design of battery charger
Battery charger are used to charge batteries. There are several types of battery charger ICs. Linear chargers use a voltage-controlled source to force a fixed voltage to appear at the output terminal. Switching chargers use an inductor, transformer, or capacitor to transfer energy from the input to the battery in discrete packets. Some battery charger ICs are designed to charge lithium (Li) ion or lead acid batteries. Others are suitable for charging nickel-cadmium (NiCd) or nickel-metal-hydride (NiMH) batteries. Important features for battery charger ICs include over-voltage protection and over-current protection. Devices with a soft-start feature condition the battery for several minutes before performing a fast charge. Devices with a charge status indicator have a built-in monitor that displays the amount of current supplied and/or the amount of charge applied. In response to concerns about the environmental impact of using lead (Pb) in solder finishes, some battery charger ICs do not contain lead in any form.
Important performance specifications for battery charger ICs include the maximum number of cells, supply voltage, quiescent current (IQ), maximum charge current, voltage accuracy, and operating temperature. Batteries consist of units called cells, each of which contains electrodes. Using a battery sends electrons along a conductive path from the anode (-) to the cathode (+). Charging a battery changes the flow of electrons, causing the electrochemical process to occur in reverse. Battery charger ICs with relatively high supply voltages and quiescent currents are well-suited for batteries that contain a relatively large numbers of cells. For both low charge and high charge devices, the maximum charge current is usually expressed in amperes (M). Voltage accuracy is expressed as a percentage deviation from a nominal value. The operating temperature is a full-required range.