Isolation Capacitor Fault Detection in Non-Earthed Power Supplies
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power supply systems in non-earthed electrical devices face challenges in detecting and preventing high voltage spikes that can expose users to dangerous peak voltages, particularly when transformers fail, without the need for protective earth or non-conductive materials, which add cost and complexity.
Innovation Solution
A power supply system with built-in fault detection using a transformer with galvanic isolation, an isolation capacitor, and fault circuitry to detect a switching pattern propagated through a short circuit between the primary and secondary sides, enabling immediate shutdown of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective earth is added to the chassis, then safety against peak voltage is improved, but device complexity and installation complexity increase
Solution Approach 1:
The fault detection circuitry continuously monitors for short circuits between primary and secondary windings before a fault can cause dangerous peak voltages. The isolation capacitor is pre-configured to detect switching patterns that indicate transformer failures, enabling preventive shutdown before the chassis becomes hazardous.
Solution Approach 2:
The isolation capacitor serves as an intermediary element that couples the primary and secondary sides of the transformer. It enables the fault detection circuitry to sense switching patterns from the primary side through the capacitor, providing a mechanism to detect transformer failures without direct electrical connection or protective earth.
2Reliability
If protective earth is added to the chassis, then safety against peak voltage is improved, but installation complexity increases
Solution Approach 1:
The system performs preliminary fault detection through the isolation capacitor before a transformer failure can create a safety hazard. By continuously monitoring for abnormal switching patterns, the system prevents peak voltages from reaching the chassis, eliminating the need for protective earth installation.
Solution Approach 2:
The fault detection system is self-contained within the power supply circuitry, using the existing isolation capacitor and switching elements to monitor for failures. The system automatically detects and responds to transformer faults without requiring external protective earth connections or additional installation infrastructure.
3Reliability
If the chassis is covered with plastic or non-conductive material, then safety against peak voltage is improved, but heat dissipation capability deteriorates
Solution Approach 1:
The fault detection circuitry using the isolation capacitor detects transformer failures before they can generate dangerous peak voltages that would require insulating barriers. By preventing the fault condition rather than isolating the chassis, the system maintains metal chassis with full heat dissipation capability.
Solution Approach 2:
The isolation capacitor, originally serving its standard function of blocking DC and allowing AC between primary and secondary sides, is utilized to detect fault conditions. This converts a routine circuit element into a safety mechanism, eliminating the need for protective covering while maintaining both safety and thermal performance.
4Reliability
If the chassis is covered with plastic or non-conductive material, then safety against peak voltage is improved, but product appearance and robustness deteriorate
Solution Approach 1:
The system continuously monitors for transformer failures through the isolation capacitor before peak voltages can reach the chassis. This preventive approach maintains the aesthetic and structural advantages of metal chassis while ensuring safety through early fault detection and shutdown.
Solution Approach 2:
The power supply system independently monitors its own health through the isolation capacitor and fault detection circuitry. The system self-protects against transformer failures without requiring external protective coverings, maintaining product appearance and robustness while ensuring safety.
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
Efficiently detects and prevents high voltage exposure by stopping operation upon fault detection, eliminating the need for protective earth or non-conductive materials, thus reducing costs and maintaining safety without additional complexity.
Implementation Method 1
an isolation capacitor connected between the secondary side of the transformer and the primary side of the transformer
Implementation Method 2
a transformer comprising a primary side and a secondary side, wherein the primary side and the secondary side are galvanically isolated
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The present disclosure relates to a power supply system with built-in fault detection comprising: a transformer comprising a primary side and a secondary side, wherein the primary side and the secondary side are galvanically isolated and wherein an input voltage is supplied to the primary side of the transformer; one or more switching elements connected to the primary side of the transformer; a controller configured to control switching of the one or more switching elements to control an output voltage on the secondary side of the transformer; an isolation capacitor connected between the secondary side of the transformer and the primary side of the transformer; fault circuitry connected to the isolation capacitor and configured to detect a switching pattern propagated through a short circuit between the primary side and secondary side of the transformer and further propagated through the isolation capacitor. The disclosure further relates to an electrical apparatus comprising the power supply system and to a method of handling faults in a non-earthed electrical apparatus.