System and method for current measurement in the presence of high common mode voltages

A method for measuring an electrical current flowing in a load comprising:

• providing a measurement resistor, said resistor having a first connecting terminal and a second connecting terminal, said load being electrically coupled to said second connecting terminal of said measurement resistor, said electrical current flowing through said measurement resistor;
• providing a first network resistor, said first network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said first network resistor being electrically coupled to said first connecting terminal of said measurement resistor;
• providing a second network resistor, said second network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said second network resistor being electrically coupled to said second connecting terminal of said measurement resistor;
• providing a third network resistor, said third network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said third network resistor being electrically coupled to said second connecting terminal of said first network resistor;
• providing a fourth network resistor, said fourth network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said fourth network resistor being electrically coupled to said second connecting terminal of said second network resistor, said second connecting terminal of said fourth network resistor being electrically coupled to said second connecting terminal of said third network resistor;
• providing a first amplifier, said first amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, said non-inverting input terminal of said first amplifier being electrically coupled to said second connecting terminal of said first network resistor, said inverting input terminal of said first amplifier being electrically coupled to said second connecting terminal of said second network resistor;
• providing a DC reference voltage;
• providing a second amplifier, said second amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, said non-inverting input of said second amplifier being electrically coupled to said DC reference voltage, said inverting input of said second amplifier being electrically coupled to said second connecting terminal of said second network resistor, said output of said second amplifier being electrically coupled to said second connecting terminal of said fourth network resistor;
• measuring an output voltage from said output terminal of said first amplifier;
• providing a third amplifier, said third amplifier having a variable gain, said third amplifier having a first input terminal, a second input terminal, and an output terminal, said first input terminal of said third amplifier being electrically coupled to said first connecting terminal of said second network resistor, said second input terminal of said third amplifier being electrically coupled to said second connecting terminals of said third and said fourth network resistors;
• generating an error correction voltage at said output of said third amplifier by adjusting said variable gain of said third amplifier;
• and
• adding said error correction voltage to said output voltage of said first amplifier.