Design Of DCM-CPM-White LED Driver

White LED is now regarded as the next generation of light source because of its power saving, high efficiency, long life, low pollution and low radioactivity. White LED is become the best selection for small color LCD backlighting. With the maturating of White LED technology, it will be applied in many fields. Different from the traditional source, a special driver IC is needed for the White LED to maintain its normal working status.With an eye to the rapid market development, we design in this paper a DCM-CPM-White LED driver which is applied to White LED backlight driving with adjustable output current. It works at a fixed frequency, drive up to four White LED series and provide adjustable current to control brightness and color purity. This driver is featured by over-current protection, current detection and open-load protection features. This paper first completes DCM-CPM driver modeling, then designs and analyses each of the major modules of the circuit. For example, oscillator, band-gap reference source, the current detection amplifier, the error amplifier, PWM comparator, over-current comparator module and so on.Based on the analysis of circuit theory and the circuit topology, every module and the entire circuit are simulated by the Cadence Spectre tool. The simulation result not only meets with the target specification, but also verifies the design, which demonstrates the excellent performance of White LED driver IC realized by current-mode DC-DC converter technology. In addition, the loop is a single polar system and the whole circuit is so stable that no compensation circuit is needed.