Bidirectional Switch Power Circuit Reduces Losses
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Solution Overview
Problem
Typical power conversion circuits with unidirectional switches experience increased losses and size due to circulating currents when connected to loads with inductance components, and bidirectional switches with antiparallel IGBTs face challenges in preventing short-circuits and reducing losses.
Innovation Solution
A power conversion circuit employing a bidirectional switch with a nitride semiconductor structure that can operate in four states: as a diode in forward or reverse direction, bidirectionally conductive, or in an off state, preventing short-circuits and allowing intended circulating currents during transient periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unidirectional switches are used in the power conversion circuit, then the circuit structure is simple, but circulating current flows through the flywheel diode causing increased power loss
Solution Approach 1:
The patent changes the key parameter from unidirectional switch to bidirectional switch, which fundamentally alters the circuit's current handling capability. The bidirectional switch can conduct current in both directions, eliminating the need for the flywheel diode and preventing circulating current, thus reducing power loss while maintaining circuit simplicity.
Solution Approach 2:
The patent extracts and removes the flywheel diode from the circuit by replacing the unidirectional switch with a bidirectional switch. This elimination of the diode component directly prevents the circulating current path that causes power loss, while the bidirectional switch maintains the necessary circuit functionality.
2Loss of energy
If bidirectional switches with antiparallel IGBTs are used, then circulating current loss is reduced, but short-circuit risk increases and dead time is required
Solution Approach 1:
The patent employs dynamic control of the bidirectional switch through independent gate terminals that can be switched on and off in different combinations. This dynamic control allows the switch to adapt its state (bidirectional conduction, unidirectional conduction, or complete cutoff) based on real-time circuit conditions, preventing short-circuits during dead time while maintaining low circulating current loss during normal operation.
Solution Approach 2:
The bidirectional switch is segmented into two independent gate-controlled paths, allowing separate control of current flow in opposite directions. This segmentation enables precise control where one gate can be turned off to prevent short-circuits during dead time, while the other gate remains active to maintain low loss operation, thus resolving the contradiction between safety and efficiency.
3Reliability
If bidirectional switches are used in upper and lower arms, then short-circuit prevention is improved, but dead time increases power loss
Solution Approach 1:
The patent applies partial action by selectively controlling only the necessary gate terminals during dead time periods. Instead of completely shutting down all switches, the control circuit activates only the minimal required cutoff (one gate terminal) to prevent short-circuits, allowing other paths to remain conductive and minimize power loss during the dead time interval.
4Power
If diode is used in boost chopper circuit, then power conversion is achieved, but turn-on voltage loss increases power consumption
Solution Approach 1:
The patent changes the component parameter from diode to bidirectional switch in the boost chopper circuit. The bidirectional switch has a much lower on-resistance compared to the diode's turn-on voltage, significantly reducing power loss during power conversion while maintaining the same power transfer functionality.
Data Source
AI summary
A power conversion circuit includes a bidirectional switch 2. The bidirectional switch 2 has a first gate terminal G1, a second gate terminal G2, a first ohmic terminal S1 and a second ohmic terminal S2. The bidirectional switch 2 has four operation states. In the first state, the bidirectional switch 2 operates as a diode having a cathode as the first ohmic terminal S1 and an anode as the second ohmic terminal S2. In a second state, the bidirectional switch 2 operates as a diode having an anode as the first ohmic terminal S1 and a cathode as the second ohmic terminal S2. In a third state, the bidirectional switch 2 is bidirectionally conductive with via a diode between the first and second ohmic terminals S1 and S2. In a fourth state, the bidirectional switch 2 cuts off a bidirectional current between the first and second ohmic terminals.