HF voltage pulse supply for luminous discharge lamp - uses transistor based oscillator to generate HF pulse train with pulses having high transient initial peak

摘要

The voltage supply is in the form of voltage pulses having an initial overvoltage (4-0V to 900V) spike followed by an underVoltage (40V to 120V) period of greater duration than the spike. The pulse repetition frequency is between 20kHz and 200 kHz. The pulsed voltage supply is generated by a power transistor (Tr) based feedback oscillator powered by a DC supply, rectified (P) and filtered (C3) from the ac mains (A1-A2). The oscillator circuit has a high tension transformer (T) coupled between collector and base of the transistor, and has one electrode (3b) of the discharge lamp (1) in the emitter return path. The oscillations in the high tension transformer diary are coupled to the electrodes of the discharge lap. A photoresisto (R1) in the primay side is used to regulate the luminous output of the lamp.