Switching Element Gate Control With Timed Forced Turn-Off
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Solution Overview
Problem
Conventional power converters may experience thermal damage to switching elements due to failure in IGBTs or MOSFETs, leading to an abnormal state where the gate voltage does not decrease, preventing the switching element from turning OFF despite drive signal instructions.
Innovation Solution
An electronic device with a control circuit that uses a time drive circuit (or switching circuit) to turn OFF the switching element after a predetermined period from the timing when the drive signal switches from ON to OFF, ensuring the switching element is turned OFF even if the control terminal voltage does not decrease, thereby preventing thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive signal switches from ON to OFF instruction, then the switching element should turn OFF, but the gate voltage does not decrease due to component failure, preventing the switching element from turning OFF
Solution Approach 1:
The control circuit performs preliminary action by detecting component failures (open/short circuits in MOSFETs or IGBT) before thermal damage occurs. When a failure is detected, the control circuit proactively switches off the IGBT by controlling the MOSFETs to prevent the abnormal state from escalating into thermal damage, even though the gate voltage does not naturally decrease.
Solution Approach 2:
The control circuit implements feedback by continuously monitoring the operational state of the switching elements and detecting abnormalities. When the control circuit detects that a MOSFET or IGBT has failed (open or short circuit), it receives feedback about the abnormal state and responds by adjusting the control signals to switch off the IGBT, thereby preventing thermal damage to the switching element.
2Device complexity
If the control circuit uses only the OFF-drive switching element to turn OFF the switching element, then the control circuit is simple, but thermal damage occurs when the OFF-drive switching element fails
Solution Approach 1:
The control circuit is segmented into multiple independent control paths: an ON-drive switching element (first MOSFET) for turning on the IGBT, an OFF-drive switching element (second MOSFET) for turning off the IGBT, and a failure detection mechanism. This segmentation allows the control circuit to maintain simplicity while adding protective functionality through the third MOSFET that activates only upon detecting failures in the other components.
Solution Approach 2:
The control circuit changes its operational parameters dynamically based on detected failures. Under normal conditions, it operates with the standard ON-drive and OFF-drive MOSFETs. When a failure is detected (open or short circuit in MOSFETs or IGBT), the control circuit changes its control strategy by activating the third MOSFET with specific timing to force the IGBT off, thereby adapting to the abnormal state and preventing thermal damage.
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
Effectively prevents thermal damage to switching elements by ensuring they can be turned OFF even in abnormal states where the control terminal voltage fails to decrease, maintaining operational integrity.
Implementation Method 1
an ON-drive switching element that is connected to the control terminal of the switching element and charges the control terminal of the switching element with electrical charge by being turned ON
Implementation Method 2
an OFF-drive switching element that is connected to the control terminal of the switching element and discharges electrical charge from the control terminal of the switching element by being turned ON
Data Source
AI summary
In an electronic device with a switching element, a control circuit controls the voltage at the control terminal of the switching element and drives the switching element, by controlling an ON-drive switching element and an OFF-drive switching element based on an inputted drive signal to the control circuit. The control circuit is configured to turn OFF a switching element using a switching circuit other than the OFF-drive switching element after an elapse of a predetermined period of time from a timing at which the drive signal switches from an ON instruction thereof to an OFF instruction thereof, the ON instruction giving an instruction to turn ON the switching element, the OFF instruction giving an instruction to turn OFF the switching element.