Research And Design Of Ultra-fast Charger For NiMH Battery

Nickel-Metal Hydride rechargeable batteries is widely used in various fields such as electric tools and toys,digital products, medical equipments, remote communicated device, hybrid electrical vehicle fields etc. Because it has many advantages, such as high energy density, high power density, environmentally friendly, can stand higher temperature, safety, long service life, big discharge current, and inexpensive. But its recharge power supply has some disadvantages such as unacceptable charging time, short of functions and inconvenient, make battery tend to be polarized, overcharged or undercharged. Hence, it got the important sense to develop a kind of battery charger with multifunctional, intelligentized and short charge times.The positive and negative pulse battery charger for Nickel-Metal Hydride rechargeable battery design in this project based on quick charge Mass laws. The charge procedure showed as follows: a tiny current pre-charge process, positive and negative pulse charge process, maintain charge process.-â–³V, temperature and time control the charge procedure. As for the hardware design, power supply integration chip TOPSwitch-GX series TOP246Y chip was choose to be the hard core of the switch power, count on it's high density integrate circuit make the power more reliable , excellent electromagnetism compatibility ,lower cost ,higher power supply efficiency, and shorten R&D period.The product frame was designed by PI Expert Suite. In addition, periphery circuit and transformer are so important that I gave a minutely calculated, Include input filtrate circuit, output filtrate circuit, feedback circuit, protective circuit, power factor emendate circuit. The hard core of the control system is micro-electronics controller MC68HC08JL3. Design temperature, voltage sampling system and LED charge status display device which by made use of it's integration A/D converter, LED driver were designed.To avoid the situation in case of overcharge or undercharge, the charger was introduced to some techniques such as negative voltage increment, max temperature inspect, time control. Ensure the battery to be a longer service life and reliability. Heat dispersion is also a part and parcel, especially in power chip. Further more, electromagnetic compatibility is significant capability guideline of the electronic product. In many countries, electromagnetic compatibility is a compellent certificated item. In this paper, the source of electromagnetic interference, couple path and couple medium were analyzed. To reduce the electromagnetic interference, this embody in the design of filtration, shield, grounding, isolation, PCB plate layout, and component selection, transformer manufacture. Finally, the charger went for a low electromagnetic interference, efficient conversion.