JP2010284709A - Power source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in which control of output current becomes unstable when the conduction time of an inverter circuit built in a power source device is near the minimum. <P>SOLUTION: The power source device is equipped with: a DC converting circuit that outputs a DC voltage by rectifying/smoothing a commercial AC power source; an inverter circuit for converting the DC voltage to a high frequency AC voltage; a transformer for converting the high frequency AC voltage to a voltage suitable for a load; an output control circuit that outputs an output control signal for controlling the inverter circuit; and a switching element driving circuit that drives the inverter circuit in accordance with the output control signal. In the power source device, the switching element driving circuit drives the inverter circuit by supplying a predetermined first driving voltage when the on-duty of the output control signal is less than the predetermined reference value, and by increasing the first driving voltage from the point when the on-duty of the output control signal exceeds the reference value and supplying it as a predetermined second driving voltage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a switching element driving circuit for driving a switching element of an inverter circuit built in a power supply device.

  When the on-duty of the switching element of the inverter circuit built in the power supply apparatus becomes very small, stable control in a small current region becomes difficult due to the delay of turn-off of the switching element.

  FIG. 8 is an electrical connection diagram of a conventional welding power source. In the figure, the DC conversion circuit is formed of a rectifier circuit DR1 and a smoothing capacitor C1 provided in parallel on the output side.

  The inverter circuit INV forms a full bridge from the opposing first switching element TR1 to fourth switching element TR4 (not shown), converts a DC voltage into a high-frequency AC voltage, and outputs it.

  The transformer INT converts the high-frequency AC voltage converted by the inverter circuit INV into a high-frequency AC voltage suitable for arc machining, and the secondary rectifier circuit DR2 rectifies the output of the main transformer INT and passes through the DC reactor DCL. Electric power is supplied between the consumable electrode 1 and the workpiece M to generate an arc.

  The output current detection circuit ID detects the output current on the secondary side of the main transformer INT and outputs it as an output current detection signal Id. The output control circuit SC performs PWM control for modulating the pulse width with a constant pulse frequency, and outputs the first output control signal Sc1 and the second output control signal Sc2 that are shifted from each other by a half cycle according to the output current detection signal Id. Control the pulse width.

  FIG. 9 is a detailed diagram of a first switching element driving circuit SD1 of the prior art that uses a pulse transformer. The first switching element driving circuit SD1 is a primary that conducts in response to a first output control signal Sc1. A predetermined voltage is applied to the primary winding of the pulse transformer T1 according to the conduction of the drive switching element TR9 and the primary drive switching element TR9, and an induced electromotive voltage is generated according to the applied voltage, and the pulse transformer T2 Output to the secondary winding. Subsequently, the secondary drive switching element TR10 is cut off in accordance with the induced electromotive voltage, and a forward bias is applied to the first switching element TR1 forming the inverter circuit to conduct. Since the second switching element drive circuit SD2 to the fourth switching element drive circuit SD4 (not shown) have the same configuration as the first switching element drive circuit SD1, description of the operation is omitted.

Next, the operation of the prior art will be described with reference to FIG.
The main control circuit SC shown in FIG. 8 controls the pulse widths of the first output control signal Sc1 and the second output control signal Sc2 that are shifted from each other by a half cycle according to the output current detection signal Id. When the first output control signal Sc1 is input from the main control circuit SC shown in the figure to the first switching element driving circuit SD1 and the fourth switching element driving circuit SD4, the first switching driving signal Sd1 and the fourth switching driving signal SD1 The switching drive signal Sd4 is output, and the first switching element TR1 and the fourth switching element TR4 that form opposite sides are made conductive.

Subsequently, when the second output control signal Sc2 is input from the main control circuit SC to the second switching element driving circuit SD2 and the third switching element driving circuit SD3, the second switching driving signal Sd2 and the third switching element driving circuit SD3 are input. The switching drive signal Sd3 is output to conduct the second switching element TR2 and the third switching element TR3 that form opposite sides.
(For example, Patent Document 1)

JP 59-104830 A

  The conventional switching element driving circuit shown in FIG. 9 is provided with a reverse bias power source on the negative side of the pulse transformer T2, and applies a sufficient positive voltage (saturation voltage) between the gate and the emitter of the switching element. Stable operation was performed in the saturation region. At this time, since the gate charge capacity of the charge stored in the gate of the switching element is large, it takes a long time to discharge and the turn-off is slightly delayed, but the on-duty of the output control signal for controlling the inverter circuit is relatively large. The effects of turn-off delays are negligible.

  However, in the welding power source shown in FIG. 8, when the consumable electrode 1 and the workpiece M are short-circuited during arc generation, the arc voltage (for example, near 1 V) and the arc current (for example, near 40 A) at the time of this short-circuiting. Many times occur. At this time, the on-duty of the output control signal for controlling the inverter circuit is reduced to the minimum vicinity. When this on-duty is close to the minimum, the effect of the switching element turn-off delay cannot be ignored, the output control signal that controls the inverter circuit falls into intermittent operation, the arc voltage that is often generated at the time of a short circuit is low, and the arc current is low. When it is small, there arises a problem that stable control cannot be performed.

  Therefore, an object of the present invention is to provide a power supply apparatus that can perform stable control even when the on-duty of an output control signal that controls an inverter circuit is in the vicinity of the minimum.

  In order to solve the above-described problems, a first invention is an inverter circuit comprising a DC conversion circuit that rectifies and smoothes a commercial AC power supply and outputs a DC voltage, and a switching element that converts the DC voltage into a high-frequency AC voltage. A transformer for converting the high-frequency AC voltage into a voltage suitable for a load, an output control circuit for outputting an output control signal for controlling the inverter circuit, and switching for driving the inverter circuit in accordance with the output control signal In the power supply device including the element driving circuit, the switching element driving circuit supplies a predetermined first driving voltage when an on-duty of the output control signal is less than a predetermined reference value, and the output control signal When the on-duty exceeds the reference value, the first drive voltage is increased and supplied as a predetermined second drive voltage. Driving the inverter circuit, a power supply device according to claim.

  According to a second aspect of the invention, the first drive voltage is an active voltage that is energized in an active region that exceeds a threshold voltage of a switching element that forms the inverter circuit, and the second drive voltage is the switching voltage. 2. The power supply device according to claim 1, wherein the element has a saturation voltage value at which the element conducts in a saturation region.

  According to a third aspect of the present invention, the second drive voltage is increased to a predetermined drive voltage by increasing the first drive voltage at a predetermined voltage increase rate when the on-duty of the output control signal exceeds the reference value. The power supply device according to claim 1, wherein when it reaches, the rise in the voltage is stopped.

  The fourth invention is characterized in that the second drive voltage becomes higher based on the on-duty value of the output control signal when the on-duty of the output control signal is equal to or higher than the reference value. It is a power supply device of description.

  A first invention and a second invention are switching element driving circuits for driving a switching element forming an inverter circuit, wherein the gate-emitter driving voltage applied to the switching element is divided into two stages, for example, the first driving Output control for controlling the inverter circuit by setting the voltage as an active voltage that is energized in an active region that exceeds a threshold voltage at which the switching element starts to conduct and the second drive voltage as a saturation voltage that causes the switching element to be conducted in the saturation region When the on-duty of the signal is higher than a predetermined reference value, stable control is possible even when the output current is at the maximum rating by applying the second drive voltage between the gate and emitter of the switching element and conducting in saturation. become. Furthermore, when the on-duty of the output control signal for controlling the inverter circuit is reduced to the minimum value, it is applied between the gate and the emitter of the switching element of the first driving voltage, and is conducted in the active state, thereby switching the switching element. As the speed increases, intermittent operation of the output control signal can be prevented, and stable control can be performed even when the on-duty is near the minimum.

  According to a third aspect of the present invention, when the first drive voltage is increased from the first drive voltage to the second drive voltage, the first drive voltage is gradually increased with a predetermined voltage increase rate (dv / dt). Hunting of the output current generated when switching to the drive voltage of 2 can be suppressed.

  According to a fourth aspect of the present invention, when the on-duty of the output control signal for controlling the inverter circuit becomes equal to or higher than the reference value, the second drive voltage is increased based on the on-duty value of the output control signal, thereby The amount of charge to be charged is controlled in accordance with the output current, and accurate output control is possible.

It is an electrical connection figure of the power supply device which concerns on Embodiment 1 of this invention. FIG. 2 is a detailed diagram of the switching element driving circuit shown in FIG. 1. FIG. 6 is a waveform timing diagram for explaining the operation when the on-duty of the first embodiment is large. FIG. 6 is a waveform timing diagram for explaining an operation when the on-duty in the first embodiment is small. It is a Vce-Ic characteristic view of a switching element (IGBT). 6 is a detailed diagram of a switching element driving circuit according to Embodiment 2. FIG. 6 is a detailed diagram of a switching element driving circuit according to Embodiment 2. FIG. It is an electrical connection diagram of the power supply device of a prior art. It is detail drawing of the switching element drive circuit of a prior art.

FIG. 1 is an electrical connection diagram of the power supply device according to Embodiment 1 of the present invention.
In the figure, components having the same reference numerals as those in the electrical connection diagram of the prior art power supply device shown in FIG. 8 perform the same operations, and therefore description thereof will be omitted, and only components having different reference numerals will be described.

The inverter control circuit (not shown) is formed by the first switching element drive circuit DK1 to the fourth switching element drive circuit DK4 shown in FIG. 1, and FIG. 2 shows the first switching element drive circuit DK1 and the second switching element. FIG. 4 is a detailed diagram of a drive circuit DK2.
The first switching element drive circuit DK1 shown in FIG. 2 has a primary drive switching element TR5 that is turned on / off according to the first output control signal Sc1, and a predetermined value according to the conduction of the primary drive switching element TR5. Is applied to the primary winding of the pulse transformer T1, and in response to this applied voltage, a first induced electromotive voltage is generated in the first secondary winding of the pulse transformer T1 and the second secondary winding is generated. A pulse transformer T1 for generating a second induced electromotive voltage, a first secondary drive switching element TR6 for energizing a first drive voltage predetermined in response to the generation of the first induced electromotive voltage, and a second The on-duty of the induced electromotive voltage is discriminated, and when the on-duty is less than a predetermined value, the supply of the second induced electromotive voltage is stopped, and when the on-duty exceeds the predetermined value, the second inductive voltage is supplied. The determination circuit GD1, the second secondary drive switching element TR7 that supplies a second drive voltage higher than the first drive voltage in response to the supply of the second induced electromotive voltage, and the first secondary drive switching element With the third secondary drive switching element TR8 in which the output side of TR6 and the second secondary drive switching element TR7 are OR-connected through a diode, and the low side operation is performed according to the OR-calculated drive voltage. It is formed.
The second switching element drive circuit DK2, the third switching element drive circuit DK3, and the fourth switching element drive circuit DK4 shown in FIGS. 1 and 2 have the same configuration as the first switching element drive circuit DK1. Therefore, explanation is omitted.

FIG. 3 is a waveform timing chart for explaining the operation when on-duty is larger than a predetermined reference value in the first embodiment of the present invention.
In FIG. 3, the waveform of FIG. 3A shows the first output control signal Sc1, the waveform of FIG. 3B shows the second output control signal Sc2, and the waveform of FIG. 1 shows a first switching drive signal Dk1, the waveform of FIG. 2D shows the second switching drive signal Dk2, and the waveform of FIG. 2E shows the first 2 that forms the first switching element drive circuit DK1. The gate signal Tr6 of the secondary drive switching element TR6 is shown, and the waveform of FIG. 8F shows the gate signal Tr7 of the second secondary drive switching element TR7 forming the first switching element drive circuit DK1, and FIG. The waveform of j) shows the gate signal Tr10 of the first secondary drive switching element TR10 that forms the second switching element drive circuit DK2, and the waveform of (h) in the figure shows the second switching element drive circuit DK2. Shows a second gate signal Tr11 secondary drive switching elements TR11 to formed.

Next, the operation of the present invention will be described with reference to the waveform timing chart of FIG. 3 and the Vce-Ic characteristic diagram of the switching element of FIG.
When the start signal Ts is output from the start switch TS shown in FIG. 1, the output control circuit SC sets the current reference value Ir and the output current detection signal Id to a value (for example, Ir-Id) obtained by comparing and calculating. The first output control signal Sc1 shown in FIG. 3 (a) and the second output control signal Sc2 shown in FIG.

  At time t = t1 shown in FIG. 3, the first output control signal Sc1 shown in FIG. 3A becomes High level, and the primary drive switching element TR5 of the first switching element drive circuit DK1 shown in FIG. When conducting, the primary drive switching element TR5 applies a predetermined primary voltage to the primary winding N1 of the pulse transformer T1, and the pulse transformer T1 receives the first voltage when the primary voltage is applied to the primary winding N1. The first induced electromotive voltage is generated in the secondary winding N2, and the second induced electromotive voltage is generated in the second secondary winding N3.

At time t = t1, the gate signal Tr6 shown in FIG. 3 (e) is input to the first secondary drive switching element TR6 in accordance with the first induced electromotive voltage and becomes conductive. When the first secondary drive switching element TR6 is turned on, the first drive voltage (for example, 9V) is applied to cut off the third secondary drive switching element TR8. Then, the first switching element TR1 is driven by receiving the first switching drive signal Dk1 shown in FIG. At this time, for example, a first drive voltage that is changed from a negative voltage (−8V) to a positive voltage (+ 9V) is applied to the gate of the first switching element TR1, and the first switching element TR1 becomes conductive in an active state.
At this time, the first drive voltage (9 V) is an activity exceeding the threshold voltage at which the first switching element forming the inverter circuit starts to conduct from the Vce-Ic characteristic diagram of the switching element shown in FIG. This is the gate voltage of the region, and in a short circuit state that occurs during arc generation (not shown), the arc voltage (for example, around 1 V) is a value (100 A) that can sufficiently supply the arc current with respect to the arc current (for example, around 40 A). Selected.

  When the second induced electromotive voltage is input to the on-duty discrimination circuit GD1 at time t = t1, the on-duty discrimination circuit GD1 compares the time of the second induced electromotive voltage with a predetermined time T1 (for example, 1 μs), it is determined that the on-duty is larger than a predetermined reference value, and at time t = t2, the second secondary drive switching element TR7 is turned on. The gate signal Tr7 shown in FIG. Generate and output.

  At time t = t2, when the gate signal Tr7 shown in FIG. 3 (f) is input to the second secondary drive switching element TR7 and becomes conductive, the second drive voltage (for example, 16V) is energized, and the diode D2 and the diode An OR logic of the first drive voltage and the second drive voltage is performed via D3, and the voltage of the first switching drive signal Dk1 shown in FIG. 10C is increased from (9V) to (16V)). To do. At this time, as shown in FIG. 5, the second drive voltage (16V) is a saturation voltage at which the first switching element TR1 forming the inverter circuit is in a saturated state, and the output current supplied to the load is the maximum rating. It is a value that can be supplied up to.

  At time t = t3, when the first output control signal Sc1 shown in FIG. 3A becomes low level, the primary drive switching element TR5 is cut off, and the primary voltage is applied to the primary winding N1 of the pulse transformer T1. Stops.

  When application of the primary voltage to the primary winding N1 of the pulse transformer T1 shown in FIG. 2 stops at time t = t3, the first induced electromotive voltage and the second secondary voltage of the first secondary winding N2 Generation of the second induced electromotive voltage of the winding N3 is stopped. At this time, the supply of the first drive voltage and the second drive voltage to the third secondary drive switching element TR8 is stopped, and the third secondary drive switching element TR8 becomes conductive. When the third secondary drive switching element TR8 is turned on, a negative voltage (for example, −8V) is supplied from the reverse bias power source, and the voltage of the first switching drive signal Dk1 is changed from the positive voltage to the negative voltage as shown in FIG. The voltage changes (for example, from + 16V to −8V), and the first switching element TR1 shown in FIG. 1 is cut off.

  At time t = t4 shown in FIG. 3, the second output control signal Sc2 shown in FIG. 3B becomes High level, and the primary drive switching element TR9 of the second switching element drive circuit DK2 shown in FIG. When conducting, the primary drive switching element TR9 applies a predetermined primary voltage to the primary winding N1 of the pulse transformer T1, and the pulse transformer T1 receives the first voltage when the primary voltage is applied to the primary winding N1. A first induced electromotive voltage is generated in the secondary winding N2, and a second induced electromotive voltage is generated in the second secondary winding N3.

  At time t = t4, the gate signal Tr10 shown in FIG. 3 (j) is input to the first secondary drive switching element TR10 in accordance with the first induced electromotive voltage and becomes conductive. When the first secondary drive switching element TR10 is turned on, a first drive voltage (for example, 9V) is supplied to cut off the third secondary drive switching element TR12. The second switching element TR2 is driven by inputting the second switching drive signal Dk2 in FIG. At this time, for example, a first drive voltage that is changed from a negative voltage (−8 V) to a positive voltage (+9 V) is applied to the gate of the second switching element TR <b> 2 to be conductive.

  When the second induced electromotive voltage is input to the on-duty discrimination circuit GD2 at time t = t4, the on-duty discrimination circuit GD2 determines that the second induced electromotive voltage has the first time when the predetermined time T1 has elapsed. 2 generates and outputs the gate signal Tr10 shown in FIG. 3 (h) for conducting the secondary drive switching element TR10.

  At time t = t5, when the gate signal Tr11 shown in FIG. 4 (h) is input to the second secondary drive switching element TR11 and becomes conductive, the second drive voltage (for example, 16V) is supplied to the diode D2 and An OR logic of the first drive voltage and the second drive voltage is performed via the diode D3, and the voltage of the second switching drive signal Dk2 shown in FIG. 4 (d) is increased from (9V) to (16V). To do. At this time, as shown in FIG. 5, the second drive voltage (16V) is a saturation voltage at which the second switching element TR2 forming the inverter circuit conducts in a saturated state, and the output current supplied to the load is the maximum rating. It is a value that can be supplied up to.

  At time t = t6, when the second output control signal Sc2 shown in FIG. 3B becomes low level, the primary drive switching element TR9 is cut off, and the primary voltage is applied to the primary winding N1 of the pulse transformer T2. Stops.

  When application of the primary voltage to the primary winding N1 of the pulse transformer T2 shown in FIG. 2 stops at time t = t6, the first induced electromotive voltage and the second secondary voltage of the first secondary winding N2 The generation of the second induced electromotive voltage of the winding N3 is stopped. At this time, the supply of the first drive voltage and the second drive voltage to the third secondary drive switching element TR12 is stopped, and the third secondary drive switching element TR12 becomes conductive. When the third secondary drive switching element TR12 is turned on, a negative voltage (for example, −8V) is supplied from the reverse bias power source, and the voltage of the second switching drive signal Dk2 is changed from the positive voltage to the negative voltage as shown in FIG. The voltage is changed (for example, from + 16V to −8V), and the second switching element TR2 shown in FIG. 1 is cut off. Thereafter, the same operation as described above is performed.

  In the above, when the on-duty of the output control signal for controlling the inverter circuit is equal to or higher than a predetermined reference value, the second drive voltage (16 V) is applied between the gate and the emitter of the switching element, and the switching element is saturated in the saturated state. Conduction enables stable control even when the output current is at the maximum rating.

FIG. 4 is a waveform timing diagram illustrating an operation when the on-duty is less than a predetermined reference value in the first embodiment of the present invention.
4, the waveform of FIG. 4A shows the first output control signal Sc1, the waveform of FIG. 4B shows the output control signal Sc2 of 2, and the waveform of FIG. 4C shows the first output control signal Sc2. The switching drive signal Dk1 is shown, the waveform of FIG. 4D shows the second switching drive signal Dk2, and the waveform of FIG. 4E is the first secondary drive that forms the first switching element drive circuit DK1. The gate signal Tr6 of the switching element TR6 is shown, and the waveform of FIG. 8F shows the gate signal Tr7 of the second secondary drive switching element TR7 forming the first switching element drive circuit DK1, and FIG. The waveform of (2) shows the gate signal Tr10 of the first secondary drive switching element TR10 that forms the second switching element drive circuit DK2, and the waveform of (h) in the figure shows the second switching element drive circuit DK2. Shows a second gate signal Tr11 secondary drive switching elements TR11 to formed.

  At time t = t1 shown in FIG. 4, the first output control signal Sc1 shown in FIG. 4A becomes High level, and the primary drive switching element TR5 of the first switching element drive circuit DK1 shown in FIG. When conducting, the primary drive switching element TR5 applies a predetermined primary voltage to the primary winding N1 of the pulse transformer T1, and the pulse transformer T1 has the first voltage applied to the primary winding N1. A first induced electromotive voltage is generated in the secondary winding N2, and a second induced electromotive voltage is generated in the second secondary winding N3.

  At time t = t1, the gate signal Tr6 shown in FIG. 4 (e) is input to the first secondary drive switching element TR6 in accordance with the first induced electromotive voltage and is turned on. When the first secondary drive switching element TR6 is turned on, the first drive voltage (for example, 9V) is applied to cut off the third secondary drive switching element TR8. Then, the first switching element TR1 is driven by receiving the first switching drive signal Dk1 shown in FIG. At this time, for example, a first drive voltage that is changed from a negative voltage (−8V) to a positive voltage (+ 9V) is applied to the gate of the first switching element TR1, and the first switching element TR1 becomes conductive in an active state.

  When the second induced electromotive voltage is input to the on-duty discriminating circuit GD1 at time t = t1, the on-duty discriminating circuit GD1 determines whether the time of the second induced electromotive voltage is equal to or longer than a predetermined time T1 (for example, 1 μs). Start the determination. When the second induced electromotive voltage is input to the on-duty discriminating circuit GD1 at time t = t1, the on-duty discriminating circuit GD1 is shorter than the predetermined time T1 (for example, 1 μs). Sometimes, it is determined that the on-duty is less than a predetermined reference value, and at time t = t2, the cutoff state of the second secondary drive switching element TR7 is continued. At this time, the first switching element TR1 conducts in an active state.

  At time t = t2, when the first output control signal Sc1 shown in FIG. 4A becomes low level, the primary drive switching element TR5 is cut off, and the primary voltage is applied to the primary winding N1 of the pulse transformer T1. Is stopped, the generation of the first induced electromotive voltage of the first secondary winding N2 and the second induced electromotive voltage of the second secondary winding N3 is stopped. At this time, since the time of the second induced electromotive voltage is shorter than the predetermined time T1 in the on-duty determination circuit GD1 shown in FIG. 2, the on-duty of the first output control signal Sc1 shown in FIG. The gate signal Tr7 shown in FIG. 4 (f) is not input to the second secondary drive switching element TR7, and the second drive voltage (for example, 16V) is prohibited from being energized. The first drive voltage (9V) is supplied through the diode D2, and the first switching drive signal Dk1 is input to the first switching element TR1 in FIG. 5C, and the conductive state is kept active until time t = t2. continue.

During the time t = t1 to t2, the output voltage (9V) of the first switching drive signal Dk1 is input to the first switching element TR1 shown in FIG. At this time, when the first switching element TR1 is turned off at time t = t2, the amount of charge on the gate is suppressed, so that the electric charge is discharged quickly and the turn-off is quickened.
Therefore, the consumable electrode 1 and the workpiece M are short-circuited during arc generation, the arc voltage becomes (eg, near 1 V), the arc current becomes (eg, around 40 A), and the output control signal for controlling the inverter circuit is turned on. Even in the vicinity of the minimum, intermittent operation can be prevented and stable control becomes possible. Further, when the switching element forming the inverter is operated in the active state, the loss increases. However, since the switching element is operated in the active state in the vicinity of the on-duty of the output control signal for controlling the inverter circuit, the effect of the increase in loss is It becomes almost zero.

  FIG. 6 is a detailed diagram of the switching element driving circuit according to the second embodiment. In the figure, components having the same reference numerals as those in the electrical connection diagrams of the welding power source apparatus shown in FIGS. 1, 2 and 8 perform the same operations, and thus the description thereof will be omitted.

  When the time of the second induced electromotive voltage is longer than the predetermined time T1, the second on-duty determination circuit GD2 shown in FIG. 6 determines that the on-duty of the output control signal is equal to or greater than the predetermined reference value, and the time T1 is When the time has elapsed, the second secondary drive switching element TR7 is turned on, and the on-duty discrimination signal Gd2 is set to High level and output.

  The step-up / down circuit DV shown in FIG. 6 steps down and outputs the DC voltage (16V) to (9V) when the on-duty discrimination signal Gd2 from the second on-duty discrimination circuit GD2 is at a low level, and the on-duty discrimination signal Gd2 When the Low level is changed to the High level, the output voltage (9 V) is gradually increased by a predetermined voltage increase rate (dv / dt) and increased to (16 V).

Next, the operation will be described.
When the first output control signal Sc1 shown in FIG. 6 becomes High level, the primary drive switching element TR5 of the first switching element drive circuit DK1 becomes conductive, and the primary drive switching element TR5 becomes the primary of the pulse transformer T1. When a predetermined primary voltage is applied to the winding N1 and the primary voltage is applied to the primary winding N1, the pulse transformer T1 generates a first induced electromotive voltage in the first secondary winding N2. A second induced electromotive voltage is generated in the second secondary winding N3.

  In response to the first induced electromotive voltage, the first secondary drive switching element TR6 is turned on, the first drive voltage (9V) is applied to cut off the third secondary drive switching element TR8, and the first The drive voltage of the switching drive signal Dk1 is applied (9V) to the switching element and is made conductive in the active state.

  The second on-duty discrimination circuit GD2 discriminates that the on-duty of the first output control signal is less than the reference value when the time of the second induced electromotive voltage is shorter than the predetermined time T1, and the second secondary drive switching The element TR7 is shut off and the output of the on-duty discrimination signal Gd2 is also stopped. At this time, the step-up / down circuit DV supplies a DC voltage of (9 V) to the collector side of the second secondary drive switching element TR7.

  Next, the second on-duty discrimination circuit GD2 discriminates that the on-duty of the output control signal is equal to or greater than the reference value when the time of the second induced electromotive voltage is longer than the predetermined time T1, and the second secondary drive switching is performed. The device TR7 is turned on and the on-duty discrimination signal Gd2 is set to the high level and output.

  The step-up / down circuit DV shown in FIG. 6 gradually increases the drive voltage from (9V) to (16V) at a predetermined voltage increase rate when the on-duty determination signal Gd2 becomes High level, and the first switching drive signal Dk1 When the drive voltage reaches (16V), the rise is stopped and applied to the switching element to conduct. At this time, the conduction of the switching element shifts from the active state to the saturated state.

  From the above, when the first drive voltage is increased from the first drive voltage to the second drive voltage, the first drive voltage (9V) is increased to the second drive voltage by gradually increasing the voltage with a predetermined voltage increase rate (dv / dt). Hunting of the output current generated when switching to the drive voltage (16V) of 2 can be suppressed.

  FIG. 7 is a detailed diagram of the switching element driving circuit according to the third embodiment. In the same figure, components having the same reference numerals as those in the electrical connection diagrams of the welding power source apparatus shown in FIGS. 1, 2, 6 and 8 perform the same operations, and thus the description thereof will be omitted. explain.

  When the on-duty discrimination signal Gd2 from the second on-duty discrimination circuit GD2 is at a low level, the on-duty-compatible DC power supply circuit FV shown in FIG. 7 outputs a DC voltage, for example, (9V), and the on-duty discrimination signal Gd2 is High. When the level is reached, the DC voltage is increased based on the on-duty value of the first output control signal Sc1.

Next, the operation will be described.
When the first output control signal Sc1 shown in FIG. 7 becomes High level, the primary drive switching element TR5 of the first switching element drive circuit DK1 becomes conductive, and the primary drive switching element TR5 becomes the primary of the pulse transformer T1. When a predetermined primary voltage is applied to the winding N1 and the primary voltage is applied to the primary winding N1, the pulse transformer T1 generates a first induced electromotive voltage in the first secondary winding N2. A second induced electromotive voltage is generated in the second secondary winding N3.

  In response to the first induced electromotive voltage, the first secondary drive switching element TR6 is turned on, the first drive voltage (9V) is applied to cut off the third secondary drive switching element TR8, and the first The drive voltage of the switching drive signal Dk1 (9V) is applied to the switching element to conduct in the active state.

  The second on-duty discrimination circuit GD2 discriminates that the on-duty of the first output control signal is less than the reference value when the time of the second induced electromotive voltage is shorter than the predetermined time T1, and the second secondary drive switching The element TR7 is shut off and the output of the on-duty discrimination signal Gd2 is also stopped. At this time, the on-duty compatible DC power supply circuit FV sets the DC voltage to (9 V) and outputs it to the collector side of the second secondary drive switching element TR7 when the on-duty discrimination signal Gd2 is at the low level.

  Next, the second on-duty discrimination circuit GD2 discriminates that the on-duty of the output control signal is equal to or greater than the reference value when the time of the second induced electromotive voltage is longer than the predetermined time T1, and the second secondary drive switching is performed. The element TR7 is turned on and the on-duty discrimination signal Gd2 is set to the high level.

  The on-duty compatible DC power supply circuit FV shown in FIG. 7 increases the DC voltage from (9V) to (16V), for example, based on the on-duty value of the first output control signal Sc1 when the on-duty determination signal Gd2 becomes high level. And output.

  As described above, when the on-duty of the output control signal of the inverter circuit becomes equal to or higher than the reference value, the second drive voltage can be set to an optimum value based on the on-duty value of the output control signal.

AC commercial AC power supply C1 smoothing capacitor DCL DC reactor DV step-down circuit DR1 primary rectifier circuit DR2 secondary rectifier circuit DK1 first switching element drive circuit (invention circuit)
DK2 Second switching element driving circuit (present circuit)
DK3 Third switching element driving circuit (invention circuit)
DK4 Fourth switching element driving circuit (invention circuit)
Dk1 first switching element drive signal (invention circuit)
Dk2 Second switching element drive signal (present circuit)
Dk3 Third switching element drive signal (invention circuit)
Dk4 Fourth switching element drive signal (circuit of the present invention)
FV On-duty compatible DC power supply circuit GD On-duty discrimination circuit GD2 Second on-duty discrimination circuit ID Input current detection circuit Id Input current detection signal IR Output current setting circuit Ir Output current setting signal INT Transformer M Workpiece SC Main control circuit Sc1 First 1 output control signal Sc2 second output control signal SD1 first switching element driving circuit (conventional circuit)
SD2 Second switching element driving circuit (conventional circuit)
SD3 Third switching element driving circuit (conventional circuit)
SD4 Fourth switching element driving circuit (conventional circuit)
Sd1 First switching element drive signal (conventional circuit)
Sd2 Second switching element drive signal (conventional circuit)
Sd3 Third switching element drive signal (conventional circuit)
Sd4 Fourth switching element drive signal (conventional circuit)
TH torch TS start switch Ts start signal TR1 first switching element TR2 second switching element TR3 third switching element TR4 fourth switching element

Claims (4)

A DC conversion circuit that rectifies and smoothes commercial AC power and outputs a DC voltage; an inverter circuit that includes a switching element that converts the DC voltage into a high-frequency AC voltage; and converts the high-frequency AC voltage into a voltage suitable for a load. A power supply apparatus comprising: a transformer; an output control circuit that outputs an output control signal that controls the inverter circuit; and a switching element drive circuit that drives the inverter circuit in response to the output control signal. The drive circuit supplies a predetermined first drive voltage when the on-duty of the output control signal is less than a predetermined reference value, and the first circuit voltage from when the on-duty of the output control signal exceeds the reference value. The drive voltage is increased and supplied as a predetermined second drive voltage to drive the inverter circuit. Source apparatus.   The first drive voltage is an active voltage that is energized in an active region that exceeds a threshold voltage of a switching element that forms the inverter circuit, and the second drive voltage is conductive in the saturation region of the switching element. The power supply device according to claim 1, wherein the power supply device has a saturation voltage value.   The second drive voltage increases the first drive voltage at a predetermined voltage increase rate from when the on-duty of the output control signal exceeds the reference value, and increases when the predetermined drive voltage is reached. The power supply device according to claim 1, wherein the power supply device is stopped.   2. The power supply device according to claim 1, wherein the second drive voltage becomes higher based on an on-duty value of the output control signal when an on-duty of the output control signal is equal to or higher than the reference value.

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