This paper presents a resonant converter with the benefits of wide output voltage, wide soft switching characteristics for power devices and high circuit efficiency. Since the series resonant circuit is adopted on the primary side, the power switches are turned on under zero voltage switching and power diodes on the secondary side can be turned off under zero current switching. To overcome the drawback of narrow voltage operation range in the conventional resonant converter, full-bridge rectifier and voltage-doubler rectifier topologies are employed on the secondary side for low-voltage output and high-voltage output applications. Therefore, the voltage rating of power devices on the secondary side is clamped at output voltage, rather than two times output voltage, in the center-tapped rectifier circuit. Synchronous power switches are used on the secondary side to further reduce the conduction losses so that the circuit efficiency can be further improved. To verify the theoretical analysis and circuit performance, a laboratory prototype with 1 kW rated power was built and tested.2 of 16 needed for EV and HEV applications or outdoor LED lighting systems with variable series or parallel combinations of LED strings. There are several solutions to overcome the challenges of wide input or output voltage range operation. First, the conventional full-bridge converter, as shown in Figure 1a, with wide duty cycle control can be adopted to achieve wide voltage operation. If the maximum duty cycle is four times the minimum duty cycle (d max = 4 d min ), then the output voltage of full-bridge converter is controlled at the constant value for 4:1 input voltage range (v max = 4 v min ). However, wide duty cycle operation will result in low circuit efficiency in cases of high input voltage and low duty cycle. The second solution to achieve wide voltage operation is using two-stage dc-dc converters, as shown in Figure 1b, such as buck or boost circuit and full-bridge circuit. Since two-stage circuits are used, the circuit efficiency is decreased and the circuit reliability is also reduced. The third solution is using single stage hybrid resonant circuit topology [12][13][14] as shown in Figure 1c. The wide voltage range resonant converter with full-bridge circuit (S 1~S4 are operation) or half-bridge (S 1 , S 2 and S 3 are operation) circuit topology used on the primary side [13,14] has been proposed to extend the input voltage range. The main advantage of the full-bridge and half-bridge resonant converter on the primary side is the wide input voltage range (v in,max = 4 v in,min ). However, there is a transient duration between the half-bridge resonant converter and the full-bridge resonant converter operation, and one power switch S 3 is always in the on-state under half-bridge resonant circuit, which will result in one more conduction loss on a powered device. The secondary side of the circuit topologies in Figure 1 is the center-tapped rectified circuit with two diodes to obtain low voltage output. If a wide output voltage i...