JPH11346475A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a switching element against damages, even if a pair of switching elements are closed simultaneously. SOLUTION: Capacitors 3a, 3b are connected in series between the output terminals of an input side rectifying circuit 2 and a series circuit 4a of an IGBT 5a, and a reactor 7a is connected in series with a series circuit 4b of an IGBT 5b and a reactor 7b between the capacitors 3a, 3b. A capacitor 8 forming a series circuit with the reactor 7a, when the IGBT 5a is closed and the IGBT 5b is opened and forming a series circuit with the reactor 7b, when the IGBT 5a is opened, and the IGBT 5b is closed is connected in series with a primary winding 9p of a transformer 9 between the joint of the series circuits 4a, 4b and the mutual joint of the capacitors 3a, 3b. Circulation diodes 6a, 6b are connected in parallel with the IGBTs 5a, 5b. The reactors 7a, 7b are coupled roughly and wound to generate flux in the same direction, when a current flow through the IGBT 5a and the circulation diode 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a power supply device,
In particular, it relates to a series resonance type.

[0002]

2. Description of the Related Art Power supplies, such as DC power supplies, are sometimes used for arc welding machines. In order to reduce the size and weight of the DC power supply for an arc welding machine, a DC power supply which converts DC directly into a high frequency and converts the high frequency into a DC is sometimes used. .

For example, an AC voltage from a commercial AC power supply is converted into a DC voltage in an input-side rectifier circuit, and the DC voltage is converted into a high-frequency voltage by an inverter. This high-frequency voltage is transformed by a transformer, converted into a DC voltage by an output-side rectifier circuit, and supplied to a welding load composed of a base material and a torch.

[0004] However, in a power supply device using such an inverter, a switching element constituting the inverter,
For example, switching loss in an IGBT or the like is large.
In addition, switching noise is often generated, and it is necessary to take sufficient measures against snubber. Therefore, for example, a series resonance type DC-DC converter as shown in FIG. 4 is being used as a DC power supply device for an arc welding machine.

That is, the input terminals 1a to 1c connected to the three-phase commercial AC power supply are connected to the input side rectifier circuit 2. A pair of capacitors 3a and 3b are connected in series between output terminals of the input side connection circuit 2. Between these capacitors 3a and 3b, a three-phase commercial AC voltage is rectified,
A smooth DC voltage is generated. The input side rectifier circuit 2 operates as a DC power supply.

[0006] First and second series circuits 4a and 4b are connected in series between the capacitors 3a and 3b. First
Is a first switching element, for example, an IGBT 5a connected in series with the first reactor 21a.
have. A circulating element such as a diode 6a is connected in anti-parallel to the collector-emitter conductive path of the IGBT 5a.

The second series circuit 4b has a second switching element, for example, an IGBT 5b connected in series with the second reactor 21b. A circulating element, for example, a diode 6b is connected in antiparallel to the collector-emitter conductive path of the IGBT 5b.

Complementary switching signals are supplied to the gates of the IGBTs 5a and 5b from a control circuit (not shown). That is, when the closing signal is supplied to the IGBT 5a, the opening signal is supplied to the IGBT 5b. Conversely, when the open signal is being supplied to the IGBT 5a, the closing signal is supplied to the IGBT 5b. This is repeated, IGB
T5a and T5b are high-frequency switched.

The first reactor 21a and the second reactor 21b are wound tightly around one core (not shown) in order to reduce the size and weight of the series resonance type DC-DC converter. . The positions indicated by black circles in FIG. 4 are the winding start positions of the first and second reactors 21a and 21b. First and second reactors 21a, 21
The capacitor 8 and the primary winding 9p of the output transformer 9 are connected in series between the interconnection point b and the interconnection point of the pair of capacitors 3a and 3b.

When the IGBT 5a is closed and the IGBT 5b is open, the capacitor 8 forms a series resonance circuit with the first reactor 21a. When the IGBT 5a is open and the IGBT 5b is closed, the capacitor 8 forms a series resonance circuit with the second reactor 21a. The resonance frequency of these series resonance circuits is IG
The switching frequency is set substantially equal to or slightly higher than the switching frequency of the BTs 5a and 5b.

The secondary winding 9s of the transformer 9 has an intermediate tap. The anodes of the diodes 10a and 10b forming the output side rectifier circuit 10 are connected to both ends thereof, the cathodes are connected to each other, the output terminal 11a is connected, and the intermediate tap is connected to the output terminal 11b. Have been. A welding load composed of, for example, a workpiece and a torch is connected between the output terminals 11a and 11b.

In this series resonance type DC-DC converter, a closing signal is supplied to the IGBT 5a and the IGBT 5b
When the open signal is supplied to the IGBT 5a, the charge of the smoothing capacitor 3a, the first reactor 21a,
Discharge occurs through the capacitor 8 and the primary winding 9p of the transformer 9. This discharge current ia flows as shown in FIG. First
When the discharge current ia decreases due to the resonance between the reactor 21a and the capacitor 8 and the polarity of the discharge current reverses,
From the smoothing capacitor 3a, the primary winding 9 of the output transformer 9
A current ia ′ flows as shown in FIG. 5 via p, the first reactor 21a, and the freewheeling diode 6a.

Next, when an open signal is supplied to the IGBT 5a and a closing signal is supplied to the IGBT 5b, the primary winding of the IGBT 5b, the second reactor 21b, the capacitor 8, and the transformer 9 is supplied from the smoothing capacitor 3b. At 9p, a discharge current ib flows as shown in FIG. When the discharge current ib decreases and the polarity is reversed due to the resonance between the second reactor 21b and the capacitor 8, when the polarity of the discharge current ib is reversed, the current flowing from the capacitor 3b to the reflux diode 6b, the second reactor 21b, the capacitor 8, and the transformer 9 A current ib 'flows through the next winding 9p as shown in FIG.

Thereafter, the above-described operation is repeated, a high-frequency current flows through the primary winding 9p of the transformer 9, and a high-frequency voltage is induced in the secondary winding 9s of the transformer 9, and this is the diode 1
The current is rectified by Oa and 10b and supplied to the welding load.

[0015]

In order to induce a high-frequency voltage as described above, it is necessary that the IGBTs 5a and 5b are switched alternately. By the way, when the current ib 'is flowing through the freewheeling diode 6b, the IG
When the closing signal is input to the BT 5a, the freewheeling diode 6
The current ib ′ flowing through b decreases as shown in FIG. 6 and finally becomes 0, and a reverse recovery current flows through the freewheeling diode 6b over a period T1. At this time, I
A short-circuit current flows in the reverse direction of the GBT 5a, the first reactor 21a, the second reactor 21b, and the freewheeling diode 6b. Since the first and second reactors 21a and 21b are tightly coupled in order to reduce the size of the power source for the welding machine, winding starts are provided at both ends a and b. Therefore, a short-circuit current flowing in the opposite direction between the IGBT 5a and the freewheeling diode 6b causes the first and second reactors 2
The inductances of 1a and 21b cancel each other,
A large short-circuit current may flow, and the IGBT 5a and the freewheeling diode 6b may be damaged.

An object of the present invention is to provide a power supply device in which a switching element or a free-wheeling diode is prevented from being damaged even when the switching element is closed during a reverse recovery time of the free-wheeling diode.

[0017]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a DC power supply, a pair of capacitors connected in series between output terminals of the DC power supply, A first series circuit of a first switching element and a first reactor, a first reflux element connected in parallel to the first switching element, and a second switching element that is opened and closed alternately with the first switching element. A second series circuit connected between the pair of capacitors in series with the first series circuit, and a second series circuit of the second switching element and the second reactor. A second circulating element connected to the first switching element is closed and the first switching element is opened when the second switching element is open.
The first switching element is open and the second switching element is closed, the capacitor forming a series circuit together with the second reactor, the primary circuit of the transformer A first and second reactor, comprising, in series with the winding, a capacitor connected between an interconnection point of the first and second series circuits and an interconnection point of the pair of capacitors; Are loosely coupled.

According to the first aspect of the present invention, since the first and second reactors are loosely coupled, the first switching element closes when a current flows through the second reflux element. Therefore, even if current flows simultaneously in the first and second reactors, the magnetic flux generated by the first reactor hardly affects the second reactor, and the magnetic flux generated by the second reactor is: Has little effect on the first reactor. Therefore, it is possible to prevent a large short-circuit current from flowing without reducing the inductance of the first and second reactors.

According to a second aspect of the present invention, as in the first aspect, a DC power supply, a pair of capacitors, first and second series circuits, first and second circulating elements are provided. , A capacitor, and the first in the first and second series circuits.
The second reactor and the second reactor are wound so as to generate a magnetic flux in the same direction when a current flows through them simultaneously.

According to the second aspect of the present invention, when a current is flowing through the second reflux element, the first switching element is closed, and a current flows simultaneously through the first and second reactors. However, since the magnetic fluxes generated by the first and second reactors are in the same direction, the inductance of the first and second reactors does not decrease and a large short-circuit current can be prevented from flowing.

According to a third aspect of the present invention, in the power supply device of the second aspect, the first and second reactors are loosely coupled.

According to the third aspect of the present invention, since the first and second reactors generate a magnetic flux in the same direction and are loosely coupled, a current flows through the second reflux element. In addition, even if a current flows through the first switching element, the inductances of the first and second reactors do not cancel each other, and a large short-circuit current can be prevented from flowing.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A DC power supply for arc welding according to one embodiment of the present invention is configured as shown in FIG. The same parts as those of the DC power supply device for arc welding shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. The power supply device of FIG. 1 is most different from the power supply device of FIG.
The first and second reactors 7a and 7b are used instead of the first and second reactors 21a and 21b.

The first and second reactors 7a and 7b are:
They are loosely coupled and wound so that when a current flows in the same direction at the same time, a magnetic flux is generated in the same direction. That is, the first reactor 7a has a winding start indicated by a black circle at the terminal a on the IGBT 5a side, the second reactor 7b has a winding start indicated by a black circle at the terminal c on the capacitor 8 side, and the winding end has an IGBT 5a side. Terminal b.

The first and second reactors 7a and 7b are:
It is wound around the core 12 as shown in FIG. The core 12 has outer legs 12a and 12b and a middle leg 12c. The outer legs 12a, 12b and the middle leg 12c are spaced apart from each other along the linear portion 12d and the linear portion 12d.
, And is formed integrally with the linear portion 12d. These outer legs 12a, 12b and middle leg 1
A linear portion 12f is arranged so as to connect the leading ends of 2c with a gap 12e.

The winding of the first reactor 7a is
A is roughly wound around terminal a. The winding of the second reactor 7b is coarsely wound around the outer leg 12b starting from the terminal c. The first and second reactors 7 are attached to outer legs 12a and 12b that are spaced apart.
a and 7b are wound and a gap 12e is provided, so that the first and second reactors 7a and 7b are wound.
b is loosely coupled. The end of the winding of the first reactor 7a and the beginning of the winding of the second reactor 7b are connected in series, and the connection point is connected to the terminal c.

A closing signal is supplied to the IGBT 5a,
When the open signal is supplied to the BT 5b, the charge of the smoothing capacitor 3a is changed to the IGBT 5a, the first reactor 7a, the capacitor 8, and the primary winding 9p of the output transformer 9.
To discharge through. The discharge current ia due to this discharge is shown in FIG.
As shown in FIG. As shown in FIG. 2, the magnetic flux φa generated by the discharge current ia
Since the reactors 7a and 7b are loosely coupled, they flow through the outer leg 12a and the middle leg 12c, and hardly flow through the outer leg 12b.

When the discharge current ia decreases due to the resonance of the first reactor 7a and the capacitor 8, and the polarity of the current is reversed, the primary winding 9p of the output transformer 9 from the capacitor 3a, the first reactor 7a, A current ia ′ flows through the diode 6a as shown in FIG.

Next, when an open signal is supplied to the IGBT 5a and a closing signal is supplied to the IGBT 5b, the primary winding 9p of the transformer 9 from the capacitor 3b, the capacitor 8, the second reactor 7b, and the IGBT 5b. Thus, the current ib flows as shown in FIG. This current ib causes the magnetic flux φ
b occurs. Since the first and second reactors 7a and 7b are loosely coupled, the magnetic flux φb flows through the outer leg 12b and the middle leg 12c as shown in FIG. 2, and hardly flows through the outer leg 12a.

When the discharge current ib increases due to the resonance of the second reactor 7b and the capacitor 8, and the polarity of the current is reversed, the diode 3b for circulation, the second reactor 7b, the capacitor 8, the output transformer, The current ib ′ flows through the primary winding 9p of FIG. 9 as shown in FIG.

By thus switching the IGBTs 5a and 5b alternately at a high frequency, a high-frequency current flows through the primary winding 9p of the transformer 9 and the secondary winding 9s of the transformer 9
, A high-frequency voltage is induced. This high-frequency voltage is rectified by the diodes 10a and 10b to supply a DC output to the welding load.

When the IGBT 5a is closed while the current ib 'is flowing through the freewheeling diode 6b, as described above, the IGBT 5a, the first reactor 7a, the second reactor 7b, and the freewheeling diode 6b are reversed. Short-circuit current ic flows. The magnetic flux φc flows through the outer legs 12a and 12b due to the short-circuit current ic. That is, since the first and second reactors 7a and 7b are loosely coupled, the short-circuit current ic
As a result, a magnetic flux similar to the magnetic flux φa and a magnetic flux similar to the magnetic flux φb are generated. However, these magnetic fluxes in the middle leg 12c are canceled because the directions are opposite and equal in magnitude. Therefore, a magnetic flux φc flowing through the outer legs 12a and 12b like the magnetic flux φc is generated.

As described above, the magnetic flux flowing through the outer legs 12a and 12b is in the same direction, and the first and second reactors 7a and 7b have the same direction.
The inductances of a and 7b are not canceled out, resulting in a large inductance. With this large inductance, the short-circuit current ic is suppressed, and the IGBT 5a and the freewheeling diode 6b are not damaged.

The IGBTs 5a and 5b are alternately opened.
Even when closing is repeated, when there is a difference between the current flowing through the IGBT 5a and the current flowing through the IGBT 5b, the back electromotive force induced in the reactor in which the large current flows increases, and the reactor in which the small current flows The back electromotive force induced by the above becomes small. As a result, the current having a large value is reduced to a small value, and the current having a small value is increased to a large value. That is, the IGBT 5a,
The current flowing through the first and second reactors 7a, 5b
7b.

FIG. 3 shows a DC power supply according to the second embodiment. The difference from the power supply device of FIG.
7b and the positions of the IGBTs 5a and 5b are interchanged. That is, from the capacitor 3a to the capacitor 8,
The first reactor 7a and the IGBT 5a are connected in this order, and the second reactor and the IGBT 5b are connected in this order from the capacitor 3b to the capacitor 8. Other configurations are the same as those of the power supply device of FIG. 1 and operate similarly.

Although the above two power supplies are power supplies for a DC arc welding machine, they can also be used as DC power supplies for other electric equipment. The output side rectifier circuit 10
May be provided with a DC-AC converter on the output side to output a low-frequency AC voltage.

In the above two power supplies, the gap 12e is formed between the outer legs 12a, 12b, the middle leg 12c of the core 12, and the linear portion 12f. However, in some cases, the outer legs 12a, 12b, The middle leg 12c and the linear portion 12f may be formed integrally. The first and second reactors 7a and 7b are wound so that a magnetic flux is generated in the same direction when a current flows at the same time. However, the first and second reactors 7a and 7b may be wound so that a magnetic flux is generated in the opposite direction. . However, in this case, it is necessary that both reactors are loosely coupled.

[0038]

As described above, according to the present invention, even if the switching element connected in series with the freewheeling diode is closed during the reverse recovery time when the current is flowing through the freewheeling diode, a large short-circuit current can be obtained. Can be prevented from flowing to prevent the switching element or the free-wheeling diode from being damaged.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC power supply device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of first and second reactors of the DC power supply device of FIG.

FIG. 3 is a circuit diagram of a DC power supply device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional DC power supply device.

FIG. 5 is a waveform diagram of a current flowing through the DC power supply device of FIG.

6 is a waveform diagram of a current flowing through a freewheeling diode of the DC power supply device of FIG.

[Explanation of symbols]

2 Input side rectifier circuit (DC power supply) 3a 3b A pair of capacitors 4a 4b First and second series circuits 5a 5b IGBT (first and second switching elements) 7a First reactor 7b Second reactor 8 Capacitor 9 Output transformer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Tetsuro Ikeda 2-14-3 Awaji, Higashiyodogawa-ku, Osaka-shi, Osaka Prefecture Sansan Electric Manufacturing Co., Ltd. (72) Takeshi Morimoto 2-chome, Awaji, Higashiyodogawa-ku, Osaka-shi, Osaka No. 14-3 Inside Sansha Electric Manufacturing Co., Ltd.

Claims (3)

[Claims] A first series circuit of a first switching element and a first reactor; a first series circuit of a first switching element and a first reactor; A first recirculation element connected in parallel to the switching element, a series circuit of a second switching element and a second reactor that are alternately opened and closed with the first switching element, the first series circuit A second series circuit connected in series between the pair of capacitors, a second reflux element connected in parallel to the second switching element, and a first switching element closed, When the second switching element is open, a series circuit is formed together with the first reactor, the first switching element is open,
A capacitor forming a series circuit together with the second reactor when the second switching element is closed, and in series with the primary winding of the transformer, an interconnection point of the first and second series circuits; And a capacitor connected between an interconnection point of the pair of capacitors, wherein the first and second reactors are loosely coupled. 2. A DC power supply; a pair of capacitors connected in series between output terminals of the DC power supply; a first series circuit of a first switching element and a first reactor; A first recirculation element connected in parallel to the switching element, a series circuit of a second switching element and a second reactor that are alternately opened and closed with the first switching element, the first series circuit A second series circuit connected in series between the pair of capacitors, a second reflux element connected in parallel to the second switching element, and a first switching element closed, When the second switching element is open, a series circuit is formed together with the first reactor, the first switching element is open,
A capacitor forming a series circuit together with the second reactor when the second switching element is closed, and in series with the primary winding of the transformer, an interconnection point of the first and second series circuits; And a capacitor connected between the interconnection points of the pair of capacitors, wherein the first and second reactors generate magnetic flux in the same direction when currents flow through them simultaneously. Power supply unit wound around. 3. The power supply according to claim 2, wherein:
And the second reactor is a loosely coupled power supply.