Practical constant current charger circuit

Published:2011/5/24 3:26:00 Author:John | Keyword: constant current charger | From:SeekIC

This circuit is actually a constant current source. Nuclear device is an integrated three-terminal adjustable regulator LM317T. Within the sufficient power supply voltage, LM317T can maintain a 1. 25V higher voltage of the + Vout than that of the ADJ. See the connection in the figure. The terminal end of ADJ is connected directly to rechargeable batteries. However, the internal resistance for ADJ terminal end is large (the current does not exceed 50μA under normal circumstances), so the circuit can be approximately regarded as an open circuit. But it can sample out of the voltage. If LM317T improves the voltage on the + Vout terminal end to be higher than that of ADJ terminal end of about 1.25V, the resistor cross-connected to the + Vout and ADJ can have the current of 1.25V/25.5Ω = 0. 05A = 50mA. (25.5Ω is the total resistance for the situation when R1 and R2 are parallel placed with the opening switch). Such current flows through the battery to charge the battery within a constant current.



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