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Battery Charger and Checker Circuit for Real Time Clock

IP.com Disclosure Number: IPCOM000040936D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Riggio, SR: AUTHOR [+2]

Abstract

A technique is described whereby an electrical circuit, under microprocessor control, provides battery checking and charging capability. The circuit is unique in that the checking and charging capabilities are performed while the battery is supplying power to a real time clock, without affecting the accuracy of this clock.

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Battery Charger and Checker Circuit for Real Time Clock

A technique is described whereby an electrical circuit, under microprocessor control, provides battery checking and charging capability. The circuit is unique in that the checking and charging capabilities are performed while the battery is supplying power to a real time clock, without affecting the accuracy of this clock.

Computer operations often require telephone modems to turn a computer system on or off by means of an incoming telephone signal. When the power is off at the system, the battery and real time clock are used to provide power and control to the telephone sensing ciruitry, which enables system turn on. The circuit described herein allows the battery to be charged to required levels. Additionally, the circuit will check the condition of the battery, while the computer is turned on, for either an under or over voltage condition.

Battery 10, as shown in the figure, is connected to the current mode battery charger section of the circuit. The battery charging section of the circuit consists of transistor 11 and resistors 12, 13 and 15. Transistor 14 and resistor 16 are connected to a microprocessor so as to provide control of the charger circuit. The positive side of battery 10 is connected to the real time clock and to comparator circuits 17. Resistors 18, 19 and 20 provide the voltage divider network required to enable sensing of the over and under-voltage trip limits. If the battery voltage is...