Electric circuit for warming device, esp. blanket - has measuring switch with opening intervals short w.r.t. half-wave period of operating AC voltage

摘要

The circuit is particularly intended for electric blankets and similar devices and has a temp. control circuit for the blanket heating conductor. An electronic measuring switch and a clock pulse generator are in series with this conductor. When operated with alternating voltage, the opening intervals of the measuring switch (S2) are short in comparison to the half-wave period of the operational voltage, lying in the voltage peaks. The clock pulses, opening the measuring switch, appear max. in each second half-wave. Parallel to the switch is a measuring resistor (RH'), while a bidirectional switch (S1) is in series to this parallel element and to the heating conductor (RH). This switch forms a setting element for the temperature control circuit. It is controlled by an ignition signal generator (ZG), in turn controlled by the clock pulse generator (TG), in addition to a memory (G2,G3).