Auto-Ranging Current Sense Circuit for Wide-Range Accuracy
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Solution Overview
Problem
Current sense circuits face errors due to mismatch between power and sense transistors, amplifier offset, and gain limitations, which affect accuracy in sensing load currents, especially at high and low current levels.
Innovation Solution
A dynamically controlled auto-ranging current sensing circuit that adjusts the bias voltage, current gain, and resistance of the sense resistor to improve sensing accuracy, using a low-resolution ADC to match performance with high-resolution systems, and controls the size of the sense transistor and sense resistor to maintain output voltage within a dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed current sense circuit is used, then the circuit structure is simple, but the sensing accuracy deteriorates across varying current levels due to transistor mismatch, amplifier offset, and gain limitations
Solution Approach 1:
The patent implements dynamic adjustment of circuit parameters including sense transistor size, sense resistor value, and amplifier gain through switching elements controlled by a controller. This allows the circuit to adapt its configuration based on current levels, maintaining high sensing accuracy across varying load conditions while managing complexity through controlled dynamism
Solution Approach 2:
The patent changes physical parameters of the sense circuit including transistor channel width/length ratios, resistor values, and amplifier gain settings. By adjusting these parameters dynamically based on operating conditions, the circuit maintains optimal sensing accuracy across different current ranges while balancing the added complexity of parameter control mechanisms
2Power
If high load currents are sensed, then the power delivery is high, but the transistor mismatch and metallization errors increase significantly
Solution Approach 1:
The patent dynamically adjusts the sense transistor size and configuration based on detected current levels. At high load currents, the circuit switches to configurations with larger transistors and adjusted metallization ratios, reducing the relative impact of mismatch and metallization errors while maintaining high power delivery capability
Solution Approach 2:
The patent modifies transistor W/L ratios and metallization dimensions as operating parameters based on current level. At high currents, larger transistor sizes and adjusted metallization are employed to reduce percentage errors, while at lower currents, smaller configurations are used to maintain accuracy
3Use of energy by moving object
If low load currents are sensed, then the power consumption is low, but the amplifier offset and gain limit cause significant sensing errors
Solution Approach 1:
The patent dynamically switches amplifier configurations and sense circuit parameters based on detected current levels. At low load currents, the circuit employs configurations with higher amplifier gain and reduced offset effects, while maintaining low power consumption through selective activation of circuit elements
Solution Approach 2:
The patent adjusts amplifier gain settings and offset compensation parameters based on operating conditions. At low currents, higher gain configurations are activated to amplify small signals above the noise floor, while offset compensation is tuned to minimize errors in the low-signal regime
4Quantity of substance
If the sense transistor size is increased, then the sensing current capacity is high, but the mismatch with power transistor increases
Solution Approach 1:
The patent dynamically adjusts the sense transistor size to match operating conditions. Rather than using a fixed large sense transistor, the circuit switches between different transistor size configurations based on current level, maintaining adequate sensing capacity while minimizing mismatch errors at each operating point
Solution Approach 2:
The patent varies the sense transistor W/L ratio as a controllable parameter. By adjusting this parameter to match the power transistor characteristics at different operating points, the circuit maintains both adequate sensing current capacity and minimal mismatch error
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
The solution enhances the dynamic range and noise performance of current sensing, reducing errors and maintaining accuracy across varying load currents by dynamically adjusting the circuit parameters, allowing for efficient current sensing with a low-resolution ADC.
Implementation Method 1
a sense transistor for sensing the current provided by a main transistor
Implementation Method 2
a sense resistor for converting the sensed current to a voltage value
Data Source
AI summary
Embodiments relate to sensing a current provided by a power supply circuit. The current sensing circuit includes a sense transistor for sensing the current provided by a main transistor, a driver for controlling a bias provided to the sense transistor and the main transistor, and a sense resistor for converting the sensed current to a voltage value. Moreover, the current sensing circuit includes a controller that modifies at least one of: (a) a resistance of the main transistor by adjusting the bias voltage provided by the driver, (b) a gain ratio between a load current and a sensing current by adjusting a number of individual devices that are active in the sense transistor, and (c) a resistance of the sense resistor.