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SINGLE POWER SOURCE TRANSFORMATION DISTRIBUTION FOR A BATTERY CHARGER

IP.com Disclosure Number: IPCOM000007342D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-18
Document File: 3 page(s) / 98K

Publishing Venue

Motorola

Related People

Scott Garrett: AUTHOR [+4]

Abstract

Minimizing cost and improving quality perform- ance are among the goals of any Charger Design. Today's battery charger power supplies typically have an isolated auxiliary transformer to supply power for the controller circuitry as in figure 1. This method adds cost and complexity By using a single trans- former to supply both the battery charge power and the controller power, the isolated auxiliary trans- former is unnecessary. This can be done without jeopardizing the per%ormance of the battery charger. Thereby reducing the cost of the power supply is minimized and reducing the number ofparts.

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MO-LA Technical Developments Volume 24 March 1995

SINGLE POWER SOURCE TRANSFORMATION DISTRIBUTION FOR A BATTERY CHARGER

by Scott Garrett, Jose Fernandez, Vernon Meadows and Lam Dao

  Minimizing cost and improving quality perform- ance are among the goals of any Charger Design. Today's battery charger power supplies typically have an isolated auxiliary transformer to supply power for the controller circuitry as in figure 1. This method adds cost and complexity By using a single trans- former to supply both the battery charge power and the controller power, the isolated auxiliary trans- former is unnecessary. This can be done without jeopardizing the per%ormance of the battery charger. Thereby reducing the cost of the power supply is minimized and reducing the number ofparts.

Referring to Figure 2, the transformer, L2, is used

to provide power for both the controller circuitry and charging current. This is accomplished in the following manner. First, the charger's power supply output will start up at a predetermined voltage, for example 12Vdc. While the unit is in standby (12Vdc), the controller is powered via a step down converter, U3, (Wdc). Once the battery is detected (typically via RT line). The micro controller processor will monitor the battery voltage. Ifthe battery voltage is

above the charger controller voltage regulator's spec- ification (typically 1.7Vdc above Wdc), the micro controller processor will close the MOSFET switch M2 or M3 and provide current to...