Electromagnetic Relay Drive Circuit Fast Response
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Solution Overview
Problem
Electromagnetic relays in safety-critical applications require fast response times and high reliability to prevent accidental switching and costly false tripping, while existing solutions either compromise on simplicity and cost or fail to ensure galvanic isolation effectively.
Innovation Solution
A control circuit for an electromagnetic relay using two switching devices in series with a third switching device in parallel, driven by separate voltage sources and signal paths, including signal inverters to prevent external interference, and a monitoring system with resistors and comparators to verify functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two switching devices are used in series to improve reliability, then the response time increases due to additional switching operations
Solution Approach 1:
The control circuit pre-charges a capacitor through the first switching device before closing the second switching device. This preliminary action stores energy in the capacitor, which is then discharged through the relay coil when both switches are closed, enabling fast relay activation without requiring prolonged current buildup through two series switches.
Solution Approach 2:
The control circuit uses sequential switching phases: first charging the capacitor through the first switching device, then discharging it through the relay coil when the second switching device closes. This periodic charge-discharge cycle enables rapid relay response while maintaining the safety of two-series-switch control.
2Reliability
If separate signal paths with inverters are used to prevent external interference, then the device complexity increases
Solution Approach 1:
The control circuit divides the control signal into two separate independent signal paths, each controlling one switching device. This segmentation ensures that external interference affecting one path does not compromise the other, maintaining reliability while using simple inverter circuits for signal inversion in each path.
3Loss of time
If a semiconductor switch is used parallel to switching contacts to reduce response time, then the current carrying requirement increases
Solution Approach 1:
The control circuit introduces a capacitor as an intermediary energy storage element between the switching devices and the relay coil. The capacitor absorbs and releases energy rapidly, enabling fast relay response without requiring the semiconductor switch to continuously carry high current, thus reducing the current carrying burden on switching components.
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 achieves quick switching operations with enhanced reliability and fault tolerance, ensuring that accidental activation is prevented and functionality is monitored effectively, thereby improving the overall performance and safety of electromagnetic relays in critical applications.
Implementation Method 1
If an electric current flows through the relay coil, a magnetic field is generated around the relay coil
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a drive circuit (10) for an electromagnetic relay having a relay coil (11) and switch contacts, comprising a first switching device (13a), which is arranged between a first terminal of the relay coil (11) and a first voltage source (12a), a second switching device (13b), which is arranged between a second terminal of the relay coil (11) and a zero potential, and a control device (14) which is designed to produce a current flow through the relay coil (11) to close both switching devices (13a, 13b). In order to provide a drive circuit which, firstly, has the shortest possible response time and, secondly, can be produced constructively simply and therefore cost- effectively, a second voltage source (12b) be provided, which is connected via a third switching device (13c) to the first terminal of the relay coil (11), wherein the third switching device (13c) is arranged connected in parallel with the first switching device (13a), and the second voltage source (12b) has a higher voltage level than the first voltage source (12a), and the control device (14) is designed to produce a current flow through the relay coil (11), initially to close all three switching devices (13a, 13b, 13c) and, following the expiry of a predefined time period, firstly to open the third switching device (13c) again and secondly to keep the first and the second switching device (13a, 13b) closed.