Sunday, April 5, 2009

Switch-Mode Battery Charger Circuit

Fast, High Effi ciency, Standalone NiMH/NiCd Battery
Charging Circuit

Figure 1 shows a fast, 2A charger featuring the
high effi ciency LTC4011 550kHz synchronous buck
converter. The LTC4011 simplifi es charger design by
integrating all of the features needed to charge Ni-based
batteries, including constant current control circuitry,
charge termination, automatic trickle and top off
charge, automatic recharge, programmable timer,
PowerPath control and multiple status outputs. Such a
high level of integration lowers the component count,
enabling a complete charger to occupy less than 4cm2
of board area.

Battery Charger Delivers 2.5A With >96% Efficiency
Battery chargers are usually designed without regard for
efficiency, but the heat generated by low-efficiency
chargers can present a problem. For those applications,
the charger of Figure 1 delivers 2.5A with efficiency as
high as 96%. It can charge a battery of one to six cells
while operating from a car battery.

Figure 1. Modified feedback paths transform this switch-mode
power-supply circuit for notebook computers into a
high-efficiency battery charger.
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