JPS6213128Y2 - - Google Patents

Description

[Detailed description of the invention] This invention provides stable power supply by simply adding an extremely simple additional circuit to the stabilized collector output type power supply circuit used in the DC power supply circuit of electronic equipment such as television receivers. It is an object of the present invention to provide an improved method for utilizing a power control transistor as a power switch.

FIG. 1 shows a conventional example. Here, 1 is a power input terminal, 2 is a constant voltage power supply output terminal, and 3 to 13 are
are elements constituting a generally well-known stabilized power supply circuit; 3 is a constant voltage control transistor;
4 is a drive transistor, 5 is a comparison amplification transistor, 6 is a Zener diode that provides a reference voltage,
7 is a resistor that provides the operating current of the Zener diode 6; 8, 9, and 10 are resistors that detect the output voltage; the movable terminal of the variable resistor 9 is connected to the base of the comparison amplification transistor 5; is compared with the reference voltage of In addition, 11 is a resistor that provides the operating current of the comparison amplification transistor 5, 12 is a collector load resistance of the drive transistor 4, and 1
3 is a starting resistance.

Reference numeral 14 denotes a power off switch, which short-circuits the base and emitter of the control transistor 3 of the stabilized power supply circuit to cut off the transistor 3 and operate it as a power switch.

In this case, the resistor 13 is a starting resistor as described above, and it is necessary to generate a voltage at the terminal 2 sufficient to make the comparison amplification transistor 5 conductive when the switch 14 is opened. It cannot take a value that is too large for the load. Therefore, even when the power is off, current flows through this resistor 13, which is not preferable in the case of a battery power source. As an example, in a television receiver with a stabilized output voltage of 11.5V, the starting resistor 10 is 1.2K.
A value of Ω is required, and a current of approximately 10 mA will flow even when the switch is off.

The present invention eliminates the above-mentioned conventional drawbacks.

FIG. 2 shows an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same numbers. To explain the newly added parts, 15 is a charging capacitor for starting, 16 is a charging resistor for starting, 17 is a discharging resistor for capacitor 15, and 18 is a base/emitter of constant voltage control transistor 3 and drive transistor 4. This is a diode for reverse voltage protection.
Further, 19 is a switch for switching charging/discharging of the capacitor 15, and is interlocked with the power off switch 14. Note that in FIG. 2, the starting resistor 13 is removed.

The operation of this circuit will be explained. Now, when switches 14 and 19 are changed from closed to open, capacitor 1
5. The charging current through the resistor 16 flows to the base of the transistor 4, and the current amplified by the transistor 4 and the transistor 3 flows from the power supply input terminal 1 to the power supply load. At this time, if a current equivalent to that flowing through the resistor 13 in FIG. 1 flows, startup will be performed, and the resistor 1
You can choose a larger value for 6.

To turn off the power, press switches 14 and 1.
When 9 is closed, the bases and emitters of transistors 3 and 4 are short-circuited, thereby cutting off these transistors.

At this time, the capacitor 15 is discharged through the resistor 17 to prepare for the next power-on operation. The current flowing in this state is that the value of the resistor 16 is greater than the value of the starting resistor 13 in the conventional example shown in FIG.
The value can be increased by more than 100 times, so under the same usage conditions as in the example above, the current flowing when the power is off is 100
It is less than μA, and poses almost no problem in practice.

Furthermore, in the circuit of the present invention, when the power supply load is short-circuited, transistor 3 is momentarily cut off and does not conduct until the power switch is turned off and then on again, so it can be used as a circuit breaker for short-circuit protection. It also has the function of

As described above, according to the present invention, it is possible to provide a simple and highly practical power switch circuit that can suppress the current to an extremely low level when the power is turned off. In the above embodiment, a case was explained in which a drive transistor was inserted between the constant voltage control transistor and the comparison amplification transistor, but even if this drive transistor is not provided, the effect will be slightly reduced, but the first
An effective power switchgear can be provided compared to the figure.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional power switching device, and FIG. 2 is a circuit diagram of a power switching device according to an embodiment of the present invention. 1...Power input terminal, 2...Constant voltage power supply output terminal,
3... Constant voltage control transistor, 4... Drive transistor, 5... Comparison amplification transistor, 6...
Zener diode, 15...Capacitor, 1
6,17...Resistance, 14,19...Switch.

Claims (1)

[Claims for Utility Model Registration] (1) A constant voltage control transistor whose emitter is connected to an unregulated DC power supply and which takes out a constant voltage DC output from its collector, and whose collector is connected to the base of the transistor. A comparison amplification transistor for controlling a constant voltage control transistor, and a reference voltage element connected to the emitter of the comparison amplification transistor, and a capacitor and a resistor connected between the base of the constant voltage control transistor and the reference potential. 1. A power supply switching device, characterized in that a switch is provided to connect a series circuit and to short-circuit both ends of the capacitor and between the emitter and base of the constant voltage control transistor. (2) Provide a drive transistor whose emitter is connected to the base of the constant voltage control transistor and whose base is connected to the collector of the comparison amplification transistor, and connect a series circuit of a capacitor and a resistor between the base of this drive transistor and the reference potential. The power supply switching device according to claim 1, further comprising a switch for short-circuiting both ends of the capacitor, the emitter of the constant voltage control transistor, and the base of the drive transistor in conjunction with each other.