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Advanced battery over-discharge protector for dynamic voltage transition

IP.com Disclosure Number: IPCOM000011905D
Original Publication Date: 2003-Mar-25
Included in the Prior Art Database: 2003-Mar-25
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Abstract

Disclosed is a circuit for a battery over-discharge-protector with voltage-detector in power supply circuit of Notebook PC. As a low voltage(2.5[V]) voltage-detector has to be used to integrate the over-discharge-protector inside the ASIC, the circuit is needed not to shut down the system when the AC adapter is pulled out from the Notebook PC(under the condition both an AC adapter and a battery are connected). The battery over-discharge-protector is necessary to prevent the battery from a decay caused by leaving in Notebook PC. The circuit has a comparator which has a hysteresis and a reset circuit for the hysteresis.

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Advanced battery over-discharge protector for dynamic voltage transition

A summary of this invention;
(1)As for the transition to plus direction, voltage which is bigger than the transition voltage width is applied to the comparator.
(2)As for the transition to minus direction, in contrast, voltage which is smaller enough than the transition voltage width is applied.
(3)When the battery is attached (this means the transition to plus direction), electric current goes through the small signal diode in forward direction. Thus, it is able to reset the comparator which has a hysteresis.
(4)If the AC adaptor is pulled out(this means the transition to minus direction) from the condition both AC adapter and the battery are attached, reverse-direction electric current will be blocked by the small signal diode. Thus, the reset voltage of the comparator's input terminal is almost zero.

Outcomes of this invention;
(1)Prevents the malfunction caused in pulling out the AC adaptor, keeps the over-discharge function even the voltage detector which has hysteresis are embedded in the ASIC.

The block diagram and wave form of input terminal voltage(AC adapter or the battery attached/detached) in the voltage-detector are shown.

It was inevitable to lower the voltage-detector's voltage to 2.5[V] to embed the voltage-detector inside the ASIC. Therefore, when the AC adapter is pulled out (minus direction transition) from the condition both the AC adapter and the battery are attached, the margin of the reset voltage which is applied to the voltage-detector becomes inadequate compared with the voltage fluctuation. Consequently, when the AC adapter is pulled out, the system shuts...