Control Theory

Figure 2-1. Typical Low Pressure Fluorescent Tube I/V Characteristic

The value of Vstrike is a function of several parameters:

•Gas filling mixture

•Gas pressure and temperature

•Tube length

•Tube diameter

•Temperature of electrodes: cold or hot

Typically, values of Vstrike are in range 500 V to 1200 V. Once the tube is on, the voltage across it drops to the on-state voltage (Von), the magnitude of this voltage being dependent upon the characteristics of

the tube. Typically, Von is in range 40 V to 110 V.

The value of Von will vary during the operation of the lamp but, in order to simplify the analysis, we will assume, as a first approximation, that the on-state voltage is constant when the tube is running in steady state.

Consequently, the equivalent steady state circuit can be described by two back-to-back Zener diodes as shown in Figure 2-2. The startup network is far more complex, particularly during ionization of the gas. This is a consequence of the negative impedance exhibited by the lamp when the voltage across its electrodes collapses from Vstrike to Von.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

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Freescale Semiconductor

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Freescale Semiconductor M68HC08 manual Typical Low Pressure Fluorescent Tube I/V Characteristic
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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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