POWER SOURCE PROTECTIVE CIRCUIT

PROBLEM TO BE SOLVED: To reduce the influence of the load of a small DC power receiving circuit when the load short-circuits or the load is heavy on a power supply source in a circuit which protects a power source when the load becomes abnormal. SOLUTION: In a breaking circuit 4 which connects a power supply source to a load 1A, a capacitor C1 is fully charged after a solid-state relay SSR1 is turned on by making the primary-side current i1 of the relay SSR1 to flow for a period of time longer than the operating time of a rush current suppressing circuit 2 at the time of turning on the circuit 2 when the power supply source is turned on while the capacitor C1 is fully discharged and, when the power supply source is turned off while the capacitor C1 is fully charged, the relay SSR1 is turned off and, at the same time, the capacitor C1 is fully discharged. When a load 1A short-circuits or the load 1A becomes heavy while the power supply source is turned on, the relay SSR1 is turned off so as to disconnect the load 1A and, at the same time, to prevent the discharge of the capacitor C1 by using the current in the charging route of the capacitor C1.