We can both enjoy the lighting and energy-saving by use of LED lamps. The LED is a small size solid lighting source. It is anti-vibrating, impact resisting and recyclable. Because the semiconductor manufacturing technology is improved, the cost is reduced 50% in recent 3 years. The efficiency and cost are both reinforced rapidly. In this thesis, the flyback converter and digital controller are both studied. The voltages and currents of the flyback converter are well controlled. The drive condition of the flyback converter is set at discontinuous mode (DCM). The rated power of the LED lamp is 18W. From experimental results, the input-output relations of voltages and currents are well designed and the conditions are satisfied.