Intelligent low battery detection circuit for a paging receiver

• US 5,696,437 A
• Filed: 08/18/1993
• Issued: 12/09/1997
• Est. Priority Date: 03/28/1990
• Status: Expired due to Fees

• Current Assignee: Mobile Knowledge, Inc.
• Original Assignee: Silcom Research Limited
• Inventors: Panther, Gyles, Williams, J. Peter
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/107,355
• Time in Patent Office: 1,574 Days
• Field of Search: 320/2, 320/30, 320/43, 320/44, 320/13, 320/39, 320/22, 320/23, 324/430
• US Class Current: 340/636.11
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/36 Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: H03D 7/16 Multiple-frequency-changing
• CPC Class Codes: H03D 7/161 all the frequency changers being connected in cascade
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H03D 7/166 using two or more quadrature frequency translation stages
• CPC Class Codes: H03D 7/18 Modifications of frequency-changers for eliminating image frequencies H03D7/16 takes precedence
• CPC Class Codes: H04B 1/1607 Supply circuits converters H02M; filters therefor H02M1/14; voltage stabilisers G05F1/46
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

A low battery condition is determined by sampling battery terminal voltage with a voltage comparator under light and heavy loading, and indicating a low battery condition when the rate of change of the sampled voltage or the rate of change of the internal resistance of the battery is greater than a predetermined limit.

Claims

1. A low battery detection circuit for electronic apparatus, comprising a voltage comparator for sampling battery terminal voltage respectively under light and heavy loading, and for indicating a low battery condition when at least one of a rate of change with respect to time of the sample voltage and a rate of change of the internal resistance with respect to time of the battery is greater than a predetermined limit.

2. A low battery detection circuit as defined in claim 1, in which the means for indicating the low battery condition is comprised of means for determining internal battery resistance and the derivative of the sampled voltage, and for indicating a low battery condition when said derivative exceeds a predetermined limit.

3. A low battery detection circuit as defined in claim 2, in which the voltage comparator has an input threshold voltage for establishing a lowest acceptable battery voltage condition reference, and including means for indicating that said condition has been traversed upon sampling of said battery terminal voltage.