TIDM-02002: Power Losses in the C3M0030090K SiC MOSFET

Abdalla, 

Let me connect this thread to Wolfspeed team for best recommendation on their part for these topologies. As I am not an expert in SiC.

As CLLLC is completely soft switching on this design our estimate was as below, purely on conduction losses/  

V2 = 300V                    →   Ipri= 22 Amps RMS → Pcond = 22^2 * 0.065 = 31.46 , At a given time 2 switches are conducting

hence Pcond_sec_total= 31.46*2 = 62.92

Hence total losses on all switches: 87.498 W

-Manish

Hi Abdalla,

I am part of the Wolfspeed team.  Thank you for the question and considering our SiC MOSFETs for your design.  I wanted to let you know that I am looking into your question and I will get back to you with a more detailed answer in the next day or two.  In the mean time, have you looked at our SpeedFit design simulator (https://www.wolfspeed.com/speedfit) ?  It can help you quickly assess different topologies, devices, and cooling requirements early in a design.  

Thanks for your patience.

-Adam

Manish,

Thanks for your response.

To get clearly
For these parameters
VSEC = 300 V
Ipri= 6.6KW / 300V =22 Amps RMS
we get
conduction losses for
Secondary:
Pcond_sec_total = 31.46*2 = 62.92 W
Total :
Total losses on all switches = 87.498 W

how you calculated the Pcond_prim_total to be =24.578 W?
Note that VPRIM =380 V @ 3.3-kW [TIDM-02008]
if the output power reduced to =3.3kw for the on [TIDM-02002] DC-DC converter

According to the Test Results (Design Guide: TIDM-02002, 3.2.3 @ Page 71)

VPRIM =378.08 V
VSEC =280.06 V
Pout = 3304.4 W

conduction losses  
VSEC = 280.06 V
Ipri= 3304.4W / 280.06V =11.79 Amps RMS
Pcond = 11.79^2 * 0.065 = 9.03W
Pcond_sec_total = 9.03*2 = 18.07 W

(please advise if I misunderstanding)

thanks in advance
Abdalla,

Hi Adam,
Thanks for your response

Can I know the thermal parameters (Rcs, Rsa, and Tambient) that you used to get these results?

If I use two [TIDM-02008] in parallel to get 380V@6.6kW
For these new operating point (380V in, 280V 6.6kW out, 500kHz Fres)
Rth,ch = 3.73 °C/W
Rth,ha =1.2 °C/W

what is the suitable alternate part you advise?

C3M0030090K
C3M0060065K
C3M0065100K

Wish you a Nice Day.
Best Regards,
Abdalla Saad

Hi Abdalla,

I used a 50C fixed baseplate temperature and 0.5C/W RCH, which would correspond to a high-performing grease.  Admittedly this represents a very aggressive cooling system, but for the sake of relative comparison between parts is sufficient.  Using the numbers that you provided, it looks like your best option may be to parallel 2 parts.  May I ask what you are using for the case-to-heatsink interface, the thermal impedance of that joint seems high even for an isolated pad.  

Thanks,

Adam

Hi Adam,
Thanks for your response

For the heat sink:
A 30-mm×30-mm×25-mm push-pin heat sink Part number [UBM30-25BP-1P08] from Alpha Company Ltd at 600-LFM Forced Air Cooling.
The Heat Sink thermal resistance is (Rθhs) approximately 1.2°C/W

For the TIM:
GR-45A Gap filling pad Part number [ GR-45A-E0-100-BL- 30x30 mm] from Fujipoly with PET film on one surface to facilitate Electric Isolation, with this Tim along with the push-pin heat sink.
The TIM thermal resistance is (RθTIM) approximately 3.2°C/W

May I ask for your e-mail for further support?
Best Regards,
Abdalla Saad

Abdalla,

You can take the conversation offline with Adam as needed, i will not recommend posting direct email ID In the thread here.

As the question is resolved i will close this thread.

-Manish 

Manish,

Ok, I'm understanding.
I'm waiting for Adam's Feedback.

Thank you for understanding
Wish you a Nice Day.
Best Regards,
Abdalla Saad