Project 3
Aim:
Design and simulation of Buck converter for Auxiliary load in EV.
- Input voltage is 48V, Output voltage is 12 V
- Load current is 10A
- Calculate Duty ratio and Load(use Resistor as Load)
- Calculate L,C
Design:
From the given information
duty ratio=Vout/Vin *efficiency
we can take efficiency=92% and switching frequency=500000Hz
there fore duty ratio=12/48*0.92=27%
Load Resistance=Vout/Iout=12/10=1.2ohm
Inductor selection:
L=[Vout(Vin-Vout]/[delta IL*fs*Vin]
delta IL=(0.2-0.4)*Iout max
=0.2*10=2A
then L=12(48-12)/(2*500000*48)=9*10^-6Henry
Capacitance selection:
Cout=delta Iout^2*L/2*Vout*Vos
=8^2*9*10^-6/2*12*1.5
=1.6*10^-5Farad
Simulation of Buck converter is done as shown above
Block used:Battery,Pulse generator,MOSFET,Diode,Inductance,Capacitance,Resistance Current measurement,voltage measurement,scope and power gui
Battery:Battery is used to provide input dc voltage of 48V
Pulse generator:In pulse generator we set switching fequency 500000Hz and pulse width27% and fed to MOSFET
MOSFET:We use mosfet as switching device here and keep the defaukt paramter
Diode:kept the diode parameter same
Capacitance:capacitance value set to 2.5*10^-9 F
Inductance:Inductance value set to 9*10^-6 Henery
Resistance:Resistance value set as 1.2ohms
Working:
The switch turns on and lets current flow to the output capacitor, charging it up. Since the voltage across the capacitor cannot rise instantly, and since the inductor limits the charging current, the voltage across the cap during the switching cycle is not the full voltage of the power source.The switch now turns off. Since the current in an inductor cannot change suddenly, the inductor creates a voltage across it. This voltage is allowed to charge the capacitor and power the load through the diode when the switch is turned off, maintaining current output current throughout the switching cycle.
Result:
The above graph shows the output of buck converter ,The output voltage =12V and load current=10A for the input of 48V
Conclusion:The buck converter is designed and simulated in simulink for 1 sec we gave 48 V dc input and got 12V dc output.