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Level shift circuit

  • US 6,501,321 B2
  • Filed: 10/05/2001
  • Issued: 12/31/2002
  • Est. Priority Date: 03/02/1999
  • Status: Expired due to Term
First Claim
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1. A level shift circuit comprising:

  • at least one controllable semiconductor device including an electrode acting as a potential reference and connected to a common potential, the potential reference electrode and a main electrode being electrically connected together while a conduction signal is being input between the potential reference electrode and a control electrode;

    a DC power supply having one electrode connected to an external circuit at its predetermined site varying between the common potential and a predetermined high potential, the DC power supply having a voltage lower than a voltage between said two potentials;

    at least one load resistor having one end connected to the other electrode of the DC power supply and having the other end connected to the main electrode of said controllable semiconductor device; and

    a logic circuit operating under said DC power supply, wherein a pulse-like conduction signal is input to the control electrode of said controllable semiconductor device so that conduction through the controllable semiconductor device causes a pulse-like voltage drop in the load resistor, the voltage drop being then communicated to said logic circuit as a signal, and wherein a current negative feedback resistor is inserted between the potential reference electrode of the controllable semiconductor device and the common potential so that the voltage between the control electrode and the common potential has a predetermined value smaller than the voltage value of said DC power supply while each controllable semiconductor device is conductive.

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