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Measuring Current and Current Sharing of DC-DC Converters

Istvan Novak (Senior Principle Engineer, Oracle)

Peter Pupalaikis (Vice President of Technology Development, Teledyne LeCroy)

Lawrence Jacobs (Manager, Probe Development Group, Teledyne-LeCroy)

Location: Ballroom A

Date: Thursday, February 1

Time: 2:50pm - 3:30pm

Pass Type: 2-Day Pass, All Access Pass, Alumni All Access Pass - Get your pass now!

Track: 13. Applying Test and Measurement Methodology

Audience Level: Introductory

Format: 40-Minute Technical Session

Vault Recording: TBD

Audience Level: Introductory

A favorite way to current measurement in DC-DC converters is by using an RC network across the main inductor. We establish a practical range for the time constants needed and will illustrate the effectiveness of DSP-based corrections for time-constant values. It will be shown and illustrated that even though the voltage across the capacitor of the RC element rides on the 'quiet' output voltage, for multiple reasons the common-mode voltage range and common-mode rejection of the measurement circuit is still very important. The noise floor, dynamic range, confidence level and speed of the impedance measurement solution will also be analyzed.

Takeaway

• RC time constant not matching the L/R time constant of switching inductor in current-measurement applications can be compensated for in signal processing
• Current-ratio transfer functions can be early indicators of potential current sharing issues
• Good common-mode rejection of probes and measuring instruments are essential

Intended Audience

None