Pioneer Electronic Corporation

Katsumi Ishikawa

Nobuhiko Saegusa

Akio Ozawa

A circuit for generating a dc high voltage supplied to an anode of a cathode-ray tube, having a simplified circuit structure and reduced size. A first horizontal deflection circuit applies a first flyback pulse across the primary coil of a flyback transformer, while a second horizontal deflection circuit supplies a second flyback pulse to a lower voltage side of the secondary coil of the flyback transformer through a coupling capacitor. A dc voltage supplied to the second horizontal deflection circuit is controlled in response to the output voltage of the secondary coil of the flyback transformer. A current detection circuit for automatic brightness limiting is coupled to the lower voltage side of the secondary coil of the flyback transformer for detecting changes in the secondary current of the flyback transformer.

High voltage generating circuit

A Schmitt trigger circuit including transistors Q12 and Q13 having a common emitter resistor R3 is thermally coupled to a power amplifier A in a monolithic IC chip, and the base of Q12 is biased at a cutoff potential under normal operating conditions. When the temperature rises to a first predetermined level V.sub.BE of Q12 drops below its biasing potential owing to the temperature characteristic of Q12, whereby Q12 conducts, which cuts off Q13 and, through transistor Q14, disables the amplifier. The common emitter feedback provides a thermal hysteresis characteristic, whereby Q12 is not cut off again until the temperature drops below a second predetermined level.

Growing community of inventors

Tokyo, Japan

Katsumi Ishikawa