Specify a Power Supply That Handles Unique Output Current Conditions

A power supply's output current rating will often determine the size and cost of the unit you need. Not surprisingly, this dynamic can create a potential pitfall when choosing a power supply: Specifying a unit that meets the application's minimal current requirements without also considering how it can handle excessive currents. Undoubtedly, operating a power supply beyond its limits is risky. At Daburn, we do our best to eliminate such risks and stand ready to help you satisfy your performance needs with a safe, reliable unit. This blog post will offer some tips for obtaining a power supply that gives you the performance you require while staying within its output current limits.

In the first post in this occasional series on a power supply's operating limits, we explained how undervoltage can cause components to overheat and the power supply itself can sustain damage. Like undervoltage, thermal issues and component degradation are the consequences of exceeding your application's output current requirement. That's because the higher output power dissipates to nearby components, causing them to overheat, degrade or fail. The power loss also hinders the supply's performance and efficiency. Additional problems may include:

• Frequent shutdowns due to transient currents.
• Increased EMI.
• Operation outside of load regulation limits, which may also occur when a power supply operates under its minimum current rating — if it has one.

Tips To Meet Your Application's Output Current Requirement

In order to select a power supply that meets your current requirement, follow these tips and best practices.

• Derate current. Lowering, or derating a power supply's current rating can account for conditions that may affect the output current, such as extreme temperatures.
• Account for transients. When specifying a power supply, make sure the rated current limit allows for possible transients, such as from surges. In addition, many power supplies offer a Peak Power feature, which allows them to deliver higher power than their rated output power for a short duration when, for example, components elsewhere in the circuit draw more current at start-up than when operating continuously. Daburn's Polytron KUIP300 AC-DC industrial power supply is one such example. While it offers 300 watts of power, it is also capable of delivering 360 watts peak power for 5 seconds (typ.) when temporary load spikes occur.
• Look for built-in protections. To prevent overcurrents from damaging the device being powered, many power supplies come with built-in protections. Examples include constant current limiting which, during overloads, prevents the output current from exceeding a specific limit and lowers the output voltage until the overload ends, and fold-back limiting, which lowers both the output current and output voltage to acceptable levels. Hiccup-mode current limiting lowers the output voltage to zero and returns its normal voltage after a brief interval.

Tailor a Power Supply To Solve Over- or Under-Current Challenges

While power supply manufacturers offer many units to choose from — often with built-in protections — there may be times when a standard supply may not match your application's current requirements. At Daburn, our engineering staff can work with you in modifying a standard unit with an appropriate current limiting method, or a means of drawing more current, if necessary. Simply send us your tech specs and we'll suggest solutions for your unique requirements, create evaluation samples and safety-test the unit.

For more information, please visit our web site or contact us.