Flame monitoring circuit for gas burner

摘要

The circuit uses the temperature-dependent resistance variation in a glow plug (GL) for indicating the presence of the flame. The glow plug is inserted in a self-balancing bridge circuit (R1,R2,R3,GL), with the size of the current required for balancing the current through the glow plug used as the flame indication signal. The bridge circuit may be coupled to the current supply lines (PS1,PS2) via a controlled resistance (Q), controlled by the voltage across the bridge diagonal.