JPH01173975A - Crt monitoring equipment - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a picture burning even when abnormality occurs in a horizontal deflection circuit by driving a high voltage generating circuit by a trigger pulse outputted when the wave height value of a flyback pulse outputted from the horizontal deflection circuit is a constant value or above. CONSTITUTION:When a comparator 300a receives an FBP, it outputs a pulse for a component which exceeds a threshold TH. A waveform shaping circuit 300b to receive this pulse waveform-shapes the pulse into the trigger pulse having a constant duty and drives the base of a flyback transformer driving transistor 26 in a high voltage generating circuit 200. Consequently, when the wave height value of the FBP to be inputted to the comparator 300a becomes the threshold TH or below due to the abnormality of a horizontal deflection circuit 100, etc., the output of the pulse from the comparator 300a is stopped, the flyback transformer driving transistor 2b is turned 'off', and the generation of high voltage at the high voltage generating circuit 200 is stopped. Thus, the picture burning can be prevented beforehand.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a C
The present invention relates to an RT monitor device, and particularly to prevention of burnout of phosphors due to abnormal horizontal deflection.

(Prior Art) FIG. 4 is a schematic diagram showing the structure of an integrated horizontal deflection circuit and a high voltage generation circuit that are commonly used in conventional CRT monitor devices.

In this figure, 1 is the input terminal for the drive pulse synchronized with the horizontal synchronization signal, 2 is the horizontal output transistor, 3 is the damper diode, 4 is the capacitor, 5 is the capacitor for horizontal figure 8 correction, 6 is the horizontal deflection coil, and 7 is the flywheel. In the back transformer, 8 is a high voltage rectifier diode.

That is, in this circuit, horizontal deflection is performed by inputting a drive pulse synchronized with a horizontal synchronizing signal to input terminal 1, and a flyback pulse (
FBP) in the flyback transformer 7, for example 2
The voltage is increased to a high voltage of about 5KV and supplied to the anode of the CRT. However, in such a circuit, as the horizontal deflection frequency increases, the power loss during switching of the horizontal output transistor 2 increases. Therefore, in high-definition monitors that require high resolution, the horizontal eccentric circuit 100 and the high voltage generation circuit 200 are constructed separately as shown in FIG. However, in this case, generally the horizontal deflection frequency and the operating frequency of the high voltage generating circuit 200 are made the same and synchronized so that the switching noise of the high voltage generating circuit 200 does not affect the screen. In FIG. 5, 2a is a horizontal output transistor, 2b is a flyback transformer driving transistor, 9 is a damper diode, 10 is a horizontal resonance capacitor, and 11 is a dummy deflection coil.

[Problem that the invention seeks to solve]

However, as shown in FIG. 5, in a conventional CRT monitor device that separately includes a horizontal deflection circuit 100 and a high voltage generation circuit 200, protection of the CRT is not considered. If the output transistor 2a fails or the damper diode 3 goes into short mode, horizontal deflection will no longer occur. In this case, if the horizontal synchronizing signal continues to be supplied from the host device that externally controls the CRT and the high voltage generation circuit 200 is operating normally, the CRT
There was a problem in that vertical lines appeared with high brightness on the RT screen, and the phosphor was burned out (screen burn).

The present invention was made to solve these problems, and an object of the present invention is to provide a CRT monitor device that can prevent burnout of the phosphor due to an abnormality in the horizontal deflection circuit.

[Means for solving problems]

The CRT monitor device according to the present invention is provided with a trigger means for outputting a trigger pulse when the peak value of a flyback pulse outputted from a horizontal deflection circuit is equal to or higher than a certain value, and the trigger pulse outputted from the trigger means is used to monitor high voltage. It is designed to drive a generating circuit.

(Function) In this invention, when the peak value of the flyback pulse output from the horizontal deflection circuit becomes below a certain value, that is, when the screen size becomes below a certain value, the trigger pulse is output from the trigger means. The high voltage generation circuit will no longer operate.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the main parts of a CRT monitor device according to the present invention.

In this figure, the same reference numerals as in FIGS. 4 and 5 indicate the same parts, and 4a and 4b are resonance capacitors divided for voltage division. Reference numeral 300 denotes trigger means, which consists of a comparator 300a and a waveform shaping circuit 300b.

Further, FIGS. 2(a), (b), and (C) are waveform diagrams of main signals in FIG. 1.

Next, the operation will be explained.

Normally, in a horizontal deflection circuit, FBP as shown in FIG. 3 occurs during the horizontal retrace period, and the peak value of this FBP is almost directly proportional to the magnitude of the deflection current. Screen burn occurs when
This is a case where an abnormality occurs in the horizontal deflection circuit and the screen size becomes smaller, so if the configuration is configured to detect when the FBP peak value falls below a certain value and stop the high voltage generation circuit, it is possible to It is possible to prevent screen burn from occurring due to abnormalities in the deflection circuit.

In the embodiment shown in FIG. 1, the horizontal deflection circuit 10
0 horizontal output transistor 2a performs a switching operation. When the horizontal output transistor 2a is turned off, the inductance component of the horizontal deflection coil 6 and the resonance capacitor 4a
, 4b resonate in parallel with the series composite capacitance of the horizontal deflection coil 6, and the current value of the horizontal deflection coil 6 is reversed.
At both ends of a and 4b, there is an FB with a peak value of usually about 1 kV.
P occurs. When the comparator 300a receives the FBP as shown in FIG. 2(a), it outputs a pulse as shown in FIG. 2(b) in response to a component exceeding the threshold TH. The waveform shaping circuit 300 receives this pulse.
b is waveform-shaped into a trigger pulse with a constant duty as shown in FIG.
The base of the flyback transformer drive transistor 2b inside is driven.

In the high voltage generation circuit 200, due to the parallel resonance between the horizontal resonance capacitor 10 and the dummy deflection coil 11, an FBP of about 1 kV is normally generated at both ends of the horizontal resonance capacitor 10. This voltage is boosted in a flyback transformer 7, rectified by a high voltage rectifier diode 8, and supplied to the anode of the CRT.

Therefore, if the peak value of FBP input to the comparator 300a becomes below the threshold value TH due to an abnormality in the horizontal deflection circuit 100, the pulse is no longer output from the comparator 300a, and the flyback transformer drive transistor 2b is activated. High voltage generation circuit 2 becomes “off”
At 00, no high pressure is generated. That is, the irradiation of the beam onto the fluorescent screen is stopped, and screen burn can be prevented.

〔Effect of the invention〕

As explained above, this invention is provided with a trigger means for outputting a trigger pulse when the peak value of a flyback pulse outputted from a horizontal deflection circuit is above a certain value, and the trigger pulse outputted from this trigger means causes a high voltage Since the generating circuit is driven, even if an abnormality occurs in the horizontal deflection circuit and the screen size falls below a certain level, there is an effect that screen burn will not occur.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the main parts of the CRT monitor device of the present invention, FIGS. 2(a) to (C) are waveform diagrams of main signals, and FIG. 3 is a waveform diagram showing flyback pulses. , 4 and 5 are schematic diagrams showing the configurations of a horizontal deflection circuit and a high voltage generation circuit used in a conventional CRT monitor device. In the figure, 1 is an input terminal, 2a is a horizontal output transistor, 2
b is a flyback transformer driving transistor, 3 is a damper diode, 4a and 4b are capacitors for synchronization, 5 is a horizontal three-figure correction capacitor, 6 is a horizontal deflection coil, 7 is a flyback transformer, 8 is a high voltage rectifier diode ,1
00 is a horizontal deflection circuit, 200 is a high voltage generation circuit, 300 is a trigger means, 300a is a comparator, 300b is a waveform.

Claims (1)

[Claims] In a CRT monitor device equipped with a horizontal deflection circuit and a high voltage generation circuit, each of which operates independently, a trigger means is provided for outputting a trigger pulse when a peak value of a flyback pulse output from the horizontal deflection circuit is equal to or higher than a certain value. A CRT characterized in that the high voltage generation circuit is driven by a trigger pulse output from the trigger means.
Monitor device.