What are the characteristics of optocouplers? Why optocouplers have strong anti interference perform

The photocoupler is an optical receiving module that encapsulates the light source and the photosensitive receiving optical signal device, which is a device that transmits electrical signals with light as the medium, its input and output are isolated from each other, and the input and output are converted in a way that uses electricity - light - electricity to achieve mutual isolation of input and output, and the electrical signal transmission is unidirectional, not interfered with by external information, one-way transmission, high safety factor, and has a strong anti-interference ability. Because the optical signal data information generation control circuit is a separate design, there is no coupling correlation between the components, it is an independent working performance, it emits a certain wavelength of optical signal, is invisible light, is eyebrow communication, secretly send autumn wave information exchange, and the execution circuit is separated from each other, without any messy information interference, is a pure single directional information transmission, more safe and reliable. Optical information reception is also an independent working mode, only accept a single directional information, it is a face-to-face information exchange device that transmits and receives packaged together, is not interfered with by external messy information, optical directional information is received by a photodiode, a photosensitive triode to generate photocurrent, and the output is amplified to produce control execution information, so that the control system completes the corresponding task.

Its information transmission and execution are realized by photocouplers, and it has strong anti-interference. Make a simple schematic diagram to illustrate the characteristics of the optocoupler and its ability to resist interference.

1. It can effectively suppress the noise of the grounding loop, eliminate the ground interference, and make the signal site and the main control terminal completely isolated electrically, so as to avoid accidental damage to the main control system.

2. It can transmit electrical signals between different potentials and different impedances, and has functions such as amplification and shaping of the signal, which greatly simplifies the actual circuit design.

3. The switching speed is fast, and the response speed of the high-speed photocoupler reaches the order of magnitude, which greatly expands the application of the photocoupler in digital signal processing.

4. Small size, the device mostly adopts double in-line packaging, with a variety of structures such as single channel, dual channel and up to eight channels, which is very convenient to use.

5. It can replace transformer isolation, which will not produce peak noise due to contact jumping, and has strong anti-vibration and anti-impact capabilities.

6. In addition to being used for power monitoring, the high linearity photocoupler is used in medical equipment for medical and intelligent monitoring, which can effectively protect the life safety of patients.

There are 4 types of commonly used optocouplers:

Ordinary type - a wide range of applications.

High-speed type - the composite structure of photodiode and high-speed switch tube is adopted, which not only has high response speed, but also maintains a high current transmission ratio.

Darlington output type - large current transfer ratio, can directly drive tens of milliampere loads. Grandson-in-waiting.

Thyristor old seepage transistor output type - the output part is a light-controlled thyristor, which is often used in the isolation driving occasion of AC high-power circuits.

The main role of the optocoupler in the IO interface:

1) Isolate the electrical connection of the circuit on both sides of the input and output of the photocoupler;

2) Convenient completion of signal level conversion.

Answer]: The main parameters that characterize the performance of an optical fiber coupler are insertion loss, thick finger plus loss, splitting ratio and isolation, or crosstalk.

1) Insertion loss li

Refers to the power loss introduced through one of the optical channels of the coupler.

2) Additional pickpocketing loss

Refers to the input power pi of a port

The number of decibels compared to the ratio of the power of each output port.

3) Crosstalk LC

Refers to the input power p1 from port 1

Power p2 leaked to port 2

The number of decibels of the ratio.

4) Splitting ratio or coupling ratio SR

Refers to the optical power pi of an output port (e.g., 3 or 4).

Ratio to the total output power of each port.

The optocoupler of the photocoupler circuit is carried out in a sealed shell, so it is not interfered with by external light. （）

a.That's right. b.Wrong calls, wrong signs.

Correct Answer: a

Performance characteristics of optocouplers.

The basic structure of the optocoupler is to connect the light emitter (infrared light-emitting diode. Infrared LED) and the chip of the photosensor (silicon photoelectric detection sensitive device) is encapsulated in the same shell, and is filled with transparent resin potting as the light transmission medium, usually the pin of the light emitter is used as the input end, and the pin of the photosensitive is used as the output end, when the input end is energized, the light signal emitted by the light emitter is projected to the photosensitive through the transparent resin light light guide medium, and is converted into an electrical signal output, realizes the electro-optical electrical signal conversion transmission with light as the medium, and is completely isolated electrically. The main performance characteristics of optocouplers are as follows:

The isolation performance is good, the input and output terminals are completely electrically isolated, and the insulation resistance RISO can generally reach more than 1010, and the insulation withstand voltage VISO can meet the requirements of use at low voltage, and the high withstand voltage can generally exceed LKV, and some can reach more than 10kV.

Optical signals are transmitted in one direction, and the output signal has no feedback to the input terminal, which can effectively block the electrical connection between circuits or systems, but does not cut off the signal transmission between them.

The optical signal is not subject to electromagnetic interference, and the work is stable and reliable.

It has strong anti-common-mode interference ability, which can well suppress interference and eliminate noise.

The spectral matching of optical emission and photosensitive devices is ideal, with fast response speed and high transmission efficiency.

Easy to connect with logic circuits.

No contacts. Long lifespan. Volumetric impact resistance.

Wide operating temperature range to meet industrial and military temperature standards.

From the application point of view, the optocoupler is required to have its own corresponding characteristics in different applications, the current transmission is larger than CTR, the linearity is good, the insulation voltage is high, the high speed and large capacity, the coupling efficiency (i.e. CTR) and isolation characteristics of the optocoupler are adjusted by voltage drop after conduction is its main attractiveness, and the product types developed can meet the needs of different occasions and improve the reliability of electronic circuits.

It has small size, long service life, wide operating temperature range, strong anti-interference performance, no contacts, and the input and output slide stool are electrically completely isolated. Spine.