Control circuit for electric blanket or heater - has two electronic switches, clock pulse generator controlling second switch, and resistive voltage divider in specified connection

摘要

The circuit has a temp. control for the heat conductors, an electronic switch in series with the conductor at operational voltage, and a clock pulse generator for periodical making and breaking of the switch. The actual value generator for the temp. control is the heat conductor proper, the control incorporating a memory, as in 2757334. Parallel to the switch (S1) is a series connection of a bridge resistor (R4') and a second electronic switch (S2) controllable by the clock pulse generator (TG). A voltage divider (R1,P1,R2) is in parallel to the series connection of the heat conductor (RH) and the bridge resistor (RH') for generating a rated value voltage. The clock pulse generator closes the second switch only during the breaking of the first switch, and then only for a brief measuring interval. The bridge resistor and voltage divider may be coupled to both ends of a potentiometer (P2) to whose tap is coupled the second switch.