A Study And Design Of The High Efficiency And High Voltage Driver Of The White Light LED

In recent years, the technology of high power white LED(Light Emitting Diode) has achieved enormous process. Due to the obvious advantages such as pollution-free, long operating lifetimes, lower power consumption and shorter response time, high-efficiency high-power white LED becomes the new trend in the lighting industry. Therefore, it is expectable to replace traditional incandescent light and fluorescent lamp by the high-efficiency white LED in the coming future.The luminous intensity of LED is in proportion to the forward current. The power LED, like the ordinary diode, has a steep forward voltage-current curve. One petty change in voltage can render a somewhat noticeable change in current, then follows the variety of luminance. Consequently, it is wiser to control current rather than voltage.Beside the current regulator, the lighting system needs an AC/DC translator. Nowadays, the lighting system which using the alternating power source need to include the AC/DC translator built by separation components. Then a low voltage power supplied power management IC is used to construct the current controlled LED driver. As a result, compared with incandescent light and fluorescent lamp this kind of system is more efficient. But the AC/DC circuits and current controlling circuits reduce the efficiency of the LED lighting system and no more advantage.The battery supplied system may need the DC/DC boost translator, the same efficiency problem also exist.With the rapid growth of technology in semiconductor manufacture, nowadays, many chip foundries have developed or are exploring the high voltage technology. Along with the maturation of high voltage BCD process (which can integrates bipolar, COMS and DMOS in one-single chip), a high voltage lateral double-diffused MOSFET (LDDMOS), whose drain-source voltage can bear a value of 500V, has arisen. And it enable the design and manufacture of high voltage Integrate Circuit.This paper proposed a design of high efficiency driver of white light LED with high input voltage, constant output current, using the high voltage BCD process. The LED driver with wide range input voltage and constant LED current is realized using the pulse width modulation controlling the peak current. Using the first order temperature compensation and resistive subdivision, a 0.25V band-gap voltage reference is constructed in the chip. As the high voltage process provides LDNMOS, the input voltage can vary from 85V to 450V. The enable controlling method of the chip improves the system's efficiency. The best efficiency of the system is 96.7%.