Troubleshooting Distributed Power Systems (Part 6): The Switch Node

Focus:

System and power converter issues are frequently related to a converter’s switching characteristics, which are most easily observed at the switching node. In this 10-minute video, Steve Sandler discusses the measurement and interpretation of switch-node waveforms as observed in point-of-load regulators or POLs. He discusses the instrumentation requirements for measuring switch-node waveforms, why switch-node waveforms should be viewed using different time scales, and the impact of scope probes on measurements. With those measurement requirements as background, Sandler examines how switching frequency and duty cycle affect power supply stability as well as EMI. Measurement examples demonstrate the influence of the switching frequency on the zero-order hold, which in turn impacts stability margin; the impact of stability on switching frequency jitter; and the impact of frequency jitter on EMI and output ripple and noise.

What you’ll learn:

• How to understand instrumentation requirements for measuring switch-node waveforms
• How to understand the impact of switching frequency and duty cycle on power supply stability and EMI

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Author & Publication:

Steve Sandler, AEi Systems and Picotest, Phoenix, Ariz., How2Power Today, Nov 15 2013

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