The optocoupler (optical coupler, and the english abbreviation is OC) is also called photoelectric isolator, which referred to the optical coupler. The optocoupler transmits electrical signals through optical media. It has a good isolation effect on the input and output 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. The optocoupler 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.
There are dozens of types of optocoupler, including general type (it is also divided into the nonbase lead and base lead), Darlington type, Schmidt type, high-speed type, optical integrated circuit, optical fiber dimension, photosensitive thyristor type (with one-way thyristor, two-way thyristor) and photosensitive field-effect tube type.
It has the one-way signal transmission, and the input and output terminals completely achieve electrical isolation, and the output signal has no impact on the input. It has strong anti-interference ability, stable operation, no contact point, long service life, high transmission efficiency. Optocoupler is a new device developed in the 1970s. It has been widely used in electrical insulation, level conversion, stage coupling, driving circuit, switch circuit, chopper, multi-resonator, signal isolation, stage separation, pulse amplification circuit, digital instrument, long-distance signal transmission, pulse amplification, solid-state relay (SSR), instrumentation, communication equipment and computer interface. In the single-chip switching power supply, the linear optocoupler can be used to form the optocoupler feedback circuit, and the duty cycle can be changed by adjusting the current of the control terminal to achieve the purpose of precise voltage stabilization.