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Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

Your friend is right in that you cannot charge a lithium ion cell with just any old voltage. The battery university goes into some detail about it. Short form: A single lithium ion cell has a voltage ...
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5 votes

Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

Obviously the 9V will not be directly put on the battery. That's because lithium batteries cannot be charged safely by connecting them to a constant voltage anyway. Your mains adapter which for ...
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4 votes
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What prevents old (low current) USB cables from catching fire if used to Quick Charge modern devices (at high-current)?

As a generic answer, the USB specs, and QC specs. The USB specs require that a PD source detects the cable type from the plug. If the plug does not identify as PD capable plug then PD will not be used....
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4 votes

What prevents old (low current) USB cables from catching fire if used to Quick Charge modern devices (at high-current)?

First of all, an old cable has VBUS, GND , D+ and D-. This is only four wires. The full 100W power draw is only possible when using USB 3.0 compatible cables, which have 8 wires in them (two extra ...
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4 votes
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If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

Generally, yes. Devices in parallel share the voltage, not the current. Devices in series share the current, not the voltage. The only way to connect them in series is to connect the positive of one ...
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3 votes

Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

It's a programmable source to a Buck CC Charger Regulator. You are both correct, yet don't know how it is used. The programmable 9V charges an inductor to the required current and then discharges ...
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2 votes

If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

I'm assuming that I can I just use a single 12V 4A power supply to power them both? Quick answer: Yes By theory, components connected in parallel will utilize the same amount of voltage while drawing ...
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2 votes

Peak current of inrush limiting inductor?

The maximum current will depend upon where in the AC cycle the power is turned on. simulate this circuit – Schematic created using CircuitLab If the power switch is closed at the zero-crossing ...
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1 vote
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Clock out drive strength - Current

Usually having a variable drive strength allows a chip adjust the strength based on need. Faster signals need faster edges which can be achieved with stronger drive ability, but it requires more power....
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1 vote
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Peak current of inrush limiting inductor?

TL;DR Your initial question bears no resemblance to the actual design. The soft-start on the feedback will greatly reduce the stress on the components. This is a transformer and optoisolated forward ...
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1 vote

Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

I think the trick with the higher voltage on the USB cable is there to prevent the wires of the cable to become too hot. If a power supply delivers 27 Watt, that would be more than 5 Amperes at 5 Volt;...
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Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

Most cell phone charging works the same as EV level 1-2 charging. That external thing is not a charger! https://youtu.be/RMxB7zA-e4Y?t=122 The connection (USB cable; J1772 cord) is just a fat pipe to ...
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1 vote

Off-grid computing

Say you got 2640W peak solar panels... On overcast days, the power you'll get versus all your electrical loads seems... wildly optimistic. For example, over the last few months (jan-may) my 3kW peak ...
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If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

Current is typically thought of as being 'drawn' from the power supply by a load, at least when it is some kind of active electronic device like a USB hard drive or Android box. Only in the case of, ...
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1 vote

If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

In regards to your question on the 24V 2A option. It wont work in your case, but conceptually it could work if the two loads were closely matched in terms of power consumption and were simple like ...
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Graphing modes of BJT

In this type of graph the DC load line extents are based on two conditions, when the collector-emitter junction is an open circuit, and when it is a short circuit. The point where the DC load line ...
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1 vote
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Calculating the reading on ammeter \$A_1\$: why am I incorrect?

Ohm's law states U=R*I (or I=U/R). Where you got it wrong is on which "U" (ie which voltage) is the one to use. The voltage U is the voltage drop across the resistor R (through which flows ...
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1 vote

If two devices both require 12V 2A power can I use a 12V 4A power supply to power them both?

Short answer: yes, you can power both with a 12V 4A supply and NO, you can't use 24V 2A supply, it will fry everything most likely. Long answer: If one or both devices is sensitive to noise (eg an ...
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