Control circuit for controlling power supplied to an igniter element and igniter system

PCT No. PCT/EP97/00478 Sec. 371 Date Apr. 3, 1998 Sec. 102(e) Date Apr. 3, 1998 PCT Filed Feb. 3, 1997 PCT Pub. No. WO97/29932 PCT Pub. Date Aug. 21, 1997A control circuit (52) for controlling power supplied to an igniter element (54), includes a first input (70) for receiving an encoded input signal generated in response to the initiation of a firing mode and a diagnostic mode. The encoded input signal comprises a code portion (100) having at least two pulses, and a power portion (102). Logic circuitry (74) determines whether the code portion (100) is valid, the code portion (100) being determined valid when it meets predefined conditions within a predetermined time window, and provides an unlocking signal (Sfire) at an output (76) when the code portion (100) is determined to be valid. A switch (78), which has a control input coupled to the output (76) of the logic circuitry (74), is enabled on receipt of the unlocking signal so that power at the first input (70) of the control circuit (52) is supplied to the output of the switch for energizing the igniter element (54). In the firing mode, the power supplied via the enabled switch is sufficient to fire the igniter element (54). In the diagnostic mode, the power portion supplied via the enabled switch energizes but does not fire the igniter element (54) such that diagnostics can be performed.