Stabilized high voltage generation circuit for cathode ray tube

Details Stabilized high voltage generation circuit for cathode ray tube Stabilized high voltage generation circuit for cathode ray tube

1997-11-17

1999-09-14

Westin, Edward P.

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Power supply from deflection circuit source

315386, H04N 3185, G09G 104

Patent

active

059527951

ABSTRACT:
A high voltage generation circuit incorporates the horizontal circuit of a cathode ray tube (CRT) monitor. The horizontal circuit comprises a horizontal output transistor, a retrace capacitor coupled in parallel with the horizontal output transistor, a damping diode which clamps the minimum voltage at the drain of the transistor to approximately ground potential, and a flyback transformer. The primary winding of the flyback transformer is coupled between a terminal where a DC power supply B+ is applied and the drain of the horizontal output transistor. A second transformer is provided between the retrace capacitor and the ground for producing a voltage at the secondary winding thereof each time a free oscillation occurs between the damping interval Td of the damper diode and the conduction interval Ton of the horizontal output transistor. A diode is also provided for rectifying the voltage produced at the secondary winding of the second transformer, and thus the energy stored in the retrace capacitor is returned to the power supply B+ as a return current. Further included is an error detector for comparing a DC voltage detected at the secondary winding of the first transformer with a reference voltage to produce an error detect signal; and a pulse width modulator for supplying a pulse-width modulated signal to the base of the horizontal output transistor, causing it to perform a switching operation in response to the error detect signal fed from the error detector. Preferably, the second transformer has a predetermined turns ratio between the primary and secondary windings thereof such that the voltage at the secondary winding may be such as to allow the diode Drg to be in the cut-off region at the discharge of the retrace capacitor if the retrace capacitor Cr is charged to a value more than one-half of the supply voltage.

REFERENCES:
patent: 5016156 (1991-05-01), Ogawa
patent: 5317495 (1994-05-01), Furukawa
patent: 5625261 (1997-04-01), Ogawa
patent: 5627437 (1997-05-01), Kim
patent: 5699236 (1997-12-01), Choi
patent: 5796218 (1998-08-01), Kwon et al.

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