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UCC25660: UCC25660_Fault condition

Manimuthu Palanivel
Prodigy 70 points
Part Number: UCC25660

Dear team,

I am writing to inquire about a specific aspect of the UCC25660 LLC controller that we are currently using in our system.

We employ the UCC25660 in a half-bridge LLC configuration with a fixed input voltage of 360VDC and an output voltage of 600VDC. The capacitance of the secondary winding of the transformer is estimated to be within the range of 1nF to 2nF. Given the transformer ratio of 1:4, this capacitance is reflected on the primary side, magnified by N^2 times (16 times). In this condition, under no load, mid-load, and light-load, the capacitance appears to dominate rather than the resistive load.

In the UCC25660 datasheet, it is stated that "In the event of a persistent ZCS condition, the controller ceases switching action and moves to the fault state. A configurable time-out is used to declare a persistent ZCS fault condition."

However, our specific requirement is to avoid entering the fault condition altogether. Instead, we aim for the controller to tolerate persistent ZCS conditions for an indefinite number of cycles.

Could you please provide guidance or suggestions on how we can achieve this requirement using the UCC25660 controller? Any insights or recommendations regarding configuration settings or external components that can help us meet our objective would be greatly appreciated.


Best regards,

Manimuthu

  • 0
    TI__Genius 13245 points

    Hi Manimuthu,

    You can try increasing the ISNS value to avoid the zero crossing at the time of switch turn off. 

    Manimuthu Palanivel said:
    However, our specific requirement is to avoid entering the fault condition altogether. Instead, we aim for the controller to tolerate persistent ZCS conditions for an indefinite number of cycles.

    All the current variants by default comes with ZCS fault enable. Could you let me know how many UCC25660x controllers you would need for each year. If it's a good amount, we can have the controller with ZCS fault disable by changing internal OTP settings. But I will have to talk with my management regarding this.

    Regards

    Manikanta P

  • 0 in reply to Manikanta Pallantla
    Prodigy 70 points

    Hi Manikanta,

    Thank you for your response.


    1. Is there any option is available to disable using external components?

    2. Is there any option to reduce the fault recovery time?


    3. Is there any alternate part you could suggest for our application?


    Currently we are working on Proto system. In production, 500 Qty may be required per year.

    Best regards,

    Manimuthu

  • 0 in reply to Manimuthu Palanivel
    TI__Genius 13245 points

    Hi Manimuthu,

    All our charge mode controllers does comes with the ZCS protection. Also, there is no way to change the fault protection time or by using external components. 

    You could use UCC25600 which doesn't have ZCS protection.

    Regards

    Manikanta P