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Desheng_Zhang
Level 1
Level 1
5 questions asked 5 replies posted 10 sign-ins

Hi, it is my first time to use SiC Mosfets and 2ED020I12-F2. And I have some questions, they may be basic but they are very important to me. I very much look forward to getting your response.
(1)In the example of EVAL_2ED020I12-F2, part of the schematic diagram is shown in Figure 3-3. The values of D2B and D3B are BAT165, and they are Schottky diodes after checking. But why are they drawn as zener diodes?
(2) Also in Figure 3-3, C3B is important in desaturation protection. In the example of EVAL_2ED020I12-F2, 2ED020I12-F2 is used to drive IGBT-IKP20N60H3, whose short circuit withstand time is 5 μs when VGE = 15V. Is the short circuit response time calculated as "Vdesat/Idesatc*C3B + Tdesatleb +Tdesatout = 9V/500μA*220pF + 400ns + 350ns = 4.71 μs" ? Then, since 4.71 μs is less than 5 μs, the design of C3B is reasonable. My question is, is the value of 220pF for C3B still reasonable when I use 2ED020I12-F2 to drive SiC Mosfet instead of IGBT? For example, when the short circuit withstand time of a certain type of SiC Mosfet is 3 μs, should the value of C3B be changed to 110pF so that the short circuit response time is 2.73μs?
(3) Also in Figure 3-3, RG1B and RG2B are designed to be 100 Ω, are their resistances too high? In the datasheet of IKP20N60H3, the recommended gate resistance is 14.6Ω.

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1 Solution

Hello,

Regarding short circuit time, it is better to reduce capacitor value to 110pF for detection because the value is chosen as per how much time you need to detect the desat.

Thanks and regards,

AZIZ

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2 Replies
喜马拉雅之雪
Employee

Hi Zhang:

For schottky diode symbol, this is from Baidu info. Would you like double check it?

_0-1682062807905.png

 

For short current protection delay time, my suggest is between turn "ON" delay time and short circuit limited.

Better setting is slightly longer than the turn "ON" delay.

For SiC MOSFET, the better delay is between 0.3~1uS.

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Hello,

Regarding short circuit time, it is better to reduce capacitor value to 110pF for detection because the value is chosen as per how much time you need to detect the desat.

Thanks and regards,

AZIZ

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