JPH02107068A - Focus voltage adjustment circuit for cathode-ray tube - Google Patents

Abstract

PURPOSE:To facilitate the adjustment of an optimum focus point with a simple circuit constitution by setting a DC voltage obtained with rectifying a part of a flyback pulse into a variable one. CONSTITUTION:A voltage rectification circuit comprising of a diode D10, a bleeder resistance R10, a capacitor C10 for smoothness and a bleeder resistance R11 is connected to the first coil L7 of the secondary side of a flyback transformer 12. Consequently, when the position of the intermediate tap of the bleeder resistance R10 provided for the first coil L7 is changed, the potential of a cathode K, a first grid G1 and a second grid G2 is changed parallel to an anode voltage. Thus, an optimum focus voltage can be obtained by changing a potential difference relative to the anode voltage, the cathode voltage and the first grid voltage regardless of the brightness of a CRT 10 and modulation characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a focus voltage adjustment circuit for a negative 8II ray tube (hereinafter referred to as CRT), and particularly to a focus voltage adjustment circuit for adjusting the focus voltage of a magnetic field focusing type CRT. Related to voltage regulation circuits.

[Conventional technology]

Conventionally, as a magnetic field focusing type CRT, one having an electrode structure consisting of a cathode K, a first grid G1, a second grid G2, and an anode A is known. This kind of CRT
In -/[2, a control signal such as a video signal is input to the first grid G1, to the cathode K, and to the anode A.
For example, the circuit is configured to apply the anode voltage generated to the secondary winding of the flyback transformer.
On the primary side of the flyback transformer, a horizontal drive pulse is supplied to drive the deflection yoke, and at the same time, during the horizontal retrace period, the flyback pulse resonated by the resonant capacitor and the deflection yoke is applied to the primary winding of the flyback transformer. By supplying the voltage, the circuit can be configured to generate the required anode voltage in the secondary winding.

However, in this type of CR,T'', it is generally adopted to apply a horizontal retrace pulse to the low voltage part of the high voltage winding in order to keep the high voltage constant; , the focus voltage taken out from the middle tap of the high-voltage winding tends to fluctuate.

Therefore, in this case, in order to obtain the optimum focus point of the CRT, methods have been proposed in which, for example, the flyback pulse width of a flyback transformer is varied or the power supply voltage is varied.

[Problem to be solved by the invention]

However, the former method of varying the flyback pulse width has the disadvantage that not only is smooth adjustment not possible because the voltage to be handled is generally high, but also the adjustment range is not sufficient. Also, according to the latter method of changing the power supply voltage,
This not only causes power loss, but also causes variations in the deflection dimensions in the CRT, as well as changes in brightness, making it impossible to reproduce images properly.

In addition, the flyback pulse obtained on the primary side of the flyback lance is affected by the yoke in both directions, the resonant capacitor, the flyback transformer, etc., and the pulse width and peak value vary. 2
The anode voltage generated on the next side is also difficult to fall within the tolerance required for CRTs.

Therefore, an object of the present invention is to provide a DC voltage obtained by rectifying a part of the flyback pulse when the flyback pulse derived from the flyback 1 to lance is supplied as the cathode voltage and grid voltage of the cathode ray tube. By setting variably, the potential difference between the cathode voltage and the grid voltage and the anode voltage can be relatively variably adjusted, and adjustment of the ELM focus point can be easily achieved with a simple circuit configuration and without causing power loss. The purpose of the present invention is to provide a focus voltage adjustment circuit for a cathode ray tube.

[Means to solve the problem]

The focus voltage adjustment circuit for #e polar ray tube according to the present invention is as follows:
In a voltage supply circuit for a cathode ray tube configured to supply horizontal drive pulses to a flyback transformer and supply flyback pulses derived from the flyback transformer as cathode voltage, grid voltage, and anode voltage of the cathode ray tube, Fixing the DC load to the reference potential point of the first winding of the flyback transformer which generates the first flyback pulse supplied to the anode of the tube, and the second or second pulse supplied to the cathode and grid of the tube The present invention is characterized in that the cathode voltage and the grid voltage are adjusted with respect to the anode voltage by adjusting the reference potential point of the second or third winding of the flyback transformer that generates the three flyback pulses.

[Effect]

According to the focus voltage adjustment circuit for a cathode ray tube (CRT) according to the present invention, the anode voltage supplied to the CRT fluctuates due to fluctuations in the flyback pulse on the primary side of the flyback transformer, resulting in inappropriate focus adjustment of the CRT. In the case where By making the voltages derived from these windings adjustable, the cathode voltage and the grid voltage relative to the anode voltage can always be maintained at a proper state to easily obtain the optimum focus point of the CRT.

〔Example〕

Next, the cathode ray according to the present invention! An embodiment of a focus voltage adjustment circuit for a CRT (CRT) will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a main part showing an embodiment of a focus voltage adjustment circuit for a CRT according to the present invention. In FIG. 1, reference numeral 10 indicates a magnetic field focusing type CRT, and its electrode configuration includes a cathode K, a second grid G1, and a second grid G2.
and anode A. Reference numeral 12 indicates a flyback transformer, and the primary winding L1 of this lance 12 includes a transistor Tr for supplying horizontal drive pulses, a deflection yoke DY, a DC blocking capacitor C3, a resonance capacitor C2, and a damper diode. D is connected.

On the other hand, the secondary winding of the flyback transformer 12
is divided into a winding L7 and a second winding LII,
The first winding L7 includes a diode DIG and a bleeder resistor R. , a smoothing capacitor C1°, and a bleeder resistor R11. Also,
One end of the second winding 8 is grounded, and the other end is connected to a voltage rectifier circuit consisting of a diode D11 and a smoothing capacitor Cr+, and its output is applied to the anode A as an anode voltage. Note that the winding L3 is a heater winding for the cathode. In this case, the first winding L7 is a floating winding, fixing the intermediate tap of the bleeder resistor RIO to the required potential, while the bleeder resistor R11
The intermediate tap is configured to supply a cathode for brightness adjustment. Further, the circuit is configured so that the negative pole side of the rectified voltage applied to the bleeder resistor RZ is supplied as the first grid G1 voltage, and the JE pole side is supplied as the second grid G2 voltage. Furthermore, in this example,
A video signal is supplied to the cathode K of CRTIO via the coupling capacitor CI2.

〔Effect of the invention〕

According to the circuit of this embodiment configured in this way, the cathode K and the first grid G are connected by changing the position of the intermediate tag of the bleeder resistor R1° provided for the first winding L7.

Since the potential of the second grid G2 changes in parallel to the anode voltage, the relative potential difference between the anode voltage, the cathode voltage, and the first grid voltage can be changed to obtain the optimal value regardless of the brightness and modulation characteristics of the CRTIO. Focus voltage can be obtained.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various design changes can be made without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a focus voltage adjustment circuit for a cathode ray tube (CRT) according to the present invention. L,...Primary winding L3...Secondary winding L7...First winding (secondary 1III) L8...Second
winding (secondary 11'lIJ) Tr...transistor Dl...damper diode DY...deflection yoke C1...DC blocking capacitor C2...resonance capacitor Dl. +D11... Rectifier diode C,,,C,,
... Smoothing capacitor C12 ... Coupling capacitor R, , Rth ... Bleeder resistor 10 ... CRT 12 ... Flyback transformer

Claims (1)

[Claims] (1) In a cathode ray tube voltage supply circuit configured to supply horizontal drive pulses to a flyback transformer and supply flyback pulses derived from the flyback transformer as the cathode voltage, grid voltage, and anode voltage of the cathode ray tube. , fixing the DC load to the reference potential point of the first winding of the flyback transformer which generates the first flyback pulse supplied to the anode of the cathode ray tube, and the second or A cathode ray tube characterized in that the cathode voltage and the grid voltage are adjusted with respect to the anode voltage by adjusting the reference potential point of the second or third winding of the flyback transformer that generates the third flyback pulse. focus voltage adjustment circuit.