Conditional Active Clamping for Power Semiconductor Switches
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Solution Overview
Problem
Conventional active clamping technology is not applicable in self-propelled applications like Hybrid Electrical Vehicles (HEV) due to back electromagnetic force (BEMF) exceeding the designed activation voltage, leading to potential destruction of controllable power semiconductor switches.
Innovation Solution
A power semiconductor arrangement with a controllable switch, driver unit, and active clamping (AC) unit that enables or disables AC based on voltage levels, using a Z-diode break over unit and capacitor to manage overvoltages during switching events, ensuring the AC unit is only activated when necessary to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional active clamping (AC) technology is implemented, then overvoltage protection is provided, but the controllable power semiconductor switch may be destroyed by back electromagnetic force (BEMF) in self-propelled applications
Solution Approach 1:
The patent applies dynamics by making the active clamping function conditional rather than static. The switching unit dynamically activates or deactivates the AC unit based on real-time detection of voltage levels. When the voltage across the power semiconductor switch exceeds a predetermined threshold, the switching unit activates the AC unit to provide overvoltage protection. This dynamic control resolves the contradiction by enabling protection only when needed, preventing BEMF-induced damage while maintaining reliability during normal operation.
2Reliability
If AC unit is always activated, then overvoltage protection is ensured, but false activation occurs when BEMF exceeds activation voltage
Solution Approach 1:
The patent implements feedback through a voltage detection mechanism that continuously monitors the voltage across the controllable power semiconductor switch. The switching unit receives feedback signals indicating whether the voltage exceeds the predetermined threshold. This feedback loop enables the system to distinguish between normal high-voltage conditions (such as BEMF during regenerative braking) and actual overvoltage faults, activating the AC unit only when genuinely needed. This resolves the contradiction by preventing false activation while ensuring protection when required.
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 limits maximum voltage across controllable power semiconductor switches to below their breakdown voltage, preventing damage during transitions from ON to OFF states, even at high supply voltages, thus ensuring safe operation in self-propelled applications.
Implementation Method 1
designed to switch the load path in the ON-state if the voltage affecting the controllable power semiconductor switch is higher than or equal to a pre-defined allowable voltage
Data Source
AI summary
A power semiconductor arrangement including conditional active clamping (CAC). One embodiment includes a power semiconductor arrangement. A controllable power semiconductor switch includes a load path. A driver unit for switching the load path to either an ON-state or an OFF-state. An active clamping (AC) unit configured to switch the load path in the ON-state if the voltage affecting the controllable power semiconductor switch is higher than or equal to an allowable voltage. A switching unit includes a control input, and configured to activate and/or to deactivate the AC unit dependent on a signal applied to the control input.