Circuit for simulating characteristic of flashing direction indicators - alerts driver to malfunction of flasher unit irrespective of which of two alternative voltages of power supply is operative

摘要

A constant reference voltage of 1.8 V is applied to the emitter of a first transistor (T1) which in combination with a second transistor (T2) and resistance (R1) establishes a constant current (Ikonst) representing the invariant portion of the characteristic. The supply-voltage-dependent portion is represented by another current (I(Us)) from the emitter of a third transistor (T2) in a current-mirror configuration (T3, T4), part of whose collector load (R9) is shorted (T5) by a threshold switch or hysteresis comparator (TR) when the supply voltage (Us) is 12 V, but not when it is 24 V. USE/ADVANTAGE - In motor cars and utility vehicles, magnitude and slope of characteristic are same for both 12 V and 24 V supplies.