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power supply switch

Hi,

I've got a little problem, I'm looking for a special part for my microcontroller project, it is supposed to have main power supply 14V input and battery back-up power supply input and one output for chosen power supply and optionally a signal that can be used as an interrupt signal in the microprocessor informing about the power supply change to back-up. This part should change the power supply to back-up if standard power supply was not connected/unplugged/whatever and send the INT signal. Dunno English names for such parts, but I heard that they can be actually aquired from various manufacturers. I'd be really thankful if someone could guide me/ maybe give a link or tell me how do you call that stuff so I can look myself.

Thanks, Simon

Reply to
frd
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Two diodes will do it:

+------------> Power good signal -------- | | +| +14V--+-->|----+ | Power | D1 | | Supply | | | 14VDC -|----+ | -------- | | +---Gnd +---> Power for uProcessor --------- | | |Battery -|---+ | | | D2 | | 12V +| +12V---->|----+ ---------

The above assumes that the power supply provides a regulated 14 volts.

Ed

Reply to
ehsjr
2 diods won't send an interrupt signal, I know that I can do it with 2 diods, but as I said I'd like to know if there's a piece of electronics that can do those things I mentioned, and prolly few others too... Thanks, Simon
Reply to
frd

Do a search for 'power supply supervisory IC'. Some of these offer the functions you require, with detection of low voltage, rail switching etc.. Cheaper though, will be two diodes, plus a simple single rail monitor, generating an input when the primary rail drops below a set voltage.

Best Wishes

Reply to
Roger Hamlett

The schematic shows how the two diode approach *does* create an interrupt. Look at the power good signal. Program the uP to recognize that AC power has been interrupted when that signal has dropped. Did you want detail on that?

You can get more complex functions from a different approach, as Roger mentioned in his reply, but the two diode approach is the easiest and cheapest solution to your original question.

Ed

Reply to
ehsjr

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