Isolated Synchronous Rectification DC/DC Converter Thermal Management
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Solution Overview
Problem
Flyback DC/DC converters experience heat generation issues due to intermittent operation modes, where circuit elements like synchronous rectification transistors and switching transistors generate heat during operation periods and experience temperature rises, with short stop periods exacerbating the issue.
Innovation Solution
An isolated synchronous rectification-type DC/DC converter is designed with an auxiliary power supply circuit that maintains a power supply voltage for protection circuits, allowing extended stop periods during intermittent operation, reducing heat generation by prolonging thermal relaxation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous rectification transistors and switching transistors operate in intermittent mode with short stop periods, then the converter can maintain output voltage stability, but heat generation increases and reliability deteriorates
Solution Approach 1:
The patent segments the power supply function into two independent power supply circuits: a first power supply circuit that supplies power during normal operation, and a second power supply circuit that supplies power during stop periods. This segmentation allows the protection circuit to remain operational during stop periods without requiring the main power supply to be active, thereby enabling longer stop periods and reduced heat generation while maintaining reliability.
Solution Approach 2:
The patent implements preliminary action by providing a second power supply circuit that is prepared in advance to take over when the first power supply circuit is stopped. This ensures that the protection circuit can continue functioning during stop periods, allowing the converter to enter and maintain stop mode for extended thermal relaxation without compromising protection capabilities.
2Temperature
If the converter operates with extended stop periods to reduce heat generation, then temperature rises are suppressed, but output voltage stability may deteriorate
Solution Approach 1:
The patent implements periodic action through controlled intermittent operation where the converter alternates between operation mode and stop mode. The second power supply circuit enables the protection circuit to remain active during stop periods, allowing the system to safely extend the duration of stop modes for thermal management while maintaining output voltage stability through periodic resumption of normal operation when thermal conditions permit.
3Reliability
If protection circuits remain active during stop periods to maintain reliability, then converter protection is ensured, but power consumption increases
Solution Approach 1:
The patent segments the power supply function into two independent power supply circuits: a first power supply circuit that supplies power during normal operation, and a second power supply circuit that supplies power during stop periods. This segmentation allows the protection circuit to remain operational during stop periods without requiring the main power supply to be active, thereby enabling longer stop periods and reduced heat generation while maintaining reliability.
Solution Approach 2:
The second power supply circuit is configured to automatically activate and supply power to the protection circuit during stop periods when the first power supply circuit is inactive. This self-service mechanism ensures continuous protection functionality without requiring external intervention or increasing overall power consumption, as the second power supply utilizes available energy resources during stop modes.
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 solution effectively suppresses heat generation and enhances reliability by maintaining the power supply voltage for protection circuits, allowing longer stop periods and reducing temperature rises in circuit elements during intermittent operation modes.
Implementation Method 1
an auxiliary power supply circuit which includes a power supply capacitor provided separately from the output capacitor and supplies a power supply voltage generated in the power supply capacitor to the protection circuit
Data Source
AI summary
A secondary controller drives a light emitting element of a photocoupler such that a detection voltage VOUTS corresponding to an output voltage VOUT generated in an output capacitor C approximates to a reference voltage VREF. A primary controller controls a switching transistor M according to a feedback signal VFB. A protection circuit is activated and drives the light emitting element of the photocoupler when detecting an abnormal state. An auxiliary power supply circuit includes a power supply capacitor C provided separately from the output capacitor C and supplies a power supply voltage VCC to the protection circuit and an anode of the light emitting element of the photocoupler.