Project 2

I have chosen the first question.

1. Design an interleaving DC/DC converter system for a data centre application with the following specifications:

• Input voltage: 45 – 60V
• Output voltage: 3V
• Output current: 100A
• Efficiency > 85% (extra credit for efficiency higher than 90% on a spice-based software simulation tool)

Simulate the system using a Spice-based software simulation tool such as LT-Spice, Pspice, PowerSim, TINA, etc.

Show your design in detail (you will probably need to use an isolated system to achieve this low voltage conversion ratio; you might also need to use a multiphase system to increase the efficiency).

Show the input voltage, the output voltage, the input current, the output current, the system efficiency and any other simulation plots necessary to evaluate your design. 

Ans.

Given:

Vin = 45 - 60V
Vo = 3V
Io = 100A
η = 90%

Power = Vo x Io = 3 x 100 = 300 W

Let us assume that we will design for a 50% duty cycle.

For Vin = 45V

Then, we will choose

N1 = 600 turns
N2 = 80 turns

For Vin = 60V

Then, we will choose

N1 = 600 turns
N2 = 60 turns

Since D = 0.5, we found that

Thus, 

N3 = 550 turns

Now, we will choose an inductor for 40% of the current ripple. We know that

Let us assume the switching frequency to be 20 kHz.

Let us start designing the output capacitor Cout for 5% of the voltage ripple.

Let us consider the magnetizing inductor (Lm) to be 1 mH.

Simulink Model

In this model, we use the following parameters, which we calculated.

1. Step

2. Forward Converter Subsystem

3. Linear Transformer

4. Feedback Control

Result

1. Current of the Transformer

After zooming in

Because of the switching action of MOSFET, the scope displays the input current like I_w1 current. The current amplitude is max 10V, and the minimum voltage is near zero. So, the average value is coming to approximately 4.7 A.

2. Switching State

After zooming in

3. Output

After zooming in

• The output voltage is getting 3V, the same as we required with some ripples, and ripples are also the same as we calculated, shown in the following graph.
  
  
• The current is 100 A because the isolated and multiphase systems are getting the output perfect as the requirements.

The main aim is to get the efficiency as high as possible, and as you see in our requirements, we are getting approximately the same. So, we can say that our efficiency is above 90%.

As efficiency is calculated from output power/input power, as we calculated for this converter from all the above data, we get the input power as 300 W, and the output power is also 300 W.

So, the efficiency is 100% without considering the ripple in voltage and current. If we believe the ripple also, we can get an efficiency of more than 90%.

Conclusion:

Hence, we designed the DC/DC Converter using the given data and achieved an output of more than 90�ficiency.