CURRENT SENSE CIRCUIT WITH OFFSET CALIBRATION

摘要

A switching device is controlled by a microprocessor to selectively configure the circuit between a current measurement mode and a calibration mode. When the switch is set to the “on” state, the circuit acts as a normal prior art circuit, with the output Vout being read by the microprocessor to determine the current to the load. However, when the switch is set to the “off” state, a small value resistor (which may be roughly three orders of magnitude greater than Rshunt) connects the inputs of the measuring circuit so that the circuit can generate an output Vout corresponding to the zero load current. By connecting the V+ and V− inputs together with a low resistance resistor, the no-load condition Vdiff=V+−V−≈0 applies. In this state, the no-load offset can be determined by measuring the output voltage of the circuit without turning off the load.

主权项

1. A system for determining the no-load offset of a circuit comprising:
a shunt resistor with an input and an output, wherein the input of the shunt resistor also leads to one input of an amplifier and the output of the shunt resistor also leads to a second input of the amplifier; a switch controlled by a microcontroller, a first side of said switch being connected to one of the input and output of the shunt resistor; a small value resistor, a first end of the small value resistor being connected to the other of the input and output of the shunt resistor, and a second end of the small value resistor being connected to a second side of the switch; wherein the switch is actuated by the microcontroller to selectively break the connection between its side of the shunt resistor and the respective input of the amplifier such that the other side of the shunt resistor leads to one input of the amplifier as normal, and also leads to the other input of the amplifier through the small value resistor.