Bellow circuit is an uninterrupted power supply(4.7 Vout after regulator) with auto shutdown when the battery is low. I am using a 6-volt lead acid battery with 9v charger.

I am looking for an Idea to help me to avoid D4 because I would like to shut down the system when the battery is 5v and not 5.7v. since I can not find a regulator that can provide 4.7 when the input voltage is less than 5V.

if you think this is not good design, I will appreciate you provide a better way.

(The LEd symbol is meant to be a pump (150ma max))

enter image description here

  • \$\begingroup\$ Take a look at US Pat 5,028,858, it describes something similar using a Z Diode as Low Voltage Cut Off. \$\endgroup\$ – Alexander von Wernherr Aug 16 '18 at 13:45

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