Project 3

Project

AIM: Design and simulation of buck converter For Uxiliary load in EV.

. Input Voltage is 48V , Output voltage is , 12V.

. Output Current is 5A.

. Calculate the duty ratio and load (use resistor as load)

. calculate LC

Introduction :

A step down DC/DC converter is a device capable of convertering an unregulated input voltage into an regulated output voltage lower than the input voltage .

A buck converter step down the applied DC input voltage level directly . By directly mean that converter is non isolated DC converter non isolated converters are ideal for all board level circuit where local converter is required fax machine Scanner cellphone PACs computer copiers are all example of board level circuit where converson may required at any level inside the circuit . Hance a buck converter the DC level of input voltage into other requirement levels.

This buck converter having following controlling unit

1) Switching Power Sulpply unit which can turn ON/OFF Switching element that can be turened ON/OFF at high frequency to convert a DC Input voltage Vin into a Output volatage Vout.

2) Controll unit Whiich is used to controll the ON/OFF opration of the switching element . We use MOSFET as switching element where the pulse generation is a control unit for MOSFET.

3) Inductor It is store the energy during ON Period & dissipate during OFF period .

4) Capaciyor It bypass the ripple content in the output voltage .

5) Freewheeling Diode It freewheel the current throught thee ressitor from the inductor & circuilate it in circuit durong OFF period

6) Load resistor Accross it we can mesure the output voltage & current Throught It

Calculate;

Given Data

Input Voltage Vin = 48V

Output voltage Vout = 12V

Output current = 5A

Find

Vout = R*iL

R = Vout/iL

R = 12/5

R = 2.4 oh

Duty ratio = Vout/Vin

Duty ratio = 12/48

Duty ratio = 0.25

Let us calculate for 30% ripple in the inductor current

Delta IL = 0.3*5 = 1.5A

We know that

Inductor L = Vout*1-D/Fs *DeltaIL

L = 12*0.75/50*1.5 = 0.12mH

Similarly

Cout = 1-D/8L*Fs^2*DeltaVout

= 0.75/8*0.12*50*50*0.05

= 6.25MicroH

1) DC Voltage Source:

This Block used for the input providing 48V . the DC voltage source block represented a constant voltage source whose output voltage value is independant of the current throught the source here we are talking 48V pf input voltage

2) Diode

Implement a diode in parallel with a series RC snuber circit in on state the diode model has an internal resistance and inductance for most application . the internal inductance should be set to zero . the diode impedence is ifinite in off state mode.

3) Switching transistor :

MOSFET and internal diode in parllel with a series RC Snuber circuit . When a gate signal is applied the mosfet conductor and act as a resistance in both direction if the gate signal falls to zero when the current negative the current is transfered to the antiparllel diode .

4) Capacitor:

This block is used for the storage of the electric energy for providing output voltage when required .

Conclusion ;

We have design and simultion of buck converter for ausiliary load in Ev

And also we have calculate duty ratio and load resistor and lc value.