Demagnetisation appts. including AC control relay and driver circuit - cuts off AC from demagnetising coil when driver transistor is blocked by rise of DC voltage on charged capacitor

摘要

The DC output of a rectifier (1) is smoothed by a first capacitor (C1) and applied to a charging circuit (3) comprising a resistor (R1) and a second capacitor (C2). The demagnetising coil (DE) in series with a PTC resistor (Ra) is switched by a relay (4) whose driver circuit (5) is based on a transistor (Q1) switched by the voltage on the second capacitor. The transistor is blocked when the PTC resistance increases after the lapse of 1 or 2 seconds from closure of the AC supply switch (SW1). USE/ADVANTAGE - In TV receiver or video monitor, current consumption is reduced and overheating is avoided.