Flyback Power Supply Output Short Circuit Detection Method
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Solution Overview
Problem
Conventional flyback power supplies take tens to hundreds of milliseconds to detect output short circuits, leading to high power consumption and overheating due to delayed activation of protection mechanisms.
Innovation Solution
A method that detects the peak and initial current values in a power switch during a cycle and the next cycle, identifying output short circuits by monitoring the difference between these values, allowing for immediate detection within a few switching cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional detection methods using feedback pin COMP or power pin VDD are used, then the power management IC can detect output short circuit, but the detection time is long (tens to hundreds of milliseconds) causing high power consumption and overheating
Solution Approach 1:
The patent performs preliminary action by detecting the initial value of the current signal at the beginning of each switching cycle, before the short circuit condition fully develops. This allows the system to identify abnormal current trends early in the cycle, enabling detection within microseconds rather than waiting tens to hundreds of milliseconds as in conventional methods.
Solution Approach 2:
The patent implements continuous feedback by monitoring the current signal through the current sense pin during each switching cycle, comparing the initial value with the peak value, and immediately triggering protection when the difference exceeds the threshold. This real-time feedback mechanism eliminates the delayed detection inherent in conventional methods that only check at specific pins after the cycle completes.
2Reliability
If conventional detection methods are used, then the power management IC can identify output short circuit, but the delayed response causes large current to blowout and induces considerable power consumption
Solution Approach 1:
The patent implements continuous feedback by monitoring the current signal through the current sense pin during each switching cycle, comparing the initial value with the peak value, and immediately triggering protection when the difference exceeds the threshold. This real-time feedback mechanism eliminates the delayed detection inherent in conventional methods that only check at specific pins after the cycle completes.
Solution Approach 2:
The patent rushes through the detection process by performing the critical comparison between initial and peak current values within the same switching cycle, rather than waiting for multiple cycles or external pin readings. This allows the system to skip the lengthy detection delay and immediately activate protection when a short circuit is detected, reducing energy waste from prolonged high-current states.
3Reliability
If conventional detection methods are used, then the power management IC can detect output short circuit, but the delayed detection causes the flyback power supply to overheat
Solution Approach 1:
The patent performs preliminary action by detecting the initial value of the current signal at the beginning of each switching cycle, before the short circuit condition fully develops. This allows the system to identify abnormal current trends early in the cycle, enabling detection within microseconds rather than waiting tens to hundreds of milliseconds as in conventional methods.
Data Source
AI summary
Disclosed are methods of detection for output short circuit of a flyback power supply, which detect the current sense signal provided by a current sense resistor serially connected to a power switch of the flyback power supply, and thus quickly identify whether or not the flyback power supply suffers output short circuit.