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.
Multiphase converters require a current-sharing loop to maintain equal or desired current sharing between phases or paralleled modules. The current-sharing loop is highly sensitive to current-sensing accuracy. In this letter, a method is presented to achieve auto-tuning of the current-sharing loop in multiphase converters while adaptively calibrating the current sensing based on power conversion efficiency. This is achieved without the need for a precise calibration reference or resistor and with no dependency on sensing accuracy. A digital controller implementation of the method is described and experimental results are obtained for a 0.84 V/30 A two-phase buck voltage regulator.
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