Parallel GaN Flyback Switching to Limit On-Resistance Drift
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Solution Overview
Problem
Gallium nitride (GaN) transistors used in flyback converters experience increased on resistance and reduced efficiency when switching high voltages and currents, leading to degraded performance over time.
Innovation Solution
A flyback converter control circuit utilizing a parallel configuration of a main GaN transistor and an auxiliary GaN transistor, controlled by a controller that turns on the auxiliary transistor first during voltage valleys to reduce stress on the main transistor, thereby minimizing on resistance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single GaN transistor is used to switch high voltages and currents, then the converter achieves high power density and fast switching, but the on resistance increases and efficiency degrades over time
Solution Approach 1:
The patent divides the single transistor function into two parallel transistors (first and second transistors), each handling different portions of the switching duty cycle. This segmentation reduces the stress on each individual transistor, minimizing on-resistance degradation while maintaining high power density and efficiency
2Device complexity
If a single GaN transistor handles all switching operations, then the circuit complexity is low, but the transistor experiences increased stress leading to performance degradation
Solution Approach 1:
The switching function is segmented between two parallel transistors controlled by different PWM signals, distributing the electrical stress and reducing performance degradation
Solution Approach 2:
The controller alternates between the first and second transistors using periodic PWM signals, ensuring that each transistor operates during specific intervals to reduce cumulative stress and maintain reliability
3Device complexity
If the main transistor operates continuously without relief, then the control circuit is simple, but the on resistance increases significantly reducing efficiency
Solution Approach 1:
The controller implements periodic switching between the first and second transistors using PWM signals, providing regular relief to each transistor and maintaining low on-resistance for high efficiency
Solution Approach 2:
The controller receives feedback from the switching terminal and adjusts the PWM signals to optimize the operation of both transistors, ensuring efficient switching and minimizing energy losses
Data Source
AI summary
A circuit includes a first transistor, a second transistor and a controller. The first transistor has a first terminal coupled to a switching terminal, a second terminal coupled to a reference terminal, and a control terminal. The first transistor is a gallium nitride transistor. The second transistor has a first terminal coupled to the switching terminal, a second terminal coupled to the reference terminal, and a control terminal. The controller has a first output coupled to the control terminal of the first transistor, and a second output coupled to the control terminal of the second transistor.