Flyback Power Source Synchronous Rectification Control Circuit
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Solution Overview
Problem
Conventional flyback system power source apparatuses have complex circuit configurations and a large number of parts, making it difficult to control synchronously rectifying elements efficiently, especially in synchronizing with primary side switching, and require additional components like current transformers or inductors for current polarity detection.
Innovation Solution
A flyback system power source apparatus that uses a synchronous rectification control circuit to detect voltage vibrations in the secondary winding of a transformer, allowing for operation control of the synchronously rectifying element without the need for additional transformers or inductors, by utilizing the parasitic leakage inductance and smoothing capacitor to generate detectable voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current transformer is used to detect current polarity for controlling the synchronously rectifying element, then the rectifying element can be controlled, but the circuit configuration becomes complicated and the number of parts increases
Solution Approach 1:
The patent extracts the detection function from a separate current transformer and integrates it into the existing synchronous rectifying element by utilizing its parasitic inductance. The control circuit detects voltage changes across the synchronous rectifying element itself, eliminating the need for an external current transformer and simplifying the overall circuit configuration.
Solution Approach 2:
The synchronous rectifying element is given dual functionality: it serves both as the rectifying switch and as the detection sensor for current polarity. By monitoring voltage changes across this single component, the circuit achieves both rectification and detection functions without requiring separate dedicated parts.
2Reliability
If a current transformer is used to detect current polarity, then the rectifying element can be controlled, but the mounting area increases due to the large number of parts
Solution Approach 1:
The patent merges the detection function with the synchronous rectifying element by utilizing its inherent parasitic inductance. This consolidation eliminates the need for separate detection components, thereby reducing the total component count and the mounting area required for the circuit.
3Device complexity
If the parasitic inductance of the synchronously rectifying element is used for detection, then the number of parts is reduced, but the inductance value becomes very small making detection difficult
Solution Approach 1:
The patent introduces a smoothing capacitor as an intermediary component that works in conjunction with the parasitic inductance to generate detectable voltage vibrations. This mediator amplifies the detection signal by creating resonant oscillations, making the voltage changes sufficiently large to be easily detected despite the small inductance value.
4Reliability
If an inductor is inserted in series with the synchronously rectifying element for detection, then current polarity can be detected, but the number of parts increases
Solution Approach 1:
The synchronous rectifying element serves itself by utilizing its own parasitic inductance for detection purposes. This self-service approach eliminates the need for external inductors or current transformers, as the element's inherent electrical characteristics are leveraged to perform the detection function.
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
This approach reduces the number of parts and mounting area, enabling precise control of the synchronously rectifying element in synchronization with primary side switching, leading to more efficient voltage output and reduced power consumption without increasing the circuit complexity.
Implementation Method 1
a synchronous rectification control circuit for detecting a voltage vibration caused in a terminal voltage of the secondary winding to perform operation control of the synchronously rectifying element on the basis of the detection
Data Source
AI summary
A flyback system power source apparatus, which applies a voltage intermittently to a primary winding of a transformer to perform voltage outputting onto a secondary winding side of the transformer, comprises: the transformer; a synchronously rectifying element for rectifying a current in a secondary winding of the transformer; and a synchronous rectification control circuit for detecting a voltage vibration caused in a terminal voltage of the secondary winding to perform operation control of the synchronously rectifying element on the basis of the detection.