"Lockout" load switch with a 4093

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When the USB pin is low and the widget is not connected to the USB LiPo charger, the main load's boost converter shutdown pin is pulled low (off) by the output of the flipflop section U1.

Pulsing button 1 turns the main load on and pulsing button 2 turns it off again.

If the widget's main load is powered when USB voltage is connected, differentiator C1/R5 pulse the input of U2 low, flipping the flop and shutting down the converter so the circuit doesn't load the charger. The connection of the "on" button supply to the output of gate section U4 ensures that the main load can't be switched on when charger power is connected.

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