LH1518AT

Solid State Relays

Solid state relays, often referred to as electronic relays, are electronic switches used to turn on and off electrical circuits. They are similar to mechanical relays in that their operation and function is substantially the same, with the difference being that they are non-contact devices and require no moving parts. A solid state relay consists of an input section, an output section, and a semiconductor section.

The input section of a solid state relay is typically an opto-isolator, which provides electrical insulation between the device’s control and load circuits. The output section is often a power MOSFET or an opto-triac, depending on the type of load. The semiconductor section is a bridge rectifier that provides protection against reverse voltages.

LH1518AT Application Field and Working Principle

The LH1518AT is a solid state relay that is designed for low current, low voltage applications. It has a maximum power handling capacity of 2W and an input voltage rating of 18V. It is used for home automation, HVAC control, automated manufacturing, security systems, and other applications where precise switching of low voltage and low power circuits is required.

The LH1518AT is a bidirectional device, meaning it can switch current both ways, so it can be used to control both AC and DC signals. It is an electromechanical switch, with a very fast switching action. It is based on the principle of optical isolation, which eliminates contact bounce and reduces the possibility of arcing. It has a switching speed of <100us and a minimum on/off time of 1ms.

The working principle of the LH1518AT is based on a bridge circuit consisting of a photocoupler, power MOSFET, and rectifier. When the control input voltage is applied to the device, the photo-coupler inside the device triggers the MOSFET, which in turn, turns the load ON or OFF depending on the applied voltage.

The LH1518AT is designed to offer low on resistance and low off resistance, while providing insulated electrical and thermal isolation between the input and output. It is RoHS compliant and can operate in extreme ambient temperatures ranging from -20°C to 85°C.

The LH1518AT is a reliable and cost-effective alternative to conventional contact relays, and is thus suitable for use in a wide variety of applications demanding precise switch control. It is rated for up to 1 million operations, making it an ideal choice for heavy duty switching.