Page 47 - PEN Ebook May 2021

Test & Measurements Test & Measurements

There are better or worse solutions depending the performance increase of computers cannot be CONCLUSION

on the type of application. The second option is neglected but, finally, every simulation is only as The renaissance of power elec-
to use the best semiconductor available. New good as the models and the supplied data are. Pas- tronics is a result of current
semiconductor materials have found their way to sive components are an example. Typically, speci- market trends. Efficient and
the market. The wide band gap materials (WBG) fications of passive components are changing with reliable power converters be-
like Silicon Carbide (SiC) or Gallium Nitrite (GaN) the use case. For example, ceramic capacitors have came the crucial part in many
are the most prominent ones. Both have low- different capacity at different bias voltages, or the designs. New semiconductor
er losses (switching/conducting), have a higher inductance of coils change with the current. The materials give their contribu-
voltage withstand and support faster switching datasheet of components most of the time does tion and open several new pos-
frequencies. But, as it constantly happens, noth- not represent this. ESR, ESL or AC resistance are sibilities for design engineers,

ing comes for free. Obviously, new and modern not given for the frequency of the real use case. It but also bring new challenges
semiconductors might stand in conflict with the is therefore necessary to measure the components with them. To get insights and
requirement on lower cost. But on a second view under real conditions before it make sense to feed be able to get the best out of
there is no real conflict there. SiC/GaN devices them into the simulation tool. Furthermore, there the design it is still necessary
are indeed more expensive compared to well-es- are Must-Have tests like EMC Compliance and re- to do extensive measurements.
tablished Silicon-based MOSFETs, but the poten- liability testing. Also, performance specifications of Siglent has extended its meas-
tial for cost saving lies in the fact that they allow the final product like power consumption, dynamic urement equipment during the

using less and/or smaller components or heat response need to be proved by measuring. last years and can now offer a
sinks. Another challenge is the lack of experience wide set of products to help
with using SiC and GaN and this might lead to So finally, let us have a look at the most com- engineers solve their tasks.
issues (e.g. instability) during the design cycle. mon and important measurements. For didactic
Figure 2: Step Response.
Also, higher switching frequency is a brilliant reasons, we might start with the measurement of
source for EMC emissions, and this is crucial as, the dynamic response, which is typically done at To achieve an optimized design and finish
in the end, there is a standard to which the prod- a later stage in the development process, but it everything within the given time it is suggested
uct must comply. clearly shows what happens if the design is not to start measuring as early as possible. Ideal-
properly done. During the measurement of the ly, the first task should be to optimize the inner

Meeting the requirements of a smaller size and Load Step Response the load current steps be- “core” i.e., the switching stage. A proper layout
weight is mandatory if the product is designed tween e.g. 10% and 90% of the maximum current. is crucial here to avoid high frequency ringing
for the wearables market, lower weight is also Parallel to the current, the output voltage will be caused by LC resonances (CDS / Ltrace). Fur-
an important specification for electrification measured. Top section of figure 2 shows inten- thermore, the dead-time between high-side and
of transportation no matter if it is for drones sive ringing. This can be an issue when it comes low-side switching has to be proper. If too tight,
or cars. The new WBG-switches can also offer to EMC testing. As shown, oscillations point to an short circuits can happen and if it is too long,
a solution here, but as mentioned above, this insufficient stability of the design and issues at efficiency goes down.

brings EMC with them. Ensuring reliability and the feedback loop. To get more insights, the next
stability, EMC compliance, meeting costs and step should be measuring the loop response and
space as well as the ability to connect the T&M determining phase and gain margin with the help For More Information
equipment are the most relevant challenges. of a Bode Plot. All Siglent X-Series oscilloscopes
include this functionality and make testing easy
Another interesting question is: Do we still need to and affordable. After the design has been opti- ▶ Testing! Not Guessing! Talk at Power Forum 2020
measure or can simulation make testing obsolete? mized and the phase margin has been increased
Truly, the recent developments and improvements the result of the load step response looks just as ▶ GaN and SiC
on simulation software and models combined with in the bottom section of the picture (figure 2).

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