Switching Power Source Feedback via Auxiliary Windings
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Solution Overview
Problem
Conventional insulation type switching power source apparatuses face issues with long-term reliability and cost due to the use of photocouplers for output feedback control, and the accuracy of output feedback control in systems without photocouplers is not optimal.
Innovation Solution
An insulation type switching power source apparatus that uses a transformer with primary and secondary windings, along with auxiliary windings, and incorporates a sample/hold circuit and primary current control circuit to perform accurate output feedback control without photocouplers, allowing for efficient switching control and reduced component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a photocoupler is used for output feedback control, then insulation between primary and secondary circuit systems is maintained, but long-term reliability deteriorates and cost increases due to increase in the number of components
Solution Approach 1:
The patent extracts and removes the photocoupler from the feedback control system. Instead of using a photocoupler to transmit feedback signals across the insulation barrier, the invention uses only the auxiliary winding of the transformer to generate feedback voltages that are processed entirely on the primary side, eliminating the need for optical coupling components and improving reliability while reducing component count.
Solution Approach 2:
The auxiliary winding of the transformer is given multiple functions: it serves both as part of the power transformation system and as the sole source for generating feedback voltages for output control. This multi-functionality eliminates the need for separate photocoupler-based feedback pathways, reducing component complexity while maintaining insulation integrity.
2Reliability
If a photocoupler is used for output feedback control, then insulation between primary and secondary circuit systems is maintained, but cost increases due to increase in the number of components
Solution Approach 1:
The photocoupler is extracted from the system, eliminating its associated cost. The feedback control function is achieved entirely through the transformer's auxiliary winding and primary-side circuitry, reducing component count and manufacturing cost while maintaining the necessary insulation through the transformer's inherent magnetic coupling.
3Device complexity
If an auxiliary winding or primary winding is used for output feedback control without a photocoupler, then component count is reduced, but accuracy of the output feedback control is insufficient
Solution Approach 1:
The feedback control is segmented into multiple discrete voltage generation stages using the auxiliary winding. Different feedback voltages are generated at different operational phases (switching on, switching off, etc.), and these segmented voltage signals are processed through dedicated circuits to achieve high-precision control without requiring a photocoupler.
Solution Approach 2:
The auxiliary winding generates feedback voltages in advance during specific switching phases before they are needed for control decisions. By preliminarily generating these voltage signals during the switching cycle, the system achieves accurate real-time feedback control without relying on external optical coupling components.
4Reliability
If the primary winding is continuously driven, then output voltage stability is maintained, but efficiency decreases during light load states due to unnecessary switching operations
Solution Approach 1:
The switching control operates periodically rather than continuously, especially during light load conditions. The controller activates the primary winding only when needed based on feedback voltage levels, creating periodic switching action that maintains output stability while reducing energy waste during light load states by allowing idle periods between switching cycles.
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 provides highly accurate output feedback control, reduces component costs, and improves reliability by using auxiliary windings for feedback control, while maintaining efficiency and accuracy in both constant voltage and constant current modes.
Implementation Method 1
a transformer that insulates a primary circuit system and a secondary circuit system from each other and uses a primary winding and a secondary winding to transform an input voltage into an output voltage
Implementation Method 2
the output monitor device drives the second auxiliary winding to generate an induced voltage in the first auxiliary winding
Data Source
AI summary
A power source apparatus comprises: a transformer that insulates a primary system and a secondary system and uses primary/secondary windings to transform an input voltage into an output voltage; a switching control device that is disposed in the primary system to drive the primary winding, and an output monitor device that is disposed in the secondary system to monitor the output voltage. The transformer includes a first auxiliary winding disposed in the primary system and a second auxiliary winding disposed in the secondary system. The output monitor device drives the second auxiliary winding to generate an induced voltage in the first auxiliary winding when the output voltage becomes smaller than a predetermined threshold voltage. The switching control device temporarily stops driving of the first winding upon detecting a light load state and resumes the driving of the first winding upon detecting the induced voltage in the first auxiliary winding.