Analysis and design of a ground isolated switched capacitor DC-DC converter

Switched Capacitor (SC) DC-DC converters are transformer and inductor less DC-DC converters that are used to step up, step down or invert a supply voltage where the power requirements are usually less than 5W. The outputs of the currently available SC converters are referenced with respect to the input supply ground. Though SC converters are ideally suited for many low power miniaturized industrial applications due to their small size, lack of ground isolation in SC converters prevents their use in low power applications that require ground isolation due to ground noise sensitivity of the load. The work presented in this paper introduces the concept of ground isolation in a buck SC converter without the use of isolation transformers like conventional DC-DC converters. Switched capacitors driven by opto-isolated drives are employed to transfer power from the source to the load. The introduction of ground isolation in SC converters significantly widens its scope of application in industry. A state space averaged (SSA) model of the SC converter is developed to study its dynamic and steady state characteristics. The validity of the SSA model is verified with measurements on the hardware model.