JPS62144571A - Switching power source unit - Google Patents

Abstract

PURPOSE:To keep the output constant without lowering the power conversion efficiency by changing the resonance frequency of the resonance circuit connected to the controlled winding of a saturable reactor transformer accompanied by the fluctuation of the output voltage and voltage fluctuation at power source. CONSTITUTION:A controlled winding 16b of a saturable reactor transformer 15 is connected serially to the secondary winding N3 of a power transformer 8 to constitute the resonance circuit made up of the secondary winding N3 - the controlled winding 16b - a condenser C4. The output voltage of a rectification circuit 9c is detected by a control circuit 17. By supplying the corresponding control voltage to the control winding 16a of the saturable reactor transformer 15, the resonance frequency of the resonance circuit is controlled and the output voltage is always kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is suitable for use as a power supply device for electronic equipment such as a television receiver.

[Summary of the invention]

A resonant circuit is constructed by connecting the controlled winding of a saturable reactor transformer and a capacitor to the secondary winding of a power transformer, whose primary winding is supplied with a current that is switched at a predetermined period. By supplying the control winding with an output corresponding to the output obtained from the resonant circuit, this output is always kept constant.

[Conventional technology]

The applicant previously filed Japanese Patent Application No. 60-203942 as a switching power supply device that controls switching of DC input current and obtains a desired voltage via a power transformer.
Using an orthogonally coupled saturable reactor transformer,
By controlling the inductance of this saturable reactor transformer according to the secondary side of the power transformer, that is, the output voltage, the oscillation frequency of the oscillation circuit that switches the DC input current can be controlled, that is, the switching period of the DC current can be controlled. We proposed a switching power supply device that stabilizes the output voltage of a power transformer.

To explain this with reference to FIG. 2, (1) is a commercial AC power supply (^C), which fluctuates within a range of approximately 9QV to 144V. (2) is a rectifier circuit, and (3) is a smoothing capacitor. (4) is an oscillation circuit, and (5) is a saturable reactor transformer (hereinafter referred to as PR lance). This PR) lance (5) has a primary winding NA, two 2
It has a secondary winding N B1 + N 82 and a control winding Nc, and has four magnetic legs (7a) to (7d) as shown in FIG.
Two adjacent magnetic legs (7a) of a magnetic core (7e) having
) and (7b), the primary and secondary windings NA,
Winding NB□ and NB2, these windings NA+N R
1, one turn of winding is sufficient in the direction perpendicular to the winding direction of N 82, and two secondary windings N 81 , N
For both 82, about 5 tans is sufficient. In addition, since the control winding NC does not require a current amount, a thin wire can be used, and 1000
It is wound around a turn.

The oscillation circuit (4) has switching transistors Q1 and C2, and the secondary winding NF11- of the PR transformer (5).
Capacitor C1 - Resonant circuit passing between the base and emitter of transistor Q1, and secondary winding NB2 - Capacitor C2
- constitutes a resonant circuit passing between the base and emitter of transistor Q2. Note that R1 and R2 are starting resistors.

Then, the DC current obtained in the capacitor (3) is switched by the transistor Q1, and the PR) lance (5)
The power is supplied to a series resonant circuit consisting of a capacitor (6) and a primary winding N1 of a power transformer (8) through a primary winding NA of the power transformer (8).

The power transformer (8) has three windings N2, N3,
N4 is wound, and winding N2. Parallel resonance capacitors C3 and C4 are connected to N3, respectively. Winding N4 is for the heater and provides a voltage of 6.3v.

Further, rectifier circuits (9a) and (9b) are connected to the winding N2, and DC voltages El (for example, +15 cm) and B2 (for example, -15 cm) are obtained, respectively. A rectifier circuit (9c) is connected to the winding N3, and a DC voltage E3 (for example, 200V) is connected to the winding N3 through a series regulator (11).
) is obtained. This series regulator (11) has a well-known configuration, and although detailed explanation will be omitted, C3 is a main transistor, Q is a voltage comparison transistor, and D2 is a constant voltage element such as a Zener diode.

The voltage E1 from the rectifier circuit (9a) mentioned above is applied to the control circuit (
10) and corresponds to this voltage E1.
This control voltage ec is supplied to the control winding Nc of the PR lance (5).

To explain the operation of this circuit, when the power supply switching SW is turned on, the transistor Q1. Direct current is supplied to Q2, kicking them in and starting the switching operation. That is, the transistor Q1 is switched by the resonant current passing through the resonant circuit of the secondary winding NB1 of the PRI lance (5) and the capacitor C1, and similarly, the resonant current passing through the resonant circuit of the secondary winding NB2 and the capacitor C2 switches the transistor Q1. Transistor Q2 is switched. and both transistors Q1. Q2 is selected so that its on and off operations are opposite to each other, that is, it operates in oscillation.

By turning on and off the transistor Q1, the PR) lance (5
), a current is supplied to the resonant circuit of the capacitor (6) and the primary winding N1 of the power transformer (8) through the primary winding NA of the power transformer (8), and therefore voltage E is applied to the secondary side of the power transformer (8)
1. E2, B3 and 6.3V are obtained.

Here, currents rs1., . . . , flow through the secondary windings NB□ and NB2 of the PR transformer (5), respectively. Is2 and the respective inductances L 81 r L 82 are the control currents supplied to the control winding Nc when a magnetic core gap is provided at only one leg of the orthogonal PR transformer (5) as shown in FIG. It changes as shown in FIG. 4 depending on the IC.

Therefore, as shown in Figure 5, 2 of the power transformer (8)
If the control circuit (10) is designed so that the control current IC is controlled in response to changes in the load current IL on the next side and fluctuations in the voltage of the AC power supply (1), the oscillation frequency of the oscillation circuit (4) As shown in FIG. 6, f is controlled with respect to changes in the load current IL and voltage fluctuations of the AC power source (II).

According to such a switching power supply device, the PR transformer (5) is used to control the oscillation frequency of the oscillation circuit (4), and because of the small amplitude operation, there is little core loss at high frequencies, and the switching frequency can be increased to 100 KHz. ~150KHz
Or more can be set.

In addition, as mentioned above, it is possible to select a high operating frequency for the PR transformer (5), the number of turns of each winding can be small, and a thin wire can be used for the control winding Nc, etc.
The entire lance (5) can be made smaller, generates less heat, so natural air cooling is sufficient, and has an AC-DC conversion efficiency of 77A.
As shown in Fig. 7, c-oc is y' in the maximum load state.
90%, and has features such as low loss.

[Problem that the invention seeks to solve]

In the above-mentioned circuit configuration, when it is necessary to obtain a plurality of outputs from the power transformer (8), the outputs forming the feedback loop including the control circuit (10), that is, the outputs for obtaining the voltages El and E2 in the embodiment, are Through the above operation, a constant output is obtained, but the output that does not form a feedback loop or cannot form a feedback loop, that is, the output that obtains the voltage E3 in the example, is stabilized. In order to do this, it is necessary to insert a series regulator (11).

However, when using this series regulator, voltage fluctuations of the power supply (1) (for example, 90 V to 1
50V), the output voltage of the rectifier circuit (9C) is 2
Design the secondary winding N3 so that the voltage is 10V to 290■,
This voltage is lowered by a series regulator (11) to 200μ. Therefore, as is well known, the collector loss of transistor Q3 is large (therefore, it is necessary to add a large heat sink to this transistor Q3, and the conversion efficiency is 7^C due to the large power loss).
-The transistor Q3 has the problem that DC drops to 81% or less, reliability cannot be ensured due to heat generation, and the price is high, and when the output terminal from which this voltage E3 is obtained is short-circuited.
There are problems such as the need to add a circuit to protect Q4.

[Means for solving problems]

The present invention solves the above-mentioned problems and uses a saturable reactor transformer (also called a PR lance) for the output winding in which no feedback loop is formed.
The controlled winding (16b) of (15) is inserted in series, and this controlled winding (16b) - output winding (N5 in this example) -
A resonant circuit is formed by the capacitor C4, and the output voltage from this output winding is converted into a control voltage by the control circuit (17), and this control voltage is supplied to the control winding (16a) of the PRI-lance (15). This is how it was done.

[Effect]

Fluctuations in the output voltage E3 of the secondary winding N3 of the power transformer (8) are transmitted through the control circuit (17) (PR) lance number is the voltage E
3, so that the output voltage E3 can always be kept constant.

〔Example〕

Referring to FIG. 1 An example of a switching power supply device according to the present invention will be described with reference to FIG. However, parts corresponding to those in FIG. 2 are given the same reference numerals and their explanations will be omitted.

That is, in the present invention, the controlled winding (16b) of the PR lance (15) is connected in series with the secondary winding N3 of the power transformer (8), and the secondary winding N3 - A resonant circuit is formed by the control winding (16b) and the capacitor C4, and the output voltage E3 of the rectifier circuit (9C) is connected to the control circuit (17
), and the corresponding control voltage vc (control current ic) is detected by the control winding (16) of the PR lance (15).
This is what was supplied to a). PR in this case) Lance (
15) can be constructed in the same manner as that explained in FIG. 3, and Nc as the control winding (16a),
Also, NA can be used as the controlled winding (16b).

Note that this example shows a case where the rectifier circuit (9c) is configured as a so-called voltage doubler rectifier circuit to obtain a voltage E4 which is 1/2 of the voltage of the voltage E3. There is no direct relation to the abstract.

According to this configuration, when the load at the output terminal E3 fluctuates during operation of the circuit, that is, when the load current IL changes as shown in FIG. 8, the control circuit (17)
Since the control current i(,) to the control winding (16a) of the PR transformer (15) changes, the controlled winding (16a) of the PR transformer (15) changes.
b) The resonant frequency of the resonant circuit including b) changes. That is, the ninth
As shown in the figure, the resonance frequency f1 when the load is small
The resonant frequency f2 when the load becomes larger, that is, Δ
The resonant frequency of f-length is uneven. As a result, the output voltage E
3 can be kept constant at 200v, for example.

In the cases shown in Figures 8 and 9, as the load increases, the control current to the PR transformer (15) is reduced, the inductance of the controlled winding (16b) is lowered, and the resonant circuit is This is a case in which the resonance frequency f is increased, but it is also possible to operate in the completely opposite direction. FIGS. 10 and 11 show examples of this case.

In addition, although Fig. 1 shows the case where the control system including the second winding N3 and the control circuit (17) is provided at least one length on the secondary side of the power transformer (8), Without limitation, a plurality of sets of similar configurations can be provided on the secondary side of this power transformer (8).

Figure 12 shows another embodiment, which can be used as a switching power supply for electronic equipment with relatively small load power.This example shows a case where one transistor Q1 is used as the oscillation circuit (4). Since the other details are the same as those in FIG. 1, detailed explanation thereof will be omitted.

〔Effect of the invention〕

According to the present invention described above, a saturable reactor transformer (15) is used instead of the conventional series regulator (11) as shown in FIG. 2, which causes a relatively large power loss. By doing so, the resonant frequency of the resonant circuit connected to the controlled winding can be changed and controlled to be constant according to the fluctuation of the output voltage and the voltage of the power supply (1). It has the characteristics that it is possible to increase the power conversion efficiency, because only a small amount of loss occurs in the transformer, and there is no need for heat dissipation means.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a switching power supply device according to the present invention, FIG. 2 is a circuit diagram showing an example of a switching power supply device previously proposed by the applicant, and FIG. 3 is a circuit diagram showing an example of a switching power supply device previously proposed by the applicant. Fig. 4 is a characteristic curve diagram showing the characteristics of this saturable reactor transformer, and Figs. 5 and 6 show control current and oscillation frequency with respect to load current. Figure 7 is a characteristic diagram showing the AC-DC conversion efficiency with respect to AC power supply voltage, Figures 8 and 10 are changes in the control current supplied to the saturable reactor transformer with respect to changes in load current. Figures 4, 9 and 11 are curve diagrams showing changes in output voltage with respect to the resonant frequency of a resonant circuit including a saturable reactor transformer, and Figure 12 is another embodiment of the switching power supply according to the present invention. FIG. (4) is an oscillation circuit, (5) and (15) are saturable reactor transformers, and (10) and (17) are control circuits.

Claims (1)

[Scope of Claims] A switching power supply device in which a DC input current is switched at a predetermined period and is supplied to a primary winding of a power transformer, and an output is taken out from the secondary winding of the power transformer. The controlled winding of the saturable reactor transformer is connected in series to the secondary winding of the transformer, a capacitor is connected in parallel to the series circuit to form a resonant circuit, and the output obtained from the resonant circuit is controlled. A switching power supply device characterized in that the power is supplied to the control winding of the saturable reactor transformer through a circuit.