A Delta-Sigma Modulated Power Converter with inherent Zero-Voltage Switching

In this paper an advanced modulation strategy is proposed that generates the switch control signals of a power converter while inherently guaranteeing zero-voltage switching (ZVS) operation. The proposed modulator is based on a first-order ΔΣ-modulator combined with a hold-off circuit. This hold-off circuit consists of a D-latch and maintains the converter's switching state until ZVS commutation can be achieved while an integrator ensures the correct average output. Furthermore, features are implemented to improve start-up and transient behavior. The operating principle and stability of the proposed modulator is discussed and simulation results are presented. Finally, the proposed modulator is validated on a 2kW GaN-based synchronous buck converter. Results show that the converter naturally operates under ZVS conditions by continuously varying its switching frequency without having to compute switching times or frequencies. The proposed method is an interesting alternative to pulse-width modulation especially when operating at high switching frequencies or when the switching loss in the power converter is significant.