This 12 volt battery charger is based on LM317 three terminal regulator manufactured by National Semiconductors which is one of the most used three terminal regulators from the market and can be can be used to design a very simple 12 volt battery charger electronic project using few external electronic parts. Because of the high efficiency provided by the LM317 and number of low parts required this integrated regulator can be used in many power supply circuit projects .
RS sets output impedance of the car battery charger Zout-Rs=(1+R2/R1) .
Using the ISL9220 IC designed by Intersil Semiconductor can be designed a very simple and high efficiency cost-effective battery charger for 1-cell Li-ion and Li-Polymer based portable applications.
The device features synchronous PWM technology, maximizing power efficiency, thus minimizing charge time and heat. The 1.2MHz switching frequency allows use of small external inductors and capacitors.
A simple charge current programming method is provided. External resistors program the fast charge and end-of-charge currents.
A very simple Lithium ion battery charger circuit can be designed using the LTC4071 Li-Ion Polymer Shunt Battery Charger System .
Most Li-Ion chargers terminate the charging after a period of time. The LTC4071 does not have a discrete charge termination. Extensive measurements on Li-Ion cells show that the cell charge current drops to very low levels with the shunt charge control circuit effectively terminating the charge. For improved battery lifetime choose 4.0V or 4.1V float voltage.