12V TRICKLE CHARGER ELECTRONIC PROJECT
The 12v Trickle Charger circuit uses a TIP3055
power transistor to limit the current to the battery by turning off when the
battery voltage reaches approx 14v or if the current rises above 2 amp. The
signal to turn off this transistor comes from two other transistors - the BC557
and BC 547. Firstly, the circuit turns on fully via the BD139 and TIP3055. The
BC557 and BC 547 do not come into operation at the moment. The current through
the 0.47R creates a voltage across it to charge the 22u and this puts a voltage
between the base and emitter of the BC547. The transistors turn on slightly and
remove some of the turn-on voltage to the BD139 and this turns off the TIP3055
slightly. This is how the 2 amp max is created. As the battery voltage rises,
the voltage divider made up of the 1k8 and 39k creates a 0.65v between base and
emitter of the BC557 and it starts to turn on at approx 14v. This turns on the
BC 547 and it robs the BD136 of "turn-on" voltage and the TIP3055 is
nearly fully turned off. All battery chargers in Australia must be earthed. The
negative of the output is taken to the earth pin.
CLICK ON THE IMAGE TO ZOOM IN
