What are the types of optocouplers

Optocouplers can be classified into various types based on their output structure, working principle, and application scenarios. The following are common classification methods and specific types:

1. Transistor output optocoupler

-Structure: The input terminal is a light-emitting diode (LED), and the output terminal is a phototransistor (NPN or PNP type), which drives the transistor to conduct by emitting light from the LED.

-Features: The output is a switch signal (on/off), with a moderate response speed (usually in the μ s range), suitable for signal isolation with low voltage and low current.

-Application: Power feedback, signal level conversion, weak signal isolation in industrial control.

2. Darlington tube output optocoupler

-Structure: The output terminal adopts a Darlington transistor (a combination of two transistors with higher gain), driven by LED.

-Features: It has high current gain (can drive larger loads without external amplification circuits), slightly slower response speed than ordinary transistor types, but larger output current (up to several hundred mA).

-Application: Isolation control for driving medium power loads such as small relays and solenoid valves.

3. Thyristor output optocoupler (solid-state relay optocoupler)

-Structure: The output terminal is a unidirectional thyristor (SCR) or a bidirectional thyristor (TriaC), and the LED emits light to trigger the thyristor to conduct.

-Features: It can directly control AC or DC high-voltage high current circuits, achieve strong and weak current isolation, have no mechanical contacts, and have a long service life.

-Category:

-Unidirectional thyristor output: suitable for DC or unidirectional AC circuits.

-Bidirectional thyristor output: suitable for AC circuits.

-Application: Home appliance control (such as dimming, speed regulation), industrial high-voltage switch control, motor drive.

4. IGBT driven optocoupler

-Structure: The output terminal is a dedicated driver circuit that integrates photoelectric reception, signal amplification, and isolation functions, designed specifically for driving IGBT (Insulated Gate Bipolar Transistor).

-Features: It has high isolation voltage, fast response (ns level), overcurrent protection and other functions, and can directly drive high-power IGBT modules.

-Application: High power power electronic systems such as frequency converters, inverter power supplies, and motor drives.

5. High speed optocoupler

-Structure: The output terminal adopts high-speed photodiodes+amplification circuits (such as Schottky barrier diodes, high-speed operational amplifiers), or integrated CMOS logic circuits.

-Features: Extremely fast response speed (ns level, up to several hundred Mbps), suitable for isolation of high-frequency signals or high-speed data transmission.

-Application: Communication interface isolation (such as RS485, CAN bus), high-frequency signal transmission, digital circuit isolation.

6. Optoelectronic relay (optocoupler relay)

-Structure: The output terminal is a MOSFET switch, driven by LED, and controlled by optical signals to turn on/off the MOSFET.

-Features: Contactless, low on resistance, high isolation voltage, long lifespan, combining the isolation of optocouplers with the switching characteristics of relays.

-Applications: Signal switching for precision instruments, high-frequency circuit switches, and low-noise isolation in medical equipment.