Dual-Shunt Current Measurement Circuit for Wide Dynamic Range
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Solution Overview
Problem
Existing Source and Measure Units (SMUs) struggle to measure current consumption across a wide dynamic range without changing the shunt resistor, especially when dealing with active loads that experience rapid current fluctuations, and they suffer from poor signal-to-noise ratios when measuring low currents.
Innovation Solution
A device using shunt resistors with different resistive values and differential amplifiers, coupled with analog-to-digital converters, selectively activates additional amplifiers to maintain measurement accuracy across varying current levels, and employs control loops to stabilize voltage during rapid transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single shunt resistor is used for current measurement, then the device structure is simple, but the measurement precision deteriorates when current varies over wide dynamic range
Solution Approach 1:
The patent divides the current measurement function into multiple segments by using different shunt resistors for different current ranges. A first shunt resistor handles low current measurements while a second shunt resistor handles high current measurements, with each optimized for its specific range to maintain measurement precision across the entire dynamic range.
Solution Approach 2:
The patent implements dynamic switching between different shunt resistors based on the current level being measured. The system automatically selects the appropriate shunt resistor (first or second) depending on whether the current is low or high, enabling adaptive measurement optimization without manual intervention.
2Measurement precision
If the shunt resistor value is changed to measure different current levels, then the measurement precision improves, but the acquisition bandwidth is impacted
Solution Approach 1:
The patent dynamically switches between different shunt resistor configurations based on the current measurement requirements. By selecting the appropriate shunt resistor in real-time according to the current level, the system maintains both high measurement precision and fast acquisition bandwidth without the trade-off present in static configurations.
Solution Approach 2:
The patent changes the shunt resistor parameter (resistance value) based on the current measurement range required. This parameter adaptation allows the system to optimize both precision and bandwidth by matching the shunt resistor characteristics to the specific measurement conditions.
3Reliability
If a single amplifier is used for power supply, then the device complexity is low, but the measurement reliability deteriorates during rapid current transitions
Solution Approach 1:
The patent segments the power supply function into multiple amplifiers, each dedicated to specific current ranges or operational modes. This segmentation allows each amplifier to be optimized for its specific function, improving overall measurement reliability during rapid current transitions while maintaining manageable system complexity.
Solution Approach 2:
The patent implements dynamic switching between different amplifier configurations based on the operational requirements. During rapid current transitions, the system activates appropriate amplifiers to maintain stable power supply and reliable measurements, adapting the amplifier configuration in real-time.
4Measurement precision
If high value shunt resistors are used for low current measurement, then the measurement precision improves, but the voltage drop increases affecting the load
Solution Approach 1:
The patent segments the measurement function by using different shunt resistors for different current ranges. High value shunt resistors are used only for low current measurements where precision is critical, while low value shunt resistors are used for high current measurements where voltage drop would be problematic, thus optimizing both precision and energy efficiency for each operating condition.
Solution Approach 2:
The patent changes the shunt resistor parameter (resistance value) based on the current measurement range. By adapting the resistance parameter to match the operating conditions, the system achieves high measurement precision for low currents while minimizing voltage drop and energy loss for high currents.
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
Enables high-frequency, wide-range current measurement with low background noise, accurately capturing both low and high current levels without altering the shunt resistor, thus improving measurement precision and bandwidth.
Implementation Method 1
using shunt resistors in series to measure the current consumption of the load with a first resistor having a high resistive value and a second resistor having a low resistive value
Data Source
AI summary
Load current consumption measured using a first resistor having a high resistive value and a second resistor having a low resistive value. Differential amplifiers, the outputs of which are coupled to analog-to-digital converters and to a processing circuit unit, are connected to each of the nodes of the resistors. Depending on the current level, the processing circuit unit advantageously selects one of the analog-to-digital converters to estimate the present consumption of current in the load. Each input terminal of a resistor is advantageously power supplied from a power amplifier and each power amplifier is advantageously driven by a control loop. For low load currents, the first amplifier associated with the first resistor power supplies the load through the resistors while, for high load currents, when this first amplifier saturates, the second amplifier associated with the second resistor, takes over from the first amplifier to continue to power supply the load.