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Lighting energy consumption has been in the account for a large proportion of the energy consumption. Growing resource and environmental problems, the end of the twentieth century, countries have launched a the semiconductor lighting scheme. Its main contents are used in road and building efficient lighting electrical products, lighting more scientific, comfortable, safe and reliable, and at the same time to achieve the role of energy-saving lighting. High Power White LED power supply as a key supporting industries of the semiconductor lighting industry has become a hotspot for the power management chip market. Proposed a very high requirements of the switching power supply, in particular LED dedicated power supply, including in greater input voltage range can provide a stable output voltage, and to work at high efficiency in the full load range, and smaller, more power density higher. The design of this project a high-efficiency, high input voltage, output current constant high-power white LED driver circuit, the circuit's input voltage range of 8V-40V, output current of 350mA. The circuit uses a monolithic integrated bipolar high voltage process tube Bipolar, CMOS and DMOS devices, namely BCD process. The circuit uses a power tube built structure, the control mode and the modulation mode, respectively, using the current control mode and the PWM modulation method, thereby improving the conversion efficiency. The paper focus on chip circuit op amp circuit, bandgap reference circuit input voltage pre-adjustment circuit, sawtooth generator circuit switching MOS transistor drive circuit design. Operational amplifier uses two op amp gain of 95.5dB; bandgap reference voltage source drift coefficient down to 30ppm / ℃, input voltage pre-adjustment circuit chip internal circuit provides a stable 5V and 15V operating voltage . Subsequently, the multi-value of the bias circuit, the comparator circuit, the error amplifier circuit, and output overvoltage protection circuit, the overheat protection circuit, a logic control circuit, such a design. Switch MOS transistor built-in makes the integration of peripheral circuits increases, BCD process so that the input voltage range increases. Built-in overheat protection circuit, over-voltage protection circuit, low voltage lockout circuit, not only to improve the integration of the chip, the chip in a non-normal state to automatically shutdown, protect the chip but also to prevent the destruction of the LED . On the basis of each unit module are successful simulation and circuit Global Simulation, the conversion efficiency of more than 90%, and within the range of -50 ° C to 150 ℃, fluctuations in the output current of 1%. When the output voltage reaches 40V, the overvoltage protection can be effectively achieved. The simulation results show that the design of the circuit to achieve the expected requirements.
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