Battery charger

• US 6,225,789 B1
• Filed: 05/02/2000
• Issued: 05/01/2001
• Est. Priority Date: 05/05/1993
• Status: Expired due to Term

• Current Assignee: SGS Thomson Microelectronics Pte Ltd (STMicroelectronics NV)
• Original Assignee: SGS Thomson Microelectronics Pte Ltd (STMicroelectronics NV)
• Inventors: Yuen, Tang Kong
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): LUK, LAWRENCE W
• Application Number:
  US09/563,131
• Time in Patent Office: 364 Days
• Field of Search: 320/162, 320/137, 320/161, 320/131, 324/433, 340/455, 340/636
• US Class Current: 320/162
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

An end-of-charge detection technique for a battery charger is described. The technique involves the detection of a voltage drop at the end of charging and eliminates the effect of noise spikes.

Claims

1. A battery charger, comprising:

a voltage detector measuring a voltage of a battery being charged at a periodic interval;

a voltage charging gradient detector determining a voltage charging gradient from each measured voltage and a last preceding measured voltage;

a temperature detector measuring a temperature of the battery being charged at a periodic interval;

a temperature gradient detector determining a temperature gradient from each measured temperature and a last preceding measured temperature; and

a zero voltage gradient detector activated after at least one of the voltage charging gradient and the temperature gradient exceeds a respective threshold, the zero voltage gradient detector determining a completion of charge from a zero voltage charging gradient.

2. The battery charger of claim 1, further comprising:

a voltage drop detector activated after at least one of the voltage charging gradient and the temperature gradient exceeds the respective threshold, the voltage drop detector determining a completion of charge from a voltage drop exceeding a voltage drop threshold.

3. The battery charger of claim 2, wherein the battery charger switches to a trickle charge mode after the completion of charge is determined.

4. The battery charger of claim 2, wherein the zero voltage gradient detector determines the completion of charge from detecting a zero voltage charging gradient after at least one of the voltage charging gradient and the temperature gradient exceeds the respective threshold.

5. The battery charger of claim 2, wherein the voltage drop detector determines the completion of charge from detecting a voltage drop exceeding the voltage drop threshold after at least one of the voltage charging gradient and the temperature gradient exceeds the respective threshold.