A Multi-Lamp Current Sharing Controller Using Current-Mirror Technique for LCD Backlight Module

This paper proposes a backlight module which drives multiple cold-cathode fluorescent lamps (CCFLs) with a current mirror technique to equalize the driving currents for each lamp. A half-bridge parallel-resonant inverter is adopted as the main circuit and incorporated with a single-input, multiple-output transformer to drive the multi-CCFLs. Next, we utilize the current-mirror circuits to form a new current-sharing circuit. The current reference node and the parallel-connected multi-load nodes are used to equalize accurately all the CCFLs´ driving currents. This balances each lamp´s brightness and, consequently, improve the picture display quality of the related liquid crystal display (LCD). This paper details the concept of design for each component value with the assistance of an actual design example. The results of the example are examined with its actual measurements, which verify the accuracy of the proposed control strategy