Current sharing between multiphase and/or paralleled power stages for power conversion such as for voltage regulators (VR) has previously been implemented in ways that include sensing and power loss. Multiphase voltage converters generally require a current sharing loop to maintain equal or desired current sharing between phases or paralleled modules. Prior current sharing schemes are based on sensing each phase current to provide the current information to the current control loop.
Multiphase voltage converters today require a current sharing loop, in addition to the output voltage regulation feedback control, to achieve appropriate current sharing among all phases and to provide controllability and stability. Without the current sharing loop, the multiphase converters tend to be unstable and go to a “Runaway” condition where a few or only one phase carries all the load current while other phases either carry very small or negative current, which leads to very low conversion efficiency, unstable output voltage with degraded transient response, and in the worst scenario the malfunction (destruction) of a converter.
The current sharing in previous designs requires sensing of each phase current, which usually requires about five passive components (some of which incur power losses) for sensing circuitry and a conditioning amplifier. This implies, for example, about twenty passive components and four amplifiers for a four phase converter. Moreover, the performance of the current sharing loop largely depends on the sensing accuracy of each phase and typically requires complicated calibration procedures and additional development cost.
Previously implemented sharing schemes have disadvantages including the fact that they operate to generate a pre-set sharing ratio that is independent of a converter efficiency value, they are highly affected by the sensing accuracy of each phase, and/or they require large associated sensing circuitries and off-line calibration. Therefore, new efficiency based current sharing would be helpful to eliminate or reduce many disadvantages of conventional current sharing schemes.