JPH0686545A - Insulation type power supply circuit - Google Patents

Abstract

PURPOSE:To provide an insulation type power supply circuit capable of performing stabilization of an output voltage with a high accuracy by performing a feedback operation for an output voltage by switching operation using a pulse transformer without a photocoupler which has a possibility of the deterioration of characteristics. CONSTITUTION:The primary winding of a pulse transformer 8 and a transistor 7 are connected in series between output terminals, and the base of the transistor 7 is connected to an anode side of a first rectifying diode 5 through base resistor 7. At the secondary side of the pulse transformer, a portion of voltage drop in forward direction of a signal rectifying diode is corrected by a compensating diode 16 after DC conversion by the signal rectifying diode and a signal smoothening capacitor 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated power supply circuit for space, for example, and its output voltage is fed back to a control circuit on the primary side by using a pulse transformer to stabilize the output voltage.

[0002]

2. Description of the Related Art As an insulated power supply circuit, the one shown in FIG. 4 has been conventionally known. In the figure, 1 is a switching element, 2 is a power transformer, 3 is a drive circuit, 4 is a control circuit, 5 is a first rectifying diode, 6 is a smoothing capacitor, 20 and 21 are resistors for dividing an output voltage, 22 is a shunt regulator. , 23 are current limiting resistors, and 24 is a photocoupler.

Next, the operation will be described. Switching DC voltage with switching element 1 causes switching element 1
When the switching element 1 is non-conducting, electric power is stored in the power transformer 2, and when the switching element 1 is non-conducting, electric power is transmitted to the smoothing capacitor 6 through the first rectifying diode 5, and the DC voltage across the smoothing capacitor is supplied to the load. This output voltage is controlled by the duty cycle of the switching element, which is controlled by resistors 20, 21 which divide the output voltage.
It is compared with the internal reference voltage by the shunt regulator 22 which detects the voltage at the division point of, and a current is passed through the light emitting diode of the photocoupler 24 through the current limiting resistor 23. As a result, a DC voltage of a level corresponding to the output voltage is detected on the light receiving transistor side of the photocoupler 24, and the control circuit 4
Performs control at this voltage level, and drives the switching element 1 via the drive circuit 3. This operation stabilizes the output voltage.

[0004]

The conventional isolated power supply circuit is constructed as described above, and since the output voltage is fed back by the linear operation of the photocoupler, the characteristics of the photocoupler are deteriorated, especially in the space environment. There was a possibility that normal feedback could not be performed due to radiation deterioration in.

The present invention has been made in order to solve the above problems and provides output voltage feedback while ensuring insulation between the primary and secondary sides without using a photocoupler which may deteriorate characteristics. The purpose is to do.

[0006]

In the insulated power supply circuit according to the present invention, instead of a feedback circuit consisting of a photocoupler and a shunt regulator, an output voltage is switched by a transistor and a pulse transformer, and a secondary circuit of the pulse transformer is used. A rectifier circuit including a diode, a capacitor, and a resistor is provided on the side.

Further, a base-emitter resistor is connected between the base and emitter of the transistor which is further switched, and the base drive signal is rectified by a diode.

Further, a regenerative winding and a regenerative diode are added to the pulse transformer.

[0009]

According to the present invention, the transistor is switched on the secondary side in synchronism with the switching of the switching element, and the output voltage level is fed back to the primary side while achieving insulation through the pulse transformer. As a result, the control circuit performs control to stabilize the output voltage.

[0010]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 to 6 are the same as the above-mentioned conventional device. 7 is a transistor, 8 is a pulse transformer,
Reference numeral 9 is a base resistance, 10 is a zener diode, 11 is a signal rectifying diode, 12 is a signal smoothing capacitor, 13 is a resistor, 14 is a bias power supply, 15 is a current setting resistor, and 16 is a compensation diode.

Next, the operation will be described. 1 to 6 in FIG.
The operation up to is the same as that of the conventional circuit. The primary winding of the pulse transformer 8 and the transistor 7 are connected in series between the output terminals, and the base of the transistor 7 is connected to the anode side of the first rectifying diode via the base resistor 9.
The transistor 7 performs switching in synchronism with ON / OFF of the switch element on the primary side, and is turned off when the switch element 1 is on and turned on when the switch element 1 is off. The pulse transformer 8
The excitation energy of is absorbed by the Zener diode 10, and the pulse transformer 8 is reset while the switching is off. By this switching operation, the output voltage signal is transmitted to the secondary side of the pulse transformer 8. The transmitted signal is converted into a DC level by the signal rectifying diode 11 and the signal smoothing capacitor 12. The resistor 13 is for adjusting the frequency characteristic. Since the voltage level across the signal smoothing capacitor 12 includes the forward voltage drop of the signal rectifying diode 11, the RTN of the control circuit 4 is supplied from the bias power supply 14 via the current setting resistor 15.
A forward voltage drop of the signal rectifying diode 11 is offset by causing a current to flow to the side via the compensating diode 16.

Although the voltage level fed back to the control circuit 4 by the above operation varies depending on the turns ratio of the pulse transformer 8, if the turns ratio is 1: 1, the feedback voltage coincides with the output voltage. The voltage stabilization is controlled by.

Example 2. In the first embodiment, the drive signal is sent from the anode of the first rectifying diode 5 to the base of the transistor 7 through the base resistor 9, but the second rectifying diode 17 is inserted between them as shown in FIG. However, by connecting a resistor between the base and the emitter of the transistor 7, the same effect as that of the first embodiment can be expected while protecting an excessive reverse bias from being applied between the base and the emitter of the transistor 7.

Example 3. In the first embodiment, the excitation energy of the pulse transformer 8 is absorbed by the zener diode 10. However, as shown in FIG. 3, a winding is added to the pulse transformer 8 instead of the zener diode 10,
By regenerating the excitation energy to the smoothing capacitor through the regenerative diode 19, loss can be minimized and the same effect as that of the first embodiment can be expected.

In the above description, a transistor is used as the switching element on the secondary side, but it goes without saying that a similar circuit can be constructed by replacing it with an FET.

[0016]

As described above, according to the present invention, the switching operation is performed on the secondary side in synchronism with ON / OFF of the switching element, and the primary side is used while maintaining insulation from the secondary side by using the pulse transformer. Since the output voltage can be directly detected, there is an effect that the output voltage stabilization control can be accurately performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an isolated power supply circuit showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an isolated power supply circuit showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an isolated power supply circuit showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional insulated power supply circuit.

[Explanation of symbols]

 1 Switch Element 2 Power Transformer 3 Drive Circuit 4 Control Circuit 5 First Rectifying Diode 6 Smoothing Capacitor 7 Transistor 8 Pulse Transformer 9 Base Resistor 10 Zener Diode 11 Signal Rectifying Diode 12 Signal Smoothing Capacitor 13 Resistor 14 Bias Power Supply 15 Current Establishing Resistance 16 Compensation diode 17 Second rectifying diode 18 Base-emitter resistance 19 Regenerative diode 20 Dividing resistor 1 21 Dividing resistor 2 22 Shunt regulator 23 Current limiting resistor 24 Photocoupler

Claims (3)

[Claims] 1. A switching element for switching a DC input, a power transformer for connecting the switching element in series to a primary winding, and a secondary winding of the power transformer connected so as to conduct when the switching element is not conducting. And a smoothing capacitor that smoothes the output of the first rectifier diode, a drive circuit that drives the switching element, and a control circuit that supplies a drive control signal to the drive circuit. In an isolated power supply circuit that outputs an output voltage from both ends of a smoothing capacitor, a transistor that switches the output voltage, a pulse transformer that connects the transistor to a primary winding in series, and an anode of the first rectifying diode to the transistor The base resistance connected to the base of the And a signal-rectifying diode connected to the secondary winding of the pulse transformer so as to conduct when the transistor is conducting, and a zener diode connected in parallel between the emitter and the emitter of the pulse transformer. A signal smoothing capacitor connected to the cathode side of the diode to peak-hold the output of the pulse transformer, a resistor connected in parallel to the signal smoothing capacitor, and the signal rectifying diode in the secondary winding of the pulse transformer. A compensating diode in which an anode is connected to the terminal not connected and a cathode is connected to the RTN side of the control circuit, a resistor connected to the anode side of this diode, and a bias to which the other end of this resistor is connected. And a signal smoothing capacitor configured through the pulse transformer. Isolated power supply circuit, characterized in that to achieve voltage stabilization by feeding back the voltage to the control circuit. 2. A base-emitter resistor is connected between the base and emitter of the transistor, and a second rectifier diode is inserted between the anode and the base resistor of the rectifier diode.
2. The isolated power supply circuit according to claim 1, wherein an excessive reverse bias is protected between the base and the emitter of the transistor. 3. A winding provided on the pulse transformer instead of the zener diode that absorbs the excitation energy of the pulse transformer, and a regeneration that regenerates the excitation energy of the pulse transformer from this winding to the smoothing capacitor. Isolated power supply circuit consisting of a diode.