Desaturable Semiconductor Device Auxiliary Cells
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Solution Overview
Problem
Semiconductor devices with transistor cells and diode functionality face dynamic switching losses due to reverse recovery current, which is not effectively mitigated by existing desaturation mechanisms as charge carrier plasma partially recovers during safety periods, affecting switching characteristics.
Innovation Solution
The semiconductor device incorporates two types of auxiliary cells - desaturation injection cells and saturation injection cells, with different charge carrier injection efficiencies based on gate voltage thresholds, to manage charge carrier plasma density during saturation and desaturation periods, ensuring low forward voltage and reduced switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a desaturation period is introduced to reduce dynamic switching losses, then switching losses are reduced, but charge carrier plasma partially recovers during safety periods, foiling the desaturation mechanism
Solution Approach 1:
The patent introduces auxiliary cells that perform preliminary action by injecting charge carriers into the drift structure before the main commutation event. This preliminary injection of charge carriers prepares the device for efficient switching by ensuring adequate plasma density is maintained despite the desaturation period, preventing plasma depletion and maintaining low forward voltage during critical periods.
Solution Approach 2:
The patent changes parameters by introducing auxiliary cells with specific injection characteristics that modify the charge carrier plasma density in the drift structure. These parameter changes ensure that the plasma density remains optimized for low loss switching while maintaining the effectiveness of the desaturation mechanism, resolving the contradiction between energy loss reduction and mechanism reliability.
2Loss of energy
If charge carrier plasma is attenuated during desaturation to reduce reverse recovery current, then reverse recovery losses are reduced, but forward voltage increases during desaturation periods
Solution Approach 1:
The patent applies local quality by introducing auxiliary cells with specific local injection characteristics into the drift structure. These auxiliary cells provide localized charge carrier injection that maintains plasma density in critical regions during desaturation periods, ensuring low forward voltage is maintained locally even while overall plasma attenuation occurs to reduce reverse recovery losses.
Solution Approach 2:
The patent changes parameters by controlling the injection characteristics of auxiliary cells to dynamically adjust plasma density. This parameter control allows the device to achieve reduced reverse recovery losses through plasma attenuation while simultaneously maintaining adequate plasma density to keep forward voltage low during desaturation periods.
3Use of energy by moving object
If auxiliary cells inject charge carriers to maintain plasma density, then forward voltage remains low, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the device into transistor cells and auxiliary cells with distinct functions. The auxiliary cells are strategically positioned and configured to provide targeted charge carrier injection, maintaining plasma density and low forward voltage without requiring complete redesign of the entire device structure, thus managing complexity through functional segmentation.
Solution Approach 2:
The auxiliary cells serve multiple functions: they inject charge carriers to maintain plasma density, ensure low forward voltage during desaturation periods, and support the overall switching operation. This multi-functionality reduces the need for additional separate components, managing device complexity while achieving the desired electrical characteristics.
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 approach effectively reduces dynamic switching losses by maintaining low forward voltage during desaturation periods and optimizing charge carrier injection efficiency, enhancing the overall switching characteristics of semiconductor devices.
Implementation Method 1
First auxiliary cells in a vertical projection of and electrically connected with the first load electrode are configured to inject charge carriers into the drift structure at least in a forward biased mode of the first pn junctions
Implementation Method 2
transistor cells configured to connect a first load electrode with a drift structure forming first pn junctions with body zones when a gate voltage applied to a gate electrode exceeds a first threshold voltage
Implementation Method 3
mobile charge carriers flood a semiconductor region along a forward biased pn junction and form a dense charge carrier plasma resulting in a low forward resistance of the diode
Implementation Method 4
When the concerned pn junction commutates thereby changing from forward biased to reverse biased, a reverse recovery current removes the charge carrier plasma
Data Source
AI summary
A semiconductor device includes transistor cells that connect a first load electrode with a drift structure forming first pn junctions with body zones when a gate voltage applied to a gate electrode exceeds a first threshold voltage. First auxiliary cells in a vertical projection of and electrically connected with the first load electrode are configured to inject charge carriers into the drift structure at least in a forward biased mode of the first pn junctions. Second auxiliary cells are configured to inject charge carriers into the drift structure at high emitter efficiency when in the forward biased mode of the first pn junctions the gate voltage is below a second threshold voltage lower than the first threshold voltage and at low emitter efficiency when the gate voltage exceeds the second threshold voltage.