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My monitor comes with an adapter , which accepts electricity from wall, ranging from 110V-240V. I am wondering how it could output a same amount of current despite a dynamic voltage?

Arkyo
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    They have in-built regulator. – Marko Buršič Jun 20 '18 at 12:50
  • 1) with the exception of LED drivers, power adapters output a constant **voltage**, not a constant current. 2) basically the adapter has an internal reference voltage, it compares the output voltage to that reference voltage, that generates an error signal which is used to control another part of the circuit to increase or decrease the voltage. To fully understand how this works some serious study into electronics is needed. – Bimpelrekkie Jun 20 '18 at 12:52

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Isolated 220-110 to low voltage supplies are often switch-mode power supplies using a small transformer with a high frequency. If you change the duty cycle of the pwm controlling a power transistor you can change the output voltage. Most switch mode chips have an enable input. The reservoir capacitor on the output can serve as buffer to smooth out the enable and disable cycle.

With some measuring and feedback circuitry (using an opto-isolator to communicate back to the high voltage side) and you can then adjust that duty cycle to emit a constant voltage, a constant current, a current-limited constant voltage or ...

ratchet freak
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  • On the adapter it states: INPUT: 100-240V , 1A MAX OUTPUT: 12V 3A – Arkyo Jun 20 '18 at 14:29
  • @Arkyo, read [Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/q/34745/6334). The current rating is a maximum, not a fixed output value. – The Photon Jun 20 '18 at 15:28
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The maximum current would typically be limited by the components selected for the internal regulator circuitry, not by the input voltage or current (since a typical wall socket can supply around 1500 to 2000W, and I doubt your adapter is rated that high). The actual current depends entirely on how much the device it's powering takes.

Cristobol Polychronopolis
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Typically they rectify to peak voltage AC to DC then DC-DC converter to step down.

There will be using a fixed reference diode voltage to regulate the output.

Tony Stewart EE75
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