KR0142718B1 - Short protect delay circuit of tv - Google Patents

Abstract

The present invention delays the operation of the short protector for a predetermined time by using the short-circuit detection operation control means at the initial time of turning on the power of the television so that the initial power cut-off operation due to the malfunction of the short protector does not occur so that normal power supply is performed. It is to provide a short protection delay circuit of a television set to be performed.

To this end, the present invention provides a short circuit detection unit 10 for detecting whether a short circuit has occurred between any terminals arranged on the main PCB, and controlling the power supply operation in the television set according to a power on / off signal. Power supply control unit 12 for controlling the power supply operation in the television set to be stopped when the short circuit detection signal from the detection unit 10 is input, and for power supply / blocking based on the control signal from the power supply control unit 12. In a television set having a relay driver 14 for activating / deactivating a relay RY, an initial power-on detection unit 20 for detecting an initial state of a power-on signal and a detection signal from the initial power-on detection unit 20 When is input to control the operation of the short-circuit detection unit 10 is not performed while the input time of the power-on signal has passed a predetermined value when the detection signal is not input It consists of a short-circuit detection operation control unit 22 for controlling the operation of the short-circuit detection unit 10, the initial power-on detection unit 20 is connected to the output terminal of the transformer via a resistor (R7) and a diode (D6) as a medium. The short circuit detection operation control unit 22 is configured to output a predetermined short circuit detection operation control signal based on the operation of the initial power supply detection device.

Description

Short Protect Delay Circuits for Televisions

1 is a circuit diagram for explaining a problem of a short protector of a general television;

2 is a short protection delay circuit diagram of a television according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: AC plug 10: Short circuit detection part

12: power drive control unit 14: relay drive unit

16: rectifier 18: main power supply

20: initial power-on detection unit 22: short circuit detection operation control unit

RY: Relay

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short protection delay circuit of a television. More particularly, a short circuit detecting operation control means is used to delay the operation of a short protector for protecting a television set at initial power-on, thereby preventing a malfunction of the short protector. The short protection delay circuit of the present invention.

In general, the power supply required for the receiver ranges from a low voltage of about 12 V to the heater and the entire circuit of the water pipe, to a medium voltage of 500 V and a high voltage of 25 KV. In order to obtain a DC power supply, the flyback pulse of the horizontal deflection circuit is rectified and used in addition to the commercial power supply.

In such a power supply circuit for a television, in particular, although a large change does not occur in an input voltage input to each load or an output voltage output from the load, terminals between loads having different driving voltages are shorted. When a large current flows, internal components are destroyed or become inoperable, so that the protector in the television set is operated.

In addition, the television employs a flyback transformer that operates by a horizontal pulse and a DC voltage to transform and output a high voltage, a focus voltage, a screen voltage, an ABL (Automatic Bright Limiting) voltage, and the like, for example, for driving a CRT.

A CRT anode electrode is connected to the secondary side of the flyback transformer, particularly the CRT high voltage output side, so that the screen display operation of the image signal on the CRT is possible. If the high pressure applied to the CRT anode side rises excessively, a large amount of X-rays are emitted from the CRT screen. For this reason, in consideration of X-ray safety, the voltage level on the CRT anode side is limited to a predetermined range (for example, about 30 kv) or less.

However, if the operating voltage of the flyback transformer is excessively increased due to the resonant capacitor which determines the operation period of the flyback transformer or the contact failure or short circuit of the peripheral circuit element, the high voltage applied to the CRT anode side is also ideally excessive. As it rises, a large amount of X-rays are emitted from the CRT screen, which has a harmful effect on the human body. Thus, an overvoltage cut-off circuit that cuts off the above-mentioned overvoltage is employed in the television set to perform the operation of the protector.

In this general television set, a protector is adopted to protect the television set from short and overvoltage. As an example of such a protector, as shown in FIG. 1, the AC short circuit protector is activated as the relay RY is activated. A rectifying section 16 composed of, for example, a bridge diode for rectifying the commercial power supply (i.e., AC power supply) from the plug 1, and a power supply rectified by the DC component at the rectifying section 16 to each component circuit in the television set. In a television having a main power supply unit 18, a short circuit detection unit 10 for detecting whether a short circuit has occurred between any terminals arranged on a main printed circuit board (PCB), and a power supply unit. When the short detection signal from the short detection unit 10 is input while controlling the power supply operation in the television set in accordance with the on / off signal, A power drive control unit 12 for controlling the power supply operation in the entire set to be stopped, and a relay drive unit 14 for activating / deactivating the relay RY based on a control signal from the power drive control unit 12. do.

The operation of the short protector of the general television configured as described above is as follows.

First, in the normal state in which the power of the television is turned on, the switching transistor Q2 constituting the relay driver 14 is turned on, and the relay RY is activated (self) as the switching transistor Q2 remains turned on. And the commercial power (i.e., AC power) from the AC plug 1 is rectified by the rectifier 16, and then applied to the main power supply 15, from which the main power supply 18 passes to each component circuit in the television set. It provides a predetermined operating power (B ⁺ ).

As described above, when a predetermined portion of the secondary side of the FBT (flyback transformer) is short-circuited during the above-described power supply operation to the television set, the base potential of the switching transistor Q3 constituting the short-circuit detection section 10 is shorted. Since the switching transistor Q3 is turned on, the voltage divided by a predetermined value at the voltage divider R1 and R2 through the emitter and the collector of the switching transistor Q3 is applied to the power drive control unit 12. It is biased to the base of the switching transistor Q1 which constitutes.

Accordingly, since the switching transistor Q2 is turned off as the switching transistor Q1 is turned on, the contact point of the relay RY is opened so that the power supply to the main power supply unit 18 is not performed. will be.

However, although the switching transistors Q1 and Q3 should be cut off at an initial time when the user turns on the television, since the secondary side of the FBT becomes zero (V) instantaneously, the switching transistor Q1 and Q3 are turned on. As the switching transistors Q1 and Q3 are turned on, the switching transistor Q2 is cut off to open the contacts of the relay RY, so that power supply operation into the television set is prevented. There is a case where it is not done, and the user is very embarrassed.

Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to delay the operation of the short protector for a predetermined time by using the short-circuit detection control means at an initial time of turning on the power of the television, resulting in the malfunction of the short protector. It is to provide a short protection delay circuit of a television which prevents the initial power cut operation from occurring so that normal power supply is performed.

In order to achieve the above object, a short protection delay circuit of a television according to the present invention includes a short detection unit that detects whether a short circuit occurs between any terminals arranged on a main PCB, and a television according to a power on / off signal. A power supply control section for controlling the power supply operation in the television set to be stopped when the short circuit detection signal from the short circuit detection section is input while controlling the power supply operation in the set, and the power supply / blocking based on the control signal from the power supply control section. A television set having a relay driver for activating / deactivating a relay for use,

When the initial power-on detection unit for detecting the initial state of the power-on signal and the detection signal from the super non-power-on detection unit is input, the operation of the short-circuit detector is controlled so that the input time of the power-on signal has elapsed. And a short circuit detection operation control section for controlling the short circuit detection section to be operated when the detection signal is not input.

According to a preferred embodiment of the present invention, the initial power-on detection unit comprises an initial power-on detection element connected to the output terminal of the transformer via a resistor and a diode.

The short-circuit detection operation control section is composed of a short-circuit detection operation control element for outputting a predetermined short-circuit detection operation control signal based on the operation of the initial power-on detection element.

The initial power-on detection element and the short-circuit detection operation control element each comprise a switching transistor Q4: Q5.

In addition, the polarities of the switching transistors Q4 and Q5 are opposite to each other.

According to the present invention configured as described above, the initial power-on detection unit applies an initial power-on detection signal to the short-circuit detection operation control unit at an initial time when the user turns on the power of the television, and under the control of the short-circuit detection operation control unit When the power-on state has elapsed for a predetermined time, the initial power-on detection unit does not output the initial power-on detection signal, and the short-circuit detection unit performs the short-circuit detection operation under the control of the short-circuit detection operation control unit. .

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

2 is a short protection delay circuit diagram of a television according to the present invention. The same components as those described in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, the initial power-on detection unit 20 detects an initial time when the user turns on the power of the television. The initial power-on detection unit 20 connects the base to the resistor R7 in the reverse direction. Connected to the output terminal B ⁺ of a transformer (not shown) for outputting a voltage of about 15 V via the diode D6, and the emitter is connected to an operating power supply terminal B ⁺ for outputting a voltage of about 12 V, A PNP type switching transistor Q4 is used for the initial power-on detection element, which is turned on at the initial input of the power-on signal.

The short circuit detection operation control unit 22 controls the short circuit detection operation of the short circuit detection unit 10 not to be performed when the initial power on detection signal is input from the initial power on detection unit 20, while the power on state is predetermined. When the initial power-on detection signal from the initial power-on detection unit 20 is not input in time, the short-circuit detection operation of the short-circuit detection unit 10 is automatically performed.

Here, the short-circuit detection operation control unit 22 has a base connected to the collector of the switching transistor Q4 via the voltage divider resistors RS and R6, and the collector has a predetermined operating power supply terminal B via the resistor R4. ^{+ Is} connected to one side of the collector is connected to the emitter of the switching transistor (Q3) constituting the short-circuit detection unit 10 via a resistor (R8), when the switching transistor (Q4) is turned on and turned on NPN-type switching transistors for short-circuit detection operation control elements that make the switching transistor Q3 cut-off, and when the switching transistor Q4 is cut-off, it is thus cut off to turn the switching transistor Q3 on. Q5).

The operation of the short protection delay circuit of the television according to the present invention configured as described above is as follows.

In FIG. 2, since the output voltage of a transformer (not shown) is set to 0 V instantaneously at the initial time when a user turns on the television, the initial power-on detection unit 20 is constructed. The switching transistor Q4 is turned on. Accordingly, the operating power B ⁺ of about 12 V is divided by the voltage divider resistors R5 and R6 through the emitter and the collector of the switching transistor Q4 to form the short circuit detection operation controller 22. Since the organic transistor is organically biased, the switching transistor Q5 is turned on so that the switching transistor Q3 constituting the short-circuit detecting section 10 is cut off.

Accordingly, the switching transistor Q1 constituting the power drive control section 12 is cut off, and as a result, the switching transistor Q2 constituting the relay drive section 14 is turned on, so that the relay RY is activated (self-holding). Commercial power (i.e., AC power) from the AC plug 1 is rectified in the rectifying section 16, and then applied to the main power supply section 18, and the main power supply section 18 is determined by each component circuit in the television set. It is to provide the operating power of (B ⁺ ).

However, when the power-on state has elapsed for a predetermined time and the output voltage of the transformer is normally output, a voltage of, for example, 0.7 V or more is induced to the base of the switching transistor Q4 through the resistor R7 and the diode D6. The switching transistor Q4, which has been turned on during this time, is cut off. Accordingly, the switching transistor Q5 is also cut off, thereby increasing the emitter potential of the switching transistor Q3.

Therefore, when the emitter potential of the switching transistor Q3 in the cut-off state becomes high, for example, when a predetermined portion of the FBT secondary side is short-circuited, the switching transistor Q3 is switched from the cut-off state to the turned-on state. Transistor Q1 is turned on to cut off switching transistor Q2.

Since the contact point of the relay RY is opened in the state where the switching transistor Q2 is cut off, the power supply to the main power supply unit 18 is not performed.

According to the present invention as described above, when the user turns on the television, the operation of the short protector is not performed, but if a short circuit is detected after a predetermined time has elapsed, the operation of the short protector is automatically performed. In this case, the malfunction of the short protector (that is, the interruption of the power supply) does not occur at the initial power-on.

In addition, this invention is not limited only to the above-mentioned embodiment, It can implement by modifying and modifying within the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the television has been described as an example, but the present invention may be applied to an electric device other than a television with a built-in short protector.

Claims (5)

The short circuit detection unit 10 which detects whether a short circuit has occurred between any terminals arranged on the main PCB, and from the short circuit detection unit 10 while controlling the power supply operation in the television set in accordance with a power on / off signal. The power supply control unit 12 controls the power supply operation in the television set to stop when the short-circuit detection signal is input, and activates the power supply / disconnection relay RY based on the control signal from the power supply control unit 12. In a television set having a relay driver 14 for deactivating / deactivating, an initial power-on detection unit 20 that detects an initial state of a power-on signal, and a short circuit when a detection signal from the initial power-on detection unit 20 is input. While controlling the operation of the detector 10 is not performed, when the input signal of the power-on signal has passed a predetermined value and the detection signal is not input, the short-circuit detector ( 10. A short protection delay circuit for a television, comprising: a short-circuit detection operation control unit 22 for controlling the operation of 10). 2. The short protection delay circuit of claim 1, wherein the initial power-on detection unit 20 comprises an initial power-on detection element connected to the output terminal of the transformer via a resistor R7 and a diode D6. . 3. The short circuit of the television set according to claim 2, wherein the short circuit detection operation control section (22) comprises a short circuit detection operation control element for outputting a predetermined short circuit detection operation control signal based on the operation of the initial power-on detection element. Protect delay circuit. 3. The short protect delay circuit of claim 2, wherein the initial power-on detection element is made of a PNP type switching transistor (Q4). 4. The short protect delay circuit of claim 3, wherein the short detection operation control element comprises an NPN type switching transistor (Q5).