Determining which external power supply to use can be a difficult task.
In the past, there were AC/DC unregulated units with single ac input. The output voltage would swing up and down with change in input voltage.
The output voltage would swing up and down with change of load current. It was almost like hitting a moving target.
The new breed of external power supplies will vie with the older linear type for pricing. The new breed will also meet the new Green Power initiatives and CEC (California Energy Commission) requirements. So for many good reasons, the older linear type is being phased out.
As the majority of today's external power supplies are switch mode types, they are regulated, the task has gotten easier. They are mostly universal input covering from 90 VAC to 250 VAC at line frequencies from 47 - 63 hertz. That takes care of the output voltage swing problem due to change in AC input. They are also mostly regulated DC output. Meaning the output voltage stays constant regardless of output load current drawn providing you stay under the maximum output rating for the supply. That takes care of the output voltage swing due to changes in output load current.
→So, now your choices are few, in fact just two. What DC output voltage do I need? How much output power do I need?
Since your choice of output voltage is most likely fixed and determined by the input voltage needed by the device you are powering that takes care of one of your two choices right away. Now, you last, and really only choice is how much power do I need? This is going to be some minimum amount that your device will require in order to operate.
For example, your device requires 5 VDC in order to operate. So, you now know you need an external power supply with a 5 VDC output. Your device states that it requires 2 Amps in order to operate. This means that you need at least a 10 Watt (5 VDC x 2 Amps=10W) related supply. So now you search is narrowed down to 5 VDC power supplies rated at 10 W or higher output.
Like everything else, power supply pricing is based on the output power rating of the unit. So your search should focus on the closest power supply you can find with a 5 VDC output at am minimum of 10 Watts of power. However, you have many more choices since the output voltage is fixed at 5 VDC with the regulated supplies, you can use a 20 W or a 30 W unit if your search does not turn up a 10 W unit.
So what used to be a difficult task left to a component engineer has turned into a easier task not requiring an electrical engineering degree to complete.
Read More Knowledgebase Articles on power supplies at peaktopeakpower.com
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