'Switching circuit with on-off detection function and the main current detection function', 'on-off detection function and self-holding function and a switching circuit having a self-turn-off function', 'on-off detection function and the main current detection function switching circuit 'and' on-off detection function and self-holding function and a switching circuit having a self-turn-off function with the '

摘要

PURPOSE: To reduce on-voltage and energy loss caused thereby and to prevent a current for detecting on and off from affecting detection of a main current. ;CONSTITUTION: A switch 16 and a diode 10 are connected in series with each other, for example, and resistances 12, 13 and a DC power source 1 are connected in series with both ends of a switch 16 not via a diode 10, and the emitter junction of an NPN transistor 3 is connected in parallel with the resistance 13 and the emitter junction of an NPN transistor 4 and the diode 10 are connected in series with each other in the base forward bias direction of the NPN transistor 4. To keep the transistor 4 on, a DC power source 2 and a resistance 14 are connected in series between the emitter and base of the transistor 4 and when the main current of the switch 16 causes a forward voltage in the diode 10 the forward voltage is applied to the emitter junction of the transistor 4 via the diode 8 so as to turn the transistor 4 on and off. Therefore, an on/off detecting portion and a main current detecting portion are allowed to use the diode 10 in common so that the above purpose is accomplished.;COPYRIGHT: (C)1994,JPO&Japio