High-Resolution Inductor Current Estimation Algorithm for Digital Controlled Buck Converter

With the demand for the fast transient response of the voltage regulator module (VRM), current mode controls are used to achieve high bandwidth control, which brings the need for inductor current feedback. The inductor current sampling is one of the major issues in digital control, because of the complex current sensing circuit and sampling noise, as well as the increasing design complexity and cost in multiphase applications. In this paper, a high-resolution current estimation algorithm is proposed, which samples the input and output voltage and calculates the inductor current by digital filter. The current estimation algorithm makes it possible to avoid using the high-speed Analog to Digital Converter (ADC) to obtain the inductor current for close-loop control. Compared to existing current estimation research, this paper proposes a high-resolution approach, applies the delay line structure, and significantly improves the estimation accuracy at steady state under various load conditions and load step transient in low voltage and high current applications. The high-resolution scheme is implemented by Xilinx FPGA and verified on the multiphase Buck system. The experimental results show that the estimation is accurate within 3.8% and 1% under the light and heavy loads respectively. The proposed scheme is also compared with the up-to-date research to prove the advancement.