Dim the Lights: Problems with Lamp Current Control using a PWM Signal

IT IS THE STATE OF THE ART to drive a fluorescent lamp with a ballast that mainly consists of a high-frequency generator. High frequency, in this context, means a frequency that is substantially higher than the mains frequency. Most ballasts on the market are working at an operating frequency of about 50 kHz. It is common to realize the high-frequency generator with a half-bridge inverter. This inverter has an output waveform with a rectangular shape, and the operating frequency F0 is equal to the frequency of the oscillation of the half-bridge. The fluorescent lamp is connected to the output of the inverter via a matching network.