JPH09149634A - Switching power device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the increase of an energy loss generated in a second high- frequency rectifying circuit by starting operation on the basis of the operation stop of a first regulator circuit, and rectifying a divided voltage on the secondary side of an output transformer and producing a DC voltage. SOLUTION: When the secondary winding of an output transformer is a standard voltage a DC voltage obtained by rectifying it with a first rectifying diode 5 is a standard voltage, and no current flows in a branch circuit composed of the cathode, a resistor, a zener diode, and a resistor, so an NPN transistor 4 for a gate is off. Accordingly, the base of an NPN transistor 3 for a series regulator of a second regulator circuit is grounded through a resistor R4, so it is turned off. And a bias voltage obtained by dividing a DC voltage obtained by rectifying with the first rectifying diode 5 with resistors R5, R6 is supplied to the base of an NPN transistor 2 for a series regulator of a first regulator circuit, so a rectified and smoothed DC is outputted. As the result, it becomes possible to prevent the increase of an energy loss generated in a second high-frequency rectifying circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flyback converter type switching power supply device having multiple outputs.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of an embodiment of a switching power supply device having a flyback converter system and multiple outputs. Reference numeral 21 is a rectifier circuit that rectifies and smoothes an input commercial power source, for example, AC (AC) 100V or the like to generate DC (DC). Reference numeral 22 is a switching circuit for generating a high frequency pulse, for example, a high frequency pulse of 30 kHz by self-excited oscillation using a switching transistor and an output transformer. Reference numeral 23 is an output transformer (high frequency transformer) whose primary side and secondary side have opposite polarities. An output voltage adjusting circuit 24 controls the duty ratio or frequency of the high frequency pulse generated by the switching circuit 22 to make the output voltage a constant voltage. Reference numerals 25 and 26 are a first high-frequency rectifier circuit and a second high-frequency rectifier circuit that receive a required pulse voltage from the secondary side of the output transformer, rectify and smooth it, and generate direct current. 27 is a constant voltage control circuit that detects the output voltage of the first high-frequency rectifier circuit 25, compares it with a reference voltage, and generates a current proportional to the difference. 28 is
It is a photo coupler in which a photodiode is caused to emit light by a current proportional to the difference and the phototransistor receives the emitted light to transmit a signal.

A DC generating operation of the flyback converter type switching power supply device shown in FIG. 2 will be described. The rectifier circuit 21 receives commercial power and generates a corresponding DC,
The switching circuit 22 connected to the next stage generates a required high frequency pulse, for example, a high frequency pulse of 30 kHz or the like. The high-frequency pulse applied to the primary winding of the output transformer 23 generates a voltage of opposite polarity on the same secondary side, and the secondary winding of the first high-frequency rectifying circuit 25 and the secondary winding of the second high-frequency rectifying circuit 26. It produces a high frequency pulse in the winding which is proportional to the turns ratio. The first high frequency rectification circuit 25 and the second high frequency rectification circuit 26
Then, the high frequency pulse generated in the secondary winding is rectified and smoothed to generate voltage-stabilized (regulated) DC.
The constant voltage control circuit 27 detects the output voltage of the first high-frequency rectifier circuit 25, compares it with a reference voltage, generates a current proportional to the difference, and supplies it to the photodiode of the photocoupler 28. The phototransistor of the photocoupler 28 is
The light emitted due to the current is input and a corresponding current is generated. The output voltage adjusting circuit 24 generates a control signal for generating a high frequency pulse having a required frequency with a constant duty ratio based on the corresponding current, and supplies the control signal to the switching circuit 22.

Therefore, when the load of the first high-frequency rectifier circuit 25 increases, the output current of the first high-frequency rectifier circuit 25 increases, and when the output voltage decreases, the constant voltage control circuit 27 changes based on the reference voltage ( A current proportional to (difference) is generated, and the fluctuation signal is transmitted to the output voltage adjusting circuit 24 via the photocoupler 28. The output voltage adjusting circuit 24 controls the switching circuit 22 so as to decrease the frequency while keeping the duty ratio constant, for example. As a result of this control, a large amount of energy is transmitted to the secondary side of the output transformer 23, the output current increases, and
It is possible to cope with the accompanying decrease in output voltage (constant voltage control of flyback converter method).

FIG. 3 is a circuit diagram of an embodiment of the second high frequency rectifier circuit. However, in the flyback converter type constant voltage control, more energy is transferred to the secondary winding of the second high-frequency rectifier circuit 26 shown in FIG. 3, and the rectified voltage at the point A increases. . As a result, there is a problem that the loss in the regulator transistor TR1 increases.

[0006]

The present invention has been made in view of the above problems, and prevents an increase in energy loss newly generated in the second high frequency rectifier circuit when the first high frequency rectifier circuit is subjected to constant voltage control. It is an object of the present invention to provide such a switching power supply device.

[0007]

To achieve the above object, a rectifier circuit that rectifies and smoothes an input commercial power source to generate a direct current, a switching circuit that generates a high frequency pulse, and a next stage of the switching circuit. An output transformer whose primary side and secondary side have opposite polarities, an output voltage adjusting circuit that controls the duty ratio or frequency of the high frequency pulse generated by the switching circuit to make the output voltage a constant voltage, and the output transformer A first high-frequency rectifier circuit that receives alternating current from the secondary side of the, and rectifies and smoothes it to generate direct current;
A second high-frequency rectifier circuit, a constant voltage control circuit that detects the output voltage of the first high-frequency rectifier circuit, and generates a corresponding current by comparing it with a reference voltage, and transfers the current to the output voltage adjustment circuit. In a switching power supply device configured with a photocoupler, a first regulator circuit that rectifies the entire secondary voltage of the output transformer by the second high-frequency rectifier circuit to generate direct current, and the operation of the first regulator circuit is stopped. And a second regulator circuit for starting direct current operation and rectifying the voltage on the secondary side of the output transformer to generate direct current.

[0008]

With the above configuration, when the voltage generated in the secondary winding of the output transformer increases and exceeds the set value, the first regulator circuit stops the rectifying operation,
The second regulator circuit starts to operate and rectifies the divided voltage of the secondary winding of the output transformer to generate direct current.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A switching power supply device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of a high frequency rectifier circuit portion of a switching power supply device according to the present invention. Reference numeral 1 denotes a secondary winding of the output transformer 23 (FIG. 2), which is composed of taps at both ends and an intermediate tap. Reference numeral 2 is a series regulator NPN transistor (TR1) of the first regulator circuit. The collector is connected to the cathode of the first rectifying diode 5, the anode of which is connected to the tap, the emitter is connected to the output terminal, and the base is connected to the base. Connect in series between cathode ground 2
It is connected to the middle point of the resistance of the book and the other end is connected to the Zener diode (D3) grounded. Reference numeral 3 is a series regulator NPN transistor (TR2) of the second regulator circuit. The collector is connected to the cathode of the second rectifying diode 6 whose anode is connected to the intermediate tap, and the emitter is connected to the output terminal. Is connected in series between the cathode of the first rectifying diode 5 and the ground (R3) and the gate transistor (TR
The collector and the emitter of 3) and the resistor (R4) are connected to the emitter of the branch, and the other end is connected to the Zener diode (D4) grounded.

Reference numeral 4 is a gate NPN transistor (TR
3), and the collector and the emitter are connected to the resistor (R3) connected in series between the cathode of the first rectifying diode 5 and the ground, and the collector and the emitter of the gate transistor (TR3) as described above. , Resistance (R
4) Depending on the connection. The base is a resistor (R1) connected in series between the cathode of the first rectifying diode 5 and the ground, a zener diode (D1), and the zener diode (D1) at the midpoint of the resistor (R2). It is connected to the anode. Reference numerals 5 and 6 denote a first rectifying diode of the first regulator circuit and a second rectifying diode of the second regulator circuit. The first rectifying diode 5 has an anode connected to the tap and a cathode connected to the series regulator. NPN transistor (TR
1) Connect to the collector of 2 etc. The second rectifying diode 6 has an anode connected to the intermediate tap and a cathode connected to the collector of the series regulator NPN transistor (TR2) 3.

The high frequency rectification operation of the switching power supply device according to the present invention will be described with reference to FIG. First, the case where a standard voltage is generated in the secondary winding of the output transformer 23 (FIG. 2) will be described. The direct current rectified by the first rectifying diode 5 is a standard voltage, and in this case, the cathode of the first rectifying diode 5 and the output transformer 23 (FIG. 2).
The resistor connected in series between the secondary winding and the tap of the winding, the Zener diode, and the branch of the resistor are set so that no current flows. Therefore, the gate of the gate NPN transistor (TR3) 4 has almost zero voltage, and the gate NPN transistor (TR3) 4 is OFF. Therefore, since the base of the series regulator NPN transistor (TR2) 3 of the second regulator circuit is grounded via the resistor (R4), the series regulator NPN transistor (TR2) 3 is OFF.

On the other hand, the series regulator NPN transistor (TR1) 2 of the first regulator circuit supplies to the base a required bias voltage obtained by dividing the direct current rectified by the first rectifying diode 5 with resistors (R5, R6). Since it is set so as to conduct and conduct, DC that is rectified / smoothed and voltage-stabilized (regulated) is generated and output.

Next, a case where a high voltage exceeding the standard voltage is generated in the secondary winding of the output transformer 23 (FIG. 2) will be described. Since the direct current rectified by the first rectifying diode 5 becomes a high voltage, it is connected in series between the cathode of the first rectifying diode 5 and the tap of the secondary winding of the output transformer 23 (FIG. 2). A current flows through the resistor, the Zener diode and the resistor branch. Therefore, N for gate
Since the gate of the PN transistor (TR3) 4 is biased to a required voltage, the gate NPN transistor (TR3) 4 is ON. Therefore, the series regulator NPN transistor (T
The base of R1) 2 is a diode (D2) and a resistor (R
4) and is grounded, and as a result, the series regulator NPN transistor (TR1) 2 is turned off.

Further, the base of the series regulator NPN transistor (TR2) 3 of the second regulator circuit is biased with a voltage corresponding to the voltage drop of the resistor (R4), and becomes conductive. Therefore, the second regulator circuit uses the high voltage component voltage, for example, approximately the same as the high voltage via the cathode of the second rectifying diode 6 whose anode is connected to the intermediate tap of the secondary winding of the output transformer 23 (FIG. 2). A standard voltage or the like is supplied, and DC that is rectified and smoothed based on the same voltage to generate voltage-stabilized DC is output. The series regulator transistors 2 and 3 of the first regulator circuit and the second regulator circuit, and the gate transistor 4
Is not limited to an NPN transistor, but may be a relative circuit using a PNP transistor.

[0015]

As described above, the present invention provides a switching power supply device which prevents an increase in energy loss newly generated in the second high frequency rectifier circuit when the first high frequency rectifier circuit is subjected to constant voltage control. Therefore, the constant voltage control of the flyback converter divides the high voltage generated in the secondary winding of the second high-frequency rectifier circuit, and rectifies and smoothes it based on the divided voltage to stabilize the voltage. There is an advantage that it is possible to reduce the increase in loss in the regulator transistor.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a high frequency rectifier circuit portion of a switching power supply device according to the present invention.

FIG. 2 is a block diagram of an embodiment of a switching power supply device having a flyback converter system and multiple outputs.

FIG. 3 is a circuit diagram of an embodiment of a second high frequency rectifier circuit.

[Explanation of symbols]

1 Secondary winding 2 Series NPN transistor for regulator (TR
1) NPN transistor for 3 series regulator (TR
2) 4 gate NPN transistor (TR3) 5 first rectifying diode 6 second rectifying diode 21 rectifying circuit 22 switching circuit 23 output transformer 24 output voltage adjusting circuit 25 first high frequency rectifying circuit 26 second high frequency rectifying circuit 27 fixed Voltage control circuit 28 Photo coupler

Claims (6)

[Claims] 1. A rectifying circuit for rectifying and smoothing an input commercial power source to generate a direct current, a switching circuit for generating a high frequency pulse, and a primary winding and a secondary winding connected to the next stage of the switching circuit. And an output transformer having opposite polarities, an output voltage adjusting circuit for controlling the duty ratio or frequency of the high frequency pulse generated by the switching circuit to make the output voltage a constant voltage, and an alternating current from the secondary side of the output transformer. A first high-frequency rectifier circuit that receives, rectifies and smoothes and generates a direct current, a second high-frequency rectifier circuit, and an output voltage of the first high-frequency rectifier circuit is detected and compared with a reference voltage to generate a corresponding current. A switching power supply device comprising a constant voltage control circuit and a photocoupler for transmitting the current to the output voltage adjusting circuit, wherein the second high frequency rectification circuit outputs the second high frequency rectification circuit. A first regulator circuit that rectifies all the voltage generated on the secondary side of the lance to generate a direct current, and starts operation based on the operation stop of the first regulator circuit to reduce the divided voltage on the secondary side of the output transformer. A switching power supply device comprising a second regulator circuit that rectifies and generates a direct current. 2. The switching power supply device according to claim 1, wherein the first regulator circuit and the second regulator circuit are connected in parallel. 3. The switching power supply device according to claim 1, wherein the first regulator circuit is provided with a gate NPN transistor for controlling the base bias voltage of the series regulator NPN transistor. 4. The base of the gate transistor is
The Zener in the branch formed by the resistor, the Zener diode, and the resistor, which are connected in series between the cathode of the rectifying diode whose anode is connected to one end of the secondary winding of the output transformer and the other end of the secondary winding. The gate of the gate NPN transistor is connected to the anode of the diode, the collector of the gate NPN transistor is connected to the cathode of the rectifying diode via a resistor, and the collector of the series regulator NPN transistor is connected in the forward direction via the diode. 4. The switching power supply device according to claim 3, wherein the emitter of the NPN transistor is connected to the other end of the secondary winding of the output transformer via a resistor. 5. The series regulator NPN transistor collector is connected to the cathode of a rectifying diode whose anode is connected to the center tap of the secondary winding of the output transformer, and the collector of the series regulator NPN transistor is connected to the series regulator. The base of the NPN transistor is connected to the other end of the secondary winding through a Zener diode and the emitter of the gate NPN transistor, and the emitter of the series regulator NPN transistor is connected to the first regulator circuit. 5. The switching power supply device according to claim 4, wherein the switching power supply device is connected in parallel to the emitter of the series regulator NPN transistor. 6. The switching power supply device according to claim 3, wherein the series regulator transistor and the gate transistor of the first regulator circuit and the second regulator circuit are PNP transistors.