Measurement of Step-Down DC/DC Converters with Bode 100

Focus:

This application note explains how the Bode 100 Vector Network Analyzer may be used to analyze control loop stability in stepdown dc-dc converters. It defines key concepts related to stability such as gain and phase margin and explains how to measure them using the network analyzer including how to inject a test signal into the converter's control loop using a low-value resistor and an injection transformer. To illustrate the techniques, measurements are performed on a dc-dc converter demo board from Linear Technology. Gain and phase measurements are repeated under different line (input voltage) and load conditions as a means of visualizing the effects of changing operating conditions on the control loop. The app note also describes how to use the Bode 100's shaped-level function. This function allows the user to adjust the amplitude of the injected test signal over a selected segment of the swept frequency range in order to account for nonlinearities in the converter under test.

What you’ll learn:

• How to analyze the stability and the control loop behavior of a a dc-dc converter using a vector network analyzer
• How to measure the gain and phase margin of a dc-dc converter using a vector network analyzer
• How to inject a test signal into the control loop of a dc-dc converter

Notes:

Omicron Lab's Bode 100 Application Note

View the Source

Author & Publication:

Stephan Synkule & Lukas Heinzle, Omicron Lab, Vendor website, Jan 01 2009

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