Flyback Switching Power Supply Control for Optocoupler-Free ZVS
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Solution Overview
Problem
Existing flyback AC-DC isolated switching power supplies face challenges with high primary switching losses, low efficiency, severe electromagnetic interference (EMI), complex circuit structures, and slow control loop response speeds, which hinder miniaturization and compatibility with fast charging protocols.
Innovation Solution
A switching power supply control method that simplifies the circuit structure by eliminating optocouplers and additional control loops, achieving zero-voltage switching (ZVS) through secondary side feedback control, reducing switching losses, and improving EMI characteristics, while supporting fast charging protocols with enhanced control loop response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If active clamp flyback design is used to achieve zero voltage switching, then switching losses are reduced, but circuit structure becomes complex with higher hardware costs
Solution Approach 1:
The patent extracts and eliminates the active clamp circuit from the flyback power supply design, achieving zero voltage switching through a simplified control method that monitors voltage waveforms and adjusts switching timing, thereby reducing circuit complexity while maintaining low switching losses
Solution Approach 2:
The patent implements feedback control by monitoring the voltage waveform at the first connection point and using this information to control the turn-on timing of the primary switching transistor, achieving zero voltage switching without complex additional circuits
2Reliability
If optocoupler is used for primary and secondary side control, then control is achieved, but structure complexity increases and reliability decreases
Solution Approach 1:
The patent removes the optocoupler from the control circuitry and implements a primary-side-only control architecture that uses voltage waveform monitoring and timing control to achieve both regulation and feedback functions, thereby simplifying the structure and improving reliability
Solution Approach 2:
The patent makes the primary control module perform multiple functions including voltage regulation, feedback control, and synchronization by monitoring the voltage waveform and adjusting switching timing, eliminating the need for separate optocoupler-based feedback circuits
3Speed
If primary side regulation feedback control is used to eliminate optocouplers, then structure is simplified, but control loop response speed becomes slow
Solution Approach 1:
The patent uses preliminary detection of the voltage waveform at the first connection point to predict when zero voltage will occur, allowing the control module to prepare and execute switching actions in advance, thereby achieving fast response without complex feedback circuits
Solution Approach 2:
The patent replaces the traditional optocoupler-based feedback mechanism with an electronic voltage waveform monitoring and timing control system that operates entirely on the primary side, achieving faster response speeds through direct electronic control rather than optical coupling
4Volume of moving object
If switching frequency is increased for miniaturization, then power supply size is reduced, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent implements dynamic control of the switching timing by continuously monitoring the voltage waveform and adjusting the turn-on moment to achieve zero voltage switching, allowing high switching frequencies to be used without incurring high switching losses, thus enabling miniaturization while maintaining efficiency
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 reduces hardware costs, simplifies the circuit structure, decreases switching losses, and enhances EMI performance, enabling faster control loop responses and broader compatibility with various charging protocols.
Implementation Method 1
The primary winding is configured to store energy in the case where the first switching transistor is turned on
Implementation Method 2
The secondary winding is configured to generate the output voltage in the case where the second switching transistor is turned on
Data Source
AI summary
A switching power supply control method includes the following: after the high-voltage startup of the switching power supply, the secondary control module adjusts the cut-off current of the second switching transistor according to a voltage waveform at a second connection point until a voltage waveform at a first connection point just reaches zero, the primary control module controls the first switching transistor to be turned on; the primary control module adjusts the peak current of the first switching transistor until the peak current of the first switching transistor reaches a preset value, the primary control module controls the first switching transistor to be turned off; the secondary control module controls the second switching transistor to be turned on; and in case where the switching current of the second switching transistor is at a current zero-crossing point, the secondary control module controls the second switching transistor to be turned off.