JP2001327159A - Switching power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power circuit for drive of an on/off photocoupler which can be constituted of small and light-weight parts. SOLUTION: In a switching power source in which a photocoupler is connected between a switching control circuit for driving a primary switching element and a secondary switch, and which supplies load with DC output voltage being obtained by applying the voltage obtained by rectification and smoothing to the primary winding of a converter transformer by the above switching means, and rectifying and smoothing it by a secondary first diode and a first smoothing capacitor, a circuit for connecting a second diode, a first resistor, and a second smoothing capacitor with one another, and a first smoothing capacitor are connected in parallel between the cathode of the secondary first diode and the cathode of the diode of the photocoupler, and further a circuit for connecting a battery, a second resistor, and a third diode with one another, and a second smoothing capacitor are connected in parallel between the cathode of the diode of the above photocoupler and the secondary switch, thus a power circuit for drive of a photocoupler is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for driving a photocoupler on the secondary side, which uses a battery to perform on / off control of a switching power supply from a secondary side switch. The main components are smaller and lighter.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional switching power supply circuit in which a DC output voltage is turned on / off by a secondary switch 17.
When turned off, the power circuit 18 for driving the photocoupler is turned off.
Flows a current through the photodiode of the photocoupler 15 with the DC voltage V ₃ rectified and smoothed by the rectifier diode 26 and the smoothing capacitor 27 from the commercial transformer 25,
Although operated, the commercial transformer 25 has a problem that it is heavy and there is a limit to downsizing.

[0003]

As described above, in the conventional switching power supply, there is a problem that the commercial transformer 25, which is a main component to be used, is heavy and there is a limit to downsizing. There has been a demand for a photocoupler driving power supply circuit that can be reduced in size and weight without using 25.

[0004]

SUMMARY OF THE INVENTION The present invention has solved the above-mentioned problem, and has a photodetector between a switching control circuit for driving a primary-side switching element 5 and a secondary-side switch 17 and a resistor 16. Connect coupler 15 and rectify
The voltage obtained by smoothing is applied from the switching element 5 to the primary winding 4 of the converter transformer 11, and rectified and smoothed by the first diode 12 and the first smoothing capacitor 13 on the secondary side. In the switching power supply that supplies the DC output voltage to the load, the second diode 24 and the first resistor 2 are connected between the cathode of the first diode 12 on the secondary side and the cathode of the diode of the photocoupler 15.
3 and a second smoothing capacitor 22 in series, a first smoothing capacitor is connected in parallel, and the cathode of the photocoupler diode and the secondary switch 1 are connected.
7, a circuit for connecting a battery 19, a second resistor 20, and a third diode 21 in series, and a second smoothing capacitor 22 are connected in parallel to form a photocoupler driving power supply circuit. A switching power supply characterized in that: Further, the switching power supply is characterized in that the terminal voltage V ₁ of the second smoothing capacitor 22 is set higher than the terminal voltage V ₂ of the battery 19.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a second diode 24, a first resistor 23 and a second resistor 24 are provided between the cathode of a first diode 12 on the secondary side and the cathode of a diode of a photocoupler 15. A circuit for connecting the second smoothing capacitor 22 in series and the first smoothing capacitor are connected in parallel.
A circuit for connecting a battery 19, a second resistor 20, and a third diode 21 in series, and a second smoothing capacitor 22 are connected in parallel between the cathode of the photocoupler diode and the secondary switch 17. I do. Here, the photocoupler 15 connected to the primary-side switching control circuit 6 has a function of outputting the DC voltage Vo when the phototransistor is turned on, and stopping the output of the DC voltage Vo when the phototransistor is turned off. Therefore, when the secondary switch 17 is turned on, a current flows from the series circuit including the capacitor 22, the battery 19 connected in parallel to both ends of the capacitor 22, the second resistor 20, and the third diode 21 to the photodiode through the resistor 16. Flows, and the phototransistor is turned on, so that the switching control circuit operates and outputs the DC voltage Vo.
The second diode 24 and the resistor 2 are connected by the DC voltage Vo.
A current is supplied to the photodiode via the switch 17 and the resistor 16 through 3. At this time, the capacitor 2
2 of the terminal voltages V ₁ by setting to be higher than the terminal voltage V ₂ of the battery 19, the current flowing from the battery 19 0A
Thus, the consumption of the battery 19 can be reduced, and the photocoupler driving power supply circuit 18 can be configured using small and lightweight components (batteries). With the configuration described above, it is not necessary to separately provide a heavy commercial transformer, and a photocoupler driving power supply circuit that can be reduced in size and weight can be realized.

[0006]

FIG. 1 shows a basic circuit of an embodiment of the present invention.
FIG. 2 shows a conventional circuit. Here, a button-type small battery was used as the battery 19 in FIG. Table 1 shows a comparison between the weights of the main parts of the power circuit for driving the photocoupler in the circuits shown in FIGS.
The following weight was able to be reduced.

[0007]

[Table 1]

[0008]

The photocoupler driving circuit is constructed as in the present invention, and by using a button-type small battery as the battery 19, a photocoupler driving power supply circuit comprising a commercial transformer of the conventional circuit of FIG. It is possible to realize a reduction in size and weight as compared with. When the DC output voltage Vo is being output, the current flowing out of the battery 19 is almost 0 A.
Thus, battery consumption can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a conventional switching power supply circuit diagram.

[Explanation of symbols]

 Reference Signs List 1 AC power input 2 Full-wave rectifier diode 3, 7 Smoothing capacitor 4 Primary winding of converter transformer 5 Switching element 6 Switching control circuit 8 Diode 9 Auxiliary winding of converter transformer 10 Secondary winding of converter transformer 11 Converter transformer 12 1st diode 13 1st smoothing capacitor 14 load resistance 15 photocoupler 16 resistor 17 secondary switch 18 photocoupler drive power supply circuit 19 battery 20 second resistor 21 third diode 22 second smoothing capacitor 23 1 resistor 24 2nd diode

Claims (2)

[Claims] 1. A photocoupler is connected between a switching control circuit for driving a primary-side switching element and a secondary-side switch, and a voltage obtained by rectification and smoothing is converted by the switching element into a converter transformer. A switching power supply for applying a DC output voltage obtained by rectifying and smoothing the voltage to a secondary winding and rectifying and smoothing the rectified and smoothed voltage with a first diode on the secondary side and a first smoothing capacitor to a load; And a circuit for connecting a second diode, a first resistor, and a second smoothing capacitor in series, and a first smoothing capacitor are connected in parallel between the cathode of the photocoupler and the cathode of the diode of the photocoupler. A circuit for connecting a battery, a second resistor, and a third diode in series between the cathode of the photocoupler diode and the secondary switch; and a second smoothing capacitor. Switching power supply connected in parallel and support, characterized in that to constitute a power circuit for driving the photocoupler. 2. The switching power supply according to claim 1, wherein the terminal voltage of the second smoothing capacitor is set higher than the terminal voltage of the battery.