Reducing Circling Currents in a VHF Class Phi(2) Inverter Based on a Fully Analytical Loss Model

This paper proposes a fully analytical loss model to reduce circling currents and improve the power efficiency of a class Phi(2) inverter. Firstly, analytical expression of the switching node voltage is derived by analyzing its harmonic components. Based on the result, the power switch is modeled as a voltage source, where the circuit is simplified to a linear network and analytical expressions of branch currents are solved. Secondly, root mean square (RMS) values of branch currents and component losses are calculated to form the analytical loss model for a Phi(2) inverter. The influence of circuit parameters on the circling current and power efficiency are thoroughly analyzed, which derives optimal design constraints to reduce circling currents of a class Phi(2) inverter. Furthermore, detailed design guidance and equations are provided to calculate circuit parameters of a class Phi(2) inverter, which reduces its circling currents and improves overall power efficiency. Finally, a class Phi 2 inverter prototype is built, and experimental results demonstrate a 7% efficiency improvement compared to conventional empirical design methods.