Buck ConverterBuck Converter

충북대학교 전기전자컴퓨터공학부 김영석

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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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