The following is a circuit diagram of the lithium battery charger circuit diagram Lithium battery charger circuit diagram SHAOXING COLORBEE PLASTIC CO.,LTD , https://www.colorbeephoto.com
Photocoupler 
The following is a circuit diagram of the lithium battery charger circuit diagram Lithium battery charger circuit diagram SHAOXING COLORBEE PLASTIC CO.,LTD , https://www.colorbeephoto.com
Photocoupler