The process of energy transferring from the magnetic coil to the discharge plasma can be considered as a model of a transformer. The magnetic coil is equivalent to the primary winding and the magnetic lamp bulb is equivalent to the secondary winding. The inductively coupled discharge is maintained by high frequency voltage built in the induction bulb.
The high frequency generator (always called electronic ballast or driver) is made of four main parts. First is an EMI filter to reduce harmonics from the supply of alternating current. The second part is a bridge rectifier, this converts AC to DC power. After that is the PFC circuit which boosts the DC voltage to a constant 400V value and increases the power factor to 0.95+ efficiency.The last part of the ballast is an inverter which converts the DC power to high frequency AC.
The highlight of this ballast is the application of IC chip controlled improving the performance of the total system. The inverter is controlled by the IC chip providing driving signals controlling the frequency. Since the lamp power is inversely proportional to the operation frequency when the voltage is constant, lamp power changes with the changes of operation frequency so that the dimming could be achieved. With controls, 30%~100% dimming range can be achieved without negative effects on the lamp. PFC is controlled by IC chip which guarantees the induction lamp to work properly from wide voltage range with PFC than 0.95. This advantage benefits the application of high rate of fluctuation of power supply.