Semiconductor Switch with Auxiliary Element for Reverse Recovery Control
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Solution Overview
Problem
Conventional power conversion systems with freewheel diodes in inverse parallel configuration face issues of high reverse recovery current, complex circuitry, and timing constraints, leading to increased power supply requirements and reduced switching speed.
Innovation Solution
A semiconductor switch configuration featuring a high-voltage main element, a low-voltage auxiliary element, and a high-speed freewheel diode with a voltage equal to the main element, connected in inverse parallel, along with a gate driver and voltage clamping circuit, to suppress reverse recovery current and simplify the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional freewheel diode is used in inverse parallel with the switching element, then the circuit structure is simple, but reverse recovery current causes increased loss and reduced switching speed
Solution Approach 1:
The patent segments the freewheel diode function by introducing a separate auxiliary switching element (second switching element) that works in conjunction with the main switching element. This segmentation allows the main circuit to use a simple diode while the auxiliary circuit handles reverse recovery current suppression, resolving the contradiction between simple structure and reduced reverse recovery loss.
Solution Approach 2:
The patent introduces an auxiliary circuit with a second switching element and associated diodes as an intermediary mechanism. This intermediary circuit suppresses reverse recovery current by providing an alternative current path during switching transitions, thereby reducing reverse recovery loss without significantly complicating the main circuit structure.
2Loss of energy
If additional circuits are added to suppress reverse recovery current, then reverse recovery loss is reduced, but the circuit configuration becomes complicated and requires additional power supply
Solution Approach 1:
The auxiliary switching element serves multiple functions: it suppresses reverse recovery current, provides an alternative current path during dead time, and enables soft switching conditions. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall circuit complexity while achieving reverse recovery loss reduction.
Solution Approach 2:
The patent merges the reverse recovery suppression function with the existing switching element structure by using the second switching element in conjunction with the main switching element. The auxiliary circuit components are integrated into the overall power conversion circuit topology, combining multiple functions into a unified structure rather than adding separate independent circuits.
3Loss of energy
If additional switching elements are used to suppress reverse recovery current, then loss is reduced, but timing constraints tighten due to dead-time requirements
Solution Approach 1:
The auxiliary switching element is turned on in advance before the main switching element turns off, creating a pre-established current path. This preliminary action ensures that when the main switching element turns off, the reverse recovery current has an alternative path already available, reducing the need for extended dead time and allowing faster switching transitions.
Solution Approach 2:
The auxiliary circuit maintains continuous current flow during the transition period when the main switching element turns off. By keeping the auxiliary switching element and associated diodes active during this transition, the circuit ensures uninterrupted current path, eliminating the need for complete current interruption and reducing dead-time requirements.
Data Source
AI summary
A semiconductor switch is provided with a main element having reverse conductivity and serving as a voltage-driven switching element having a high withstand voltage, an auxiliary element serving as a voltage-driven switching element having a withstand voltage lower than that of the main element, and a high-speed freewheel diode having a withstand voltage equal to that of the main element, wherein a negative pole of the main element is connected to a negative pole of the auxiliary element to define the positive pole of the main element as a positive pole terminal and the positive pole of the auxiliary element as a negative pole terminal, and the high-speed freewheel diode is parallel-connected between the positive pole terminal and the negative pole terminal so that a direction from the negative pole terminal toward the positive pole terminal constitutes a forward direction.