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Opto-coupler is an electrical component that can be used to transfer electrical signals while remaining isolated from each other. This isolation is important because the two circuits being bridged may have different voltage potential or they may produce electromagnetic interference that would interfere with other parts of the circuit.
Optocouplers are similar to a transistor in that they operate based on the principle of photovoltaic effect; but unlike transistors, optocouplers require light as one of their inputs. Curious about what an optocoupler IC does, its applications, and which optocoupler is suitable for your application? Keep reading to find out everything you need to know.
- 1 What is the role of an IC in an optocoupler?
- 2 How do these ICs in optocouplers work?
- 3 Types of optocoupler ICs
- 4 Key features of optocoupler IC
- 5 Applications of optocouplers IC
- 6 Limitations of an Optocoupler
- 7 Guidelines for installing optocoupler IC
- 8 Benefits of optocoupler ICs
- 9 Optocoupler IC specifications
- 10 Choose a reputable optocoupler IC manufacturer
What is the role of an IC in an optocoupler?
In an optocoupler, integrated circuits are used to control the light-emitting diode (LED) and the phototransistor. The ICs are used to detect the current flow in the LED and to regulate it appropriately. Most optocouplers use a single IC that includes both an LED driver and a phototransistor driver.
How do these ICs in optocouplers work?
Like in most devices, the working mechanism of IC remains the same. The IC will first receive an input signal, which is then converted into a binary code.
This code will be sent to the LED driver or the phototransistor driver depending on what kind of optocoupler you have. The LED driver will then produce light while the phototransistor driver controls the current flow in the LED.
Types of optocoupler ICs
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The integrated circuits build for optocouplers are designed according to the type of optocouplers.
This implies that there are four main types of ICs used in optocouplers:
As the name suggests, this type of IC is mainly found in photo-transistor optocouplers. These ICs are designed to protect the photo-transistor from high current and excessive voltage. The IC will also provide a constant current flow to the photo-transistor.
Photo-darlington optocoupler IC
Photo-darlington ICs are used in photo-darlington optocouplers. Photo-darsopn optocouplers have two LEDs that they use to regulate a current flow. A photo-darlington IC is used to regulate this flow of current in these types of optocouplers.
This type of IC is named after the inventor, which is Charles H. Dyson, who invented this type of optocoupler in 1959, which was first called as the DYSON TRIPLEXER.
The main role of the photo-darlington IC is to regulate both LEDs with a single phototransistor while at the same time protecting it from high voltage and currents.
The most commonly used circuit for this type of IC is usually a serial circuit, which uses two transistors for each channel (one for each LED). This means that there are three transistors involved in total: one for each LED and one for regulating them both together (the third transistor).
Photo-SCR optocoupler IC
A photo-SCR is used in a photovoltaic cell. Photo-SCR is a type of thyristor that has two functions: it can be used to control the voltage and current at the same time. This can be used in solar panels or other DC applications where high voltage and low current are required.
The main role of the photo-SCR is to convert high voltage into lower voltages, which can then be controlled by a transistor.
The photo-SCR is usually made up of two transistors: one transistor for controlling the voltage and another transistor that converts the low voltages into higher voltages .
Photo-TRIAC optocoupler IC
This type of IC is used in the photo TRIAC optocouplers. A TRIAC is a thyristor (or two-way switch) used for AC power conversion. It is especially used in power generation and distribution systems, where high voltage AC current must be converted to low voltage DC current.
Key features of optocoupler IC
– Isolation – Optocouplers are designed to separate or isolate the input from the output circuits. They are isolated from each other via an optical barrier. This barrier ensures the two circuits remain isolated from each other even if the current through one circuit changes enough to affect the other circuit. The barrier is transparent to incoming light, but reflects outgoing current. This allows the circuits to be connected without being dependent on the voltages of the circuits being matched. – Selective coupling
– An optocoupler IC can be set up to be either normally closed or normally open. Normally closed means it will be closed when the input is open and open when the input is closed. Normally open is the opposite of normally closed. A normally open optocoupler is usually used when a circuit has to be isolated when it is off. This prevents the input of the circuit from drawing current from the battery when the circuit is not in use. – Turn-on voltage
– Optocouplers are designed to detect a change in voltage and transfer the input current to the output. However, they do not immediately do this when they are energized. Instead, they have a turn-on voltage that must be reached before they start to transfer the input to the output. This voltage is usually between 2 and 5 volts.
– Turn-off voltage – When the input current to the optocoupler changes, turning off the voltage, the output current will stay in the output circuit until the turn-off voltage is reached. This voltage is usually between 2 and 5 volts.
– Isolation protection – An optoisolator provides isolation protection against both transient voltages and electromagnetic interference. The input and output circuits are protected from each other by the air gap between their two halves.
– The breakdown voltage of an optocoupler IC is the minimum voltage that can be applied to the input circuit while still allowing the output to deliver its rated current.
– The isolation resistance of an optocoupler IC is the maximum voltage that can be applied to the input circuit without affecting the output.
– The optical power of an optocoupler is equal to its current rating multiplied by a factor that depends on its type and also on whether it is a differential or common mode device.
In general, optical power decreases with increasing light intensity, whereas current decreases with increasing intensity.
Applications of optocouplers IC
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Data communication is one of the most popular applications of optocoupler ICs. Optical communication uses light signals to transfer data between computers, telephone lines, satellites, and more. By using an optocoupler instead of a simple diode, electrical interference from the power supply is prevented from interfering with the communication.
Optocoupler ICs can be used as sensors that detect light and transfer the signal to an electrical current. For example, they are often used in security systems to detect when a room is lit or dark.
Optocouplers can be used to switch electrical power. A circuit is turned on when light is allowed to pass through the receptor and turned off when light is prevented from reaching the receptor.
Power supply regulation
Optocoupler ICs are often used to regulate the amount of power that is supplied to a circuit.
A large amount of power can be provided to a circuit, but when the light intensity is too low, the light cannot reach the receptor and the circuit is switched off.
Similarly, when light intensity is too high, there will be an excess of current that cannot flow through the optocoupler and will cause overheating.
Optocouplers are frequently used to switch the signals of microprocessors and other digital devices.
This is because optocouplers have a high input impedance that prevents the switching of the digital device from causing noise, and also because there are few moving parts that can fail.
Optocouplers are used in optical isolators to prevent light from reaching one device when it is intended for another device. This prevents damage to the devices and ensures that they operate at their optimal performance levels.
Limitations of an Optocoupler
– Voltage ratings – As with any electrical component, optocouplers have voltage ratings. The voltage rating is the highest voltage that a particular optocoupler can have applied to it without becoming damaged. If you exceed this voltage, the optocoupler could be destroyed, causing damage to other electrical components that it is connected to.
– EMI/RFI – An optocoupler has a limited ability to protect a circuit from electromagnetic interference (EMI) and radio frequency interference (RFI). It can help to protect the circuit from a nearby source of EMI or RFI, but it will not help to protect against a source that is further away.
Guidelines for installing optocoupler IC
Before installing the optocoupler, you should be aware of the voltages of the inputs and outputs of the components that will be connected to the circuit. These voltages should be within the specified voltages of the optocoupler.
You should also note the type of connection between the components. It is also important to note that the leads of the components are usually color-coded.
Route the input and output to the corresponding leads of the optocoupler and connect the leads according to the circuit diagram.
Also, follow the IC manufacturer’s instructions when installing and configuring the IC to the optocoupler.
Benefits of optocoupler ICs
Why should optocouplers have specialty integrated circuits? Here are the top benefits of using these ICs.
-Easy to install: Since the IC is small, you do not have to worry about installing it in a circuit that has many components, especially if you are not an electrical engineer.
-Reliable: These ICs work reliably under all conditions. They have programmable functions that help them to work efficiently.
-High performance: The ICs for optocouplers have very high performance with high speed and low power consumption. You will not need to worry about the reliability of your system failing because of these ICs failing or not working right if they are used correctly.
-Compact size: The ICs for optocouplers are small in size making them easy to install in a compact space such as on a circuit board or inside another electronic device.
This size also makes them easy to work with, especially when designing and building the optocoupler.
-Low cost: The ICs for optocouplers use less power than other types of circuits used by other electronic devices so they require less energy from batteries or power sources and therefore lower your energy bill. Also, you can get affordable optocoupler ICs from reputable manufacturers and suppliers.
-Customizable: You can easily customize the optocoupler ICs. For example, you can change the value of the resistor used in the optocoupler so that it has a different resistance value.
You can also change the number of optocouplers used in a circuit so you can use more or fewer optocouplers as needed.
Optocoupler IC specifications
Here are vital specifications that you should know before you proceed to buy an optocoupler integrated circuit.
-Output-input current ratio: This value defines the ratio of current transfer between the output end of the coupler and the input end. This value usually depends on son the emitter-collector voltage in case you are using a photo-transistor optocoupler
-LED forward voltage- This is the power that is required to turn on the LED of an optocoupler. It is usually matched with the trigger current of an optocoupler.
-Forward voltage: This is the voltage that is required to turn on the LED of an optocoupler. It is usually matched with the trigger current of an optocoupler.
-Optocoupler temperature coefficient: This value defines how the output voltage changes when operating at different temperatures.
-Output capacitance: This value defines how many electrons can be stored by a capacitor in case you are using a photo-transistor optocoupler.
-Input capacitance: This value defines how many electrons can be stored by a capacitor in case you are using a photo-transistor optocoupler.
Choose a reputable optocoupler IC manufacturer
So, where should I buy optocoupler ICs for my project?
The best place to buy is from reputable and reliable manufacturers and suppliers.
This way, you can be sure that the optocoupler IC will work as it is supposed to.
Another important thing to keep in mind when looking for optocoupler ICs is that you should buy from manufacturers who are well-known in the market.
And we at ICRFQ can help you find those manufacturers. As a sourcing agent, our main task is to buy electronic components from reputable brands in China.
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