STM32G474 buck BUCK

2020-02-25: Wrong selection of MOS driver in the first version,

2020-03-19: Version 2 gate driver not working.

2020-05-10: The third version is OK.

Need to make a buck module that can provide a maximum current of 10A

The input is powered by a 12V 3S lithium battery, and the output is expected to be 7.4V.

Then start calculating the inductance parameters :

ΔV=12-7.4=4.6V

The frequency is 100kHz, that is, f=100kHz

Duty cycle D=7.4/12=0.617

PWM period T=1/f=10us

MOS tube conduction time Ton=T*D=0.617*10us=6.17us in one cycle

The ripple coefficient is 0.3, then the ripple current is ΔI=0.3*10A=3A

The inductor withstands a potential difference of ΔV=4.6V, and the current rises ΔI=3A during Ton=6.17us.

The volt-ampere relationship formula of the inductor is as follows

dI=L*du/dt

Because the time is very short, the values ​​can be as follows

dI=3A

du=4.6V

dt=6.17us

Calculated L=4.37uH

Since the inductance of the inductor will decrease under the influence of DC bias current, an inductor with a larger inductance value can be selected for production.

Calculate capacitance parameters :

The average output voltage is 7.4V

Let the ripple voltage be within the range of 1%. By calculation, it is 0.07V.

According to the inductor current harmonics all enter Co, and the constant component enters the load calculation,

dU=1/8 *T*ΔI * 1/C

Set the values ​​for the above parameters

dU=0.07V

T=10us

ΔI=3A

Then it can be calculated that C=53.6uF

Documents for the car project:

https://www.yuque.com/haomingzi-syzrw/nngv9s/fohxs4