Ohne Titel

PhotoMOS Relays

Topology

How does it work

Diversity of PhotoMOS

Application scenaries

Normally closed

Current limiting

Short circuit protected

High power

Typically used for alarm contacts. This type of MOSFET has a thin layer of n-type Si just below the gate-insulating layer, wich forms a conducting channel between source and drain

In order to prevent damage from overcurrent. It is activated as soon as overcurrent occurs and automatically reduces the voltage at the gates of the MOSFET

Protect both the output MOSFETs and the load circuit against overcurrent. A protective circuit detects if the load current increases above a certain limiting value, threatening a shor-circuit

High power PhotoMOS relays are therefore offered mainly in SIL or PD packages - current models allow load currents of up to 10 A in a SIL

Electrical Mobility

Energy managment

Building automation

Measurement equipement

When the LED is operated, the PDA translates the light into electrical current and voltage, wich drive the power MOSFETs on the output

1. An input LED optically coupled to a photodiode arrar (PDA)

2. A control circuit

3. Two power MOSFETs that function as output devices

Advantages of PhotoMOS

Disadventages of PhotoMOS relays

- Bounce - free operation

- Immune to electromagnetic interference

- Can switch far below 1 ms

- Much better shock and vibration resistance of more than 1000g

- Better switching life

- Maximum switching voltage increased

- Contact resistance

- Output capacitance

- Overload

- Galvanic isolation at the output

This most application in the automotive field is isolation monitoring

Typically used for alarms contacts

Used in battery-driven applications like smoke detectors or burglar alarm sensors

This is the case for PLC or IPC. This task is helped by the linear output characteristics of the PhotoMOS relays