This paper presents a new free-running-oscillation resonant DC-DC converter with the Class-E oscillator and the Class-E rectifier, along with its design procedure and design curves for any conditions. The proposed converter is a free-running-oscillation system and has no gate-drive circuit to drive the MOSFET. Therefore, the structure of the proposed converter is simpler than that of class E 2 dc-dc converter. The proposed converter is suitable for a constant voltage and constant power operation under the fixed designed condition. The proposed converter has the ability to achieve a high power-conversion efficiency and low noises under high-frequency operation because of Class-E switching at both the oscillator and the rectifier. We investigate operations of the proposed converter by circuit experiments and show the validity of the design curves. This paper denotes two experimental results. One achieves 79.3% power-conversion efficiency under 1.54-W output power at an operating frequency 2.00 MHz. The other does 80.5% under 1.60-W output power at an operating frequency 1.98 MHz