On-State Voltage Sensing Circuit Without Diode Error
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Solution Overview
Problem
Existing on-state voltage measurement circuits for semiconductor switch elements are prone to inaccuracies due to variations in the forward voltage of diodes, especially when the on-state voltage is relatively small, affecting the measurement of the on-state voltage.
Innovation Solution
An on-state voltage measurement circuit that includes a detecting switch element, a control unit, a resistive element, and a voltage detection unit, where the resistive element has a higher resistance than the on-state resistance of the detecting switch element, allowing for accurate measurement of the on-state voltage by detecting the voltage across the resistive element when both the semiconductor switch element and the detecting switch element are on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is used to detect the voltage between main electrodes of a semiconductor switching element, then the protection circuit can detect short-circuit conditions, but the forward voltage variation of the diode significantly affects the measurement accuracy of the on-state voltage when the on-state voltage is relatively small
Solution Approach 1:
The patent introduces a detecting switch element as an intermediary component between the semiconductor switching element and the voltage detection unit. This detecting switch element, when turned on, creates a parallel conduction path that allows the voltage detection unit to measure the on-state voltage directly across the semiconductor switching element without being affected by diode forward voltage variations. The detecting switch element acts as a mediator that isolates the measurement system from the harmful diode voltage drop, thereby resolving the contradiction between short-circuit detection reliability and voltage measurement precision.
2Measurement precision
If the resistance value of the resistive element is made greater than the on-state resistance of the detecting switch element, then the voltage detection unit can accurately detect the on-state voltage, but the circuit complexity increases
Solution Approach 1:
The patent specifies a particular parameter relationship: the resistance value of the resistive element should be greater than the on-state resistance of the detecting switch element. This parameter change ensures that when both the semiconductor switching element and detecting switch element are on, the voltage across the resistive element accurately reflects the on-state voltage of the semiconductor switching element. By controlling this resistance parameter relationship, the patent achieves precise voltage measurement while keeping the circuit structure relatively simple, thus resolving the contradiction between measurement precision and device complexity.
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 proposed circuit enhances measurement accuracy of the on-state voltage and detects abnormal currents flowing through the semiconductor switch element, improving the reliability of the measurement process.
Implementation Method 1
A resistance value of the resistive element is greater than an on-state resistance of the detecting switch element. The voltage detection unit detects, based on a voltage across the resistive element when the semiconductor switch element and the detecting switch element are both on, the on-state voltage of the semiconductor switch element
Data Source
AI summary
An on-state voltage measurement circuit includes a detecting switch element, a control unit, a resistive element, and a voltage detection unit. The control unit includes a signal output terminal and a reference potential terminal and controls the detecting switch element. The resistive element is connected between a source terminal of the detecting switch element and the reference potential terminal. A resistance value of the resistive element is greater than an on-state resistance of the detecting switch element. The control unit turns the detecting switch element on when the semiconductor switch element is turned on. The voltage detection unit detects, based on a voltage across the resistive element when the semiconductor switch element and the detecting switch element are both on, the on-state voltage of the semiconductor switch element connected between a drain terminal of the detecting switch element and the reference potential terminal.