A Highly Efficient Four Mould Design And Analysis Of The Led Driver

These years have witnessed the rapid development of white LED driver in the market of power management IC. White LED is widely used as high quality backlight light source in portable electronic products. The white LED chips driven by charge pump will have the advantages of Low electromagnetic interference (EMI), small PCB plate area and low cost。 Meanwhile, when development direction of the new charge pump circuit is improving the output current capability, reducing the output resistance and improving the efficiency of LED, charge pump circuit will become a popular solution of LED drives. There are mainly two structures of white LED driver, charge pump based on capacitor and switching power supply based on inductor.Unlike the traditional charge pump structure, the paper adopted1X/1.33X/1.5X/2X four mode fractional adaptive charge pump, with the change of input voltage which can automatically convert working mode. This structure tremendously enhances the efficiency of charge pump and thus prolongs the using time of batteries.In this thesis, the theory about the driver and the circuit diagram are introduced firstly. Then the charge-pump technology and its efficiency are discussed, the1.33X mode are proposed, and some methods of LED constant current driving and brightness regulating are analyzed. The five sub-blocks, including the bandgap reference circuit, the current mirror, the operational amplifier, the oscillator and the over-temperature protection circuit are designed respectively. The whole chip functions and the key performances are simulated and the results show that the LED driver has achieved the design specification.