Chopper power supply for discharge lamp - has multi-winding transformer and switching transistor in switched capacitor reactive circuit

摘要

The low-voltage DC supply at positive and negative input terminals (5,8) is switched (6) to a buffer capacitor (20) and a first winding (2) of a step-up transformer (1). The second winding (4) supplies the discharge tube (18) via the reactive circuit (9) and base of the chopper transistor (7) which is in series with the first winding (2). The third winding (3) connects the DC input to the second winding (4) at its junction (E) with the reactive circuit. The base-emitter circuit of the chopper (7) detects the reactive signal and eliminates positive-going spikes. The operating frequency is adjusted by selective connection (11) of one of three capacitors (12-14) in parallel with a permanently connected capacitor (16) and resistor (15). The system is adaptable to hot- and cold-cathode tubes of different length and power.