Desaturation Detection Circuit With Switched Voltage Division
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Solution Overview
Problem
Existing semiconductor device configurations for detecting desaturation status in switching elements increase power consumption and circuit scale due to the need for high breakdown voltage diodes and constant current sources during the OFF period.
Innovation Solution
A semiconductor device with a detection circuit and voltage generation circuit that uses a high breakdown voltage switch, variable resistor elements, and a voltage comparison circuit to detect inter-terminal voltage abnormalities without constant current sources, ensuring insulation and reducing power consumption by eliminating the need for high breakdown voltage diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high breakdown voltage diode is used to ensure insulation when the semiconductor switching element is turned off, then insulation is ensured, but the circuit scale increases
Solution Approach 1:
The patent extracts the high breakdown voltage requirement from the diode and applies it only to the switch component, while the detection circuit components (resistors, capacitors, comparators) can use standard breakdown voltage ratings. This selective application reduces the overall circuit scale while maintaining the necessary insulation performance during the OFF period.
Solution Approach 2:
The patent introduces a control signal that dynamically switches the detection circuit between active and inactive states. During the ON period, the detection circuit is active and monitors the inter-terminal voltage. During the OFF period, the detection circuit is inactive, and the switch provides insulation. This dynamic operation allows the use of standard voltage-rated components rather than requiring all components to withstand the full breakdown voltage.
2Measurement precision
If a constant current source is used to charge the capacitor during the OFF period to detect desaturation status, then desaturation detection is enabled, but power consumption increases
Solution Approach 1:
The patent employs periodic action by enabling the constant current source and detection circuit only during the ON period of the semiconductor switching element, when desaturation detection is actually needed. During the OFF period, these components are disabled to minimize power consumption. The switch controls the timing, allowing the system to perform detection periodically rather than continuously.
Solution Approach 2:
The patent prepares the detection circuit by pre-charging the capacitor during the ON period before the switching element turns off. This preliminary action ensures that when the switching element turns off and desaturation occurs, the capacitor is already in the correct state for accurate detection, eliminating the need for continuous current sourcing during the OFF period.
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 effectively detects desaturation status without increasing power consumption or circuit scale, ensuring accurate detection of inter-terminal voltage abnormalities while maintaining insulation during the OFF period.
Implementation Method 1
The switch has a breakdown voltage greater than at least a potential difference between the first potential and the second potential during an OFF period
Implementation Method 2
The detection circuit includes a switch, a first resistor element having a first electric resistance value, and a second resistor element having a second electric resistance value... At least one of the first resistor element and the second resistor element is a variable resistor element
Data Source
AI summary
During an ON period of a high breakdown voltage switch provided within an ON period of a semiconductor switching element, a detection circuit outputs to a predetermined node a voltage obtained by dividing an inter-terminal voltage by a plurality of resistor elements. A voltage comparison circuit outputs a detection signal indicating whether or not the inter-terminal voltage is greater than a predetermined determination voltage based on a comparison between the voltage of the predetermined node and a predetermined DC voltage. The high breakdown voltage switch has a breakdown voltage greater than a potential difference between a high potential and a low potential during an OFF period.