Secondary-Side Fault Detection in Isolated Power Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Isolated switched-mode power converters face challenges in detecting primary-side fault conditions from the secondary side without introducing additional analog isolation circuitry, which increases cost, size, and introduces delay and noise.
Innovation Solution
The implementation of a secondary-side digital controller that senses a rectified voltage on the secondary side to detect primary-side fault conditions, using digital isolators for switch control signals and avoiding the need for additional analog isolation circuitry, allowing for quick detection of voltage anomalies indicative of primary-side faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary-side controller is used to detect fault conditions, then fault detection capability is improved, but additional analog isolators are required which increases cost, size, and introduces delay
Solution Approach 1:
The patent inverts the conventional approach by placing the controller on the secondary side instead of the primary side. This allows the controller to detect primary-side faults by monitoring the rectified voltage waveform that reflects primary-side conditions, eliminating the need for additional analog isolators while maintaining fault detection capability
Solution Approach 2:
The rectified voltage waveform serves as an intermediary that carries information about primary-side fault conditions to the secondary-side controller. By monitoring this intermediate signal, the controller can detect primary-side faults without direct electrical contact or additional isolation circuitry
2Reliability
If analog isolators are used to transfer output voltage and current information, then closed-loop control is maintained, but cost and size increase
Solution Approach 1:
The system uses the existing rectified voltage waveform, which is already present for power conversion purposes, to provide dual functionality by also serving as a fault detection signal. This self-service approach eliminates the need for separate analog isolators dedicated to fault detection
Solution Approach 2:
The rectified voltage waveform performs multiple functions: it provides the necessary signal for power conversion and simultaneously serves as a diagnostic signal for detecting primary-side faults. This multi-functionality reduces the need for additional dedicated circuitry
3Device complexity
If a secondary-side controller is used, then cost and size are reduced, but detection of primary-side faults becomes difficult
Solution Approach 1:
The system uses feedback from the rectified voltage waveform, which naturally reflects primary-side operating conditions, to enable the secondary-side controller to detect primary-side faults. The feedback mechanism allows indirect monitoring of primary-side conditions without additional hardware
4Reliability
If additional analog isolation circuitry is introduced, then isolation barrier integrity is maintained, but delay and noise are introduced
Solution Approach 1:
The system uses a copy of the primary-side voltage information that is already present in the rectified voltage waveform on the secondary side. By monitoring this existing copy rather than introducing additional isolation circuitry, the system avoids adding delay or noise while maintaining isolation barrier 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 rapid detection of primary-side faults with minimal delay and without the drawbacks of analog isolation, maintaining the integrity of the isolation barrier while reducing costs and size, and achieving performance comparable to solutions requiring dedicated analog isolators.
Implementation Method 1
Isolated switched-mode direct-current (DC) to DC power converters use a transformer to convert power from an input source into power for an output load
Implementation Method 2
AC power supplied on the secondary side of the transformer is rectified and filtered so as to provide DC power to the output load
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An isolated switched-mode power converter converts power from an input source into power for an output load. Power switches within a primary-side power stage control the amount of power input to the power converter and, ultimately, provided to the output load. A digital controller on the secondary side of the power converter generates signals to control the power switches. This controller also senses a rectified voltage on the secondary side of the power converter and uses this sensed voltage to detect fault conditions of the primary side. For example, the sensed rectified voltage is used to detect undervoltage or overvoltage conditions of the input power source of the power converter, or faulty power switches within the primary-side power stage.