JP2797568B2 - DC power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-output type DC power supply device incorporated in an electronic device or the like.

2. Description of the Related Art A circuit example of a conventional multi-output type DC power supply is shown in FIG.
Shown in the figure. In FIG. 3, a DC voltage is input to a voltage input terminal 1 from the outside, and the voltage is converted by a collector of an AVR output transistor 2 and a resistor 3, a constant voltage diode 5, and a smoothing capacitor 4, and the AVR output transistor 2 Supplied to the base. The emitter of the AVR output transistor 2 is connected to the smoothing capacitor 6 and the first output terminal 7. The power supply circuit that outputs the converted DC voltage to the first output terminal 7 is referred to as a first power supply circuit. On the other hand, the DC voltage input from the voltage input terminal 1 is supplied to the primary winding terminal P1 of the switching transformer 9 via the switch 8;
The other end P2 of the primary winding terminal of the switching transformer 9
Is connected to the collector of a switching output transistor 10 so that a driving voltage is supplied to the base of the switching output transistor 10 from an oscillation circuit 11.
A rectifying / smoothing diode 12 and an electrolytic capacitor 13 are connected to the secondary winding terminal S1 to generate a DC voltage, which is output to a second output terminal 14. Similarly, a rectifying / smoothing diode 19 and an electrolytic capacitor 20 are connected to the secondary winding terminal S2 of the switching transformer 9 to generate a DC voltage and output it to the third output terminal 21 for multi-output.
This constitutes a second power supply circuit unit of the DC-DC switching system. As for the output of the first power supply circuit unit, a DC voltage is output from the first output terminal 7 while the voltage is being input from the input terminal 1. The output of the second power supply circuit is controlled by the switch 8, and only when the switch 8 is in a closed circuit (switch-on) state is the output voltage connected to the second output terminal 14 and the third output terminal 14. Output to the output terminal 21.

Problems to be Solved by the Invention A conventional power supply circuit including a first power supply circuit section that constantly outputs a DC voltage and a second power supply circuit section having a function of turning on and off an output voltage by a switch. In the output type DC power supply device, the voltage conversion loss of the first power supply circuit section is constantly occurring.

The present invention has been made to solve the above-described problems, and has as its object to reduce power conversion loss and improve efficiency.

Means for Solving the Problems In order to achieve the above object, the present invention provides a detecting section for detecting an output voltage of a second power supply circuit section provided with a switch (power switch). The base voltage of the AVR output transistor of the first power supply circuit unit which generates the electric current is controlled to be turned on / off by using a transistor, and a voltage is applied from the second power supply circuit unit to the output terminal of the first power supply circuit unit via a diode. And a voltage switching circuit for supplying the power supply, and switches the output terminal voltage of the first power supply circuit to the output voltage of the second power supply circuit while the switch is closed and the second power supply circuit is operating. It is like that.

Effect of the Invention According to the above configuration, when the switch (power switch) is open (power switch is OFF), the output voltage of the first power supply circuit is output to the output terminal, and when the switch is closed (power switch). Is ON), the output voltage of the first power supply circuit section is cut off, and the voltage is supplied from the second power supply circuit section to the output terminal, thereby reducing the voltage conversion loss.

Embodiment FIG. 1 shows a circuit diagram of an embodiment of the present invention. In the figure,
A DC voltage is externally input to a DC voltage input terminal 1 of a multi-output type (3 outputs in the illustrated example) DC power supply, and a collector of an AVR output transistor 2 and a resistor 3, a constant voltage diode 5, and a smoothing capacitor 4 are used. Convert the voltage to the above AVR
It is supplied to the base of the output transistor 2. The emitter of the AVR output transistor 2 is connected to the smoothing capacitor 6 and the first output terminal 7, and the converted DC voltage is output from the first output terminal 7. This power supply circuit is called a first power supply circuit section. The DC voltage input from the voltage input terminal 1 is supplied to a primary winding terminal P1 of a switching transformer 9 via a switch (power switch) 8. The other end P2 of the primary winding terminal of the switching transformer 9 is connected to the collector of the switching output transistor 10, and the base of the transistor 10 is supplied with a driving voltage from the oscillation circuit 11. A rectifying / smoothing diode 12 and an electrolytic capacitor 13 are connected to the secondary winding terminal S1 of the switching transformer 9 to generate a DC voltage having a voltage value equivalent to the output voltage of the first power supply circuit. , To the second output terminal 14. As described above, the diode 19 for rectification and smoothing and the electrolytic capacitor 20 are connected to the secondary side line terminal S2 of the above-mentioned stitching transformer 9 to generate a DC voltage and output it to the third output terminal 21. This is the second of the multiple output DC-DC switching method.
Power supply circuit section. The second output terminal 14 is provided with a voltage detector for detecting the voltage by dividing the voltage of the second terminal 14 with the resistors 15 and 16, and providing a voltage between the first output terminal 7 and the second output terminal 14. The diode 18 so that the cathode side is on the first output terminal 7 side (in the case of a negative voltage, the reverse direction).
And the output voltage of the voltage detection unit is supplied to the base of the transistor 17. Transistor 17
Connect the collector to the base of the above AVR transistor 2,
The emitter is turned on when the detection voltage is generated by grounding, shuts off the AVR output transistor 2, and outputs the output voltage from the second power supply circuit unit to the first output terminal 7 via the diode 18. Are configured to be supplied. The voltage switching timing of the first output terminal 7 will be described with reference to FIG.

In FIG. 2, Va is a base voltage of the AVR output transistor 2, V1 is a first output terminal voltage, and V2 is a second output terminal voltage. When the switch 8 is open (while the power switch is OFF), the transistor 17 is turned off, the Va voltage becomes the rated voltage, and the output voltage of the first power supply circuit is output to the output terminal 7. On the other hand, when the switch is closed (while the power switch is ON), the transistor 17 is turned on, the AVR output transistor 2 is cut off, the output voltage of the first power supply circuit is cut off, and the diode is supplied from the second power supply circuit unit. A voltage is supplied to the output terminal 7 via 18.

As described above, according to the present invention, according to the present invention, a first power supply circuit unit that constantly outputs a DC voltage without a switching device, and a second power supply that includes a switching device and outputs a DC voltage only during a switch-on period In a multi-output type DC power supply circuit having a circuit section, the second
While the power supply circuit section is operating, the first power supply circuit section is shut off and the second
By supplying an output voltage from the power supply circuit unit to the first power supply circuit unit, the voltage conversion loss corresponding to the power loss of the AVR output transistor of the first power supply circuit unit can be reduced, and the efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a DC power supply device according to an embodiment of the present invention, FIG. 2 is a diagram showing voltage switching timing of the DC power supply device of the present invention, and FIG. 3 is a circuit diagram of a conventional example. 1 ... voltage input terminal, 2 ... AVR output transistor, 3
·································································································· First output terminal
8 Switchgear, 9 Switching transformer, 10 Switching output transistor, 11 Oscillation circuit, 12/18
・ 19… Diode, 14… Second output terminal, 17 ……
Transistor, 20... Third output terminal.

Claims (1)

(57) [Claims] 1. A first power supply circuit section for inputting a DC voltage to an input terminal, forming a constant voltage circuit by a resistor, a constant voltage diode, and a transistor and outputting a DC constant voltage, and a DC power input from the input terminal. A voltage is supplied to a primary winding terminal of a switching transformer via a switch, and is supplied to a primary winding terminal of the switching transformer.The other end of the primary winding terminal of the switching transformer is connected to a base by an oscillation circuit. A second power supply circuit connected to a collector of a switching output transistor to which a driving voltage is supplied and connected to a rectifying / smoothing diode and an electrolytic capacitor at a secondary winding terminal of the switching transformer to output a DC voltage; And a diode connected between a secondary law winding terminal of the switching transformer and an output terminal of the first power supply circuit unit. A voltage obtained by dividing the output voltage of the power supply circuit by a resistor is supplied to the base, and the collector is a switching transistor that is connected to the base of the transistor of the constant voltage circuit of the first power supply circuit and supplies and cuts off the base voltage. When the switch is open, the output voltage of the first power supply circuit is output to an output terminal, and when the switch is closed, the switch circuit is activated to activate the first circuit. A DC power supply device configured to cut off the output voltage of the power supply circuit unit and output the output voltage rectified by the diode from the second power supply circuit unit to the output terminal of the first power supply circuit unit.