Control loop analysis

Control loop analysis

Modulation analysis

Pulse width modulation (PWM), pulse duration modulation (PDM) or frequency modulation are at the heart of almost any switched mode power supply or industrial drive. Analyzing and optimizing the underlying modulation function is important for assessing the function of the control loop. Rohde & Schwarz oscilloscopes feature dedicated analysis functions that are ideal for this task.

Analyze pulse width modulated signals
Analyze pulse width modulated signals

Analysing pulse width modulated signals

The track function of the R&S®RTM3000 and the R&S®RTA4000 oscilloscopes can demodulate the PWM signal and extract the underlying modulation signal in a track waveform. This analysis tool plots the results of any given value against time, giving you a very clear view of how PWM parameters change when measured for a relatively long period.

Startup behavior of LLC converter
Startup behavior of LLC converter

Startup behavior analysis

Resonant converters often use a start frequency that is much higher than the resonant frequency. This limits the resonant current, but it also lengthens the actual startup phase. This application card shows how to analyze the startup phase of a resonant converter using the PWM frequency track function.

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Control loop stability

Application card: Power supply control loop response measurements (Bode plot)

Bode plots are an important tool for verifying control loop stability of switched mode power supplies. Today, this functionality is also provided by oscilloscopes. This application information shows how.

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Application note: Tips and tricks on how to verify control loop stability

Download this application note to learn how to perform good control loop stability measurements using oscilloscopes.

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Webinar: Tips and tricks on how to verify control loop stability

Register and watch the webinar from March 2020: Tips and tricks on how to verity control loop stability with Andreas Ibl & Marcus Sonst, Rohde & Schwarz experts in this topic.

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eGuide: Practical tips for accurate Bode plot measurements

This online guide includes a wealth of practical tips for choosing suitable equipment, setting up measurements, running tests, and interpreting the measurement results.

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Related topics

DC/DC converter evaluation

This application note evaluates the main dynamic behaviors of a DC/DC buck converter. The test procedures and measurements described determine whether the converter operates in a safe manner and whether it meets its design goals for startup time, inrush current, peak inductor current, inductor behavior, output ripple and ripple spectrum.

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Harmonic analysis with R&S®Scope Rider

An ideal electrical supply would deliver a constant frequency, sinusoidal voltage waveform with unvarying magnitude. Real power supplies deviate from this behavior due to varying system loads, transients and outages. Insufficient power quality can lead to failures of machinery, electric control systems or computers connected to the electrical supply network. Power quality measurements characterize the harmonic pollution, reactive power and load imbalance of power supplies.

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Related products


The R&S®RTO2000 and R&S®RTE1000 feature track functionality for analyzing the PWM modulation of switched mode power supplies.

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High voltage probes

Rohde & Schwarz offers passive and active differential high voltage probes that support various power electronics measurements, including PWM analysis.

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Power analysis option

The R&S®RTx-K31 software option provides essential measurement functions for analyzing power electronics, including inrush current, output spectrum and safe operating area. Its available on the R&S®RTM3000, R&S®RTA4000, R&S®RTE1000 and R&S®RTO2000 oscilloscopes.

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Related solutions

Efficiency testing

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EMI debugging of embedded power electronics designs

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Switching analysis

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