Monday, January 9, 2012

When powering multiple DUTs, should I use multiple small power supplies or one big power supply?

If you have to provide DC power to multiple devices under test (DUTs) at the same time, you will have to choose between using multiple smaller power supplies to provide power to each individual DUT (Figure 1) or one big power supply to power all of the DUTs at once (Figure 2). As will most choices, each has advantages and disadvantages. However, in this case, the advantages of choosing multiple smaller power supplies seem to outnumber those for the single bigger supply.

One of my colleagues, Bob Zollo, wrote an article on this topic that appeared in Electronic Design on October 12, 2011. Here is a link to the article:

Below is my summary of the contents:

Advantages of choosing multiple smaller power supplies
• Enables individual DUT current measurements without additional hardware
• Enables individual DUT voltage control
• Enables individual DUT shutdown upon DUT failure
• Enables individual DUT galvanic disconnect with relays inside power supply
• Prevents one DUT inrush current from disturbing other DUT’s voltage
• Prevents one DUT failure from affecting other DUT testing
• Isolates power supply failure to one DUT instead of affecting all DUTs

Advantages of choosing one big power supply
• Power supply hardware is less expensive
• Less power supply hardware to calibrate

The disadvantages of the smaller power supply choice are that the total power supply hardware is more expensive and is a larger quantity of hardware to calibrate. The disadvantages of the one big power supply are that it does not provide any of the advantages listed for the smaller supplies.

So you can see that the multiple smaller power supply choice has more advantages over the one big power supply choice. For the one big power supply choice, current monitoring and relays can be added in series with each DUT; however, this will contribute significantly to the cost of the system. If your application does not require you to monitor or control the power to each of your DUTs individually, you may be able to use the less capable one big power supply approach. Otherwise, use multiple smaller power supplies to get all of the performance, measurement, and control you need to test your DUTs.

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