JPH031894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a power supply device that does not use a power transformer, and its aim is to improve the efficiency of the power supply device and stabilize the output voltage.

A conventional transformerless power supply device that does not use a power transformer has a relatively simple structure including a rectifier diode, a dropper resistor, and the like. An example of this is explained using Fig. 1. 1 and 2 are AC input terminals such as commercial power supply, 3 is a rectifier diode,
4 is a dropper resistor, 5 is a smoothing capacitor, 6,
7 is a DC output terminal, and 8 is a load. Conventional transformerless power supplies having such a configuration have the following drawbacks. In other words, the load voltage tends to change due to changes in the AC input voltage or load impedance, and to prevent this, it is necessary to stabilize the voltage using a voltage stabilization circuit after smoothing with the capacitor 5, or to stabilize the voltage by using a voltage stabilization circuit after smoothing with the capacitor 5. Accordingly, the heat generated by the dropper resistor 4 increases, resulting in various drawbacks such as the need for a large heat dissipation device.

The present invention eliminates such conventional drawbacks, and one embodiment thereof will be described below with reference to FIG. 2. In the figure, 11 and 12 are AC input terminals such as commercial power supply, 13 is a rectifier thyristor, and 1
4 is a current limiting resistor, 15 is a smoothing capacitor, 1
6 is the load, 17, 20 is the diode, 18, 2
2 and 24 are resistors, 19 is a Zener diode, 2
1 is a capacitor, 23 is a transistor, 25, 2
6 is a DC output terminal.

Here, the rectifying thyristor 13 and the smoothing capacitor 15 are connected in series, and are connected to the AC input terminal 1 through the current limiting resistor 14.
It is connected between 1 and 12. Further, the load 16 is connected to both ends of the smoothing capacitor 15, and the DC output terminals 25, 26 at both ends of the smoothing capacitor 15 are connected to each other.
It is configured to extract output from .

The transistor 23 is a rectifying thyristor 1
It is connected between the gate G and cathode K of No. 3.
Further, a resistor 24 is connected between the collector and emitter of the transistor 23.

Further, a diode 17, a resistor 18, a Zener diode 19, and a diode 20 are connected in series between the AC input terminals 11 and 12. The Zener diode 19 is connected between the collector and base of the transistor 23 via a resistor 22, and when the voltage exceeds a certain voltage determined by the constant voltage detection element of the Zener diode 19, base current flows to the transistor 23 and conducts. I will do it.

In addition, a transistor 2 is connected across the Zener diode 19 when the AC input voltage is rising.
3 is connected to a capacitor 21 for flowing a base current.

The operation of the above embodiment will now be explained. When the AC input voltage is rising (A in Figure 3)
), a base current flows from the diode 17 and resistor 18 to the transistor 23 through the capacitor 21, and the AC input voltage is a constant voltage E determined by the Zener diode 19, resistors 18, 22, etc.
In the above case, the base current flows from the diode 17 and the resistor 18 to the transistor 3 through the Zener diode 19, and in either case, the base current flows to the transistor 23.
conducts, and the gate G and cathode K of the rectifying thyristor 13 become short-circuited, and the thyristor 13
remains off.

On the other hand, when the input AC voltage is decreasing (portion B in Figure 3), the AC input voltage is at the constant voltage E.
When the base current of the transistor 23 stops flowing, the transistor 23 turns off.
At that time, a certain amount of charge that has been charged in the capacitor 21 passes through the resistor 22 to the thyristor 1.
3 gate signal, the thyristor 13 becomes conductive,
In other words, turn on.

Since the input AC voltage is an alternating voltage whose voltage rises and falls repeatedly, the thyristor 13 also continuously repeats non-conduction and conduction accordingly.
The capacitor 15 is charged by being supplied with the voltage indicated by the shaded area c in FIG. 3 only when the thyristor 13 is conductive, and a substantially constant voltage is supplied to the load 16. The voltage E at which the thyristor 13 conducts can be set arbitrarily, and thereby the output voltage can also be arbitrarily selected.

As explained above, in the power supply device of the present invention, the turn-on voltage of the thyristor is determined by the constant voltage detection circuit and can be set arbitrarily, so that changes in the output voltage with respect to changes in the input AC voltage can be reduced. Also, the turn-on voltage of the thyristor,
In other words, by setting the output peak voltage to a value close to the output voltage, the current limiting resistor generates less heat and improves efficiency, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional transformerless power supply device, FIG. 2 is a circuit diagram of a transformerless power supply device according to an embodiment of the present invention, and FIG. 3 is a waveform diagram illustrating the operation of the same device. 11, 12... AC input terminal, 13... Thyristor, 14, 18, 22, 24... Resistor, 15...
...Smoothing capacitor, 16...Load, 17, 20...
...Diode, 19... Zener diode, 2
1...Capacitor, 23...Transistor, 2
5, 26...DC output terminal.

Claims (1)

[Claims] 1. A power supply device configured such that at least a smoothing capacitor and a thyristor are connected in series between AC input terminals, and output is taken from both ends of the capacitor, and a transistor is connected between the gate and cathode of the thyristor. , and a constant voltage detection element that causes a base current to flow through the transistor to make it conductive when the AC input voltage is equal to or higher than a predetermined value, and a capacitor that causes a base current to flow through the transistor to make it conductive when the AC input voltage rises, A power supply device characterized in that the thyristor is made conductive only when the voltage drops below a predetermined value.