Application of Piezoelectric-Transformer-Based Resonant Circuits for AC LED Lighting-Driven Systems With Frequency-Tracking Techniques

This paper proposes an application of piezoelectric transformer (PT) based inverters for alternating current (ac) light-emitting diode (LED) lighting-driven systems with a new resonant topology and frequency-tracking technique. This proposed architecture comprises a full-bridge phase-shift inverter with a PT-based C-L-C series resonant circuit, piezoelectric ceramic transformers, and a microwinding resonant transformer to extend the range of operation frequency, hence achieving a two-terminal alternating voltage to drive ac LED arrays while stabilizing the resonant characteristics. In this system design, a frequency-tracking mechanism is also integrated into the field-programmable gate array controller to improve operation efficiency. Since only the secondary current of the resonant transformer is required for the controller, the circuit implementation is simple and additional sensor devices can be largely saved. Moreover, by considering that the frequency-gain characteristics of PTs may be affected due to temperature changes; the controller is designed to adjust the operation frequency swiftly in order to restrict the temperature effect. This proposed method has been verified on modular ac LED lighting systems. Test results confirm the feasibility of the method for lighting system applications.