Optical coupler equipment (OCEP) is also called optoisolator or optocoupler, or optocoupler for short. It is to assemble light emitting devices (such as light-emitting diodes) and photosensitive devices (such as photosensitive triodes) together, and to realize coupling through light to form an electrical optical and optical electrical converter, so as to play the role of input, output and isolation. Next, we will briefly introduce the main parameters and classification of optocoupler. Let’s have a look!
Main parameters of optocoupler
- Reverse current IR: the current flowing through the diode when the specified reverse working voltage VR is applied to both ends of the tube under test.
- Reverse breakdown voltage VBR: the voltage drop between the two poles when the reverse current IR passed by the tube under test is the specified value.
- Forward voltage drop VF: the voltage drop between the positive and negative poles when the forward current passed by the diode is a specified value.
- Forward current IF: the current flowing through the diode when a certain forward voltage is applied to both ends of the tube under test. Junction capacitance CJ: capacitance value at both ends of the tube under test under specified bias voltage.
- Reverse breakdown voltage V (BR) CEO: the LED is open circuit, the collector current IC is the specified value, and the voltage drop between the collector and the emitter.
- Output saturation voltage drop VCE (sat): the voltage drop between collector and emitter when the LED operating current IF and collector current IC are specified values and IC/IF ≤ CTRmin (CTRmin is specified in the technical conditions of the tube under test) is maintained.
- Reverse cut-off current ICEO: when the LED is open circuit and the voltage between collector and emitter is the specified value, the current flowing through collector is the reverse cut-off current.
- Current transfer ratio CTR: when the operating voltage of the output tube is a specified value, the ratio of the output current to the forward current of the LED is the current transfer ratio CTR.
- Pulse rise time tr, fall time tf: under the specified working conditions of the optocoupler, the LED inputs the pulse wave of the specified current IFP, and the output terminal tube outputs the corresponding pulse wave, from 10% to 90% of the amplitude of the output pulse front edge, and the required time is the pulse rise time tr. From 90% to 10% of the output pulse trailing edge amplitude, the required time is the pulse falling time tf.
- Transmission delay time tPHL, tPLH: the time required from 50% of the leading edge amplitude of the input pulse to the time when the output pulse level drops to 1.5V is the transmission delay time tPHL. The time required from 50% of the amplitude of the rear edge of the input pulse to 1.5V of the output pulse level is the transmission delay time tPLH.
- Isolation capacitance CIO between input and output: capacitance value between input and output terminals of optocoupler.
- In out isolation resistance RIO: the insulation resistance value between the input end and the output end of the semiconductor optocoupler.
- Incoming and outgoing isolation voltage VIO: the insulation withstand voltage value between the input end and the output end of the optical coupler.