JP2008099381A - Power supply unit for arc welding, and the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the unbalanced voltage sharing of two pieces of smoothing capacitors, connected in series at the input side of inverters in a power supply unit for arc welding, and the like, constituted of the inverters. <P>SOLUTION: This power supply unit comprises two inverter units, which input DC voltages between the positive and negative poles of each of two capacitors, connected in series for smoothing the output of an input rectifier to output an alternating current and supply electric power in parallel to a load. This power supply unit incorporates a revised PWM drive signal generation means, which comprises a circuit that detects voltages across terminals of each smoothing capacitor and detects a differential voltage from a reference signal, a circuit that corrects pulse timing so that it is made narrow on time base, when the voltages across the terminals of the capacitors are low, and a corrected PWM drive signal generation circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a small and light power source for arc welding or plating with an inverter configuration that can be used with either a two-voltage AC power source having a high voltage (440V) at the power receiving end and a low voltage (220V) that is about half that voltage. It relates to the improvement of the device.

  2. Description of the Related Art Conventionally, this type of two-input-voltage arc welder is operated by an input rectifier that rectifies an AC power receiving power source, a smoothing capacitor, and a direct current as described in "Patent Document 1" shown in FIG. An inverter having a semiconductor switch configuration for outputting high-frequency alternating current, an output transformer to which the output of the inverter is supplied, and an output terminal of the input rectifier by the high voltage and the low voltage corresponding to the high voltage and low voltage of the AC power supply A connection switching device is provided between which a smoothing capacitor is switched in series and in parallel.

  When the AC received voltage is on the high voltage side, a smoothing capacitor is connected in series between the output terminals of the input rectifier, and the voltage between the positive and negative electrodes of each capacitor is divided into voltages for each capacitor, and the voltage is equally shared. It has become a state. However, when the inverter load is unbalanced and the conduction width of the switching element is not balanced, the shared voltage of each smoothing capacitor varies, and one of the smoothing capacitors has a high shared voltage, which significantly reduces the durability of the capacitor. Therefore, it is necessary to select a member that is one rank higher in the withstand voltage of the switching element.

  The paragraph (0027) of Patent Document 1 has the following description. When this is reprinted, “32 and 33 are two feedback rectifiers for the voltage balancer, and are composed of diode bridges of diodes 33 to 36 and 37 to 40. The output of the tertiary windings 27d and 26d is rectified and injected to the input side of the inverters 11 and 12. " Large current circuit members such as a feedback rectifier and an output transformer having a tertiary winding were provided. The design with the withstand voltage upgrade of each component as described above has been an impediment to providing a power supply device at low cost.

Japanese Patent Application Laid-Open No. 05-111766

  The present invention switches the internal connection in response to the high voltage and low voltage of an AC power supply, and is applicable to a three-phase power supply. A compact and lightweight two-input voltage compatible inverter configuration for arc welding, electroplating power supply, etc. This is a power supply for the application of (in the case of internal connection corresponding to high voltage), and the output of each inverter and the conduction width of the switching element of each inverter become uneven. There is a problem that the voltage between the positive electrode and the negative electrode becomes unbalanced.

  Further, since an uneven DC voltage is applied to the inverter input side, a high breakdown voltage power transistor is required as a switching element constituting the inverter. Since it is difficult to obtain a high switching power transistor having such a high withstand voltage, the inverter operating frequency cannot be increased, and the inverter output frequency is lowered by design. The design was reduced in size.

  In addition, a high breakdown voltage transistor has a higher collector / emitter saturation voltage (on voltage) than a low breakdown voltage and a large internal loss, so that a large-sized heat dissipation fin is required for the inverter. Therefore, there is a problem that the power supply device used for welding or plating is prevented from being reduced in size and weight.

  When a tertiary winding is provided in the output transformer, and this output is rectified by the feedback rectifier for the voltage balancer and injected into the input side of the other inverter, the output imbalance of the inverter is prevented, and the required element breakdown voltage of the inverter is reduced. Although it has been reported that the welding machine can be made smaller and lighter by lowering it, there was a drawback that the size and weight of the output transformer and the number of manufacturing steps increased.

  Since the purpose is to provide a small and inexpensive power supply device, it is not possible to adopt a solution that increases the number of man-hours for producing an output transformer and increases its size, so we decided to solve it using signal circuit technology.

Regarding claim 1,
Two input rectifiers that convert the AC power supply to DC, two series smoothing capacitors that divide this output voltage, and two semiconductor switch elements that operate with the voltage between the positive and negative electrodes of each smoothing capacitor to output high-frequency AC Corresponding to the inverter, the output transformer to which the output of each inverter is supplied, and whether the voltage of the AC power receiving power source is a high voltage or a low voltage that is about half of the high voltage. In a power supply apparatus provided with connection switching means for switching and connecting the smoothing capacitors in series and in parallel between the DC output terminals of the rectifier, when the smoothing capacitors are in series, the voltages between the positive and negative electrodes of the two capacitors A power supply device for arc welding or the like, characterized in that it is provided with capacitor voltage equalizing means for equalizing the voltage.

Regarding claim 2,
An input rectifier that converts the AC power supply to DC, a plurality of series smoothing capacitors that divide the output voltage of the input rectifier, and a plurality that outputs high-frequency alternating current by operating with the voltage between the positive and negative electrodes of each of the smoothing capacitors Inverter, the output transformer to which the output of each inverter is supplied, and the output terminal of the secondary winding of the output transformer are connected in parallel or cascaded as a load terminal, or connected to the output terminal of the secondary winding In a power supply device in which the output terminals connected to the output rectifier are connected in parallel or cascaded to form a load terminal, capacitor voltage equalizing means for equalizing the voltages between the positive and negative electrodes of a plurality of capacitors is provided. A power supply device such as arc welding, which is characterized by the above.

Regarding claim 3,
Capacitor voltage equalization means, wherein the capacitor voltage equalization means comprises voltage detection means for detecting the voltage between terminals of each capacitor, and modified PWM drive signal generation means for supplying an output signal to the switching element of the inverter. 3. A power supply device for arc welding or the like according to claim 1 or 2.

Regarding claim 4,
The modified PWM drive signal generation means inputs the output signal of the voltage detection means for detecting the voltage between the positive electrode and the negative electrode of each capacitor, detects a difference voltage from the reference signal, a pulse timing correction circuit, a correction PWM drive signal circuit 4. A power supply apparatus for arc welding or the like according to claim 3, which is a modified PWM drive signal generating means for supplying to the control pole of the switching element of the inverter.

Regarding claim 5,
5. The arc timing correction circuit according to claim 4, wherein the pulse timing correction circuit is a pulse timing correction circuit corresponding to the output signal of the differential voltage detection circuit, generating a correction PWM pulse corrected in time axis and supplying the corrected PWM pulse to the drive signal circuit. The power supply unit was used.
As described above, a constant direct current corresponding to a relatively low voltage is generated between the positive and negative electrodes of both smoothing capacitors, and the voltage applied to the input side of both inverters is high. Even when a voltage AC power supply is supplied, the voltage is maintained at a relatively low voltage, which is the same as that when a low voltage AC power supply is supplied. Both inverters may have a low switching element withstand voltage, and the switching frequency can be increased. Therefore, the supplied AC power supply can reduce the size and weight of the high-frequency output transformer, and can be used not only with a single-phase power supply but also with a three-phase power supply. A power supply can be realized.

  The smoothing capacitors connected in series share the voltage evenly, eliminating the need to select with a margin for the withstand voltage. A high withstand voltage power transistor is not required as a switching element, and a power transistor with a high withstand voltage can be easily obtained, so that the output frequency of the inverter can be increased by design and the output transformer can be downsized. By suppressing the unbalance of the input voltage of the inverter, the required switching element withstand voltage can be selected to be lower, and a power supply device for welding or the like could be manufactured at a lower cost.

  A first embodiment of the present invention will be described with reference to FIG. The configuration of the apparatus related to the present invention will be described with reference to FIG. 3 for partially explaining the first embodiment. 1 shows an overall configuration when an AC power source is a three-phase power source. In FIG. 1, 1a to 1c are power receiving three-phase power terminals, 2 is an input rectifier, and has a positive output terminal 2p and a negative output terminal 2n. Reference numeral 3 denotes a first smoothing capacitor, the positive electrode of which is connected to the output terminal 2p. Reference numeral 4 denotes a second smoothing capacitor, the negative electrode of which is connected to the output terminal 2n.

  The connection switching means 9 connects the first smoothing capacitor 3 and the second smoothing capacitor 4 in series between the DC output terminals 2p and 2n of the input rectifier 2, and divides and applies the DC output voltage to each capacitor by 50%. As shown in FIG. 3, the switching between the direct / parallel connection is switched between the case where the smoothing capacitors 3 and 4 are connected in parallel and the output voltage of the input rectifier 2 is applied to each capacitor by 100%. Connection switching means.

  The inverters 11 and 12 are inverters having a bridge configuration of semiconductor switch elements that operate by inputting DC voltages between the positive and negative electrodes of the smoothing capacitors 3 and 4. An IGBT or a power MOS transistor is used as the semiconductor switch element, and a diode is connected in antiparallel to each switch element.

  The modified PWM drive signal generation means 50 receives the output signal of the voltage detection means 55 for detecting the voltage between the terminals of each capacitor, receives the signal of the difference voltage detection circuit 52 for detecting the difference voltage from the reference signal, and receives the pulse timing. This is a means for generating a corrected PWM drive signal that is supplied to the control pole of the switching element of the inverter by supplying the output of the correction means to the correction PWM drive signal circuit 54. These operations are described below.

  In the operation explanatory diagram of FIG. 2, the horizontal axis represents time, and the vertical axis represents a signal waveform indicating amplitude. A indicates the magnitude relationship between a PWM carrier wave (triangular wave) W and signal waves S1 and S2 that modulate the carrier wave (triangular wave) W. B is a pulse waveform of a drive signal inputted to the gate (control pole) of a switching element such as an IGBT constituting the inverters 11 and 12 (assuming that the voltage of the smoothing capacitor is ignored). The output pulse when the technique of the present invention is not implemented. For example, the signal wave S1 is a signal wave generated as a target current value when the inverter output current is controlled to be constant. Only when the carrier wave (in this case, a triangular wave) W has a higher wave height than the signal wave S1, the pulse waveform is output at the H level (like a hatched pulse), and the pulse waveform is at the L level during the time period when W is lower than the signal wave S1. Is output. The switching element is turned on in response to the hatched pulse, and the inverter output current is output to the output transformer.

  C is a pulse waveform of the drive signal input to the gate of the inverter. The smoothing capacitor is detected by the pulse timing correction circuit 53 in the embodiment of the present invention by detecting the voltage of the smoothing capacitor and amplifying the difference voltage from the reference value. When the detection voltage is high, the output signal is generated as S2 having a low peak value, and when the detection voltage of the smoothing capacitor is low, the output signal is generated as S2 having a high peak value.

  In this way, the modulation signal wave S2 is generated, input to the correction PWM drive signal circuit 54, and the output signal pulse waveform when the carrier wave (in this case, the triangular wave) W is modulated is the pulse waveform indicated by the oblique line C. This corresponds to the output waveform of the correction PWM drive signal circuit 54 in FIG. 1 and has a narrow pulse width when S2 is high (when the smoothing capacitor voltage is low).

  Which voltage of the smoothing capacitors 3 and 4 is lower in the output signal of the difference voltage detection circuit 52 that detects the voltage of the smoothing capacitors 3 and 4 and detects the difference voltage from the reference signal that is the output of the reference signal generation circuit 51 As a result, the width of the C pulse waveform is reduced. When the width of the C pulse waveform is small, the inverter output becomes small and the load is lightly loaded, and the width of the C pulse waveform is large (or small) depending on which voltage of the smoothing capacitors 3 and 4 is high (or low). The load is increased (or decreased), and the capacitor terminal voltage decreases (or increases). In this way, the difference in the shared voltage between the smoothing capacitors 3 and 4 can be compensated. The invention focuses on sharing the low (or high) shared voltage of the smoothing capacitors connected in series depending on whether the load is heavy (or light).

  The transformers 26 and 27 are high-frequency transformers provided as output transformers for each inverter, and the primary windings 26a and 27a connected to the inverters 11 and 12 and the output secondary windings 26b and 27b are individually magnetic cores. It is formed by winding around. The secondary windings 26b and 27b of the transformers 26 and 27 are connected in parallel and a rectifying diode is connected to supply a direct current to the load. When the rectifying diode is not connected, an AC arc is connected. There are cases where power is supplied to the load. There are cases where the secondary windings 26b and 27b are connected in parallel and a rectifying diode is connected to supply a direct current to the load, or an AC arc load is supplied without being connected to the rectifying diode. A parallel / series connection means 56 is connected to the secondary windings 26b and 27b.

  In the block diagram of the second embodiment according to the present invention shown in FIG. 4, INV is an inverter unit having a smoothing capacitor Cn on the input side and having a transformer at the output end. The voltage detection means 55 and 50 are the corrected PWM drive signal generating means between the positive and negative electrodes of each smoothing capacitor Cn. The inverter output is controlled by amplifying the difference from each reference voltage to generate a signal wave S2 that modulates the carrier wave (triangular wave) W, and the shared voltage of each smoothing capacitor Cn is equalized. In this way, the plurality of smoothing capacitors connected in series can suppress the variation in the voltage between the terminals, thereby forming an inverter that applies the input voltage at a voltage lower than the received AC voltage.

  A high-withstand-voltage power transistor is not required as a switching element that constitutes the inverter, and power transistors that do not have a high withstand voltage can easily be obtained with a high switching frequency, so that the operating frequency of the inverter can be increased, and the inverter output transformer is compact.・ We were able to reduce the weight and make it possible to manufacture with materials that saved power supply devices for welding, etc., which contributed to energy and resource savings.

It is a connection diagram of a 1st embodiment by the present invention. It is operation | movement explanatory drawing of embodiment by this invention. It is a connection diagram of an apparatus for explanation related to the present invention. It is a block diagram of 2nd Embodiment by this invention. It is a connection diagram of the power supply apparatus for arc welding of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC receiving terminal 2 Input rectifier 2p Positive electrode output terminal 2n Negative electrode output terminal 3 1st smoothing capacitor 4 2nd smoothing capacitor 9 Connection switching means 11, 12 Inverter 26, 27 Output transformer 26a, 27a Primary winding 26b, 27b Secondary windings 26d, 27d Tertiary winding 42 Connection switching devices 48, 49 Output terminal 50 Modified PWM drive signal generation means 51 Reference signal generation circuit 52 Difference voltage detection circuit 53 Pulse timing correction circuit 54 Correction PWM drive signal circuit 55 Voltage Detection means Cn nth smoothing capacitor INV inverter unit

Claims (5)

  An input rectifier that receives alternating current and converts it to direct current, two series smoothing capacitors that divide the output voltage of the input rectifier, and two that output high-frequency alternating current connected between the terminals of each of the smoothing capacitors. And a connection switching means for switching and connecting each of the smoothing capacitors between the DC output terminal of the input rectifier between the series and the parallel. A power supply apparatus for arc welding or the like, characterized in that it comprises capacitor voltage equalizing means for equalizing the voltage between the terminals of the two capacitors.   An input rectifier that receives alternating current and converts it to direct current; a plurality of series smoothing capacitors that divide the output voltage of the input rectifier; and a plurality of inverters that output high-frequency alternating current by inputting voltages between terminals of the smoothing capacitors; The output transformer to which the output of the inverter is supplied and the output terminal of the secondary winding of each output transformer are connected in parallel or cascaded as a load terminal, or the output rectifier is connected to the output terminal of the secondary winding In the power supply device in which the output terminals of the output rectifier are connected in parallel or cascaded to form load terminals, capacitor voltage equalizing means is formed to equalize the voltages between the terminals of the plurality of capacitors. A power supply apparatus for arc welding or the like characterized by comprising.   The capacitor voltage equalizing means is a capacitor voltage equalizing means comprising voltage detecting means for detecting a voltage between terminals of each capacitor, and modified PWM drive signal generating means for supplying an output signal to the switching element of the inverter. A power supply apparatus for arc welding or the like according to claim 1 or 2.   The modified PWM drive signal generation means includes an output signal of voltage detection means for detecting a voltage between terminals of each capacitor, a difference voltage detection circuit from a reference signal, a pulse timing correction circuit, a correction PWM drive signal circuit, and an inverter 4. A power supply apparatus for arc welding or the like according to claim 3, which is a modified PWM drive signal generating means for supplying to the control pole of the switching element.   The pulse timing correction circuit includes a triangular wave signal generation circuit (or a sawtooth wave signal generation circuit), and generates a corrected PWM pulse in which the pulse timing is corrected on the time axis corresponding to the output signal of the differential voltage detection circuit. The power supply apparatus for arc welding or the like according to claim 4, which is a pulse timing correction circuit supplied to the drive signal circuit.

Images