This paper presents a robust control method for wireless energy transfer systems using current source resonant converter without any communication network. The proposed control strategy is valid even for systems with variable air-gap. Output voltage regulation, resonant frequency tracking and zero voltage switching condition are the main control objectives. The control strategy includes a simple modulation technique for the primary side class-D inverter and a sliding mode controller for the secondary-side full-bridge rectifier. Theoretical features of the presented control system are tested by some selected simulation results.