Comparison of three different topologies of driving LEDs with a piezoelectric transformer

The main purpose of this paper is to compare three different topologies of LED drivers by using a piezoelectric transformer. The advantages of LEDs lighting applications include small size, low power consumption and high efficacy. On the other hand, the merits of the piezoelectric transformer are thin profile, high power density and no electromagnetic interference radiation unlike conventional electromagnetic transformers. Therefore, piezoelectric transformers are suitable to drive LEDs. Since the output voltage of a piezoelectric transformer is highly related to the load impedance, the type of the connection between the piezoelectric transformer and LEDs is a key design parameters as it influences temperature rise and efficiency. In this paper, three different types of connections in driving LEDs are discussed in detail. They are LED self-rectifier, full-wave rectifier and current doubler. Theoretical analysis of these three various topologies are discussed. The theoretical predictions were verified by the circuit simulator PSIM. The characteristics of the three driving methods are compared and summarized.