Integrated lossless load current sensing method for buck–boost DC–DC converters

An integrated lossless load current sensing method for buck-boost DC-DC converters is presented. The load current is detected by sensing the average current flowing through the power transistor connected between the inductor and the output capacitor. The circuit is almost independent of voltage and temperature by using a sense resistor method. A second-order on-chip lowpass filter is adopted to average the sensed voltage. The buck-boost converter could automatically switch between heavy and light load modes with a fixed switching current for different input and output voltages.