Deflectional system for a television set comprising a power transistor

US4645986A · kind A · utility

Assignee

• SGS Halbleiter-Bauelemente GmbH · DE

Inventors

• Joachim Melbert · Deisenhofen, DE
• Eduard Sawicki · Munich, DE

Key dates

• Filing date: May 30, 1985
• Grant date: Feb 24, 1987
• Expiry date: May 30, 2005

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03K4/64
• WIPO field: Basic communication processes
• WIPO sector: Electrical engineering

Abstract

The invention relates to a deflectional system of a television set comprising a power transistor and a driving circuit which supplies a deflection current increasing in ramp-shaped manner to a deflection coil. The driving circuit is periodically fed with switching-on pulses of a duration corresponding to the ramp length of the deflecting current. The driving circuit applies an increasing switched-on base current to the power transistor during the switching-on pulse duration, said switched-on base current driving the power transistor into the saturation state during substantially the entire switching-on pulse duration. After termination of the switching-on pulse, the driving circuit controls the power transistor with a switching-off base current which rapidly decreases in relation to the increase of the switched-on base current and finally changes polarity and which effects a rapid return of the power transistor from the saturation state into the blocking state. The power transistor has a sensor means associated therewith which supplies to the driving circuit an actual-value signal which is proportional to the instantaneous value of the transistor main current. The driving circuit r…