Challenge

Project 3

Design and simulation of buck converter for auxiliary load in EV.

Buck converter:

Step down DC/DC converter which converts unregulated dc into regulated dc which is lower than the supply voltage.

Modes of operation:

when the switch is closed inductor current increase linearly till the switch is ON. Vs =Vo
when the switch is open inductor behaves like the current source current freewheels through the diode across Vo.

Given Data:

Input Voltage =48 v

output voltage =12 v

Load current = 10A

Calculations:

R = Vo/iL = 12/10 = 1.2 ohms

To determine the duty ratio

Duty Ratio = Vo /Vin = 12/48 =0.25 or 25%

To determine inductance value:

Assume the switching frequency is 40KHz

Lmin = (1-D)R /2f = (1-0.25)*1.2 /2 *40*10^3

=11.25 micro Henry

Assuming the inductance value is 25% higher for the inductor current to be continuous,

Lmin =(25/100)*11.25

= 14.06 microhenry

To determine Capacitance value:

C = (1-D) / (8*l*r*f^2)

=(1-0.25) / (8*14.06*10^-6*r*40*40*10^6)

Assume ripple to be 5%,

= 833 microFarad.

From the above-calculated parameters, we design a buck converter model below

Pulse Generator

Parameters entered based on calculated duty cycle and frequency

Inductance:

Capacitance:

Simulink Design of Buck converter:

Output:

We are getting voltage and current from the above waveform is

Ship work like this
in your own course.