An LLC Resonant Converter With Symmetric Pulse-Width Balancing and Fixed-Period Hysteresis Burst Control for High Efficiency Over Full Load Range

This paper presents a high-efficiency LLC resonant converter with an integrated controller. To speed up the transient response, Hybrid Hysteresis Charge (HHC) control is applied. However, identical ramp currents for control compensation pose challenges in precise current matching, leading to output current discrepancies and reduced device lifespan. Furthermore, LLC converter efficiency declines under light load conditions due to increased switching losses. To address the above problems, the proposed controller operates in three modes: high power mode, low power mode, and ultra-low power mode. HHC control combined with an innovative Symmetric Pulse-width Balancing (SPB) technique for accurate ramp compensation currents matching is used in high power mode. Fixed-Period Hysteresis Burst Control (FPHC) is applied in low power mode while minimizing audible noise. An Ultra-Low Power Mode (ULPM) is incorporated to maintain performance under ultra-light load conditions. Experimental results from a prototype converter with an input voltage range from 365 VDC to 410 VDC, an output voltage of 24 V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</sub>, and an output power range from 2.4 W to 240 W demonstrate a peak efficiency of 95.37% at an output current of 5 A and an input voltage of 410 V. At an ultra-light load of @#@.1A with an input voltage of 365 V, the circuit remains 89.05% efficiency.