SLVAFU8 July 2024 TPSI2072-Q1 , TPSI2140-Q1 , TPSI3050 , TPSI3050-Q1 , TPSI3052 , TPSI3052-Q1 , TPSI3100 , TPSI3100-Q1
Solid-state relays are switches with no moving parts that control loads with signals provided by an external device, such as an MCU. High voltage systems, like a high-voltage battery in an electric vehicle, need solid-state relays to control a high voltage load with a low voltage signal. These types of applications often require isolation to prevent two power domains forming an undesired ground loop due to a high potential difference as well as to monitor user protection from hazardous currents.
There are many methods available to achieve isolation for a solid-state relay. Photo or optical isolation technologies are well established in the industry for the last few years. New capacitive and inductive isolation technologies are able to provide advantages over photo isolation. This includes improved reliability, and the ability to quickly send and receive signals across the isolation barrier to allow for diagnostics information to inform the system of unexpected faults like over-current or over-temperature. This application note explores the different types of solid-state relays and their internal topologies.