A novel bidirectional current estimator for digital controlled DC-DC converters

摘要

In a bidirectional converter, the inductor current is needed to control the power flow between the source and the load. Sensing the inductor current for the use of a digital controller requires a wide bandwidth current sensor and a high speed Analog to Digital Converter (ADC). The high speed ADC is a costly device and complicates the physical implementation because it is prone to noise. Hence, estimation of the inductor current instead of sensing is a topic of research. This paper proposes a technique which can estimate the current through an inductor irrespective of the direction of current flow. The proposed technique eliminates the need for a high speed ADC and wide bandwidth current sensor. The proposed inductor current estimator is compatible to be used directly with a digital controller. This can estimate both the average DC and the switching frequency ripple components of the inductor current. Since, the switch node voltage of the converter gives the real time status of the converter. Switch node voltage of the converter is used for estimating the inductor current in the proposed technique. The switch node voltage is sensed using a low cost discrete comparator. Detailed theory and practical implementation procedure of the proposed technique are given. Experimental results to validate the proposed current estimation technique are given. The experimental results validate the proposed technique for both forward and reverse operation with the accuracy up to 10%.