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 61000-3-2and the international standard IEC 1000-3-2.

The advantages of the presented digital solution over standard analog solutions can be summarized as follows:

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor

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Freescale Semiconductor M68HC08 manual Introduction, Benefits of this Solution
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M68HC08 specifications

Freescale Semiconductor, known for its innovative solutions in the field of embedded systems, developed the M68HC08 microcontroller family, which includes the MC68HC908QT2. This 8-bit microcontroller is engineered to meet the demands of diverse applications, including automotive, industrial, and consumer electronics.

The MC68HC908QT2 is designed around Freescale’s M68HC08 core, which is renowned for its efficient and reliable performance. This microcontroller integrates a powerful instruction set, enabling developers to create high-performance applications with relatively low power consumption. The device operates at a clock frequency of up to 3 MHz, which is adequate for various control tasks.

One of the key features of the MC68HC908QT2 is its memory architecture. It includes a 2 KB Flash memory for program storage, representing a significant advantage for developers requiring non-volatile memory. Additionally, it encompasses 128 bytes of EEPROM memory, allowing for data retention even after power loss. The microcontroller also has 256 bytes of RAM for efficient data manipulation during operation.

In terms of input/output capabilities, the MC68HC908QT2 supports a variety of interfacing options. The microcontroller features up to 20 general-purpose I/O pins for flexibility in connecting with peripheral devices. Additionally, it provides multiple analog-to-digital converters (ADC) and timers that facilitate efficient analog signal processing and precise control through timing functions.

The architecture of the MC68HC908QT2 also incorporates sophisticated on-chip peripherals, enhancing its functionality. These peripherals include PWM (Pulse Width Modulation) outputs, which are essential for applications requiring motor control and other precise duty cycle processes. The integrated watchdog timer ensures reliable operation by resetting the system in the event of an application failure.

Moreover, the MC68HC908QT2 is equipped with an efficient power management system, enabling operation in a low-power mode, ideal for battery-powered applications. This microcontroller is packaged in a compact 28-pin dual in-line package (DIP), making it suitable for space-constrained designs.

In summary, the Freescale Semiconductor MC68HC908QT2 microcontroller is distinguished by its robust performance, extensive memory options, and versatile I/O capabilities. Its advanced features, including built-in timers, ADC, and a power management system, make it an exceptional choice for developers seeking to implement reliable and efficient embedded solutions. With its comprehensive architecture, the MC68HC908QT2 remains a popular choice in the landscape of 8-bit microcontrollers.
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