The temp. control circuit has a pulse generator (8) producing the triggering pulses for the tyristor (Thy) or triac, etc. that connects the heating element to its ac supply. The thyristor is shunted by a series circuit comprising a first capacitor (C1), a resistor (R5) and a second capacitor (C3). - The first capacitor is shunted by a zener diode (D3) in series with two diodes (D1, D2). The temp. dependent resistor (Rt) is in series with a fixed (R2) and a variable (R1) resistor across these two diodes. The pulse generator's input is connected to one end of the temp. dependent resistor. The advantage lies in fewer components and greater reliability.
展开▼
