Semiconductor Dead-Time Circuit for Soft Shut-Off Protection
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Solution Overview
Problem
During the soft shut-off operation of a protection circuit, the increased time to execute the shut-off of switching devices can lead to excessive current flow due to arm shorts between high and low potential power supply terminals, even with an appropriate dead time provided, as the turn-off time of switching devices is longer than normal, potentially causing damage.
Innovation Solution
A semiconductor device with a dead-time generation circuit that includes status-detection circuits for each switching device to determine their turn-off states and logic circuits to control the on-off commands, ensuring that one switching device is only turned on after the other has completed its turn-off operation, thereby preventing arm shorts by dynamically adjusting the dead time based on the turn-on and turn-off times of the devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit with soft shut-off function is added to detect abnormalities and safely turn off switching devices, then the safety and reliability of the system is improved, but the turn-off time of switching devices increases more than normal turn-off time, which may cause arm short and excessive through-current
Solution Approach 1:
The dead-time generation circuit proactively extends the dead time period when soft shut-off is detected, before the actual switching occurs. This preliminary adjustment ensures that even if the switching device takes longer to turn off during soft shut-off operation, the complementary switching device will not be turned on prematurely, preventing arm short conditions.
Solution Approach 2:
The dead time period is made dynamic rather than fixed. The dead-time generation circuit adjusts the dead time duration based on the operating mode: using a normal dead time during regular operation and an extended dead time during soft shut-off operation. This dynamic adjustment allows the system to maintain safety during abnormal conditions while preserving normal switching performance during regular operation.
2Object-affected harmful factors
If an appropriate dead time is provided to prevent arm short between high potential and low potential power supply terminals, then the risk of short circuit is reduced, but during soft shut-off operation the increased turn-off time may still cause arm short before shut-off is completed
Solution Approach 1:
The system detects when soft shut-off operation is initiated and proactively extends the dead time period in advance. This ensures that the extended protection period is in place before the prolonged turn-off process begins, preventing any possibility of arm short even though the switching device will take longer to turn off during soft shut-off operation.
Solution Approach 2:
The dead-time generation circuit receives feedback signals indicating whether the switching device is in soft shut-off operation. Based on this feedback, the circuit automatically adjusts the dead time duration, extending it when soft shut-off is detected and maintaining normal duration otherwise. This feedback mechanism ensures appropriate dead time is always provided to prevent arm short under varying operating conditions.
Data Source
AI summary
The present invention relates to a semiconductor device provided with a dead-time generation circuit, the semiconductor device including: first and second status-detection circuits that each have a function of detecting whether first and second switching devices are in turn-off operation to output first and second status signals, respectively, and each have a function of generating a dead time of on-off operation of the corresponding one of the first and second switching devices; a first logic circuit that receives a first on-off command signal instructing the first switching device to be turned on or off, and the second status signal to output a signal allowing the first switching device to be turned on only when the second switching device is not in turn-off operation; and a second logic circuit that receives the first on-off command signal instructing the second switching device to be turned on or off, and the first status signal to output a signal allowing the second switching device to be turned on only when the first switching device is not in turn-off operation.