Expert Talk: Design a 24V Boost Converter in CCM mode

Open online SPICE simulator circuit link: learn_power_boost_24V_ccm_startup.tsc

Expert talk: how to design a Boost (step-up) Converter?

Use the boost (step-up) topology if the output voltage is required to be higher than the input voltage. It can
run in CCM (Continuous Conduction Mode) or DCM (Discontinuous Conduction Mode). The boost converter
is also used for active Power Factor Correction (PFC) to satisfy regulation requirements.

Output voltage V_out: higher than input voltage
Power rating P_out: up to 150 W or higher
Isolation: not available (if human accessible, V_in must be smaller than 42.5 V)

Continuous Conduction Mode (CCM)
Output voltage V_out= V_in/(1 - D); Duty cycle D= T_on/T with conducting pulse width T_on, switching period T
Current Ripple I_LR= ( (V_out - V_in) * (1 - D) * T)/L

Component Ratings
MOSFET voltage class V_DS= V_out
MOSFET current I_D= (2 * P_out)/V_in(min)
Diode voltage class V_R= V_out

Other Remarks
design for CCM to minimize the inductor peak current I_L
design for DCM to minimize the inductor value L

Example Converter
set your CCM converter spec in the Interpreter window on the left, click on Run to calculate the components and simulate it!
V_in= 12 V
V_out= 24 V (higher than V_in)
I_out= 1.5 A

Important Note (Disclaimer)
This is an idealized circuit for learning and experimental use. Test carefully when using calculated values for real hardware.


{1. click here to set application parameters}
{2. click on "Run" to calculate components}
{3. click on "OK" and Simulate Transient }

{Input voltage [V]}
V_in:= 12 {use 5... 40}
{Output voltage [V]}
V_out:= 24 {use higher than V_in}

{Output current [A]}
I_out:= 1.5 {use 1 .. 2}
R_load:= V_out/I_out

{=== Control settings: change with care ! ===}
{Switching frequency [Hz]}
fs:= 100k {use 100k .. 300k}
{Duty cycle}
Duty:= 1-(V_in/V_out)
L_INIT:= I_out/(1-Duty) {inductor DC value}
C_INIT:= V_out {capacitor DC value}
T_on:= Duty*T
{Calculate components for CCM}
L_crcm:= (R_load*Duty)*(1-Duty)^2/(2*fs)
L:= 2*L_crcm
R_crcm:= (2*fs*L)/(Duty*(1-Duty)^2)

Infineon MOSFET Finder,
\a(Power Selection Guide (PDF),
\a(PFC boost converter guide

Technical Assistance
Other circuits

Boost startup
Boost steady-state