A circuit and method for improving current sensing in a bridgeless PFC boost converter. Such a converter comprises a current transformer having first and second primaries; a boost inductor having a first end connected to a first AC input terminal and a second end connected to a first junction defined between the anode of a first diode and a first end of the first primary, the second end of the first primary being connected to a first terminal of the first switch; a second terminal of the first switch being connected to a common line; a parallel circuit of a capacitance and a load connected between the cathode of the first diode and the common line; a series circuit of a second diode, the second primary and a second switch connected between the cathode of the first diode and the common line; and a second AC input terminal connected to a second junction defined between the second primary and the second switch. A second boost inductor may be connected between the second AC input terminal and the second junction. The first and second switches may be MOSFETs. The circuit also includes a rectification circuit on first and second secondaries of the current transformer, comprising a MOSFET and additional diodes.

A flyback ballast for fluorescent lamps is provided. A transformer is utilized to control the power delivered to the lamp. A first switch is coupled to the first winding of the transformer. A first filter is coupled to a second filter through a first terminal pair of a lamp. The second switch is coupled to the third switch through a second terminal pair of the lamp. A switching signal is provided to the first switch to control the power of the transformer delivered to the filters. A second switching signal and a third switching signal are provided to the second switch and the third switch respectively to control the power delivered to the lamp. No glow discharge is occurred during the preheating interval.