Power management system for battery powered computers

• US 5,254,928 A
• Filed: 10/01/1991
• Issued: 10/19/1993
• Est. Priority Date: 10/01/1991
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Wallgren, Markus, Young, Steven J.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US07/770,193
• Time in Patent Office: 749 Days
• Field of Search: 320/14, 320/44, 320/39, 320/21, 307/66
• US Class Current: 320/125
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: Y10S 320/13 Fault detection

Abstract

A power management system for a portable computer is disclosed. The system can determine which one of a plurality of battery packs has been coupled to the system. After determining the type of battery pack, the system recalls from storage the recommended charging pattern for the particular battery pack and begins to charge the battery at the recommended rate. The system'"'"'s information is used during charging to determine if the battery pack is defective. When the computer is running off the battery pack, the charge counter measures the total amount of charge supplied to the computer and provides this information to the system. When the difference betweem the total amount of charge supplied to the computer and the total charge available from the battery reaches a predefined limit, the system indicates to the computer that a low-power situation exists and that the computer should prepare for a possible loss-of-power event.

Claims

1. A battery charging circuit with self-adjusting charging voltage levels, the circuit comprising:

first transformer means for converting an A.C. voltage to a D.C. voltage;

oscillator means coupled to the first transformer means for converting the D.C. voltage to a square wave of fixed amplitude but variable duty cycle;

second transformer means coupled to the oscillator means for converting the square wave to a sinusoidal wave, the amplitude of the sinusoidal wave varying directly with the duty cycle of the square voltage wave;

rectifier means coupled to the second transformer means and a battery, for converting the sinusoidal wave to a D.C. charging voltage; and

voltage comparator means having at least two inputs, a first input being coupled to an output of the rectifier means, a second input being coupled to a square wave generator, the output of the comparator means being coupled to the oscillator means, the comparator means decreasing the duty cycle of the oscillator means when the output of the comparator is high, the decrease in the duty cycle resulting in less voltage at the output of the second transformer means.

2. A power management system for a computer, the computer being powered by one of a plurality of battery packs, the system comprising:

power charging means coupled to the battery pack and an A.C. power supply for charging the battery pack, the power charging means further comprising a means for supplying a self-adjusting voltage charge level to the computer, the means comprising;

first transformer means for converting an A.C. voltage to a D.C. voltage;

oscillator means coupled to the first transformer means for converting the D.C. voltage to a square wave of fixed amplitude with a variable duty cycle;

second transformer means coupled to the oscillator means for converting the square wave to a sinusoidal wave, the amplitude of the sinusoidal wave varying directly with the duty cycle of the square voltage wave;

rectifier means coupled to the second transformer means and the battery pack, for converting the sinusoidal wave to a D.C. charging voltage; and

voltage comparator means having a least two inputs, a first input being coupled to the output of the rectifier means and the second input being set a predefined D.C. voltage level, the output of the comparator means being coupled to the oscillator means, the comparator means decreasing the duty cycle of the oscillator means when the output of the comparator is high, the decrease in duty cycle resulting in less voltage at the output of the second transformer means;

controller means coupled to the power charging means and the computer, the controller means having a memory means for storing battery type and charging rate information, the controller means receiving battery type information from the battery pack through the power charging means and supplying charging rate information to the power charging means; and

charge measuring means coupled to the battery pack, the computer, the power charging means and the controller means, the charge counter means measuring the amount of charge that has flowed into the computer, the discharge information being provided to the controller means for generating a low-power warning when the discharge amount reaches a predefined limit.