Tian, Bo (2015-05). A Single-phase Rectifier With Ripple-power Decoupling and Application to LED Lighting. Master's Thesis.
In recent years, Light-Emitting-Diode (LED) is widely used in lighting applications for its high efficacy and high reliability. However, the rectifier, which is required by the LEDs to convert the AC power from the grid into DC power, suffers from low-reliability caused by the filtering capacitor. In order to fully utilize the long operational hours of the LEDs, this thesis proposes a rectifier that has improved reliability by adding a ripple-port to eliminate the non-reliable electrolytic capacitor. The ripple-port is capable of decoupling the ripple-power inherited in a single-phase rectifier, which enables using the reliable film capacitor to replace the electrolytic capacitor. To guarantee that the ripple-port can effectively decouple the ripple-power, a closed-loop control scheme is designed and implemented in a digital controller. Simulation and experimental results show that the proposed rectifier can reduce the required capacitance by 70%, which results in a 60% increase in lifetime. The proposed ripple-port circuit can be considered as an add-on module to be integrated into the rectifiers used in applications that require long lifetime. A detailed analysis of the efficiency, cost and reliability of applying the ripple-port in LED lighting applications supports the feasibility of the proposed circuit.