Soft-Switching Inverter With Symmetric Current Sharing
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Solution Overview
Problem
Existing inverters with 3LTT switching legs suffer from conduction and switching losses which are detrimental to the efficiency of the system, and existing resonant topologies are not advantageous because they often require large components, incur high losses, and generate voltage imbalances.
Innovation Solution
An inverter with a switching unit and an auxiliary circuit with an asymmetrical transformer with magnetically coupled windings and secondary windings, configured to generate currents to alternatingly switch the parasitic capacitances of the switches before at least some switching operations of the switching unit, which includes an asymmetrical transformer, which reduces the switching losses, while at the same time requiring only minimal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If resonant topologies are used to achieve soft-switching, then switching losses are reduced, but component size increases and voltage imbalances are generated
Solution Approach 1:
The auxiliary circuit performs preliminary action by charging and discharging the parasitic capacitances of the main switches before the actual switching operations occur. This pre-conditioning of the capacitances enables zero-voltage switching without requiring large resonant components, thus reducing switching losses while avoiding the component size penalty of traditional resonant topologies.
2Loss of energy
If auxiliary components are added for soft-switching, then switching losses are reduced, but device complexity and cost increase
Solution Approach 1:
The auxiliary circuit is designed with multi-functionality, serving both to generate the commutation voltage for soft-switching and to charge/discharge the parasitic capacitances of the main switches. This universal approach reduces the need for separate dedicated components, thereby reducing overall device complexity and cost while achieving the goal of reduced switching losses.
3Loss of energy
If resonant topologies are used, then zero-voltage-switching is achieved, but voltage imbalances occur
Solution Approach 1:
The auxiliary circuit acts as an intermediary between the DC voltage source and the main switching leg. It generates the necessary commutation voltage and manages the charging/discharging of parasitic capacitances in a controlled manner, thereby achieving zero-voltage switching without the voltage imbalances that plague traditional resonant topologies. The intermediary auxiliary circuit isolates the main switching leg from the direct effects of resonant voltage oscillations.
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 efficacy of the system allows for a significant reduction in the switching losses, while at the same time requiring only small-scale components.
Implementation Method 1
The primary winding and the secondary winding are magnetically coupled. The asymmetrical transformer is configured to generate the current required to charge and discharge the parasitic capacitances of the switches.
Implementation Method 2
the auxiliary circuit is configured to generate a commutation voltage so as to enable zero-voltage-switching (ZVS) of switches of the switching unit
Data Source
AI summary
An inverter for generating an alternate current signal from a direct current signal is provided, including a positive voltage rail and a negative voltage rail. The inverter includes a switching unit, which, in turn, includes an alternating current output and a plurality of switches. Each of the plurality of switches includes a parasitic capacitance. The switching unit is configured to alternatingly switch the positive voltage of the direct current signal, a mid-point voltage between the positive voltage and the negative voltage of the direct current signal, and the negative voltage of the direct current signal to the alternating current output.