Current Sense Circuit Temperature Compensation
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Solution Overview
Problem
Current sense circuits face errors in output signal magnitude due to disparate temperature coefficients between main transistors and sense transistors, which become significant at varying current ranges.
Innovation Solution
An integrated circuit with a current sense circuit and a corrector circuit, where the corrector circuit generates a correction current to modify the output voltage of the current sense circuit, reducing errors caused by temperature-dependent on-resistance of the main transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sense circuit uses a sense transistor with different temperature coefficient than the main transistor, then the circuit can sense current, but the output signal magnitude develops error that increases with current magnitude
Solution Approach 1:
The patent introduces a correction circuit as an intermediary component that generates a correction signal to compensate for the temperature-dependent errors in the current sense circuit. This correction circuit acts as a mediator between the temperature variations and the sensing accuracy, offsetting the error without requiring direct modification of the main transistor or sense transistor pairing.
Solution Approach 2:
The patent modifies the output signal parameter by adding a correction signal that changes based on temperature conditions. The correction circuit dynamically adjusts the correction signal magnitude and polarity to compensate for temperature-induced errors, effectively changing the signal parameters to maintain accuracy across varying temperatures and current magnitudes.
2Power
If the main transistor size is increased to handle larger currents, then the current handling capability improves, but the temperature coefficient mismatch with the sense transistor increases causing larger errors
Solution Approach 1:
The patent segments the current sensing function into two independent parts: the main transistor handles the power current independently, while the sense transistor and correction circuit handle the measurement function independently. This segmentation allows the main transistor to be sized for power handling without compromising measurement precision, as the correction circuit compensates for any temperature coefficient mismatches.
Solution Approach 2:
The correction circuit serves as an intermediary that decouples the relationship between main transistor size and measurement accuracy. It generates a correction signal based on temperature conditions to offset errors introduced by large main transistor currents, allowing the system to handle high power while maintaining measurement precision regardless of the temperature coefficient mismatch.
Data Source
AI summary
An integrated circuit includes a current sense circuit having an input, an output, and a correction current input terminal between the input and output. A first transistor has a first control input and a first terminal. The first terminal is coupled to the input of the current sense circuit. A second transistor has a second control input and a second terminal. The second control input is coupled to the first control input, and the second terminal is coupled to the correction current input terminal.