Design of a Current Sensing Circuit without Power Loss for DC-DC Converter

In order to decrease the additional power loss in DC-DC converter caused by current detection, a current sensing technique without power loss is proposed. Power MOSFET is being widely used in low and medium power DC-DC converters; it can be regarded as a resistor in the condition of turn-on. Thus, based on the analysis of traditional kinds of current detection technology, a novel current sensing technology is proposed, which senses the current by using the conduction voltage drop of the power devices in DC-DC converter, the accuracy of sensing current can be improved by adjusting the resistor connected in both ends of the transconductance amplifier, no additional current sensing circuit is needed, and the additional power loss can be avoided. The DC-DC converter operating at the frequency of 1MHz is simulated, and the simulation results verify the accuracy and feasibility of the designed circuit.