Auto-measurement and calibration of DC resistance in current sensing applications

A measurement and calibration device for use with a power conversion device including an input power node, an output power node and a capacitive device tied to the input and output power nodes, the measurement and calibration device comprising:

• a resistance element tied at a first side thereof to the output power node;
• a first switching element having a first connection tied to a second side of the resistance element, a second connection tied to a controller for managing the power conversion device and a third connection tied to a current limiting resistor;
• and
• a second switching element having a first connection tied to the current limiting resistor, and a second connection tied to the controller;
• wherein upon application of a fixed current across the current limiting resistor, the measurement and calibration device:
• obtains a voltage differential across the capacitive device to derive a pre-calibration voltage;
• sets the first and second switching elements to permit a fixed current to flow through the pair of switching elements;
• measures a voltage across the resistance element of the calibration circuit;
• calibrates any errors associated with the power conversion device based on the measured voltage across the resistance element;
• re-measures the voltage differential across the capacitive device after calibrating for any errors to derive a calibration voltage;
• derives a calibrated voltage from the calibration voltage and the pre-calibration voltage;
• and
• stores the calibrated voltage in memory for use during operation of the power conversion circuit.

A measurement and calibration architecture for use with a power conversion device including an input power node, an output power node and a capacitive device tied to the input and output power nodes, the measurement and calibration architecture comprising:

• a controller for managing operation of the power conversion device;
• a resistance element tied at a first side thereof to the output power node;
• a first switching element having a first connection tied to a second side of the resistance element, a second connection tied to the controller and a third connection tied to a ground node;
• a second switching element having a first connection tied to the ground node and a second connection tied to the controller;
• wherein the controller is operable to apply a fixed current across the capacitive device of the power conversion device, to obtain a voltage differential across the capacitive device to derive a pre-calibration voltage, to set the first and second switching elements to permit a fixed current to flow through the pair of switching elements, to measure a voltage across the resistance element, to calibrate any errors associated with the power conversion device based on the measured voltage across the resistance element, to re-measure the voltage differential across the capacitive device after calibrating for any errors to derive a calibration voltage, to derive a calibrated voltage from the calibration voltage and the pre-calibration voltage, and to store the calibrated voltage in memory for use during operation of the power conversion circuit.

A method of measuring and calibrating resistance in an electronic circuit board having an input node and an output node, the method comprising:

• measuring a voltage between the input and output nodes to derive a first baseline voltage VRpcb—before—cal;
• measuring a voltage across a calibration resistor R—PCB—CAL to derive a second baseline voltage VRcal—before—cal, the calibration resistor being tied at a first end thereof to a switching element and to a second end thereof to ground;
• activating the switching element so that the first end of the calibration resistor is electrically connected to the output node;
• upon activation of the switching element, re-measuring the voltage between the input and output nodes to derive a first calibration voltage V—Rpcb—cal;
• upon activation of the switching element, re-measuring the voltage across the calibration resistor to derive a second calibration voltage VRcal—cal;
• determining a calibration current I—cal according to the equation:
• I—cal=(V—Rcal—cal−V—Rcal—before—cal)/R—PCB—CAL;
• determining an effective resistance R—pcb of a portion of the electronic circuit board between the input and output nodes according to the equation:
• R—pcb=(VRpcb—cal−VRpcb—before—cal)/I—cal;
• and
• storing the effective resistance R—pcb in memory.

A measurement and calibration device for use with an electronic circuit board having an input node and an output node, the measurement and calibration device comprising:

• a controller for managing operation of the calibration device;
• a switching element having a first connection electrically connected to the output node;
• and
• a calibration resistor tied at a first side thereof to the output power node through the switching element and tied at a second side thereof to ground;
• wherein the controller is operable to:
• measure a voltage between the input and output nodes to derive a first baseline voltage VRpcb—before—cal;
• measure a voltage across the calibration resistor to derive a second baseline voltage V—Rcal—before—cal;
• activate the switching element so that the first side of the calibration resistor is electrically connected to the output node;
• upon activation of the switching element, re-measure the voltage between the input and output nodes to derive a first calibration voltage V—Rpcb—cal;
• upon activation of the switching element, re-measure the voltage across the calibration resistor to derive a second calibration voltage VRcal—cal;
• determine a calibration current I—cal according to the equation:
• I—cal=(VRcal—cal−VRcal—before—cal)/R—PCB—CAL,
• wherein R—PCB—CAL represents a known resistance of the calibration resistor;
• determine an effective resistance R—pcb of a portion of the electronic circuit board between the input and output nodes according to the equation:
• R—pcb=(VRpcb—cal−VRpcb—before—cal)/I—cal;
• and
• store the effective resistance R—pcb in memory.