Solid-State Overvoltage Isolation Circuit for Fast Terminal Protection
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Solution Overview
Problem
Existing protection circuits for electronic devices are inadequate in quickly decoupling external terminals from excessive voltages without drawing current or altering voltage, leading to potential damage to internal components, as they often require time for fuses to melt or current sensing components to divert current, which can be too slow to prevent component damage.
Innovation Solution
A protection system comprising a current limiting device and a solid state relay, including an optotransistor and light emitting diode, which detects excessive voltages and rapidly decouples the terminals using a control signal to prevent damage, with a detection circuit that applies a control signal to the solid state relay when a voltage exceeds a specific value, ensuring quick termination of current flow before component damage occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low current fuse is used to protect circuits, then the circuit can be protected from excessive current, but the response time is too slow as the fuse requires time to reach melting temperature
Solution Approach 1:
The patent replaces the mechanical fuse melting process with a solid-state electronic protection circuit that uses voltage detection and fast-acting transistors to interrupt current flow, achieving protection without the time delay inherent in thermal-mechanical fuse operation
Solution Approach 2:
The patent introduces an intermediary protection circuit between the terminals and the protected component, which includes voltage detection circuitry and switching elements that can rapidly respond to overvoltage conditions and disconnect the load before damage occurs
2Speed
If a current sensing component is placed in parallel with terminals to quickly detect excessive voltage, then the response time is improved, but current is drawn from the internal circuit which may cause measurement errors or alter voltage
Solution Approach 1:
The patent uses a high-impedance voltage detection circuit as an intermediary that monitors terminal voltage without drawing significant current, allowing accurate voltage sensing and rapid response without interfering with the normal operation or measurements of the protected circuit
Solution Approach 2:
The patent changes the operating parameters of the detection circuit to operate at very high impedance levels, enabling voltage detection with minimal current draw, thus avoiding alteration of the voltage being measured while maintaining fast response capability
3Reliability
If traditional relay systems are used for protection, then the circuit can be decoupled from excessive voltage, but the response time is insufficient to prevent component damage
Solution Approach 1:
The patent replaces the mechanical relay system with a solid-state electronic protection circuit using fast-acting transistors and voltage detection circuitry that can respond in microseconds, eliminating the mechanical movement time inherent in traditional relay systems
Solution Approach 2:
The patent introduces an intermediary solid-state switching circuit between the terminals and protected component that can rapidly respond to overvoltage conditions and disconnect the load before damage occurs, replacing the slow mechanical relay operation
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 effectively and rapidly protects electronic device components from excessive voltages by quickly terminating current flow through the solid state relay, preventing damage to the current limiting devices and ensuring the protection circuit responds faster than traditional relay systems, thus safeguarding internal circuits.
Implementation Method 1
a light emitting diode optically coupled to the optotransistor
Implementation Method 2
an optotransistor optically coupled to a light emitting diode, the optotransistor being coupled between the terminal and the electronic device in series with the current limiting device
Data Source
Figure 1~2
Figure 3
AI summary
A circuit for protecting an electronic device from excessive voltages applied to an input or output terminal (14) includes a solid state relay (120) coupling the electronic device to the terminal (14). The solid state relay (120) may include an optotransistor (130) coupled between the electronic device and the terminal (14) and a light emitting diode (124) optically coupled to the opto-transistor (130). The solid state relay (120) is coupled in series with a current limiting device (18,24), such as one or more enhancement mode field effect transistors. A voltage detector (30) coupled to the terminal detects a voltage larger than a specific value and causes current to flow thorough the light emitting diode (124), thereby interrupting the coupling between the terminal (14) and the electronic device. The voltage detector (30) may be coupled between two spaced-apart connections to the coupling path between the terminal to the electronic device so that the voltage detector avoids diverting current from the coupling path.