Study And Design Of High-Power LED Driver Circuit

Lighting energy consumption always occupies large proportion in the energy consumption. For the growing serious problem of resource and environment, many nations introduced solid-state lighting one by one in the end of twentieth century. The main content of lighting plan is to introduce high efficiency lighting products in road and building, making lighting more scientific, comfortable, safe, reliable, saving energy. High-power white LED driver, as a crucial supporting part of solid-state lighting industry, has become the research hot spot of power management chip market.At present, many high of performances are required for switching power supply, especially for LED power, such as wider input voltage range, steady output voltage, and higher efficiency in the full load range, high power density, and smaller size etc. The driver circuit for high-power white LED with high efficiency, high input voltage, constant output current has been deigned in this dissertation. The input voltage of the circuit is from 8V to 40V, and the output current is 350mA. The circuit is constructed and designed by using high voltage process integrated bipolar transistor, with CMOS and DMOS devices. In order to improve conversion efficiency, the power MOSFET is built-in, the current control mode and the PWM modulation are used. The designs of operational amplifier, band-gap reference, input voltage pre-regulator, sawtooth generator circuit and gate driver for power MOSFET are mainly designed in this dissertation. The gain of op-amp up to 95.5dB; the temperature coefficient of band-gap is less than 30ppm/℃. The input voltage pre-regulator supplies 15V and 5V for other circuits. The sub-circuits such as, multi-valued bias circuit, comparator, error amplifier, output over-voltage protection circuit, over-thermal protection circuit, and logic control circuit are studied and analyzed in details.The power MOSFET built-in chip results in an increase in integration of periphery circuit. The input voltage range is improved by using BCD process. The over-thermal protection circuit, the output over-voltage protection circuit and the low-voltage shutdown circuit built-in not only make integrity increase, but also make chip automatically shutdown in the non-normal operation and protecting LED. Finally, the whole circuit simulation results by spectre are given, the efficiency is above 90%. And the output current fluctuation of 1% in the range -50℃to 150℃, and when the output voltage is high than 40V, the over-voltage protection begin to work. The simulation results show that the circuit designed can satisfy the anticipate requirements.