Protected flashing indicator circuit - has dynamic feedback to multivibrator and power transistor to correct short circuit and incorrect load to lamps

摘要

The flashing indicator circuit has a multivibrator (1) driving a power transistor (40) through an operational amplifier (31). The power transistor in turn switches current to the lamps. The lamp signal (51) is also delivered to a stabilised protection circuit (50) which also receives an input (H) from the multivibrator. The protection circuit has elements (68) which are sensitive to the timing of the multivibrator and detect cases of overload, underload and short circuit. The output (69) from the elements is fed back to the multivibrator (71) and operational amplifier (70). The effect is to regulate the timing of the multivibrator and/or switch off the power transistor under instance of excess load. The protection circuit may also be used to illuminate warning lamps to indicate a fault.