Isolated Synchronous Rectifying DC/DC Converter Source Open Detection
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Solution Overview
Problem
Isolated synchronous rectifying DC/DC converters face challenges in accurately detecting source open abnormalities, which can lead to unstable voltage conditions and potential damage to synchronous rectification transistors due to parasitic impedance and avalanche breakdown.
Innovation Solution
The implementation of a synchronous rectification controller with a source open abnormality detection circuit, including a comparator and flip-flop configuration, that compares the source terminal voltage with a detection threshold and outputs an abnormality detection signal to control the synchronous rectification transistor, preventing damage by turning it off when an abnormality is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a synchronous rectification controller is used to control switching of the synchronous rectification transistor, then rectification efficiency is improved, but the risk of source open abnormalities and transistor damage increases
Solution Approach 1:
The patent applies preliminary action by detecting source open abnormalities before they cause transistor damage. The abnormality detection circuit continuously monitors the source terminal voltage and compares it with a reference voltage to detect open conditions early, allowing the controller to take preventive action (stopping switching signals) before reverse current or avalanche breakdown can damage the transistor.
Solution Approach 2:
The patent implements feedback through the abnormality detection circuit that continuously monitors the source terminal voltage and feeds back abnormality detection signals to the synchronous rectification controller. This feedback mechanism enables real-time monitoring and automatic protection by comparing the source voltage with reference voltage and adjusting control signals accordingly to prevent transistor damage.
2Stability of the object's composition
If parasitic impedance is present in the source terminal connection, then voltage instability occurs, but adding protection circuits increases circuit complexity
Solution Approach 1:
The patent extracts the abnormality detection function as a separate, dedicated circuit module within the synchronous rectification controller. By taking out the detection functionality from the main control logic and implementing it as an independent abnormality detection circuit with comparator and signal processing elements, the patent addresses voltage instability caused by parasitic impedance while minimizing impact on overall control circuit complexity.
Solution Approach 2:
The patent introduces an intermediary abnormality detection circuit that mediates between the source terminal and the main control system. This intermediary circuit includes voltage comparison and signal processing elements that isolate the main controller from direct exposure to voltage instability caused by parasitic impedance, providing clean abnormality detection signals while maintaining system stability.
3Measurement precision
If the source terminal voltage fluctuates due to parasitic impedance, then abnormality detection accuracy decreases, but increasing detection sensitivity may cause false positives
Solution Approach 1:
The patent applies dynamics by implementing dynamic threshold adjustment and adaptive detection mechanisms. The abnormality detection circuit dynamically compares source terminal voltage with reference voltage and adjusts detection thresholds based on operating conditions. This dynamic approach allows accurate detection of true abnormalities while adapting to normal voltage fluctuations caused by parasitic impedance, thereby reducing false positives.
Solution Approach 2:
The patent changes detection parameters dynamically by adjusting voltage thresholds and comparison criteria based on operating conditions. The abnormality detection circuit monitors source terminal voltage and uses parameter changes in the reference voltage levels and detection thresholds to distinguish between normal fluctuations and true abnormalities, improving detection accuracy while minimizing false positives.
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 detects source open abnormalities, preventing reverse current flow and potential transistor damage, ensuring stable operation and extending the lifespan of the synchronous rectification transistors.
Implementation Method 1
the first comparator CP1 detects that the drain voltage VDS2 becomes equal to or lower than the first threshold voltage VthA... the second comparator CP2 detects zero current at which the current Is becomes substantially zero based on the drain voltage VDS2
Implementation Method 2
The synchronous rectification controller 300S outputs a gate signal GS from the gate terminal G10 based on a drain voltage VDS2 generated at the drain terminal D10 to control switching of the synchronous rectification transistor M200
Implementation Method 3
By the switching of the switching transistor on the primary side and the switching of the synchronous rectification transistor M200, an input voltage applied to the primary winding is converted to an output voltage and outputted from the output terminal
Data Source
AI summary
An isolated synchronous rectifying DC/DC converter includes a drain terminal connected to a drain of a synchronous rectification transistor, a source terminal connected to a source of the synchronous rectification transistor; a comparator configured to compare a drain voltage of the drain terminal with a predetermined threshold voltage which set is based on a potential of the source terminal, a first flip-flop to which an OFF signal output from the comparator is input, a driver configured to output a gate signal to the synchronous rectification transistor based on an output signal of the first flip-flop, and a first abnormality detection circuit including an abnormality detection comparator configured to compare a voltage of the source terminal with a detection threshold voltage, and configured to output a first abnormality detection signal based on an output of the abnormality detection comparator.