How can we judge the quality of optocouplers?

If the resistance value of 1-2 pins measured by the diode gear of the digital multimeter is about 750 ohms, and the meter pen does not respond, please ask whether this optocoupler is normal, (brand new).

Optocoupler. The main advantages of the combiner are: one-way signal transmission, the input and output terminals are completely electrically isolated and isolated, the output signal has no impact on the input end, the anti-interference ability is strong, the work is stable, there is no contact, the service life is long, and the transmission efficiency is high.

Optocoupler is a new type of device developed in the 70s, and has been widely used in electrical insulation, level shifting, interstage coupling, drive circuits, switching circuits, choppers, multivibrators, signal isolation, interstage isolation, pulse amplification circuits, digital instruments, long-distance signal transmission, pulse amplification, and solid-state relays.

SSR), instrumentation, communication equipment and microcomputer interfaces. In a monolithic switching power supply, a linear optocoupler can be used to form an optocoupler feedback circuit, which can change the duty cycle by adjusting the current at the control end.

Achieve the purpose of precision voltage regulation.

At present, what I have learned may be that only Beiyi Fiber is doing domestic military products, and it also cooperates with many industries, such as Huawei, ZTE, national defense, military industry, aviation, aerospace, weapons, ships, radar, electronics, nuclear industry, and nuclear industry.

Military, electric power, railway, transportation, communications, telecommunications, mobile, Unicom, national defense science and technology industry system in colleges and universities and research institutes, etc.!

Method: Use the PN junction of the digital multimeter to measure the end, the red pen "battery + pole" is connected to the "1" end of the optocoupler, and the black pen "battery-pole" is connected to the "2" end of the optocoupler (even if the light-emitting diode of the optocoupler is positively conducted), use another meter to measure the resistance of the "3" and "4" terminals, disconnect or turn on the input terminal (light-emitting diode end), and the resistance of the output end should change significantly, indicating that it is good to change the optocoupler. In addition, the multimeter at the LED end can be replaced by a battery string current-limiting resistor.

In the maintenance of switching power supplies such as color TVs and displays, if the optocoupler is damaged, it must be replaced by a linear optocoupler.

Commonly used 4-pin linear optocouplers are: TLP521, etc., commonly used 6-pin linear optocouplers are: TLP632, TLP532, PC614, PC714, PS2031, etc.

The commonly used 4n25 4n26 4n35 4n36 is not suitable for use in switching power supplies, because these four optocouplers are nonlinear optocouplers.

1. Use the multimeter ohm file to detect the light-emitting diode, anyway, measure the diode of the light-emitting diode, if the measurement value is small, and the other measurement resistance is very large, it means that it is a light-emitting diode and its pn junction is good, such as the two-pole of the light-emitting diode anyway, its resistance value is = 0, or the resistance value is very large, indicating that the diode of the light-emitting diode has broken down or has been broken (the piece has been broken). For example, the two poles of the light-emitting diode are small, and they may be two anti-parallel diodes. Then use the meter to detect the two poles of the phototriode, if the measured resistance value = 0 or very small, it means that the piece is broken.

2. Power-on inspection: when it is not determined that it has been damaged through the above inspection, two resistors (such as 1K) can be connected according to the above figure, and the voltage of R2 should be measured when the switch is not closed should be = 0, and when the switch K is closed, the voltage indication = 12V, it means that it is good here. If it still indicates = 0, then use a voltmeter to measure the voltage at both ends of the diode, such as the voltage at the two ends of the diode = 10v, the two poles of the diode can be reversed, and the voltage of the diode is also = 10v, indicating that this piece is broken.

If the voltage value is about or so, it means that the diode has been turned on and the transistor is reversed. The two poles of the transistor can be reversed, and then the R2 voltage is measured, if the indication = 10V, it means that the tube is good. If =0v is still indicated, the tube is bad.