JP2010012510A - Welding power supply device and welding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding power supply device of an inverter welding machine capable of enhancing the biased magnetization suppressing effect of a welding transformer. <P>SOLUTION: An output control circuit 16 sets the driving pulse for turning on a switching element of an inverter circuit to the pulse width according to the current operational situation, and the output destination of the driving pulse is changed to any one of corresponding switching elements as the A-side and B-side driving signals. When the pulse width is set to the zero width, and when a changing circuit 30 performs the determination, the changing operation of the output destination of the driving pulse is temporarily stopped so as to maintain the output destination when determining the zero width even in the next control period in the changing circuit 30. Thus, the driving pulse of the control period before and after the pulse width is set to be the zero width is determined so that the output destination to the switching element is constantly different, preventing only the switching element of one set from being continuously turned on. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a welding power supply apparatus for an inverter welding machine suitable for suppressing the demagnetization of a welding transformer and the welding machine.

  A welding power source device for an inverter welding machine supplies a DC voltage obtained by rectifying and smoothing an input AC power source using a DC conversion circuit to the inverter circuit, and converts it to a predetermined high-frequency AC voltage by turning on / off the switching element of the inverter circuit. Then, it is supplied to the primary side of the welding transformer and converted to a welding DC voltage suitable for welding on the secondary side of the welding transformer.

  By the way, the inverter circuit is configured by a bridge circuit using a plurality of switching elements, and the polarity of the high-frequency AC voltage is reversed by turning on and off predetermined switching elements alternately. There may be a deviation in on-time between the element and the other side. In this case, the high-frequency AC voltage is biased to one polarity side, and the welding transformer is magnetized, so-called biased magnetism. Since the demagnetization of the welding transformer causes an overcurrent to continuously occur on the primary side of the transformer and destroys the switching elements of the inverter circuit, it is desired to take measures to suppress the demagnetization.

  Therefore, for example, in the welding power supply apparatus of the inverter welding machine shown in Patent Document 1 and Patent Document 2, the first and last inverter control cycles are set to opposite polarities (phases), thereby one of the high-frequency AC voltages. It is difficult to cause a bias toward the polar side, and the bias is suppressed.

Further, for example, in the welding power supply apparatus for an inverter welder disclosed in Patent Document 3, the first polarity of the inverter control cycle is always reversed, and the number of drive pulses during the inverter control cycle for turning on the switching element is an odd number. Similarly, it is difficult to cause the high-frequency AC voltage to be biased to one polarity side, and the bias is suppressed.
JP-A-8-224664 JP-A-63-108975 Japanese Patent Laid-Open No. 3-118984

  Here, in the welding power supply apparatus of the inverter welding machine as shown in Patent Documents 1 to 3 described above, the primary current and secondary current of the welding transformer are usually detected, and the detected current value and output setting are detected. Feedback control is performed to match the values (see Patent Documents 2 and 3).

  In this case, if the detected current value is too larger than the output set value, the pulse width of the drive pulse of the switching element to be turned on next is set to zero (missing tooth), the switching element at that time is turned off, and the current value is sharpened. It is done to make it smaller. In particular, when the control gain of feedback control is increased with the recent increase in the switching speed of the inverter circuit, the switching element on one side is continuously turned on and the switching element on the other side is continuously turned off. Therefore, it becomes difficult to set a proper driving pulse. In this case, a high-frequency AC voltage supplied to the welding transformer falls into a biased state where the polarity is biased to one side.

  Therefore, as described in the above Patent Documents 1 to 3, rather than making the first and last polarities of the inverter control period the same and demagnetizing, the pulse width of the drive pulse on one side becomes zero, Since it is easier to fall into a demagnetized state when the period during which only the switching element on the side is continuously turned on continues, it has been desired to solve this problem and suppress the demagnetization.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a welding power supply apparatus for an inverter welder that can further improve the effect of suppressing the demagnetization of the welding transformer, and the welder thereof. There is to do.

  In order to solve the above-described problem, the invention according to claim 1 is a circuit in which a first set and a second set of switching elements are alternately turned on and off in an inverter circuit configured by using a plurality of switching elements. An AC voltage is generated, the generated AC voltage is supplied to the primary side of the welding transformer, and a DC voltage for welding is generated on the secondary side, and the drive pulse for turning on the switching element is in accordance with the operation situation at that time. A power supply apparatus for welding comprising an output control circuit that controls to switch the output destination of the drive pulse to any one of the sets of the switching elements for each control cycle. The control circuit includes: zero width determining means for determining whether or not the pulse width of the driving pulse is zero width; and the zero width determining means determines that the pulse width of the driving pulse is zero width. Then, in order to maintain the output destination at the time of the zero width determination in the next control cycle, the gist of the invention is to include switching prohibiting means for temporarily prohibiting the switching operation of the output destination of the drive pulse. .

  In the present invention, the output control circuit sets the drive pulse for turning on the switching element of the inverter circuit to a pulse width corresponding to the operation status at that time, and sets the output destination of the drive pulse for each control cycle to the first set and When switching to one of the second set of switching elements and the pulse width is set to zero width according to the operation situation at that time, if the determination is made by the zero width determination means, the switching prohibition means In the next control cycle, the drive pulse output destination switching operation is temporarily prohibited in order to maintain the output destination at the time of the zero width determination. As a result, the drive pulses of the control period before and after the pulse width is set to zero width always have different output destinations for the switching elements, and the switching elements that are turned on are alternately alternated in different sets. Therefore, for example, even when the timing at which the pulse width is set to zero width is synchronized every other control cycle, only one set of switching elements is alternately turned on without alternately turning on each set of switching elements. Is turned on, and the occurrence of a bias magnetism biased to one polarity in the subsequent welding transformer is more reliably suppressed.

  According to a second aspect of the present invention, in the welding power source device according to the first aspect, the output control circuit internally generates a voltage corresponding to a pulse width of the drive pulse corresponding to the operation state at that time. The zero width determination means comprises a comparator that compares a voltage corresponding to the pulse width of the drive pulse with a voltage corresponding to the zero width determination value and outputs the comparison result as an output signal. The gist of the invention is that the switching prohibiting means comprises a logic gate circuit that generates an output signal for prohibiting the switching operation of the output destination of the drive pulse based on the output signal from the comparator. And

  In the present invention, the zero width determination means includes a comparator that outputs an output signal based on a comparison between a voltage corresponding to the pulse width of the drive pulse and a voltage corresponding to the zero width determination value. And a logic gate circuit that generates an output signal for prohibiting the switching operation of the output destination of the drive pulse on the basis of the output signal from. That is, the zero width determination unit and the switching prohibition unit can be simply configured, which can contribute to the simplification of the configuration of the entire apparatus.

A third aspect of the present invention is a welding machine configured to perform welding based on the welding DC voltage generated by the power supply device according to the first or second aspect.
In this invention, since the power supply device of Claim 1 or 2 is used and a welder is comprised, the welder which can obtain the effect of said each claim can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the power supply device for welding of the inverter welding machine which can improve the demagnetization suppression effect of a welding transformer more, and its welding machine can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 shows an inverter arc welder 10 according to this embodiment. The arc welding machine 10 supplies the welding DC voltage generated by the welding power supply device 11 to the torch TH, generates an arc from the torch TH toward the workpiece M, and performs arc welding of the workpiece M. It is a device that performs. The welding power supply device 11 is compatible with a three-phase AC power supply such as 200 V or 400 V, and includes a primary side rectifier circuit 12, an inverter circuit 13, a welding transformer 14, a secondary side rectifier circuit 15, an output control circuit 16, and a setting device 17. It has.

  The primary side rectifier circuit 12 includes a diode bridge, a smoothing capacitor, and the like, generates a primary side DC voltage from an input three-phase AC power supply, and supplies the generated DC voltage to the subsequent inverter circuit 13.

  The inverter circuit 13 is configured by a full bridge circuit using four switching elements S1 to S4 made of four IGBTs. In the switching elements S1 to S4, the first set of switching elements S1 and S4 and the second set of switching elements S2 and S3 are alternately turned on and off based on a control signal from the output control circuit 16 input to each gate, Thereby, the DC voltage from the primary side rectifier circuit 12 is converted into a predetermined high-frequency AC voltage. The inverter circuit 13 supplies the high-frequency AC voltage to the primary coil 14a of the welding transformer 14 at the subsequent stage.

  A primary current detector 18 is disposed on the power line between the output terminal of the inverter circuit 13 and the primary coil 14 a of the welding transformer 14, and the current detector 18 connects the welding transformer 14 with the inverter circuit 13. A primary current value flowing through the primary coil 14a is detected, and the primary current value is output to the output control circuit 16 as a voltage signal.

  The welding transformer 14 includes a primary side coil 14a, a secondary side coil 14b, and a detection coil 14c on the secondary side, performs voltage conversion between the primary side coil 14a and the secondary side coil 14b, and performs arc conversion. It is converted to a voltage value suitable for welding. A voltage detection circuit 19 is connected to the detection coil 14c provided on the secondary side. The voltage detection circuit 19 detects a voltage integral value (voltage change) on the secondary side, and the voltage integral value is The voltage signal is output to the output control circuit 16.

  The secondary coil 14 b of the welding transformer 14 is connected to the secondary rectifier circuit 15. The secondary side rectifier circuit 15 includes a diode, a DC reactor, and the like, generates a welding DC voltage from the high-frequency AC voltage adjusted to a predetermined voltage by the welding transformer 14, and uses the generated welding DC voltage to the torch TH. To supply. Then, by connecting the workpiece M to the intermediate tap of the secondary coil 14b, an arc is generated from the torch TH to the workpiece M based on the supply of the welding DC voltage, and arc welding is performed. It is like that.

  Further, an output current detector 20 is disposed on the power supply line between the workpiece M and the intermediate tap of the secondary coil 14b, and the output current value that has flowed to the workpiece M by the current detector 20 is determined. The output current value is detected and output to the output control circuit 16 as a voltage signal.

  The output control circuit 16 controls switching of the inverter circuit 13 to adjust the high-frequency AC voltage and adjust the welding DC voltage supplied to the torch TH. In this case, the on-pulse width of the switching elements S1 to S4 is adjusted by changing the duty. PWM control is performed. The output control circuit 16 receives a current setting value corresponding to the setting from the setting device 17 that can be set by the user, and the control circuit 16 receives the current setting value and the output current detector 20 from the current setting value. Switching control of the inverter circuit 13 is performed on the basis of the output current value and the voltage integrated value from the voltage detection circuit 19. The output control circuit 16 also performs feedback control using the output current value from the output current detector 20 and the like.

  FIG. 2 shows a specific configuration of the output control circuit 16. The output control circuit 16 is first provided with an adder 21, which includes a current setting value from the setting device 17, an output current value from the output current detector 20, and a voltage detection circuit 19. Are integrated as voltage signals. In this case, the current set value is input to the adder 21 as it is, and the output current value and the voltage integral value are inverted and input to the adder 21. The output signal of the adder 21 is amplified by the amplifier 22 with a predetermined gain, inverted through the inverting amplifier 23, and input to the negative input terminal of the first comparator 24.

  Therefore, when the current set value is increased, the output signal level of the adder 21 is increased and the output signal level of the inverting amplifier 23 is decreased. When the current set value is decreased, the output signal level of the adder 21 is decreased. Thus, the output signal level of the inverting amplifier 23 increases. On the other hand, when either the output current value or the voltage integrated value increases, the output signal level of the adder 21 decreases, the output signal level of the inverting amplifier 23 increases, and either the output current value or the voltage integrated value decreases. As a result, the output signal level of the adder 21 increases and the output signal level of the inverting amplifier 23 decreases. Incidentally, the output signal of the inverting amplifier 23 corresponds to the target pulse width of the driving pulse of the switching elements S1 to S4 at that time, and the subsequent stage of the output signal of the inverting amplifier 23 determines the pulse width of the driving pulse of the next inverter control cycle. It is output to the first comparator 24.

  A triangular wave (sawtooth wave) signal is input from the triangular wave generation circuit 25 to the positive side input terminal of the first comparator 24. The period of this triangular wave corresponds to the inverter control period. The output signal of the first comparator 24 is input to a first input terminal of a first AND circuit 26 composed of a 3-input AND circuit and a first input terminal of a second AND circuit 27 also composed of a 3-input AND circuit. ing. The output signal of the first AND circuit 26 is output as an A-side drive signal for driving the first set of switching elements S1 and S4 on and off, and the output signal of the second AND circuit 27 is output as the second set of switching elements S2. , S3 are output as B-side drive signals for driving on and off.

  In other words, the first comparator 24 generates an output signal (base pulse signal) that is at the H level during a period when the triangular wave signal level is higher than the output signal level based on the output signal of the inverting amplifier 23 and the triangular wave signal. . Therefore, when the output signal level of the inverting amplifier 23 rises and falls due to changes in the current setting value, the output current value, and the voltage integration value as described above, the H level period of the output signal of the comparator 24 becomes longer and shorter in relation to the triangular wave signal. . Incidentally, when the current setting value is large and the output current value or the voltage integral value is small, the output signal level of the inverting amplifier 23 is lowered, so that the H level period of the output signal of the comparator 24 becomes large. On the other hand, when the current setting value is small and the output current value or the voltage integral value is large, the output signal level of the inverting amplifier 23 is increased, so that the H level period of the output signal of the comparator 24 is small. When the signals input to the other input terminals (second and third input terminals) of the first and second AND circuits 26 and 27 are at the H level, the output signal of the comparator 24 is output from each of the AND circuits 26 and 27. Reflected in the A and B side drive signals as output signals and output to the switching elements S1 to S4, the on-time of the switching elements S1 to S4 is adjusted.

  The output signals from the second comparator 28 are input to the second input terminals of the first and second AND circuits 26 and 27, respectively. The second comparator 28 receives the primary current value from the primary current detector 18 as a voltage signal at the negative input terminal, and determines whether the primary current value is an overcurrent at the positive input terminal. A voltage corresponding to the overcurrent determination value is applied.

  That is, the second comparator 28 outputs an H level output signal to the second input terminals of the first and second AND circuits 26 and 27 when the primary current value is less than the overcurrent determination value. Therefore, when the signal input to the third input terminals of the AND circuits 26 and 27 is at the H level, the output signal of the comparator 24 is switched to the switching elements S1 to S4 as the A and B side drive signals via the AND circuits 26 and 27. Is output. On the other hand, when the primary current value becomes equal to or higher than the overcurrent determination value, the second comparator 28 outputs an L level output signal to the second input terminals of the first and second AND circuits 26 and 27. Therefore, even if the signal input to the third input terminals of the AND circuits 26 and 27 becomes the H level, the A and B side drive signals that are the output signals of the AND circuits 26 and 27 are fixed to the L level, and the switching element. S1 to S4 are turned off.

  Output signals from the switching circuit 30 are input to the third input terminals of the first and second AND circuits 26 and 27, respectively. The switching circuit 30 operates based on the pulse signal generated by the pulse generation circuit 29. The pulse generation circuit 29 generates a pulse signal from the triangular wave signal from the triangular wave generation circuit 25. In this case, since one cycle of the triangular wave signal is one cycle of the inverter control cycle, a pulse signal synchronized with the inverter control cycle is generated. It is generated and output to the switching circuit 30. Accordingly, the switching circuit 30 performs an operation synchronized with the inverter control cycle.

  FIG. 3 shows a specific configuration of the switching circuit 30. The switching circuit 30 is first provided with a third AND circuit 31. The AND circuit 31 receives a pulse signal from the pulse generation circuit 29 at one input terminal, and the third comparator 32 at the other input terminal. An output signal is input. An output signal from the adder 21 that has passed through the amplifier 22 and the inverting amplifier 23 is input to the positive side input terminal of the third comparator 32, and a zero width determination value corresponding to a pulse width of zero is input to the negative side input terminal. Have been entered. The output signal of the third AND circuit 31 is output to the clock terminal CLK of the flip-flop 33.

  Based on the output signal of the third AND circuit 31 input to the clock terminal CLK, the flip-flop 33 outputs a complementary output signal in which the H and L levels alternate from the output terminals Q and Q, and the output terminal bar The output signal output from Q is output to the third input terminal of the first AND circuit 26 shown in FIG. 2, and the output signal output from the output terminal Q is output to the third input terminal of the second AND circuit 27, respectively. Has been.

  That is, in the switching circuit 30, when the output signal from the third comparator 32 is at the H level, a pulse signal synchronized with the inverter control cycle is output to the clock terminal CLK of the flip-flop 33 as the output signal of the third AND circuit 31. The In the flip-flop 33, the logic of the output signals of the output terminals Q and Q is inverted every one cycle of the pulse signal, that is, every cycle of the inverter control cycle, and this complementary output signal is sent to each AND circuit 26 and 27. Is output. Therefore, the AND circuits 26 and 27 use the output signal of the comparator 24 as the A side drive signal so that a drive pulse (H level pulse) is alternately generated in the A side or B side drive signal for each inverter control cycle. The output signal is alternately output to the switching elements S1 and S4 to the switching elements S2 and S3 as the B-side drive signal.

  On the other hand, when the output signal of the third comparator 32 becomes L level, the output signal of the third AND circuit 31 input to the clock terminal CLK of the flip-flop 33 is fixed to L level. On the other hand, when the output signal of the third comparator 32 becomes L level, the output signal of the third AND circuit 31 input to the clock terminal CLK of the flip-flop 33 is fixed to L level. Then, in the flip-flop 33, the logic of the output signals from the output terminals Q and Q at that time is held, and in the AND circuits 26 and 27, the drive signal from the same side continues to be supplied from the switching elements S1 to S1 in the next inverter control cycle. Output to S4.

  Here, the third comparator 32 compares the output signal level of the inverting amplifier 23 with the zero width determination value, that is, whether the target pulse width of the driving pulses of the switching elements S1 to S4 at that time is a level equal to or less than the zero width. It is judged whether the level exceeds. In the determination that the target pulse width of the drive pulse exceeds the zero width, the third comparator 32 sets the output signal to the H level, and outputs the comparator 24 so that the drive pulse is alternately generated in the A side or B side drive signal at every inverter control cycle. The signals are alternately switched and output as A side or B side drive signals.

  On the other hand, in the determination that the target pulse width of the drive pulse is equal to or less than the zero width, the third comparator 32 sets the output signal to the L level, and the output signal of the comparator 24 is continuously driven on the same side even when the inverter control cycle becomes the next control cycle. Output as a signal. In other words, if the drive pulse is set to zero width in the current control cycle, the drive pulse is reflected in the drive signal on the same side in the next control cycle, and driving is performed in the control cycle before and after the zero width is set. The pulse is reflected in the drive signal on the different side. Accordingly, the switching elements S1 and S4 and the switching elements S2 and S3 on different sides are always turned on alternately, thereby suppressing the welding transformer 14 from being biased to one polarity and suppressing the bias magnetism. It has been.

  Here, FIG. 6 shows waveforms at various points of the power supply device (11) when the control gain is low. In FIG. 6, the voltage waveform at point a in FIG. Since the fluctuation of the output signal level of the inverting amplifier (23) reflecting the target pulse width of the pulse is small, the drive pulse rises alternately for each control period in the A side and B side drive signals, and against the demagnetization of the welding transformer (13). Although the influence is small, the small fluctuation means that the responsiveness is low. If the speed of the inverter control is increased, a desired output current cannot be obtained from time to time, and there is a concern about the influence on the welding performance.

  Therefore, in the power supply device 11 of the present embodiment, the switching elements S1 to S4 corresponding to the high speed are used to cope with the high speed of the inverter control, and in the output control circuit 16, the amplifier 22 is set to a high gain, and the control is performed. Gain is set high. Therefore, as shown in various waveforms of the power supply device 11 of the present embodiment in FIG. 4, the output signal level of the inverting amplifier 23 (the voltage waveform at the point a in FIG. 2) reflecting the target pulse width of the driving pulse at that time. ) Will vary greatly. On the other hand, the output signal level often occurs higher than the triangular wave signal level.

  FIG. 5 shows waveforms at various points of the power supply device (11) having a specification with a high control gain but no bias. Specifically, in the switching circuit (30) shown in FIG. 3, the third AND circuit (31) and the third comparator (32) are omitted, and a pulse signal is directly input to the clock terminal CLK of the flip-flop (33). It is the structure to do. In the case of this specification, as in FIG. 4, the output signal level (voltage waveform at point a in FIG. 2) of the inverting amplifier 23 reflecting the target pulse width of the driving pulse at that time varies greatly.

  In this case, for example, when the output signal level of the inverting amplifier (23) continuously becomes higher than the triangular wave signal level in every other control cycle of the inverter control cycle (one cycle of the triangular wave signal), the B side The drive pulse rises only in the drive signal. Then, the welding transformer (13) falls into a biased magnetic state biased to one polarity, the primary current value exceeds the overcurrent determination value, and the output of the drive signal during that time is stopped, but the switching elements (S1 to S4) ) Is heavy, and in some cases, damage may occur.

  On the other hand, in this embodiment, as shown in FIG. 4, every time the output signal level of the inverting amplifier 23 becomes higher than the triangular wave signal level in every other control cycle of the inverter control cycle, the output of the inverting amplifier 23 is output. The signal level, that is, the target pulse width of the drive pulse is determined by the third comparator 32 of the switching circuit 30 to be equal to or less than the zero width, and the output terminal Q of the flip-flop 33 is shown by the voltage waveforms at points c and d in FIG. , The logic of the output signal from the bar Q is retained.

  That is, even if the inverter control cycle becomes the next control cycle, the output signal of the comparator 24 is continuously output as the drive signal on the same side. Therefore, when the drive pulse is set to zero width in the current control cycle, In the control cycle, the drive pulse is reflected in the drive signal on the same side, and in the control cycle before and after the zero width is set, the drive pulse is reflected in the drive signal on the different side. Therefore, in the power supply device 11 of the present embodiment, the switching elements S1 and S4 and the switching elements S2 and S3 on the different sides are always turned on alternately, whereby the biasing magnet in which the welding transformer 14 is biased to one polarity. Can be suppressed.

Next, characteristic effects of the present embodiment will be described.
(1) In the present embodiment, the output control circuit 16 sets the drive pulse for turning on the switching elements S1 to S4 of the inverter circuit 13 to the operation state at that time (current setting value, output current value and voltage integral value in the present embodiment). And the output destination of the drive pulse for each control cycle is the first set of switching elements S1, S4 (A-side drive signal) and the second set of switching. It is switched to one of the elements S2 and S3 (B side drive signal). When the pulse width is set to zero width according to the operation situation at that time, when the determination is made by the comparator 32 in the switching circuit 30, the operation of the AND circuit 31 in the switching circuit 30 is performed. In the next control cycle, the switching operation of the output destination of the drive pulse in the flip-flop 33 is temporarily prohibited in order to maintain the output destination at the time of the zero width determination. As a result, the drive pulses of the control period before and after the pulse width set to zero width always have different output destinations for the switching elements S1 to S4, and the switching elements S1 to S4 that are turned on are always alternately different. Become. Therefore, for example, even when the timing at which the pulse width is set to zero width is synchronized every other control cycle, only one set of switching elements S1 to S4 is alternately turned on without being turned on continuously. The switching elements S1 to S4 are turned on, and the occurrence of a bias magnetism biased to one polarity in the subsequent welding transformer 14 is more reliably suppressed. Thereby, the power supply apparatus 11 for welding which can further improve the demagnetization suppression effect of the welding transformer 14, and the arc welding machine 10 can be provided.

  (2) In this embodiment, the switching circuit 30 outputs an output signal based on a comparison between a voltage corresponding to the pulse width of the drive pulse (output signal level of the inverting amplifier 23) and a voltage corresponding to the zero width determination value. The comparator 32 is configured using an AND circuit 31 that generates an output signal for prohibiting the switching operation of the output destination of the drive pulse based on the output signal from the comparator 32. That is, the switching circuit 30 can be simply configured using the comparator 32 and the AND circuit 31, which can contribute to simplification of the configuration of the output control circuit 16, and thus the entire power supply device 11.

In addition, you may change embodiment of this invention as follows.
In the above embodiment, the circuit configuration of the output control circuit 16 may be changed as appropriate. For example, the current set value, the output current value, and the voltage integral value are used in setting the target on-pulse width according to the operation state at that time, but other detection values other than these may be used.

  In the switching circuit 30, the means for prohibiting the switching operation of the flip-flop 33 is configured using one AND circuit 31, but may be configured by combining a plurality of other logic gate circuits. Further, although the means for performing the zero width determination of the pulse width of the drive pulse is configured using one comparator 32, it may be configured using a determination circuit other than the comparator.

  -In the said embodiment, although applied to the power supply apparatus 11 for welding of the arc welding machine 10, this arc welding shall also include arc cutting. Moreover, you may apply to the power supply apparatus for welding of other electric welding machines, such as resistance welding, other than arc welding.

Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(B) In an inverter circuit configured by using a plurality of switching elements, a predetermined AC voltage is generated by alternately turning on and off the first and second sets of switching elements, and the generated AC voltage is supplied to the welding transformer. In the welding power supply device configured to supply the primary side and generate the welding DC voltage on the secondary side,
Control for setting the drive pulse for turning on the switching element to a pulse width corresponding to the operation state at that time, and controlling the output destination of the drive pulse to be switched to any one of the sets of the switching elements at each control cycle A device,
Zero width determination means for determining whether or not the pulse width of the drive pulse is zero width;
When the pulse width of the drive pulse is determined to be zero width by the zero width determination means, the operation of switching the output destination of the drive pulse is performed in order to maintain the output destination at the time of the zero width determination in the next control cycle. A control device for a welding power supply device, comprising: a switching prohibiting means for temporarily prohibiting.

  If the control device having such a configuration is used for a welding power source device, the same effect as that of the first aspect of the invention can be obtained.

It is a circuit diagram which shows the power supply device for welding of the inverter welding machine of this embodiment. It is a circuit diagram which shows the specific structure of the output control circuit in this embodiment. It is a circuit diagram which shows the specific structure of the switching circuit in this embodiment. It is a wave form diagram of various places of the power supply device of this embodiment corresponding to a high-gain and magnetic bias. It is a wave form diagram of various places of a power supply device of a specification which is not high-gain and does not correspond to magnetic demagnetization. It is a wave form diagram of various places of a power supply device in a low gain specification.

Explanation of symbols

10 ... arc welding machine (welding machine), 11 ... power supply device for welding (power supply device),
13 ... Inverter circuit, 14 ... Welding transformer, 16 ... Output control circuit,
31 ... Third AND circuit (switching prohibiting means),
32. Third comparator (zero width determination means),
S1 to S4: switching elements.

Claims (3)

In the inverter circuit configured by using a plurality of switching elements, the first set and the second set of switching elements are alternately turned on and off to generate a predetermined AC voltage, and the generated AC voltage is supplied to the primary side of the welding transformer. Supply and generate a DC voltage for welding on the secondary side,
The driving pulse for turning on the switching element is set to a pulse width corresponding to the operation state at that time, and the output for controlling the output destination of the driving pulse to be switched to any one of the groups of the switching elements every control cycle A welding power supply device comprising a control circuit,
The output control circuit includes:
Zero width determination means for determining whether or not the pulse width of the drive pulse is zero width;
When the pulse width of the drive pulse is determined to be zero width by the zero width determination means, the operation of switching the output destination of the drive pulse is performed in order to maintain the output destination at the time of the zero width determination in the next control cycle. A welding power supply device comprising switching prohibiting means for temporarily prohibiting. In the welding power supply device according to claim 1,
The output control circuit internally generates a voltage corresponding to the pulse width of the drive pulse according to the operation status at that time,
The zero width determination means is composed of a comparator that compares a voltage corresponding to the pulse width of the drive pulse with a voltage corresponding to a zero width determination value, and outputs the comparison result as an output signal.
The switching prohibiting means comprises a logic gate circuit that generates an output signal for prohibiting the switching operation of the output destination of the drive pulse based on the output signal from the comparator. Power supply.   A welding machine configured to perform welding based on the welding DC voltage generated by the power supply device according to claim 1.

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