Auto-Ranging Current Sense Circuit With Dynamic Bias and Gain Control
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Solution Overview
Problem
Current sense circuits face errors due to mismatch between power and sense transistors, amplifier offset, gain limitations, and noise, particularly at high and low load currents, affecting accuracy in current sensing.
Innovation Solution
A dynamically controlled auto-ranging current sensing circuit that adjusts the bias voltage, current gain, and sense resistor resistance to improve sensing accuracy, using a controller to modify the operation of the sense transistor and sense resistor, and employing a low-resolution ADC to match performance with high-resolution systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed bias voltage is applied to the sense transistor, then the circuit structure is simple, but sensing accuracy deteriorates at varying load currents
Solution Approach 1:
The patent implements dynamic bias voltage adjustment by controlling the gate voltage of the sense transistor based on detected load current levels. The controller modifies the bias voltage in real-time to optimize the sense transistor's operating point, transforming a static circuit into a dynamic one that adapts to varying current conditions, thereby resolving the contradiction between simple structure and accurate measurement.
Solution Approach 2:
The patent changes the electrical parameters (bias voltage, gain ratio) of the sense circuit dynamically based on load current conditions. By adjusting these parameters according to the detected current level, the system maintains high measurement precision across different operating ranges without requiring a completely complex reconfiguration of the circuit architecture.
2Measurement precision
If high gain is used in the amplifier, then sensing accuracy at low currents improves, but noise and offset errors increase
Solution Approach 1:
The patent dynamically adjusts the amplifier gain based on the detected load current level. At low current levels, higher gain is applied to amplify weak signals for accurate measurement. At high current levels, the gain is reduced to prevent saturation and minimize the impact of noise and offset errors. This dynamic gain adjustment resolves the contradiction between sensitivity and noise performance.
Solution Approach 2:
The system changes the amplifier's gain parameter adaptively according to the operating conditions. By modifying the gain ratio between load current and sensing current based on the actual current level, the patent optimizes the signal-to-noise ratio while maintaining measurement accuracy across the full current range.
3Measurement precision
If high-resolution ADC is used, then measurement precision improves, but power consumption increases
Solution Approach 1:
The patent implements a dynamic ranging system that adjusts the sense circuit parameters to match the input signal level. By optimizing the bias voltage and gain settings according to the detected current range, the system maximizes the utilization of a low-resolution ADC's dynamic range, achieving high measurement precision without requiring the continuous operation of a high-resolution ADC, thus reducing power consumption.
Solution Approach 2:
The system dynamically changes the operating parameters of the sense circuit to optimize the output signal for a low-resolution ADC. By adjusting the bias voltage and gain ratio based on the input current level, the patent ensures that the ADC operates in its optimal range, achieving high effective precision while consuming less power than a fixed high-resolution ADC configuration.
4Quantity of substance
If sense transistor W/L ratio is increased, then sensing current increases, but mismatch errors between power and sense transistors worsen
Solution Approach 1:
The patent dynamically adjusts the bias voltage applied to the sense transistor based on the detected load current level. By optimizing the gate voltage in real-time, the system maximizes the sensing current output without requiring extreme W/L ratios, thereby reducing the impact of transistor mismatch errors while maintaining high sensing current levels when needed.
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 sensing accuracy by reducing errors and maintaining output voltage within a set range across varying load currents, improving dynamic range and noise performance while allowing the use of a low-resolution ADC for reduced power consumption.
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.