Based On The High Efficiency Charge Pump White Led Driver Circuit Design And Research

These years have witnessed the rapid development of white LED driver 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 four white LEDs in parallel with regulated constant current and keeps all LEDs with uniform brightness. The chip is mainly applied to the portable electronic products with the following features: 2.7v to 5.5v input voltage range; the 1MHz fixed frequency; -40℃to +85℃operating temperature; two digital inputs control on/off and select amongst three levels of brightness; thermal shutdown and under voltage shutdown protection, low 0.1μA shutdown current; soft-start limits inrush current.Unlike the traditional single mode of charge pump structure, the paper adopted 1x/1.5x fractional adaptive charge pump, which can automatically convert working mode with the change of input voltage, and utilized ultra-low-dropout current regulators to make 0.15V LED_ minimum regulation voltage in order to remain the charge pump working mostly in higher-efficiency 1x mode. This structure substantially enhances the efficiency of charge pump and thus prolongs the using time of batteries.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 and then laid out the structure of adaptive 1x/1.5x charge pump emphasizing the analysis of its working principle and then designed the sub-circuits. In the parts of sub-circuits, the author analyzed and designed the following typical sub-circuits: REFERENCE, ERROR AMPLIFIER, OTP.Based on the finished analysis of circuit principle and circuit design, the author simulated the functioning features and key parameters by the use of the simulating...