Dual Resistor Current Measurement Circuit for Wide Dynamic Range
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Solution Overview
Problem
Conventional methods fail to accurately measure current consumption of active loads, such as processing units, due to the inability to handle a broad dynamic range of currents at high frequencies without generating excessive noise or losing samples during switching between low and high current measurements.
Innovation Solution
A method involving two resistors in series between a voltage source and an active load, where the first resistor measures low currents with higher sensitivity and the second resistor measures high currents, with a stabilization circuit maintaining voltage at a threshold value to prevent excessive voltage drops, allowing simultaneous measurement of both ranges without sample loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single resistor connected to an amplifier is used for current measurement, then the measurement circuit is simple, but it cannot accurately measure both very low currents (0.3 microamperes) and very high currents (3 milliamperes) at high frequencies due to noise generation at high frequencies
Solution Approach 1:
The measurement circuit is segmented into two separate resistor-amplifier paths: one path with a first resistor and first amplifier optimized for low current measurement, and another path with a second resistor and second amplifier optimized for high current measurement. This segmentation allows each path to be independently optimized for its specific current range, achieving high measurement precision across the full dynamic range without requiring a single complex circuit
Solution Approach 2:
The circuit dynamically switches between the low current measurement path and high current measurement path based on the detected current level. When the current exceeds a threshold, the switching element connects the high current path; when the current is below the threshold, the low current path is used. This dynamic adaptation enables accurate measurement across a broad dynamic range while maintaining circuit simplicity
2Measurement precision
If two resistors each connected to separate amplifiers are used for measuring low and high currents, then measurement accuracy across dynamic range is improved, but the switching system is too slow and causes sample loss during current transitions
Solution Approach 1:
The patent replaces the mechanical switching system with voltage-controlled switches (such as MOSFETs or analog multiplexers) that can transition between states in nanoseconds or microseconds. This substitution eliminates the mechanical inertia and contact bounce issues, achieving switching speeds fast enough to capture brief current events without sample loss
Solution Approach 2:
The circuit continuously monitors the current level and pre-positions the switching element in the appropriate measurement path before the current transition completes. This preliminary action ensures that the measurement path is already configured correctly when the current reaches the threshold level, preventing any measurement gaps or sample losses during transitions
3Speed
If high frequency amplifiers are used for fast current measurement, then measurement speed is improved, but noise generation increases making very low current measurement impossible
Solution Approach 1:
The amplification function is segmented into two separate amplifiers: a first amplifier with high gain and low bandwidth optimized for low current measurement at lower frequencies, and a second amplifier with lower gain and high bandwidth optimized for high current measurement at high frequencies. This segmentation allows each amplifier to operate in its optimal frequency range, achieving fast measurement speed for high currents while maintaining low noise performance for low currents
Solution Approach 2:
The circuit changes the operational parameters (gain and bandwidth) by switching between two different amplifier paths based on the current level. For low currents, the first amplifier operates with high gain and narrow bandwidth to minimize noise. For high currents, the second amplifier operates with lower gain and wide bandwidth to handle high frequencies. This parameter change through switching resolves the contradiction between speed and noise
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 accurate measurement of current consumption across a wide dynamic range without noise interference or sample loss, allowing for precise determination of both low and high current values with enhanced sensitivity.
Implementation Method 1
a first resistor and a second resistor are disposed in series between the voltage source and a first terminal of the active load, the first resistor having a resistance value greater than a resistance value of the second resistor
Data Source
AI summary
A first resistor and a second resistor are coupled in series between a voltage source and an active load. When the current drawn by the active load exceeds a current threshold corresponding to a maximum admissible voltage drop across the first resistor, a stabilization current is delivered to the node common to the series coupled first and second resistors in such a way as to stabilize the voltage on the terminals of the active load at a threshold value. In the presence of such a current in excess of the current threshold, the current consumed by the active load is measured from the voltage drop across the second resistor. Conversely, if the current is less than the current threshold, the current consumed by the active load is measured from the voltage drop across the first resistor.