JP2540152B2 - Anode voltage adjustment circuit for cathode ray tube - Google Patents

Description

The present invention relates to an anode voltage adjusting circuit of a cathode ray tube (hereinafter referred to as CRT), and particularly to adjusting an anode voltage for obtaining an optimum focus point of a magnetic field focusing CRT. Regarding the circuit.

[Conventional technology]

Conventionally, a magnetic field focusing CRT having an electrode structure including a cathode K, a first grid G ₁ , a second grid G ₂ and an anode A is known. In this type of CRT, generally, a control signal such as a video signal is input to the first grid G ₁ and the cathode K, and an anode voltage generated in the secondary winding of the flyback transformer is applied to the anode A. Circuit is configured. For example, on the primary side of the flyback transformer, the horizontal drive pulse is supplied to drive the deflection yoke, and at the same time, the flyback pulse resonated by the resonance capacitor and the deflection yoke during the horizontal flyback period is applied to the primary winding of the flyback transformer. By supplying the line, the secondary winding can be configured to generate the required anode voltage.

However, in this type of CRT, it is generally adopted to add a horizontal retrace pulse to the low-voltage part of the high-voltage winding in order to keep the high voltage constant. Then, the focus voltage extracted from the intermediate tap of the high voltage winding tends to change. Therefore, in this case, in order to obtain the optimum focus point of the CRT,
For example, a method of changing a flyback voltage width by a flyback transformer or changing a power supply voltage has been proposed.

[Problems to be solved by the invention]

However, the former method of changing the flyback voltage range has a drawback that not only the adjustment voltage cannot be adjusted smoothly because the handling voltage is generally high, but also the adjustment range is not sufficient. According to the latter method of changing the power supply voltage,
Not only will power loss occur, but the deflection size of the CRT will also vary, making it impossible to reproduce proper images.

Further, the flyback pulse obtained on the primary side of the flyback transformer is affected by the deflection yoke, the resonance capacitor, the flyback transformer, etc., and the pulse width and the peak value thereof are varied.
It is difficult for the anode voltage generated on the secondary side to fall within the allowable value required for CRT.

Therefore, an object of the present invention is to provide a flyback transformer,
Take a tap from the secondary winding, insulate the resulting voltage as a grid voltage for the cathode ray tube, and use this as an adjustment voltage for the anode voltage derived from the secondary winding of the flyback transformer. It is an object of the present invention to provide an anode voltage adjusting circuit for a cathode ray tube that can achieve the adjustment of the optimum focus point easily by superimposing with a simple circuit configuration and without causing power loss.

[Means for solving the problem]

To achieve the above object, an anode voltage adjusting circuit for a cathode ray tube according to the present invention extracts a first flyback pulse from a part of one winding of a flyback transformer, rectifies and smoothes the obtained voltage. Adjusting the level, superimposing it on the second flyback pulse obtained from the winding, and rectifying and smoothing the adjusted second flyback pulse to obtain the anode voltage of the cathode ray tube. The circuit configuration is such that focus is adjusted by adjusting the anode voltage by adjusting the voltage level without adjusting the grid voltage.

In this case, for example, the first flyback pulse is extracted from a part of one winding of the flyback transformer in a direct current manner, rectified and smoothed to obtain a direct current voltage, and the direct current voltage is directly supplied from the winding. Is superimposed on the second flyback pulse generated in the above, the second flyback pulse on which the DC voltage is superimposed is rectified and smoothed to obtain the anode voltage of the cathode ray tube, and the level of the DC voltage is adjusted. By adjusting the anode voltage by adjusting the anode voltage, the circuit can be configured to adjust the focus without adjusting the grid voltage.

[Action]

According to the anode voltage adjusting circuit of the cathode ray tube (CRT) of the present invention, the anode voltage supplied to the CRT fluctuates due to the fluctuation of the flyback pulse on the primary side of the flyback transformer, and the focus adjustment of the CRT becomes improper. In this case, a tap for obtaining a constant voltage to be supplied to the grid of the CRT is provided on the secondary winding of the flyback transformer, and the constant voltage thus obtained can be adjusted by an adjusting resistor. By superimposing on the anode voltage generated in the line, the anode voltage can always be maintained in an appropriate state and the optimum focus point of the CRT can be easily obtained.

〔Example〕

Next, an embodiment of an anode voltage adjusting circuit of a cathode ray tube (CRT) according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a main part circuit diagram showing a typical embodiment of an anode voltage adjusting circuit of a CRT according to the present invention. In FIG. 1, reference numeral 10 indicates a magnetic field focusing CRT, and its electrode configuration is cathode K, first grid G ₁ , second grid G ₂
And an anode A. Further, reference numeral 12 indicates a flyback transformer, the primary side winding L _{1 of} this transformer 12
Is a transistor Tr that supplies a horizontal drive pulse, a deflection yoke DY, a DC blocking capacitor C ₁ , a resonant capacitor C ₂
And the damper diode D ₁ are connected.

However, in the present invention, the flyback transformer
A tap is provided on a part of the secondary winding L ₂ of 12 and the voltage generated at this tap is rectified via the rectifying diodes D ₂ and D ₃ and the smoothing capacitor C ₄ via the DC insulating capacitor C _3. Then, the circuit is configured to obtain the supply voltage V _G2 to the second grid G ₂ . Further, a bleeder resistor R ₁ is provided on the output lines of the diode D ₃ and the capacitor C ₄ , and the adjustment voltage obtained by this bleeder resistor R ₁ is induced in the secondary winding L ₂ of the flyback transformer 12. The circuit is configured to be superimposed on the anode voltage. Therefore, the anode voltage thus obtained is applied to the anode of the CRT ₁₀ via the rectifier circuit _Recf . In addition, in the first grid G ₁ of CRT10,
The video signal is provided via capacitor C ₅ and resistor R ₂ .

With this configuration, the CRT's second grid G
_It is possible to supply a constant voltage to ₂ and effectively use this voltage as the adjustment voltage of the anode voltage.

〔The invention's effect〕

As is apparent from the above-described embodiments, according to the present invention, the CRT can be more easily installed than the secondary winding of the flyback transformer.
It is possible to obtain a constant voltage to be supplied to the grid of, and to use this voltage to adjust it, and by using it as the adjustment voltage of the anode voltage, the optimum focus point of the CRT can be set properly and smoothly. it can.

In particular, according to the present invention, the secondary winding of the flyback transformer is provided with a tap, and the voltage induced in this is taken out as a grid voltage. Therefore, the number of windings of the flyback transformer can be increased. Miniaturization can be maintained. In addition, DC adjustment is possible with a simple circuit as the adjustment voltage of the anode voltage, and stable focus adjustment can be achieved.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an anode voltage adjusting circuit of a cathode ray tube (CRT) according to the present invention. 10 …… CRT 12 …… Flyback transformer L ₁ …… Primary side winding L ₂ …… Secondary side winding Tr …… Transistor D ₁ …… Damper diode DY …… Deflecting yoke C ₁ …… DC blocking capacitor C ₂ …… Resonance capacitor C ₃ …… DC insulation capacitor D ₂ , D ₃ …… _Rectifying diode C ₄ …… Smoothing capacitor R ₁ …… _Bleeder resistor R _ecf …… Rectifier circuit

Claims (2)

(57) [Claims] 1. A voltage obtained by extracting, rectifying and smoothing a first flyback pulse from a part of one winding of a flyback transformer and adjusting the level of the voltage to obtain a second voltage from the winding. The flyback pulse of the above, and the adjusted voltage is rectified and smoothed to the anode voltage of the cathode ray tube by rectifying and smoothing the superimposed second flyback pulse, and the level of the voltage is adjusted without adjusting the grid voltage. An anode voltage adjusting circuit for a cathode ray tube, characterized in that the circuit is configured to adjust the focus by adjusting the anode voltage. 2. A direct current is insulated from a part of one winding of a flyback transformer, a first flyback pulse is taken out, rectified and smoothed to obtain a direct current voltage, and this direct current voltage is supplied from the winding. Directly superposing on the generated second flyback pulse, rectifying and smoothing the superposed second flyback pulse to obtain the anode voltage of the cathode ray tube, and adjusting the level of the direct current voltage. The anode voltage adjusting circuit for a cathode ray tube according to claim 1, wherein the circuit configuration is such that the focus is adjusted without adjusting the grid voltage by adjusting the anode voltage.