24-VAC multi-channel solid state relay reference design using digital isolator
Description
This reference design demonstrates a multi-channel solid state relay (SSR) using a single isolation. The design uses a multi-channel digital isolator with a single isolated power supply and common ground gate-drive circuit to control multiple SSRs independently. The design is rated for 24-VAC powered relays with current rating up to 2 A: but scalable up to 240 VAC and higher current rating. Each SSR channel consumes less than 75-mm2 space with a maximum height of the component around 3-mm: enabling considerable size saving compared to electromechanical relays. The use of single isolated power supply reduces board space and BOM cost.
Features
- Multiple solid-state relays using a single isolation with multichannel digital isolator: easily scalable to any number of SSR channels with minimum extra costSSR drive voltage 24 VAC ±20%: drive current 2-A RMS (voltage and current rating: scalable by using appropriately rated components)SSR turn on and turn off time: 15–300 μs (adjustable): average current consumption per SSR drive (referred to primary) SSR size 2 per channel. Height is around 3 mm.Functionally isolated open-loop flyback based power supply without the need of an MCUSurge and switching overvoltage protection
Applications
- Thermostat
- HVAC controller
Product Categories
- Isolation