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Dual voltage electrical system

  • US 4,748,395 A
  • Filed: 08/07/1987
  • Issued: 05/31/1988
  • Est. Priority Date: 08/07/1987
  • Status: Expired due to Fees
First Claim
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1. A dual voltage motor vehicle electrical system comprising, an alternating current generator having a polyphase output winding, a polyphase full-wave bridge rectifier comprised of groups of positive and negative diodes, said bridge rectifier having AC input terminals connected to said output winding and having positive and negative direct voltage output terminals, first and second storage batteries connected in series and across said direct voltage output terminals of said bridge rectifier, the negative terminal of one battery and the positive terminal of the other battery being connected to a common junction, a first switchable rectifying circuit connected between said junction and said AC input terminals, said first switchable rectifying circuit when biased conductive and one of said groups of diodes supplying charging current to one of said batteries, a second switchable rectifying circuit connected between said junction and said AC input terminals, said second switchable rectifying circuit when biased conductive and the other group of said diodes supplying charging current to the other battery, means for causing said switchable rectifying circuits to be biased alternately conductive, means for sensing the relative magnitudes of the voltages across said batteries, means responsive to the difference in the voltages across the batteries for controlling the time periods that said switchable rectifying circuits are biased conductive, said last-named means operative to cause the switchable rectifying circuit that supplies current to the battery that has the lower voltage to be biased conductive for a time period that is longer than the time period of conduction of the other switchable rectifying circuit means for summing the phase voltages developed by said polyphase output winding to provide a control signal that is a function of the summed phase voltages, and means responsive to said control signal for preventing simultaneous conduction of said switchable rectifying circuits.

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