Max. switching frequency of CRD300DA12E-XM3

jamini

Hi,

I have one question about CRD300DA12E-XM3.

What is maximum switching frequency of this converter in full load, 800V? mentioned max 80kHz, is it for full load?

Thank you

TBhatia

Hello, thank you for your message. A member of our technical team is looking into your questions and we will respond shortly. 

ChrisN

Hello jamini,

Thank you for your question. At full load, we recommend a maximum 20 kHz switching frequency, due to thermal limitations.

Referring to Figure 22 of the CAB450M12XM3 datasheet (shown below), which shows an inverter output current as a function of switching frequency, the module output current must be derated at higher switching frequencies due to thermals. In the figure, increasing the switching frequency from 20 kHz to 80 kHz reduces the module output current rating from approximately 375 A_rms to 175 A_rms. Furthermore, this plot is shown with an R_G(ext) of 0 Ω whereas the CRD300DA12E-XM3 reference design uses a 1 Ω resistor, so the current derating is expected to drop off more compared to this plot. Additionally, this analysis assumes the case temperature is consistently held at 90 °C or lower, which might not be true in all applications. To ensure reliable and consistent operation, we therefore recommend a maximum 20 kHz frequency while operating at full load. 

The 80 kHz maximum value described in the datasheet is derived from the gate drive circuit and represents the maximum switching frequency of the reference design at reduced load. The calculation for this frequency is found in the power estimates section of the CGD12HBXMP datasheet and shown below.

For the CRD300DA12E-XM3 reference design, the corresponding values are:

P_sw = 2 W (from the CGD12HBXMP datasheet)

Q_G = 1330 nC (from the CAB450M12XM3 datasheet)

Delta V_PS = (15 V - (-4 V)) = 19 V (from the CGD12HBXMP datasheet)

Rearranging to solve for F_sw results in the following:

F_sw = 2 / ((1330x10^(-9)*19) = ~80 kHz

 

However, as indicated before, this 80 kHz analysis does not consider the module thermals, and thus should only be considered in low-power operation. 

Thanks,

Chris N.

TBhatia

Hi, I hope that this answered your question. I will close this discussion for now but if you have a follow up question, please "Start a New Discussion" and we would be glad to support you further.