Flyback Controller Leakage Current Protection
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Solution Overview
Problem
Flyback power converters face issues with diode leakage current, leading to increased temperature and potential burning of the diode or adapter, as existing solutions like over-temperature protection and specific diodes increase costs without being effective choices for designers.
Innovation Solution
A controller with leakage current protection that includes a comparison unit, reference voltage generation unit, time out signal generation unit, and gate signal generation unit, which outputs selection signals and reference voltage ranges to determine time outs and enter leakage current protection or quasi-resonant modes based on compensation voltage and voltage peaks, allowing for quick activation of protection without additional costly circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If over-temperature protection is implemented to prevent diode burning, then reliability is improved, but device complexity and cost increase due to additional circuits
Solution Approach 1:
The system uses its own existing voltage detection circuitry to monitor the auxiliary winding voltage peaks and detect diode leakage current conditions. No external or additional protection circuits are needed - the controller repurposes its inherent measurement capabilities to detect the leakage condition and activate protection mode, making the system self-protecting without adding complexity
Solution Approach 2:
The voltage detection circuit, originally designed for normal operation monitoring, is made multi-functional by also detecting diode leakage current conditions through analysis of voltage peak attenuation characteristics. This allows the same circuit to serve both normal control functions and protection functions, eliminating the need for separate protection circuits
2Reliability
If specific diodes are used to prevent leakage current issues, then reliability is improved, but cost increases
Solution Approach 1:
Instead of changing the diode component itself, the system changes the operational parameters by detecting voltage peak attenuation characteristics and dynamically adjusting the power switch timing. When leakage is detected, the controller enters a protection mode that prevents further damage, allowing standard diodes to be used without requiring expensive specialized components
3Reliability
If traditional over-temperature protection is used, then diode burning is prevented, but the protection response is slow and cost increases
Solution Approach 1:
The system performs preliminary detection of diode health by continuously monitoring the attenuation characteristics of voltage peaks during normal operation. This early detection occurs before temperature reaches dangerous levels, allowing the controller to preemptively enter protection mode and prevent damage before it occurs, rather than reacting after overheating is detected
4Reliability
If the diode is monitored for leakage current, then reliability is improved, but the detection and control complexity increases
Solution Approach 1:
The system implements feedback by monitoring the attenuation of voltage peaks from the auxiliary winding and using this information to detect diode leakage current. The detected condition feeds back to the controller, which automatically adjusts the power switch timing to enter protection mode, creating a closed-loop system that uses simple voltage measurements to trigger protective action without complex control logic
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
The solution enables cost-effective and rapid entry into leakage current protection, preventing diode overheating and adapter damage while maintaining efficient operation, thus addressing the cost and effectiveness issues of prior art.
Implementation Method 1
The comparison unit is used for receiving a compensation voltage, and outputting a corresponding selection signal according to the compensation voltage and a threshold
Implementation Method 2
The reference voltage generation unit is used for outputting a corresponding reference voltage range according to the corresponding selection signal
Implementation Method 3
the time out signal generation unit is used for determining a corresponding time out according to the corresponding selection signal, and generating a corresponding time out signal when a voltage corresponding to an auxiliary winding of the power converter has no peak to cross an upper limit of the corresponding reference voltage range during the corresponding time out
Implementation Method 4
a reverse bias is crossed on a diode coupled to a secondary side of the flyback power converter when a power switch of a primary side of the flyback power converter is turned on
Implementation Method 5
the flyback power converter stores energy and a reverse bias is crossed on a diode coupled to a secondary side of the flyback power converter when a power switch of a primary side of the flyback power converter is turned on
Implementation Method 6
the flyback power converter releases the energy to the secondary side of the flyback power converter and a forward bias is crossed on the diode when the power switch is turned off
Data Source
AI summary
A controller with leakage current protection of a diode includes a comparison unit, a reference voltage generation unit, a time out signal generation unit, and a gate signal generation unit, wherein the diode is applied to a secondary side of a power converter. The comparison unit outputs a corresponding selection signal according to a compensation voltage and a threshold. The reference voltage generation unit outputs a corresponding reference voltage range according to the corresponding selection signal. The time out signal generation unit determines a corresponding time out according to the corresponding selection signal, and generates a corresponding time out signal when a voltage corresponding to an auxiliary winding has no peak to cross an upper limit of the corresponding reference voltage range during the corresponding time out. The gate signal generation unit enters the leakage current protection or a quasi-resonant mode according to the corresponding time out signal.