Abstract: A protection circuit for a transistor switching regulator type power supply which prevents damage to the regulating transistor upon initial application of power to the system. The normal feedback control signal pulses used to control the "on-time" of the regulating transistor are combined with second control signal pulses whose pulse width increases as a function of time during a predetermined interval such that the regulating transistor will initially conduct for an extremely short period of time, but for longer and longer periods as time preogresses until the output voltage from the regulator circuit is within the regulation band provided by the normal feedback control circuit.