Login Join Maker Pro
Or sign in with

# Current variations.

#### Ravi kant

Oct 11, 2016
5
Hello Seniors.
I'm quite confuse with current!
Since we know that current varies with respect to the load over a fixed voltage supply.
So how can a charger circuit give a constant voltage and current as well or its just my misunderstanding?
I want to understand the logic behind it.
Thank you ☺

#### Alec_t

Jul 7, 2015
3,188
how can a charger circuit give a constant voltage and current as well
It can only do both simultaneously for one specific constant load resistance. A battery on charge is not a constant load, so a charger will usually provide a constant voltage or a constant current, depending on the required battery charging profile.

#### BobK

Jan 5, 2010
7,682
Yes, you misunderstand. If you are talking about a cell phone charger, say rated at 5V 1A, the voltage is held constant, the current is the maximum current it can put out, and it varies with the load.

Bob

#### AnalogKid

Jun 10, 2015
2,661
So how can a charger circuit give a constant voltage and current as well or its just my misunderstanding?
Your understanding. There are several basic kinds of battery charger circuits, based on the battery type/chemistry being charged. The smart ones have several modes and adjust themselves automatically based on monitoring the battery terminal voltage. These can start out in a constant current mode, then shift to constant voltage mode as appropriate.

Unitrode (now TI), Linear Technology, and Maxim make charger controller chips. Read a few datasheets; they have pretty good explanations.

ak

#### Ravi kant

Oct 11, 2016
5
Thank you all for your answers.