| 摘要 |
1. Proximity, respectively presence detector apparatus of the two terminal type supplied by a rectified A-C current (e1 , e2 , D4 -D7 ) for controlling a load (CH) series-connected to said apparatus and comprising : a sensor-control circuit unit (CAP) ; at least a first thyristor (TH1 ) and a Zener diode (Z2 ) series and oppositely connected, the gate of the first thyristor (TH1 ) being connected to the output of the sensor-control circuit unit (CAP) making the first thyristor (TH1 ) conductive or not, for controlling the charge (CH), said unit being supplied by said rectifying means at the terminals of the Zener diode Z2 or across a first resistor (R3 ) depending on the first thyristor (TH1 ) being conducting or not ; and a first capacitor (C1 ) connected in parallel to the Zener diode (Z2 ) and serving as a supply source for the said sensor-control circuit when minimum intensities of rectified current are flowing through the apparatus, characterized in that it contains protection means comprising a semi-conductor high gain component (T3 ) series-connected with the first thyristor having an input (D) and a power output (S) and at least one control input (G), a transistor (T2 ) connected in parallel between said control input (G) and the output of said semi-conductor component (T3 ) in such a way that the said transistor (T2 ), normally not saturated, becomes saturated when an overload or a power short circuit occur and that the saturation of said transistor (T2 ) leads to the locking of the semi-conductor component (T3 ) and thus to the current limitation (by R7 and R8 ) in the first thyristor (TH1 ). |
