Synchronous Flyback Converter Primary Current Detection
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Solution Overview
Problem
Synchronous flyback converter circuits face challenges in efficiently detecting and regulating the mean value of current on the secondary side for lighting systems, particularly at low dimming levels, due to galvanic isolation and noise interference, leading to increased complexity and cost.
Innovation Solution
The solution involves detecting the time average of the switch current on the primary side by separating the positive and negative components, allowing for the determination of the secondary-side current without the need for potential isolation and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mean value of secondary-side current is detected using traditional methods with galvanic isolation, then electrical isolation between primary and secondary sides is maintained, but device complexity and cost increase
Solution Approach 1:
The invention extracts the current detection function from the secondary side to the primary side by detecting the switch current flowing through the primary switch. This eliminates the need for separate secondary-side detection circuits and galvanic isolation components, as the switch current on the primary side contains information about the secondary-side current that can be processed to determine its mean value.
Solution Approach 2:
The primary switch serves multiple functions: it controls the primary-side current flow for energy storage in the transformer, and simultaneously acts as a sensing element whose current can be used to detect the secondary-side current characteristics. This multi-functionality reduces the need for separate detection components.
2Measurement precision
If the time average of switch current is detected on the primary side, then detection accuracy at low dimming levels improves, but noise interference increases
Solution Approach 1:
The invention segments the switch current into positive and negative components and processes them separately. By calculating the time average of the absolute value of the switch current, the method distinguishes between useful signal information and noise, improving measurement precision at low dimming levels while filtering out interfering noise components.
Solution Approach 2:
The control unit continuously monitors the switch current and uses feedback control to regulate the secondary-side current based on the detected mean value. This feedback mechanism allows the system to maintain accurate current regulation even at low dimming levels by adjusting the switching parameters to compensate for noise and maintain signal integrity.
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 enables cost-effective and space-efficient detection of the secondary-side current, improving the accuracy and reliability of current regulation even at low dimming levels, thereby enhancing the control of lighting systems.
Implementation Method 1
a transformer with a primary winding, which is electrically connected to the first switch, and with a secondary winding... the transformer galvanically isolates a primary side of the synchronous flyback converter circuit from a secondary side
Implementation Method 2
the detection circuit is set up to separately detect a time average of a positive component of the switch current flowing through the first switch and a time average of a negative component of the switch current flowing through the first switch
Data Source
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AI summary
The present invention relates to a synchronous flyback converter circuit (1) for operating an illuminant line (4) having at least one illuminant (5), more particularly having at least one light emitting diode, the synchronous flyback converter circuit (1) comprising: a transformer (T), having a primary winding (Np), which is electrically connected to a first switch (S1), and a secondary winding (Ns), which is electrically connected to an output (A1, A1') of the synchronous flyback converter circuit via a second switch (S2), the illuminant line (4) being able to be connected to the output; and a control unit (2), which is designed to control the first switch (S1) and the second switch (S2). According to a first embodiment according to the invention, the synchronous flyback converter circuit (1) comprises a sensing circuit (3), which is designed to capture a temporal mean of the switch current (IS1) flowing through the first switch (S1) and to feed at least one signal (Sg) conveying said temporal mean to the control unit (2), the control unit (2) being designed to separately determine, on the basis of the signal (Sg) fed from the sensing circuit (3), a temporal mean of the positive component of the switch current (IS1) flowing through the first switch (S1) and a temporal mean of the negative component of the switch current (IS1) flowing through the first switch (S1). According to a second embodiment according to the invention, the synchronous flyback converter circuit (1) comprises a sensing circuit (3), which is designed to separately capture a temporal mean of the positive component of the switch current (IS1) flowing through the first switch and a temporal mean of the negative component of the switch current (IS1) flowing through the first switch and to feed a first signal conveying the temporal mean of the negative component of the switch current (IS1) and a second signal conveying the temporal mean of the positive component of the switch current (IS1) to the control unit (2).