Design Of White LED Driver Based On Charge Pump

With the development of semiconductor materials, white LEDs are main selection of illuminating devices, and the market potential is enormous. It will bring about a new industrial revolution. But, because of constraints of LED product own performance and power supply voltage, We must use white light LED driver to provides a stable voltage control source and LED current size for it. So the white LED driver is used widely in the market of power management IC. There are mainly two structures of white LED driver, based on capacitor-charge pump and based on inductor-switching power supply. The two have respectively its advantages and disadvantages.A high-efficiency white LED driver based on charge pump was designed in this paper, which introduces the structure of charge pump to perform the conversion of rising input voltage, drives up three LEDs in parallel and keeps all LEDs with uniform brightness. The chip is mainly applied to the portable electronic products with the following features:0.5μm CMOS process; 2.7 to 5v input voltage range; the 1MHz fixed frequency;-40℃to +85℃operating temperature; soft-start, over current and short circuit protecting function.According to the request of the system design, the author analyzed the whole structure and working principle of the circuit, divided it into sub-circuits in terms of its different functions, introduced the basic theory of charge pump. In the parts of sub-circuits, the author analyzed and designed the following typical sub-circuits: OSC, ERROR AMPLIFIER, SOFTSTART, PROTECTING CIRCUIT, LOGIC CONTROL.Based on the finished analysis of circuit principle and design, the author simulated the functioning features and key parameters by the use of the simulating software of HSPICE.The simulating result shows that the desired functions and performance are achieved. Finally the layout is designed with Cadence virtuoso, which is verified by DRC and LVS.