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Universal isolated power supply

Universal isolated power supply

Universal isolated power supply

(OP)
Hi,

I need to design an 5Vdc at 1amp power supply.  This supply need to have an universal input and be able to support operating temperature of -40 to +80 C.

The problem with this limitation is that I cannot use switching supply cause of the temperature.

Anyone have a suggestion?

Thank in advance

RE: Universal isolated power supply

You could start by giving better requirements:

"universal" means ???  anything from 1uV to 1MV?

Why is switching eliminated by temperature?

Line Regulation?

Load Regulation?

TTFN

RE: Universal isolated power supply

(OP)
Universal means that I could use 120 or 240V at the input and the power supply still work.  The reason why I shoul eliminate the switching supply is that in this kind of power supply we need a 400V capacitor at the input. The problem with 400V Capacitor is that the maximum operating temperature is -25 C.

I want to use this power supply for a control system that use an microchip microcontroller.

Hope this clarify my first e-mail

RE: Universal isolated power supply

I would suggest that you go with a linear power supply.  Not only will this be cost effective but also simple in construction and quite durable.  You'll need a transformer, full wave bridge rectifier, a 5V regulator and a couple of capacitors.    MC 7805 voltage regulator by ON Semiconductor appears to meet you specifications.  It operates from -40 to +125 C and is capable of outputting in excess of 1A at 5V.  Most rectifiers I've worked with do operate beyond your temperature requirements, so finding a rectifier shouldn't be a problem.  A 100 V rectifier rated at 2 amps should be more than sufficient.  As for a transformer, I would recommend you get one with a center tap and wire your power supply circuit accordingly so that you could change between 110V/220V with just a flip of a switch.  As for a capacitor, you can use a 1000uF @ 50V electrolytic capacitor on the input of the voltage regulator and a 100nF ceramic capacitor on the output.  Finally, you may want to add a heatsink on your regulator to prevent it from overheating.

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