Abstract: A method of passive current balancing for digital control of multiphase DC-DC converters is provided based upon the duty-cycle matching principle. Current balance is achieved by inserting a digital filter into the control path. Being sensorless, it is insensitive to current measurement inaccuracies caused by noise, component value tolerance or variation. It will be shown that effective current balancing can be achieved via some simple modifications to standard voltage mode control laws, allowing current balancing to be achieved with minor additional complexity. The current share scheme has been shown to perform well dynamically, matching currents cycle by cycle during load steps, and clearly benefiting from the absence of the slow current share loop popular in traditional methods. The current share filter proposed, blends well with existing digital controllers. Given the very low complexity in implementing the filter, the degree of matching achieved is exceptional.