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Battery Backed external power supply

We have a small unit which has a external power supply of 7V. This unit draws around 100mA. We have been asked to supply some sort of battery backup for it. There is no ups to hand so what we are looking for is a DC small DC supply 7 to 15V which can power the unit from the mains and keep powering the unit for around 2 hours on power fail. This could be a external battery that connects in line between the current power supply and the unit, or a totally new power supply with integrated battery. The batterys will need to be accessable to allow them to be changed once a year. I know I could design and build something but wondered if there is anything on the market. We would want several hundred of these. Any advice/help would be appreciated.

Thanks

Reply to
steve.jones
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This can be setup really simple: feed your circuit from tha 15V (must be higher than battery voltage) supply through a diode. Also connect a 12 lead-gel battery to the circuit through another diode. When the power fails, the battery takes over. You can trickle-charge the battery from the power supply as well though a suitable resistor.

Meindert

Reply to
Meindert Sprang

Depending on what the user means by 'small', a 9V alkaline battery (with about 600mAH capacity) and a diode might work. An unstated specification is how often they expect the power to fail and whether they want to build the battery into the same housing as the device.

Mark Borgerson

Reply to
Mark Borgerson

TI makes a line of switching regulators. (switching for efficiency) They're in the DIgiKey catalog.

A battery and a diode (perhaps 2 diodes) for isolation.

Set it up so that external power is high enough to keep the switcher supplying 0%. THen when the external goes away the switcher will take over.

george

Reply to
GMM50

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