Power supply operation is closely linked with its ambient temperature. Even if you plan to operate your power supply in a conventional commercial environment, your unit may encounter heat in various ways that can ultimately affect its performance and reliability. That's why power supply manufacturers establish an operating temperature range and include it on the data sheet.
However, many factors can cause a power supply to operate outside even a wide temperature range and cause problems. This blog post — the third part of our series on operating power supplies outside their specifications — will explain why the operating temperature is a critical specification while also offering strategies to address thermal management during the selection process.
Reasons for Thermal Issues
Designers don't always have the luxury of specifying a power supply that is limited to a narrow operating temperature range that can otherwise suffice in a room with benign ambient temperatures. For example, if the power supply must operate in a hot, sunny or arid environment, the location will influence the ambient temperature. In addition, the power supply's load requirements, efficiency, enclosure type and ventilation can cause the unit to operate outside its temperature limits. When a power supply operates higher than its temperature specifications, a host of problems can occur such as reduced component lifetimes, increased output ripple and its associated electrical noise, and over-voltage issues.
And, if you're specifying an external power supply, its surface temperature can make it hot to touch or even pose a fire risk. This problem is especially concerning for medical applications, where patient comfort and safety are paramount. It's also important to remember that operating a power supply at lower-than-specified temperatures can also hinder performance. Implications can include poor output regulation, an increase in the output ripple or inability to start up.
Choose a Power Supply With Thermal Limits in Mind
When it's time to select a power supply, there are features to look for that can help your unit run within its temperature limits.
- A wide operating temperature range. Power supplies with a wide operating temperature can be desirable for harsh or outdoor environments where high or low temperatures are possible, and they may not require modifications to remove excessive heat. In addition, a higher temperature specification can help avoid derating output power which can otherwise be necessary to avoid high-temperature operation.
- Overtemperature protection. A variety of events like high ambient temperature, poor ventilation and power surges can raise the temperature of a power supply. That's why many power supplies come with an overtemperature protection (OTP) feature that shuts down the unit until the temperature returns to a specified threshold.
- Heat removal. Because power supplies give off heat, they often come with built-in mechanisms such as fans, heat sinks or thermal plates. Other power supplies rely on convection and liquid cooling. Selecting the right cooling method is often system dependent and will involve trade-offs such as power and noise requirements, and enclosure or frame construction, to name a few.
Two examples — the Polytron UIPCP industrial and MUIPCP medical power supplies — have an open-frame design that take advantage of free-air convection to keep its components cool, and they also offer overtemperature protection to prevent operation at high temperatures.
Work Closely With Your Power Supply Manufacturer
As you select an ideal power supply for your device, it is important to work with a supplier that can offer a variety of options to meet your thermal management goals. At Daburn, our Polytron Devices division offers a wide range of power supplies for a variety of markets — each with its own operating temperature needs, including industrial, military, EV charging and medical sectors. And if a power supply cannot meet your exact temperature or performance requirements, we stand ready to suggest modifications or external cooling methods and design strategies to best keep your power supply cool.
For more information about Daburn Electronics Polytron Devices power supplies, please visit our web site.