Interface Circuit, Power Conversion Device, and Vehicle-Mounted Electric Machinery System

Abstract

An interface circuit capable of reliably transmitting signal even when there is fluctuation in the potential difference in reference potentials between circuits between which signal transmission is carried out. An interface circuit 4 is comprised of a level shift circuit 20 and a potential selection circuit 10 for selecting the potential of a power supply voltage for operating the level shift circuit 20 . The potential selection circuit 10 selects one of a plurality of input potentials. The level shift circuit 20 receives a voltage pulse having a first potential as reference potential and outputs a voltage pulse having a second potential as reference potential. The level shift circuit 20 is operated on the basis of both a potential difference between the output potential from the potential selection circuit and the first potential and a potential difference between the selected potential and the second potential.

1 . An interface circuit for transmitting a signal having a first potential as reference potential into a signal having a second potential as reference potential, wherein a plurality of potentials are applied as operating power supplies, said interface circuit being operated on the basis of a potential difference between one selected potential among said plurality of potentials and said first potential, and a potential difference between said selected potential and said second potential. 
   
   
       2 . An interface circuit comprising:
 a signal transmission circuit; and   an automatic potential selection circuit for selecting a potential of an operating power supply voltage for said signal transmission circuit,   wherein a plurality of different potentials are applied to said potential selection circuit, which selects one therefrom,   wherein a first potential, a second potential, and said selected potential are applied to said signal transmission circuit, which is operated on the basis of both a potential difference between said selected potential and said first potential and a potential difference between said selected potential and said second potential, and   wherein a signal having said first potential as reference is converted into a signal having said second potential as reference to be transmitted.   
   
   
       3 . The interface circuit according to  claim 2 , wherein said first potential and said second potential are connected by a wire conductor. 
   
   
       4 . The interface circuit according to  claim 2 , wherein said potential selection circuit and said signal transmission circuit are each comprised of a semiconductor integrated circuit. 
   
   
       5 . The interface circuit according to  claim 2 , wherein said signal transmission circuit is a level shift circuit to which a signal having a first potential as reference potential is applied and which outputs a signal having a second potential as reference potential,
 wherein said interface circuit is operated on the basis of both a potential difference between said selected potential and said first potential, and a potential difference between said selected potential and said second potential.   
   
   
       6 . The interface circuit according to  claim 2 , wherein said potential selection circuit selects one of said plurality of potentials that has a greater potential difference from said first potential. 
   
   
       7 . An interface circuit comprising:
 a signal transmission circuit; and   a potential selection circuit for selecting a potential for the operating power supply voltage for said signal transmission circuit,   wherein a plurality of different potentials are applied to said potential selection circuit, which selects one of said plurality of potentials in response to a switch instruction signal,   wherein a first potential, a second potential, and said selected potential are applied to said signal transmission circuit, which is operated on the basis of both a potential difference between said selected potential and said first potential and a potential difference between said selected potential and said second potential,   wherein a signal having said first potential as reference potential is converted into a signal having said second potential as reference to be transmitted.