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Charging efficiency using selectable isolation

  • US 8,810,208 B2
  • Filed: 03/10/2011
  • Issued: 08/19/2014
  • Est. Priority Date: 03/10/2011
  • Status: Active Grant
First Claim
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1. An apparatus for charging an energy storage system (ESS) from an AC line voltage, comprising:

  • a boost stage for converting the AC line voltage to a first ESS charging voltage;

    an isolation stage, coupled to the boost stage, for converting the first ESS charging voltage to a second ESS charging voltage with the second ESS charging voltage less than the first ESS charging voltage, the isolation stage removing a common mode current between the ESS and the boost stage;

    a switching system, responsive to a control signal, to set a direct communication of the first ESS charging voltage to the ESS in a bypass mode and to open the direct communication of the first ESS charging voltage to the ESS in an isolation mode; and

    a controller, coupled to the switching system, for setting the modes responsive to a battery voltage, a peak of the AC line voltage, and a total leakage current at an input of the AC line voltage, the controller asserting the control signal to the switching system;

    wherein a residual-current device (RCD) trip level is associated with a source for the AC input voltage and wherein the controller asserts the control signal to set the bypass mode when both the battery voltage is above the peak of the AC line and the leakage current is below the RCD trip level.

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