Electronic delay with protection against supply interrupts - has auxiliary delay working from separate power supply

摘要

The delay, holds off the supply Voltage to an integrated circuit or a power transistor for a preset time, which is controlled by a variable frequency oscillator and a counter. The delay circuit operation continues in spite of interruptions to its own power supply. The circuit recognises the supply removal and continues its count down. Where the supply is reinstated before some set time the original delay is maintained. If the reinstatement occurs after this set time the delay circuit waits for the reinstatement and continues its delay from then. The circuit consists of two delay blocks, the principal block (20) providing the basic delay is initiated by a single input signal. The second block (21) provides the supply interruption record and has its own independent supply (23) and a high stability oscillator (22).