Optocoupler working principle function electric parameter application circuit

Optocoupler （Optical coupler）

1. name ：

Optocoupler , Also called Optocoupler （optical coupler equipment, English abbreviation OCEP/OC）, Also called optocoupler or optoisolator .

2. working principle ：

It is a device that uses light as the medium to transmit electrical signals , Usually put the illuminator （ Infrared light emitting diode LED） And light receiver （ Photosensitive semiconductor tube or photosensitive resistor ） Enclosed in the same shell . When an electrical signal is applied to the input, the light emitter emits light , When the light receiver receives light, it generates an electric current , From the output , So as to achieve “ electric — light — electric ” control .

It is mainly used for isolation of transmission signals during communication and control .

internal structure ：

3. function ：

1. The optocoupler can effectively suppress the sharp pulse and various clutter interference when transmitting signals

2. One way signal transmission , The input and output terminals are completely electrically isolated , The output signal has no effect on the input , Strong anti-interference ability

3. The clutter voltage entering the optocoupler input is relatively small , Only a very weak current can be formed , There is not enough energy to make the diode light up , This will not affect the output

4. There is no electrical connection between the input circuit and output circuit of the optocoupler , There is no common ground ; The distributed capacitance between is very small . And the insulation resistance is very large . Therefore, it is difficult to transmit various dry anti clutter waves on one side of the loop to the other side through the optocoupler , The interference signal of common impedance coupling is avoided

5. The optocoupler plays a very good role in safety protection , Even when an external device fails , Or when the input signal line is short circuited , It won't affect another device , At the same time, the light input circuit and output circuit can withstand several dry volts of high voltage

6. The optocoupler responds very quickly , The response delay time is us level , Faster have ns level .

4. classification

• linear relationship

  linear

  nonlinear

• Speed

  Ordinary ： response time us level

  High speed ： response time ns level

• voltage

  low pressure ：5-15V

  High pressure ： Greater than 30V

5. Electrical parameters

VF： Input voltage drop

IF： Input current

IO： Maximum current at output end

VCC： Supply voltage （ Some have ）

VCE： The maximum voltage applied to the output terminal

RT： Rising edge time

RF： Falling edge time

CTR： Current transfer ratio , When the output voltage remains constant , It is equal to the DC output current IC And DC input current IF Percent of

6. Typical application circuit analysis

Circuit one ：

Circuit two ：

Circuit three ：

Circuit four ：

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