JPH0119592Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a switching type DC stabilized power supply device.
In particular, the present invention relates to the simplification of a voltage stabilization control circuit for a switching type stabilized power supply device that uses a secondary side control method.

Conventionally, many switching type stabilized DC power supplies having a circuit configuration as shown in FIG. 1 have been used. This is done by turning on and off the DC input 3 at a desired cycle by the first switching transistor 2 controlled by the control unit 1, and applying the rectangular wave voltage _E1 shown in FIG. 2a to the secondary winding side of the output transformer 4. make. Furthermore, the time width t of the positive polarity voltage is
The second switching transistor 6 controlled by the voltage stabilization control section 5 controls the DC output obtained through the rectifier and smoothing circuit 7 in synchronization with the rectangular wave voltage _E1 as shown in FIG. 2b. The voltage E ₃ is
As shown in FIG. 2c, it is made to remain approximately constant. In the figure, 8 is a load, and in the rectifier and smoothing circuit 7, L is a choke, C is a capacitor,
_D1 is a diode for discharging the energy stored in the choke L, and _D2 is a diode for blocking the negative polarity of the output voltage _E2 .

In this system, the output transformer 4 is provided with a plurality of secondary windings as required, and a corresponding voltage stabilization control section 5 is provided, thereby insulating the input DC power supply 1 with a reduced ripple component. This has the advantage of providing multiple stabilized DC outputs. Furthermore, since the switching periods of the first and second switching transistors 2 and 6 are made to match, the control unit 1
Mutual interference between the voltage stabilization control unit 5 and the voltage stabilization control unit 5 is greatly suppressed, which has the advantage of making it difficult to cause disturbances in operation, and in addition, it has various advantages such as being able to reduce switching loss of each switching transistor. It is known for that.

However, this system has the disadvantage that the voltage stabilization control section 5 is more complex than the other circuits forming the power supply, and the power supply is expensive.
That is, as shown in FIG. 1, the conventional voltage stabilization control unit 5 includes an error amplifier CM that compares the DC output voltage E ₃ and the reference voltage E _s and sends out an error voltage, and an input voltage E ₁ . Synchronous circuit S that creates a synchronized signal as
This creates a complex circuit consisting of a switching pulse width modulation circuit PM whose pulse width t changes in accordance with the error voltage in synchronization with _E1 , and a circuit AM which amplifies the signal and drives the second switching transistor 6. Since it has a circuit configuration, it has the disadvantage that the power supply device is expensive.

The present invention significantly simplifies the voltage stabilization control section compared to conventional ones, making it possible to provide an inexpensive DC voltage stabilization power supply device.The details will be explained below with reference to the drawings. do.

FIG. 3 is a circuit diagram (first embodiment) showing an embodiment of the present invention.
The same symbols as in the figures indicate equivalent parts. ), and is characterized in that the voltage stabilization control section 5 is formed as follows. That is, the first one is the DC output obtained by the voltage dividing resistors R ₄ and R ₅ by the error amplifier CM formed by the first and second transistors T _r1 and T _r2 , resistors R ₁ , R ₂ , R ₃ , etc. By comparing the divided voltage E′ ₃ of the voltage E ₃ and the reference voltage E _s , the amplified error voltage obtained at the output, that is, the collector of the second transistor T _r2 , causes the base of the second switching transistor 6 to be The point is that it is controlled.

The second point is that a synchronizing capacitor C _s is connected between the collector and emitter of the second transistor T _r2 of the error amplifier CM. However, since its capacitance value may be small, this is the second transistor T _r2
In some cases, it can be substituted by the parasitic capacitance between the collector and emitter of

In this way, the same effect as the conventional one can be obtained with a simple circuit. That is _, at the same time as the output voltage E ₁ on the secondary winding side of the output transformer 4 rises (time t ₁ ) as shown in FIG. C _s →resistance R ₁ ], a current flows for a short period of time, forcing the second switching transistor 6 to conduct. As a result, the output voltage _E2 rises as shown in FIG. 2b, the capacitor C of the rectifying and smoothing circuit 7 is charged, and the output voltage _E3 rises as shown in FIG. 2c. Therefore, the voltage is divided by resistors R ₄ and R ₅ , and the first transistor T _r1 of the error amplifier CM
The voltage applied to E′ ₃ also increases, and when it exceeds the voltage value of the set reference voltage E _s at time t ₂ , the operation of the error amplifier CM is reversed and the second transistor T _r2 becomes non-conducting. . As a result, the second switching transistor 6 also becomes non-conductive, and the output voltage _E2 immediately falls as shown in FIG. 2b. Then, as shown in FIG. 2c, the capacitor C of the rectifying and smoothing circuit 7 is discharged until the voltage _E1 rises again at time _t3 , and the output voltage _E3 is kept approximately constant.

That is, in the present invention, the voltage stabilization control section can be configured with a simple circuit using only the error amplifier CM and the synchronizing capacitor _Cs used in the conventional circuit, so the power supply device becomes inexpensive. Moreover, the control of the second switching transistor 6 is also performed in complete synchronization with the output voltage _E1 due to the action of the synchronizing capacitor _Cs , so that the same effect as the conventional circuit is obtained, such as no interference between control sections. be able to.

In addition, in the present invention, as shown in FIG. 3, a parallel connection circuit consisting of a resistor R6 and a capacitor C _T is connected between the collector of the second switching transistor ₆ and the base of the second transistor T _r2 of the error amplifier CM. Therefore, the _second
The conduction of the switching transistor 6 can be made more reliable. That is, the voltage appearing on the collector side of the second switching transistor ₆ , which becomes conductive at the same time as the output voltage E1 rises, charges the capacitor C _T and increases the base potential of the second transistor T _r2 of the error amplifier CM. The emitter-collector current is increased for a short period of time. As a result, the current flowing from the emitter to the base of the second switching transistor 6 is transferred to the synchronizing capacitor.
This improves the conduction, or synchronization, of the second switching transistor 6 to a greater extent than when using only _Cs . Further, when the second switching transistor 6 changes from conductive to non-conductive, the switching operation is ensured by the reverse process.

As is clear from the above explanation, according to the present invention, it is possible to configure a voltage stabilization control section with the same functions as the conventional one using a simple circuit, so a secondary side control type that is cheaper than the conventional one is adopted. A switching type DC stabilized power supply device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a waveform diagram of each part of the circuit, and FIG. 3 is a circuit diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Control part, 2... First switching transistor, 3... DC input, 4... Output transformer,
5... Voltage stabilization control unit, 6... Second switching transistor, 7... Rectifying and smoothing circuit, 8... Load, L... CHiyoke, C... Capacitor, D ₁ ,
D ₂ ... diode, CM ... error amplifier, T _r1 ,
T _r2 ... Transistor, R ₁ , R ₂ , R ₃ ... Resistance, E _s
...Reference voltage, E ₃ ...DC output voltage, R ₄ , R ₅ ...
...Voltage division resistor, S...Synchronization circuit, PM...Pulse width modulation circuit, AM...Drive circuit, _Cs ...Synchronization capacitor, _R6 ...Resistance, C _T ...Capacitor.

Claims (1)

[Claims for Utility Model Registration] Connecting the primary winding of an output transformer and a first switching transistor in series to a DC input power source,
a circuit that controls on/off the first switching transistor to generate a rectangular wave alternating current voltage in the secondary winding of the output transformer; and a second switching circuit connected in series to the secondary winding of the output transformer. A switching type DC stabilized power supply device comprising a circuit for supplying DC output to a load via a transistor and a rectifying and smoothing circuit, and a voltage stabilization control section for the second switching transistor, wherein the voltage stabilization control section is an emitter. has first and second transistors connected in common;
A DC output voltage is applied to the base of the transistor, a reference voltage is applied to the base of the second transistor, and a synchronizing capacitor is connected between the emitter and collector, and the collector is connected to the second transistor. A switching type DC stabilized power supply device equipped with an error amplifier connected to the base of two switching transistors.