Buck Boost Converter with simulation model.pdf

Power electronics topic , Chopper

1. EXPERIMENT NO. 3 : SIMULATION OF BUCK / BOOST
CONVERTER USING MATLAB / SIMULINK

Objective: Design a Buck / Boost Converter with appropriate value of parameters and
simulate it.
Parameters of the Buck / Boost Converter:
Input voltage: 24V
Output Voltage: 48V
Output Power: 100W
Switching Frequency: 100kHz
Ripple in Inductor Current: 25%
Ripple in Output Voltage: 0.1%
Theory: Buck/Boost Converter is a DC to DC converter (Step up/down Chopper), By
adjusting Duty Ratio we can use either as Buck Converter (Vo < Vin) or Boost Converter (Vo
> Vin)
Duty Ratio
D =





=







Circuit Diagram and Theoratical Waveforms:

2. Design procedure and final design parameters obtained:
For getting desired response (VO = 48V) first we will design L & C by using
given parameters. By using L & C we will design a Buck/Boost Converter and
simulate it.
1. Duty Ratio:
D =






So, D=0.666

3. 2. Avg Current through Inductor (Theoretical):
IL = IS + IO =
+

IL = 6.25 Amp.
3. Ripple in Inductor Current:
ΔIL (Theoretical) = 1.5625 Amp.
ΔIL =




So, L = 102.5µH
where f is switching frequency
4. Ripple in Output Voltage:
ΔVo (Theoretical) = 0.048V
ΔVo =




So, C = 288.6µF

5. Load Resistance:
RL (Fixed) =

= 23.04Ω

4. 6. Simulation configuration parameters:
Here we are taking 100 Samples for each Time period So, Sampling frequency is
100 times of switching frequency(100kHz).
So, Sampling Time Period = 100nSec.


7. Simulation Model of Buck Converter:

5. Results:
1. Source Voltage Waveform:
Vin = 24V


2. Switching signal for turn ON/OFF to MOSFET:


3. Voltage Across the Diode:
When Diode is OFF
VD = 72 V
When Diode is ON
VD = -0.8V

6. 4. Voltage across the Switch/MOSFET:
When MOSFET/switch is ON
VSW = 0.8V
When MOSFET/switch is OFF
VSW = 72V


5. Current through Inductor:
Avg Current through Inductor (Practical)
IS = IL = 6.25Amp.
Ripple in Inductor Current (Practical)
ΔIL = 1.5Amp.

7. 6. Output voltage:
Output Avg. Voltage (Practical)
Vo= 46.37V
Ripple in Output Voltage (Practical)
ΔVo = 0.041V