Phase-Shift Modulated Hybrid LLC and Half-Bridge Converter With Fixed Frequency for Wide Voltage Gain Range Application

In this article, a novel hybrid
LLC
and half-bridge (HB) converter is proposed for wide voltage gain applications. The proposed converter is composed of a conventional
LLC
resonant converter and a HB converter. The
LLC
resonant converter and the HB converter are connected in parallel on the primary side with an auxiliary winding of the
LLC
transformer inserted in the primary power loop of the HB converter, while the secondary windings of two converters transformers are inversely connected and share a voltage-doubler rectifier. The
LLC
and HB operate with the same fixed frequency, and the phase-shift modulation control between two converters is utilized to regulate the output voltage. Zero-voltage switching of all the primary switches and zero-current switching of all second side diodes can be achieved over a wide range of output voltage and load conditions. Detailed principle and voltage gain analysis based on time-domain method has been presented. After that, a simple approximate analysis method is proposed so that the voltage gain can be obtained more easily and main parameters of the converter can be fast optimally designed. Finally, a 1 KW laboratory prototype with 400 V input/50 V–450 V output has been built up to verify the theoretical analysis of the proposed converter. The peak efficiency achieves 97.9%, and features good voltage regulation capability. Thus, the proposed converter is suitable for wide voltage gain range applications.