Optocoupler (optical coupler，and the English abbreviation is OC) is also called photoelectric isolator, refering to optical coupler. The optocoupler transmits electrical signals through optical media. It has a good isolation effect on the input and output of the electrical signals, so it is widely used in various circuits. At present, it has become one of the most diverse and widely used optoelectronic devices. Optical couplers are generally composed of three parts: light emission, light reception and signal amplification. The input electric signal drives the light-emitting diode (LED) to emit a certain wavelength of light, which is received by the photodetector and generates photocurrent, and then amplified and output. This completes the electro-optical-electrical conversion, thus playing the role of input, output and isolation. Because the input and output of optical coupler are isolated from each other, the transmission of electric signal has the unidirectional characteristics, so it has good electrical insulation and anti-interference ability. With the increase of service time and the decrease of transmission ratio, it is necessary to provide sufficient driving current margin for Q2 in order to prevent control failure.
There are many kinds of optocoupler, such as photodiode type, phototransistor type, photoresistor type, photocontrolled crystal elucidation type, photoelectric documented darling type, integrated circuit type and so on. (The appearance has metal round shell packaging, plastic double in-line insertion and so on.).
The working principle is that the light source emits light by adding electric signals at the input end of the optocoupler. The intensity of light depends on the magnitude of the exciting current. When the light is illuminated on the encapsulated receiver, the photocurrent is generated by the photoelectric effect and is drawn out from the output end of the receiver. Thus, the conversion of electricity-light-electricity is realized.