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OVER VOLTAGE DETECTOR WITH STAND-BY MODE

IP.com Disclosure Number: IPCOM000012161D
Publication Date: 2003-Apr-14
Document File: 5 page(s) / 767K

Publishing Venue

The IP.com Prior Art Database

Abstract

Key words: battery life, leakage current, phone and charger

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OVER VOLTAGE DETECTOR WITH STAND-BY MODE

Key words: battery life, leakage current, phone and charger

In FIG. 1 is a schematic diagram including an AC/DC adapter for providing power to a phone when the phone is in a cradle.  The phone includes an over voltage detector OVIC, a battery (BATT+), and a phone processor section (PMU).

Problem

The over voltage protection integrated circuit (OVIC) is powered by an adapter or battery BATT+ coupled to an external bus called EXT.B+, which is further coupled to pin VCC of the OVIC, FIG. 1.  A gate of transistor Q1 is controlled by both an over voltage event at pin IN of the OVIC and a logic signal coupled to pin CNTRL.  When the phone is removed from the cradle, the battery BATT+ provides power for the phone.  However, when the phone is removed from the cradle, a leakage current ICC develops across Q1’s internal body diode from the battery BATT+ to the pin VCC of the OVIC.  This shortens the battery BATT+ life.

FIG. 2 includes a CCCV charger embodiment with transistor Q2 and the required electrical coupling from the EXT. B+ to pins VCC, ISNS and VSNS of the CCCV charger and pin OUT to a gate of transistor Q2.

The leakage problem presented above is aggravated by an additional leakage current ISS2 across transistor Q2’s internal body diode, because now there are two leakage currents ISS1 and ISS2.  This results in even a shorter battery BATT+ life.

Prior Art

Prior art resolves the current leakage problem by adding components in the cha...