Power Module Current Sensing Circuit Stabilizes Detection Voltage
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Solution Overview
Problem
Conventional power switching semiconductor devices face issues with false detection and accuracy drops in current sensing due to variations in current sensing resistance and power source fluctuations, whether using resistors or current mirror circuits.
Innovation Solution
A power module with a current sensing circuit that includes a first transistor connected to the output terminal of the current sense element, minimizing voltage changes and allowing for a stable voltage difference between the main and current sense elements, enabling accurate current sensing and arbitrary resistance settings for the current sensing resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensing resistor with smaller resistance is used to maintain current division ratio, then measurement accuracy is maintained, but the detection voltage becomes too small causing false detections
Solution Approach 1:
The current mirror circuit serves as a mediator that amplifies the effect of the sense current without requiring a large sensing resistor. By using the current mirror to generate a proportional mirror current that flows through the sensing resistor, the system can use a larger resistance value to generate sufficient detection voltage while the actual current division ratio in the power element remains undisturbed.
2Stability of the object's composition
If a current mirror circuit is used to sense current, then the detection voltage is stabilized against power source variations, but the sensing accuracy still deteriorates when power source voltage fluctuates
Solution Approach 1:
The patent employs feedback mechanisms through the current mirror circuit configuration where transistors Q1 and Q2 form a mirrored pair that automatically adjusts current distribution. The circuit uses the stable reference current from the main element to regulate the mirror current, creating a feedback loop that compensates for power source variations and maintains accurate sensing despite voltage fluctuations.
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 configuration enhances the accuracy of current sensing by stabilizing the voltage difference and preventing false detections, allowing for increased resistance settings without affecting current division ratios, thus improving reliability in overcurrent detection.
Implementation Method 1
a mirror current (current I4) obtained by the current mirror circuit is converted into a voltage by a current sensing resistor (resistor R1)
Data Source
AI summary
A power module includes a current sensing circuit in which a transistor includes an emitter connected to a sense emitter of a current sense element of an IGBT and a base connected to ground, a current sensing resistor including one end thereof connected to a collector of the transistor and the other end thereof connected to a common connection portion. The power module detects, as a current sensing voltage, a potential difference generated by the current sensing resistor based on the common connection portion as a reference, compares the current sensing voltage with a predetermined threshold voltage, and determines whether or not an overcurrent flows through the IGBT according to a magnitude relation therebetween.