When designing semiconductor components in modern power electronics, designing a reliable power supply is often not a high priority. However, if the power supply fails, it can cause costly rework. Not only can operation of the power electronic come to an abrupt halt, but if the power supply isn’t designed or constructed to meet its predicted lifetime, it could also lead to the premature degradation of the entire power electronic system as well, as explained in this article.
While it’s crucial to ensure the reliability of the power supply in power electronics, doing so is often difficult for the following reasons:
The power supply is not often viewed as a product differentiator and is treated no differently than a resistor or capacitor. In fact, it is often seen as almost a necessary evil. This means that many companies don’t invest sufficient resources into a reliable power supply design from the start - only in mitigation if they begin to fail.
With the processor and memory taking up a majority of a power electronic system's space, the remaining room is often allocated to the power supply. Unfortunately, this can mean that the power supply is primarily designed to fit the available space, instead of being designed for reliable performance.
One of the most challenging aspects of the power supply design process is that requirements aren’t known until the analog/digital circuit power levels have been defined. However, the power supply must be designed and ready when the analog/digital boards come in and the power requirements are known. This often leads to a hasty power supply design process, with little to no room for reliability testing.
Multiple Packaging Technologies
If the printed circuit board (PCB) in the power electronics uses a blend of different packaging technologies, ensuring a reliable power supply can be difficult, as it will need to handle both surface mount technology (SMT) for small signal, and plated through-hole for high power components. If the power electronic uses multiple technologies, the power supply will also need to have specialized high-power connectors and PCBs, along with specified transformer construction and weight on the PCBs.
High Voltage/High Current
If the power supply will be operating from a wall plug, it must be designed to accept up to 265 volts AC (VAC) power. This means that the power supply must be able to handle high inrush current as well as meet IEC-60950 safety requirements for high power density and voltage.
As a subassembly of a power supply, custom-made magnetics, like transformers and coils, need to be treated like a separate product. They require a unique handling skillset, which is often not taught in schools. Attempting to design a power supply with custom magnetics without having this specific knowledge would be a significant reliability risk.
The power supply must meet IEC 61000-4-X standards and FCC/CISPR electromagnetic compatibility requirements. In order to operate reliably, it needs to be able to handle transients, electrical noise, different temperatures, and variations in AC utility. Understanding these specifications and tests will facilitate a robust power supply design that has margin for operation in these environments.
Miscommunicating Reliability Expectations
It was stated above that tight schedules can make it difficult to ensure the reliability of a power supply. Because of these time constraints, a power supply can be manufactured and tested to specifications, but those specs can turn out to be insufficient once more information is known. For example, a power supply may have been tested at 25° C when the customer needed it at 50° C. Miscommunications like this can greatly impact power supply reliability.
A Physics of Failure (PoF) Solution
Taking action early on in the power supply design phase, before physical prototyping occurs, can help to mitigate many of these challenges and help ensure predicted reliability. One way that today’s engineers can achieve this in a time- and cost-effective way is by using Physics of Failure (PoF) based simulations to get a comprehensive understanding of the power supply’s predicted reliability under different use environments.
Rather than conducting lengthy, expensive physical testing, engineers can use design reliability analysis tools, like Sherlock Automated Design Analysis™ Software, to simulate against validation requirements for the power supply. Sherlock can simulate the different types of environments the power supply will normally operate in, while determining the stresses it will experience as a result. Sherlock then uses this data to accurately predict where and why failure could occur, while providing predicted life expectancy.
To learn more about how PoF-based simulation software like Sherlock can help ensure the reliability of power supplies in an efficient way, watch our popular webinar, Best Practices for Implementing Physics of Failure into the Design Process, on-demand by clicking the button below.