Synchronous Rectification Controller Without Auxiliary Winding Loss
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Solution Overview
Problem
Traditional diode rectification in flyback switching power supplies results in low efficiency due to a large forward voltage drop, while methods using auxiliary windings or self-supply increase transformer size and cost, and methods without auxiliary windings suffer from significant energy loss.
Innovation Solution
A synchronous rectification controller utilizing a power switch transistor, drive circuit, and switch circuit with integrated NMOS transistors, which controls the on/off states of these transistors to efficiently transfer energy between capacitors, reducing system volume and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional diode rectification is used, then the structure is simple, but the conversion efficiency is low due to large forward voltage drop
Solution Approach 1:
The patent replaces the mechanical diode rectification system with an electronic synchronous rectification system using MOS transistors. The controller integrates power switch transistors that can be dynamically controlled to replace the passive diode, eliminating the large forward voltage drop and improving conversion efficiency while maintaining reasonable structural complexity through integration.
Solution Approach 2:
The patent changes the key parameter of the rectification element from a fixed diode with high forward voltage drop to a controllable MOS transistor with variable on-resistance. By dynamically adjusting the gate voltage of the MOS transistor, the resistance can be minimized during conduction, significantly reducing power loss and improving efficiency.
2Reliability
If auxiliary winding is added for power supply, then the controller can be powered, but the transformer size increases and integration level decreases
Solution Approach 1:
The patent makes the existing windings serve multiple functions. The primary and secondary windings not only perform power transfer but also enable power supply to the controller through the integrated power switch transistors. This eliminates the need for a dedicated auxiliary winding, maintaining power supply capability while reducing transformer size and improving integration.
Solution Approach 2:
The patent extracts the power supply function from a separate auxiliary winding and integrates it into the existing power transfer windings through the controller's power switch transistors. This removes the unnecessary auxiliary winding, reducing transformer complexity and size while maintaining the ability to power the controller.
3Volume of stationary object
If self-power supply method is used without auxiliary winding, then transformer size is reduced, but energy loss increases significantly
Solution Approach 1:
The patent replaces the lossy self-power supply method with an integrated synchronous rectification system. The power switch transistors in the controller are used to efficiently transfer and regulate energy from the transformer windings to power the controller, replacing the inefficient energy transfer path and significantly reducing energy loss while maintaining compact transformer size.
4Object-affected harmful factors
If high-side synchronous rectification is used, then EMI performance is improved, but the power supply complexity increases
Solution Approach 1:
The patent merges the power supply function with the high-side synchronous rectification function in a single integrated controller. The power switch transistors serve both to provide high-side rectification for improved EMI performance and to enable efficient power supply to the controller, eliminating the need for separate power supply circuitry and reducing overall complexity.
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 improves energy conversion efficiency and reduces application volume and cost by integrating high-voltage power supply switch transistors on a silicon slice, enabling efficient power supply and sampling of output voltage.
Implementation Method 1
When QSW1 is turned off and QR1 is turned on, the energy is induced to a secondary side winding NS1 and an auxiliary winding Naux through winding mutual inductance of the transformer T1
Data Source
AI summary
A synchronous rectification controller and a switching power supply are provided. The synchronous rectification controller includes: a power switch transistor, a drive circuit, a power supply control circuit, and a switch circuit including a plurality of power supply switch transistors; wherein the drive circuit is configured to control an on or off state of the power switch transistor, to make the synchronous rectification controller perform synchronous rectification or stop synchronous rectification; and the power supply control circuit is configured to control an on or off state of each power supply switch transistor in the switch circuit. With embodiments of the present disclosure, energy conversion efficiency may be improved to realize efficient power supply.