High-Voltage Fusing Apparatus for EV PTC Heater Overheat Protection
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Solution Overview
Problem
High-voltage PTC heating circuits in electric vehicles are prone to overheating due to sticking contacts in the high-voltage relay, which can damage the PTC heater and cause vehicle combustion.
Innovation Solution
A high-voltage fusing apparatus comprising a current fuse, a temperature fuse, and a current-carrying fuse connected in series and parallel, with the current-carrying fuse having a lower resistance and fusing temperature, allowing for quick disconnection of the high-voltage circuit to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high-voltage relay is used to control the PTC heater circuit, then the heating control function is improved, but the contact sticking problem occurs causing the high-voltage circuit to fail disconnecting
Solution Approach 1:
The patent introduces a low-voltage control circuit as an intermediary between the temperature control switch and the high-voltage relay. This low-voltage circuit includes a temperature control switch, relay coil, and auxiliary circuit that work together to control the high-voltage relay through electromagnetic actuation rather than direct high-voltage switching, thereby improving reliability while maintaining control functionality
Solution Approach 2:
The patent divides the heating control system into separate low-voltage control circuit and high-voltage power circuit. The low-voltage circuit handles switching control while the high-voltage circuit handles power delivery, isolating the control function from the high-voltage switching to prevent contact sticking and improve overall system reliability
2Device complexity
If the temperature control switch directly controls the high-voltage relay, then the control simplicity is improved, but the response speed to overheating is too slow causing safety issues
Solution Approach 1:
The patent incorporates a pre-heating circuit that activates before the main heating operation. This pre-heating circuit includes heating resistors and control switches that prepare the system in advance, allowing the temperature control switch and protective devices to be pre-positioned and ready for immediate action when overheating conditions occur, thereby improving response speed without significantly increasing overall system complexity
3Ease of operation
If the high-voltage relay contacts are used for switching, then the switching capability is improved, but the contact sticking occurs preventing circuit disconnection
Solution Approach 1:
The patent introduces a low-voltage auxiliary control circuit as an intermediary that uses electromagnetic relay actuation instead of direct high-voltage contact switching. The low-voltage control circuit includes a temperature control switch connected to a relay coil, which actuates the high-voltage relay contacts through electromagnetic force, thereby maintaining switching capability while eliminating direct high-voltage contact sticking
Solution Approach 2:
The patent replaces the mechanical direct-contact switching system with an electromagnetic actuation system. The low-voltage control circuit uses electromagnetic fields generated by the relay coil to actuate the high-voltage relay contacts, substituting mechanical high-voltage switching with electromagnetic control to prevent contact sticking while maintaining switching functionality
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 apparatus effectively cuts off the high-voltage circuit to prevent overheating, avoiding damage to the PTC heater and ensuring vehicle safety by switching current to the high-voltage fuse when the current-carrying fuse fuses or the temperature fuse activates.
Implementation Method 1
A resistance value of the current-carrying fuse is less than a resistance value of the current fuse, and a fusing temperature of the current-carrying fuse is lower than a fusing temperature of the temperature fuse
Implementation Method 2
the current fuse, a temperature fuse, and a current-carrying fuse
Data Source
AI summary
A high-voltage fusing apparatus includes a current fuse, a temperature fuse, and a current-carrying fuse. The current fuse is connected in series with the temperature fuse, and a series branch of the current fuse and the temperature fuse is connected in parallel with the current-carrying fuse. A resistance value of the current-carrying fuse is less than a resistance value of the current fuse, and a fusing temperature of the current-carrying fuse is lower than a fusing temperature of the temperature fuse. The high-voltage fusing apparatus can cut off a high-voltage circuit quickly, and effectively protect the high-voltage heating circuit from overheating.