The total loss of the boost converter (P_TOTAL) can be expressed as the sum of the losses in the device (P_IC), MOSFET power losses (P_Q), diode power losses (P_D), inductor power losses (P_L), and the loss in the sense resistor (P_RS).

Equation 29.

P_IC can be separated into gate driving loss (P_G) and the losses caused by quiescent current (P_IQ).

Equation 30.

Each power loss is approximately calculated as follows:

Equation 31.

Equation 32.

For I_BIAS values in each mode, see the LM5156 data sheet.

P_Q can be separated into switching loss (P_Q(SW)) and conduction loss (P_Q(COND)).

Equation 33.

Each power loss is approximately calculated as follows:

Equation 34.

t_R and t_F are the rise and fall times of the low-side N-channel MOSFET device. I_SUPPLY is the input supply current of the boost converter.

Equation 35.

R_DS(on) is the on-resistance of the MOSFET and is specified in the MOSFET data sheet. Consider the R_DS(on) increase due to self-heating.

P_D can be separated into diode conduction loss (P_VF) and reverse recovery loss (P_RR).

Equation 36.

Each power loss is approximately calculated as follows:

Equation 37.

Equation 38.

Q_RR is the reverse recovery charge of the diode and is specified in the diode data sheet. Reverse recovery characteristics of the diode strongly affect efficiency, especially when the load voltage is high.

P_L is the sum of DCR loss (P_DCR) and AC core loss (P_AC). DCR is the DC resistance of inductor which is mentioned in the inductor data sheet.

Equation 39.

Each power loss is approximately calculated as follows:

Equation 40.

Equation 41.

Equation 42.

∆I is the peak-to-peak inductor current ripple. K, α, and β are core dependent factors which can be provided by the inductor manufacturer.

P_RS is calculated as follows:

Equation 43.

Efficiency of the power converter can be estimated as follows:

Equation 44.