Smart Solid-State Relays: Quietly Powering the Next Generation of Building Automation

This episode of Inside Electronics features Alix Paultre, Editor at Large for Electronic Design, and Dr. Hugo Guzman, Product Marketing Manager-Integrated Circuits at Littelfuse. Alix and Hugo discuss how smart solid-state relays (SSRs) are reshaping residential, commercial, and industrial building automation. 

As engineers pack more HVAC controls, access systems, smart thermostats, sensors, and wireless modules into existing infrastructure, they must meet tight EMC, EMI, safety, and form-factor constraints while often working without a dedicated C wire. Hugo contrasts legacy electromechanical relays—bulky, noisy, prone to contact wear, arcing, and limited lifetime—with SSR-based designs that offer silent operation, predictable switching behavior, and improved reliability in inductive-load environments. 

Hugo also explains how Littelfuse’s smart SSRs integrate application-specific intelligence, such as load-powered operation and latching for C wire–less smart thermostats (CPC1601M), minimizing quiescent current and extending battery life in retrofit designs. 

For video doorbells and access control, the CPC2501M adds controlled handling of chime inrush currents up to 5 A for a few milliseconds, while maintaining continuous power to both chime and camera from a compact QFN package. Throughout the episode, Alix and Hugo emphasize how these smart SSRs help designers achieve smaller, safer, and more energy-efficient building automation systems that comply with stringent 24/7 reliability and safety standards.