Protection device and protection method
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Solution Overview
Problem
Existing protection devices for air conditioning systems face issues with slow operation speed, high costs, and large size due to the need for high-voltage transistors, and they struggle with heat dissipation and action lag in limiting excess current and voltage in communication circuits.
Innovation Solution
A protection device with a first transistor connected in series with the communication line, controlled by a current-limiting controller to increase resistance when excess current flows, and a current interrupt controller to turn off the transistor when an excessive voltage is reached, preventing excess current and interrupting the electric current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermistor having a positive temperature coefficient is used to limit excess current, then the communication circuit is protected from excess current, but there is action lag in limiting the excess current
Solution Approach 1:
The patent replaces the thermistor's thermal-based current limiting mechanism with an electronic control system using a transistor and control circuit. The transistor's collector-emitter path serves as the current path, and the control circuit actively regulates current based on voltage detection, eliminating the thermal inertia and action lag inherent in thermistor-based protection.
2Reliability
If a current-limiting bipolar transistor is used in the active region to protect from excess current, then the communication circuit is protected, but the transistor needs to withstand high voltage and has high collector dissipation requirements
Solution Approach 1:
The patent employs dynamic operation of the transistor, switching between active region and saturation region based on protection needs. The transistor operates in the active region during normal current limiting and transitions to saturation region when excess voltage is detected, allowing the use of transistors with lower voltage and power ratings while maintaining protection effectiveness.
Solution Approach 2:
The patent introduces a control circuit as an intermediary between the transistor and the communication circuit. This control circuit detects voltage across the transistor's collector-emitter path and regulates the base-emitter voltage accordingly, enabling precise current control without requiring the transistor itself to withstand extreme voltages and powers.
3Reliability
If a protection device with high voltage withstand capability is used, then the communication circuit is protected from voltage impressing, but the device becomes slow in operating speed
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the voltage across the transistor's collector-emitter path. When the voltage exceeds a predetermined threshold, the control circuit immediately adjusts the base-emitter voltage to limit current. This closed-loop feedback enables rapid response to voltage transients without requiring the transistor to be inherently slow for high voltage protection.
4Device complexity
If a thermistor is used for protection, then the device structure is simple, but heat dissipation becomes a problem during excess current limiting
Solution Approach 1:
The patent replaces the thermistor's passive thermal-based protection with an active electronic control system. The transistor and control circuit actively regulate current flow, preventing excessive heat generation in the first place rather than relying on thermal effects. This eliminates the heat dissipation problem while maintaining structural simplicity through integration.
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 solution reduces action lag and lowers costs by using a more efficient and cost-effective transistor design that quickly limits excess current and interrupts excessive voltage, providing stable protection for air conditioning system communication circuits.
Implementation Method 1
a base-emitter voltage controller configured to control a base-emitter voltage of the first transistor when the electric current flowing in the first current path is equal to or greater than a set electric current, thereby limiting an electric current flowing in the first current path
Implementation Method 2
a current interrupt controller configured to turn off the first transistor when an end-to-end voltage of the first current path is equal to or greater than a set voltage
Data Source
Figure 1
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AI summary
A current path of a first transistor (TR1) is connected in series to a communication line. When the electric current through the current path of the first transistor (TR1) becomes equal to or greater than a set electric current, a current-limiting controller (231) limits the electric current through the current path by controlling the first transistor (TR1) to increase the resistance of the current path. When the end-to-end voltage of the current path of the first transistor (TR1) becomes equal to or greater than a set voltage, a load limiter (232) switches the first transistor (TR1) off.