Managing power dissipation in portable battery charger applications

Dissipating battery-charger power outside small portable products makes them operate cooler. Because of their small size, most of these applications have strict limitations on the available space and power dissipation and tend to use lithium-ion (Li-ion) batteries. This paper describes a charger design topology that moves the bulk of the power dissipation of battery charging out of the portable device but leaves the charger circuit embedded in the application. The performance of a circuit with high-accuracy voltage regulation, battery conditioning, temperature monitoring, and charge-status indication is analyzed for the effects of power dissipation, circuit area, and charging time.