High Frequency Full Digital Dimming Ballast for a Compact Lamp
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This paper proposes a full-digital dimming ballast with a dedicated Digital Power Controller (DPC) having a driving frequency of 200 to 400 KHz with a digital control method. The DPC has Digital Pulse Width Modulation (DPWM) of 8 or 12 bits resolution, as well as a typical microcontroller feature including a sampled 8-bit A/D converter with an internal programmable memory. The variable frequency is used to drive the series-resonant network with a compact fluorescent lamp. By changing the driving frequency, the lamp can be preheated for accurate pre-heating time. A 32W power compact fluorescent lamp from GE lighting is tested with a running frequency of 200 KHz for maximum power and a pre-heating frequency of 400 KHz without any passive components for setting pre-heating or driving frequencies. The full digital ballast is implemented with a dedicated digital power controller (DPC). Without any external R and C, the pre-heating time and various driving frequencies can be programmed and adjusted according to an operating condition for a best lamp control. In addition, the driving frequency is increased up to 400 KHz with 8-Bit resolution so that the series inductor of 330 uH and resonant capacitor of 1.5 nF are used. The experimental results are provided.