Variable Clamping Unit for Vehicle Inverter Overshoot Protection
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Solution Overview
Problem
In hybrid vehicle inverters, sudden switching stoppages due to short circuits or overvoltages can damage IGBT modules, and increasing breakdown voltages to prevent damage raises manufacturing costs and limits system voltage usage across different vehicle models.
Innovation Solution
A variable clamping unit with a clamping diode and a variable admittance, including a capacitor and resistance, that turns switching elements on to clamp overshoots and off after charging, preventing damage from excessive system voltages and counter-electromotive forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage of the clamping diode is set lower than the system voltage to clamp overshoots, then the IGBT module is protected from voltage spikes, but the switching element is continuously turned on during high-speed motor operation causing overheating and potential damage
Solution Approach 1:
The patent applies dynamics by making the clamping unit's breakdown voltage adjustable rather than fixed. The system dynamically adapts the clamping voltage level based on operating conditions - using a lower breakdown voltage for overshoot protection during switching events, and a higher breakdown voltage during high-speed motor operation to prevent continuous conduction and overheating of the switching element.
Solution Approach 2:
The patent changes the electrical parameter (breakdown voltage) of the clamping unit based on different operational states. By varying the breakdown voltage parameter, the system achieves dual functionality: protecting against voltage spikes when needed while allowing normal high-voltage operation without continuous conduction, thus resolving the temperature issue.
2Power
If the breakdown voltage of the IGBT module and clamping diode is increased to allow higher system voltage operation, then the inverter can operate at higher voltages for improved motor performance, but the manufacturing cost increases and the IGBT module must be changed
Solution Approach 1:
The patent changes the breakdown voltage parameter of the clamping unit to match different system voltage requirements without changing the IGBT module itself. This allows the same IGBT module to be used across different voltage systems by simply adjusting the clamping unit's electrical characteristics, thereby reducing manufacturing costs and improving ease of manufacture.
Solution Approach 2:
The patent makes the clamping unit universal by designing it to be adjustable across different voltage levels. This single adjustable clamping unit can serve multiple system voltage configurations, eliminating the need for different IGBT modules for different voltage requirements and reducing overall system complexity and manufacturing cost.
3Reliability
If the switching elements are suddenly stopped to prevent damage from short circuits or overvoltage, then the IGBT module is protected from excessive current, but an overvoltage is instantaneously caused between the drain and source ends damaging the IGBT module
Solution Approach 1:
The patent applies beforehand cushioning by providing a clamping unit that is ready to activate before the IGBT module can be damaged by overvoltage. The clamping unit with its adjustable breakdown voltage acts as a protective cushion that activates during voltage spikes, absorbing the harmful overvoltage energy and preventing it from reaching the IGBT module, thus protecting against both excessive current and subsequent overvoltage 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
This solution enhances inverter efficiency, reduces costs, and allows for higher system voltage usage without IGBT module changes, enabling improved motor performance and miniaturization while reducing weight and volume.
Implementation Method 1
a capacitor that is charged by current which flows from the clamping unit
Implementation Method 2
If the breakdown voltage of the clamping diode D1 is set to be lower than the breakdown voltage of the IGBT module 10, and the VDS voltage is increased to a value higher than the breakdown voltage of the clamping diode D1, the clamping diode D1 is turned on, which makes current ID1 flow through the clamping unit 20
Data Source
AI summary
The present invention provides an inverter circuit for a vehicle, which includes: a switching unit that includes a plurality of switching elements and switches a direct current into an alternating current; and a variable clamping unit that clamps an overshoot in case the overshoot is generated, and stops the operation of the switching unit in case a system voltage is greater than a clamping breakdown voltage. The circuit enables a voltage (DC input voltage) greater than a breakdown voltage of clamping unit to be used as a system voltage.