lt8330

Hi!

LT8330, documentation p.17 has a reference circuit of 48V Boost Converter.

Duty cycle is ~94%. A max allowed duty cycle is ~84% even for 65 ns On-Time.

Is this circuit correct?

The table defines On-Time for Vin = 24V.

If On-Time has another value for Vin = 3V, where can I find this value?

Parents
  • Thank you for the post.

    The reference circuit mentioned above (3V - 6V input to 48VOUT) operates in discontinuous conduction mode (DCM), so the duty cycle calculation D = (VOUT - VIN)/VOUT for continuous conduction mode (CCM) is not applicable.  To determine the duty cycle for DCM, the first step is to determine the charge in the inductor during the switch off time: q ~ IOUT/(fsw*efficiency).  Once q is determined, I(PK) is determined and ton can be determined using I(PK).  I will leave this as an exercise but the exercise should show that the minimum on time of the switch is not exceeded.

    Minimum on time should not vary much with input voltage.

Reply
  • Thank you for the post.

    The reference circuit mentioned above (3V - 6V input to 48VOUT) operates in discontinuous conduction mode (DCM), so the duty cycle calculation D = (VOUT - VIN)/VOUT for continuous conduction mode (CCM) is not applicable.  To determine the duty cycle for DCM, the first step is to determine the charge in the inductor during the switch off time: q ~ IOUT/(fsw*efficiency).  Once q is determined, I(PK) is determined and ton can be determined using I(PK).  I will leave this as an exercise but the exercise should show that the minimum on time of the switch is not exceeded.

    Minimum on time should not vary much with input voltage.

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