JPH01295672A - Flyback converter - Google Patents

Abstract

PURPOSE:To provide a large capacity to a flyback converter by using a plurality of transformers in which each single winding is connected in parallel through each diode. CONSTITUTION:A flyback converter is composed of a transformer 1, a DC power source 2, a switching transistor(Tr) 3, a controlling circuit 4, a rectification diode 5 and smoothing capacitors 5a-5b. In this connection, transformers 1a-1b each connected in parallel through diodes 6a-6b and 7a-7b on both primary and secondary sides are used to provide a far increased output to the converter. If the transformers 1a and 1b are of the same performance, the output thus obtained will be up to twice as large as what a conventional converter can provide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flyback type DC/DC converter, and particularly to a flyback converter for a device that uses high output power.

[Prior Art] Conventionally, a flyback type DC/DC converter uses one switching control circuit and a switching transistor to apply a chopped voltage to one transformer, store energy, and transfer it to the secondary side. and generates the necessary voltage.

Figure 4 is a circuit diagram showing a conventional flyback converter in blocks, and 1 in the figure is a transformer.

2 is a DC power supply, and 3 is a switching transistor.

4 is a control circuit, 5 is a rectifying diode, and 6 is a smoothing capacitor.

[Problems to be Solved by the Invention] When increasing the output of a conventional flyback converter, it is necessary to reduce the primary inductance of the transformer 1. That is, the final current flowing through the primary inductance and the voltage V9 winding is 1. Let T be the time that the current flows and E be the energy.There is the following relationship, so when V and T are constant, if L becomes small, E becomes large.

Even if the primary inductance 1- is reduced, the associated leakage inductance does not decrease much, so
There is a problem in that the energy that cannot be transmitted to the secondary side increases and the efficiency of the flyback converter decreases.

In addition, in recent years there has been a growing demand for flat power supply installations and for incorporating power supplies into narrow spaces, and conventionally, transformers were large, so there were often restrictions on the shape of the transformer.

The purpose of the present invention is to connect multiple small transformers in parallel,
An object of the present invention is to provide a flyback converter capable of producing louder sound.

[Means for Solving Problem 11] In order to solve the above problems, the present invention includes a DC power supply and a transformer whose primary winding is connected to the DC power supply via a switching transistor and its control circuit. 1, characterized in that the transformer is comprised of a plurality of transformers in which at least one winding is connected in parallel via a diode.
'It is a back converter.

Moreover, a feedback winding is added to the transformer having the largest primary side:secondary side turns ratio among the plurality of transformers connected in parallel.

[Example] Embodiments of the present invention will be described below based on the drawings.

(Example 1) FIG. 1 is a circuit diagram showing the basic configuration of the present invention.

The same parts in the figure as in FIG. 4 are given the same reference numerals.

The present invention aims at increasing output by using transformers connected in parallel through diodes on both the primary and secondary sides.

Here, if the transformers 1a and 1b are equivalent, it is possible to obtain up to twice the output.

The backflow prevention diodes 7a and 7b are used during the period when the energy stored in the transformer is generated on the secondary side.

A voltage higher than the DC voltage 1T12 is generated at the drain of the switching transistor 3, but if there is a slight difference between the transformers 1a and 1b, the generated voltage will be fixed at the lower one, so this is necessary to prevent this. In addition, 5a and 5b in the figure are rectifier diodes.

Although this example deals with the case where there are two transformers, the same applies to three or more transformers, and although the case where there is one main switching transistor is illustrated, as shown in Fig. 2, two transformers are used. It is also possible to drive the devices 1a and lb with one or more switching transistors, for example 3a and 3b, respectively.
In that case, diodes 7a and 7b are not necessary.

(Embodiment 2) Embodiment 1 was a passive flyback converter in which the control circuit spontaneously drives the switching transistor 3, but this system is not very practical because the drive circuit is expensive. For this reason, this embodiment uses a self-excited seven-liveback converter.

The circuit diagram in FIG. 3 shows an example in which the present invention is applied to a self-excited flyback converter.

In the figure, the same parts as No. 4 are given the same reference numerals.

The transformer was constructed so that the ratio of the number of turns on the primary and secondary sides of the transformer 1b was larger than that of the transformer 1a.

That is, the number of primary windings of transformers 1a and 1b is np, respectively.
a, npb, and the number of secondary windings are nsa and npb, respectively.
If sb, then n sa/ n pa< n sb/
n pb.

Here, if the inductance of the primary winding of the transformer is equal, the period during which the switching transistor 3 is conductive,
The same energy is stored in transformers 1a and 1b. When the switching transistor 3 is cut off, energy is released from the secondary winding, but at this time n sa/n
If pa<n sb/n pb, the time required to release the energy stored in transformer 1b is long, and it is ensured that transformer 1a1. : After the accumulated energy is transmitted to the secondary side, the switching transistor 3 becomes conductive due to the voltage induced in the feedback winding number nG.

If the feedback winding is connected to the larger transformer 1b, self-oscillation will be achieved successfully. If this is reversed, the transformer will become saturated and lead to destruction of the main switch.

Of course, in this case as well, as described in the first embodiment, there is no limit to the parallel connection of two or more transformers or the number of switching transistors.

[Effects of the Invention] As detailed above, the flyback converter according to the present invention applies chopped voltage waveforms to multiple transformers at the same time using one switching control circuit, and increases the high-output DC output. It has become possible to obtain efficiency.

Furthermore, since it became possible to connect multiple small transformers, it became possible to create a power supply that could be placed in a narrow space without worrying about the size of the transformer.

Furthermore, since the present invention can be applied to a self-excited flyback converter, it is also advantageous in terms of cost.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram in which two transformers 1a and lb are driven by two switching transistors 3a and 3b, respectively, and Fig. 3 is a circuit diagram of the present invention. FIG. 4 is a circuit diagram showing a self-help type flyback converter which is another embodiment of the invention, and FIG. 4 is a circuit diagram showing a conventional example. 1, la, lb... transformer, 2... DC power supply, 3.
3a, 3b... switching transistor, 4...
Control circuit, 5a, 5b...P diode, 6...
・Smoothing capacitors, 7a, 7b... Backflow prevention diodes, npa, npb-...1 of transformers 1a, 1b
Number of windings on the next side, nsa, n5b--Transformer 61a, 1b
The number of secondary windings, nG...Number of feedback windings. Part 1 Figure 3

Claims (2)

[Claims] (1) It has a DC power supply and a transformer whose primary winding is connected to the DC power supply through a switching transistor and its control circuit, and at least one winding of the transformer is connected to the DC power supply through a diode. A flyback converter is characterized by consisting of multiple transformers connected in parallel. (2) Claim (1) characterized in that a feedback winding is added to the transformer having the largest primary:secondary winding ratio among the plurality of transformers connected in parallel. Flyback converter as described.