An integrated current sensing circuit with comparator function for a buck DC-DC converter in HV-CMOS

An integrated current sensing circuit with incorporated comparator function is presented. The current scaling is done in two independent steps, therefore very high current division ratio is obtained, which makes this circuit suitable for converters with large output currents. The additional comparator part eliminates the need for a separate comparator circuit, therefore reduces the design effort and complexity. The current sensing accuracy is in the range from 91.1% up to 99.6% for a wide range of output currents. Also, a high precision of the sensed current and a stable duty ratio of the converter for a wide range of temperatures and in process corner simulations are achieved. The complete buck converter is designed in 0.18 μm 50 V high-voltage (HV) CMOS technology.