JPH0349374A - High voltage generating circuit - Google Patents

Abstract

PURPOSE:To improve the reliability a hazard prevention of against X-ray emission from a cathode-ray tube by providing a hazard discriminating circuit which outputs an oscillation stop signal in the case of excess of the detected voltage detected by a high voltage detecting part over a set reference value and a horizontal oscillation stopping circuit which receives this oscillation stop signal to stop the operation of a horizontal oscillating circuit. CONSTITUTION:A high output voltage, which is divided by a breeder resistor 21 and taken out, is detected by a variable resistor 22 as the high voltage detecting part. A comparator amplifier 26 of a hazard discriminating circuit 25 always compares the voltage detected by the variable resistor 22 and the reference voltage (set reference value) applied from a second reference power source 27 with each other and applies the oscillation stop signal to a horizontal oscillation stopping circuit 28 in the case of excess of the detected voltage over the reference voltage. The horizontal oscillation stopping circuit 28 receives this oscillation stop signal to immediately stop the operation of a horizontal oscillating circuit 1. The horizontal oscillation frequency is not outputted from the horizontal oscillating circuit by this stop of the horizontal oscillation operation, and a hazard that X rays are emitted from a cathode-ray tube by the abnormal voltage is surely prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high voltage generation circuit for a television receiver or the like, and in particular to a means for stabilizing high voltage output voltage and
The present invention relates to a high voltage generation circuit equipped with radiation prevention means.

[Conventional technology]

-JW, in television receivers and CRT display devices, there is a phenomenon in which when brightness increase adjustment is performed, high voltage output current flows to the anode of the cathode ray tube, causing the high voltage output voltage to drop. When the high output voltage drops in this manner, the output impedance cannot be significantly lowered, and there is a problem in that it becomes difficult to achieve high definition image quality. Furthermore, if the flyback pulse voltage becomes abnormally large, X-rays are emitted from the cathode ray tube, which has a negative effect on the human body.

In recent years, measures have been taken to prevent the drop in the high-voltage output voltage and furthermore to prevent the emission of X-rays from the cathode ray tube, and a typical circuit for this is shown in Figure 3. .

This circuit consists of a horizontal oscillation circuit 1 that generates a horizontal oscillation frequency.
, a horizontal drive circuit 2 that amplifies the signal from the horizontal oscillation circuit 1 and shapes the waveform; and a flyback pulse is generated based on the output from the horizontal drive circuit 2, and a sawtooth wave is applied to the horizontal deflection coil. A protection circuit 6 includes a horizontal output circuit 3 that applies current, a flyback transformer 4 that boosts the flyback pulse generated in the horizontal output circuit 3 and applies a high output voltage to the anode 9a of the cathode ray tube 9, and a comparison circuit 5. , a high-voltage detection section 12 that detects a high-voltage output voltage, and a correction circuit 13 that corrects the high-voltage output voltage to a constant value.

The flyback transformer 4 includes a low voltage coil (minusary coil) 7, a high voltage coil (secondary coil) 8, and a detection coil (tertiary coil N) for extracting the detection voltage of the flyback pulse.
It has O. The comparison circuit 5 compares a reference voltage supplied via a terminal 11 from a reference power source (not shown) with a detection voltage of a flyback pulse detected by a detection coil 10. The protection circuit 6 stops the operation of the horizontal oscillation circuit 1 when the detected voltage exceeds the reference voltage, thereby preventing X-rays from being emitted from the cathode ray tube 9.

Further, the high voltage detection section 12 detects the high voltage output voltage and applies this detection information to the correction circuit 13. Based on this detection information, the correction circuit 13 generates an additional voltage corresponding to the drop in the high-voltage output voltage, and applies this to the high-voltage coil 8 to stabilize the high-voltage output voltage.

[Problem to be solved by the invention]

However, in the conventional device described above, the detection voltage for preventing the emission of X-rays is detected by the detection coil IO, which is separated from the high voltage side, so it is not possible to detect abnormalities in the high voltage stabilizing circuit. First, a problem arises in terms of reliability as a means for preventing the emission of X-rays. In other words, if the correction circuit 13 that constitutes the high-voltage stabilization circuit malfunctions and continues to apply additional voltage to the high-voltage coil 8 side even if the high-voltage output voltage reaches a dangerous voltage that emits X-rays, this high voltage Since the output voltage is not directly detected, the protection circuit 6 cannot detect this abnormality, and a dangerous situation occurs in which X-rays are emitted from the cathode ray tube 9.

The present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to promptly detect an abnormality even if it occurs in the high voltage stabilizing circuit, and to detect this abnormality before X-rays are emitted from the cathode ray tube. An object of the present invention is to provide a high voltage generation circuit that can reliably stop the oscillation operation of a horizontal oscillation circuit.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention includes a horizontal oscillation circuit that generates a horizontal oscillation frequency, a horizontal drive circuit that amplifies and shapes the signal from this horizontal oscillation circuit, and a flyback pulse based on the output from this horizontal drive circuit. a horizontal output circuit that generates a sawtooth wave current to a horizontal deflection coil; a flyback transformer that boosts a flyback pulse generated in the horizontal output circuit and applies a high output voltage to an anode of a cathode ray tube;
A high voltage generation circuit that includes a high voltage detection section that detects a high voltage output voltage, and a high voltage output voltage correction circuit that adds an additional voltage corresponding to the drop in the high voltage output voltage to the high voltage output voltage based on the high voltage detection value of the high voltage detection section. , a danger discrimination circuit outputs an oscillation stop signal when the detected voltage detected by the high voltage detection section exceeds a set reference value, and a horizontal oscillation circuit receives the oscillation stop signal from the danger discrimination circuit and operates the horizontal oscillation circuit. The horizontal oscillation stop circuit is configured to stop the horizontal oscillation.

[Effect]

In the present invention, the high voltage output voltage is detected by the high voltage detection section, and when the high voltage output voltage drops, the correction circuit adds an additional voltage corresponding to this drop to the high voltage coil based on the detection information of the high voltage detection section. Stabilizes high voltage output voltage.

On the other hand, the danger discrimination circuit compares the detected voltage detected by the high voltage detection section with a set reference value, and outputs an oscillation stop signal when the detected voltage exceeds the set reference value.

In response to this oscillation stop signal, the horizontal oscillation stop circuit stops the oscillation operation of the horizontal oscillation circuit, thereby preventing the emission of X-rays from the cathode ray tube.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. In the description of this embodiment, the same reference numerals are given to circuit parts that are the same as those of the conventional example, and redundant explanation thereof will be omitted.

In FIG. 1, the configuration of a high voltage generation circuit showing an embodiment of the present invention is shown. In FIG. It consists of a deflection coil 17 and a three-figure correction capacitor 18, applies a sawtooth wave current to the horizontal deflection coil 17, generates a flyback pulse, and applies this to a flyback transformer 19.

The flyback transformer 19 includes a low voltage coil 7 and a high voltage coil 8, and the low voltage coil 7 is connected to the output side of the horizontal output circuit 3. Further, the high voltage side of the high voltage coil 8 is connected to the anode 9a of the cathode ray tube 9 via a high voltage rectifier diode 20.
It is connected to the. A correction coil 13 is connected to the low voltage side of the high voltage coil 8.

One end side of a bleeder resistor 21 is connected to the high voltage side of the high voltage coil 8, that is, the cathode side of the high voltage rectifier diode 20, and the resistor 2
One end of a variable resistor 22 serving as a high output voltage detection section is connected to the other end of the variable resistor 22 . This variable resistor 22
The other end is connected to ground. Further, a connection portion between the bleeder resistor 21 and the variable resistor 22, that is, an output portion P of the detection voltage is connected to a negative input terminal of the comparator amplifier 23. Further, the positive side input terminal of the comparator amplifier 23 is connected to the positive side of a first reference power source 24, and the negative side of the first reference power source 24 is connected to ground.

This first reference power supply 24 provides a reference voltage for detecting the amount of drop in the high output voltage. The output side of this comparison amplifier 23 is connected to the input side of the correction circuit 13. These bleeder resistor 21, variable resistor 22, comparator amplifier 23, first reference power supply 24, and correction circuit 13 constitute a high voltage stabilizing means that stabilizes the high voltage output voltage.

A danger discrimination circuit 25 is connected to the output section P of the detected voltage. This danger determination circuit 25 is composed of a comparison amplifier 26 and a second reference power supply 27. The plus side input terminal of the comparator amplifier 26 is connected to the output section P of the detection voltage, and the minus side input terminal is connected to the plus side of the second reference power supply 27. The negative side of the second reference power source 27 is connected to ground.

This second reference power source 27 provides a reference value for determining the dangerous voltage for emitting X-rays. This comparison amplifier 2
6, information is input as a voltage signal to the plus side terminal and the minus side terminal, and this voltage signal is converted into a current value by impedance conversion, and a current signal is output from the output side.

A horizontal oscillation stop circuit 2 is provided on the output side of this danger discrimination circuit 25.
8 are connected. This horizontal oscillation stop circuit 28 stops the oscillation operation of the horizontal oscillation circuit 1 when receiving an oscillation stop signal from the danger discrimination circuit 25. In this embodiment, the variable resistor 22, the danger discrimination circuit 25, The horizontal oscillation stop circuit 28 constitutes an X-ray emission prevention means.

The present embodiment is configured as described above, and its operation will be explained below.

While the circuit is in operation, the high voltage output voltage is connected to the bleeder resistor 2
1 and taken out, and detected by a variable resistor 22 as a high voltage detection section. This detection voltage is then applied to the negative terminal of the comparison amplifier 23 and the positive input terminal of the comparison amplifier 26, respectively. Comparison amplifier 23
compares the reference voltage applied by the first reference power supply 24 with the detected voltage of the high voltage output voltage, and when there is no drop in the high voltage output voltage, that is, when the detected voltage is higher than the reference voltage, the voltage is sent to the correction circuit 13. When no signal is applied, the correction circuit 13 does not operate, and therefore no additional voltage is applied to the high voltage coil 8. On the other hand, when a high-voltage output current flows due to brightness increase adjustment or the like, the high-voltage output voltage drops. Due to this voltage drop, the detected voltage becomes lower than the reference voltage applied from the first reference power supply 24. When the detected voltage becomes lower than the reference voltage in this way, the comparator amplifier 23 applies a signal instructing addition to the correction circuit 13.

Based on this signal, the correction circuit creates an additional voltage corresponding to the drop in the high voltage output voltage, and applies this to the high voltage coil 8. This addition operation of the correction circuit 13 controls the high voltage output voltage to be constant.

On the other hand, the comparison amplifier 26 of the danger discrimination circuit 25 compares the detection voltage detected by the variable resistor 22 with the second reference power supply 2.
7 is constantly compared with the reference voltage (set reference value) applied from 7, and when the detected voltage becomes larger than the reference voltage, an oscillation stop signal is applied to the horizontal oscillation stop circuit 28. The horizontal oscillation stop circuit 28 receives this oscillation stop signal and starts the horizontal oscillation circuit 1.
Immediately stop the operation. By stopping this horizontal oscillation operation, the horizontal oscillation frequency is not output from the horizontal oscillation circuit, and the danger of X'kfA being emitted from the cathode ray tube 9 due to abnormal voltage is reliably prevented.

Also, the correction circuit 13 may malfunction and the detected voltage may be lower than the first -
Even if a situation occurs in which the additional voltage continues to be added even though it is higher than the reference voltage applied from O reference voltage rJ, 24, an abnormal increase due to the addition of the high voltage output voltage will cause the detected voltage to become the second reference. Since the voltage exceeding the reference voltage applied from the power supply 27 is immediately detected and the horizontal oscillation operation is stopped, the reliability of preventing X-ray emission is greatly increased.

Further, by detecting the high output voltage and preventing X-ray emission, the following effects can be obtained. That is, in the conventional circuit shown in FIG. 3, since it is not possible to detect an abnormality in the correction circuit 13, the high voltage output current 1. , and the high voltage output voltage E11, the high voltage output voltage E must be stabilized at a voltage level of EIIL, which is considerably lower than the dangerous voltage E, X at which X-rays are emitted. Must be. In this way, if you set the voltage from E IIK to Eui, which is considerably lower, as the operating voltage of a television receiver, etc.,
The correction circuit 13 has malfunctioned and the added voltage ΔEll becomes EH.
Even if E and l are applied to L, there is still a dangerous voltage EI
Since the radiation does not reach IX, safety against X-ray emission is ensured.

However, if the operating voltage is set at such a low voltage level EIIL, a problem arises in that the focus of the television receiver or display device becomes poor and unclear.

In this regard, as in this embodiment, if the high voltage output voltage E□ is directly detected and the protection operation against X-ray emission is performed using this detected voltage, the operating voltage of the television receiver etc. can be reduced to the dangerous voltage EII.
The advantage is that the voltage can be set to EIIIll slightly lower than X. This is because, if the voltage E exceeds even a little, this abnormality is detected by the comparator amplifier 26 of the danger discrimination circuit 25, and the horizontal oscillation stop operation is immediately activated.

In this way, in this embodiment, the operating voltage of the television receiver and display device can be set to a high voltage, so a bright and clear screen can be obtained.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various ways.

For example, the comparator amplifier 23 may be any circuit that has the function of comparing the detected voltage and the reference voltage and outputting a signal when the detected voltage is lower than the reference voltage.
The comparator amplifier 26 can be composed of a circuit such as an operational amplifier, an error amplifier, or an operational amplifier.Also, the comparator amplifier 26 can be composed of a circuit similar to the comparator amplifier 23, but it can also be composed of a simpler amplification function such as a transistor. It can be configured by a circuit having.

〔Effect of the invention〕

Since the present invention is configured to directly detect the high-voltage output voltage and prevent X-ray emission, it is possible to prevent abnormalities in the high-voltage output voltage caused by an abnormal increase in the flyback pulse voltage, disconnection of the resonant capacitor, etc. It is now possible to reliably detect not only an increase in the high voltage output voltage but also an abnormal increase in the high voltage output voltage due to an abnormality in the correction circuit that stabilizes the high voltage by adding an additional voltage, and to stop the horizontal oscillation operation. It becomes possible to significantly improve the reliability of preventing dangers from X-ray emission.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the high voltage generation circuit according to the present invention, Fig. 2 is an explanatory diagram showing an example of setting the operating voltage of a television receiver or display device, and Fig. 3 is a circuit diagram showing an example of setting the operating voltage of a television receiver or display device. FIG. 2 is a circuit diagram of a conventional general high voltage generation circuit provided with stabilizing means and means for preventing X-ray emission. 1...Horizontal oscillation circuit, 2...Horizontal drive circuit, 3
...Horizontal output circuit, 4...Flyback transformer,
5... Comparison circuit, 6... Protection circuit, 7... Low voltage coil, 8... High voltage coil, 9... Braun tube, 9a
... Anode, 10... Detection coil, 11... Terminal, 12... High voltage detection section 1.13... Correction circuit, 1
4... Horizontal output transistor, 15... Damper diode, 16... Resonance capacitor, 17... Horizontal deflection coil, 18... Figure 8 correction capacitor, 19...
Flyback transformer, 20... High voltage rectifier diode, 21... Bleeder resistor, 22... Variable resistor, 2
3.26... Comparison amplifier, 24... First reference power supply, 25... Danger discrimination circuit, 27... Second reference power supply, 28... Horizontal oscillation stop circuit. No.

Claims (1)

[Claims] A horizontal oscillation circuit that generates a horizontal oscillation frequency, a horizontal drive circuit that amplifies the signal from this horizontal oscillation circuit and shapes the waveform, and generates a flyback pulse based on the output from this horizontal drive circuit.
a horizontal output circuit that applies a sawtooth current to a horizontal deflection coil, a flyback transformer that boosts the flyback pulse generated in the horizontal output circuit and applies a high output voltage to the anode of the cathode ray tube, and a high voltage that detects the high output voltage. In a high voltage generation circuit comprising a detection section and a high voltage output voltage correction circuit that adds an additional voltage corresponding to a drop in the high voltage output voltage to the high voltage output voltage based on the high voltage detection value of the high voltage detection section, the high voltage detection section A danger discrimination circuit that outputs an oscillation stop signal when the detected voltage exceeds a set reference value, and a horizontal oscillation stop circuit that stops the operation of the horizontal oscillation circuit upon receiving the oscillation stop signal from the danger discrimination circuit. A high voltage generation circuit characterized by having: