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# Fuel Gauge Sampling Frequency Control by Battery Current

IP.com Disclosure Number: IPCOM000116911D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 42K

IBM

## Related People

Narita, I: AUTHOR

## Abstract

Disclosed is a battery fuel gauge circuit which changes its sampling frequency by battery current. If the sampling frequency gets faster, the accuracy of the fuel gauge becomes better, but on the other hand the power consumption of the fuel gauge IC becomes bigger. If the sampling frequency becomes lower, the power consumption of the fuel gauge IC becomes rude. The power consumption of the notebook PC becomes big and varies dynamically in the normal operation mode. In suspend mode, the power consumption becomes smaller and rather static.

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Fuel Gauge Sampling Frequency Control by

Battery

Current

Disclosed is a battery fuel gauge circuit which changes its
sampling frequency by battery current.  If the sampling frequency
gets faster, the accuracy of the fuel gauge becomes better, but on
the other hand the power consumption of the fuel gauge IC becomes
bigger.  If the sampling frequency becomes lower, the power
consumption of the fuel gauge IC becomes rude.  The power consumption
of the notebook PC becomes big and varies dynamically in the normal
operation mode.  In suspend mode, the power consumption becomes
smaller and rather static.

In this invention, the sampling frequency becomes low when the
battery current becomes small.  The frequency becomes high when the
battery current becomes big.  Therefore, the accuracy and the power
consumption of the fuel gauge will be optimized.

The Figure shows the circuit that implements this invention.
The battery current I is monitored by the resistor R and OP Amp.  The
signal generated by the OP Amp is inputted to the clock selector.
The clock selector selects either clock1 or clock2 according to the
battery current, and outputs the selected clock signal to the fuel
gauge.  Provided that the threshold value of the current is 0.1A,
clock1 is 3 kHz and clock2 is 300 kHz.  In this case, the fuel gauge
will be operated with 3 kHz if the battery current is below 0.1 A and
will be operated 300 kHz if the battery current is above 0.1 A.
Con...