Current-sensing techniques for DC-DC converters

Current sensing is one of the most important functions on a smart power chip. Conventional current-sensing methods insert a resistor in the path of the current to be sensed. This method incurs significant power losses, especially when the current to be sensed is high. Lossless current-sensing methods address this issue by sensing the current without dissipating the power that passive resistors do. Six available lossless current sensing techniques are reviewed. A new scheme for increasing the accuracy of current sensing when the discrete elements are not known is introduced. The new scheme measures the inductor value during the DC-DC controller startup.