| 摘要 |
PURPOSE:To simplify circuit constitution, and improve economy by detecting a lamp current, and controlling a power switch element of a voltage resonance type inverter through a voltage resonance type switching power control circuit. CONSTITUTION:A lamp current of a metal halide lamp L is detected as a voltage through a resistance current detecting resistor RD, a diode D12, a capacitor C11, etc., to be supplied to an operational amplifier OPA of a resonance type switching power control circuit IC1. On/off frequency of a power switch element FETQ1 of a voltage resonance type inverter is controlled through a VCO, a pulse frequency modulator PFM, etc., to set the frequency lower as the lamp current is lower, a primary current at a boosting transformer T1 is increased compared with that at the time of stationary action where a discharge current is sent through the lamp L, and the lamp L1 starts glow discharge. By this constitution without requiring a DC-DC converter, a high brightness discharge lamp lighting device of simple circuit constitution and improved economy can be provided. |
