Undertaken a final year electronics engineering main project on UPS (Uninterrupted Power Supply), UPS has been designed to provide emergency power supply to the load when input power supply fails. It consists of a battery, a transformer, an inverter and a rectifier circuit. The complexity of using separate inverter and rectifier circuits is reduced by using HEXFET which is a combination of both MOSFET and zener diode which will work as both inverter and rectifier. Apart from using HEXFET many other components like poly propylene capacitors and electromagnetic relays which are used for battery charging and protection of circuit. This project mainly deals to design a UPS which is better in terms of working efficiency.