Optocoupler, Magnetic Coupling, Capacitive Coupling

1. Principle: Optocouplers generally consist of three parts: light emission, light reception, and signal amplification. The input electrical signal drives the light-emitting diode (LED) to emit light of a certain wavelength, which is received by the photodetector and generates a photoelectric current. After further amplification, it is output. This completes the conversion of electricity, light, and electricity, thereby providing input and output isolation. Choose air and epoxy resin as isolation materials.
Advantages: Unidirectional signal transmission, electrical isolation, and strong anti-interference ability.
Disadvantages: High power consumption, easy aging and failure, large transmission delay, and large volume of LED. So for equipment with high reliability requirements [sensitive words], optocoupler isolation is not necessary.
2. Principle: Magnetic coupling is the isolation and transmission of signals through energy transfer through a magnetic field. Using the principle of transformers, current pulses pass through a coil to form a small local magnetic field, thereby generating inductance in another coil
Advantages: Fast speed [sensitive words] up to 150MBps, convenient application, high reliability, long lifespan, no need for power supply, magnetic isolation power consumption 10 to 100 times lower than optocouplers.
Disadvantages: The integrated transformer itself is a radiation source, which has EMI interference issues, higher power consumption than capacitive coupling, larger volume, and higher cost.
3. Principle: Capacitive coupling uses high-frequency signal modulation and demodulation to transmit the input signal through capacitor isolation. The signal has good tracking characteristics and superior performance.
Advantages: High communication speed, short signal transmission delay time, long service life, good resistance to EMI interference, good tracking characteristics, and low cost.
Disadvantages: Poor low-frequency characteristics and inconvenient integration of capacitive coupling.
Transformer isolation will be used as an isolation voltage generating device in the isolation transceiver chip; Optocoupler isolation and capacitor isolation are used in signal isolation circuits. When using, the selection of capacitance and resistance parameters in the circuit should refer to the user manual of the isolator. Improper selection can lead to functional defects or damage to the circuit.