Reduction of DC/DC Converters EMI Emission Using Bi- and Unidirectional QR-ZVS Topologies

Switched-mode power supplies (SMPSs) operating at high switching frequency (HSF) in the MHz range offer advantages such as improved output voltage regulation, reduced filter size and lower system cost. However, these benefits come with challenges. HSFs can lead to increased total losses, reduced efficiency and severe electromagnetic interference (EMI) emissions, due to transient current and voltage (dv/dt, di/dt). Although wide bandgap (WBG) devices - such as Gallium Nitride (GaN) and Silicon Carbide (SiC) transistors– can afford HSFs, but on the cost of greater switching losses and EMI noise, especially when opting for hard-switching pulse width modulation (PWM) converters. To address the EMI emissions, various methods have been explored, which include the use of EMI filters, the adoption of different spread-spectrum modulation methods, selecting appropriate components along with improved circuit design, and soft-switching techniques. This paper presents the use of the quasi-resonant (QR) zero voltage switching (ZVS) technique for the purpose of reducing the converter EMI noise and enhancing its efficiency, while opting for HSF up to 4 MHz with GaN-HEMT, using fixed LC resonant tank parameter.