Current sensing system and method

Abstract

There is provided a current sense circuit ( 134 ). An exemplary current sense circuit ( 134 ) comprises a voltage-to-current converter circuit ( 218 ) that is adapted to receive a voltage that is proportional to a load current drawn from a battery ( 110 ) by a load ( 202 ) and to produce a current proportional to the load current, and a current-to-voltage converter circuit ( 228 ) that is adapted to receive the current proportional to the load current and to produce a voltage proportional to the load. current based on a regulated voltage source ( 230 ).

What is claimed is: 
     
         1 . A current sense circuit comprising:
 a voltage-to-current converter circuit that is adapted to receive a voltage that is proportional to a load current through a load and to produce a current proportional to the load current; and   a current-to-voltage converter circuit that is adapted to receive the current proportional to the load current and to produce a voltage proportional to the load current.   
     
     
         2 . The current sense circuit recited in  claim 1 , comprising a current sense resistor having a voltage drop that is applied differentially to the voltage-to-current converter circuit. 
     
     
         3 . The current sense circuit recited in  claim 1 , comprising an analog-to-digital converter that is adapted to produce a digital output corresponding to the voltage proportional to the load current. 
     
     
         4 . The current sense circuit recited in  claim 1 , wherein the current-to-voltage converter circuit is adapted to produce an output voltage that falls as the current proportional to the load current increases. 
     
     
         5 . The current sense circuit recited in  claim 1 , wherein the load comprises an active antenna. 
     
     
         6 . The currant sense circuit recited in  claim 1 , wherein the current sense circuit comprises a portion of a vehicle audio subsystem. 
     
     
         7 . The current sense circuit recited in  claim 1 , wherein the voltage-to-current converter circuit comprises a single Junction Field Effect Transistor (JFET) transistor that solely produces the current proportional to the load current. 
     
     
         8 . The current sense circuit recited in  claim 1 , wherein the current-to-voltage converter circuit is adapted to receive the current proportional to the load current and to produce a voltage proportional to the load current based on a regulated voltage source. 
     
     
         9 . A method of sensing current drawn by a load, the method comprising:
 receiving a voltage that is proportional to a load current drawn by a load;   producing a current proportional to the load current;   receiving the current proportional to the load current; and   producing a voltage proportional to the load current.   
     
     
         10 . The method recited in  claim 9 , wherein the current proportional to the load current is produced based on a regulated voltage source. 
     
     
         11 . The method recited in  claim 9 , wherein the current proportional to the load current is produced by a junction Field Effect Transistor (JFET). 
     
     
         12 . The method recited in  claim 9 , comprising differentially applying a voltage drop to produce the current proportional to the load current. 
     
     
         13 . The method recited in  claim 9 , comprising producing a digital output corresponding to the voltage proportional to the load current. 
     
     
         14 . The method recited in  claim 9 , comprising causing the voltage proportional to the load current to fall in response to a rise in the current proportional to the load current. 
     
     
         15 . A motorized vehicle, comprising:
 a chassis;   an engine that is supported by the chassis;   a power train adapted to be driven by the engine;   control electronics that are adapted to control the engine and the power train; and   an entertainment system that includes an audio subsystem, the audio subsystem being adapted to provide audio programming to occupants of the motorized vehicle, the audio subsystem having a current sense circuit, the current sense circuit comprising:
 a voltage-to-current converter circuit that is adapted to receive a voltage that is proportional to a load current drawn from a battery by a load and to produce a current proportional to the load current; and 
 a current-to-voltage converter circuit that is adapted to receive the current proportional to the load current and to produce a voltage proportional to the load current. 
   
     
     
         16 . The motorized vehicle recited in  claim 15 , wherein the voltage-to-current converter circuit comprises a JFET that produces the current proportional to the load current drawn from the battery. 
     
     
         17 . The motorized vehicle recited in  claim 15 , comprising a current sense resistor having a voltage drop that is applied differentially to the voltage-to-current converter circuit. 
     
     
         18 . The motorized vehicle recited in  claim 15 , comprising an analog-to-digital converter that is adapted to produce a digital output corresponding to the voltage proportional to the load current. 
     
     
         19 . The motorized vehicle recited in  claim 15 , wherein the current-to-voltage converter circuit is adapted to:
 produce an output voltage that falls as the current proportional to the load current increases; and   produce a voltage proportional to the load current based on a regulated voltage source.   
     
     
         20 . The motorized vehicle recited in  claim 15 , wherein the load comprises an active antenna.