Browse Prior Art Database

POWER SUPPLY IDENTIFICATION IN A 3 WIRE SYSTEM

IP.com Disclosure Number: IPCOM000009245D
Original Publication Date: 2002-Aug-13
Included in the Prior Art Database: 2002-Aug-13
Document File: 3 page(s) / 78K

Publishing Venue

Motorola

Related People

MARC B. RILEY: AUTHOR [+2]

Abstract

Intelligent charging systems benefit from properly utilizing the available energy from its power source. In some cases the system is compatible with several different power sources. In order to properly benefit from the capabilities of different power sources, the charging system must be able to recognize the type of power supply it is connected to. This could be done either mechanically or electrically. While there are some advantages of differentiating power supplies mechanically, the disadvantages far outweigh the advantages when dealing with intelligent charging systems that can accept multiple types of power supplies. Therefore, the effects of using an electrical identification in an intelligent charging system will be investigated. It is not uncommon to use a code resistor for power supply identification. In fact, prior art (US Patent 5,506,490) suggests this can be done using four wires: power supply voltage, power supply feedback, code resistor voltage, and ground. However, there is a potential issue when the intelligent charging system is also a host device for another intelligent charging system that utilizes the same power supply. This invention combines the code resistor and power supply feedback to achieve successful power supply identification using only three wires and also eliminates the issue with two intelligent charging systems utilizing the same power supply.

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  POWER SUPPLY IDENTIFICATION IN A 3 WIRE SYSTEM

AUTHORS

MARC B. RILEY

TANEKA FRAZIER

Problem

Intelligent charging systems benefit from properly utilizing the available energy from its power source.  In some cases the system is compatible with several different power sources.  In order to properly benefit from the capabilities of different power sources, the charging system must be able to recognize the type of power supply it is connected to.  This could be done either mechanically or electrically.  While there are some advantages of differentiating power supplies mechanically, the disadvantages far outweigh the advantages when dealing with intelligent charging systems that can accept multiple types of power supplies.  Therefore, the effects of using an electrical identification in an intelligent charging system will be investigated. It is not uncommon to use a code resistor for power supply identification.  In fact, prior art (US Patent 5,506,490) suggests this can be done using four wires: power supply voltage, power supply feedback, code resistor voltage, and ground.  However, there is a potential issue when the intelligent charging system is also a host device for another intelligent charging system that utilizes the same power supply.  This invention combines the code resistor and power supply feedback to achieve successful power supply identification using only three wires and also eliminates the issue with two intelligent charging systems utilizing the same power

supply.

Solution

This invention will provide a method and apparatus for determining an external power supply type and modifying the charging of a spare battery based on the external power supply type and battery information.  A micro-controller in the desktop charger regulates the charging current to the battery.  The micro-controller contains an A/D converter that is connected to a pull-up resistor (R1) internal to the desktop charger (Unit 1), and to a pull-down resistor (Rid) in the external power supply adapter.  The voltage generated by the resistor divider...