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When a laptop loses power and its charger is reconnected, this circuit automatically presses the power button for a short duration, turning the laptop on without manual intervention.
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01
Use an RC differentiator (C1/R2) to generate a low trigger pulse on VCC power-up.
02
Select Rt and Ct to set a pulse width long enough for the laptop's power button hold time (typically 100–500 ms).
03
Drive a relay via a transistor to isolate the laptop's power button pins.
Useful for laptops used as servers, kiosks, or unattended systems that must power on automatically after AC power is restored.