Design Of Electronic Ballast For 150W Metal Halide Lamp

With the global shortage of non-renewable energy resources, energy saving and consumption reduction have become the major concerns in the industrial development of China, even the whole world. As the third generation of green light source, Metal Halide Lamps (MHL) has the advantages of high luminous efficiency, good color rendering, long life and so on, making it an important role in the green lighting project. However, the traditional inductance ballast, configured with MHL, has the shortcut of high energy consumption, low efficiency, bulky and so on, and it can not meet the requirement of green lighting. Thus, the electronic ballast is becoming a hot research of development for its energy-saving, portability etc.In order to restrain the distinguished"acoustic resonance phenomenon"characteristic of MHL, and settle the compatibility problem of the electronic ballast, this paper adopts a three-level structure, Active Power Factor Correction(APFC), Constant Power Control and Low-Frequency Square-Wave-driven. In the first stage, APFC, the 220V AC electricity goes through the EMI, RFI filter, and after rectification it goes through the APFC circuit controlled by the critical conduction mode L6562, which achieves 170V~260V wide voltage range input, power factor increased to 0.985, and total harmonic distortion decreased to 9.1%. In the second stage, Constant Power Controlling, the buck topology is used, which is controlled by, both the 8-bit low-cost PIC microcontroller and current-mode pulse-width modulation (PWM) chip UC2843, to realize the smoothing start and precision Constant Power Control of MHL, which combines the advantages of near-constant power control and constant current control method. Meanwhile, the microcontroller is used to realize the self-protection when the electronic ballast is open, short circuit, start failure and lamp preburning, thus, improves the reliability of electronic ballast. The third stage is full-bridge inverter and high-voltage ignition functions; a 350Hz low-frequency square-wave drive is adopted to avoid the "acoustic resonance phenomenon." Using the pulse ignition means, the high-voltage ignition circuit generates the high-voltage pulse through bi-directional trigger and the step-up transformer. The ignition circuit fails after the ignition of HML.At the test of the electronic ballast prototype of 150W MHL, the waveforms of key points are collected and analyzed. The test results indicate that the electronic ballast of MHL works stably, and has a constant output power, the power factor more than 0.98, and efficiency more than 85%.