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Dimmable Light Ballast with Power Factor Correction, Rev. 1
Freescale Semiconductor 7
Chapter 1
Introduction
1.1 Introduction
This reference design describes the design of a fully digital dimmable light ballast with power factor
correction (PFC) control for two parallel connected fluorescent lamps.
This reference design focuses on the lamp ballast hardware and software implementation using the
Freescale MC68HC908LB8 microcontroller (MCU), which is designed specifically for light ballast
applications. This MCU includes a set of peripherals that are appropriate for light dimming and power
factor correction.
The reference design incorporates both hardware and software parts of the system including detailed
hardware descriptions and full software listings. The application uses half-bridge topology, typical for this
kind of applications. The MC68HC908LB8 MCU is well suited to this topology.
Figure 1-1. Dimmable Light Ballast with PFC Demo
1.2 Benefits of this Solution
Microcontrollers offer the advantages of low cost and attractive digital light ballast design. Using a
dedicated on-chip high resolution PWM (HRP) allows easy implementation of dimming features. PFC
improves the efficiency of the light ballast. Harmonic content of the input current for the mains supplied
equipment meets the European regulation
EN 61000-3-2 and the international standard IEC 1000-3-2.
The advantages of the presented digital solution over standard analog solutions can be summarized as
follows: