Pulse-Amplitude-Modulation Full-Bridge Diode-Clamped Three-Level LLC Resonant Converter With Offset Voltage Injection Method

In this paper, a full-bridge diode-clamped three-level LLC resonant converter with pulse-amplitude-modulation (PAM) suitable for a high-input voltage system has been studied. Unlike the existing frequency sweep converter, the proposed PAM method controls the output voltage by modulating the magnitude of fundamental component of leg voltage input to the resonance tank while fixing the operating frequency at the resonance point. In addition, the PWM switching pattern was easily implemented by applying an offset voltage while reducing the switching loss by using the ±180° discontinuous PWM (DPWM) technique. In this study, the control algorithm and operation characteristics were analyzed in detail, and the feasibility was confirmed through simulation.