A High-Bandwidth Current Estimator With Self Tunning for Digital Buck Controller

In order to solve the low-cost problem of high-speed current sampling in digital buck controllers, a current estimation method based on the direct current resistance current detection principle is proposed in this article. The inductor current including direct current (DC) and alternating current (AC) is obtained by performing high-frequency digital filtering on the voltage across the inductor (
V_L
). Quantitative analysis of various factors affecting the accuracy of current estimation is carried out. For improving the estimated current accuracy, the multi-phase interleaved clock sampling technique and the algorithm of the average duty cycle in the filter cycle are proposed to improve the
V_L
accuracy in each filter cycle. Meanwhile, considering the completeness of the current estimation algorithm, a calibration mechanism with a known current sink to adjust filter parameters online is adopted for the change of the inductance (
L
) and its equivalent impedance (
R_L
) due to process and aging. The proposed algorithm is verified in a buck prototyping board. Experimental results are presented to show that the proposed method is effective in both fixed frequency and variable frequency control modes. The DC and ac accuracy of estimated current reach 5% and 2%, respectively. The estimated inductor current delay is within 100 ns.