Semiconductor Relay Circuit With Self-Powered Overheat Protection
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Solution Overview
Problem
Semiconductor relay devices face challenges in protecting output-side apparatuses from overvoltage, overcurrent, and overheating without requiring external power sources or complex protection circuit designs that consume significant board space and complicate the design.
Innovation Solution
The semiconductor relay device incorporates a zener diode, serially coupled diodes, and a thyristor with a control terminal, utilizing temperature-dependent forward voltage to generate a control signal for overheat protection, allowing autonomous operation without constant current or voltage sources and simplifying the design by regulating the number of diodes to achieve overheat protection within a targeted temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex protection circuits are used to protect output-side apparatus from overvoltage, overcurrent, and overheating, then reliability is improved, but device complexity increases and board space is consumed
Solution Approach 1:
The patent combines multiple protection functions (overvoltage protection, overcurrent protection, and overheat protection) into a single integrated protection circuit. The protection circuit includes a zener diode for overvoltage protection, a fuse for overcurrent protection, and temperature-dependent diodes with a thyristor for overheat protection, all merged into one compact unit that protects the output-side apparatus from multiple hazards simultaneously.
Solution Approach 2:
The protection circuit operates autonomously without requiring external control signals or power sources. The temperature-dependent diodes automatically generate control signals based on temperature changes, and the thyristor triggers protection actions self-activating when temperature thresholds are exceeded. The fuse automatically blows when overcurrent occurs, and the zener diode clamps overvoltage without external intervention.
2Reliability
If external power sources are used for protection circuits, then protection reliability is improved, but device complexity and power consumption increase
Solution Approach 1:
The protection circuit is designed to operate autonomously without external power sources. The temperature-dependent diodes generate control signals using only the power available from the protected circuit itself. When temperature increases, the diode forward voltages change, automatically triggering the thyristor to activate protection functions. The fuse responds to overcurrent conditions and the zener diode responds to overvoltage conditions without requiring any external power supply.
Solution Approach 2:
The protection circuit utilizes temperature-dependent changes in diode forward voltage to trigger protection actions. As temperature increases, the forward voltage of the series-connected diodes decreases, and when it drops below the zener diode's breakdown voltage, the thyristor is triggered. This parameter-based triggering mechanism eliminates the need for external power sources while maintaining reliable protection.
3Measurement precision
If multiple diodes are serially coupled to achieve temperature-based control, then overheat protection precision is improved, but device complexity increases
Solution Approach 1:
The patent uses the temperature-dependent forward voltage characteristics of diodes to detect temperature changes. By serially coupling multiple diodes, the total forward voltage becomes a more sensitive indicator of temperature changes. When the combined forward voltage drops below the zener diode's breakdown voltage due to temperature increase, the thyristor is triggered, providing precise temperature-based protection control.
Solution Approach 2:
The zener diode acts as an intermediary element that compares the temperature-dependent voltage from the series-connected diodes against a reference breakdown voltage. This intermediary mechanism translates subtle temperature changes into a clear trigger signal for the thyristor, achieving precise temperature detection without requiring complex sensing circuits.
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 enables effective overheat protection without external power, maintaining device operation and reducing design complexity, while ensuring the output-side apparatus is safeguarded from overheating without consuming continuous current or voltage, thus enhancing reliability and efficiency.
Implementation Method 1
utilizing temperature-dependent forward voltage to generate a control signal for overheat protection
Data Source
AI summary
A semiconductor relay device includes a conversion circuit configured to receive an input signal from outside and pass a first current to a first node based on the input signal. A zener diode has an anode coupled to a second node and a cathode coupled to the first node. A resistor is coupled between the second node and a third node. A number n of diodes are serially coupled. A thyristor has an anode coupled to the first node, a cathode coupled to the second node, and a control terminal coupled to the third node. A transistor has a gate coupled to the first node. An anode of a diode at a first end of the n diodes is coupled to the first node, and a cathode of a diode at a second end of the n diodes is coupled to a third node.