How do intelligent power systems manage dynamic input, plus a potentially dynamic load?

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I often wonder, how does my laptop’s charger and battery control work? Because I’ve been in situations where I’m charging my laptop from a weak charger that’s under-rated for the laptop’s draw. For example, I have a 20W PD charger, and my laptop draws between 15-45W depending on what I’m doing. If I’m just doing some simple word processing work, my battery can even get a little charge while plugged into my charger. But if I play a 3D game, then my laptop maxes out the 20W PD charger, then supplements from the battery.

How does my laptop know how to split the power demand, and how does it draw exactly the right amount of power from the battery?

In: 2

Alright, let’s imagine a playground scene to understand this better:

Imagine your laptop is like a big thirsty elephant. This elephant loves to drink water. The water is the power or electricity.

Now, you have a water fountain (your 20W PD charger) that can only provide a limited amount of water at a time. Sometimes, the elephant can get all the water it wants from the fountain. Like when you’re just typing up something – that’s like the elephant sipping water calmly.

But when you play a big 3D game, the elephant gets really thirsty and wants to drink a lot more water. The fountain alone can’t keep up, so the elephant has a backup: a big water bottle (your laptop battery) on its back.

If the elephant needs more water than the fountain can give, it knows to take some water from its bottle. So, if the fountain gives 20W and the elephant needs 45W, it will take the remaining 25W from its bottle.

Your laptop has a smart system (like the elephant’s brain) that always knows how thirsty it is and can decide how much water to take from the fountain and how much from its bottle.

So, even if the fountain can’t provide all the water (power) the elephant (laptop) wants, the smart elephant knows to take the extra it needs from its bottle (battery). That way, it always gets the right amount of water it needs!