Current Detection Circuit for Channel and Body Diode Separation
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Solution Overview
Problem
Existing current detection circuits in automotive chips fail to accurately detect the current flowing through a load, particularly when the current is high, leading to reduced detection accuracy due to neglecting the current through the body diode of the switching transistor.
Innovation Solution
The current detection circuit divides the current into two parts: one linearly related to the voltage difference and the other exponentially related to the voltage difference, using separate detection branches to accurately measure these parts, and combines them to determine the total current flowing through the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current detection branch is used to detect the current through the switch branch, then the device complexity is reduced, but the measurement precision deteriorates because the body diode current cannot be accurately separated from the channel current
Solution Approach 1:
The patent divides the current detection task into two separate detection branches: one dedicated to detecting the channel current and another for detecting the body diode current. This segmentation allows each branch to be optimized for its specific detection purpose, with the first branch measuring the voltage difference to determine channel current and the second branch measuring the body diode voltage to determine diode current, thereby achieving accurate total current measurement without excessive complexity
Solution Approach 2:
The patent introduces intermediate measurement nodes: the voltage difference between the signal input terminal and signal output terminal serves as an intermediary to infer channel current, while the body diode voltage serves as an intermediary to infer body diode current. These intermediary measurements enable accurate current detection through mathematical relationships without requiring direct current measurement
2Device complexity
If the current through the body diode is neglected in high current conditions, then the detection circuit simplicity is maintained, but the measurement precision deteriorates due to significant detection errors
Solution Approach 1:
The patent implements a dynamic detection approach where the circuit automatically adapts to different operating conditions. The switch branch dynamically switches between blocking and conducting states, and the detection circuit dynamically adjusts its measurement focus - detecting primarily channel current when the switch is on and accounting for body diode current when the switch is off, ensuring accurate measurement across all current conditions
Solution Approach 2:
The patent changes the measurement parameters based on the operating state. When the switch branch is conducting, the circuit measures the voltage difference to determine channel current. When the switch branch is blocking, the circuit measures the body diode voltage to determine body diode current. This parameter adaptation ensures accurate detection across different current magnitudes and switch states
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
This approach enhances detection accuracy by separately measuring the current through the channel and body diode of the switching transistor, allowing for precise determination of the total current flowing into the load.
Implementation Method 1
The first transistor is configured such that the equivalent internal resistance of the first transistor is K times the equivalent internal resistance of the switch branch
Implementation Method 2
the second current flowing through the body diode of the switching transistor, wherein the second current is exponentially related to the first voltage difference
Data Source
AI summary
A current detection circuit comprises a signal input terminal, a signal output terminal, a switch branch, a first current detection branch, and a second current detection branch. The switch branch is configured to block the current flowing from the signal output terminal to the signal input terminal when the switch branch is turned off. When the switch branch is conducting, the current flowing from the signal input terminal through the switch branch to the signal output terminal is the switch branch current comprising a first part linearly related to a first voltage difference, and a second part exponentially related to the first voltage difference. The first voltage difference is the voltage difference between the signal input terminal and the signal output terminal. The first current detection branch outputs a first detection current representing the first part. The second current detection branch outputs a second detection current representing the second part.