JPH0556646A - Power supply - Google Patents

Abstract

PURPOSE:To prepare a DC power unit by using a normal circuit element in place of a power-supply transformer in order to lighten, thin and shorten the DC power unit. CONSTITUTION:AC currents are half-wave rectified by rectifier diodes 2 and 3, and charged to a capacitor 4. The voltage of the capacitor 4 flows through a diode 10 and charges a capacitor 9, and an external circuit is supplied with DC power from the capacitor 9.

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, and more particularly to a device for producing a low voltage DC power supply from a commercial power supply without using a transformer.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional power supply circuit. In the figure, 1 is a power plug, which is a commercial power source (AC10
0 V) and the output terminal of the power plug is connected to the primary side of the power transformer 12. The bridge rectifier diode 13 is connected to the secondary side of the power transformer 12.
A 3-terminal regulator 15 is connected to the output part of the bridge rectifier diode 13, and the 3-terminal regulator 1
Smoothing capacitors 14 and 16 are connected to both ends of 5. The output of the three-terminal regulator 15 is connected to the output terminal 11. AC100V input to power plug 1
The voltage is reduced to a predetermined voltage by the power transformer 12 and rectified by the bridge rectifying diode 13. The rectified DC voltage is stabilized by the three-terminal regulator 15 and supplied as an output power source. Since a power supply transformer is usually used in the step-down circuit required for such a DC power supply device, it is impossible to make the DC power supply device light, thin, short and small because of the power supply transformer.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. In order to reduce the size and weight of the DC power supply device, a normal circuit element is used without using a power transformer. And create a DC power supply.

[0004]

In order to solve the above problems, according to the present invention, the anode of the first diode is connected to one end of the plug, and the cathode of the first diode is connected to the anode of the second diode through the first resistor. Connect the cathode of the second diode to the other end of the plug, connect the cathode of the first diode to one end of the first capacitor, and connect the anode of the Zener diode and the cathode of the third diode to the other end of the first capacitor. Connect, the emitter of the transistor is connected to the anode of the third diode, the collector of the transistor is connected to the other end of the output end, the second capacitor is connected between one end of the output end and the other end, and one end of the output end is connected. The cathode of the fourth diode is connected, the other end of the second resistor is connected to the anode of the fourth diode, the cathode of the Zener diode and the first diode. The anode was connected, there is provided a power supply circuit, characterized in that it connects the base of the transistor to one end of the second resistor.

[0005]

According to the above structure, the alternating current is half-wave rectified by the rectifying diodes 2 and 3 and charged in the capacitor 4.
The voltage of the capacitor 4 flows through the resistor 17 and the diode 10 to charge the capacitor 9, and the capacitor 9 supplies DC power to the external circuit.

[0006]

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a power supply circuit of the present invention. In the figure, reference numeral 1 denotes an AC plug, which is connected to a commercial power source (for example, AC 100 V), one end of an output terminal of the AC plug 1 is connected to an anode of a rectifying diode 2, and the other end of the output terminal is a cathode of a rectifying diode 3. It is connected to the. The cathode of the rectifier diode 2 is connected to the anode of the rectifier diode 3 via the resistor 17. The cathode of the rectifying diode 2 is connected to the emitter of the transistor 7 via the series circuit of the capacitor 4 and the diode 6. The collector of the transistor 7 is the output terminal 11
And the other end of the capacitor 9 and one end of the capacitor 9. The other end of the capacitor 9 is connected to one end of the output terminal 11 and the cathode of the diode 10. The other end of the resistor 8 is connected to the anode of the diode 10 and the anode of the diode 3. One end of the resistor 8 is connected to the base of the transistor 7. The anode of the Zener diode 5 is connected to the cathode of the diode 6, and the cathode is connected to the anode of the rectifying diode 3.

In the above structure, one end of the AC plug 1
When a positive waveform of AC 100 V is applied to point a in the figure, an alternating current flows through the rectifying diode 2, the capacitor 4, the Zener diode 5 and the rectifying diode 3 to charge the capacitor 4. If the capacitance of the capacitor 4 is large, the capacitance through which a large current flows is appropriately selected. AC100 at point a in the figure
When a negative waveform of V is applied, the alternating current is blocked by the rectifying diodes 3 and 2 and does not flow. In this way, half-wave rectification is performed. The voltage charged in the capacitor 4 is applied to the resistor 17, the resistor 8, the base / emitter of the transistor 7 and the diode 6, and a current flows during this period to turn on the transistor 7. When the transistor 7 is turned on, the current charged in the capacitor 4 is transferred to the resistor 17,
It flows through the diode 10, the capacitor 9, the transistor 7, and the diode 6, and charges the capacitor 9. At this time, since the Zener diode 5 is included, the charging voltage of the capacitor 9 will not be charged higher than the Zener voltage. The DC power charged in the capacitor 9 is supplied to the external circuit from the terminal 11. The diode 6 is for preventing overvoltage between the base and emitter of the transistor 7. In this circuit, since no AC current flows between the AC 100V and the terminal 11, no electric shock occurs. That is, at point a in the figure, A
When a positive waveform of C100V is added and the capacitor 4 is charged, a current flows through the Zener diode 5, so that the forward voltage of the Zener diode 5 causes the transistor 7 to be reverse biased and the transistor 7 is turned off. Therefore, no AC voltage appears at the terminal 11. AC at point a in the figure
When a negative waveform of 100 V is applied, no current flows through the diodes 2 and 3, so that no AC voltage appears at the terminal 11.

[0008]

As described above, according to the present invention, since the step-down circuit required for the DC power supply device does not use a power transformer and the circuit is composed of ordinary circuit parts, the DC power supply device can be made compact and lightweight. The effect is great.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a conventional power supply circuit.

[Explanation of symbols]

 1 AC plug 2 Rectifier diode 3 Rectifier diode 4 Capacitor 5 Zener diode 6 Diode 7 Transistor 8 Resistor 9 Capacitor 10 Diode 11 Terminal 12 Power transformer 13 Bridge rectifier diode 14 Smoothing capacitor 15 3-terminal regulator 16 Smoothing capacitor 17 Resistance

Claims (1)

[Claims] 1. An anode of a first diode is connected to one end of a plug, a cathode of the first diode is connected to an anode of a second diode through a first resistor, and a cathode of the second diode is connected to the other end of the plug. Then, connect one end of the first capacitor to the cathode of the first diode, connect the anode of the Zener diode and the cathode of the third diode to the other end of the first capacitor, and connect the emitter of the transistor to the anode of the third diode. , The collector of the transistor is connected to the other end of the output end, the second capacitor is connected between the one end and the other end of the output end, the cathode of the fourth diode is connected to one end of the output end, and the anode of the fourth diode is connected to the other end. Connect the other end of the second resistor, the cathode of the Zener diode and the anode of the first diode, respectively, and connect it to one end of the second resistor. Power supply circuit characterized by connecting the base of the star.