Analyse de boucle de régulation

Modulation au sein d'un convertisseur de puissance

La modulation de la largeur d'impulsion (PWM), la modulation de la durée d'impulsion (PDM) ou la modulation de fréquence sont au cœur de la plupart des alimentations à découpage ou des moteurs industriels. L'analyse et l'optimisation de la fonction de modulation sous-jacente sont importantes, afin d'évaluer la fonction de la boucle de régulation. Les oscilloscopes Rohde & Schwarz proposent des fonctions d'analyse dédiées idéales pour cette tâche.

Your power supply control loop test challenge

Getting the happy medium stimulus signal level. If the injection level is too low, the gain will be too high, causing noisy results at low frequencies. On the other hand, some control loops are very sensitive to the injected level; a too-high level results in a too-low gain, causing nonlinearities or large signal effects.

In addition, the necessary stimulus signal level may change with frequency. Typically, a higher signal level is needed at low frequencies, and a lower signal level is needed at higher frequencies.

For control loop signals with a voltage measured in millivolts and a frequency in the kilohertz range, probes must have a suitable low noise floor to support high sensitivity and low signal-to-noise ratios.

Impedance in the loop forward direction must be much larger than in the backward direction in order not to change the behavior of the circuit

Our control loop analysis test solution

4 families of Rohde & Schwarz oscilloscopes all offer features, functions and performance that make them ideal for frequency response analysis for power electronics: the R&S®MXO4, the R&S®RTB2000, R&S®RTM3000, and R&S®RTA4000.

R&S®MXO4 includes market-leading 4.5 million acquisitions per second, resolution provided by the 12-bit analog-digital converter, and 0.00001 vertical division trigger sensitivity, based on the unique R&S digital trigger, now available in the mid class.

All three RTx oscilloscope families feature a 10.1" capacitive touchscreen with 1280 × 800 resolution, a 10-bit AD converter, 10 s boot time, 16 digital channels (optional) and a wide range of optional instruments such as logic, spectrum and protocol analyzers, arbitrary waveform and pattern generators, and a digital voltmeter.

The R&S®RTx-K36 option for any of these oscilloscopes provides Bode plot analysis; the oscilloscope’s internal signal generator provides the stimulus signal (10 Hz to 25 MHz). Low attenuation probes are available for all these oscilloscopes.

Benefits of our analysis test solution

No need for an external signal source; the wave form generator built into the oscilloscope provides the stimulus signal (10 Hz to 25 MHz).

Running the analysis to investigate the stability is simple and straightforward, with a Bode plot function. The oscilloscope performs all the necessary parameter changes (with option K36). Simply turn the oscilloscope rotary knob to adjust the stimulus signal frequency, and observe directly on the oscilloscope screen how this affects the gain margin and phase margin.

A rigorous measurement procedure, especially since the optimum stimulus signal level may change with frequency. Use amplitude profiling to optimally match the signal level to the given frequency. Up to 16 steps in the signal level are supported.

Ideal probes for all supported oscilloscopes

Do you have further questions regarding our control loop analysis solutions? Please contact us.