JP2002325449A - Transformer circuit and power inverter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a plurality of transformers in sure balance using a simple structure for supplying large power using a plurality of small transformers. SOLUTION: A transformer circuit 1 consists of two transformers T1, T2 each having separate core. In both of the transformers T1 and T2, primary windings 2, 3 are connected in parallel, and secondary windings 4, 5 are connected in series. One end of each of primary windings 2, 3 is connected with a DC power supply 6, and the other end thereof is connected with a switching device 7. An N-channel MOSFET used for the switching device 7 and a source is grounded. The respective secondary windings 4, 5 are connected wit ha smoothing circuit 8. The respective windings 2, 3, 4, 5 are formed, so that the primary and secondary polarities of the transforms T1, T2 become respectively the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer circuit and a power conversion circuit, and more particularly, to a transformer circuit and a power conversion circuit suitable for supplying large power using a plurality of small transformers.

[0002]

2. Description of the Related Art It is necessary to use a large core for a transformer of a high power supply. Transformers were sometimes connected in parallel to avoid using large cores.

Japanese Patent Application Laid-Open No. 6-120055 discloses a transformer used in a resistance welding machine as shown in FIG.
As shown in FIG. 1A, a transformer having a transformer circuit 32 in which three transformers 31a, 31b, 31c for supplying power to the secondary side are connected in parallel is disclosed. FIG. 9B
As shown in the figure, three transformers 31a, 31b, 31c
Are connected by conductor plates 33a and 33b, respectively, and a secondary load 34 is connected to both conductor plates 33a and 33b. In this case, the conductor plate 3
The width and thickness of each of the transformers 3a and 33b are fixed.
If the distances between the output terminals on the plus side and the minus side of a to 31c are equal, the output of the central transformer 31b is lower than the outputs of the transformers 31a and 31c on both sides.
As a result, there is a problem that the use efficiencies of the respective transformers 31a to 31c are different and stable power supply cannot be performed.

In order to solve the above problem, as shown in FIG. 9 (b), conductor plates 33a, 33b between predetermined transformers are set so that the impedance on the secondary side as viewed from each of the transformers 31a to 31c becomes equal. Have different cross-sectional areas.

In Japanese Utility Model Laid-Open Publication No. 2-36015,
One core 35 as a transformer used in the power supply circuit
Discloses a configuration in which a primary side winding and a secondary side winding are divided into a plurality of pieces and wound. Then, as shown in FIG. 10, two primary windings PL and PR are wound as primary windings and connected in parallel, and a secondary winding S1L corresponding to the primary winding PL as a secondary winding. , S2L are wound around secondary windings S1R, S2R corresponding to the primary winding PR, and are connected in series.

[0006]

There is a problem that the use of a large-sized core increases the cost and increases the layout restrictions in designing. Further, when the transformers are connected in parallel, if the respective secondary-side voltages of the transformers connected in parallel are different, only one of the transformers is operated and there is no point in connecting in parallel. Therefore, it is necessary to completely equalize the secondary voltages of the respective transformers connected in parallel, which is technically very difficult.

Further, Japanese Patent Application Laid-Open No. 6-120055 discloses
The purpose is to eliminate the imbalance due to the impedance of the wiring between multiple transformers connected in parallel,
It is assumed that the secondary voltages of a plurality of transformers connected in parallel are equal. No consideration is given to equalizing the secondary voltages of the plurality of transformers.

In the configuration disclosed in Japanese Utility Model Laid-Open Publication No. 2-36015, since the primary windings PL and PR share the core 35,
Even if the currents flowing through the secondary windings S1L (S2L) and S1R (S2R) are the same, the currents flowing through the primary winding PL and the primary winding PR are not necessarily equal. Therefore, the primary winding P
It is difficult to make the current flowing through L and the primary winding PR the same.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to supply a large amount of electric power by using a plurality of small-sized transformers, and to assure the plurality of transformers with a simple configuration. Another object of the present invention is to provide a transformer circuit that can be operated in a balanced manner. Another object of the present invention is to provide a power conversion circuit that can be reduced in size by using a transformer circuit that can reliably operate a plurality of transformers with a simple configuration in a balanced manner.

[0010]

According to a first aspect of the present invention, there is provided a transformer circuit including a plurality of transformers each having a separate core. The windings were connected in parallel, and the secondary windings were connected in series.

In the present invention, since the secondary sides of a plurality of transformers having separate cores are connected in series, the currents flowing through the respective secondary side windings are equal. For this reason, the current flowing to the primary side of each transformer is always equal, and each transformer is surely balanced. Also, for example, when two transformers are used, the number of turns of the secondary side winding may be １ ／ of the value determined from the number of turns of the primary side winding and the required output voltage. To contribute. Also, it is not necessary to make the primary side winding unnecessarily thick, which contributes to downsizing.

According to the invention described in claim 2, there is provided a transformer circuit having a plurality of transformers each having a separate core, wherein a primary winding of each transformer is connected in parallel, and a secondary side of each transformer is connected. Were connected in series via a rectifying element. In the present invention, since the secondary sides of the plurality of transformers are connected in series via the rectifying element, the currents flowing through the respective secondary side windings are equal. Therefore, the same operation and effect as those of the transformer according to the first aspect of the invention can be obtained.

In order to achieve the second object, in the invention according to claim 3, the transformer circuit according to claim 1 or 2 is used for a transformer circuit of a push-pull type power conversion circuit. Note that the power conversion circuit is not limited to a circuit in which the voltage changes between the input side and the output side, and is used for the purpose of ensuring insulation between the input side and the output side. Also includes those having the same voltage.

In the present invention, since the transformer circuit used is that of the first or second aspect of the present invention,
The push-pull type power conversion circuit can be downsized when supplying large power.

According to a fourth aspect of the present invention, in the transformer circuit of the forward power conversion circuit, the first or second aspect is provided.
Was used. In the present invention, since the transformer circuit used is the one according to the first or second aspect of the present invention, the size can be reduced even when a large power is supplied as a forward-type power conversion circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is embodied in a forward-type current conversion circuit (forward-type converter) will be described below with reference to FIG.

The transformer circuit 1 constituting the forward-type current conversion circuit includes transformers T1 and T2 each having a plurality (two in this embodiment) of separate cores. The primary windings 2 and 3 are connected in parallel to both transformers T1 and T2,
The secondary windings 4 and 5 are connected in series. One end of each of the primary windings 2 and 3 is connected to the DC power supply 6, and the other end is connected to the switching element 7. Switching element 7
, An N-channel MOSFET is used, and the source is grounded. Each of the secondary windings 4 and 5 is connected to a smoothing circuit 8. Each winding 2, 3, 4, 5 is connected to each transformer T
1 and T2 are formed such that the polarities on the primary side and the secondary side are the same.

The number of turns n1 of the winding 2 on the primary side of the transformer T1
And the number of turns n1 / N1 of the number of turns N1 of the secondary winding 4
Is set to be the same as the number of turns n2 / N2 of the number of turns n2 of the primary winding 3 and the number of turns N2 of the secondary winding 5 of the transformer T2. Further, in this embodiment, the number of turns n1 of the winding 4 is the same as the number of turns n1 of the winding 3 in the same manner as the number of turns n2 of the winding 3.
Is set to be the same as the number of turns N2 of the winding 5.

Next, the operation of the transformer circuit 1 configured as described above will be described. The switching element 7 is switched by a drive signal from a drive circuit (not shown). When the switching element 7 is turned on, a current flows through the transformer T
1 and T2 flow through the primary windings 2 and 3, and the induced electromotive force causes current to flow through the secondary windings 4 and 5.

Since the secondary sides of the plurality of transformers T1, T2 are connected in series, the windings 4, 5
Are equal. Therefore, each transformer T
The currents I11 and I12 flowing on the primary sides of the transformers T1 and T2 are always equal, and the transformers T1 and T2 are surely balanced.

If the voltage of the DC power supply 6 is V, the secondary voltage V1o of the transformer T1 and the secondary voltage V2o of the transformer T2 are V1o = V (N1 / n1) and V2o = V
(N2 / n2). The output voltage Vo of the transformer circuit 1 is the sum of the secondary voltages of the two transformers T1 and T2. Since the turns ratio of the two transformers T1 and T2 is the same, the output voltage Vo of the transformer circuit 1 is one transformer T1. In this case, the voltage is twice as high as that in Therefore, the number of turns of the secondary windings 4 and 5 of each of the transformers T1 and T2 is １ ／ of the value determined by the number of turns of the primary windings 2 and 3 and the required output voltage.

This embodiment has the following effects. (1) Primary windings 2 of a plurality of transformers T1, T2
3 were connected in parallel, and the secondary windings 4 and 5 were connected in series.
As a result, the windings 4, 5 on the secondary side of the transformers T1, T2
The current I2 flowing through each of the transformers T1 and T
The currents I11 and I12 flowing through the windings 2 and 3 on the primary side always become equal, and the transformers T1 and T2 operate in a surely balanced state.

(2) The transformers T1 and T2 are surely balanced based on the fact that equal current flows through the secondary windings 4 and 5 of the plurality of transformers T1 and T2. Therefore, even if the impedance of the wiring connected to the secondary windings 4 and 5 of the transformers T1 and T2 is unbalanced, the transformers T1 and T2 are surely in a balanced state, and the manufacturing is simplified. .

(3) Since the secondary sides of the plurality of transformers T1 and T2 are connected in series, for example, when two transformers T1 and T2 having the same configuration are used, the windings 4 and 5 on the secondary side are used. The number of turns may be １ ／ of the value determined from the number of turns of the primary windings 2 and 3 and the required output voltage. Therefore, the lengths of the windings 4 and 5 are shortened and the resistance value is reduced, and the volume occupied by the windings 4 and 5 is also reduced, so that the size and loss of the transformer can be reduced. The current I
Since the current 11 and the current I12 are surely balanced, it is not necessary to make the primary windings 2 and 3 unnecessarily thick, which contributes to downsizing.

(4) Since the transformers T1 and T2 are formed in the same configuration, the number of types of parts can be reduced and assembly is simplified. (Second Embodiment) Next, a second embodiment will be described with reference to FIG. This embodiment is significantly different from the above embodiment in that a plurality of (two in this embodiment) outputs can be obtained from the secondary side. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The transformer circuit 1 has two sets of output units 9a,
9b is provided. The secondary windings 4a and 5a for one output unit 9a are connected in series, and the secondary windings 4b and 5b for the other output unit 9b are also connected in series. The windings 4a and 5a and the windings 4b and 5b are
a, 8b. Each winding 2, 3, 4a, 4
b, 5a and 5b are formed such that the primary and secondary polarities of the transformers T1 and T2 are the same.

The number of turns n of the winding 2 on the primary side of the transformer T1
1, the number of turns N1a and N1b of the secondary windings 4a and 4b, the number of turns n2 of the primary winding 3 of the transformer T2, and the number of secondary windings 5
The numbers of turns N2a and N2b of a and 5b are set so as to satisfy the following relationship.

N1: N1a = n2: N2a, n1: N1b = n2: N2b In this embodiment, when the switching element 7 is turned on, a current flows through the primary windings 2 and 3 of the transformers T1 and T2, The secondary winding 4a,
Current also flows through 5a, 4b and 5b. Since the windings 4a and 5a are connected in series, a current I2a equal to the windings 4a and 5a flows. Since the windings 4b and 5b are connected in series, a current I2b equal to the windings 4b and 5b flows. Flows. Therefore, the current I1 flowing on the primary side of each transformer T1, T2
Since 1 and I12 have the same value corresponding to the sum of the current I2a and the current I2b, they are always equal, and the transformers T1 and T2 are surely balanced.

This embodiment has the following effects in addition to having substantially the same effects as (1) to (4) of the above embodiment. (5) Since the transformer circuit 1 includes the plurality of output units 9a and 9b, a plurality of different outputs can be obtained from one DC power supply 6.

(Third Embodiment) Next, a third embodiment embodied in a push-pull type power conversion circuit will be described with reference to FIGS.

In a push-pull converter 10 as a push-pull power conversion circuit, primary windings 2a and 3a of transformers T1 and T2 are connected in parallel between a DC power supply 6 and a first switching element S1, The primary windings 2b and 3b of the transformers T1 and T2 are connected in parallel between the DC power supply 6 and the second switching element S2. Winding 2
The number of turns of each of the windings 3a, 2a is set to n1.
The number of turns of 3b is set to n2. For example, MOSFETs are used for the switching elements S1 and S2.

Secondary windings 4, 5 of transformers T1, T2
Are connected in series. The winding numbers of the windings 4 and 5 are set to N1 and N2, respectively. Each winding 2a, 2b, 3
a, 3b, 4 and 5 are formed such that the primary and secondary polarities of the transformers T1 and T2 are the same.

In this device, the first and second switching elements S1 and S2 alternately turn on and off. First
When the switching element S1 is turned on, the transformer T
The currents I1a1, I1a2 are applied to the primary windings 2a, 3a of the primary winding T1, T2.
Flows, and the secondary winding 4,
Current also flows through 5. Since the windings 4 and 5 are connected in series, a current I21 equal to the windings 4 and 5 flows, and the currents I1a1 and I1a2 flowing to the primary sides of the transformers T1 and T2 always become equal. Will surely balance.

When the second switching element S2 is turned on while the first switching element S1 is turned off, the currents I1b1, I2 are supplied to the primary windings 2b, 3b of the transformers T1, T2.
1b2 flows, and the current I22 also flows through the secondary windings 4 and 5 due to the induced electromotive force. Since the windings 4 and 5 are connected in series, a current I22 equal to the windings 4 and 5 flows,
Currents I1b1, I1b flowing on the primary side of each transformer T1, T2
2 are always equal, and the transformers T1 and T2 are surely balanced.

When the second switching element S2 is on, the direction of the current flowing through the primary windings 2b and 3b of the transformers T1 and T2 is such that when the first switching element S1 is on, the windings 2a and 2b are turned on. The direction is opposite to the direction of the current flowing through 3a. As a result, the direction of the current I22 flowing through the secondary windings 4, 5 of the transformers T1, T2 is opposite to the current I21. Therefore, an AC output as shown in FIG. 4 is obtained by the switching operation of both switching elements S1 and S2. That is, this push-pull type converter 10 is DC-
Functions as an AC inverter. In this case, for example, it is used for driving a discharge tube or an EL element.

This embodiment has the following effects. (6) Since the push-pull converter 10 uses a transformer having the same configuration as that of the transformer circuit 1 of the first embodiment, it is possible to reduce the size and loss of the transformer when supplying large power. Therefore, the size and the loss of the push-pull converter 10 can be reduced.

(Fourth Embodiment) Next, a fourth embodiment embodied in a push-pull converter 10 having another configuration will be described with reference to FIG. This embodiment is significantly different from the above embodiments in that the secondary windings of the transformers T1 and T2 are connected in series via rectifying elements (diodes in this embodiment). The configuration of the primary side of each of the transformers T1 and T2 is the same as that of the third embodiment, and two sets of windings are provided on the secondary side, and a point that a DC voltage is output. Is greatly different from the third embodiment. The same parts as those in the third embodiment are denoted by the same reference numerals, and detailed description is omitted.

The secondary windings 4a, 5a corresponding to the primary windings 2a, 3a are provided on the secondary sides of the transformers T1, T2.
And secondary windings 4b, 5b are provided corresponding to the primary windings 2b, 3b. The number of turns of each of the windings 4a and 4b is set to N1, and the number of turns of each of the windings 5a and 5b is set to N2. Each winding 2a, 2b,
3a, 3b, 4a, 4b, 5a, 5b are each transformer T
1 and T2 are formed such that the polarities on the primary side and the secondary side are the same.

The windings 4a and 5a are connected in series.
a has one end connected to the positive output terminal 11 via the diode D1 and the other end connected to the winding 5 via the diode D2.
a is connected to one end. The other end of the winding 5a is connected to the output terminal 12 on the negative side. The windings 4b and 5b are connected in series. One end of the winding 4b is connected to the output terminal 11 on the plus side via a diode D3, and the other end is connected to one end of the winding 5b via a diode D4. . The other end of the winding 5b is connected to the output terminal 12 on the minus side.

In this device, the first and second switching elements S1 and S2 alternately turn on and off. First
When the switching element S1 is turned on, the transformer T
The currents I1a1, I1a2 are applied to the primary windings 2a, 3a of the primary winding T1, T2.
Flow, and the secondary winding 4
Current also flows through b and 5b. Since the windings 4b and 5b are connected in series, a current I21 equal to the windings 4b and 5b flows, and a current I1a flowing to the primary side of each of the transformers T1 and T2.
1, I1a2 are always equal, and the transformers T1, T2 are surely balanced. The current I21 is the negative output terminal 1
2, the current flows from the winding 5b, the diode D4, the winding 4b, and the diode D3 in this order to the output terminal 11 on the plus side.

When the second switching element S2 is turned on while the first switching element S1 is turned off, the currents I1b1, I2 are supplied to the primary windings 2b, 3b of the transformers T1, T2.
1b2 flows, and a current I22 also flows through the secondary windings 4a and 5a due to the induced electromotive force. Since the windings 4a and 5a are connected in series, a current I22 equal to the windings 4a and 5a flows, and the currents I1b1 and I1b2 flowing to the primary sides of the transformers T1 and T2 always become equal.
2 will definitely balance. The current I22 flows from the output terminal 12 on the minus side to the output terminal 11 on the plus side in the order of the winding 5a → the diode D2 → the winding 4a → the diode D1.

Therefore, in this embodiment, the switching elements S1 and S2 are alternately turned on and off, so that a DC voltage is output from the output section. (Fifth Embodiment) Next, a fifth embodiment will be described with reference to FIG. In this embodiment, each transformer T1, T2
Is another embodiment in which the secondary side winding is connected in series via a rectifying element (a diode in this embodiment). As in each of the embodiments, the primary winding of each transformer is connected in parallel. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Both ends of the winding 4 are connected to diodes D11, D12, D
13 and D14, the winding 5
Are connected to a full bridge 14 composed of diodes D21, D22, D23 and D24. One end of the full bridge 13 is connected to the output terminal 11 on the plus side, and the other end is connected to one end of the full bridge 14. Full bridge 1
The other end of 4 is connected to the output terminal 12 on the minus side. That is, the secondary windings 4, 5 of both transformers T1, T2
Are connected in series via a diode.

When the switching element 7 is turned on, the currents I11 and I12 are supplied to the primary windings 2 and 3 of the transformers T1 and T2.
Flows, and the secondary winding 4,
5, the current I2 also flows. Since the windings 4 and 5 are connected in series via the diodes, the current I2 equal to the windings 4 and 5 flows, and the currents I11 and I12 flowing to the primary sides of the transformers T1 and T2 always become equal. Transformers T1, T
2 will definitely balance. The current I2 is supplied from the negative output terminal 12 to the diode D22 → the winding 5 → the diode D23.
The current flows to the positive output terminal 11 in the order of: winding 4 → diode D12 → winding 4 → diode D13.

The embodiment is not limited to the above, and may be embodied as follows, for example. The number of transformers constituting the transformer circuit 1 is not limited to two, and as shown in FIG.
1, T2... TN), the primary windings 2, 3 and the like may be connected in parallel, and the secondary windings 4, 5 and the like may be connected in series. When the output voltage is the same, the larger the number of transformers, the smaller the number of turns of the secondary side windings 4, 5 and the like, and the size and loss can be improved.

The ratio n1 / N1 of the number of turns n1 of the primary winding 2 of the plurality of transformers T1 and T2 to the number of turns N1 of the secondary winding 4 is equal to the number of turns n2 of the primary winding 3 , The ratio n2 / N2 with the number of turns N2 of the secondary winding 5 may be different.

In the third embodiment, a bridge rectifier circuit (full-wave rectifier circuit) and a smoothing circuit may be connected to the secondary sides of the transformers T1 and T2. In this case, since the currents I21 and I22 flowing through the windings 4 and 5 are output through the bridge rectifier circuit and the smoothing circuit, the currents I21 and I22 correspond to the switching of the switching elements S1 and S2 as in the fourth embodiment. A DC voltage is output.

In the third embodiment, the switching timings of the two switching elements S1 and S2 are, as shown in FIG. 8, from the time when the first switching element S1 is turned off to the time when the second switching element S2 is turned on. A predetermined time may be provided from turning off the second switching element S2 to turning on the first switching element S1.

As in the fifth embodiment, a transformer circuit in which the windings on the secondary side of each transformer are connected in series via a diode is not limited to a forward-type power conversion circuit, but may be a push-pull type power conversion circuit. Alternatively, the present invention may be applied to a transformer configured to supply power directly to a transformer from an AC power supply.

A bipolar transistor or an IGBT may be used as the switching element 7, S1, S2 instead of the MOSFET. The present invention may be applied to a configuration in which an AC power supply is converted to DC by a converter and used without using a battery as the DC power supply 6.

The present invention is not limited to the configuration in which the power is supplied from the DC power supply 6 to the transformer by repeating the on / off operation of the switching element 7, and the configuration may be such that the power is supplied to the transformer directly from the AC power supply.

The transistor may be used as the rectifying element. The invention (technical idea) that can be grasped from the embodiment will be described below.

(1) In the invention described in claim 1 or 2, the plurality of transformers are formed in the same configuration. (2) In the invention described in claim 1 or claim 2,
The transformer has a plurality of output units.

[0054]

As described in detail above, according to the first and second aspects of the present invention, when a large amount of power is supplied using a plurality of small transformers, the plurality of transformers can be reliably formed with a simple configuration. Can be operated in a balanced manner. According to the third and fourth aspects of the present invention, it is possible to reduce the size of the power conversion circuit by using a transformer circuit that can reliably operate a plurality of transformers in a balanced manner with a simple configuration. Become.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a circuit diagram according to a second embodiment;

FIG. 3 is a circuit diagram of a third embodiment.

FIG. 4 is a timing chart showing the operation.

FIG. 5 is a circuit diagram of a fourth embodiment.

FIG. 6 is a circuit diagram of a fifth embodiment.

FIG. 7 is a circuit diagram of another embodiment.

FIG. 8 is a timing chart showing another example of on / off timing.

9A is a configuration diagram of a conventional technique, and FIG. 9B is a configuration diagram showing a connection structure of a transformer.

FIG. 10 is another prior art circuit diagram.

[Explanation of symbols]

1 ... Transformer circuit, 2,2a, 2b, 3,3a, 3b ...
Primary-side windings, 4, 5, 4a, 4b, 5a, 5b ... secondary-side windings, 10 ... push-pull converters as push-pull power conversion circuits, D11, D12, D13, D14,
D21, D22, D23, D24: Diodes as rectifying elements.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Omi 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture Inside Toyota Industries Corporation (72) Inventor Hironobu Furuya 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture Inside Toyoda Automatic Loom Works, Ltd. (72) Inventor Kimiyoshi Ozaki 2-1-1, Toyotamachi, Kariya-shi, Aichi Prefecture Inside Toyoda Automatic Loom Works, Ltd. F term in Toyota Industries Corporation (reference) 5H730 AA15 AS01 BB23 BB25 BB57 BB83 DD04 EE04 EE62 EE73 EE76 ZZ16

Claims (4)

[Claims] 1. A transformer circuit comprising a plurality of transformers having separate cores, wherein a primary winding of a transformer is connected in parallel and a secondary winding is connected in series. 2. A transformer circuit comprising a plurality of transformers each having a separate core, wherein a primary winding of each transformer is connected in parallel, and a secondary winding of each transformer is connected via a rectifying element. Transformer circuit connected in series. 3. A power conversion circuit using the transformer circuit according to claim 1 as a transformer circuit of a push-pull type power conversion circuit. 4. A power conversion circuit using the transformer circuit according to claim 1 as a transformer circuit of a forward-type power conversion circuit.