Battery remaining amount warning circuit

• US 6,922,151 B2
• Filed: 07/11/2003
• Issued: 07/26/2005
• Est. Priority Date: 07/11/2002
• Status: Expired due to Fees

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Kawakami, Chikuni
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): TANG, SON M
• Application Number:
  US10/617,047
• Publication Number:
  US 20040008117A1
• Time in Patent Office: 746 Days
• Field of Search: 3406361-63615, 340/636.19, 340657-664, 320149-152, 323274-277
• US Class Current: 340/636.1
• CPC Class Codes: G01R 31/386 using test-loads

Abstract

The battery remaining amount warning circuit can issue a battery remaining amount warning after battery power is fully used, reduce current consumption, and issue a warning at appropriate timing for various types of battery. A system controller calculates DC resistance value of the battery from a difference between a current value in an operating mode before a change which is stored in the memory and a current value in an operating mode after the change which is stored in the memory and a voltage variation of the battery measured by an A/D converter, and when the calculated DC resistance value becomes greater than a predetermined value, the system controller sends a warning instruction signal to a data LCD.

Claims

1. A battery remaining amount warning circuit that detects a voltage drop of a battery in an electronic device, comprising:

a storage device which stores a current value in each of a plurality of operating modes of the electronic device;

a measuring device which measures a voltage variation of the battery when a first one of the operating modes of the electronic device is changed for a second one of the operating modes of the electronic device;

a calculation device which calculates a DC resistance value of the battery from the voltage variation measured by the measuring device and a difference between the current value in the first operating mode stored in the storage device and the current value in the second operating mode stored in the storage device; and

a warning device which gives a warning when the DC resistance value calculated by the calculation device becomes greater than a predetermined warning level.

2. The battery remaining amount warning circuit according to claim 1, wherein the electronic device is a digital camera and the plurality of operating modes include a playback mode, recording mode, flash charge recording mode, of the digital camera.