Electricity: battery or capacitor charging or discharging – Diverse charging or discharging rates for plural batteries
Reexamination Certificate
2000-04-06
2001-05-08
Tso, E. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Diverse charging or discharging rates for plural batteries
Reexamination Certificate
active
06229283
ABSTRACT:
The present invention relates generally to a voltage/current regulator and a method for regulating the charging of a rechargeable battery in a portable electronic apparatus.
Rechargeable batteries, when in a charged condition, are used to provide electric current to power a variety of electrical appliances, such as industrial and consumer applications, including mobile telephone apparatuses or other similar electronic devices. However, when the battery is discharged, it needs to be charged. Battery charging implies generally applying of an appropriate electric current to the battery for a certain time.
The charging current required depends on which type of rechargeable cells or batteries are used, and with some types of rechargeable batteries the value of the current has to be varied during the charging process. Therefore a charging programme are used in order to regulate the current during the charging.
Lithium - or Li batteries are commonly used batteries in the above mentioned appliances because of its light weight, high-voltage, high energy density, flat discharge characteristics, and long shelf life etc. However, in some stages in the charging cycle of Li-batteries it is required to have a linear regulation of the charging current. Therefore, a transistor is used for controlling the current and during the regulation it has a voltage drop from the drain to the source. Hence, heat is generated in the transistor and power is dissipated.
Due to the cost and board space limitation reasons it is desired to use a transistor which is as small as possible. However, a small transistor can handle less amount of power dissipation. Consequently, the current must be set low in order to cover all cases regarding to the temperature, the voltage level and the charging current. This means, however, that in many cases the current is unnecessarily low, resulting in longer charging times.
Another alternative is to apply a higher current in order to reduce the charging time for normal cases. However, in some cases the current is too high, resulting in a high temperature in the transistor and in the phone that in some cases irritates the user of the phone and also reduce the lifetime of the transistors.
SUMMARY
Therefore, it is an object of the present invention to provide a voltage/current regulator and method for battery charging in a portable apparatus which overcomes the above-mentioned problems.
This is accomplished with a voltage/current regulator apparatus according to the invention, which is regulated to dissipate a constant power, wherein a maximum allowed current regarding to power dissipation and temperature in the apparatus is used in the charging current transistor in the apparatus.
An advantage of the present invention is that the charging current is dynamically adjusted to the actual incoming voltage and the temperature inside the phone and the battery. Consequently, the minimum charging time is always achieved although the maximum dissipation is never exceeded.
Further, there is no inconvenient temperature increasing in the phone, which is important particularly regarding to very compact phone designs, in which even a small increase in temperature in the phone is noticeable by the user. In general it is an advantage of the present invention to keep the increase in temperature due to the charging as low as possible.
REFERENCES:
patent: 3979658 (1976-09-01), Foster
patent: 4341988 (1982-07-01), Small
patent: 4644247 (1987-02-01), Burmenko
patent: 5576609 (1996-11-01), Brown
patent: 5703470 (1997-12-01), Baranowski et al.
Andersson Rickard
Forsberg Charles
Hansson Magnus
Kalogeropoulus Sarandis
Mercke Johan
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
Tso E.
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