Posted on Nov 15, 2012

To prevent battery damage due to over -disc barge, a low-voltage detector and switch should be included in the design of the battery backup circuit. The detector circuit should consume extremely low current. The switch should exlnbit a low-voltage drop and be easy to control. R1 and D2 provide a trickle charge for the battery. Chosen for its low forward voltage drop, Schottky diode D3 prevents forward polarization of the diode incorporated in Ql.

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When the battery voltage is above approximately 8 V, the output of U1 is low and Ql is turned on. If the battery voltage falls below 8 V, the output of U1 increases and turns off Ql.

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