Design Considerations For DCR Current Sensing In Boost Converters

Focus:

In dc-dc converter applications, using a current-sense resistor to detect overloads generates additional conduction loss, requires a large footprint for heat dissipation, and adds cost. Inductor direct-current resistance (DCR) current sensing can eliminate the current-sense resistor, reducing solution size while improving efficiency. This article explains how to design an inductor DCR current-sensing circuit and discusses practical design considerations to improve current-sensing accuracy in boost converter designs. Article begins by explaining the principles of inductor DCR sensing, then discusses factors affecting current-sense accuracy such as time constant mismatching and bias-current-induced offset voltage. Techniques for minimizing the offset voltage error are described. Loss mechanisms in resistor and DCR current sensing are explained and compared. Experimental results compare the converter efficiency obtained with inductor DCR current sensing versus resistor current sensing.

What you’ll learn:

• How to optimize current sense accuracy in boost converters when using inductor DCR current sensing
• How to understand the impact of inductor DCR current sensing versus resistor current sensing on boost converter efficiency

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Author & Publication:

Haifeng Fan, Texas Instruments, Phoenix, Ariz, How2Power Today, Mar 15 2014

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