Power MOSFET Reverse Diode Control for Lower Switching Loss
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Solution Overview
Problem
Conventional power MOSFETs experience increased switching losses and reduced switching speed due to the body diode, which conducts even when reverse biased, and are undesirable in applications like matrix converters where reverse conduction is not desired.
Innovation Solution
Incorporating a depletion control structure adjacent to the drift region that generates a depletion region based on a drive signal, allowing the transistor to be operated in a reverse mode without conducting, thereby deactivating the body diode and enhancing reverse blocking capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the body diode is forward biased to allow reverse conduction, then the MOSFET can conduct in reverse direction, but switching losses increase and switching speed decreases
Solution Approach 1:
The depletion control structure is activated before the body diode can conduct, creating a depletion region in the drift region that prevents charge carrier plasma accumulation. This preliminary action blocks reverse conduction before it can occur, avoiding the associated switching losses and maintaining high switching speed.
Solution Approach 2:
The invention applies a counter-action by generating a depletion region through the depletion control structure that opposes and prevents the forward bias conduction of the body diode. This preliminary anti-action ensures that reverse conduction is blocked before charge carrier plasma can form, thereby eliminating switching losses while maintaining reverse blocking capability.
2Adaptability or versatility
If the body diode is forward biased to enable reverse conduction, then the MOSFET conducts independently of gate control, but the charge carrier plasma accumulation increases switching losses
Solution Approach 1:
The depletion control structure creates a depletion region in the drift region before the body diode can accumulate charge carrier plasma. This preliminary action prevents the formation of conductive plasma, maintaining fast switching response and high switching speed while blocking reverse conduction.
3Reliability
If the source region and body region are short-circuited to prevent parasitic transistor impact, then the MOSFET functionality is protected, but only one pn junction remains that can be reverse biased
Solution Approach 1:
The invention segments the drift region by introducing a depletion control structure that creates a controlled depletion region. This segmentation allows the device to maintain the short-circuited source-body configuration for parasitic transistor control while adding a new functional element that enables reverse blocking capability through the depletion region in the drift region.
Solution Approach 2:
The depletion control structure acts as an intermediary element between the source-body short circuit and the drain region. It mediates the contradiction by providing a controlled depletion region that enables reverse blocking while maintaining the beneficial short-circuited configuration for parasitic transistor suppression.
4Adaptability or versatility
If a depletion control structure is added to generate a depletion region in the drift region, then reverse blocking capability is enhanced, but device complexity increases
Solution Approach 1:
The depletion control structure is merged with the existing drift region, utilizing the same semiconductor material and integration process. This merging approach enhances reverse blocking capability while minimizing additional structural complexity by combining functions within the existing device architecture rather than adding separate discrete components.
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 effectively prevents reverse conduction and increases the voltage blocking capability in the reverse direction, reducing switching losses and improving switching speed by pinching off the conducting channel in the drift region.
Implementation Method 1
a depletion control structure arranged adjacent the drift region, having a control terminal, and configured to generate a depletion region in the drift region dependent on a drive signal received at the control terminal
Data Source
AI summary
An electronic circuit includes a transistor device that can be operated in a reverse operation mode and a control circuit. The transistor device includes a source region, a drain region, a body region and a drift region, a source electrode electrically connected to the source region, a pn junction formed between the body region and the drift region, a gate electrode adjacent the body region and dielectrically insulated from the body region, and a depletion control structure adjacent the drift region. The depletion control structure has a control terminal and is configured to generate a depletion region in the drift region dependent on a drive signal received at the control terminal. The control circuit is coupled to the control terminal of the depletion control structure and configured to drive the depletion control structure to generate the depletion region when the transistor device is operated in the reverse operation mode.