Self-activated switch power supply apparatus

The invention publishes an self-excitation type power switch installment, including: the vertex 207 in the primary coil ST1 the vertex 201 connects the power source CN1, collecting electrode of the primary coil ST1 the vertex 202 connects the triode DQ9, the base electrode of the triode DQ9 through the resistance R52, resistance R54, the forward feedback end 203 which the electric capacity C61 contacts the connection tickler ST2, resistance R52, vertex 207 which the common end of resistance R54 through resistance R12 connects power source CN1, the emitter electrode of the triode DQ9 through resistance R55 connects the negative feedback end 204 of the tickler ST2 and vertex 208 of the power source CN1, the base electrode of triode DQ601 through resistance R501 connects the emitter electrode of the triode DQ9, the collecting electrode of triode DQ601 through resistance R503 connects the base electrode of triode DQ9, the emitter electrode of triode DQ601 connects the vertex 208 of the power sourceCN1. Because this invention may prevent switch triode DQ9 from appearing the overfull phenomenon to affect its service life, even damaged, has guaranteed the entire electrical power unit works with security, highly effective.