Switch Drive Circuit for Full-Bridge Transformer Magnetic Deviation
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Solution Overview
Problem
Conventional switching power supply devices using a full-bridge output stage suffer from magnetic deviation of a transformer due to variations in switching device characteristics, which can lead to abnormal operation and failure in generating the desired output voltage.
Innovation Solution
A switch drive circuit that alternately switches between two cycles of excitation currents in different directions to the transformer, with simultaneous OFF times set based on the magnitude of the excitation currents in each cycle, allowing for operation mode switching to adjust dead times according to the average current or individual cycle currents, thereby moderating magnetic deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional full-bridge output stage is used with fixed switching parameters, then the circuit structure is simple, but magnetic deviation of transformer occurs due to variation in switching device characteristics
Solution Approach 1:
The patent applies dynamics by making the simultaneous OFF time (dead time) of the full-bridge output stage variable rather than fixed. The control circuit dynamically adjusts the dead time based on detected excitation current magnitudes from both cycles, allowing the switching parameters to adapt to variations in switching device characteristics and prevent magnetic deviation of the transformer.
Solution Approach 2:
The patent implements feedback by using detection circuits to measure the excitation current magnitudes in both cycles, then feeding this information back to the control circuit. The control circuit uses this feedback to automatically adjust the simultaneous OFF time, creating a closed-loop control system that compensates for switching device variations and maintains transformer magnetic balance.
2Reliability
If simultaneous OFF time is adjusted based on excitation current magnitude, then magnetic deviation is reduced, but control complexity increases
Solution Approach 1:
The patent applies self-service by designing a control system that automatically adjusts the simultaneous OFF time based on detected excitation current magnitudes without requiring external manual intervention. The control circuit self-regulates the dead time by comparing current magnitudes from both cycles and making appropriate adjustments, reducing the need for complex external control mechanisms.
3Reliability
If dead time is set based on average excitation current, then magnetic deviation is moderated, but response to individual cycle variations is reduced
Solution Approach 1:
The patent applies dynamics by providing multiple operational modes for setting the simultaneous OFF time. The system can dynamically switch between using average excitation current from both cycles (for moderate magnetic deviation) and using excitation current from only one cycle (for faster response to variations). This dynamic mode switching allows the system to adapt its response characteristics based on operating conditions.
Data Source
AI summary
A switch drive circuit drives a full-bridge output stage connected to a transformer to alternately switch between a first cycle in which a current in a first direction is supplied to the transformer and a second cycle in which a current in a second direction is supplied to the transformer. The switch drive circuit includes a mode in which a dead time of the output stage is set in accordance with a magnitude of a current flown in one of the first and second cycles, the dead time becoming an operation changing factor in the other cycle. Or, the switch drive circuit includes a mode in which the dead time of the output stage is set in accordance with a magnitude of an average current obtained by averaging currents flown in the first and second cycles. Or, the switch drive circuit switches between these modes in accordance with a signal.