In this paper, an adaptive synchronous rectifier (SR) driving scheme for the LLC resonant converters using the ripple counter concept is proposed, along with two methods of implementation. With the proposed scheme, the SR drain to source voltage is sensed to detect the body diode conduction, based on which the SR on-time can be well tuned to eliminate the body diode conduction. One proposed implementation tunes the SR on-time every switching cycle based on the ripple detection; another proposed implementation tunes the SR on-time every nth switching cycle (n = 1, 2, 3...) based on the ripple counter, which is suitable for the high frequency LLC converters. The proposed SR driving scheme has the simple implementation, requires only low-cost digital controllers and occupies very few controller resources. More importantly, since the digital controllers have already been widely adopted in the control of the LLC converters, the proposed adaptive SR driving method can be embedded into these digital controllers with little extra cost. Furthermore, how to integrate the proposed SR driving method with closed-loop control is explained in details. Experimental results are demonstrated on a 130kHz LLC converter with 100MHz microcontroller (MCU) and a 500kHz LLC converter with a 60MHz MCU and a ripple counter.