| Ultra-brightness white LED used as environmental protection lamp is a potential product can replace current competitors. The driver of white LED with best efficiency, good reliability and low cost is in need to satisfy the significant amout market of commercial and home application. There are large scale power management chip as boost transformer applied in portable equipment such as cell phone, laptop. Switch method power supply system has won the low dropout regulator in efficiency and wide application range.This paper illustrates the related characteristics about DC-DC transformer system and designs the top module according to the requirement of general illumination usage. The solution includes two parts, the one is switch transistor and the other is gate driver parts. A varied buffer layer under the collector is used to release the curvature effect and stop switch from breakdown early. It presents structure dimensions and doping profile as well as performance parameters after simulation using TCAD tools.In this thesis, Design of DC-DC control system is the most important work. This system makes use of pulse width modulation to realize the constant current output. The intelligent module samples the current signal from the resistor seried with load and current through power switch. The top module can monitor the temperature and overvoltage. Bandgap, Error amplifier, PWM comparator, thermal shutdown module are included to complete the function just as my pre-defination. All circuit cell designed in this paper are simulated based on 0.35μm 18V highvoltage technology and detailed results are followed.
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