KR0126459Y1 - Circuit for protecting the power supply - Google Patents

Abstract

The present invention relates to a power supply protection circuit for preventing the destruction of the device generated when the secondary side is short-circuited.

To this end, the present invention is connected to the first transistor Q1 outputting a high level voltage when power is input from an external source, and the low level voltage is conducted according to the high level voltage output from the first transistor Q1. A third transistor Q3 that is connected to the second transistor Q2, a low level voltage output from the second transistor Q2, and outputs a high level voltage, and is output from the third transistor Q3. In a power supply circuit composed of a fourth transistor (Q4) connected to a high-level voltage to supply power to each component of a V-C, one end of the collector and the second transistor of the first transistor (Q1). It is connected to the base end of (Q2), the other end is connected to the emitter end of the fourth transistor (Q4), and includes a diode (D1) to control the driving of the second transistor to prevent destruction of the fourth transistor (Q4). Phrase Is, there is an effect that it is possible to prevent destruction of the device.

Description

Power protection circuit

1 is a power circuit diagram supplied to a video cassette recorder.

2 is a power protection circuit diagram according to the present invention.

* Explanation of symbols for main parts of the drawings

10: secondary side of SMPS

The present invention relates to a power supply protection circuit, and more particularly, to a power supply protection circuit for preventing destruction of an element generated when a secondary side of a power supply circuit of a video cassette recorder (hereinafter referred to as VCC) is short-circuited. will be.

In general, the power supply circuit diagram of the V-Cal is the most basic circuit diagram for operating the V-Cal. The device is a device that supplies power required for each part of the V-Cal by converting an AC voltage into a DC voltage.

FIG. 1 is a power supply circuit diagram supplied to each component of the VRC.

The reference numeral 10 shown in the drawing is a power supply device for regularly and stably supplying the power required at the load end, and repeats the ON / OFF operation by using the semiconductor device as a switch element. It is a secondary side of a switching mode power supply (hereinafter referred to as SMPS), which is a power supply method that controls an on / off time ratio to stabilize an output. In addition, the capacitor C1 connected to one end of the SMPS secondary side 10 is a smoothing capacitor that reduces noise generation of the current output from the SMSP secondary side 10.

At this time, when a power key is applied from the outside, a low level voltage is applied to the base terminal of the first transistor Q1 through the P / W ON (L) 21 terminal. Therefore, a high level voltage is applied to the collector terminal of the first transistor Q1 configured of the PNP type, and the voltage applied to the collector terminal of the first transistor Q1 is output to the EVER 6V terminal 20. It is applied to the base end of the second transistor Q2 of the type.

That is, the high level voltage applied from the collector terminal of the first transistor Q1 to the base terminal of the second transistor Q2 conducts the second transistor Q2 so that the collector terminal of the second transistor Q2 has a low level. Voltage will flow.

In this case, the resistor R1 connected to the collector terminal of the first transistor Q1 has a function of limiting the current output from the first transistor Q1 to the EVER 6V terminal 20.

As described above, the low level flowing through the collector terminal of the second transistor Q2 is divided by the resistors R2 and R3, and the voltage divided by the resistors R2 and R3 is the third transistor. It is applied to the base of Q3 to conduct the third transistor Q3.

Therefore, the voltage applied to the base terminal of the third transistor Q3 shorts between the collector terminal and the emitter terminal, and the voltage applied to the base terminal is turned ON / OFF 12V terminal through the collector terminal of the third transistor Q3. It is output to 23 and supplies power to V-Cal components that require ON / OFF 12V.

At this time, the capacitor C2 connected between the resistor R2 and the emitter terminal of the third transistor Q3 has a function of limiting the current flowing through the emitter terminal of the third transistor Q3, and the third transistor Q3. The capacitor C3 connected to the collector terminal of the selector selectively limits the current output from the collector terminal of the third transistor Q3, that is, blocks the DC component of the current output from the collector terminal, and the AC component will be described later. It serves to output to the fourth transistor Q4.

At this time, a high level voltage of 5.6V is applied to the base terminal of the fourth transistor Q4 by a 5.6V zener diode connected to the fourth transistor Q4, so that the fourth transistor Q4 is turned on.

Accordingly, the voltage due to the potential difference between the base terminal and the emitter terminal of the fourth transistor Q4 is output to the ON / OFF 5V terminal 22 through the emitter terminal of the fourth transistor Q4, and requires a V that requires ON / OFF 5V. It is supplied to the components of the seed.

In this case, the integrating circuit formed by the resistor R4 and the capacitor C4 is configured to limit the current flowing rapidly through the base terminal of the fourth transistor Q4, and the capacitor (connected to the emitter terminal of the fourth transistor Q4) C5) has a function to prevent the spark, such as when the current flows rapidly to the ON / OFF 5V (22) occurs.

However, if a short circuit occurs on the secondary side due to incorrect mass production or a defective device, the emitter terminal of the fourth transistor Q4 is grounded, causing a rapid current flow between the collector stage and the emitter stage, or the elements are destroyed or peripheral semiconductor components are destroyed. There was this.

The present invention was devised to solve the above problems, and an object of the present invention is to prevent the destruction of components by controlling the oscillation of the secondary side by using a diode when the secondary side of the power supply is short-circuited. To provide.

The power protection circuit according to the present invention includes a first transistor for outputting a high level voltage when power is input from an external source, and a second transistor for conducting according to a high level voltage output from the first transistor and outputting a low level voltage. A transistor, a third transistor that is connected according to the low level voltage output from the second transistor and outputs a high level voltage, and a fourth transistor that is connected according to the high level voltage output from the third transistor. In the power supply circuit for supplying power to each component of the seed, one end is connected to the collector terminal of the first transistor and the base terminal of the second transistor and the other end is connected to the emitter terminal of the fourth transistor, It comprises a diode that controls the driving to prevent destruction of the fourth transistor (Q4).

Other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

FIG. 2 is a power protection circuit diagram according to the present invention. In the conventional power protection circuit diagram shown in FIG. 1, one end is connected to the collector end of the first transistor and the base end of the second transistor, and the other end thereof is the fourth transistor (Q4). It further comprises a diode (D1) connected to the emitter end of the).

At this time, when the diode D1 does not have a short circuit on the secondary side, that is, when it operates normally, a voltage of about 5.5 V flows by the capacitor C5 connected to the point (B). In addition, since (A) and (C) points are the same voltage source, there is a difference of 6V, so no conduction is made.

However, when a short circuit occurs on the secondary side, a rapid current flows between the collector and the emitter of the fourth transformer Q4 so that the capacitor C5 is destroyed and grounded. Therefore, the point (B) becomes OV and the points (A) and (C) flow 0.6 V, that is, a potential difference of 0.6 V is generated and the diode D1 is conducted.

Therefore, a low level voltage is applied to the base terminal of the second transistor Q2 having the same voltage source as point (A) so that the second transistor Q2 is turned off and interlocked by the second transistor Q2. Transistor Q3 is also turned off.

In addition, since the fourth transistor Q4 interlocked by the third transistor Q3 is also turned off, oscillation of the fourth transistor Q4 is stopped and the fourth transistor Q4 can be prevented from being destroyed.

As described above, the power protection circuit according to the present invention is connected to the collector terminal of the first transistor and the base terminal of the second transistor when the secondary side is short-circuited, and the other end is connected to the emitter terminal of the fourth transistor. Is turned on so that oscillation of the fourth transistor is stopped, thereby preventing the fourth transistor from being destroyed.

While the invention has been shown and described with respect to certain preferred embodiments, those skilled in the art will recognize that various modifications and changes can occur without departing from the spirit and scope of the invention as set forth in the following claims.

Claims (1)

When a power source is input from the outside, the first transistor Q1 outputs a high level voltage and the second transistor conducts according to the high level voltage output from the first transistor Q1 and outputs a low level voltage. Q3), a third transistor Q3 which is connected according to a low level voltage output from the second transistor Q2 and outputs a high level voltage, and a high level output of the third transistor Q3. In a power supply circuit configured to supply power to each component of a V-CAL comprising a fourth transistor Q4 conducted according to a voltage, one end of the collector terminal of the first transistor Q1 and the second transistor Q2 are provided. Diode (D1) connected to the base end of the transistor) and the other end connected to the emitter end of the fourth transistor (Q4) to control the driving of the second transistor to prevent destruction of the fourth transistor (Q4). include Power supply circuit.