Browse Prior Art Database

Software Controller Back-Up Battery Recharge

IP.com Disclosure Number: IPCOM000040014D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Sawdon, D: AUTHOR

Abstract

In equipment where a rechargeable battery backs up volatile memory or realtime clock when mains power is absent, the charge rate is selected by software when mains power returns. The charge-discharge history of the battery is stored so that the optimum charge rate may be selected, the user warned that the battery charge is low or that the battery should be replaced. Equipment which uses a rechargeable battery to back-up memory or realtime clock functions while the mains power is not present naturally requires that the battery is recharged during times when the mains power is present. Some market areas have unpredictable on/off power cycles; it is therefore difficult to guarantee that the battery will always be correctly recharged ...

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 2

Software Controller Back-Up Battery Recharge

In equipment where a rechargeable battery backs up volatile memory or realtime clock when mains power is absent, the charge rate is selected by software when mains power returns. The charge-discharge history of the battery is stored so that the optimum charge rate may be selected, the user warned that the battery charge is low or that the battery should be replaced. Equipment which uses a rechargeable battery to back-up memory or realtime clock functions while the mains power is not present naturally requires that the battery is recharged during times when the mains power is present. Some market areas have unpredictable on/off power cycles; it is therefore difficult to guarantee that the battery will always be correctly recharged ... voltage droop leads to unreliable memory retention and also frequency drift of realtime clock oscillators. The diagram shows a battery charging circuit whose switches are software controlled to select a suitable recharge current. The system makes use of the battery back-up memory to store a value which is proportional to the time which the battery has been discharging, for an appropriate charge rate can then be selected. In detail: The charge rate is made software-selectable (see

diagram); the number of different charge rates is

dependant on the battery technology chosen. The load current is determined during the development process. Two locations are reserved in battery back-up memory, A...