suggestions on control the charging current?

Projects General Guidance
1

Dear all,

I want to design a circuit that can control the charging current. The circuit is used to charge the battery (e.g. 3.7V Li-ion battery from the mobile). This charging current should be controlled proportionally to the control signal I have acting as the input. The input signal I have is a PWM modulated voltage signal from arduino (e.g from pin 9). I want use this signal to control the charging current of my circuit. For example, when the PWM signal is 0V, then the charging current should be zero or almost zero. Similarly, if the PWM output is 5V from the arduino, then the charging current should be the maximum charging current specified by the battery, for example, 1.2A. In addition to this design, I also have a constant DC voltage source. I am not quite sure is there any dedicated circuit (i.e. from Sparkfun or any related products) that has already got the functions as I described above. If not, can anyone give me some suggestions on how to achieve that?

Thanks a lot.
Victor

2

use a transistor.

3

Lithium batteries must be charged according to a strict scheme or they will be destroyed. Charge control ICs and breakout boards are available for experimenters from SparkFun and other suppliers. The batteries can also be destroyed by over-discharging so each battery should be equipped with a "battery protection PCB". These are available very cheaply from all-battery.com: Tenergy Battery Pack PCB