Automatic burner ignition circuit for through-flow water heater - uses switched constant current source supplying feed valve energising magnet

摘要

The burner ignition circuit, provides opening of the magnetic valve inserted in the fuel feed line for the burner, via an opening current circuit (41), with the valve held open via a holding current circuit (42), both circuits (41, 42) coupled to the magnetic energising coil (SP). The coil is supplied via a switched constant current source (43) incorporated in a bridge circuit (Br). One arm of the latter has a resistor (R1) is series with a Zener diode (d1), a second arm containing a safety switch (F), the valve coil (SP), the collector-emitter path of a transmitter (F1) and 2 series resistors (R2, R3). ADVANTAGE - Unaffected by amplitude variations of supply voltage.