JPS5918780Y2 - Detection signal generation circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an abnormally high voltage detection signal generation circuit for a television receiver.

In a conventional television receiver, as shown in Figure 1,
The flyback transformer 1 is provided with a low voltage winding 12, and the flyback pulse generated in the winding 12 is rectified and smoothed to obtain a DC low voltage.

In order to improve regulation characteristics, the diode 3 is made conductive during the horizontal scanning period, so even if the high voltage increases abnormally and therefore the amplitude of the flyback pulse increases, the fluctuation in the DC low voltage is small.

Note that a negative flyback pulse is generated in the winding 12.

For this reason, a detection winding 13 that generates positive flyback pulses is newly provided, and the flyback pulses generated in this winding 13 are rectified and smoothed to detect fluctuations in the DC voltage.

That is, the detection signal generation circuit includes the winding 13 and the diode 4.
, a protective resistor 5' and a capacitor 9.

In Fig. 1, 2 is a high-voltage rectifier, 5 and 5' are protective resistors, 8 is a capacitor, 10 is a load circuit driven by a low voltage such as a video amplifier, and 11 is a high-voltage rectifier when the charging voltage of the capacitor 9 is higher than a predetermined voltage. This is a high voltage limiting circuit that operates to stop the generation of high voltage when the voltage rises.

In the conventional detection signal generation circuit, it is necessary to newly provide a winding 13 dedicated to detection in the flyback transformer 1, and
Even if the protective resistor 5' is disconnected for some reason and the detection signal generation circuit ceases to perform its function, it will not be noticed, so if abnormal high voltage occurs in such a case, it will cause abnormalities such as X-ray radiation and fire. There is also the risk of causing a situation.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a detection signal generation circuit that generates a signal according to the amplitude of a flyback pulse without providing a detection winding.

The present invention uses the voltage generated in the low voltage winding during the horizontal retrace period when the diode rectifying the horizontal flyback pulse is cut off as the signal to be detected for detecting voltage fluctuations.

The present invention will be explained below with reference to FIGS. 2 to 5.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

A flyback pulse shown in FIG. 3A is generated at the connection point 6 between the protective resistor 5 and the diode 3.

Diode 3 conducts during the horizontal scanning period and capacitor 8
is charged to voltage E1, and a low DC voltage E is obtained as in the case of FIG.

On the other hand, a capacitor 9 and a diode 4 are connected in series between the connection point 6 and the ground, and since the diode 4 is conductive during the horizontal retrace period, the capacitor 9 is charged to a voltage E2.

Therefore, a voltage shown in FIG. 3B is generated at the connection point 14 between the diode 4 and the capacitor 9.

In other words, at the connection point 14, a voltage with a DC waveform obtained by recirculating the flyback pulse generated in the low voltage winding 12 so that the lowest voltage becomes 0 volts is generated, so that fluctuations in the flat part of this waveform By detecting this, it is possible to detect fluctuations in the amplitude of the flyback pulse, that is, fluctuations in high pressure.

Therefore, the detection winding 13 is unnecessary, and if the protective resistor 5 is disconnected, circuits that operate at low voltage, such as video amplifiers, will no longer operate, so such a failure can be detected immediately. be able to.

Therefore, it is possible to avoid a dangerous situation in which the television receiver is used without realizing that the detection signal generation circuit is not operating.

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

Diode 3 conducts during the horizontal scanning period, and capacitor 8
is charged to El in the same way as in FIGS. 1 and 2.

Since the diode 3 is provided between the winding 12 and the ground,
The voltage at the cathode of diode 3 changes as shown in FIG.

That is, since the maximum voltage at the cathode of the diode 3 becomes the amplitude E1+E2 of the flyback pulse, the capacitor 9 is charged to E1+E2, and this charging voltage varies with the amplitude of the flyback pulse.

Therefore, the occurrence of abnormally high voltage can be detected by fluctuations in the charging voltage of the capacitor 9.

As described above, according to the present invention, the low voltage generation winding 1
Since the variation in the amplitude of the flyback pulse generated at 2 is detected, there is no need to provide a new detection winding 13, and there is no need to install a new detection winding 13, and the detection signal generation circuit is Even if it stops working, you can immediately notice this.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional detection signal generation circuit, Fig. 2 is a circuit diagram showing an embodiment of the detection signal generation circuit according to the present invention, Fig. 3 is a voltage waveform diagram of its main part, and Fig. 4 5 is a circuit diagram showing another embodiment of the present invention, and FIG. 5 is a voltage waveform diagram of the main part thereof.

Claims (1)

[Scope of utility model registration request] DC low voltage that generates DC low voltage by rectifying the flyback pulse generated in the low voltage winding of the flyback transformer using a diode that conducts during the horizontal scanning period and shuts off during the horizontal retrace period. In a display device equipped with a cathode ray tube having a generating circuit and a high voltage limiting circuit that detects when the amplitude of the flyback pulse exceeds a predetermined amplitude and prevents the generation of abnormally high voltage, the low voltage winding is connected to the low voltage winding. Level shifting means for shifting the DC level of the generated flyback pulse to generate a voltage whose maximum value is equal to the amplitude of the flyback pulse, and supply means for supplying the voltage with the shifted DC level to the high voltage limiting circuit. A detection signal generation circuit characterized in that it is provided with.