JPH05344723A - Resonant dc-dc converter - Google Patents

Abstract

PURPOSE:To reduce a required number of resonance inductances in a parallel drive system voltage resonant DC-DC converter. CONSTITUTION:A series circuit consisting of a primary winding of a transformer 2, third winding 23 and field effect transistor 5 is connected between terminals of a DC power supply 1. A resonance capacitor 7 is connected between main terminals of the field effect transistor 5. A series circuit consisting of a fourth winding 24 and field effect transistor 6 is connected to the end of the primary winding 21 of the transformer 2, and a second resonance capacitor 8 is connected between main terminals of the field effect transistor 6. The third winding 23 and fourth winding 24 lower coupling factor of the transformer 2 with a core to raise a leak inductance, and it is acted as a parallel drive system voltage resonant DC-DC converter by a series resonant circuit consisting of the leak inductance and resonance capacitors 7 and 8.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type DC-DC converter, and more particularly to a parallel drive type resonance DC-DC converter.

2. Description of the Related Art A resonance type DC-DC converter is suitable for high frequency because of its small switching loss and low noise, and it has been attracting attention as a circuit system effective for reducing the size and weight of a power supply. A method of controlling the switching frequency is generally used for voltage adjustment of this resonant converter, but in this method, it is necessary to design an output filter for the lowest frequency in the change range of the switching frequency. The drawback remains that it limits weight reduction.
Therefore, a circuit method capable of adjusting the output voltage at a fixed frequency is one of the problems of the resonance type DC-DC converter. As one method of this, for example, on September 8, 1989, the Institute of Electronics, Information and Communication Engineers Technical Research Report [Power Technology for Electronic Communications]
Parallel drive type voltage resonance type D announced at PE89-26
There is a C-DC converter. This parallel drive type voltage resonance type DC-DC converter will be explained. In FIG. 3, reference numeral 1 is a DC power source, and between its terminals, the primary winding 21 of the transformer 2, the resonance inductance 3 and the first winding 21. The field effect transistor 5, which is a switching element, is connected in series. At the end of the primary winding 21 of the transformer 2, a series circuit of a second resonance inductance 4 and a field effect transistor 6 which is a second switching element is connected in parallel. A resonance capacitor 7 is connected in parallel between the drain and the source of the field effect transistor 5 which is the first switching element, and a second resonance capacitor is similarly connected between the drain and the source of the field effect transistor 6 which is the second switching element. 8 are connected in parallel. The secondary winding 22 of the transformer 2 includes a rectifying diode 9 and a smoothing capacitor 10
Are connected in series. Both ends of the smoothing capacitor 10 are connected to the output terminals 31 and 32. The voltages at the output terminals 31 and 32 are connected to a comparison / error amplification circuit 11 that amplifies the error signal by comparing it with a reference voltage. The output signal of the comparison / error amplification circuit 11 delays the signal of the oscillation circuit 13 to control the phase difference between the field effect transistor 5 and the field effect transistor 6, and drives the field effect transistor 6.
It is connected to the. The field effect transistor 5 and the field effect transistor 6 operate at a fixed frequency and a fixed pulse width by the oscillation circuit 13, and the comparison / error amplification circuit 11 that amplifies the error signal between the output voltage and the reference voltage has the field effect transistor 5. And the phase difference between the field effect transistor 6 and the output voltage is stabilized. When the phase of the field effect transistor 5 which is the first switching element and the field effect transistor 6 which is the second switching element match, the maximum output is obtained, and on the contrary, the output is reduced as the phases are shifted.

However, in such a conventional parallel drive type voltage resonance type DC-DC converter which operates at a fixed frequency, two resonance inductances are required, which is an obstacle to miniaturization. However, there is a problem that it becomes expensive. The present invention is
An object of the present invention is to reduce the required number of resonance inductances in a parallel drive type voltage resonance type DC-DC converter.

In order to solve this problem, in the present invention, as the two inductances of the parallel drive type voltage resonance type DC-DC converter, the third and fourth windings having a low coupling rate to the transformer are used. Lines are provided for those 3rd, 4th
It proposes to utilize the leakage inductance of the winding as the resonance inductance.

FIG. 1 shows an embodiment of the present invention, which will be described below with reference to FIG. In the figure, 1 is a DC power supply, and between the input terminals 29 and 30 for receiving it,
The primary winding 21, the third winding 23, and the field effect transistor 5, which is the first switching element, of the transformer 2 are connected in series.
A fourth winding 24 and a field effect transistor 6 as a second switching element are connected in series to the primary winding 21 of the transformer 2. The third winding 23 and the fourth winding 24 of the transformer 2 intentionally lower the coupling rate with the iron core of the transformer 2 to increase the leakage inductance. A resonance capacitor 7 is connected in parallel between the drain and source of the field effect transistor 5, and similarly, a second capacitor is formed between the drain and source of the field effect transistor 6.
The resonance capacitor 8 is connected in parallel. The leakage inductance of the third winding 23 of the transformer 2 and the resonance capacitor 7 equivalently form a series resonance circuit. Also transformer 2
The leakage inductance of the fourth winding 24 and the resonance capacitor 8 equivalently form a series resonance circuit. Next, the rectifying diode 9 and the smoothing capacitor 10 are connected in series to the secondary winding 22 of the transformer 2. The smoothing capacitor 10 is connected to the output terminals 31 and 32. The error amplification circuit 11 that amplifies the error signal between the voltage of the output terminals 31 and 32 and the reference voltage, the signal of the oscillator 13 is delayed by the signal of the error amplification circuit 11, and the field effect transistor 5 and the field effect transistor 6 A phase control circuit 12 for controlling the phase difference and driving the field effect transistor 6 is connected between the oscillator 13 and the gate of the field effect transistor 6. The field effect transistor 5 and the field effect transistor 6 are operated by the oscillator 13 at a fixed frequency and a fixed pulse width. An error amplification circuit 11 that amplifies an error signal between the output voltage and the reference voltage determines the phase difference between the field effect transistor 5 and the field effect transistor 6 and stabilizes the output voltage. The maximum output is obtained when the phases of the field effect transistor 5 and the field effect transistor 6 match, and conversely, the output decreases as the phases are shifted. Although this circuit has no inductance in appearance, it uses a leakage inductance equivalently formed in the transformer to form a parallel drive type resonant DC-DC converter. The setting of the value of the resonance inductance can be achieved by adjusting the coupling rate so that the leakage inductance becomes the required value of the resonance inductance.

As described above, according to the present invention, in a parallel drive type resonance type DC-DC converter, by accommodating the required inductance equivalently in one transformer, It is possible to achieve further miniaturization and further economy.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a resonance type DC-DC converter according to the present invention.

FIG. 2 is a circuit diagram of a conventional parallel drive type resonant DC-DC converter.

[Explanation of symbols]

1 ... DC power supply 2 ... Transformer 21 ... Primary winding
22 ... Secondary winding 23 ... Third winding 24 ... Fourth winding 3,4 ... Resonance inductance 5,6 ... Field effect transistor 7,8 ... Resonance capacitor 9 ... Rectifier diode 10 ... Capacitor 11 ... Comparison / error amplification Circuit 12 ... Phase control circuit
13 ... Oscillator 29, 30 ... Input terminal 31, 32 ... Output terminal

Claims (1)

[Claims] 1. A pair of input terminals connected to a DC power source, a transformer, and a primary winding of the transformer, one end of which is connected to one end of the input terminal. ， Connected to the other end of this primary winding, the third coupling of transformer is low
A winding, a first switching element having a main terminal connected between the other end of the third winding and the other end of the input terminal, and a first switching element connected between the main terminal of the first switching element. First
Capacitor, a fourth winding connected to the other end of the primary winding and having a low coupling ratio of the transformer, and a main terminal between the other end of the fourth winding and the other end of the input terminal. A second switching element connected to the second switching element, a second capacitor connected between the main terminals of the second switching element, and 2 of the transformer.
A secondary winding, a rectifier connected to the secondary winding, a pair of output terminals connected to the rectifier, an oscillator circuit for driving the first switching element, and a pair of output terminals And a phase control circuit which operates by receiving the output of the comparison / error amplification circuit and which is connected between the output of the oscillation circuit and the second switching element. A series resonance circuit is formed by the leakage inductance of the third winding and the first capacitor, and a series resonance circuit is formed by the leakage inductance of the fourth winding and the second capacitor. A characteristic resonance type DC-DC converter.