Here is a tried and tested sample circuit of a Li-Ion battery charger that can be used to charge any 3.7V Li-Ion battery using a 5VDC (USB, Solar Panel…) power supply. At the heart of the circuit is ...

Figure 3 This circuit diagram shows an isolated resonant converter with an asynchronous rectifier. Source: Vishay At the center of the charging system is the isolated DC/DC converter, which is used to ...