Design and simulation of up/down converters using Simulink

1- Design a buck-boost converter with a source varying from 10 to 14 V. The output voltage is regulated at – 12 V. The load power is 15 W. The output voltage ripple must be less than 1 % for any operating condition.
a) Determine the range of the duty ratio of the switch.
b) Design the inductor and capacitor values used in your design.
c) Confirm your solutions using a simulation software for every operating condition (you must show the input voltage, the duty ratio, the output voltage “including the ripple” and the inductor current “including the ripple”).

2- The Sepic DC/DC converter shown below has 𝑉𝑠=3.3 𝑣,𝐷=0.7,𝐿1=4 𝜇𝐻,𝑎𝑛𝑑 𝐿2=10 𝜇𝐻,𝐶1=𝐶2=50𝜇𝐹. The load resistor is 5 Ω, and 𝑓𝑠=300 𝑘𝐻𝑧.
a) Determine the maximum and the minimum values of the inductor currents in 𝐿1 and 𝐿2.
b) Determine the variation in the capacitor voltages in both 𝐶1 and 𝐶2.
c) Confirm your results using a simulation software package.

1- Design a buck-boost converter with a source varying from 10 to 14 V. The output voltage is regulated at – 12 V. The load power is 15 W. The output voltage ripple must be less than 1 % for any operating condition.
a) Determine the range of the duty ratio of the switch.
b) Design the inductor and capacitor values used in your design.
c) Confirm your solutions using simulation software for every operating condition (you must show the input voltage, the duty ratio, the output voltage “including the ripple” and the inductor current “including the ripple”).

Solution:

 To Design buck-boost converter

Given Data,

Vin range: 10V to 14V

Power: 15W

Vout: -12V

Output Voltage Rippel: 1%

Schematic Diagram:

On the mode of operation:

Off mode of operation:

Calculation:

as per the calculation,

Duty Cycle range: 0.54 to 0.46 

R(Load)= 9.6 Ohm

Lmin (D: 0.54)= 3.38uH

Lmin (D: 0.46)= 4.66uH

Cout (D: 0.54)= 18.75uf

Cout (D: 0.46)=15.97uf

Matlab Circuit Diagram:

Output Waveform of the input voltage, the duty ratio, the output voltage “including the ripple” and the inductor current “including the ripple”

For,

Vin= 10V

Duty Cycle= 0.54

Lmin= 3.38uH

Cout= 18.75uf

Circuit Diagram for,

Vin= 14V

Duty Cycle= 0.46

Lmin = 4.66uH

Cout = 15.97uf

Output Waveform of the input voltage, the duty ratio, the output voltage “including the ripple” and the inductor current “including the ripple”

2- The Sepic DC/DC converter shown below has 𝑉𝑠=3.3 𝑣,𝐷=0.7,𝐿1=4 𝜇𝐻,𝑎𝑛𝑑 𝐿2=10 𝜇𝐻,𝐶1=𝐶2=50𝜇𝐹. The load resistor is 5 Ω and 𝑓𝑠=300 𝑘𝐻𝑧.
a) Determine the maximum and the minimum values of the inductor currents in 𝐿1 and 𝐿2.
b) Determine the variation in the capacitor voltages in both 𝐶1 and 𝐶2.
c) Confirm your results using a simulation software package.

Simulation:

Matlab Circuit Diagram:

Output Waveform of

Voltage Across C1 & C2

Current Through L1 & L2

Comments:

a) Determine the maximum and the minimum values of the inductor currents in 𝐿1 and 𝐿2.

1. The maximum value of the inductor current in 𝐿1: 3.5A

2. The minimum value of the inductor current in 𝐿1: 2.0A

3. The maximum value of the inductor current in 𝐿2: -0.9A

4. The minimum value of the inductor current in 𝐿2: -1.5A

b) Determine the variation in the capacitor voltages in both 𝐶1 and 𝐶2.

1. The maximum value of the capacitor voltages in 𝐶1: 3.32V

2. The minimum value of the capacitor voltages in 𝐶1: 3.27V

3. The maximum value of the capacitor voltages in 𝐶2: 5.98V

4. The minimum value of the capacitor voltages in 𝐶2: 5.93V

Hence, All the Data is verified from the simulation.

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