HALF-BRIDGE SELF-EXCITED OSCILLATOR Russian patent published in 1999 - IPC

FIELD: microelectronics; control systems for fluorescent and halogen lamps; secondary power supplies. SUBSTANCE: oscillator has power transistors connected to control circuits identical for top and bottom transistors of half-bridge which function to reduce dissipation power and to convert sine-wave voltage across transformer secondary windings to square-wave current conveyed to bases of power transistors as well as to actively cut off power transistors when they are turned off. In addition, at least bottom transistor of half-bridge incorporates overcurrent protective circuit for external control of its level; in case of overcurrent condition, protective circuit sends signal to disabling circuit which operates as thyristor and fully turns off power transistor; disabling circuit is reset at each half-cycle of self-excited oscillations inoperative for particular power transistor. EFFECT: reduced power loss and provision for controlling brightness of lamps. 3 dwg