JPH0215419Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to horizontal deflection circuits for television receivers, etc., and in particular protects horizontal deflection circuits in which the oscillation voltage of the horizontal oscillation circuit is applied separately to the horizontal output circuit and the high voltage output circuit. Regarding circuits.

In television receivers and the like, high pressure is supplied to the anode of the picture tube, but this high pressure may rise abnormally, and in this case there is a risk of emitting X-rays that are harmful to the human body. For this reason, a high voltage stop circuit is generally provided which stops the operation of the high voltage output circuit when the high voltage rise reaches a certain value. FIG. 1 is a circuit diagram of a high voltage stop circuit and its peripheral circuits in a horizontal deflection circuit configured such that the oscillation voltage of the horizontal oscillation circuit is applied to the horizontal output circuit and the high voltage output circuit separately. 1 is a horizontal oscillation circuit, 2 is a horizontal drive circuit, 3 is a horizontal output circuit, 4 is a horizontal deflection coil,
5 is a high voltage output circuit, 6 is a flyback transformer,
7 is a high voltage rectifier unit, and 8 is a picture tube. Reference numeral 9 denotes a high voltage stop circuit which detects a flyback pulse voltage which is a secondary voltage of the flyback transformer 6, and turns on to cut off the B voltage of the horizontal oscillation circuit 1 if the detected voltage is larger than the reference voltage. In a horizontal deflection circuit that has such a high-voltage stop circuit and has a configuration in which the oscillation voltage of the horizontal oscillation circuit is applied to the horizontal output circuit and the high-voltage output circuit separately, when the high-voltage stop circuit operates, the high-voltage output circuit and the horizontal output circuit are almost simultaneously turned off, and depending on the timing, the horizontal output circuit turns off first. As a result, the screen becomes vertically aligned for a moment, and the electron beams concentrate there, potentially burning out the phosphor of the picture tube.

The object of the present invention is to provide a horizontal deflection circuit that eliminates such drawbacks.

The present invention will be explained below with reference to the drawings.
FIG. 2 is a circuit diagram of a horizontal deflection circuit and its peripheral circuits according to an embodiment of the present invention. Each circuit numbered 1 to 8 is the same as the circuit with the same number in FIG. 10 is a high voltage detection circuit. +B ₁ is the main high voltage stop circuit 10
11 is the reference voltage power supply that operates, and 11 compares the high voltage detected by the high voltage detection circuit with the reference voltage of the power supply + _B1 ,
This is a comparator that outputs a high level signal when the former is larger than the latter. D is a diode provided between the output terminal and the non-inverting input terminal of the comparator 11, and _R2 is a resistor to prevent feedback from being applied to the comparator 11 by the diode D when the output of the high voltage detection circuit 10 is at a low level. It is. 12 is an inverter circuit. TR ₁ is a switching transistor,
R ₁ and +B ₂ are the current limiting resistor and power supply of the transistor TR ₁ , respectively. R ₃ and C ₁ are a resistor and a capacitor that constitute a time constant circuit, respectively. 13 and 1
4 is a comparator, +B ₃ and +B ₄ are the comparison reference voltages of comparators 13 and 14, respectively, and the power supply of V ₁ and V ₂ is set so that V ₁ < V ₂ < V ₃ (V ₃ is the voltage of the power supply +B ₂ ) be done. TR ₂ and TR ₃ are switching transistors, and R ₄ and R ₅ are current limiting resistors of transistors TR ₂ and TR ₃ , respectively.

R ₆ and R ₇ are horizontal output circuit 3 and high voltage output circuit 5 when transistors TR ₂ and TR ₃ are turned on, respectively.
This is a resistance to prevent both from falling to the ground level.

Next, the operation of the protection circuit for the horizontal deflection circuit according to an example of the present invention having the above configuration will be explained. FIG. 3 is a diagram showing temporal changes in the terminal voltage of the capacitor _C1 (potential at point A) of the time constant circuit. When the flyback pulse voltage of the flyback transformer 6 detected by the high voltage detection circuit 10 is smaller than the reference voltage at which the high voltage stop circuit operates, the comparator 11 outputs a low level signal.
This low level signal is inverted by the inverter circuit 12 and becomes high level, and the transistor _TR1 is turned on. Therefore, the terminal voltage of capacitor _C1 is zero. This allows comparator 1
3 and 14 are both at low level, transistors TR ₂ and TR ₃ are both off, and the oscillation voltage of the horizontal oscillation circuit 1 is amplified by the horizontal drive circuit 2 and then sent to the horizontal output circuit 4 and the high voltage output circuit. 5 separately. Next, at time _t0 , when the input voltage of the flyback pulse voltage from the high voltage detection circuit 10 becomes larger than the comparison reference voltage of the comparator 11, it is determined that an abnormal high voltage has occurred, and the output of the comparator 11 changes from the low level. The signal becomes high level, passes through the inverter circuit 12, is inverted to low level, and turns off the transistor _TR1 . In addition, capacitor C ₁ connects the voltage of power supply +B ₂ through resistor R ₃ .
The capacitor C1 is charged by _V3 , and at this time the terminal voltage of the capacitor _C1 rises along the charging curve shown in FIG. When the charging time exceeds _t1 , the terminal voltage of capacitor _C1 becomes the comparison reference voltage _V1 of comparator 13.
The output of the comparator 13 becomes high level, and the transistor TR ₂ is turned on. Therefore, the potential between the horizontal drive circuit 2 and the high voltage output circuit 5 becomes zero, and the supply of oscillation voltage from the horizontal drive circuit 2 to the high voltage output circuit 5 is cut off.
Next, when time exceeds _t2 , the terminal voltage of the capacitor _C1 becomes higher than the comparison reference voltage _V2 of the comparator 14, the output of the comparator 14 becomes high level, and the transistor _TR3 is turned on. Therefore, the potential between the horizontal drive circuit 2 and the horizontal output circuit 3 becomes zero, and the supply of oscillation voltage from the horizontal drive circuit 2 to the horizontal output circuit 3 is cut off. That is,
When the charging time of the capacitor _C1 exceeds _t1 , the high voltage output circuit 5 first stops, and when it exceeds _t2 , the horizontal output circuit 3 stops. And from now on, transistor TR ₁
remains off until the power is turned off.

As explained above, the present invention provides a switching circuit between the horizontal drive circuit and the horizontal output circuit, the horizontal drive circuit and the high voltage output circuit, and
When the high voltage detection circuit detects abnormally high voltage, the switching circuit of the high voltage output circuit is turned on before the switching circuit of the horizontal output circuit, and the high voltage output circuit is stopped before the horizontal output circuit. It has the effect of reliably protecting the

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional high voltage stop circuit and its peripheral circuits in a horizontal deflection circuit configured such that the oscillation voltage of the horizontal oscillation circuit is supplied to the horizontal output circuit and the high voltage output circuit separately, and Figure 2 is a circuit diagram of the conventional high voltage stop circuit and its peripheral circuits. FIG. 3 is a circuit diagram of a circuit according to an embodiment and its peripheral circuits, and is a diagram showing a temporal change in the terminal voltage of capacitor C ₁ in FIG. 2. DESCRIPTION OF SYMBOLS 10... High voltage detection circuit, 11... Control voltage generation means, _TR1 , + _B2 , _R3 , _C1 ... Voltage generation circuit, 13,
+B ₃ , TR ₂ ...first switching circuit, 14, +
B ₄ , TR ₃ ... second switching circuit.

Claims (1)

[Claims for Utility Model Registration] A horizontal drive circuit that amplifies the oscillation voltage of a horizontal oscillation circuit, a horizontal output circuit that supplies a deflection current to a horizontal deflection coil, and a high-voltage output circuit that generates a high voltage that is supplied to the anode of a picture tube. In the horizontal deflection circuit configured to apply the amplified oscillation voltage to the horizontal output circuit and the high voltage output circuit separately, the high voltage detection circuit extracts an output voltage that changes in proportion to fluctuations in the high voltage. a control means that receives the output voltage of the high voltage detection circuit and generates a control voltage in response when the input voltage becomes larger than a first specific reference voltage; and a period during which the control voltage is applied. , a charging circuit that charges a unique DC voltage and extracts a charging voltage that increases over time; A voltage value at a second point in time that occurs later than the voltage value at one point in time is used as a second and third unique reference voltage, respectively, and the comparison input voltage is set as a second and third unique reference voltage, respectively. The first, in response to exceeding the reference voltage of
first and second comparators that take out a second control output; and a first switching that cuts off application of the oscillation voltage from the horizontal drive circuit to the high voltage output circuit in response to the first control output. A protection circuit for a horizontal deflection circuit, comprising: a circuit; and a second switching circuit that cuts off application of the oscillation voltage from the horizontal drive circuit to the horizontal output circuit in response to the second control output.