| 摘要 |
PURPOSE:To enable a power source to be exactly turned OFF, by feeding sufficient base current to a control transistor through the current source of DC voltage from a detection winding, when a switching element is communicated with. CONSTITUTION:Between a connected intermediate point D between starting resistance R4', R4'', and the obtaining point E of DC voltage from a detection winding N3, a pair of reverse-current-checking diodes D12, D13 are connected in series in the mutually reverse directions. Between the cathode K connected in common and the base of a control transistor Q2, the collector and emitter of a light-receiving transistor Q4 in photocoupler PC for a switching element for a power source-ON/OFF are connected in series via a current limiting resistance R13. When the light-receiving transistor Q4 is communicated with, then sufficient base current is fed to the control transistor Q2 through the current source of DC voltage from the detection winding N3, and a switching transistor Q1 is turned OFF.
|
