A Kind Of White Led Driver Based On Charge Pump Design

As a new type of solid illumination, WLED has much characteristic, such as high efficiency, low pollute, and long life-span etc. It is regarded as the most promising illumination source by the market, especially in LCD back-light modules. It takes the mainstream up gradually, and the market of WLED drivers becomes more and more hot. The research of WLED drivers has great practical significance.This thesis first introduces the basic theory of light radiation of WLEDs, analysis of its characteristics and the theories of several driving modes. Meanwhile several modes of current controls, and the advantages and disadvantages of the serial connections and the parallel connections have been presented.The white LED lighting driver in this thesis is based on boost charge pump. The driver maintains the high efficiency by utilizing a x1/x1.5/x2 fractional charge pump over all of battery life. It supports up to 4 white LEDs with regulated constant current for uniform intensity. It supports up to 120mA output current. User can easily configure each LED current up to 30mA by an external resistor. Three digital inputs can be programmable to control each white LED On/Off. LED dimming can be achieved by applying a PWM signal to the digital control signals.In the part of system design, this thesis derivates BGR and Charge pump’s basic theory and characteristic in details, and gives the actual circuits to validate them. This thesis also presents the OSC, the LED drive circuits, and the voltage and heat protect circuits in details, and summarizes their advantages and disadvantages. Finally the simulation results havebeen given.This chip is produced by standard CMOS 0.6um process. The layout picture is shown at the end. The test results of sample chips indicate the design is valuable.