values Fa and Fb to the switching elements TR1 to TR4; and a pulse width measurement circuit 32 that measurements the pulse width of a pulse signal Pu corresponding to the driving signals S1 to S4. The control circuit 33 corrects the command values Fa and Fb on the basis of a comparison result of the pulse width measured in a pulse width measurement circuit 32 and the command values Fa and Fb.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply device and a welding power supply device.

  For example, a power supply device used for an arc welding machine has an inverter circuit (switching power supply circuit) using a switching element, and once converts DC power into high-frequency AC power, and generates desired output power on the secondary side via a transformer. It is the composition to do. In such a power supply device, a drive signal for switching control (on / off control) of the switching element is generated using an element such as a transistor or a photocoupler. However, the switching speeds of elements such as transistors and photocouplers vary from individual to individual. Due to the variation in the switching speed, the on-pulse width of the drive signal supplied to the switching element varies. Then, the balance of the inverter control is lost, and a phenomenon called a demagnetization in which the magnetic flux of the transformer is biased to one side polarity occurs. When such a bias magnetism occurs, an excessive current flows through the switching element of the inverter circuit in charge of the polarity on one side, and this switching element generates heat abnormally and may be damaged in the worst case.

  Therefore, a variable resistor is provided between the photocouplers, and by adjusting the resistance value of the variable resistor, the signal transmission time difference between the drive signals due to the switching speed variation is adjusted, and the on-pulse width of the drive signal There has been proposed a technique for reducing the variation of the above (for example, see Patent Document 1).

Japanese Patent Publication No. 6-32858

  However, characteristics such as a switching speed in an element such as a transistor or a photocoupler vary depending on a use environment (for example, use temperature), a use time, and the like. For this reason, in the conventional power supply device, it is necessary to manually adjust the resistance value of the variable resistor every time the usage environment changes, and there is a problem that the adjustment work is complicated.

Such a problem also occurs in power supply devices other than the arc welding power supply device having a transformer.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power supply device and a welding power supply that can easily compensate for variations in the on-pulse width of the drive signal and can suitably suppress the occurrence of magnetic bias. To provide an apparatus.

  A power supply device that solves the above problems is provided on the primary side of a transformer, and generates an RF circuit from a DC voltage by the operation of a switching element that constitutes a bridge circuit, and a desired output on the secondary side of the transformer. A control unit that generates a drive signal for controlling a switching operation of the switching element so as to generate electric power, wherein the control unit sets a command value for setting an on-pulse width of the drive signal. A control circuit for generating, a drive circuit for outputting the drive signal having a pulse width based on the command value to the switching element, and a pulse width measurement circuit for measuring a pulse width of the pulse signal corresponding to the drive signal, And the control circuit determines the command value based on a comparison result between the pulse width measured by the pulse width measurement circuit and the command value. Configured to forward to.

  According to this configuration, the pulse width of the pulse signal corresponding to the drive signal is measured, and the command value is corrected based on the comparison result between the pulse width and the command value. At this time, the pulse width of the pulse signal is a pulse width corresponding to the on-pulse width of the drive signal. Therefore, the comparison result between the pulse width of the pulse signal and the command value reflects the characteristic variation of the elements in the drive circuit. By correcting the command value based on such a comparison result, the influence due to the characteristic variation can be reduced, and the on-pulse width variation of the drive signal can be compensated. As a result, it is possible to suppress the occurrence of magnetic bias in the transformer. Further, since the command value can be corrected by an internal calculation of the control circuit, manual adjustment is not required, and the on-pulse width of the drive signal can be easily compensated.

  The power supply device further includes a current detector that detects an input current input to the primary side of the transformer, and the control unit performs full-wave rectification on the detection signal acquired by the current detector, A signal processing circuit that outputs the pulse signal generated by waveform shaping of the rectified signal to the pulse width measurement circuit, the control circuit based on the pulse width measured by the pulse width measurement circuit, It is preferable that a first pulse width corresponding to the ON time of the switching element is calculated, and a difference between the first pulse width and the command value is superimposed on the command value.

  According to this configuration, the command value is corrected by superimposing the difference between the first pulse width corresponding to the ON time of the switching element and the command value on the command value. At this time, the difference between the first pulse width and the command value reflects the characteristic variation of the switching element as well as the characteristic variation of the element in the drive circuit. Therefore, by correcting the command value based on the difference, the influence due to the characteristic variation of the switching element can be reduced together with the influence due to the characteristic variation of the element in the drive circuit.

  In the power supply apparatus, the pulse width measurement circuit inputs the drive signal as the pulse signal, and the control circuit is configured to turn on the drive signal based on the pulse width measured by the pulse width measurement circuit. It is preferable that a second pulse width corresponding to the width is calculated, and a difference between the second pulse width and the command value is superimposed on the command value.

  According to this configuration, the command value is corrected by superimposing the difference between the second pulse width corresponding to the on-pulse width of the drive signal and the command value on the command value. Thereby, the command value can be suitably corrected so as to compensate for the characteristic variation of the elements in the drive circuit.

  The power supply apparatus further includes a current detector that detects an input current input to the primary side of the transformer, and the control unit inputs the drive signal and the detection signal acquired by the current detector. When the detection signal is 0A, the drive signal is output to the pulse width measurement circuit as the pulse signal, while when the detection signal is other than 0A, the detection signal is full-wave rectified, A signal processing circuit is provided that outputs a signal obtained by waveform shaping of the signal after full-wave rectification as the pulse signal to the pulse width measurement circuit.

  According to this configuration, the command value can be corrected using the drive signal as the pulse signal during a period in which the detection signal is 0 A and the command value cannot be corrected using the detection signal.

Further, in the power supply device, the control circuit corrects the command value constantly or intermittently when the power supply device is turned on.
According to this configuration, even when the characteristic variation of the element in the drive circuit changes due to a change in usage environment, usage time, etc., the above characteristic variation changes constantly or intermittently when the power is turned on. In addition, the command value can be corrected.

Moreover, the power supply apparatus for welding which solves the said subject is comprised so that the output electric power for welding may be produced | generated using the said power supply apparatus.
According to this configuration, it is possible to easily compensate for the variation in the on-pulse width of the drive signal in the welding power source device that generates the output power for welding, and it is possible to favorably suppress the occurrence of magnetic bias.

  According to the power supply device and the welding power supply device of the present invention, it is possible to easily compensate for the variation in the on-pulse width of the drive signal, and to suitably suppress the occurrence of magnetic bias.

It is a block diagram of the power supply apparatus for welding in one Embodiment. It is a block diagram of the signal processing circuit in one Embodiment. It is a block diagram of the pulse width measurement circuit in one Embodiment. It is a flowchart which shows operation | movement of the power supply apparatus for welding in one Embodiment. It is a wave form diagram which shows operation | movement of the power supply apparatus for welding in one Embodiment. It is a block diagram of the control part of the power supply device for welding in a modification. It is a block diagram of the control part of the power supply device for welding in a modification.

Hereinafter, an embodiment of a power supply device (welding power supply device) will be described.
As shown in FIG. 1, the power supply device 10 of the present embodiment is an arc welding power supply device including a primary side conversion circuit 11, an inverter circuit 12, a welding transformer INT, and a secondary side conversion circuit 13. The power supply device 10 generates DC output power suitable for arc welding from three-phase AC input power supplied from a commercial power supply.

  The primary side conversion circuit 11 includes a rectifier circuit DR1 formed of a diode bridge circuit, and a smoothing capacitor C1 connected between output terminals of the rectifier circuit DR1. The primary side conversion circuit 11 once converts the three-phase AC input power into DC power and outputs the DC power to the inverter circuit 12.

  The inverter circuit 12 is configured by a full bridge circuit using semiconductor switching elements TR1 to TR4 such as IGBT (Insulated Gate Bipolar Transistor). Specifically, the switching element TR1 is disposed on the first upper arm, the switching element TR2 is disposed on the first lower arm, the switching element TR3 is disposed on the second upper arm, and the switching element TR4 is disposed on the second lower arm. An output terminal a of the inverter circuit 12 between the switching elements TR1 and TR2 and an output terminal b of the inverter circuit 12 between the switching elements TR3 and TR4 are connected to the primary coil L1 of the transformer INT.

  In the inverter circuit 12, the switching elements TR1 and TR4 form a pair, the switching elements TR2 and TR3 form a pair, and each pair performs switching operation alternately, thereby converting the DC power input from the primary side conversion circuit 11 into a high-frequency alternating current. It is converted into electric power and supplied to the primary coil L1 of the transformer INT. When the switching elements TR1 and TR4 are in the ON state, a positive voltage is applied to the primary coil L1, and the input current Ia input to the primary coil L1 flows from the output terminal a toward the primary coil L1 to be positive. It becomes the value of. On the other hand, when the switching elements TR2 and TR3 are in the ON state, a negative voltage is applied to the primary side coil L1, and the input current Ia flows from the primary side coil L1 toward the output terminal a to become a negative value. When all the switching elements TR1 to TR4 are in the off state, the input current Ia is 0A. Switching operations of these switching elements TR1 to TR4 are performed based on drive signals S1 to S4 input from the control unit 30.

  On the secondary side of the transformer INT, the high-frequency AC power generated by the inverter circuit 12 is converted into a predetermined voltage and output from the secondary coil L2. The secondary side conversion circuit 13 is connected to the secondary side coil L2.

  The secondary side conversion circuit 13 includes a secondary side rectifier circuit DR2 and a direct current reactor DCL. The secondary side rectifier circuit DR2 is composed of a full-wave rectifier circuit using a pair of diodes, the anodes of the respective diodes are respectively connected to both side terminals of the secondary side coil L2, and the cathodes of the respective diodes are both ends of the DC reactor DCL. It is connected to the. The other end of the DC reactor DCL is connected to the positive output terminal o1 of the power supply device 10. The negative output terminal o2 of the power supply device 10 is connected to the intermediate terminal of the secondary coil L2. Such a secondary side conversion circuit 13 converts the high frequency AC power from the secondary side coil L2 of the transformer INT into DC output power of arc welding and outputs it from the output terminals o1 and o2. Then, the welding torch TH is connected to the positive output terminal o1 of the power supply device 10, the welding object M is connected to the negative output terminal o2, and the electrodes of the welding torch TH are generated based on the DC output power generated by the power supply device 10. An arc is generated between the welding object M and the welding object M, and arc welding of the welding object M is performed.

  The power supply device 10 includes a control unit 30 including a CPU (Central Processing Unit) and the like. A detection signal Ib corresponding to the input current Ia is input to the control unit 30 from the output terminal of the inverter circuit 12, that is, the current detector 21 installed on the primary side of the transformer INT. Further, the detection signal Id corresponding to the output current Io of the power supply device 10 is input to the control unit 30 from the current detector 22 installed on the output-side power supply line of the power supply device 10. A detection signal Vd corresponding to the output voltage Vo of the power supply device 10 is input to the control unit 30 from the voltage detector 23 installed between the output side power supply lines of the power supply device 10. Incidentally, the current detectors 21 and 22 are, for example, Hall type current sensors using Hall elements.

  The control unit 30 determines the actual values of the input current Ia and the output current Io obtained from the input detection signals Ib and Id, the actual value of the output voltage Vo obtained from the input detection signal Vd, the target value thereof, and the like. Based on the various parameters that are included, internal calculations are performed for appropriate output from time to time. Control unit 30 generates drive signals S1 to S4 for switching control of switching elements TR1 to TR4, respectively, based on the internal calculation result. The control unit 30 includes a signal processing circuit 31, a pulse width measurement circuit 32, a control circuit 33, and a drive circuit 34.

  A detection signal Ib corresponding to the input current Ia is input from the current detector 21 to the signal processing circuit 31. Similar to the input current Ia, the detection signal Ib takes a positive value during the on-time of the switching elements TR1 and TR4 and takes a negative value during the on-time of the switching elements TR2 and TR3 (see FIG. 5). Based on the detection signal Ib, the signal processing circuit 31 has a pulse signal Pu having a pulse width corresponding to the on-time of the switching elements TR1 and TR4 and a pulse width pulse corresponding to the on-time of the switching elements TR2 and TR3. Is generated.

  As shown in FIG. 2, the signal processing circuit 31 includes a full wave rectification circuit 41 connected to the secondary side of the current detector 21 and a waveform shaping circuit 42 connected to the output terminal of the full wave rectification circuit 41. I have.

  The full-wave rectifier circuit 41 is configured by a bridge circuit using four diodes D1 to D4. The output terminal of the current detector 21 is connected between the diodes D1 and D2 and between the diodes D3 and D4. Specifically, one output terminal of the current detector 21 is connected to the anode of the diode D1 and the cathode of the diode D2, and the other output terminal of the current detector 21 is connected to the anode of the diode D3 and the cathode of the diode D4. It is connected. The anodes of the diodes D2 and D4 are connected to the ground. Then, the full wave rectification circuit 41 performs full wave rectification on the detection signal Ib detected by the current detector 21 and supplies the rectified signal to the waveform shaping circuit 42.

  The waveform shaping circuit 42 includes resistors R1 and R2, a diode D5, a capacitor C2, a comparator 43, a reference power supply E1, a pull-up resistor R3, and an inverting circuit 44. The resistor R1, the diode D5, and the capacitor C2 are connected in parallel between the output terminals of the full-wave rectifier circuit 41, that is, between the cathodes of the diodes D1 and D3 and the anodes of the diodes D2 and D4.

  The cathodes of the diodes D1 and D3 are connected to the inverting input terminal of the comparator 43. A reference power source E1 is connected to the non-inverting input terminal of the comparator 43 via a resistor R2, and a reference voltage generated by the reference power source E1 is input. The output terminal of the comparator 43 is connected to the pull-up resistor R3 and the inverting circuit 44. The waveform shaping circuit 42 shapes the signal after the full-wave rectification to generate a pulse signal Pu, and outputs the pulse signal Pu from the inverting circuit 44. Here, as shown in FIG. 5, the pulse signal Pu includes a pulse Pm (for example, pulses P1, P3, P5, P7) having a pulse width corresponding to the ON time of the switching elements TR1, TR4, and the switching elements TR2, TR3. Pulse Pm (for example, P2, P4, P6, P8) having a pulse width corresponding to the ON time. In other words, the pulse signal Pu becomes H level (for example, high potential power supply voltage level) corresponding to the period when the switching elements TR1 and TR4 are turned on and the period when the switching elements TR2 and TR3 are turned on. It becomes L level (for example, ground level) corresponding to a period in which all of TR4 is turned off.

  By the signal processing (that is, full-wave rectification and waveform shaping) by the signal processing circuit 31 described above, a pulse signal Pu having a stable rectangular pulse can be generated from the detection signal Ib.

  The pulse width measuring circuit 32 shown in FIG. 3 receives the pulse signal Pu from the signal processing circuit 31, and measures the pulse width of the pulse Pm included in the pulse signal Pu. The pulse width measurement circuit 32 includes a counter 51 and a crystal oscillator 52. The counter 51 counts the clock signal CK input from the crystal oscillator 52 during the period when the pulse signal Pu from the signal processing circuit 31 is at the H level, that is, the period when the pulse Pm is generated. The counter 51 outputs a count value Nm corresponding to the pulse width of the pulse Pm to the control circuit 33. The frequency of the clock signal CK can be about 40 MHz, for example, and the period T of the clock signal CK can be about 25 ns, for example.

  The control circuit 33 inputs the count value Nm from the pulse width measurement circuit 32, the detection signal Id from the current detector 22, and the detection signal Vd from the voltage detector 23. The control circuit 33 performs PWM control as the switching control of the inverter circuit 12, and based on the detection signals Id and Vd, the drive signals S1 to S1 such that the on-duty of the switching elements TR1 to TR4 is appropriate from time to time. The on-pulse width is set (calculated) in S4. Specifically, the control circuit 33 sets the on-pulse width of the drive signals S1 to S4 to be long when the output power is increased at that time, while the drive signal S1 to S1 when the output power is decreased. Command values Fa and Fb for setting the on-pulse width of S4 to be short are generated.

  The drive circuit 34 generates drive signals S1 and S4 having an on-pulse width based on the command value Fa, and generates drive signals S2 and S3 having an on-pulse width based on the command value Fb. The drive circuit 34 supplies drive signals S1 to S4 to the switching elements TR1 to TR4, respectively. The drive circuit 34 includes a plurality of photocouplers 34A (here, four as many as the switching elements TR1 to TR4) that output the driving signals S1 to S4 to the switching elements TR1 to TR4, respectively.

  By the way, if there are variations in characteristics (for example, switching speed) of the photocoupler 34A and the switching elements TR1 to TR4 in the drive circuit 34, the on-pulse width (command value) of the drive signals S1 to S4 specified by the command values Fa and Fb. ) And a period (actual value) in which the switching elements TR1 to TR4 are actually turned on may occur. Due to such a difference, when the difference between the on-time of the switching elements TR1 and TR4 and the on-time of the switching elements TR2 and TR3 becomes large, a magnetic demagnetization in which the magnetic flux of the transformer INT is biased to the polarity on one side occurs.

  Therefore, the control circuit 33 of the present embodiment performs actual driving signals S1 to S4 based on the comparison result between the command values Fa and Fb and the pulse widths Wa and Wb (see FIG. 5) obtained from the count value Nm. The command values Fa and Fb are corrected so that the on-pulse width becomes a desired pulse width. Then, the drive circuit 34 generates drive signals S1 to S4 having on-pulse widths based on the corrected command values Fa and Fb. Here, the pulse width Wa corresponds to the on-time (actual value) of the switching elements TR1 and TR4, and the pulse width Wb corresponds to the on-time (actual value) of the switching elements TR2 and TR3. By correcting the command values Fa and Fb based on the difference between the pulse widths Wa and Wb (actual values) and the command values Fa and Fb, the influence due to the characteristic variation of the photocoupler 34A and the switching elements TR1 to TR4 is affected. Can be reduced. Thereby, the ON time of the switching elements TR1 and TR4 can be brought close to the command value Fa before correction, and the ON time of the switching elements TR2 and TR3 can be brought close to the command value Fb before correction. Therefore, the difference between the on-time of switching elements TR1 and TR4 and the on-time of switching elements TR2 and TR3 can be reduced. That is, it is possible to compensate for variations in the on-time of the switching elements TR1 and TR4 and the on-time of the switching elements TR2 and TR3. As a result, it is possible to suppress the occurrence of magnetic bias in the transformer INT.

Next, the operation of the power supply device 10 will be described with reference to FIGS.
In step ST1 shown in FIG. 4, when the power supply 10 is turned on, the control unit 30 executes an initialization process for initializing various variables. In this example, the control unit 30 sets the number n of pulses Pm necessary for calculating the pulse widths Wa and Wb to 8, and sets the count value Nm of the mth pulse Pm (m is an integer) to “0”. And the variable m for identifying the pulse Pm is set to the minimum value “1”.

  When the power supply 10 is turned on, the control circuit 33 generates command values Fa and Fb so as to generate desired output power on the secondary side of the transformer INT. Based on the command value Fa, the on-pulse width of the drive signals S1, S4 (here, the width of the H level pulse) is set, and on the basis of the command value Fb, the on-pulse width of the drive signals S2, S3 (here, H Level pulse width) is set. The command value Fa and the command value Fb at this time are normally set to the same value. The command values Fa and Fb are stored in a storage device (not shown) in the control circuit 33.

  When the switching elements TR1 and TR4 are turned on based on the ON pulses of the drive signals S1 and S4 at the times t1 to t2 shown in FIG. 5, the detection signal Ib detected by the current detector 21 becomes a positive value. Become. Corresponding to the ON periods (time t1 to t2) of the switching elements TR1 and TR4, an H level pulse Pm (here, pulse P1) is generated in the pulse signal Pu. The pulse width W1 of the pulse P1 is measured by the pulse width measuring circuit 32.

  Specifically, when a rising edge of the pulse signal Pu occurs at time t1 (YES in step ST2), the pulse width measurement circuit 32 measures the pulse width of the first pulse P1, that is, counts the clock signal CK. Is started (step ST3). Specifically, the pulse width measurement circuit 32 counts up the count value Nm (here, the count value N1) every time a rising edge of the clock signal CK is detected (N1 = N1 + 1). This counting operation is repeatedly executed until the falling edge of the pulse signal Pu occurs.

  Next, when the falling edge of the pulse signal Pu occurs at time t2 shown in FIG. 5 (YES in step ST4), the pulse width measurement circuit 32 stops counting the clock signal CK (step ST5). At this time, the pulse width measurement circuit 32 outputs a count value N1 corresponding to the pulse width W1 of the pulse P1 to the control circuit 33. In addition, the control circuit 33 adds “1” to the variable m. As a result, the variable m becomes “2”.

  Next, in step ST6, the control circuit 33 determines whether or not the variable m is larger than the number n (in this example, n = 8). That is, in step ST6, it is determined whether or not the measurement of the pulse width Wm of the predetermined number (eight in this example) of the pulses Pm is completed. Here, since m = 2 and m <n (NO in step ST6), the process returns to step ST2.

  Subsequently, at times t2 to t3 shown in FIG. 5, since all of the switching elements TR1 to TR4 are turned off and the pulse signal Pu is at the L level (NO in step ST2), the pulse width measurement by the pulse width measurement circuit 32 is performed. (Counting operation) is not started.

  Next, at time t3 to t4 shown in FIG. 5, when the switching elements TR2 and TR3 are turned on based on the ON pulses of the drive signals S2 and S3, the detection signal Ib detected by the current detector 21 becomes a negative value. Become. Corresponding to the ON periods of the switching elements TR2 and TR3, an H level pulse P2 is generated in the pulse signal Pu. Similarly to the pulse P1, the pulse width W2 of the pulse P2 is measured by the pulse width measurement circuit 32, and the count value N2 corresponding to the pulse width W2 of the pulse P2 is output to the control circuit 33 (step ST2). To ST5).

  Thereafter, similarly, the pulse widths W3 to W8 of the pulses P3 to P8 of the pulse signal Pu are measured by the pulse width measuring circuit 32, and the count values N3 to N8 corresponding to the pulse widths W3 to W8 of the pulses P3 to P8 are obtained. It is output to the control circuit 33.

Thereafter, when “1” is added to the variable m in step ST5, m = 9 and m> n (YES in step ST6), the process proceeds to step ST7.
Subsequently, the control circuit 33 calculates the pulse widths Wa and Wb corresponding to the actual on-time of the switching elements TR1 to TR4 based on the count values N1 to N8 input from the pulse width measurement circuit 32 (step ST7). . Specifically, the control circuit 33 obtains the pulse width Wm of the pulse Pm (that is, the pulse widths W1 to W8 of the pulses P1 to P8) by the following equation, where T is the period of the clock signal CK.

Wm = Nm × T
Here, in this example, the pulse widths W1, W3, W5, and W7 of the odd-numbered pulses P1, P3, P5, and P7 among the pulses P1 to P8 correspond to the ON times of the switching elements TR1 and TR4. The pulse widths W2, W4, W6, and W8 of the even-numbered pulses P2, P4, P6, and P8 among the pulses P1 to P8 correspond to the on-time of the switching elements TR2 and TR4.

  Therefore, the control circuit 33 calculates the average value of the pulse widths W1, W3, W5, and W7, and calculates the pulse width Wa corresponding to the on-time of the switching elements TR1 and TR4. Further, the control circuit 33 calculates an average value of the pulse widths W2, W4, W6, and W8, and calculates a pulse width Wb corresponding to the on-time of the switching elements TR2 and TR4. That is, the control circuit 33 calculates the pulse widths Wa and Wb from the following equations.

Wa = (W1 + W3 + W5 + W7) / 4
= {(N1 * T) + (N3 * T) + (N5 * T) + (N7 * T)} / 4
Wb = (W2 + W4 + W6 + W8) / 4
= {(N2 * T) + (N4 * T) + (N6 * T) + (N8 * T)} / 4
Next, the control circuit 33 determines the on-pulse width of the switching elements TR1 to TR4 based on the comparison result between the calculated pulse widths Wa and Wb (actual values) and the command values Fa and Fb stored in the storage device. The indicated command values Fa and Fb are corrected (step ST8). Specifically, when the command values Fa and Fb stored in the storage device are respectively set as the command values WFa and WFb for convenience, the control circuit 33 uses the following equations to calculate the corrected command values Fa and Fb. calculate.

Fa = (WFa−Wa) + WFa
Fb = (WFb−Wb) + WFb
That is, by adding the difference between the calculated pulse widths Wa and Wb (actual values) and the command values WFa and WFb stored in the storage device to the command values WFa and WFb, the corrected command values Fa, Fb is calculated. Here, the difference between the calculated pulse widths Wa and Wb and the command values WFa and WFb is a difference caused by characteristic variations of the photocoupler 34A and the switching elements TR1 to TR4. For this reason, the characteristic variation can be compensated by superimposing the difference on the original command values Fa and Fb (in this case, the command values WFa and WFb before correction set first).

  For example, when the pulse width Wa corresponding to the actual on-time of the switching elements TR1 and TR4 is smaller than the command value WFa, the command value WFa is corrected to be increased by an amount of time that is less than the command value WFa. The When the pulse width Wa is larger than the command value WFa, the command value WFa is corrected to be reduced by an extra time with respect to the command value WFa. Thereby, the actual on-time of the switching elements TR1 and TR4 can be brought close to the original command value WFa. Similarly, the actual on-time of switching elements TR2 and TR3 can be brought close to the original command value WFb. Therefore, the difference between the actual on-time of switching elements TR1 and TR4 and the actual on-time of switching elements TR2 and TR3 can be reduced.

  The correction processing of the command values Fa and Fb by the control unit 30 described above is always performed when the power supply device 10 is turned on. That is, after the correction process in step ST8 is completed, step ST1 is started again.

Next, characteristic effects of the present embodiment will be described.
(1) The input current Ia of the transformer INT is detected as a signal corresponding to the drive signals S1 to S4, and the pulse signal Pu is generated from the detection signal Ib corresponding to the input current Ia. The pulse width Wm of the pulse Pm included in the pulse signal Pu is measured, and the pulse widths Wa and Wb corresponding to the actual on-time of the switching elements TR1 to TR4 are calculated based on the measurement result. The command values Fa and Fb are corrected based on the difference between the pulse widths Wa and Wb (actual values) and the command values Fa and Fb. That is, the above-mentioned difference caused by the characteristic variation of the photocoupler 34A is superimposed on the command values Fa and Fb to correct the command values Fa and Fb. For this reason, by setting the on-pulse width of the drive signals S1 to S4 based on the corrected command values Fa and Fb, it is possible to reduce the influence due to the characteristic variation. Therefore, even when there is a characteristic variation in the photocoupler 34A, it is possible to suppress an increase in the difference between the on-time of the switching elements TR1 and TR4 and the on-time of the switching elements TR2 and TR3. As a result, it is possible to suitably suppress the occurrence of magnetic bias in the transformer INT.

  Further, the correction of the command values Fa and Fb is automatically executed by an internal calculation of the control circuit 33. For this reason, it is possible to easily correct the command values Fa and Fb and compensate for variations in the on-pulse width of the drive signals S1 to S4, compared to the case where the resistance value of the variable resistor is adjusted manually.

  (2) The correction process of the command values Fa and Fb is always executed when the power supply device 10 is turned on. Further, the control unit 30 corrects the command values Fa and Fb based on the difference obtained from time to time. For this reason, even if the characteristic variation of the photocoupler 34A or the like changes due to a change in use environment (for example, use temperature) or use time, the command values Fa, Fb can be easily corrected. That is, since the difference also changes according to the change in characteristic variation, the characteristic variation after the change can be compensated by correcting the command values Fa and Fb based on the changed difference. Therefore, even when the variation in the characteristics of the elements such as the photocoupler 34A changes due to changes in the usage environment or deterioration over time, variations in the on-pulse width of the drive signals S1 to S4 can be compensated for, and the occurrence of bias magnetism is prevented. It can suppress suitably.

  (3) Further, the pulse widths Wa and Wb are calculated using the detection signal Ib corresponding to the input current Ia. For this reason, the difference between the command values Fa and Fb and the pulse widths Wa and Wb reflects the characteristic variation of the switching elements TR1 to TR4 together with the characteristic variation of the photocoupler 34A. Therefore, by superimposing the difference on the command values Fa and Fb, it is possible to reduce the influence due to the characteristic variation of the switching elements TR1 to TR4 together with the influence due to the characteristic variation of the photocoupler 34A.

  (4) In the welding power supply device 10 including the inverter circuit 12 and the transformer INT, since a large current is generated on the circuit when the transformer INT is excessively demagnetized, the switching elements TR1 to TR4 of the inverter circuit 12 are abnormal. This is a configuration that can generate heat. Therefore, application to the power supply apparatus 10 having the configuration as in the present embodiment is particularly effective, and can contribute to improving the reliability of the welding power supply apparatus 10.

  (5) The pulse widths Wa and Wb are calculated from the average value of the pulse widths Wm of the plurality of pulses Pm. For this reason, for example, even when the ON times of the switching elements TR1 to TR4 change suddenly due to noise or the like, it is preferable that the command values Fa and Fb are corrected more than necessary with the sudden change. Can be suppressed.

In addition, you may change the said embodiment as follows.
In the above embodiment, the difference between the calculated pulse widths Wa and Wb and the command values WFa and WFb is added to the command values WFa and WFb that are set first before correction. For example, the difference may be added to the command values Fa and Fb generated based on the detection signal Id corresponding to the output current Io from time to time.

  In the above embodiment, the correction processing of the command values Fa and Fb by the control unit 30 is always performed when the power supply device 10 is turned on. For example, the correction processing of the command values Fa and Fb may be performed intermittently when the power supply device 10 is turned on. That is, when the power supply device 10 is turned on, the correction processing of the command values Fa and Fb may be performed once every predetermined time (for example, one hour).

  Alternatively, the correction processing of the command values Fa and Fb may be performed only once such as at the time of shipping inspection. In this case, a circuit similar to the control circuit 33 is provided in the inspection unit for shipping inspection, and the same correction processing as in the above embodiment is performed in the circuit, and the command value after the correction processing is controlled in the power supply device 10. Set in circuit 33. Note that the power supply device 10 in this case is provided with a communication device that transmits the count value Nm output from the pulse width measurement circuit 32 to the inspection unit.

  In the control circuit 33 of the above embodiment, the difference value between the calculated pulse widths Wa and Wb and the command values Fa and Fb is calculated a plurality of times, an average value of the difference values for a plurality of times is calculated, and the difference value May be added to the original command values Fa and Fb (correction values initially set or command values generated based on the detection signal Id or the like at that time).

  The number n in the correction processing of the command values Fa and Fb in the above embodiment is not particularly limited. For example, the number n may be set to “2” to “7”, or the number n may be set to “9” or more.

  In the above embodiment, the average value of the pulse widths Wm of the plurality of pulses Pm is calculated to calculate the pulse widths Wa and Wb. For example, the pulse width Wm of one pulse Pm corresponding to the ON time of the switching elements TR1 and TR4 is set as the pulse width Wa, and the pulse width of one pulse Pm corresponding to the ON time of the switching elements TR2 and TR3 is used. Wm may be calculated as the pulse width Wb.

  In the above embodiment, the pulse signal Pu is generated from the detection signal Ib corresponding to the input current Ia of the transformer INT, and the pulse width Wm of the pulse signal Pu is measured. That is, the pulse signal Pu generated from the detection signal Ib (input current Ia of the transformer INT) is used as the pulse signal corresponding to the drive signals S1 to S4 output from the drive circuit 34. However, the present invention is not limited to this. You may change suitably.

  For example, as shown in FIG. 6, the control unit 30 may be changed to a control unit 30A. In the control unit 30A, the signal processing circuit 31 is omitted from the control unit 30 (see FIG. 1), and the drive signals S1 to S4 are input to the pulse width measurement circuit 32 as pulse signals. The pulse width measurement circuit 32 measures the on pulse widths of the drive signals S1 to S4, respectively. Specifically, the pulse width measurement circuit 32 counts the clock signal CK (see FIG. 3) during the period when the on-pulses of the drive signals S1 to S4 are generated, and corresponds to the on-pulse widths of the drive signals S1 to S4. The count value Nm is output to the control circuit 33.

  Based on the count value Nm, the control circuit 33 calculates a pulse width (second pulse width) corresponding to the actual on-pulse width of the drive signals S1 to S4, and calculates the calculated pulse width and the command values F1 to F4. Calculate the difference. Further, the control circuit 33 adds the calculated difference to the original command values F1 to F4 (for example, a correction value that is initially set or a command value that is generated based on the detection signal Id or the like at that time). The command values F1 to F4 are corrected. Then, the drive circuit 34 has a drive signal S1 having an on-pulse width based on the corrected command value F1, a drive signal S2 having an on-pulse width based on the corrected command value F2, and an on-pulse based on the corrected command value F3. A drive signal S3 having a width and a drive signal S4 having an on-pulse width based on the corrected command value F4 are generated.

  According to this configuration, the command values F1 to F4 are based on the difference caused by the characteristic variation of the elements such as the photocoupler 34A in the drive circuit 34, that is, the difference between the calculated pulse width and the command values F1 to F4. Is corrected. Thereby, it is possible to reduce the influence due to the characteristic variation of the photocoupler 34A, and to compensate for the variation in the on-pulse width of the drive signals S1 to S4.

  Further, since the on-pulse widths of the drive signals S1 to S4 are individually measured, the command values F1 to F4 for setting the on-pulse widths of the drive signals S1 to S4 can be individually corrected.

  -For example, as shown in Drawing 7, control part 30 may be changed into control part 30B. In the control unit 30B, the signal processing circuit 31 is changed to a signal processing circuit 31A. The signal processing circuit 31A receives the detection signal Ib from the current detector 21 and the drive signals S1 to S4. When the detection signal Ib is 0A, the signal processing circuit 31A outputs the drive signals S1 to S4 to the pulse width measurement circuit 32 as the pulse signal Pu. On the other hand, when the detection signal Ib is other than 0A, the signal processing circuit 31A generates the pulse signal Pu from the detection signal Ib and outputs the pulse signal Pu to the pulse width measurement circuit 32, as in the above embodiment.

  According to this configuration, the drive signals S1 to S4 are used when the detection signal Ib is 0A, that is, during a period in which the correction processing of the command values F1 to F4 cannot be performed using the pulse signal Pu generated from the detection signal Ib. Thus, it is possible to correct the command values F1 to F4.

Note that the switching condition between the detection signal Ib and the drive signals S1 to S4 in the signal processing circuit 31A is not limited to the above condition, and may be changed as appropriate.
The inverter circuit 12 may have a configuration other than a full bridge circuit, for example, a half bridge circuit.

  -Although applied to the power supply apparatus 10 for arc welding, you may apply to other power supply apparatuses for welding or power supplies other than welding.

10 Power supply (Power supply for welding)
DESCRIPTION OF SYMBOLS 11 Primary side conversion circuit 12 Inverter circuit 13 Secondary side conversion circuit 21 Current detector 30, 30A, 30B Control part 31, 31A Signal processing circuit 32 Pulse width measurement circuit 33 Control circuit 34 Drive circuit 34A Photocoupler 51 Counter Fa, Fb Command value F1 to F4 Command value Ia Input current Ib Detection signal INT Welding transformer (transformer)
L1 Primary side coil L2 Secondary side coil Pu Pulse signal S1 to S4 Drive signal TR1 to TR4 Switching element Wa, Wb Pulse width (first pulse width)

Claims (6)

An inverter circuit that is provided on the primary side of the transformer and generates a high-frequency AC voltage from a DC voltage by an operation of a switching element that constitutes a bridge circuit;
A control unit that generates a drive signal for controlling a switching operation of the switching element so as to generate a desired output power on the secondary side of the transformer,
The controller is
A control circuit for generating a command value for setting an on-pulse width of the drive signal;
A drive circuit that outputs the drive signal having an on-pulse width based on the command value to the switching element;
A pulse width measuring circuit for measuring a pulse width of a pulse signal corresponding to the drive signal,
The power supply apparatus, wherein the control circuit corrects the command value based on a comparison result between the pulse width measured by the pulse width measurement circuit and the command value. The power supply device according to claim 1,
A current detector for detecting an input current input to the primary side of the transformer;
The controller is
Full-wave rectification of the detection signal acquired by the current detector, comprising a signal processing circuit that outputs the pulse signal generated by shaping the signal after full-wave rectification to the pulse width measurement circuit,
The control circuit calculates a first pulse width corresponding to the ON time of the switching element based on the pulse width measured by the pulse width measurement circuit, and calculates a difference between the first pulse width and the command value. A power supply device that is superimposed on the command value. The power supply device according to claim 1,
The pulse width measurement circuit inputs the drive signal as the pulse signal,
The control circuit calculates a second pulse width corresponding to the on-pulse width of the drive signal based on the pulse width measured by the pulse width measurement circuit, and calculates a difference between the second pulse width and the command value. A power supply device that is superimposed on the command value. The power supply device according to claim 1,
A current detector for detecting an input current input to the primary side of the transformer;
The controller is
The drive signal and the detection signal acquired by the current detector are input, and when the detection signal is 0 A, the drive signal is output as the pulse signal to the pulse width measurement circuit, while the detection When the signal is other than 0A, a signal processing circuit is provided for full-wave rectifying the detection signal and outputting the waveform-shaped signal of the signal after full-wave rectification as the pulse signal to the pulse width measurement circuit. A power supply characterized by. In the power supply device according to any one of claims 1 to 4,
The power supply device, wherein the control circuit executes correction of the command value constantly or intermittently when the power supply device is turned on.   A welding power supply device configured to generate welding output power using the power supply device according to any one of claims 1 to 5.