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			| Power 
		Supplies: UPS
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							Basic UPS:  |  
							| Build a UPS for USB devices: 04/11/2002  EDN - 
							Design Ideas /    Portable systems often include 
							circuitry that derives power from an external 
							source, such as USB. When the system disconnects 
							from the USB supply, a battery takes over and 
							supplies current via a dc/dc converter. A diode-OR 
							connection |  |  |  
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