Research on High Precision Inductor Current Sensing Method for Current-mode Switching Power Supplies

Aiming at buck-Boost DC-DC power supply with high precision peak current mode control, a high precision circuit using power tube conduction resistance RDS to sense inductance current information is proposed, which solves the problem that the sensing gain drift of RDS in traditional structure is unstable due to the influence of PVT. Based on 0.18μm high voltage BCD process, the circuit design and physical implementation of the proposed method are verified. The test results show that: when the input voltage is 2.9V~4.5V and the temperature is -40°C~85°C, the current accuracy is up to 99.7%, and the maximum error difference is only 2.5%. The design value of current limiting protection is 2.15A, and the test results show that the current limiting protection circuit can turn off the main switch tube when the inductance current is 2.14A, and the error is only 0.005%. This structure has been successfully applied in a buck-Boost power supply.