TRANSISTOR COMMUTATOR Russian patent published in 1999 - IPC

FIELD: electronic engineering. SUBSTANCE: transistor commutator has composite transistor switch built around two transistors; first transistor base is connected to device input through current-limiting member and second transistor emitter is connected through current sensor to first bus of power supply. Transistor collectors are connected to second bus through switching circuit. Commutator incorporates transistor optocoupler whose light-emitting diode is inserted between base of second transistor and first bus of power supply. Commutator has two intercoupled feedback circuits. Circuit for coarse shaping of transistor switch load current limiting level is controlled by optocoupler light- emitting diode. Circuit for fine shaping of current limiting level is controlled by phototransistor. Since light-emitting diode and phototransistor are optically coupled, slight variations in current flowing through light-emitting diode occurring during load current limiting causes considerable variations in feedback circuit due to high gain of transistor thereby shaping stable load current limiting threshold (level). EFFECT: improved stability of load current limiting level. 1 dwg