Virtual Probing for Current Sense Resistor Parasitic Compensation
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Solution Overview
Problem
Current methods for measuring current in switch-mode power supplies using small series sense resistors are hindered by parasitic inductance, capacitance, and resistance, leading to inaccurate measurements, especially at higher frequencies, which can compromise the stability and power integrity of electronic circuits.
Innovation Solution
The implementation of virtual probing systems and methods that generate a virtual probe netlist to compensate for parasitic effects by removing unwanted parasitic components from the measurement circuit, allowing for accurate current waveform representation through a transfer function-based filtering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small series sense resistor is used to minimize power dissipation and voltage drop, then power loss and voltage drop are reduced, but parasitic inductance, capacitance, and resistance cause measurement inaccuracy
Solution Approach 1:
The system performs preliminary characterization of the sense resistor's parasitic parameters (inductance, capacitance, resistance) before actual current measurements. By pre-measuring and storing these parasitic values, the system can compensate for their effects during subsequent measurements, thereby maintaining measurement accuracy while using small sense resistors that minimize power loss.
Solution Approach 2:
The system uses feedback by continuously monitoring the voltage across the sense resistor and applying correction based on the characterized parasitic parameters. The measured voltage is processed through compensation algorithms that subtract the effects of parasitic inductance, capacitance, and resistance, providing accurate current measurements despite the presence of these unwanted elements in small-value sense resistors.
2Ease of operation
If a small series sense resistor is used to minimize voltage drop, then the effect on output is minimized, but parasitic effects cause poor measurements at higher frequencies
Solution Approach 1:
The system performs preliminary action by characterizing the frequency-dependent behavior of parasitic elements before actual measurements. The parasitic inductance, capacitance, and resistance values are measured and stored as compensation parameters, enabling the system to correct for frequency-related measurement errors while maintaining minimal output disturbance through small sense resistor values.
Solution Approach 2:
The system applies parameter changes by adjusting the measurement interpretation based on frequency. As frequency increases, the compensation algorithm dynamically adjusts for the increasing impact of parasitic inductance and capacitance, allowing accurate current measurements across a wide frequency range while maintaining small sense resistor values that minimize output disturbance.
3Measurement precision
If parasitic components are present in the sense resistor, then measurement accuracy deteriorates, but removing or reducing parasitics increases device complexity
Solution Approach 1:
The system applies self-service by having the measurement system characterize its own parasitic parameters. The same measurement apparatus used to measure current is used to measure the parasitic inductance, capacitance, and resistance of the sense resistor. This self-characterization approach eliminates the need for separate, complex parasitic extraction equipment, maintaining measurement accuracy while avoiding additional device complexity.
Solution Approach 2:
The system creates a computational model (copy) of the parasitic elements rather than physically removing them. By measuring the parasitic parameters and creating an equivalent circuit model, the system can simulate and compensate for parasitic effects through software algorithms, avoiding the need for complex physical modifications to the measurement circuitry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise current measurements by compensating for parasitic inductance, capacitance, and resistance, resulting in accurate current waveform representation and improved design, analysis, and debugging of electronic circuits.
Implementation Method 1
there is a voltage drop across the resistor of: V=I·R
Implementation Method 2
current flowing through a wire causes a magnetic field to develop that leads to inductance
Implementation Method 3
a wire has parasitics in the form of some resistance, and also generates an electric field between other wires and ground causing the wire to have some capacitance
Data Source
AI summary
Systems and methods are provided for compensating for parasitics in current measurements utilizing series current sense resistors. In one or more embodiments, the techniques include connecting a probe to a terminal of a circuit and a waveform measuring device. A waveform measuring device then acquires, through the probe, a voltage waveform. A virtual probe netlist is generated, where the netlist is descriptive of a series resistance and associated parasitics. A virtual probe processor converts, based on the virtual probe netlist, the voltage waveform to a current waveform representative of a current in the circuit.