Abstract:

A dual buck-type DC/DC (Direst Cunent) parallel power supply system is designed to provide high-efficiency and stable DC bias for WLEDs (White Light Emitting Devices) used in VLC (Visible Light Communication) links. ARM7 processor (LPC2148) is used as the main controller, and based on the feedback voltage, the duty-cycle of a pair of PWM (Pulse Width Modulation) signals controlling the two DC/DC modules is adjusted for regulating the output voltage. By adopting two PMOS (P-channel Metal-OxideSemiconductor) switches, the currents of the two DC/DC modules are shared. To evaluate this power supply system, experiments are performed by using it to drive a WLED. The error between actual output voltage and expected voltage is less than 2%, the current error between the two DC/DC branches is less than 1%, and the power supply efficiency is within the range of 75%~80%. For the transient response, no overshoot or undershoot is observed during power on and power off processes. The rise time is about 20 s for the output voltage increases from 0 to 1.6 V, and the fall time is about 65 s when it drops from 1.6 V to 0. Besides, the life of this system is extended by using two DC/DC modules working alternately. This introduced proposal can be served as a solution for the multiple DC/DC modules power supply system to get high efficiency, stable output voltage and sharing current.

Key words: white light emitting devices （WLED）, power supply system, current-sharing parallel