Current Sensing DCR Calibration With Parasitic Resistance Compensation
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Solution Overview
Problem
Current current sensing techniques in power conversion systems face errors due to varying DC resistance and parasitic resistances in inductors and printed circuit boards, which can lead to improper voltage supply and reliability issues in computing systems.
Innovation Solution
A method and device for measuring and calibrating power conversion circuits by deriving a pre-calibration voltage across a capacitive device, setting switching elements to allow a fixed current flow, measuring and calibrating voltage across a resistance element, and storing the calibrated voltage for use during operation, with temperature compensation for accurate resistance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC resistance measurement is performed during manufacture, then baseline DCR is obtained, but measurement accuracy is insufficient due to manufacturing variations and parasitic resistances
Solution Approach 1:
The patent performs calibration measurements during the manufacturing process to establish baseline resistance values before the product is deployed. This preliminary action captures the actual resistance characteristics of each specific circuit board, including its unique parasitic resistances, so that accurate current sensing can be achieved during operation without requiring complex real-time compensation circuits.
Solution Approach 2:
The patent uses measured resistance values from calibration to create lookup tables or calibration data that are stored in the device. During operation, the system uses these stored calibration values to compensate for parasitic resistances and manufacturing variations, effectively using feedback from the manufacturing measurement process to improve operational accuracy.
2Productivity
If sample circuit boards are measured during manufacture, then baseline data is collected, but measurement variation is high due to PCB resistance variations and solder connections
Solution Approach 1:
The patent extracts and measures only the specific resistance components that are relevant to current sensing accuracy during the manufacturing process. By focusing measurement on the critical parasitic resistance elements rather than attempting to measure all possible resistance sources, the system achieves both manufacturing efficiency and improved measurement consistency.
Solution Approach 2:
The patent changes the measurement parameters and conditions during calibration to account for temperature variations and other environmental factors that affect resistance. By performing measurements under controlled and documented conditions, the system captures resistance values that are representative of actual operating conditions, reducing variation between samples.
3Measurement precision
If temperature compensation is implemented, then accurate resistance measurement is achieved, but device complexity increases
Solution Approach 1:
The patent introduces temperature sensors as intermediary devices that measure the thermal state of the circuit board and inductor. These temperature measurements serve as mediators that allow the system to compensate for temperature-induced resistance changes through software or lookup tables, avoiding the need for complex hardware compensation circuits while still achieving accurate resistance measurement.
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 provides accurate current sensing by accounting for parasitic resistances, ensuring reliable voltage supply and improving system efficiency by calibrating errors and compensating for temperature variations.
Implementation Method 1
a capacitive device coupled between the input and output power nodes
Implementation Method 2
measuring a voltage across a resistance element of the calibration circuit
Implementation Method 3
setting a pair of switching elements of a calibration circuit tied to the output power node to permit a fixed known current to flow through the pair of switching elements
Data Source
AI summary
The present invention pertains to calibration in current sensing applications. Power conversion systems such as those used in computer architectures may employ step down converters such as buck converters or other types of converters. The present invention provides calibration processes and devices to account for various parasitic resistances which are found in such systems. A calibration circuit may be coupled to the buck converter or other power conversion to determine a calibrated voltage signal for the output of the power converter. An effective DC resistance may be determined and programmed for use by a control device used. In this way, the parasitic resistances are taken into account to obtain an accurate estimate of the actual current. In turn, this enables power converters and other devices to operate within specification requirements.