A DC-DC converter with a high step-up voltage gain is used for many applications, such as high-intensity discharge lamp ballasts for automobile head lamps, fuel cell energy conversion systems, solar-cell energy conversion systems and battery backup systems for uninterruptible power supplies. Theoretically, a dc-dc boost converter can achieve a high step-up voltage gain with an extremely high duty ratio. However, in practice, the step-up voltage gain is limited due to the effect of power switches, rectifier diodes and the equivalent series resistance (ESR) of inductors and capacitors.