BEC operation with input volts below out put volts.

everydayflyer · Nov 02, 2007, 10:06 PM

This question came up in the Batteries and Chargers Forum.

As I read / understand the pdf spec. sheets it appears that the regulators DE uses requires input voltage to be output + 1.3V.

Question is what happens if a 6V BEC is being used and input drops to below 6 volts?

Does it just pass the available voltage?
Supply available voltage minus X?
Shuts down and passes zero volts?

With the Spektrum receivers being prong to shutting down at just below 4 volts and the more common usage of A123 and other LiIon high current cells which can have severe voltage drops under heavy loads inquiring minds want / need to know.

Charles

Afroman · Nov 05, 2007, 11:49 AM

The output voltage will become the input voltage minus the dropout voltage. There isn't a sudden shutdown - the voltage will just start to drop as the input drops. The dropout voltage will vary depending on the amount of current you are pulling, but 1.3V is fairly common. To ensure a 6.0V output with a good safety margin we recommend you keep the input voltage above 8.0V (hence why ParkBEC 6V is rated for a minimum of 3s lithium).

Nov 02, 2007, 10:06 PM	#1
everydayflyer Southern Pride Haralson County GA. USA Joined Oct 2004 34,186 Posts	BEC operation with input volts below out put volts. This question came up in the Batteries and Chargers Forum. As I read / understand the pdf spec. sheets it appears that the regulators DE uses requires input voltage to be output + 1.3V. Question is what happens if a 6V BEC is being used and input drops to below 6 volts? Does it just pass the available voltage? Supply available voltage minus X? Shuts down and passes zero volts? With the Spektrum receivers being prong to shutting down at just below 4 volts and the more common usage of A123 and other LiIon high current cells which can have severe voltage drops under heavy loads inquiring minds want / need to know. Charles

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Nov 05, 2007, 11:49 AM	#2
Afroman Cat lover Joined Mar 2005 68 Posts	The output voltage will become the input voltage minus the dropout voltage. There isn't a sudden shutdown - the voltage will just start to drop as the input drops. The dropout voltage will vary depending on the amount of current you are pulling, but 1.3V is fairly common. To ensure a 6.0V output with a good safety margin we recommend you keep the input voltage above 8.0V (hence why ParkBEC 6V is rated for a minimum of 3s lithium).