Solid-State Relay Circuit Without Opto-Couplers for Fast Switching
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Solution Overview
Problem
Electro-mechanical relays face reliability issues due to mechanical damage, low switching speeds, and poor electromagnetic compatibility (EMC) behavior, leading to a trend towards replacing them with solid state relays, but existing solid state relays with optical isolation are costly.
Innovation Solution
A solid state relay circuit using a relay transistor and a driver circuit with a constant current source, comprising diodes and resistors to switch the relay transistor, allowing for efficient operation without mechanical movement and reduced EMC issues, and potentially integrating a pulse width modulation (PWM) control for faster switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical isolation is used in solid state relays, then reliability is improved, but cost increases significantly
Solution Approach 1:
The patent extracts and eliminates the opto-coupler component from the solid state relay design, replacing it with a direct-drive transistor switching circuit. This removal of the optical isolation component significantly reduces cost while maintaining reliability through alternative switching mechanisms that do not require mechanical or optical parts.
Solution Approach 2:
The patent uses a transistor to replicate the switching function previously performed by opto-couplers, creating an electrical copy of the isolation and switching behavior. The driver transistor mimics the control function of optical relays while achieving the same reliability goals through solid-state electrical switching.
2Device complexity
If electro-mechanical relays are used, then simplicity of design is maintained, but switching speed decreases and mechanical damage occurs
Solution Approach 1:
The patent replaces the mechanical relay system entirely with a solid-state transistor switching circuit. The driver transistor and relay transistor configuration eliminates moving parts, armatures, and mechanical contacts, achieving high-speed switching through electrical field control while maintaining design simplicity through the use of standard semiconductor components.
3Ease of operation
If electro-mechanical relays are used, then ease of operation is maintained, but electromagnetic compatibility deteriorates over time
Solution Approach 1:
The patent replaces mechanical relay operations with solid-state transistor switching, eliminating the sources of electromagnetic interference generated by mechanical contact closure and opening. The transistor-based switching circuit provides clean, controlled electrical transitions that maintain ease of operation while dramatically improving electromagnetic compatibility and eliminating the degradation associated with mechanical wear.
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 enables faster switching speeds, reduced thermal heating, and improved EMC, while potentially lowering production costs by eliminating the need for opto-couplers, thus providing a reliable and cost-effective alternative to electro-mechanical relays.
Implementation Method 1
a driver circuit comprising a constant current source; wherein the driver circuit is configured and arranged to switchably operate the relay transistor
Implementation Method 2
at least one diode connected to a control terminal of the driver transistor; wherein the diode and the driver transistor are arranged to produce a constant voltage across the first resistor
Implementation Method 3
the relay transistor is configured and arranged to switchably operate the electrical load
Implementation Method 4
the driver transistor output terminal is directly connected a control terminal of the relay transistor and arranged to switchably operate the relay transistor
Data Source
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AI summary
The disclosure relates to solid state relay circuit for switching an electrical load. The solid state relay circuit may include a relay transistor; and a driver circuit comprising a constant current source. The driver circuit is configured and arranged to switchably operate the relay transistor, and the relay transistor is configured and arranged to switchably operate the electrical load.