UCC25661: UCC25660 UCC25661

Hello,

This will work in Tina only ?

thanks 

regards

Hi Jchk,

We will use UCC25661x for LLC design, Is the simulation model "UCC25660x" you provide the same as ucc25661x? 

Thanks.

Hi Sir, 

Please refer below picture,

Ch1: Low side mosfet Vgs, Ch2: High side mosfet Vgs,

Could you help check what the Reason the effective duty cycle is to small?

I also upload excel file for the parameter of ucc256612. 

UCC25661x_Design_Calculator_Rev2.0.xlsx

Hi Jchk,

I understand, but my question is, the duty cycle of high-side and low-side vgs is only around 40% (dead time is large), how to adjust its duty cycle to be close to 50%?  

Thanks.  

HI Jchk, 

At no load @ 50V, the LLC converter operates in Burst Mode @ Vin 400V.

When the load increases to 2A @ 50V, the LLC exits Burst Mode and the  duty cycle is 40% until full load.

 Hi Jchk,

Please refer to the attachment, where Lr= 30uH, Lm=300uH and Cr:4.7nF+4.7nF, these parameters are fixed.

Thanks.

/cfs-file/__key/communityserver-discussions-components-files/196/LLC_5F00_TI.pdf

 JCHK Hi Jchk,

Do you have any suggestion about the design?

Thanks.

JCHK 

Hi Jckh, do you have any latest news or any information you need from me?

Thanks.

Hi Jchk, 

Vin:400V, Out:50V/4A Steady-state.

Picture1: CH2: High side VGS,  CH4: High side VDS 

Picture2:CH2: Low side VGS,  CH4: Low side VDS

the pulse width is around: 1.2us

And I also find the overshoot on the Vout, could you help to check?

Hi Jchk, 

Do you have any ideal about these issue?

Thanks.

Hi Jchk,

In the picture, the duty cycle is only 1.2 µs at 243.8 kHz, which means the duty cycle is around 30%.

Could you explain the reason and please provide the simulation results? I couldn’t reproduce the real test result in my simulation.   

The capacitor was 186uF, I increased it to 500uF, but it didn't help much with the overshoot.

Thanks.

Hi Jchk,

I understood, as we discussed early

Ch1: Low side mosfet Vgs (Ho), Ch2: High side mosfet Vgs(Lo),

The duty is around 30%~40% @ Vin:400V, Out:50V/4A Steady-state.

So, the duty cycle is small, but I don't know the reason.

Hi Jchk, JCHK 

This is exactly what I'm curious about — why is the dead-time so large?
How can I verify whether the dead-time value is correct?
I’d like to reduce the dead-time because the duty cycle is too small, which leads to low voltage utilization and prevents the LLC from operating at the expected resonant frequency.

Initially, I thought the smaller duty cycle was caused by the ZCS protection feature, but based on actual measurements, that doesn’t seem to be the case.

Could you provide more methods to help me confirm whether the duty cycle is indeed too small?
This could be a serious issue in the design.

Yellow color is :V_ISNS

Green color is : VGS of High side mosfet

Thanks.