JPH0360370A - Power supply circuit - Google Patents

Abstract

PURPOSE:To prevent generation of heat due to current imbalance, by connecting primary windings of respective transformers in series and rectifying and flywheel diodes to secondary windings in parallel. CONSTITUTION:A primary winding of each transformer T1, T2 is connected in series. Simultaneously with this connection, by parallelly connecting rectifier circuits in which rectifying diodes D1, D3 and flywheel diodes D2, D4 are respectively connected to a secondary winding of each transformer T1, T2, an output is obtained. Since the primary winding of each transformer T1, T2 is connected in series, an equal primary current is generated in each transformer T1, T2. While by equally setting winding ratio of the transformers T1, T2, a secondary current is equally generated in each transformer T1, T2. Accordingly, deterioration of reliability with imbalance generated in the heat generation because of a large current in either of the transformers T1, T2 in parallel operation can be prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding a power supply circuit that prevents current imbalance in each transformer in a power supply circuit in which a plurality of transformers are operated in parallel, current imbalance in the transformers running in parallel may cause current to flow to one of the transformers. A power supply circuit that operates multiple transformers of the same capacity and the same turns ratio in parallel, with the aim of providing a power supply circuit that prevents heat generation in the transformer from concentrating and thereby prevents a decrease in reliability. The transformer is constructed by connecting rectifier circuits connecting the rectifier diodes and flywheel diodes of each transformer in parallel to obtain an output.

[Industrial application field]

The present invention relates to a power supply circuit configured to operate a plurality of transformers in parallel, and which prevents current imbalance among the transformers.

In a power supply circuit such as a switching regulator, the output capacity is large, so if the required capacity of the transformer exceeds the allowable capacity, it is necessary to use a plurality of transformers and operate them in parallel.

In such a power supply circuit in which a plurality of transformers are operated in parallel, it is desired that the currents of each transformer be balanced and that the heat generation of each transformer be not unbalanced.

[Conventional technology]

FIG. 4 shows the configuration of a conventional power supply circuit,
A case of a switching regulator circuit in which two transformers T1 and T2 are operated in parallel is illustrated.

Two transformers T1. T2 has the same capacitance and the same turns ratio nI+nz, and their primary sides are connected in parallel and connected to the DC power supply VIN via the switching transistor TRI, and their secondary sides are also connected in parallel, and the output is Rectifier diode D1. It is connected to the load RL via a rectifier circuit consisting of a flywheel diode D2, a smoothing circuit consisting of an output choke coil L1, and an output smoothing capacitor C2.

In the circuit of FIG. 4, the switching transistor T
RI is turned on and off in response to an external drive signal applied to the base, and is connected to the transformer T1.RI from the power supply VIN. A primary current of 11+il° is applied to the primary side of each T2. As a result, secondary currents i2. yield i,'.

Current iZ+1! is added, rectified through a diode D1, converted to direct current through a smoothing circuit consisting of a coil L1 and a capacitor C2, and supplied to the load RL. Note that the capacitor CI is a smoothing capacitor on the primary side of the transformer TLT2, and the diode D2 is a so-called flywheel diode that releases the energy of the coil L1 and generates an output current when the output of the diode D1 is turned off.

[Problem to be solved by the invention]

In the conventional power supply circuit shown in Fig. 4, the primary current flowing through each transformer T1 and T2 is determined based on differences in wiring for transformers (T1, T2) operated in parallel, or differences in impedance of the transformers themselves. 11+fl are not equal.On the other hand, the current on the secondary side of the transformer is n, from the turns ratio.

1 □ = □1 2 Old.

12 = 1 2 , therefore 12≠i, l, and the current of the transformer TLT2 is not balanced in both the primary and secondary.

As a result, the transformer, through which a large amount of current flows, generates heat.

In addition, on the secondary side, due to the difference in electromotive force between the windings of both transformers, a circulating current is flowing from the winding with higher electromotive force to the winding with lower electromotive force, which also generates heat in the transformer. It causes There is a problem in that heat generation in the transformer not only causes failure but also reduces reliability.

The present invention aims to solve the problems of the prior art, and is designed to prevent current from concentrating on one of the transformers due to current imbalance in transformers operating in parallel, thereby preventing heat generation in the transformers. The purpose of the present invention is to provide a power supply circuit that prevents a decrease in reliability.

[Means to solve the problem]

As shown in FIG. 1, the present invention relates to a power supply circuit that operates a plurality of transformers T1 and T2 having the same capacity and the same turns ratio in parallel.

At this time, the primary windings n of each transformer T1 and T2 are connected in series, and the secondary winding n2 of each transformer T1 and T2 is connected in series.
rectifier diodes D1, D3 and flywheel diodes D2., respectively. D4 is connected and the outputs of these rectifier circuits are connected in parallel to obtain an output.

[Effect]

Since the output capacity of the power supply circuit is large, if the required capacity of the transformer exceeds the allowable capacity, parallel operation is performed using multiple transformers.

In this way, in a power supply circuit in which multiple transformers of the same capacity and turns ratio are operated in parallel, if the primary windings are connected in parallel, current will concentrate in one of the transformers due to current imbalance in the transformers operating in parallel. do,
This causes the transformer to generate heat, reducing reliability.

Therefore, the primary windings of each transformer operating in parallel are connected in series, a rectifier circuit is connected to the secondary winding of each transformer, and the output sides of these rectifier circuits are connected in parallel to obtain an output.

In the power supply circuit of the present invention, the primary windings of a plurality of transformers are connected in series, so the primary current of each transformer is equal, and the turns ratio of each transformer is equal.
The secondary currents of each transformer will also be equal.

Therefore, it is possible to prevent reliability from decreasing due to unbalanced heat generation due to a large current value in one of the transformers operating in parallel.

〔Example〕

FIG. 2 shows the tank bottom of an embodiment of the present invention, and the same parts as in the circuit of FIG. 4 are designated by the same numbers. D3 is a rectifier diode, and D4 is a flywheel diode.

In the circuit of FIG. 2, the two transformers T1 and T2 have equal capacitances and equal turns ratios n, n, and the primary windings of each transformer T1.72 are connected in series. Further, the secondary windings of each transformer T1, T2 include a rectifier diode D1°D3 and a flywheel diode D2. A rectifier circuit consisting of D4 is connected. The output sides of both rectifier circuits are connected in parallel and connected to a load RL via a smoothing circuit consisting of an output choke coil L1 and an output smoothing capacitor C2.

In the circuit of Fig. 2, the switching transistor T
RI is turned on in response to an external drive signal applied to the base.
By turning off, the transformer T1,
A primary current iI is applied in series to each primary side of T2.

As a result, secondary currents ja+1z' are generated on the secondary sides of the transformers T1 and T2, respectively.

The secondary currents +z and i2゛ are each connected to the rectifier diode Di
and D3, and is rectified through coil L1. Capacitor C
It is converted into a direct current through a smoothing circuit consisting of 2, and is supplied to the load RL. Diode D2. D4 is a flywheel diode, and when the outputs of diodes Di and D3 are turned off, the energy of coil L1 is released to generate an output current to load RL.

In the circuit shown in FIG. 2, the primary windings of transformers T1 and T2 are connected in series, so the primary currents of both transformers are always equal. - On the proximal side of the crab, transformer T1,
The secondary currents 1 t+ 12゛ of T2 are n and , respectively.

iz = t 2 12' = □11 z and i, = i,'', so both transformers TLT
2, both primary and secondary currents are balanced.

FIG. 3 shows another embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same numbers, and L2 is an output choke coil.

In the circuit of FIG. 3, - compared to the circuit of FIG.
The choke coils that make up the smoothing circuit are connected to both transformers T1.
, T2 are respectively inserted into the output side of the rectifier circuit on the secondary side, and the output sides of both coils L1 and L2 are connected in parallel to the capacitor C2.

The operation of the circuit in Figure 3 is basically the same as the circuit in Figure 2, but the coils that make up the smoothing circuit are inserted separately into the outputs of the rectifier circuits of both transformers, so the coil current Restrictions based on capacity are relaxed, and output current can be increased.

Note that in each of the above embodiments, the number of transformers is not limited to two, and it goes without saying that the number of transformers can be similarly configured with two or more.

〔Effect of the invention〕

As explained above, according to the present invention, in a power supply circuit in which a plurality of transformers are operated in parallel, it is possible to balance the winding currents of each transformer operated in parallel.
It is possible to prevent current concentration in either transformer due to current imbalance, and prevent heat generation in the transformer. Therefore, according to the present invention, when transformers are operated in parallel to increase the capacity of the power supply, it is possible to prevent the reliability of the power supply circuit from decreasing due to the heat generated by the transformer.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIGS. 2 and 3 are diagrams each showing an embodiment of the present invention, and FIG. 4 is a diagram showing a conventional power supply circuit. T1 and T2 are transformers, D1 and D3 are rectifier diodes,
D2. D4 is a flywheel diode, LLL2 is an output choke coil, and C2 is an output smoothing capacitor.

Claims (2)

[Claims] (1) Multiple transformers with the same capacity and turns ratio (T1
, T2) are operated in parallel, the primary windings of each transformer (T1, T2) are connected in series, and the secondary winding of each transformer (T1, T2) is connected to a rectifier diode (D1, D3) ) and flywheel diodes (D2, D4) are connected in parallel to obtain an output. (2) Multiple transformers with the same capacity and turns ratio (T1
, T2) are operated in parallel, the primary windings of each transformer (T1, T2) are connected in series, and the secondary winding of each transformer (T1, T2) is connected to a rectifier diode (D1, D3) ) and flywheel diodes (D2, D4) are connected, and each rectifier circuit in which an output choke coil (L1, L2) is connected from the output end of each diode is connected in parallel to an output smoothing capacitor (C2). power supply circuit.