Reference Design

Table 3-1. Light Ballast Characteristics

Parameter

Unit

Value

 

 

 

Lamp Type

 

F18W/33

 

 

 

Input Power

W

8...31

 

 

 

Input Current

mA

40...290

(230VAC)

 

 

 

 

 

Preheat Output

kHz

86

Frequency

 

 

 

 

 

Preheat Output

Vpp

345

Voltage

 

 

 

 

 

Preheat Time

ms

900

 

 

 

Running Output

kHz

50...100

Frequency Range

 

 

 

 

 

Running Output

V

200...235

Voltage Range

 

 

 

 

 

Input AC Voltage

VAC

110V/60Hz, 230/50Hz

 

 

 

Ambient

°C

0.50

Temperature Range

 

 

 

 

 

Power Factor

 

0.94...0.99

 

 

 

Total Harmonic

%

5.2...24.6

Distortion

 

 

 

 

 

Output Ignition

Vpp

510

Voltage

 

 

 

 

 

3.3 Application Description

The system concept is shown in Figure 3-1. The system consists of:

Control board with MC68HC908LB8 microcontroller

Two fluorescent lamps

The MC68HC908LB8 MCU runs the main control algorithm. According to the dimming level potentiometer It generates output signals for the half-bridge inverter which controls the ballast circuit. It also controls PFC. The desired dimming value is set by the potentiometer, because the human eye is more sensitive at lower light levels. The input values from the potentiometer are converted using brightness linearization. The HRP uses a frequency control method for dimming. It incorporates hardware that allows dithering between two adjacent frequencies for smooth light level dimming.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

22

Freescale Semiconductor

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Freescale Semiconductor M68HC08 manual Application Description, Light Ballast Characteristics

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.