Flyback Switching Power Supply Tertiary Winding Load Detection
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Solution Overview
Problem
Flyback type switching power supplies face challenges in detecting sudden load changes without direct secondary side voltage detection, leading to transient output voltage drops during low or no load conditions, resulting in inefficiencies and increased power consumption.
Innovation Solution
Incorporating a sudden load change detector circuit that utilizes a tertiary winding voltage and a differentiating circuit with minimal power consumption to detect transient output voltage fluctuations, enabling immediate switching control of the semiconductor switch even when it's off, thus suppressing output voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photo-coupler based voltage detector circuit is used to directly detect secondary side voltage, then output voltage detection precision is improved, but power loss increases
Solution Approach 1:
The patent uses a tertiary winding as an intermediary to transfer voltage information from the secondary side to the primary side without direct electrical connection. The tertiary winding induces a voltage proportional to the secondary voltage through electromagnetic coupling, allowing detection without direct secondary side measurement and avoiding the power loss associated with photo-coupler based detection circuits.
2Loss of energy
If switching frequency is reduced to save power during light load, then power consumption is reduced, but output voltage stability deteriorates
Solution Approach 1:
The patent implements a preliminary detection mechanism that monitors the tertiary winding voltage to detect sudden load changes before they cause significant output voltage drops. When a load change is detected, the system proactively adjusts the switching frequency to maintain output voltage stability, preventing the stability deterioration that would otherwise occur during light load conditions.
Solution Approach 2:
The patent establishes a feedback loop where the tertiary winding voltage is continuously monitored and used to control the switching frequency. This feedback mechanism ensures that when load conditions change, the system responds by adjusting the switching frequency to maintain output voltage stability, thus resolving the contradiction between power consumption and voltage stability during light load operation.
3Device complexity
If tertiary winding voltage detection is used instead of direct secondary detection, then device complexity is reduced, but response speed to sudden load changes deteriorates
Solution Approach 1:
The patent dynamically adjusts the switching frequency based on tertiary winding voltage detection to maintain fast response to load changes. By making the switching frequency variable rather than fixed, the system can respond quickly to sudden load changes detected through the tertiary winding, compensating for the indirect detection method and maintaining response speed despite the simpler detection circuitry.
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 reduces power consumption and prevents output voltage drops during sudden load changes by enabling timely detection and control of the output voltage, maintaining stability and efficiency.
Implementation Method 1
a transformer (6) having a primary winding (6-1), a secondary winding (6-2), and a tertiary winding (6-3)
Data Source
AI summary
A flyback type switching power supply includes between P and N of a direct current output a sudden load change detector circuit, which normally has no power consumption, that detects only a transient fluctuation of a direct current output voltage, and starts the switching of a primary side semiconductor switch when there is no load or a light load, even when the semiconductor switch is in an off state, thereby enabling the detection of the direct current output voltage in a tertiary winding, and suppressing a drop in the direct current output voltage.