Download Buck-Boost converter circuit drawing

SEE 4433
POWER ELECTRONIC AND DRIVES
GROUP 3
ASSIGNMENT 1
GROUP MEMBER:
NAME
: AMIR SHAHRIZAL BIN MOHD ZAHLAN
MATRIX NO : SX091666EEJ03
NAME
: AMMIRUL NIZAM BIN OTHMAN
MATRIX NO : SX091675EEJ03
NAME
: AZIAN BINTI YAHAYA
MATRIX NO : SX080513EEJ03
LECTURER:
PM DR AWANG BIN JUSOH
CONTENTS
PAGES
1. Quesstion
2. Problem Statement
3. Design Methodology
“Calculation of all parameters
4. Simulation
5. Conclusion
6. Reference
7. Appendix
2
1.0
Question
Problem (c)
Assuming that you working in Cellular Phone Company and your following task is to design a simple
mobile converter to charge the phone's battery. The converter has the technical specification as follows:
 Input voltage = 9 V
 Output voltage = -12 V
 Power rating = 5 W
 Peak-to-peak output ripple voltage < 2% (or 240mVpp)
 Switching frequency = 300 kHz
 Converter operating in CCM down to 5% load
 Assume all components are ideal
Establish the design parameter for this converter topology. Using MATLAB/Simulink/PSpice
simulation package, conduct the computer simulation to verify and confirm the design that have been
done. Submit a report with the following elements:
 Cover page : Title, Group No and members etc
 Introduction : Statement of problem
 Design methodology : All calculation of parameters
 MATLAB/Simulink/PSpice simulation: Procedures, circuits, results and discussion. In the
discussion, compare the theoretical design values and the obtained simulation results.
 Conclusion: Summarize of work and result in few sentences.
 References
 Appendix: Datasheets of selected devices used in the design.
3
2.0
Problem Statement
To design a simple mobile converter to charge the phone's battery with the specification Input
Voltage = 9 V and Output Voltage = -12 V with the output voltage always negative and the mobile
converter are operating in Continuous Current Mode (CCM) down to 5% load. The suitable
converter circuit to produce this output is Buck Boost Converter.
There are many types of dc-dc converter which is buck (step down) converter, boost (step up)
converter and buck-boost (step up-step down) converter. A Buck Boost Converter is a type of switch
mode converter that combine the principles of the Buck Converter and Boost Converter in a single
circuit. With the combination of these two regulator designs, it is possible to have a regulator circuit
that can cope with a wide range of input voltages both higher and lower than that needed by the
circuit
Figure a: buck-boost equivalent circuit
4
Figure b: buck-boost operating state
The output voltage is of the opposite polarity as the input. This is a switched-mode power
supply with a similar circuit topology to the boost converter and the buck converter. The output
voltage is adjustable based on the duty cycle of the switching transistor. One possible drawback of
this converter is that the switch does not have a terminal at ground; this complicates the driving
circuit. Neither drawback is of any consequence if the power supply is isolated from the load circuit
(if, for example, the supply is a battery) as the supply and diode polarity can simply be reversed.
The switch can be on either the ground side or the supply side.
5
3.0
Design Methodology
3.1 Specification given:







Input voltage = 9 V
Output voltage = -12 V
Power rating = 5 W
Peak-to-peak output ripple voltage < 2% (or 240mVpp)
Switching frequency = 300 kHz
Converter operating in CCM down to 5% load
Assume all components are ideal
3.2 Design Calculation
3.2.1 Duty Cycle
Vo
= Vd (
𝐷
)
T
(1−𝐷)
=
=
D
=
=
𝑉𝑜
(𝑉𝑜−𝑉𝑑)
−12𝑉
(−12𝑉−9𝑉)
DT
1
𝑓
1
3000𝐾ℎ𝑧
= 3.33 µs
= (0.571) (3.33µs) = 1.90 µs
= 0.571
3.2.2 Voltage
Switch Close
Switch Open
VL = Vd = 9V
VL = Vo = -12V
3.2.3 Load Current
P = IV
Io =
𝑃𝑜
𝑉𝑜
ideal components Ps = Po
=
5
12
= 0.42A
6
3.2.4 Converter Operating in Continuous Current Mode (CCM) down to 5% load
Find RNEW with output current drop to 5%
Io 5%
RNEW =
5
= 100 𝑥 0.42𝐴 = 0.021A
𝑉𝑜
Io 5%
= 571.4Ω
3.2.5 Minimum Inductance Value
Lmin
=
=
(1−D)2 xR
2𝑓
(1−0.571)2 x(571.4)
2(300𝐾ℎ𝑧)
= 175.3 µH
3.2.6 Output Voltage Ripple
∆Vo
=
𝑉𝑜 (𝐷)
𝑅𝐶𝑓
= ∆Vo p-p / 2
=
0.24
2
= 0.12V
3.2.7 Capacitance, C
C
=
=
Vo (𝐷)
∆Vo𝑅𝑓
12 (0.571)
(0.12)(571.4)(300𝐾ℎ𝑧)
= 0.33 𝑥 10−6 𝑓
= 0.33 µf
3.2.8 Ripple Factor
r
∆Vo
0.12
= Vo =
= 0.001 = 1%
12
7
3.2.9 ∆IL, Imax & Imin
(𝑉𝑑)(𝐷𝑇)
∆IL
=
Imax
= Io 5% +
Imin
= Io 5% +
L
=
∆𝐼𝐿
2
∆𝐼𝐿
2
9 𝑥 1.90 µ𝑠
175.3 µH
= 0.021 +
= 0.021 -
= 97.5mA
97.5𝑚𝐴
2
97.5𝑚𝐴
2
8
= 69.8mA
= 27.8mA
4.0
Procedure
a. Begin by first opening up MultiSim.
b. To create file/Open a schematic file
c. As a default a blank file named “Curcuit 1” is opened up on the workspace. To save a
schematic under a different name simply click on File/Save As on the toolbar and enter the
name of your choice. To open an existing file click on File/Open on the toolbar and select
the file to open.
1.
Placing components:
On the toolbar select Place/Component, the following window will appear:
Figure 4.1 : Selecting a component
From this list, find all components needed to suit in buck boost converter circuit such as VDC,
transistor( Mosfet) , diode, inductor, resistor, capacitor, clock voltage and ground components.
Make the circuit for buck converter using the following parts:
9
2. Editing the component
a. Once placed in the Mutisim window.
b. Arrange the components and wiring each other by clicking at the components terminal pin as
per buck boost converter circuit.
c. Set the parameter of the component by left double click on the component. Set parameter for
each of the components based on the specification given and the calculation done in the
previous section.
d. The schematic of the circuit as per below:
Q2
IRF232
D1
V2
V1
9V
300kHz
15 V
L1
175.3µH
C2
0.33µF
GND
Figure 4.2.1 : Buck-Boost converter circuit drawing
10
R1
571.4Ω
5.0
Analysis & Simulation Results
a. Simulation plots for output Voltage & Current converter operating in CCM mode down to
5% load
Specification
Simulation Result Error (%) Result
Output Voltage -12 V
-13.0 V
8.3
PASS
Output Current
0.021 A 0. 0228 A
8.6
PASS
Output Power
0.25W
16
PASS
0.29W
11
b. Peak-to-Peak Output Ripple Voltage
CH1: 100mV/Div: Output ripple Voltage
Result
Specification
Peak to peak output ripple voltage
240 mV
12
Simulation Result
Result
Less than 200 mV
PASS
Analysis
Perform analysis on the circuit to understand the operation each of the components used
1. Voltage and current across diode D1.
XSC1
Ext T rig
+
_
B
A
+
XCP1
Q2
IRF232
D1
V2
V1
9V
300kHz
15 V
L1
175.3µH
C2
0.33µF
R1
571.4Ω
GND
CH1: 10V/Div: VR of D1
CH2: 200mA/Div: Id of D1
13
_
+
_
2. Voltage and current across inductor L1
XSC1
Ext T rig
+
_
B
A
+
Q2
IRF232
XCP1 D1
V2
V1
9V
300kHz
15 V
L1
175.3µH
C2
0.33µF
GND
CH1:10V/Div: VL of L1
CH2:100mA/Div: IL of L1
14
R1
571.4Ω
_
+
_
3. Relationship between duty cycle (Vgs) and Vds of MOSFET Q1.
XSC1
Ext Trig
+
_
B
A
+
Q2
IRF232
_
+
_
D1
V2
V1
9V
300kHz
15 V
L1
175.3µH
C2
0.33µF
R1
571.4Ω
GND
XCP1
CH1: 10V/Div: Vds of Q1
CH2: 10V/Div: Duty cycle (Vgs) of Q1
15
Ton
Toff
ON
OFF
ON
OFF
t
VL
SWITCH STATE
5.2.1.2 Summary of buck boost operation Typical waveform
IL
t
ID
t
VD
t
IC
t
t
Output
∆Q
t
Iload
Vo
16
6.0 Discussion
7.0
8.0
Conclusion
References
1. Daniel W.Hart, Power Electronic, International EdittionMcGraw.Hill.
2.
SEE 4433: POWER ELECTRONICS AND DRIVES teaching module.
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