Nowadays, the LLC converter has been widely used in power supply industry for high conversion efficiency and high-power density. LLC resonant converter can regulate the output voltage by changing the switching frequency. For example, when the output-load is decreased, LLC resonant converter will increase the operating frequency to maintain output voltage, but the high switching frequency will reduce the conversion efficiency. To use the burst mode control has been proposed for increased conversion efficiency at light-load conditions. Unfortunately, the switching period of power-switches is still operated in a high switching frequency during the burst-mode operations, moreover, the burst mode control will also cause a high low frequency output voltage ripple. This paper proposes a valley switching control (VSC) for LLC resonant converter at light-load conditions, compared with burst mode operations, this VSC is effective to reduce the switching loss and low frequency output voltage ripple. Detailed analysis and design of this valley switching control are described. Experimental results are recorded for a prototype converter with a DC input voltage 400-VDC, an output voltage 48-VDC, and an output current of 12.5-A.
|
專利行銷平台
