LED backlight driver circuit with dual-mode dimming control and current-balancing design

A dimmable LED driver circuit with dual-mode dimming control and current-balancing design for backlight application was examined and implemented in this study. Parallel current balancing can be achieved by a passive differential-mode (DM) transformer. The driver has the main power stage constructed by one boost converter. Owing to the high switching frequency, continuous current mode operation and DM transformer magnetizing inductance, the output side only needs an ultra low capacitor. Through the constant current and constant voltage dimming scheme, the LED has smoothed temporary voltage transient and will extend the lifetime of a LED lamp. Furthermore, simplicity, low cost, less capacitor, and gradual voltage rising slope can be achieved. This study included the analyses and discussions for the operational principles of the proposed LED driver. A 10 W-laboratory prototype was built and tested to verify the feasibility of the studied driver.