Transistorised switch with series load connected to power supply - has voltage regulator and associated pair of series transistors, alternately switched by astable, to supply switch control circuit

摘要

The switch includes the control circuit (1) which is connected to the grid of the power transistor (T1) which may be switched in response to a detected (S) current overload. A voltage regulator (5) provides a steady control voltage, Vx, to two series diodes to provide a line voltage, Vc, to the control circuit. The transistor pair (T2,T3) lie between the ground, Vn, and the second line voltage, Vo, to the control. The oscillator (7) controls the grids of the pair so that they alternately block and conduct. When the first transistor (T2) conducts a first capacitor (C3) is charged. When the second transistor (T3) conducts the first capacitor, between the pair of transistors and pair of diodes, discharges to a second capacitor (C4) between the supply lines to balance the charges. ADVANTAGE - Low line perturbation of supply, using components with low capacitative transfer voltage.