Feedback design of a piezoelectric transformer-based half-bridge resonant CCFL inverter

The feedback loop design of a half-bridge resonant inverter based on a piezoelectric transformer (PT) for driving a cold cathode fluorescent lamp (CCFL) is presented in this paper. In order to stabilize the CCFL driving current and luminance, the PT-based resonant inverter incorporating a feedback compensator is designed to track the operating frequency. The dynamic equations and the small-signal model of the presented inverter system are established by using the harmonic approximation and harmonic balance procedures. The feedback compensation is performed by applying the derived small-signal block diagram. The complete mathematical analysis and design considerations are presented in detail. The experimental results agree with the theoretical predictions and confirm the validity of the proposed design approach.