Class-E Resonant Converter

This chapter deals with class-E resonant converters, zero-voltage switching (ZVS), and zero-current switching (ZCS). ZVS is implemented by placing a capacitor across the power switch. This approach is based on the recognition that the capacitor's voltages are continuous. ZCS is implemented by connecting an inductor in series with the power switch. Both techniques can be enhanced by taking the advantage of resonant circuits. The power stage of a class-E resonant converter can be transformed into an equivalent circuit, which delivers the same average load power as the original circuit. The resonant DC-DC converter studied in this chapter is designed to have a constant switch-off time. However, for output regulation, the switch-on time is modulated. This control strategy implies a frequency-modulated power stage and a control loop, where, after being scaled and processed by a constant feedback ratio and the error amplifier, the output generates an error voltage. The error voltage feeds a voltage-controlled oscillator (VCO), which produces a variable switching frequency driving the driver and the power stage.