Design Note for DN06009/D

Design Note for DN06009/D
5W,CCCV Cell Phone Battery Charger

This circuit presents a very simple, low cost, yet highly effective 5 watt, off-line constant current – constant voltage battery charger for cell phones or similar applications. The circuit is designed around ON’s NCP1014 integrated controller with internal mosfet in a discontinuous mode flyback topology. Current and voltage feedback are accomplished with a single optocoupler as well as providing ac mains isolation. The circuit provides a respectable output V/I load-line characteristic for battery charging over typical temperature variations. The use of an auxiliary Vcc winding on T1, although not required because of the 1014’s DSS circuitry, guarantees very low standby (no load) power consumption (< 300 mW). For maximum simplicity a half-wave input rectifier (D1) is utilized and a conducted EMI filter is provided by C1 and L1. If there are very low output line frequency ripple and/or low ac input constraints, a full bridge input rectifier is recommended. The T1 flyback transformer design is compliant enough for output voltage requirements from 4 to 6.5 volts.

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