Project 3

ans- Aim- Basically the project developed for Ev used auxillary load for this we need convertor so we developed DC-DC convertor a step- down the voltage provide supply to the auxilllary load (Radio, horn,accessories, etc.)

Given Data

Vin= 48v

Vout=12v

Output current=10A

inductor current ripple is less than 30%of the average inductor current output voltage ripple of the capacitor is less than 5%

Step1- Draw a circuit schematic diagram of the buck convertor

In this circuit we used input voltage , one power switch (Mosfet, IGBT), inductor coil,capacitor, diode, resistance load in this

circuit working in two mode this circuit will work switch on and switch off

Mode 1-Switch ON, diode off

Circuit below

Working of this circuit

When we start supply switch is ON. then supply goes to the inductor coil energies with polities + to- and then goes to the

resistance load the back to supply voltage and circuit complete and also capacitor also charged in this circuit Diode stop to

flow current due to anode side is - and cathode side is + its work like reversed Biased

Mode2- Switch Off and Diode ON

Circuit Below

Working of this circuit

When we switch off supply stop and when switch is on that time our inductor coil is charged now switch is off that inductor start discharging but changes the polarity of inductor coil and jsut because of diode gets anode side geta+ and cathode side we get- so diode also start conducting supply inductor coil through then resistance load and capacitor and diode through complete the circuit like this circuit work.

Calculation part

VL(on)*Tan+VL(OFF)*TOFF=0

(VS-VO)*Dt+(-vo)*(1-D)*T=0

Vo=DVS

D=VO/VS

D=12/48 =0.25

0.25 duty cycle

Vout= Iout*R

R=Vout/Iout

R=12/10=1.2 ohm

Then let us design for 30%ripple in the inductor

Delta IL= 30/100*10=3A

find the inductor

L=Vout(1-D)/Fs*Delta*IL

L=12*(0.25)/50*3=0.06mh

C=1-d/8-L*Fs*(Delta Vo/Vo)

C=0.75/8*0.06*50^2*0.05

C=0.0125

C=12.5mf

R=1.2ohm

D=25%

Now simulate the circuit simulation

Now design this circuit with the help of DC VOLTAGE supply connect with Mosfet switch for controlling the voltage for switch we used PWM generator to generate the PWM so we controlled the voltage we used

inductor coil in series and capacitor across the Resistance load and diode and with help of voltage measurement we used for the measure the voltage.

Output voltage graph

peak current of diode is 10.1A

peak current of MOSFET is 11.1A

peak voltage of diode is 0.7V

peak voltage of Mosfet is 49.3v

conclusion- With the buck convertor we step down the input voltage and given to voltage to the auxillary load smoothly we can say this is the DC-DC convertor