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IMPROVED VEHICLE OPERATED AUXILIARY LEAD-ACID BATTERY CHARGER

IP.com Disclosure Number: IPCOM000005799D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2001-Nov-07
Document File: 1 page(s) / 52K

Publishing Venue

Motorola

Related People

Dave Bush: AUTHOR [+2]

Abstract

In certain mobile applications, it is desirable to have radio equipment operated from a lead-acid battery other than the vehicle battery. For these applications, a charging system must be provided to keep the system battery charged at all times. The use of passive isolation diodes is possible, but installation in many vehicles is inconvenient. An active self-contained battery charger is an effective solution.

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MOTOROLA Technical Developments Volume 9 August 1989

IMPROVED VEHICLE OPERATED AUXILIARY LEAD-ACID BATTERY CHARGER

by Dave Bush and Bill Downs

   In certain mobile applications, it is desirable to have radio equipment operated from a lead-acid battery other than the vehicle battery. For these applications, a charging system must be provided to keep the system battery charged at all times. The use of passive isolation diodes is possible, but installation in many vehicles is inconvenient. An active self-contained battery charger is an effective solution.

   The system battery charger must be capable of providing a sufficient temperature-compensated output, independent of input supply variations. This requires simultaneous implementation of both step-up and step- down circuitry. In typical pulsed circuit applications the component power dissipation requirements are sub- stantial. These component dissipations can be reduced by incorporating a linear regulator with an integrated step-up supply. A block diagram of the charger is shown.

   The vehicle input supplies power to the linear regulator (which maintains an input to Ll, D2) and boost regulator at or below the battery charger output level. During high input voltage conditions, the linear regulator provides aconstant controlled voltage source to the boost regulator. During low input conditions, the regulator saturates and the boost regulator provides the increased output required. A temperature compensation circuit is...