Switching circuit for TV receiver - derives setting value from pulse voltage of isolating transformer primary in amplitude rectifier for protection of output voltage rise

摘要

The circuit has an isolating transformer (6), a periodically conductive switch, a feedback path (7, 16) derived from the transformer primary for the switch control, and a stabilising circuit (12) for output voltages. The circuit provides protection against heavy rise of output voltages (U1, U2). The protection is obtained by deriving a setting value (U5) from the pulse voltage on the primary side of the isolating transformer in an amplitude rectifier (14). If a threshold value has been exceeded, the setting value blocks the feedback path via an electronic switch (16) in series with the feedback path. The rectifier is preferably coupled to a coil (11), supplying the stabilising circuit.