Novel Current Sharing Schemes for Multiphase Converters with Digital Controller Implementation

Abstract

Multiphase converters require a current sharing loop to maintain equal or desired current sharing between phases or paralleled modules. Conventional current sharing schemes are based on sensing each phase current to provide the current information to the control loop. Such schemes have disadvantages including the fact that they operate to generate a pre-set sharing ratio that is independent of converter efficiency value, they are highly affected by the sensing accuracy of each phase, and they require large associated sensing circuitries and off-line calibration. In this paper, new efficiency based current sharing concepts and schemes are proposed and discussed to eliminate or reduce the disadvantages of conventional schemes. The proposed concepts are based on dynamically maximizing the efficiency (minimizing power losses) of the converter to achieve the optimum current sharing ratio. They also provide schemes that are independent of sensing accuracy and require a reduced number of sensors and associated circuitries. The proposed schemes can be used for current sharing as stand-alone designs or can be combined with conventional schemes to achieve online current sharing loop calibration. Digital controller implementation is presented utilizing flexibility and other advantages of digital controllers. Experimental results are presented to support the theoretical analysis.