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UCC27712: UCC27712 gate driver with 100% duty cycle

Part Number: UCC27712
Other Parts Discussed in Thread: SM72445,

Dear Experts,

I am designing a solar charger with SM72445 that charges 48V batteries. The input range of the solar cells varies from 30V to 180V so it means that

1:1 (100% duty cycle) can happen when the input is around the output charging voltage (2% variation based on the datasheet of the SM72445).

The question is that how the SM72445 will toggle the output low side switch mosfets in 100% to keep the two high side mosfets on during this bypass mode?

I am asking this question because UCC27712 drivers can work in 100% duty cycle but the control has to make sure that the low side fets are toggled

with a certain frequency so the bootstrap supply (Voltage on HB-HS) of the high side nmos driver recharges periodically and does not fall below uvlo.

Thanks and regards,


  • Hello,

    Our office is closed Monday for the US Martin Luther King, Jr holiday. We will get back with you on your question early next week.

    Best regards, Don

  • Hello Andras,

    Your assessment of the limitation of the bootstrap bias is correct, regarding that the low side driver has to be switched periodically to ensure the boot capacitor is recharged. We are the experts on the gate drivers and can assist with those issues and questions. I think your question is more on the details of the SM72445 controller PWM signals. 

    To get your question to the correct expert on that part, I would suggest posing this same question but title the thread with the SM72445 part number. I am going to go ahead and close this thread.