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Buck ConverterBuck Converter
충북대학교 전기전자컴퓨터공학부 김영석
2 12 9 12012.9.1
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Power Electronics and DrivesDr Zainal Salam
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Dr. Zainal Salam
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SPEC: (1) 입력 전압: Vd=28V, (2) 출력 전압 Vo=15V 출력 전(2) 출력 전압 Vo=15V, 출력 전류: I=5A, 전압 리플 20mVpp, (3) Vref=5V, VM=4V, (4) f 100kHfs=100kHz
AV
IVR
R
oL 3
515
Ω===
VDVVDV
AI
do
R
2815 ,
5
⋅=⋅=D 5357.0=∴
kHzf 100=
14
HkHz
RfDL L 73
10025357.01
21
min ≈Ω⋅−
=−
= μ
D
HLLf
1
7010 min =⋅= μ
FVVDC
VLCf
DV
o
oo
6215)5357.01(181
2
=−
=−
=
−=Δ
μ
VV
FmkHzVLf
Co
)535701(15
62201007088 22 =⋅⋅⋅
=Δ
= μμ
AII
AkHz
VDLfVI
LC
oL
17.02/
110070
)5357.01(15)1(
=Δ
=
=⋅−
=−=Δμ
AAAI
AI rmsC
5)2/1(5
17.03
22
,
AAAI rmsL 5)32/1(5 22
, =+=
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PSPICE Simulations for Buck Converter Design
AIAIImVVVV
LRL
oo
03.1,86.420 ,6.14
≈Δ≈=≈Δ≈
AIAII LRL 03.1 ,86.4 Δ
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Control techniques입력 전압의 변동 등으로 출력 전압 변동 => Feedback 회로로 제어 필요
Control Techniques
Pulse Frequency Modulation
F V i• Frequency Varies
• Duty Cycle 50%
Pulse Width Modulation(PWM)Pulse Width Modulation(PWM)
• Frequency is Constant
• Duty Cycle Varies with the Load
Mode
Voltage Mode
C t M dCurrent Mode
Feedback System: Frequency Compensation 필요
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PWM Buck Converter
Voltage Modeg
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PWM Buck ConverterPSPICE
Frequency Compensation?
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Voltage Mode PWM
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Current Mode PWM
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Synchronous Buck Converter
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LTC3405 Block Diagram
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LTC3405 SPEC
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Chip Photo
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