Multi-lamp current-balancing technique for cold cathode fluorescent lamp based on PWM control and fourier analysis

This paper proposes a current-balancing technique to equalize the driving currents for multiple cold-cathode fluorescent lamps (CCFLs) by modulating the fundamental components and harmonics in each lamp currents. First, we adopt a class D resonant inverter as the main circuit. Next, we introduce an averaging circuit incorporating the PWM control to form a new current-sharing controller, where the averaging lamp current and each sampling lamp currents are used to determine each corresponding duty cycle, to accurately equalize all CCFLspsila driving currents. This will balance each lamppsilas brightness and, consequently, improve the display quality of the liquid crystal display (LCD). Complete design considerations and mathematical model derived from Fourier series and Parsevalpsilas theorem are detailed. Finally, some experimental results are used to verify the correctness of the proposed control strategy.