Boost calculations


1. Minimum needed inductance
2. Check for continuous or discontinuous mode
3. On- and off-time
4. Voltages and currents on components
5. General calculations




1. Minimum needed inductance

    The calculation is done with the minimum input voltage to achieve the desired current ripple in continuous conduction mode.


    Peak-to-peak inductor current ripple


    Minimum needed inductance at minimum input voltage




2. Check for continuous or discontinuous mode

    It has to be checked if the boost converter is working in continuous or discontinuous mode to use the proper formulas.


    Maximum input current


    Current ripple with choosen indcutance


    Check for continuous or discontinuous mode



3. On- and off-time

    Depending on the mode (continuous or discontinuous) different formulas are needed.


    ton       - FET is in on-state (continuous and discontinuous mode)
               - Inductor current is rising

    toff       - FET is in off-state (
continuous and discontinuous mode)
               - Inductor current is falling

    tzero     - time slot when inductor current is zero
               - occurs only in discontinuous conduction mode


    Duty cycle



    On-time is continuous conduction mode


    Off-time in continuous condcution mode



    On-time is discontinuous conduction mode


    Off-time in discontinuous condcution mode



    Time slot when inductor current is zero (only in discontinuous condcution mode)



4. Voltages and currents on components

    Depending on the mode (continuous or discontinuous) different formulas are needed.


    Minimum current in continuous conduction mode (FET, diode, inductor)


    Maximum current in continuous conduction mode (FET, diode,
inductor)


    Minimum current in discontinuous conduction mode (FET, diode, inductor)


    Maximum current in discontinuous conduction mode (FET, diode,
inductor)


    4.1 FET specific calculations

    Average FET current


    RMS FET current



    Minimum FET voltage


    Maximum FET voltage



    FET voltage in discontinuous conduction mode when the inductor current is zero


    4.2 Diode specific calculations

    Average diode current


    RMS diode current



    Minimum diode voltage


    Maximum diode voltage



    Diode voltage in discontinuous conduction mode when the inductor current is zero


    4.3 Inductor specific calculations

    Average inductor current


    RMS inductor current



    Minimum inductor voltage


    Maximum inductor voltage



    Diode voltage in discontinuous conduction mode when the inductor current is zero



5. General calculations

    Diode losses


    Output power



    Input power


    Input current