JPH0793688B2 - Television receiver protection circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a protection circuit for a television receiver, and particularly to a high-voltage protection circuit when a video output circuit and / or a vertical output circuit stops operating. The present invention relates to a protection circuit that prevents an abnormal phenomenon that occurs in a receiver.

[Conventional technology]

As shown in FIG. 3, a protection circuit of a conventional television receiver includes a horizontal oscillation circuit 1, a horizontal pre-drive circuit 2, a horizontal drive circuit 3, a horizontal output circuit 4, a flyback transformer (hereinafter abbreviated as FBT) 5 Horizontal deflection circuit 6 consisting of FBT
A high-voltage circuit 7 that rectifies the pulse on the secondary side of 5 and supplies a high voltage to the anode terminal of CRT8, and a CRT8 that outputs an image,
FBT5 the secondary side of the pulse rectification to obtain a DC voltage + B ₁ rectifier circuit 9b and the overcurrent to protect the breakdown of the next-stage circuit by eg fuse 9a and configured by the video output power and protection circuit (hereinafter picture Output power supply) 9), video output circuit 10 that operates with the DC voltage + B ₁ obtained by this circuit as the power supply voltage, and DC voltage + B ₂ by rectifying the secondary side pulse of FBT5
A vertical deflection power supply / protection circuit (hereinafter referred to as vertical deflection power supply) 11 including a rectifier circuit 11b for obtaining
And a vertical output circuit 12 that operates using the DC voltage + B ₂ obtained in this circuit as the power supply voltage, a rectifier circuit 13a that rectifies the pulse on the secondary side of the FBT ₅ to obtain a DC voltage + B ₃ , and resistors R ₄ and R ₅ A high voltage detection circuit 13 composed of a voltage dividing circuit 13b consisting of
Reference voltage generating circuit 14 for generating a reference voltage by a Zener diode (hereinafter abbreviated as ZD) 14a and this reference voltage generating circuit 14
DC voltage rectified by the high voltage detection circuit 13 by the reference voltage of +
PNP transistor TR _{1 that} operates when B ₃ becomes higher
(Hereinafter abbreviated as TR ₁ ) and NPN-type transistor TR ₂ (hereinafter abbreviated as TR ₂ ) and a switch circuit 15 configured as a flip-flop, for example.

Next, the operation will be described. The horizontal oscillating circuit 1 supplies a pulse signal (for example, a 15.75 KHz pulse signal) synchronized with the horizontal synchronizing signal to the horizontal predrive circuit 2. The horizontal predrive circuit 2 has a high input impedance and the horizontal drive circuit 3 amplifies it. It is a preamplifier that amplifies to the extent possible. The horizontal drive circuit 3 is an amplifier that sufficiently amplifies the pulse signal amplified in the previous stage until the horizontal output circuit 4 can operate. Then, the pulse signal sufficiently amplified by the horizontal drive circuit 3 operates the horizontal output circuit 4 and outputs one of the outputs as a sawtooth wave current (for example, 15.75 KHz) to a horizontal deflection coil for horizontally deflecting, The other is output as a flyback pulse to the primary side of FBT5. The FBT 5 boosts the flyback pulse output from the horizontal output circuit 4 to generate a high voltage on the secondary side. The high voltage circuit 7 rectifies this high voltage, converts it into a DC voltage, and supplies it to the anode terminal of the CRT 8. The high voltage generated on the secondary side of the FBT 5 is used as a power supply voltage for each circuit, for example, the video output circuit 10 and the vertical deflection circuit 12. The video protection circuit 9 rectifies the pulse generated on the secondary side of the FBT 5 by the rectification circuit 9b through the fuse 9a to produce a DC voltage + B ₁ and supplies it to the video output circuit 10, and the video output circuit 10 uses this DC voltage. It operates by + B ₁ and outputs a predetermined video signal to CRT8. The vertical deflection power supply circuit 11 rectifies the pulse generated on the secondary side of the FBT 5 by the rectification circuit 11b through the fuse 11a to generate a DC voltage + B ₂ and supplies the DC voltage + B ₂ to the vertical deflection circuit 11. It operates by a DC voltage + B ₂ and outputs a sawtooth wave current (for example, 60 Hz) to a vertical deflection coil that performs vertical deflection. High voltage detection circuit 13
It is to create a DC voltage + B ₃ by rectifying the pulses generated in the secondary side of the FBT5 by the rectifier circuit 13a, a high pressure detection signal when the DC voltage + B ₃ is higher than the reference voltage Vz of the reference voltage generating circuit 14 The HV is output to the base electrode of TR ₂ of the switch circuit 15. TR ₂ is turned on by this signal HV, and TR ₁ is also turned on. The pulse signal output from the horizontal oscillation circuit 1 is grounded via the resistor R ₁ that turns on TR ₁ and TR ₂ . That is, the horizontal predrive circuit 2
Since the input impedance of the very high, it is the pulse signal is grounded via a resistor R ₁ -TR ₁ -TR ₂ -ZD.
Since the switch circuit 15 is configured, for example, like a flip-flop as described above, it keeps the horizontal oscillation circuit stopped when it is turned on once.

More specifically, the conventional high voltage protection circuit 16 will be described in detail. When the power supply voltage + B supplied to the primary side of the FBT5 fluctuates due to a failure of an element of a power supply circuit (not shown) or a fluctuation of the AC input voltage, the voltage is boosted to the secondary. pressure rises abnormally occurring side, thereby increasing the beam current I _B, because the X-ray is in danger to be emitted from a cathode ray tube of CRT 8, the reference of the reference voltage generating circuit 14 provided in the high-voltage protection circuit 16 When the DC voltage + B ₃ rectified by the rectifier circuit 13a becomes higher than the voltage Vz, it is detected that the high voltage is abnormally high, and the high voltage detection signal HV is output to the switch circuit 15, and TR is generated by this signal HV. _The pulse signal output from the horizontal oscillation circuit 1 was cut off because ₂ is turned on and then TR ₁ is also turned on. As a result the horizontal pre-drive circuit 2, a horizontal drive circuit 3, the flyback pulses will not occur because the horizontal output circuit 4 stops the operation, to the secondary side of the FBT5, the beam current I _B since the high voltage is not generated It also had the effect that the emission of X-rays disappeared.

In addition to the high voltage protection circuit 16, a video output power circuit 9
And a vertical deflection power supply circuit 11 are provided. For example, when a circuit element of the video output circuit 10 is short-circuited or the rectifier circuit 9b fails and an overcurrent I flows, a horizontal output circuit and an electronic circuit are provided. The circuit protects the circuit from being destroyed by this overcurrent I. That is, the overcurrent I, fuse 9a is short-circuited by blowing had to stop the operation of the video output circuit 10 to shut down the power supply voltage + B ₁ to the video output circuit 10. Similarly, also the vertical deflection power supply circuit 11 flows through the overcurrent I, the fuse 11a is blown, and cut off the power supply voltage + B ₂ in the vertical deflection circuit 12 becomes short-circuited state, the operation of vertical deflection circuit 12 It was stopped.

[Problems to be Solved by the Invention] However, in the above-described conventional configuration, when the high-voltage protection circuit 16 is not working, that is, the pulse signal output from the horizontal oscillation circuit 1 when the switch circuit 15 is off,
If the video output circuit 10 or the vertical deflection circuit 12 stops operating due to the above-mentioned cause while the subsequent circuits 2, 3 and 4 are operating, for example, in the case of the video output circuit 10, the brightness becomes abnormal. As the upstream beam current I _B increases, there is a risk that X-rays will be emitted from the cathode ray tube of the CRT 8 and the induced current due to the excessive beam current I _B will flow to the primary side of the FBT 5 and destroy the horizontal output circuit 4. Had.

Further, in the case of the vertical deflection circuit 12, since vertical deflection cannot be performed, there is also a problem that a horizontal white line is generated on the screen of the CRT 8 and the fluorescent surface is burned out.

[Means for solving problems]

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to control the switch circuit of the high voltage protection circuit when the operation of the video output circuit or the vertical deflection circuit is stopped and to control the horizontal level. It is an object of the present invention to provide a protection circuit for a television receiver that stops the operation of the deflection circuit.

In order to achieve this object, the present invention provides a power supply detection circuit for detecting that a DC voltage supplied to a video output circuit and / or a vertical deflection circuit has risen in a protection circuit of a television receiver, and A second switch circuit for controlling the protection circuit of the television receiver to operate in accordance with the power detection signal output from the power detection circuit.

[Action]

According to the present invention, even if the high voltage protection circuit is not operating, if the operation of the video output circuit and / or the vertical deflection circuit is stopped, the high voltage protection circuit is controlled to operate by detecting this, and the receiver is operated. The abnormal phenomenon of is prevented.

〔Example〕

FIG. 1 shows an electric block diagram of the present invention, and FIG. 2 shows an electric circuit. An embodiment of the present invention will be described below with reference to FIG. The same parts as those in the conventional example are designated by the same reference numerals, the description thereof will be omitted, and only new parts will be described in detail.

In the protection circuit of the conventional television receiver, the pulse voltage generated on the secondary side of the flyback transformer (hereinafter abbreviated as FBT) 5 of the horizontal deflection circuit 6 is rectified by the rectification circuits 9b and 11b, and the DC voltage + B ₁ , Supply + B ₂ and stop the supply operation by detecting the flow of overcurrent more than a predetermined value. For example, a power supply circuit and a protection circuit for video output (hereinafter abbreviated as power supply for video output) 9 and a power supply and protection circuit for vertical deflection (hereinafter abbreviated as power supply for vertical deflection) 11 which are power supply circuits including fuses 9a and 11a Upon receiving the power supply detection circuit 17 that receives the output and the output signal of this circuit 17, that is, the power supply detection signal A,
A second switch circuit 18 which operates to control the first switch circuit 15 is newly provided.

Next, the operation will be described.

When the high voltage protection circuit 16 is not working, that is, when there is no abnormal high voltage rise and the video output circuit 10 and vertical deflection circuit 12 are operating normally, the resistance of the base electrode of TR ₅ of the power supply detection circuit 17 is a resistance. DC voltage + B ₁ is applied via R ₁₀ and becomes “H” level to turn on, and TR ₆ also has resistance R on the base electrode.
_The DC voltage + B ₂ is applied via ₁₁ and it goes to the “H” level and turned on. Therefore, the power supply voltage + B is equal to the resistance R ₉ −.
It is grounded through a TR ₅ -TR _6. As a result, the power supply detection signal A output from the collector electrode of TR ₅ becomes “L” level, and the NPN transistor TR ₄ (hereinafter abbreviated as TR ₄ ) of the second switch circuit 18 passes through the resistor R ₈ . Join the base electrode,
TR ₄ is turned off. When TR ₄ is in the OFF state, the power supply voltage + B is the resistance R ₄ NPN-type transistor TR ₃ via (hereinafter TR
Since it is added to the base electrode (abbreviated as ₃ ), it becomes the “H” level and is turned on. When TR ₃ is in the ON state, the base electrode of the NPN transistor TR ₂ (hereinafter abbreviated as TR ₂ ) of the first switch circuit 15 is grounded via the resistor R ₅ of the voltage dividing circuit 13b.
That is, since it becomes the "L" level, it is turned off, and the PNP transistor TR ₁ (hereinafter abbreviated as TR ₁ ) is also turned off. Therefore, the horizontal deflection circuit 6 continues its operation without stopping.

Next, when the circuit element of the video output circuit 10 is short-circuited or the like, an overcurrent flows, and when the fuse 9a provided in the video output power supply 9 is blown, the DC voltage + B ₁ disappears and the video output circuit 10 operates. To stop. Then, the base electrode of TR ₅ of the power supply detection circuit 17 becomes "L" level, and TR ₅
Turns off. Then, the power supply detection signal A output from the collector electrode of TR ₅ becomes "H" level and is applied to the base electrode of TR ₄ of the second switch circuit 18 via the resistor R ₈ . TR ₄ is turned on by this “H” level, and TR ₃ is turned off this time. When TR ₃ is turned off, the potential at the connection point between the resistor R ₄ and the resistor R ₅ of the voltage dividing circuit 13b rises, and when this potential becomes higher than the reference voltage Vz set by the reference voltage generating circuit 14, the first voltage TR _{2 of the} switch circuit 15 is turned on, and accordingly, TR ₁ is also turned on. Therefore, the pulse signal output from the horizontal oscillator circuit 1 is grounded via the resistors R ₁ -TR ₁ -TR _2, and as a result,
The operation of the horizontal deflection circuit 6 is stopped. Since the first switch circuit 15 is configured, for example, like a flip-flop, it keeps the ON state unless the power supply to the horizontal oscillation circuit 1 is cut off.

In addition, the fuse 11a provided in the vertical deflection power supply 11
However, when the fuse is blown by an overcurrent, the base electrode of TR ₆ of the power supply detection circuit 17 becomes the “L” level and TR ₆ is turned off, as in the case of the video output power supply 9 described above. Therefore, the power supply detection signal A output from the power supply detection circuit 17 becomes "H" level, and TR _{4 of} the second switch circuit 18 is
To the resistor via resistor R ₈ and TR ₄ is turned on. Therefore, the resistance R ₄ and the resistance R _{4 of the} voltage dividing circuit 13b of the high voltage detection circuit 13 are
The potential at the connection point of ₅ rises, and TR _{2 of} the first switch circuit 15 is turned on. As a result, the horizontal deflection circuit 6 stops operating. In this case as well, the ON state is maintained unless the power supply to the horizontal oscillation circuit 1 is cut off, as described above.

In the embodiment, the power supply voltage of the video output circuit 10 is configured to be obtained from the secondary side of the FBT5 via the video output power supply 9, but it is not always necessary to take it from the primary side of the FBT5. , It may be configured to be obtained from a commercial power source, for example. In this case, it goes without saying that the same operation as that of the present invention is performed.

〔effect〕

As described above, according to the present invention, the high voltage protection circuit operates not only when the high voltage is detected, but also when the operation of the video output circuit and / or the vertical deflection circuit is stopped. Since it is configured, it is possible to prevent the destruction of the horizontal output circuit due to the overcurrent due to the stop of the operation of the video output circuit and the burning of the fluorescent surface due to the stop of the operation of the vertical deflection circuit, which have been the conventional problems. The safety and reliability are significantly improved.

[Brief description of drawings]

FIG. 1 is an electric block diagram of the present invention, FIG. 2 is an electric circuit diagram of the present invention, and FIG. 3 is an electric block diagram of a conventional example. 6 ... Horizontal deflection circuit, 9 ... Video output power / protection circuit, 10 ... Video output circuit, 11 ... Vertical deflection power / protection circuit, 12 ... Vertical deflection circuit, 16 ... High voltage protection circuit, 17 ...
… Power supply detection circuit, 18 …… Second switch circuit.

Claims (1)

[Claims] 1. A horizontal deflection circuit for deflecting an electron beam of a picture tube in a horizontal direction, and a flyback pulse generated in the horizontal deflection circuit is boosted by a flyback transformer connected to the horizontal deflection circuit, rectified to a high voltage. A high voltage generation circuit for generating and supplying the cathode electrode to the cathode or grid of the picture tube, and a video output circuit for modulating the beam current of the picture tube with the video signal, And a vertical deflection circuit for vertically deflecting the electron beam, and when the high voltage generated in the high voltage generation circuit is detected to be equal to or higher than a predetermined value, control is performed to stop the operation of the horizontal deflection circuit. A high voltage protection circuit having a first switch circuit and a DC voltage necessary for operating the video output circuit and / or the vertical deflection circuit are supplied to a commercial power source or A power supply circuit having an overcurrent prevention means for rectifying and smoothing the pulse voltage generated in the flat deflection circuit and supplying the pulse voltage, and detecting the flow of an overcurrent of a predetermined value or more to stop the supply operation. In a protection circuit of a television receiver, a power supply detection circuit that outputs a power supply detection signal by detecting that the direct current voltage from the power supply circuit has been cut off by the operation of the overcurrent prevention means, and a circuit output from this circuit. A protection circuit for a television receiver, comprising: a second switch circuit that controls the first switch circuit according to the detection signal.