Optically Isolated Latching Solid-State Relay With Self-Powered Hold
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Solution Overview
Problem
Conventional latching relays, whether mechanical or solid-state, face issues such as susceptibility to damage and undesirable operating characteristics, with mechanical relays being fragile and solid-state relays requiring a separate supply to remain latched.
Innovation Solution
A discrete packaged power semiconductor device with a supply terminal, load terminal, coupling circuits, latch circuit, and transistors, utilizing optocoupler circuits for isolation and a capacitor for local supply, allowing the relay to maintain the on state without external power consumption and featuring MOSFET transistors for linear operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional solid-state relays use SCRs to switch and maintain on state, then the relay can maintain latched state, but it requires a separate supply to remain latched and exhibits undesirable operating characteristics
Solution Approach 1:
The latching relay uses the load current itself to maintain the latched state through internal circuitry including a phototransistor and triac, eliminating the need for a separate external supply to maintain the latched state. The load current charges a capacitor that sustains the triggering signal for the triac, enabling self-maintenance without additional power consumption.
2Ease of operation
If mechanical relays are used to switch loads, then the relay can be operated, but it is susceptible to damage from impact and mechanical components
Solution Approach 1:
The patent replaces mechanical relay components with solid-state electronic components including a phototransistor, triac, capacitor, and resistor. This solid-state implementation eliminates mechanical moving parts that are susceptible to impact damage, while maintaining the switching operation capability through electronic control mechanisms.
3Productivity
If conventional solid-state relays are used, then the relay can switch loads, but it has undesirable operating characteristics
Solution Approach 1:
The patent changes the operating parameters and circuit configuration by using a phototransistor-triac combination with a capacitor-resistor network, rather than conventional SCR-based solid-state relays. This parameter change enables linear operation characteristics and eliminates the undesirable traits of conventional solid-state relays while maintaining load switching capability.
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 provides a robust, energy-efficient latching relay with linear operating characteristics, capable of switching loads on and off without external power, and includes a refresh mode to maintain voltage levels, ensuring reliable operation.
Implementation Method 1
The first and second coupling circuits are optocoupler circuits that use optical coupling techniques
Implementation Method 2
The photovoltaic stack of the PVSPD circuit is used for enabling a refresh mode of the latching relay
Implementation Method 3
The local supply node is supplied by the capacitor
Data Source
AI summary
A latching relay includes a supply terminal, a load terminal, first and second coupling circuits, a latch circuit, first and second transistors, and a local supply node coupled to a capacitor. In one example, the supply terminal is coupled to a supply node and the load terminal is coupled to the load. The first and second transistors control the conductivity of a drive transistor coupled to the load. A microcontroller controls the latching relay to switch the load on and off. To enable the load, the microcontroller sinks current from the supply terminal and through the first coupling circuit. While the load is enabled, the capacitor is discharged. The latching relay is operable in a refresh mode in which current is pulsed through the first coupling circuit causing capacitor to be re-charged from the supply terminal. To disable the load, the microcontroller sinks current through the second coupling circuit.