Protective Circuit for Overvoltage and Short-Circuit Protection
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Solution Overview
Problem
Electronic devices designed for 12 volts often face short-circuit issues when used in environments with higher operating voltages, such as trucks or buses, leading to fault voltages that can damage components and cause undesired external supply.
Innovation Solution
A protective circuit with elements like inductive, capacitive, and resistive components that limit voltage increases and shape measurement voltages to prevent triggering during short circuits, ensuring reliable protection across all operating states, including when the device is disconnected or under fault conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage limiting means are provided at the device terminal to protect against overvoltage, then protection against fault voltage is improved, but the response speed deteriorates because the voltage rise is limited
Solution Approach 1:
The protection function is divided into two independent parts: voltage limiting means (inductor LPR) that limits voltage rise rate, and overvoltage detection means (comparator SPR1) that detects actual overvoltage conditions. This segmentation allows each part to perform its specific function optimally without compromising the other.
Solution Approach 2:
A measurement voltage signal is introduced as an intermediary between the actual voltage at the device terminal and the comparator. This measurement signal is shaped by the voltage limiting means but represents the actual voltage condition, allowing the comparator to respond quickly to true overvoltage events while the limiting means protects against voltage spikes.
2Reliability
If the device is designed to be short-circuit proof with all inputs and outputs withstand short circuit to ground, then safety is improved, but voltage fluctuations significantly higher than operating voltage occur at inputs and outputs
Solution Approach 1:
The harmful high voltage fluctuations are extracted and isolated from the device terminal through the protection circuit. The inductor LPR and comparator SPR1 detect and respond to these fluctuations, preventing them from reaching and damaging the electronic component 101 while allowing the device to maintain its short-circuit proof design.
Solution Approach 2:
The voltage limiting means converts the harmful rapid voltage rise into a controlled, limited voltage increase. By limiting the rate of voltage change, the circuit transforms potentially destructive voltage spikes into manageable voltage transitions that the protection circuit can detect and respond to safely.
3Reliability
If voltage limiting means are added to protect against overvoltage, then protection reliability is improved, but device complexity increases
Solution Approach 1:
The protection circuit is merged with the existing device terminal structure. The voltage limiting means and overvoltage detection means are integrated into the terminal circuitry, sharing common elements like the device terminal connection and ground reference, thereby minimizing additional complexity while achieving comprehensive protection.
Solution Approach 2:
The protection circuit is designed to handle multiple protection scenarios universally: overvoltage from external sources, reverse polarity, and transient spikes. The same inductor LPR and comparator SPR1 configuration provides protection across all these conditions, reducing the need for separate protection circuits for each scenario.
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 protective circuit effectively prevents overvoltages and overcurrents in all operating states, allowing standard low-voltage devices to be safely used in high-voltage vehicle systems, including trucks and buses, without damaging the device connections.
Implementation Method 1
at least one inductive circuit element for limiting the rate of change of the reference voltage relative to the rate of change of the voltage applied to the external circuitry
Implementation Method 2
at least one capacitive circuit element for limiting the rate of change of the reference voltage relative to the rate of change of the voltage applied to the external circuitry
Implementation Method 3
at least one voltage-shaping element, in particular configured with at least one diode, for generating the measuring voltage from the voltage applied to the external circuitry
Data Source
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AI summary
The aim of the invention is to make a device terminal (202; PA_SPK-, PA_SPK+) of an electronic device (200; 300; 400; 410), in particular for a motor vehicle, resistant to short-circuits, even a short-circuit with respect to an offset voltage which exceeds the operating voltage (Vbb), said terminal being designed for an external connection, preferably for connecting to a load (RL). This is achieved by a protective circuit (204; 304; 403; 411) for overvoltage and/or overcurrent protection, comprising a comparison stage (SPR1) for comparing a measurement voltage, which is formed from a voltage applied to the external connection, with a comparison voltage, in particular with a supply voltage or a voltage obtained therefrom of the electronic device (200; 300; 400; 410), and at least one switching element (UPR1, UPR2), which is arranged in series between the device terminal (202; PA_SPK-, PA_SPK+) and the external connection and which can be controlled by the comparison stage (SPR1), for separating the external connection from the device terminal (202; PA_SPK-, PA_SPK+).