Power supply voltage u: it is the power supply voltage applied to the diode and current limiting resistor according to the transistor characteristic diagram, which is generally 120%~200% of the transistor breakdown voltage.
The breakdown voltage URB of diode is the voltage when diode breaks down, which is generally about 20% higher than the breakdown voltage of diode parameters.
Diode breakdown current IRB: the current flowing through the diode after diode breakdown. The breakdown current is generally greater than 10 times of the maximum leakage current. (But the reverse power consumption URB*IRB cannot be greater than 0/2 of the rated power consumption of 65438+ diode. )
Selection of current limiting resistor r: R~(U-URB)/IRB
Take 15SQ045 as an example:
Breakdown voltage URB: The actual breakdown voltage is about 55V, which varies from lamp to lamp.
Measurement power supply voltage u selection: according to the actual breakdown voltage, select the measurement power supply voltage of100V.
Selection of breakdown current IRB: The maximum breakdown current can be selected from 1 to 10 mA, such as 2mA.
Selection of current limiting resistor r: r ~ (u-urb)/IRB = (100-55)/2 = 22.5kΩ, and r can be selected in the range of10 ~ 50kΩ.
In actual measurement, the selection range of measuring power supply voltage U and current limiting resistance R is very large. The measured power supply voltage can be 100V or above 200V, because the voltage applied to the diode and current limiting resistor can be adjusted and increased slowly, and the pressurization can be stopped when the breakdown current is adjusted properly.