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Portable barcode label printer battery switching circuit

  • US 5,866,023 A
  • Filed: 07/03/1997
  • Issued: 02/02/1999
  • Est. Priority Date: 07/03/1997
  • Status: Expired due to Fees
First Claim
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1. In a portable barcode printer, an improved circuit for coupling power to a printer memory comprising:

  • a read/write memory storing information for controlling one or more operations of said barcode printer;

    a main battery coupled to said memory;

    a backup battery coupled to said memory;

    a circuit coupled between said main battery and said memory to provide power from said main battery to said memory under normal conditions and said circuit being coupled between said main battery and said back up battery, said circuit comprising;

    a P-channel field effect transistor having a gate, a source and a drain; and

    a N-channel field effect transistor having a source coupled to a ground, a gate and a drain;

    wherein the drain of said P-channel field effect transistor is coupled to the main battery, the source of the P-channel field effect transistor is coupled to the memory and the gate of the P-channel field effect transistor is connected to the drain of the N-channel field effect transistor so that when said N-channel field effect transistor is turned on said P-channel field effect transistor is turned on and saturated to allow a positive current flow from the drain to the source of said P-channel field effect transistor when said main battery is providing power to said memory.

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