JPH10126638A - Protection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a cathode-ray tube when a horizontal deflection coil and a linearity coil are disconnected by detecting the pulse height of a flyback transformer, which is generated in a horizontal deflection circuit, detecting the abnormality of the horizontal deflection circuit and stopping power. SOLUTION: When the horizontal deflection coil and the linearity coil are cut or when a pattern foil on a substrate is cut owing to some cause, the value of the inductance of the flyback transformer 5 becomes large. When the horizontal deflection coil is opened, pulse height becomes small and pulse height generated on a secondary side, which follows it, becomes small. Thus, the output value of a rectifier circuit 10 becomes small and the voltage of the input terminal of a comparator 11 drops. When the value of reference voltage is set to that between the regular time voltage of the input terminal of the comparator 11 and the open time voltage of the deflection coil, the output of the comparator 11 becomes a low level at regular time and becomes the height level when the horizontal deflection coil and the like open. Thus, a protection circuit 8 is operated by giving the signal to the microcomputer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for performing processing such as turning off a power supply when an abnormality occurs in a horizontal deflection coil or a linearity coil of a horizontal deflection circuit of a television receiver.

[0002]

2. Description of the Related Art A conventional horizontal deflection circuit will be described below. FIG. 4A is a block diagram showing a conventional horizontal deflection circuit. In FIG. 4A, 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a deflection coil, 4 is an S-shaped correction capacitor, 5 is a flyback transformer, 6 is a cathode ray tube, 7 is a DC power supply, and 8 is a protection circuit. , 9 is a signal processing circuit, 14 is a diode, and 15, 16, and 17 are capacitors, whose capacities are C1, C2, and C3, respectively.

In order to explain the conventional horizontal deflection circuit shown in FIG. 4A, the combined capacitance of C1, C2 and C3 is C, and the primary side inductance of the flyback transformer 5 is the combined inductance of the inductance of the horizontal deflection coil 3. As L,
Further, since the voltage between both ends of the S-shaped correction capacitor 4 is substantially equal to the power supply voltage of 7, it can be simplified as shown in FIG.

The operation of FIG. 4B will be described below with reference to FIG. (1) A horizontal drive pulse is applied to the base of the horizontal output transistor. When the drive pulse is at the low level, the transistor is off. At this time, no current flows through the circuit because the diode D is reverse-biased.

(2) When the horizontal drive pulse goes high, the transistor turns on and a collector current that increases linearly according to the power supply voltage and the inductance of L flows through the horizontal deflection coil.

(3) When the drive pulse goes low again and the horizontal output transistor turns off, the collector current becomes 0, but the current of the deflection coil continues to flow, and decreases while charging the resonance capacitor C to become 0.

(4) Thereafter, the resonance capacitor starts discharging and a current flows in the opposite direction through the deflection coil. In the resonance phenomenon of L and C, the capacitor C is charged in the opposite direction after the energy of the capacitor has shifted to L, but the damper diode D is connected and the voltage across the deflection coil becomes the forward voltage of the diode. As a result, the current is conducted and the current of the deflection coil flows through the damper diode D.

(5) When the drive pulse goes high again, the operation returns to the operation (2), and the operations (2) to (5) are repeated, so that a saw-tooth current flows through the horizontal deflection coil. During the resonance periods (3) and (4), a pulse voltage appears at both ends of the capacitor C as shown in FIG. This pulse height is given by (Equation 1).

[0009]

(Equation 1)

In FIG. 4A, since a pulse synchronized with the flyback pulse is required in the signal processing circuit 9 to achieve horizontal synchronization, the signal is divided by C2 and C3 to lower the voltage value and to be applied to the signal processing circuit. Have given. Reference numeral 8 denotes a protection circuit, which supplies a signal to the microcomputer when an abnormal current flows in a power supply line for supplying power to the horizontal deflection circuit, and stops the power supply.

[0011]

In the conventional horizontal deflection circuit configured as described above, when an abnormal current flows due to a short circuit of each component of the horizontal deflection circuit, the protection function operates as shown in the conventional example. I do. However, if the horizontal deflection coil or linearity coil, which is a component of the horizontal deflection circuit, is broken, or if the pattern foil on the substrate breaks for some reason, the protection circuit does not operate, and the horizontal deflection current does not flow. The beam current concentrates in the center of the tube, causing damage to the cathode ray tube.

[0012]

In order to solve the above-mentioned problems, the present invention detects an abnormality in the horizontal deflection circuit by detecting the pulse height of a flyback pulse generated in the horizontal deflection circuit, and stops the power supply. It is intended to be.

[0013]

The present invention according to a second aspect of the present invention provides a rectifier circuit for smoothing a pulse generated from a secondary side of a flyback, and a rectifier circuit for comparing a rectified voltage by the rectifier circuit with a reference voltage. And a power supply control circuit for detecting the output voltage of the comparator and controlling the power supply. The power supply control circuit detects an abnormality in the horizontal deflection circuit, disconnection of the deflection coil, etc. from the secondary side of the flyback transformer. The power supply is stopped by detecting that the pulse height of the generated pulse becomes small.

According to a third aspect of the present invention, there is provided a capacitor for dividing a collector pulse of a horizontal output transistor.
And a capacitor 2, a rectifier circuit for smoothing a pulse at a middle point between the capacitors 1 and 2, a comparator for comparing a rectified voltage by the rectifier circuit with a reference voltage, and a power supply for detecting an output voltage of the comparator. This is a protection circuit composed of a power supply control circuit that controls the
When the deflection coil is disconnected, the power supply is stopped by detecting that the pulse height of the collector pulse of the horizontal output transistor is small.

According to a fourth aspect of the present invention, there is provided a rectifier circuit for smoothing a heater pulse generated from a flyback, a comparator for comparing a rectified voltage by the rectifier circuit with a reference voltage, and an output of the comparator. A protection circuit consisting of a power supply control circuit that detects the voltage and controls the power supply, and detects when the pulse height of the collector pulse of the horizontal output transistor decreases when an abnormality in the horizontal deflection circuit or disconnection of the deflection coil occurs. And shut off the power.

(Embodiment 1) An embodiment of the present invention described in claims 1 and 2 of the present invention will be described below with reference to FIG.

In FIG. 1, 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a horizontal deflection coil, 4 is an S-shaped correction capacitor, 5 is a flyback transformer, 6 is a cathode ray tube, 7 is a DC power supply, 8 protection circuit, 9 is a signal processing circuit, 10 is a rectifier circuit, 11 is a comparator, 12 is a power supply, 13
Is a microcomputer, 14 is a damper diode, 15, 16,
Reference numeral 17 denotes a capacitor having a capacity of C1, C2, C
3 is assumed.

A horizontal drive circuit 1, a horizontal output transistor 2, capacitors 15, 16, 17, a damper diode 14, a horizontal deflection coil 3, an S-shaped correction capacitor 4,
Flyback transformer 5, CRT 6, DC power supply 7,
The basic operation of the protection circuit 8 is the same as that of the conventional example, and the description is omitted. In addition to the conventional circuit of FIG. 4A, a pulse generated in the secondary winding of the flyback transformer 5 is smoothed by the rectifier circuit 10 and input to the input terminal 1 of the comparator 11. A reference voltage is applied to the other input terminal 2 of the comparator 11 by a DC power supply. The value of the reference voltage will be described later. The output of the comparator 11 is connected to the microcomputer 13.

In this configuration, when the horizontal deflection coil or linearity coil is cut, or when the pattern foil on the substrate is cut for some reason, the inductance value corresponding to L in FIG. The value changes from the parallel connection of the coil and the inductance of the primary side of the flyback transformer to the inductance of the primary side of the flyback transformer. Here, the relationship between the inductance value of L and the peak value of the flyback pulse is (Equation 1).
Therefore, the pulse height when the horizontal deflection coil is open decreases, and the pulse height generated on the secondary side decreases accordingly. As a result, the output value of the rectifier circuit 10 decreases and the voltage of the input terminal 1 of the comparator 11 becomes Go down. Here, if the value of the reference voltage is set to a value between the normal voltage of the input voltage 1 of the comparator 11 and the open voltage of the deflecting coil, the output of the comparator 11 becomes the normal Low level, When the horizontal deflection coil or the like is open, it becomes H level, and this signal is given to the microcomputer to operate the protection circuit.

(Embodiment 2) An embodiment of the present invention described in claims 1 and 3 of the present invention will be described below with reference to FIG.

In FIG. 2, 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a horizontal deflection coil, 4 is an S-shaped correction capacitor, 5 is a flyback transformer, 6 is a cathode ray tube, 7 is a DC power supply, 8 protection circuit, 9 is a signal processing circuit, 10 is a rectifier circuit, 11 is a comparator, 12 is a power supply, 13
Is a microcomputer, 14 is a damper diode, 15, 16,
Reference numeral 17 denotes a capacitor having a capacity of C1, C2, C
3 is assumed.

Horizontal drive circuit 1, horizontal output transistor 2, capacitors 15, 16, 17, damper diode 14, horizontal deflection coil 3, S-shaped correction capacitor 4, flyback transformer 5, cathode ray tube 6, DC power supply 7, protection circuit 8 Is the same as that of the conventional example, and the description is omitted. In addition to the circuit of FIG. 4 of the conventional example, a flyback pulse is divided by C2 and C3, and a pulse having a reduced voltage is smoothed by a rectifier circuit 10 and input to an input terminal 1 of a comparator 11. A reference voltage is applied to the other input terminal 2 of the comparator 11 by a DC power supply. The value of the reference voltage will be described later. The output of the comparator 11 is the microcomputer 13
Connect to

In this configuration, when the horizontal deflection coil or the linearity coil is cut or the pattern foil on the substrate is cut for some reason, the inductance value corresponding to L in FIG. The value changes from the parallel connection of the coil and the inductance of the primary side of the flyback transformer to the inductance of the primary side of the flyback transformer. Here, the relationship between the inductance value of L and the peak value of the flyback pulse is (Equation 1).
Therefore, the pulse height when the horizontal deflection coil is open becomes small, and the voltage at the connection point of the capacitors C2 and C3 decreases,
As a result, the output value of the rectifier circuit 10 becomes smaller and the comparator 11
The voltage of the input terminal 1 decreases. If the value of the reference voltage is set to a value between the normal voltage of the input voltage 1 of the comparator 11 and the open voltage of the deflection coil, the comparator 1
The output of 1 becomes a low level in a normal state and a high level when a horizontal deflection coil or the like is opened, and the protection circuit is operated by giving this signal to a microcomputer.

(Embodiment 3) An embodiment of the present invention described in claims 1 and 4 of the present invention will be described below with reference to FIG.

In FIG. 3, 1 is a horizontal drive circuit, 2 is a horizontal output transistor, 3 is a horizontal deflection coil, 4 is an S-shaped correction capacitor, 5 is a flyback transformer, 6 is a cathode ray tube, 7 is a DC power supply, 8 protection circuit, 9 is a signal processing circuit, 10 is a rectifier circuit, 11 is a comparator, 12 is a power supply, 13
Is a microcomputer, 14 is a damper diode, 15, 16,
Reference numeral 17 denotes a capacitor having a capacity of C1, C2, C
3 is assumed.

The horizontal drive circuit 1, horizontal output transistor 2, capacitors 15, 16, 17, damper diode 14, horizontal deflection coil 3, S-shaped correction capacitor 4,
Flyback transformer 5, CRT 6, DC power supply 7,
The basic operation of the protection circuit 8 is the same as that of the conventional example, and the description is omitted. In addition to the conventional circuit of FIG. 4A, a heater pulse generated by a flyback transformer is smoothed by a rectifier circuit 10 and input to an input terminal 1 of a comparator 11. A reference voltage is applied to the other input terminal 2 of the comparator 11 by a DC power supply. The value of the reference voltage will be described later. The output of the comparator 11 is connected to the microcomputer 13.

In this configuration, when the horizontal deflection coil or linearity coil is cut or the pattern foil on the substrate is cut for some reason, the inductance value corresponding to L in FIG. The value changes from the parallel connection of the coil and the inductance of the primary side of the flyback transformer to the inductance of the primary side of the flyback transformer. Here, the relationship between the inductance value of L and the peak value of the flyback pulse is (Equation 1).
Therefore, the pulse height when the horizontal deflection coil is open decreases, and the heater pulse generated in the flyback transformer also decreases. As a result, the output value of the rectifier circuit 10 decreases and the voltage of the input terminal 1 of the comparator 11 decreases. Goes down.
Here, if the value of the reference voltage is set to a value between the normal voltage of the input voltage 1 of the comparator 11 and the open voltage of the deflecting coil, the output of the comparator 11 becomes the normal Low level, When the horizontal deflection coil or the like is open, the protection circuit is operated by turning to a high level and supplying this signal to the microcomputer.

[0028]

As described above, the protection circuit of the television receiver according to the present invention has a problem that the horizontal deflection coil or the linearity coil, which is a component of the horizontal deflection circuit, is disconnected or the pattern foil on the substrate is cut off for some reason. In this case, the protection circuit is operated by detecting the voltage of the secondary winding of the flyback transformer to stop the power supply and prevent the cathode ray tube from being damaged.

[Brief description of the drawings]

FIG. 1 is a block diagram of a protection circuit according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram of a protection circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a protection circuit according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a conventional horizontal deflection circuit.

FIG. 5 is an explanatory diagram of the operation of the horizontal deflection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal drive circuit 2 Horizontal output transistor 3 Horizontal deflection coil 4 S-shaped correction capacitor 5 Flyback transformer 6 CRT 7 DC power supply 8 Protection circuit 9 Signal processing circuit 10 Rectifier circuit 11 Comparator 12 Power supply reference voltage 13 Microcomputer 14 Diode 15, 16 , 17 Capacitor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Nono 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A protection circuit for detecting that a deflection current has stopped flowing through a horizontal deflection coil and stopping a power supply. 2. A rectifier circuit for smoothing a pulse generated from a secondary side of a flyback transformer, a comparator for comparing a rectified voltage by the rectifier circuit with a reference voltage, and a power supply for detecting an output voltage of the comparator. A protection circuit consisting of a microcomputer that controls the 3. A first capacitor and a second capacitor for dividing a collector pulse of a horizontal output transistor;
A rectifier circuit for smoothing a pulse at a connection point between the first capacitor and the second capacitor; a comparator for comparing a rectified voltage by the rectifier circuit with a reference voltage; A protection circuit consisting of a controlling microcomputer. 4. A rectifier circuit for smoothing a heater pulse generated from a flyback transformer, a comparator for comparing a rectified voltage by the rectifier circuit with a reference voltage, and detecting an output voltage of the comparator to control a power supply. Protection circuit consisting of microcomputer.