JP6081148B2 - Arc machining power supply - Google Patents

Description

The present invention, in the process generating the output power of the arc machining power supply apparatus, a luer chromatography click machining power supply apparatus comprising an inverter circuit for performing power conversion from DC power to high frequency AC power.

  As a power supply device including an inverter circuit, for example, an arc machining power supply device disclosed in Patent Document 1 is known. This power supply device converts input commercial AC power into DC power using a rectifier circuit, converts the converted DC power into high frequency AC power using a switching operation of an inverter circuit, and converts the converted high frequency AC power via a transformer. Is supplied to the secondary side and converted to DC output power suitable for arc processing such as arc welding on the secondary side. The output power is adjusted by controlling the switching operation of the inverter circuit.

  One of the switching controls of the inverter circuit is pulse width modulation control (PWM control). When the output power is increased from time to time, the ON time of the switching element of the inverter circuit is lengthened, and the ON pulse width of the control pulse signal output to the switching element is set to be wide. On the other hand, when the output power is reduced, the ON time of the switching element of the inverter circuit is shortened, and the ON pulse width of the control pulse signal output to the switching element is set to be narrow.

Japanese Patent Laying-Open No. 2005-279774 (FIG. 10 etc.)

By the way, when a high to medium output request is made, the on-pulse width of the control pulse signal output to the inverter circuit (switching element) is sufficiently wide so that the switching element can be sufficiently turned on.
However, when a request for a low output is generated, in the PWM control, the on-pulse width of the control pulse signal is set to be narrower, and thus the switching element may not be sufficiently turned on. This leads to output instability, transformer biasing factors, and the like, so that it is desired to drive the switching element stably when a low output is required.

The present invention was made to solve the above problems, even while meeting the low power requirements, for luer chromatography click processing can realize stable driving of the switching elements of the inverter circuit It is to provide a power supply device.

An arc machining power supply that solves the above problems is a full-bridge circuit configuration inverter circuit that performs power conversion from DC power to high-frequency AC power by an on / off operation of a switching element in the process of generating output power of the power supply apparatus, A control circuit that outputs a control pulse signal to the switching element to control the on / off operation of the switching element and controls the output power, and configured to generate DC output power for arc machining a is, the inverter circuit, the first switching element to the first upper arm, a third scan Lee switching element to the first lower arm, the second switching element to the second upper arm, the first to the second lower arm 4 switching elements are arranged, respectively, and the first and fourth switching elements form a set, and the second and third switching elements PWM control that converts a DC power into a high-frequency AC power by alternately switching each group, and the control circuit adjusts an ON pulse width of a control pulse signal output to the switching element. And a PDM control that adjusts the on-pulse density of the control pulse signal so that the on-pulse width of the control pulse signal is sufficiently large to enable the switching element to be turned on. A control switching unit is provided that performs the PWM control on the higher output side than the request and switches to the PDM control on the lower output side than the predetermined output request. The PDM control includes a constant period of the PWM control period corresponding to the PDM control period. And adjust the density of the on-pulses by thinning out any of the on-pulses in the PDM control cycle. Ku In includes a control pulse signal to be output to the first switching element and the fourth switching element, in which thinning similarly a control pulse signal to be output to the second switching element and the third switching element.

According to this configuration, PWM control for adjusting the on-pulse width of the control pulse signal output to the switching element of the inverter circuit is performed on the higher output side than the predetermined output request. On the other hand, on the lower output side than the predetermined output request, the on-pulse width of the control pulse signal is set to a predetermined width at which the switching element can be sufficiently turned on, and the PDM control is switched to adjust the on-pulse density of the control pulse signal. In other words, at the time of low output request, if the PWM pulse control is performed, the on-pulse width where the switching element cannot be turned on is switched to the PDM control so that the on-pulse width of the switching element is set to a predetermined width that can be sufficiently turned on. For low output requirements, the on-pulse itself is thinned out to adjust the on-pulse density. As a result, it is possible to realize stable driving of the switching elements of the inverter circuit while meeting low output requirements.
Further, in the PDM control, a fixed period of the PWM control period is set as the PDM control period, and any of the on-pulses in the PDM control period is thinned out to adjust the on-pulse density. That is, this PDM control can contribute to simplification of control because the PDM control cycle is performed at a constant PWM control cycle.

Further, in the arc machining power supply apparatus, the control switching unit causes the PWM control to be performed from a maximum width of an on-pulse width of the control pulse signal to a minimum width at which the switching element can be sufficiently turned on. When requested, it is preferable to switch to the PDM control for adjusting the density of the on-pulse while fixing the on-pulse width of the control pulse signal at a minimum width.

  According to this configuration, in the PWM control, the on-pulse width of the control pulse signal is performed from the maximum width to the minimum width at which the switching element can be sufficiently turned on. The on-pulse density is adjusted while the on-pulse width is fixed at the minimum width. That is, since the PWM control with a fine control cycle is performed in a wide range until the on-pulse width of the control pulse signal becomes the minimum width at which the switching element can be turned on, it can contribute to output stabilization. Further, since the on-pulse width is inherited with the minimum width when switching between PWM control and PDM control, it is possible to contribute to stabilization of output when switching control.

In the arc machining power supply apparatus, it is preferable that the PDM control adjusts the density of on-pulses by thinning out on-pulses sequentially from the rear end side of the PDM control cycle.
According to this configuration, in the PDM control, the on-pulse density is adjusted by thinning out the on-pulse in order from the rear end side of the PDM control cycle. That is, since the on-pulse is simply thinned out from the rear end side of the PDM control cycle, this can also contribute to simplification of the control.

According to arc machining power supply apparatus of the present invention can also while meeting the low power requirements, to achieve stable driving of the switching elements of the inverter circuit.

The circuit diagram which shows the power supply apparatus for arc welding in one Embodiment. FIG. 5 is a waveform diagram of various parts of the power supply device for PWM control when a high output is requested. The wave form diagram of each place of the power supply device at the time of the PWM-PDM criticality at the time of middle output request | requirement. The wave form diagram of each place of the power supply device concerning PDM control at the time of a low output request | requirement.

Hereinafter, an embodiment of a power supply apparatus for arc welding as a power supply apparatus will be described.
As shown in FIG. 1, the arc welding machine 10 connects the electrode WE of the welding torch TH to the positive output terminal o1 of the arc welding power supply device 11 used for this, and the welding target ( The base material M is connected, an arc is generated at the tip of the electrode WE based on the DC output power generated by the power supply device 11, and arc welding of the welding object M is performed. The arc welder 10 is, for example, a consumable electrode type arc welder, and since a wire electrode used as the electrode WE is consumed by an arc, a feeding device (not shown) that feeds the electrode WE according to the wear is provided. Use.

  The power supply apparatus 11 for arc welding includes an input conversion circuit 12, an inverter circuit 13, a transformer INT, and an output conversion circuit 14, and generates DC output power suitable for arc welding from input commercial AC power.

  The input conversion circuit 12 includes a primary side rectifier circuit DR1 formed of a diode bridge circuit and a smoothing capacitor C1 connected between output terminals of the rectifier circuit DR1, and converts three-phase commercial AC power into DC power. The DC input power is supplied to the subsequent inverter circuit 13.

  The inverter circuit 13 is configured by a full bridge circuit of first to fourth switching elements TR1 to TR4 made of a semiconductor switching element such as an IGBT. Incidentally, the first switching element TR1 in the first upper arm, the third switching element TR3 in the first lower arm, the second switching element TR2 in the second upper arm, and the fourth switching element TR4 in the second lower arm, respectively. It is arranged. Diodes D1 to D4 are reversely connected to the switching elements TR1 to TR4, respectively. The output terminal a of the inverter circuit 13 between the second and fourth switching elements TR2 and TR4 and the output terminal b between the first and third switching elements TR1 and TR3 are connected to the primary coil L1 of the transformer INT.

  In the inverter circuit 13, the first and fourth switching elements TR1 and TR4 form a pair, and the second and third switching elements TR2 and TR3 form a pair. The DC power input from the circuit 12 is converted into high-frequency AC power and supplied to the primary coil L1 of the transformer INT. Switching operations of these switching elements TR1 to TR4 are performed based on control pulse signals S1 to S4 input from the control circuit 20.

  On the secondary side of the transformer INT, the high-frequency AC power generated by the inverter circuit 13 is converted into a predetermined voltage and output from the secondary coil L2. The output conversion circuit 14 is connected to the secondary coil L2.

  The output conversion circuit 14 includes a secondary side rectifier circuit DR2 and a DC 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 11. The negative output terminal o2 of the power supply device 11 is connected to the intermediate terminal of the secondary coil L2. Such an output conversion circuit 14 converts high-frequency AC power from the secondary coil L2 of the transformer INT into DC output power for arc welding, and outputs it from the output terminals o1 and o2.

  The power supply device 11 is provided with a control circuit 20 including a CPU and the like. The control circuit 20 includes a detection signal Id corresponding to the output current Io from the current detector 21 installed on the output-side power line of the power supply device 11, and an output current target value from the output current setting device 22 that can be operated by a user or the like. And a setting signal Ir corresponding to. Based on various parameters including the actual value of the output current Io obtained from the input detection signal Id and the setting signal Ir and its target value, the control circuit 20 performs an internal calculation for performing an appropriate output from time to time. ing. Then, the control circuit 20 performs switching control on the switching elements TR1 to TR4 of the inverter circuit 13 based on the internal calculation.

  As the switching control of this embodiment, pulse width modulation (Pulse Width Modulation: PWM) control is used when high to medium output is required, and pulse density modulation (PDM) control is used when low output is required. The PWM control and the PDM control are appropriately switched. In this embodiment, first, in the pulse width setting unit 20a of the control circuit 20, based on the actual value and the target value of the output current Io, the on-pulse width Wm of the appropriate control pulse signals S1 to S4 (from time to time) Next, based on the calculated on-pulse width Wm, the control switching unit 20b switches between PWM control and PDM control.

Next, the operation (action) of the present embodiment will be described with reference to FIGS.
[When high to medium output is requested: PWM control]
The on-pulse width Wm of the control pulse signals S1 to S4 output to the inverter circuit 13 (switching elements TR1 to TR4) is calculated, and the calculated on-pulse width Wm is changed from the maximum width Wmx shown in FIG. 2 to the minimum width shown in FIG. When it is between Wm0, the calculated value is set as the on-pulse width Wm as it is. In other words, when the high to medium output is requested, the output of the power supply device 11 is adjusted by PWM control in which the on-pulse width Wm (PWM duty cycle) is adjusted between the maximum width Wmx and the minimum width Wm0.

2 and 3 (the same applies to FIG. 4 described later), the voltage between the output terminals a and b of the inverter circuit 13 is Vab, the current flowing through the switching elements TR1 and TR4 is _ITR1,4 , and the current flows through the switching elements TR2 and TR3. It is _assumed that the current is I _TR2,3 , the voltage applied to the switching elements TR1, TR4 is V _TR1,4 , and the voltage applied to the switching elements TR2, TR3 is V _TR2,3 . The output voltage Vab of the inverter circuit 13 changes according to the length of the ON pulse width Wm of the control pulse signals S1 to S4, thereby adjusting the output power of the power supply device 11 generated on the secondary side of the transformer INT.

  By the way, the minimum width Wm0 of the on-pulse width Wm of the control pulse signals S1 to S4 is set to a width that allows the switching elements TR1 to TR4 to be sufficiently turned on. That is, even if the on-pulse width Wm is set to the minimum width Wm0, the switching elements TR1 to TR4 are reliably turned on.

  On the other hand, if the on-pulse width Wm is smaller than the minimum width Wm0, the on-operation of the switching elements TR1 to TR4 cannot be compensated. For this reason, when the calculation of the on-pulse width Wm according to the output request becomes smaller than the minimum width Wm0, the on-pulse width Wm is fixed to the minimum width Wm0, and the process shifts to PDM control for adjusting the density of the on-pulse. In other words, in the above-described PWM control, an on opportunity is given every cycle, and the on-pulse density (PDM duty cycle) is 100%, which is the maximum.

[When requesting low output: PDM control]
When the calculated on-pulse width Wm becomes a calculated value smaller than the minimum width Wm0, the on-pulse width Wm is fixed at the minimum width Wm0, and the density of the on-pulse is set small. That is, at the time of this low output request, the output of the power supply device 11 is adjusted by PDM control in which the number of on pulses of the minimum width Wm0 is adjusted.

  Specifically, in the present embodiment, as shown in FIG. 4, 10 control pulse signals S1 to S4 have 10 on-pulses, that is, 10 PWM control cycles TW are one cycle of the PDM control cycle TD. The number to be thinned out is determined according to the calculated value of the previous on-pulse width Wm for each period TD. Within the calculated on-pulse width Wm, which is smaller than the minimum width Wm0, the number to be thinned out increases as it becomes smaller. Further, the unnecessary on-pulses are thinned out in order from the rear end of the PDM control cycle TD, and the on-pulse density is reduced. Further, the control pulse signals S1, S4 and the control pulse signals S2, S3 are thinned out in the same manner. Incidentally, in FIG. 4, the PDM duty cycle is 50%, and the first five on-pulses (fixed at the minimum width Wm0) are set as they are within one period of PDM control, and the latter five on-pulses are thinned out and disappeared. To do.

  Here, in the comparison between the present embodiment and the background art, in the background art, the on-pulse width of the control pulse signal is set to be narrow until the power supply device reaches the minimum output. It is unclear which switching element of the circuit cannot be turned on and which of the switching elements of the upper and lower arms of the inverter circuit (bridge circuit) cannot be turned on. That is, since the switching element cannot be turned on unexpectedly (uncontrollable), the balance of the polarity of power transmission to the transformer via the switching element is lost, and the magnetism is generated in the transformer.

  On the other hand, in the PDM control of this embodiment, since the control circuit 20 thins out the ON pulses of the control pulse signals S1 to S4, it is not unexpected that the switching elements TR1 to TR4 are not turned on. Incidentally, in this embodiment, the control pulse signals S1 and S4 and the control pulse signals S2 and S3 are thinned out in the same manner. For this reason, even when there is a period during which the switching elements TR1 to TR4 are not turned on, the occurrence of magnetic bias in the transformer INT is suppressed as much as possible.

  In this way, even when a low output request is made that is smaller than the minimum width Wm0 as the calculated value of the on-pulse width Wm of the control pulse signals S1 to S4, the on-pulse width Wm is fixed at the minimum width Wm0. By realizing the stable driving of the switching elements TR1 to TR4 and reducing the on-pulse density by thinning the on-pulse itself as appropriate, the on-pulse width Wm is made wider as the minimum width Wm0 than the calculated value according to the output request. The power supply device 11 is capable of stable low output according to the output request up to the minimum output.

  Incidentally, as shown in FIG. 4, the output voltage Vab of the inverter circuit 13 with respect to the individual on pulses of the control pulse signals S1 to S4 is the same as that in FIG. 3 at the time of the PWM-PDM control critical, but the amount obtained by thinning the on pulse from there. The average voltage of the output voltage Vab decreases. Therefore, the output power of the power supply device 11 generated on the secondary side of the transformer INT is also low output.

Next, characteristic effects of the present embodiment will be described.
(1) On the higher output side than the predetermined output request, PWM control for adjusting the on-pulse width Wm of the control pulse signals S1 to S4 output to the switching elements TR1 to TR4 of the inverter circuit 13 is performed. On the other hand, on the lower output side than the predetermined output request, the on pulse width Wm of the control pulse signals S1 to S4 is set to a predetermined width (minimum width Wm0) in which the switching elements TR1 to TR4 can be sufficiently turned on. Can be switched to PDM control for adjusting the density of on-pulses. That is, at the time of a low output request, the on-pulse width Wm of the switching elements TR1 to TR4 is set by switching to the PDM control where the on-pulse width Wm is set so that the switching elements TR1 to TR4 cannot be turned on if PWM control is performed. Is secured as a predetermined width (minimum width Wm0) that can be sufficiently turned on, and for low output requirements, the on-pulse density is adjusted by thinning out the on-pulse itself. Thereby, the stable drive of switching element TR1-TR4 of the inverter circuit 13 is realizable, responding to a low output request | requirement.

  In particular, in the case of the arc welding power supply device 11 as in the present embodiment, the stable driving of the switching elements TR1 to TR4 of the inverter circuit 13 greatly affects the welding performance, and becomes a factor of demagnetization when the transformer INT is used. The significance of application to the power supply apparatus 11 for arc welding as in this embodiment is significant.

  (2) In the PWM control, the ON pulse width Wm of the control pulse signals S1 to S4 is performed from the maximum width Wmx to the minimum width Wm0 where the switching elements TR1 to TR4 can be sufficiently turned on. The on-pulse density is adjusted while the on-pulse width Wm of the control pulse signals S1 to S4 is fixed at the minimum width Wm0. That is, since the PWM control with a fine control cycle (TW) is performed in a wide range until the ON pulse width Wm of the control pulse signals S1 to S4 becomes the minimum width Wm0 that can be turned ON of the switching elements TR1 to TR4, the output stability is improved. Contributes to Further, when the PWM control and the PDM control are switched, the on-pulse width Wm is inherited with the minimum width Wm0, which contributes to the stabilization of the output when the control is switched.

  (3) In the PDM control, a fixed period of the PWM control period TW is set as the PDM control period TD, and any on-pulses in the PDM control period TD are thinned out to adjust the density of the on-pulses. That is, this PDM control contributes to simplification of control because the PDM control cycle TD is performed at a constant cycle of the PWM control cycle TW.

  (4) In the PDM control, the on-pulse density is adjusted by thinning out the on-pulse in order from the rear end side of the PDM control cycle TD. That is, since the on-pulse is simply thinned out from the rear end side of the PDM control cycle TD, this can also contribute to the simplification of the control.

In addition, you may change the said embodiment as follows.
Although the PDM control cycle TD is set to be constant at 10 cycles of the PWM control cycle TW, the number of cycles of the PWM control cycle TW is not limited to this, and may be set to other cycle numbers. Further, the predetermined number of PWM control cycles TW may not be constant, and the number of cycles of the PWM control cycle TW may be changed from time to time.

  The on-pulse is thinned out sequentially from the rear end of the PDM control cycle TD, but it may be thinned out sequentially from the front end or may be thinned out from an appropriate place. In this case, thinning may be performed so that the interval between on-pulses is the same (so that the difference in the interval between on-pulses is small).

  Switching between PWM control and PDM control is performed on the boundary that the calculation of the on-pulse width Wm of the control pulse signals S1 to S4 reaches the minimum width Wm0. In the PDM control, the minimum width Wm0 is used, but the switching element TR1 As long as .about.TR4 can be turned on, a predetermined width other than the minimum width Wm0 may be used. Further, the on-pulse width Wm may not be inherited by the PWM control and the PDM control, and the on-pulse width Wm may be set uniquely in the PDM control if the switching elements TR1 to TR4 can be turned on.

  The control is not switched based on the magnitude of the calculated value of the on-pulse width Wm of the control pulse signals S1 to S4 as the output request, but the magnitude of the actual output value such as the output current Io detected by the current detector 21 The control may be switched based on the output target value such as the output current target value by the output current setting unit 22.

The power supply device 11 is a power supply device for arc welding, but may be a power supply device for arc processing other than arc welding or other power supply devices.
Next, a technical idea that can be grasped from the above embodiment and another example will be added below.

(A) In the process of generating output power of the power supply device, a control pulse signal is output to the switching element for an inverter circuit having a full bridge circuit configuration that performs power conversion from DC power to high-frequency AC power by ON / OFF operation of the switching element. And controlling the on / off operation of the switching element to control the output power.
PWM control for adjusting the on-pulse width of the control pulse signal output to the switching element, and PDM control for adjusting the on-pulse density of the control pulse signal by setting the on-pulse width of the control pulse signal to a predetermined width that allows the switching element to be sufficiently turned on. The power supply apparatus is characterized in that PWM control is performed on the higher output side than the predetermined output request and is switched to PDM control on the lower output side than the predetermined output request. Control method.

11 Power supply device for arc welding (power supply device, power supply device for arc machining)
13 Inverter circuit 20 Control circuit 20b Control switching unit S1-S4 Control pulse signal TD PDM control cycle TW PWM control cycle TR1-TR4 First to fourth switching elements Wm On-pulse width Wm0 Minimum width (predetermined width)
Wmx maximum width

Claims (3)

In the process of generating output power of the power supply device, an inverter circuit having a full bridge circuit configuration that performs power conversion from direct current power to high frequency alternating current power by an on / off operation of the switching element;
A control circuit that outputs a control pulse signal to the switching element to control the on / off operation of the switching element and controls the output power, and is configured to generate DC output power for arc machining A device,
The inverter circuit includes a first switching element to the first upper arm, a third scan Lee switching element to the first lower arm, the second switching element to the second upper arm, the fourth switching element is in the second lower arm The first and fourth switching elements are arranged as a set, the second and third switching elements are set as a set, and each set alternately performs a switching operation to convert DC power into high-frequency AC power. And
The control circuit includes a PWM control for adjusting an on-pulse width of a control pulse signal output to the switching element, and an on-pulse density of the control pulse signal by setting the on-pulse width of the control pulse signal to a predetermined width that allows the switching element to be sufficiently turned on. PDM control to adjust the
In the control of the control circuit, a control switching unit that performs the PWM control on a higher output side than a predetermined output request and switches to the PDM control on a lower output side than the predetermined output request,
In the PDM control, a constant period of the PWM control period is set as a PDM control period, and any on-pulses in the PDM control period are thinned out to adjust the density of the on-pulses. A power supply apparatus for arc machining, wherein the control pulse signal output to the element and the fourth switching element and the control pulse signal output to the second switching element and the third switching element are similarly thinned out. In the arc machining power supply device according to claim 1,
The control switching unit causes the PWM control to be performed from a maximum width of the on-pulse width of the control pulse signal to a minimum width at which the switching element can be sufficiently turned on. Switching to the PDM control that adjusts the density of the on-pulse while fixing at a minimum width, an arc machining power supply device, In the power supply device for arc machining according to claim 1 or 2 ,
The PDM control, arc machining power supply apparatus characterized by adjusting the density of the on-pulse thinning out on pulse from the rear end side of the PDM control cycle in order.