Four-Terminal Flyback Controller with Shared Opto Feedback
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Solution Overview
Problem
Conventional secondary side constant voltage and constant current controller integrated circuits in flyback converters are costly and have complex topologies, necessitating a more economical and simplified solution for regulating output voltage and current in switch mode power supply circuits.
Innovation Solution
A low-cost integrated circuit with a secondary side constant voltage and constant current controller is developed, utilizing a four-terminal package with shared error current sinking for both voltage and current regulation, where the feedback terminal senses output voltage and also serves as a power supply terminal, and the sense terminal senses output current while acting as the power supply current return, reducing terminal count and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional secondary side constant voltage and constant current controller integrated circuits are used, then output voltage and current regulation is achieved, but cost and circuit complexity increase
Solution Approach 1:
The patent combines the constant voltage controller and constant current controller into a single integrated circuit device. The CV controller and CC controller are merged on the same secondary side, sharing common components such as the optocoupler and feedback terminal, thereby reducing overall system complexity and component count while maintaining dual regulation functionality
Solution Approach 2:
The feedback terminal serves multiple functions: it provides feedback for voltage regulation, provides feedback for current regulation, and serves as a power supply terminal for the integrated circuit. This multi-functionality reduces the number of required terminals and simplifies the overall circuit topology
2Reliability
If conventional secondary side controller with separate terminals is used, then regulation functions are independent, but terminal count and package complexity increase
Solution Approach 1:
The feedback terminal is designed to serve multiple purposes simultaneously: it accepts feedback signals for both voltage and current regulation while also providing power supply connection. This multi-functional design reduces the terminal count from the conventional high number to just four terminals, simplifying the package without compromising independent regulation capabilities
Solution Approach 2:
The patent merges the functions of multiple terminals into fewer terminals. The feedback terminal combines feedback reception and power supply functions, while the integrated circuit internally manages separate regulation pathways for voltage and current, achieving terminal reduction while maintaining functional independence
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 solution effectively regulates output voltage and current in flyback converters, reducing costs and complexity while maintaining efficient operation in both constant voltage and constant current modes, with minimal error contribution from bias current and adaptable to various power supply applications.
Implementation Method 1
a corresponding current 26 to flow to the primary side controller 16 through the optocoupler 17
Data Source
AI summary
A low-cost integrated circuit is used as a secondary side constant voltage and constant current controller. The integrated circuit has four terminals and two amplifier circuits. A first amplifier circuit is used to sense a voltage on a FB terminal and in response to cause a first current to flow through an OPTO terminal. A second amplifier circuit is used to sense a voltage between a SENSE terminal and a SOURCE terminal and in response to cause a second current to flow through the same OPTO terminal. The FB terminal is used for output voltage feedback and is also used to supply power onto the integrated circuit. The SOURCE terminal is used for output current feedback and is also used as power supply return for the integrated circuit. The cost of the integrated circuit is reduced by having only four terminals.