Synchronous Rectification in Three-Level Inverter-Converter Topologies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power inverter/converter topologies in aerospace applications suffer from significant static losses due to voltage drops across diodes, which are not effectively mitigated by existing technologies, particularly in uni-directional active rectifiers like the Vienna Rectifier.
Innovation Solution
The implementation of synchronous rectification using silicon carbide (SiC) power MOSFETs and SiC Schottky diodes in parallel configurations within a three-level power module, where the synchronous rectifier switches are controlled to operate in conjunction with diodes to reduce voltage drops and prevent shoot-through conditions, along with current sensing and control logic to manage their operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional diodes are used in rectifier circuits, then the circuit structure is simple, but significant voltage drops occur causing high static losses
Solution Approach 1:
The patent combines a power FET and a diode into a synchronous rectifier unit where the FET is connected in parallel with the diode. The FET is controlled to conduct in synchrony with the diode, merging the low on-resistance advantage of FETs with the simplicity of diode circuits, thereby reducing voltage drops and static losses while maintaining manageable circuit complexity
Solution Approach 2:
The patent introduces dynamic control of the power FET switching states based on the conduction state of the diodes. The FETs are turned on and off in synchronization with the diode conduction, transforming the static diode rectifier into a dynamically controlled synchronous rectifier system that adapts to load conditions and minimizes losses
2Loss of energy
If power FETs are used to reduce voltage drop, then efficiency improves, but the risk of shoot-through conditions increases
Solution Approach 1:
The patent implements control logic that monitors the conduction state of the diodes and uses this feedback to control the switching of the power FETs. The FETs are turned on only when their corresponding diodes are conducting, and turned off when the diodes stop conducting, creating a feedback-based control mechanism that prevents shoot-through conditions while maintaining low voltage drops
Solution Approach 2:
The control system prepares the power FETs for conduction in advance by turning them on slightly before the diodes begin to conduct, and ensures they are turned off before the diodes stop conducting. This preliminary action approach ensures smooth current transfer and prevents shoot-through conditions by maintaining proper timing margins
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 significantly reduces static losses and enhances efficiency by lowering voltage drops across the circuit, making the power module more suitable for high-frequency and high-power applications, including aerospace uses.
Implementation Method 1
Synchronous rectification is a concept that has been applied in the past, particularly in DC-DC converters at low output voltage levels. Synchronous rectification involves the use of a power FET connected in parallel with a diode, wherein the FET is configured to be turned on when the diode is conducting, so that current flow is re-directed through the FET.
Implementation Method 2
a voltage drop of 0.4 V to about 1.0 V in the output rectifier is common and would be converted into a significant loss
Data Source
AI summary
A power module is disclosed having a first module block defining a first rectifier and including a first rectifier switch having a first FET and connected in parallel with a first diode, a second module block including a second FET connected in parallel with a second diode, a third module block including a third FET connected in parallel with a third diode, wherein the second and third module blocks are positioned between first and second terminal interfaces of the power module, and wherein two serially connected diodes are on the first interface side of the power module in parallel with the serially connected second and third module blocks, and a fourth module block defining a second rectifier and including a second rectifier switch having a fourth FET and connected in parallel with a fourth diode.