A novel current estimation technique for digital controlled switching converters operating in CCM and DCM

Inductor current in the high speed switching converters is used as a feedback signal for current mode control and over current fault protection. Sensing inductor current for the use of digital controllers require high bandwidth current sensors and also need high speed Analog to Digital Converter (ADC) to convert the sensed current into digital domain. Use of high bandwidth current sensors and high speed ADCs make the sensing costly and complimented. Hence, eliminating current sensor and ADCs is in the interest of the present day research. These can be eliminated by estimating inductor current instead of sensing it. The estimation process uses converter voltages easily sensed using slow ADCs. This paper proposes a novel high bandwidth digital inductor current estimation technique which using low cost comparators. This technique estimates both DC and switching frequency components of the inductor current. The estimation is accurate to 9 % of the actual current irrespective of the converter operating in Continuous or Discontinuous Conduction Mode (CCM/DCM). The theory and its practical implementation procedures are given in detail. The proposed theory is validated with the experimental results on a 98 kHz, 3.3 V / 10 A buck converter working in CCM and DCM.