Flyback Current Detection Circuit With Mirrored Capacitor Path
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Solution Overview
Problem
Existing flyback voltage converters face challenges in accurately controlling current flow through the primary coil of the transformer, leading to inefficiencies in power conversion and increased component costs and circuit area.
Innovation Solution
The proposed solution involves mirroring a small current path in parallel to a large current path within the current detection circuit, using a second capacitor and a current detection resistor in parallel with a first capacitor, to reduce power loss, component costs, and circuit area while maintaining current detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection resistor is used to detect current flowing through the primary coil of the transformer, then current detection accuracy is achieved, but power loss increases and component costs increase
Solution Approach 1:
The patent creates a parallel current path with a second capacitor and current detection resistor that mirrors a portion of the main current flow. This copying approach allows detection of current characteristics without forcing the entire current through the detection resistor, thereby reducing power loss while maintaining detection accuracy through proportional measurement.
Solution Approach 2:
The current detection function is segmented into two parallel paths: the main current path through the first capacitor and a detection path through the second capacitor and current detection resistor. This segmentation allows the detection resistor to handle only a portion of the total current, reducing power loss while still providing accurate current detection through the proportional relationship between the paths.
2Measurement precision
If a current detection resistor is used to detect current flowing through the primary coil of the transformer, then current detection accuracy is achieved, but circuit area increases
Solution Approach 1:
The detection path is designed as a scaled-down copy of the main current path, using a second capacitor with different capacitance value to create a proportional current relationship. This allows accurate current detection through the smaller detection path components, reducing the overall circuit area required compared to forcing all current through a large detection resistor.
3Ease of operation
If conventional current detection methods are used in flyback voltage converters, then current control is achieved, but conversion efficiency decreases
Solution Approach 1:
The patent implements a copied current detection path that provides accurate current control information to the controller while minimizing energy loss. The proportional current relationship between the first and second capacitors allows the controller to accurately control the primary coil current based on the voltage across the current detection resistor, without requiring the full current to pass through the detection resistor, thus maintaining high conversion 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
This approach significantly reduces power loss caused by current detection resistors, lowers component costs and circuit area, and maintains accurate current detection, thereby enhancing the overall efficiency of the flyback voltage converter.
Implementation Method 1
a current detection resistor coupled between the second capacitor and a ground... the power converter acknowledges a current flowing through the transformer and the first capacitor based on a voltage across the current detection resistor
Implementation Method 2
The transformer comprises a primary coil, and the primary coil is coupled between the switching node and a first node... the transformer comprises a first secondary coil
Implementation Method 3
The first capacitor is coupled between the first node and the ground... a second capacitor and a current detection resistor... a first ratio of the first current to the second current is equal to a second ratio of the first capacitor to the second capacitor
Data Source
AI summary
A power converter includes a high-side transistor, a low-side transistor, a transformer, a first capacitor, a current detection circuit, a second capacitor, and a current detection resistor. The high-side transistor is coupled between an input voltage and a switching node. The low-side transistor is coupled between the switching node and a ground. The transformer includes a primary coil, and is coupled between the switching node and a first node. The first capacitor is coupled between the first node and the ground. The current detection circuit is connected in parallel with the first capacitor, and includes a second capacitor and a current detection resistor. The second capacitor is coupled to the first node. The current detection resistor is coupled between the second capacitor and the ground.