Universal isolated power supply

[Assault]

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

 

[IRstuff]

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

 

[Assault]

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

 

[eemotor]

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.