A flexible mode electrolytic capacitor-free LED driver with high efficiency over a wide range of input voltage

The conventional ac-dc LED drivers fail to achieve high efficiency and optimized bus voltage over a wide range of input voltage. In order to obtain the better performance in high-line and low-line conditions simultaneously, a flexible mode LED driver is proposed. The proposed driver can operate in half-voltage input mode at high-line input to achieve relatively low-bus voltage and high efficiency. Meanwhile, the proposed driver can operate in full-voltage input mode at low-line input to cut down the diode loss and switch loss; thus, high efficiency can be also achieved. Meanwhile, zero-voltage switching characteristic of the active switches can be fulfilled in both modes. In addition, the proposed LED driver can achieve electrolytic capacitor free. The detail structure, operational principle, and design considerations are examined in detail. Finally, the feasibility and the effectiveness of the proposed LED driver are verified by an experimental prototype with rated power of 100 W.