Flyback Converter Secondary Side Control Optical Coupler Removal
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Solution Overview
Problem
Conventional flyback converters face issues with stability and durability due to the physical characteristics of optical couplers, requiring additional components that increase cost and space, and secondary side control designs complicate the control IC fabrication process.
Innovation Solution
A flyback converter with secondary side control that replaces the optical coupler with a rectifier switching device and an output capacitor, using a secondary side control circuit to detect voltage and current variations and control the rectifier switching device, and an auxiliary winding to provide power and detect states, allowing for multi-mode operation and supporting USB rapid charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical coupler is used for feedback control, then the output voltage can be regulated, but the system stability and durability are affected and additional components are required
Solution Approach 1:
The patent removes the optical coupler from the feedback control path and extracts its function by using the auxiliary winding to directly sense the output voltage and feed back to the primary side controller, eliminating the reliability issues associated with optical coupler aging and coupling efficiency degradation
Solution Approach 2:
The auxiliary winding acts as an intermediary element that transfers output voltage information from the secondary side to the primary side through magnetic coupling, replacing the optical coupler's function while providing more stable and durable signal transmission
2Measurement precision
If an optical coupler is used for feedback control, then the output voltage can be regulated, but extra electric components are required increasing cost and space
Solution Approach 1:
The optical coupler and associated components are removed from the circuit. The feedback function is achieved using only the auxiliary winding and existing primary side control circuitry, reducing component count and system complexity
Solution Approach 2:
The auxiliary winding serves multiple functions: providing feedback signal for voltage regulation, generating auxiliary power supply voltage, and enabling communication between primary and secondary sides, replacing multiple separate components
3Reliability
If secondary side control is implemented, then better regulation is achieved, but the control IC fabrication process is complicated
Solution Approach 1:
Instead of controlling the switching device from the secondary side, the patent inverts the control direction by having the primary side controller regulate the switching device based on feedback from the auxiliary winding, simplifying the fabrication process while maintaining regulation performance
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 design simplifies the circuit by removing the optical coupler, reduces costs, provides precise control for USB rapid charging, and optimizes power converting efficiency through multi-mode control, enhancing stability and reducing component complexity.
Implementation Method 1
an auxiliary winding coupled to the secondary winding and configured to provide power and to detect the states of the secondary side rectifier switching device
Implementation Method 2
a transformer having a primary winding and a secondary winding
Data Source
AI summary
A flyback converter with a secondary side control includes a transformer having a primary winding and a secondary winding, a rectifier switching device in the secondary side configured to provide a rectifier path and a switching path, a secondary side control circuit configured to detect the output voltage or current value and to control the states of the rectifier switching device according to the variations between the pre-set voltage or current value and the output voltage or current value, a primary side switching device in the primary side configured to switch between on and off states, an auxiliary winding coupled to the secondary winding for providing power and detecting the states of the secondary side rectifier switching device, and a primary control circuit configured to control the primary side switching device based on the detected output state of the secondary winding from the auxiliary winding.