Flywheel Diode Structure for Power Conversion Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current power conversion devices, such as inverters, face challenges in reducing power loss due to high forward voltage drops and backward recovery currents in flywheel diodes, which hinder efficiency, size reduction, and cost-effectiveness.
Innovation Solution
A semiconductor device structure featuring a semiconductor substrate with specific conductivity type layers and electrodes, including a MOSFET configuration with a trench gate and Schottky junction, which reduces forward voltage drops and backward recovery currents by controlling the flow of current and electric charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a pn diode made of silicon is used for the flywheel diode to decrease the forward voltage drop, then the conduction loss is reduced, but the backward recovery current increases causing turn-on loss in the IGBT
Solution Approach 1:
The patent combines a pn junction diode structure with a Schottky barrier diode structure to create a composite diode. The pn junction provides low forward voltage drop through conductivity modulation, while the Schottky barrier prevents backward recovery current by blocking reverse bias operation. This composite structure resolves the contradiction by integrating the advantages of both diode types.
Solution Approach 2:
The patent creates different functional regions within the diode structure. The forward conduction path utilizes the pn junction region for low voltage drop, while the reverse blocking function is handled by the Schottky barrier region. This local differentiation of function allows simultaneous optimization of forward conduction and reverse blocking characteristics.
2Object-generated harmful factors
If a Schottky diode is used for the flywheel diode to decrease the backward recovery current, then the turn-on loss is reduced, but the forward voltage drop increases causing high conduction loss
Solution Approach 1:
The patent integrates a Schottky barrier diode structure with a pn junction diode structure. The Schottky barrier portion handles reverse blocking to minimize backward recovery current, while the pn junction portion provides low forward voltage drop for reduced conduction loss. This composite approach resolves the contradiction between reverse recovery performance and forward conduction efficiency.
Solution Approach 2:
The composite diode structure performs multiple functions simultaneously: the Schottky barrier provides reverse voltage blocking and prevents backward recovery current, while the pn junction provides low-resistance forward conduction path. This multi-functionality allows a single device to optimize both forward and reverse operating characteristics.
3Adaptability or versatility
If the flywheel diode repeats switching with the IGBT, then the motor speed can be controlled, but the accumulated electric charges discharge as backward recovery current increasing power loss
Solution Approach 1:
The patent uses a composite diode structure where the Schottky barrier portion blocks the backward recovery current that would otherwise flow during IGBT switching transitions. This allows the inverter to maintain full switching capability for motor speed control while the Schottky barrier prevents the harmful backward recovery current, reducing power loss during switching operations.
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 semiconductor device effectively decreases forward voltage drops and backward recovery currents, enhancing the efficiency and voltage resistance of power conversion devices while maintaining cost-effectiveness.
Implementation Method 1
an anode electrode... in contact with the fifth semiconductor layer and the fourth semiconductor layer... having a reverse blocking characteristic
Implementation Method 2
a gate electrode provided on the other surface of the semiconductor substrate; and a gate insulating film formed between the gate electrode and the semiconductor substrate
Implementation Method 3
a cathode electrode provided on the one surface side of the semiconductor substrate and in ohmic contact with the first semiconductor layer
Data Source
AI summary
The invention provides an inexpensive flywheel diode having a low power loss. A semiconductor substrate side of a gate electrode provided on a surface of an anode electrode side of a semiconductor substrate including silicon is surrounded by a p layer, an n layer, and a p layer via a gate insulating film. The anode electrode is in contact with the p layer with a low resistance, and is also in contact with the n layer or the p layer, and a Schottky diode is formed between the anode electrode and the n layer or the p layer.