A High-Efficiency RF Suppression Circuit for Fluorescent Lamp Inverters Using Charge Pump and Partial Smoothing Capacitors

Abstract

A highly efficient RF suppression circuit for a fluorescent lamp inverters is proposed based on charge pump and partial smoothing capacitors. The circuit consists of a pumping capacitors, a partial smoothing capacitor and a control switch. The pumping capacitor is of comparatively small capacitance and the control switch operates to ensure that the pumping capacitor charging current is proportional to the AC power supply voltage even across the interval when the AC voltage is near zero. Effective use of current charging reduces the RF harmonic components in the supply current and improve the power factor. The charging voltage of pumping capacitor (VCp) and the charging voltage of partial smoothing capacitor (VCh) are responsible for the inverter drive of the lamp circuit. When the lamp starts, the control switch provide the high voltage of VCp+VCh. After the lamp has started, VCp and VCh are switched in alternately. During the period that the partial smoothing capacitor is charging, the time constants of the choke coil at the rectifier circuit input and the partial smoothing circuit are optimized, while use of the charging voltage of the pump capacitor prevents sudden appearance of a charging current at the input. Test circuits exhibited a power factor of 97.4% (well above the 85% rating), and 3rd to 11th harmonics about half of the rated values, demonstrating the feasibility of a high-power-factor, low-RF inverter.