White Led Driver Circuit In The Portable Product Design

The current market of power management products is growing up very fast all over the world, especially in china. The driver of the white LEDs for display backlighting becomes one of the fastest growing kinds of power management products with the wide use of portable facilities.This dissertation designs a current mode switching regulator used in driving white LEDs for display backlighting of variety of portable facilities. The outside of this chip adopts BOOST structure to drive up to seven white LEDs with the input voltage ranging from 3V to 5V. Series connection of the LEDs provides identical LED current resulting in uniform brightness. The output current is adjustable from OmA to 20mA. Connecting with different peripheral devices, the circuit can also have the functions of short circuit protection, soft start and four kinds of dimming control. With careful design and the support of the process, the circuit can be accomplished within only tens of transistors, the standard CMOS process and the typical devices are available. Thus its size is small meanwhile its efficiency gets enough guarantee.In the dissertation, the author firstly introduce the application, development and future of power management products, especially white LEDs driver, specify the theory,basic structure and advantages of the current mode switching regulator and its slope compensation. The design of the whole chip topology and the application circuit is carried out at the request of the specific use and the circuit introduces the typical structure of current mode PWM controller to seven sub-blocks. Then the topology of every sub-block are analyzed and the relative important parameters are calculated.Every sub-block has been simulated by Hspice with a standard CMOS process model provided by a famous foundry to ensure meeting the requirement at different supply voltage and temperature.The circuit will be taped out through the standard CMOS process, four kinds of devices are available:vertical PNP,PMOS,NMOS,resistor and capacitor.Some informa -tion about the process and the devices are given in chapter 4, in which some notes about the layout are also presented.