I want to choose a TVS to protect the PFC mos tube. The PFC outputs a constant 390VDC, the starting overshoot will reach 420VDC, and the power is 1200W. Now I am distressed to choose this TVS. Baidu has a look at the TVS related information, there are several parameters:
1. Vrwm
2. Vbr.min / Vbr.max
3. Vc
I would like to ask, which parameter should I use as a design reference?
Raphael Posted on December 9, 2020
Transient voltage suppression diodes have nominal voltages, clamp minimum voltages and maximum voltages. The voltage of the circuit during normal operation (the voltage that does not need to be clamped) is lower than the minimum clamped voltage, and the peak of the circuit The impulse voltage is less than the maximum voltage of the clamp. Except for unclamped, which is equivalent to ordinary diodes, this parameter is required to install ordinary diodes. When clamping is also required, if the circuit is working normally, the working time of the clamped state is relatively long, and power consumption needs to be considered.
Alvin Posted on December 9, 2020
The following points should be paid attention to when selecting TVS tube:
• Determine the maximum DC or continuous operating voltage of the protected circuit, the rated standard voltage of the circuit and the "high end" tolerance.
• TVS rated reverse shutdown VWM should be greater than or equal to the maximum working voltage of the protected circuit. If the selected VWM is too low, the device may enter an avalanche or the normal operation of the circuit may be affected by too much reverse leakage current. Serial connection of sub-voltage, parallel connection of sub-current.
• The maximum clamping voltage VC of the TVS should be less than the damage voltage of the protected circuit.
• Within the specified pulse duration, the maximum peak pulse power PM of the TVS must be greater than the peak pulse power that may appear in the protected circuit. After determining the maximum clamping voltage, its peak pulse current should be greater than the transient surge current.
• For the protection of the data interface circuit, attention must also be paid to selecting TVS devices with suitable capacitance C.
• Select the polarity and package structure of the TVS according to the application. It is more reasonable to choose bipolar TVS for AC circuit; it is more advantageous to choose TVS array for multi-line protection.
Melvin Posted on December 9, 2020
Why do I need to choose TVS protection for PFC MOSFET? This is the first time I heard of such an application. According to my understanding, the PFC output has a large energy storage capacitor, which is enough to absorb huge transient peak power. Usually the withstand voltage of PFC MOSFET is 500 or 600V. Even without TVS, there is no danger.
