Optocoupler is a device that transmits electrical signals using light as a medium, usually encapsulating the light-emitting diode (IR LED) and the light emitting device (photosensitive semiconductor tube) in the same casing. When the input signal is added, Optocoupler the light is emitted by the light device, and the optical current is generated from the output end, thus the "electric-optical-electric" conversion is realized.
The main characteristics of Optocoupler are as follows:
1. Input and output between the insulation, its insulation resistance is generally greater than 10000mω, withstand pressure can be more than 1kV, and some can even reach more than 10kV.
2. Because the optical receiver can only accept the information of the light source, the other can not, so the signal from the source to the optical receiver will not appear feedback phenomenon, Optocoupler its output signal will not affect the input.
3. Because the light-emitting device (gallium arsenide infrared diode) is a resistive current driving device, and noise is a high internal resistance of micro-current voltage signal. Therefore, the common-mode rejection ratio of optocoupler is very large, so the optical coupler can restrain the interference and eliminate the noise well.
4. Easy to cooperate with logic circuit.
5. Fast response speed. The time constants of optocoupler devices are usually in milliseconds or even microseconds.
6. No contact point, long life, small size, impact resistance.
The optical coupler of the input signal is coupled to the output end by light, Optocoupler because it has the advantages of small size, long life, no contact, strong anti-interference ability, insulation between output and input, one-way transmission signal and so on, it has been widely used in digital circuit.
The main advantages of optical coupling are: signal one-way transmission, input and output completely realize the electrical isolation, output signal on the input side without impact, anti-interference ability, work stability, no contact, long service life, high transmission efficiency. Optocoupler is the development of new devices in the 70 's, has been widely used in electrical insulation, level conversion, cascade coupling, drive circuit, switching circuit, chopper, harmonic oscillator, signal isolation, class isolation, pulse amplification circuit, digital instrumentation, Optocoupler long-distance signal transmission, pulse amplification, Solid State relays (SSR), instrumentation, Communication equipment and microcomputer interface. In the Single-chip switching power supply, the use of linear optocoupler can constitute a optocoupler feedback circuit, by adjusting the control terminal current to change the duty ratio, Optocoupler to achieve precision voltage regulation purposes.