Semiconductor laser, which serves as a primary pump source for fiber laser, requires a reliable and stable constant current driving source. The current stability and system reliability of the laser power supply have a large influence on the stability of output laser and the service life of the high power fiber laser. The LLC converter has the advantages of high efficiency and power density. It achieves output regulation by adjusting the resonant tank’s gain through frequency modulation, which ensures relatively high precision in voltage control but suffers from lower accuracy in controlling output current. This paper proposes a comprehensive suppression scheme for output current ripple in high-power constant-current drive power supplies used in vehicle-mounted laser systems, along with robust protective functions. Experimental results show that, when the power supply outputs a current of 20 A, the current ripple does not exceed 150 mA, and the ripple rate is below 0.85%.