Load Short-Circuit Protection Circuit for Vehicle Air-Conditioning
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Solution Overview
Problem
Conventional short-circuit protection methods for loads like PTC elements in vehicle air-conditioning systems have a slow response time, leading to potential element damage due to overcurrent and surge voltage during short circuits.
Innovation Solution
A load driving device with a first switching element, drive means, voltage outputting means, comparison means, holding means, and a second switching element, which rapidly detects short circuits and cuts off power supply by maintaining a high signal to turn off the first switching element, improving response speed and preventing element damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional overcurrent protection based on fuse or microcomputer is used, then short-circuit protection is achieved, but response time is long causing element damage
Solution Approach 1:
The patent replaces conventional mechanical/electronic protection systems (fuses, microcomputer-based overcurrent protection) with a voltage-based detection system. By converting current detection to voltage detection through a series resistor, the system achieves faster response times because voltage changes are detected more rapidly than current changes in conventional systems.
Solution Approach 2:
The patent changes the detection parameter from current to voltage. By measuring voltage across a series resistor instead of directly measuring current, the system achieves faster response. The voltage signal changes more rapidly when a short circuit occurs, enabling the comparison circuit to detect the fault condition almost immediately.
2Loss of time
If fast response short-circuit detection is implemented, then element damage is prevented, but device complexity increases
Solution Approach 1:
The patent introduces a series resistor as an intermediary element that converts current information into voltage information. This simple passive component acts as a mediator between the load current and the voltage-based comparison circuit, enabling fast detection without requiring complex active sensing circuits or signal conditioning stages.
Solution Approach 2:
The patent replaces complex current sensing and processing circuits with a simple voltage comparison approach. By using a series resistor and voltage comparator instead of complex current sensors and microcomputer processing, the system achieves fast response with minimal circuit complexity.
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 significantly reduces the time from short-circuit detection to power cutoff, suppressing element damage and surge voltage, thereby enhancing the responsiveness and reliability of short-circuit protection.
Implementation Method 1
voltage outputting means for converting a current flowing through the load to a voltage and outputting the voltage
Implementation Method 2
comparison means for detecting a short circuit and outputting a high signal when an output voltage of the voltage outputting means is a predetermined reference voltage or higher
Implementation Method 3
holding means for maintaining the high signal of the comparison means for a predetermined period
Implementation Method 4
a first resistor provided on a control line that connects the drive means and the conduction control terminal of the first switching element, a second switching element provided on a line connecting an area between the first resistor and the second resistor and a ground
Data Source
AI summary
The purpose of the present invention is to improve responsiveness to short-circuit detection and rapidly cut off power supply to a load when a short circuit occurs. When a short circuit occurs, voltage exceeding the reference voltage of a comparison circuit is inputted as an input signal from a voltage output circuit, and a high signal is outputted from the comparison circuit. An FET is turned on by the output of the comparison circuit changing to the high signal. Consequently, an electric charge stored between the gate and emitter of an IGBT is discharged through a resistor, gate voltage decreases, and thereby the IGBT is turned off. The high signal of the comparison signal is held for a predetermined period by a holding circuit, and the IGBT is maintained in the off state over this period.