AIC1781

The AIC1781 fast charge controller IC is designed for intelligent charging of NiMH or NiCd batteries without the risk of overcharge. −V detection (-0.25%), 0V detection (peak voltage timer) and T /t detection are the primary methods employed by the AIC1781 to terminate fast charge.

The fast charge can also be cut off by maximum battery voltage and maximum battery temperature detection along with the safety timer to prevent charging under fault conditions of the charging system or the battery itself.

Both T /t and −V detection methods have been proved powerful in terminating fast charging for NiMH and NiCd batteries. The AIC1781 utilizes the combination of these two methods to achieve reliable decision of ending fast charge and prevent misaction caused by using −V detection alone under certain conditions. Fig. 1 shows an example of charging curve of a battery charged by a fluctuating current from a NiMH battery charger which uses the AIC1781 controller IC to achieve optimal charging. This technique, in cooperating with the 0V detection (peak voltage timer), is particularly suitable for NiMH batteries, whose voltage drop is hardly significant yet temperature rises rapidly. The T /t or −V detection circuitry may be disabled independently for different applications, such as system-integrated chargers, chargers with varying charge current, or battery packs lack of temperature sensing thermistor.

The safety timer period, mode of battery temperature protection, battery voltage protection range, pulsed trickle charge duty, and LED display mode are all adjustable or selectable. Dischargebefore- charge function is included to get rid of memory effect of NiCd batteries without the risk of overdischarging. Test mode is provided for charger manufactures to dramatically reduce production test time.