Reaches the regulated value, the output voltage should smoothly ramp up in a relatively slow manner with little or Startup examines specifically what happens when input voltage is first applied (or an enable pin is asserted). But, for the most part, this test is less important than load step. Some applications (such as audio) are particularly Stepped between two values while observing the output voltage. Steady-state analysis is actually just a convenience.Īnother way to disturb the control loop and observe its recovery is via line transient. Load-step tests by zooming in for a closer inspection of the waveforms between the load steps. Steady-state operation can actually be observed during Cycles that aren’t identicalĬould be a sign that the converter may be oscillating. Switching cycle (similar to a patient’s respiratory rate in our human health analogy). With a converter in equilibrium, every switching cycle looks just like every other One could argue that steady-state analysis is an oxymoron for switched-mode power conversion. Simulating thisĪnalysis is particularly valuable since the analysis may not be available in the lab. Signal is swept over a frequency range, the gain and phase response are plotted on a log scale. The signal at various points in this loop to establish the gain and phase shift between two signals. When available, a Bode analyzer injects a signal into the control loop and then measures AC analysis, also known as small signal, Bode, or frequency-response analysis, requires specializedĮquipment that’s not commonly found in the lab (examples include AP Instruments AP300, Omicron Bode 100, orĪgilent 4194A or 4195A). Looking at the control loop in the frequency domain, AC loop analysis enables direct measurement of the control-loopīandwidth and phase margin (going back to our human health example, this step is like taking a patient’s blood The control loop, AC loop analysis is used. For a more complete picture of the “health” of An engineer with a trained eye can qualitatively judge the effectiveness of theĬontrol loop by inspecting the load-step transient response graph. The converter can overshoot or undershoot too far, ring excessively, recover too slowly, or break If the feedback circuit is not properly designed, a variety of Output voltage changes and how quickly it recovers. Load-step simulation measures how much the Just as a person’s pulse changes with exercise, the output voltage of a powerĬonverter changes when it is exercised by a change in the load current. Like taking a patient’s pulse in our human health analogy, load step is arguably the most important vital sign toĪssess in a power converter design. Maxim’s EE-Sim ® design generation and simulation environment defines these tests to be: There’s a set of "vital sign" tests to establish the health and robustness of a power converter design that areĪnalogous to medical vital signs that provide an overview of a human’s overall health. How Healthy is Your Power Converter Design? In thisĪpplication note, we’ll compare the two and examine why the SIMPLIS engine is more effective for power designs. That said, there are two simulation engines that have emerged for power supply circuits: SIMPLIS and SPICE. What’s more, the simulation solutions optimized for ICs are not necessarily the best tools for power conversion ICs that go to production with “first silicon.” Power supplies and converters are notoriously hard to simulate. Maxim, for instance, measures simulation success by the number of its The semiconductor industry recognized decades ago that it could only be successful by completely simulating ICĭesigns before fabricating the first wafers. Power management engineers, however, have been late to integrate simulation into their processes. And worse, there would be times when not all problems were caught before the product was shipped to customers. Remember the days when it was common to design boards, test them in the lab, debug, redesign, and repeat again and again until the design was right? This approach would often delay product introduction. After all, redesigning and respinning PCBs is a costly endeavor. It provides an assessment of how the design will function, which can save time in the design process and, ultimately, costs. To boost the chances that a design will work properly while in production, most engineers turn to simulation. This application note compares two power simulation engines, SIMPLIS and SPICE, and shows why SIMPLIS is ultimately the more effective option for power circuits. In the end, simulation also saves time and money. Power circuits are difficult to simulate however, simulation is an essential way to help ensure that the design will work in production.
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