《电子电力技术》（英文版） Chapter 3 DC to DC Converters

Power electronics Chapter 3 DC to Dc converters (Choppers

PPoowweerr EElleeccttrroonniiccss Chapter 3 DC to DC Converters (Choppers)

PEREC Outline 3.1 Basic dc to dc converters 3.1. 1 Buck converter( Step-down converter) 3.1.2 Boost converter(Step-up converter) 3.1.3 Buck-Boost converter(Step-down/step-up converter) and Cuk converter 3.1. 4 Sepic converter and zeta converter 3.2 Composite dC/dc converters and connection of multiple dc/dc converters 3.2.1 A current-reversible chopper 3.2.2 Bridge chopper(H-bridge DC/DC converter) 3.2.3 Multi-phase multi-channel DC/DC converters 2

Power Electron cs i 2 Outline Outline 3.1 Basic DC to DC converters Basic DC to DC converters 3.1.1 Buck converter (Step 3.1.1 Buck converter (Step -down converter) down converter) 3.1.2 Boost converter (Step 3.1.2 Boost converter (Step -up converter) up converter) 3.1.3 Buc 3.1.3 Buc k -Boost converter (Step Boost converter (Step -down/step down/step -up converter) and up converter) and Cuk converter converter 3.1.4 Sepic converter and Zeta converter converter and Zeta converter 3.2 Composite DC/DC converters and connection of 3.2 Composite DC/DC converters and connection of multiple DC/DC converters multiple DC/DC converters 3.2.1 A current 3.2.1 A current -reversible chopper reversible chopper 3.2.2 Bridge chopper (H 3.2.2 Bridge chopper (H -bridge DC/ bridge DC/DC converter) C converter) 3.2.3 Mu 3.2.3 Multi -phase multi phase multi -channel DC/DC converters channel DC/DC converters

PEREC 3.1 Basic dc to dc converters Introduction -Buck converter SPDT switch changes dc component s R2 v() Switch output voltage waveform Duty cycle D 0≤D<1 complement D D=1-D switch osition 3

Power E l ect r o n cs i 3 3.1 Basic DC to DC converters Basic DC to DC converters Introduction Introduction—Buck converter Buck converter SPDT switch changes dc SPDT switch changes dc component component Switch output voltage Switch output voltage waveform Duty cycle D: Duty cycle D: 0 ≤ D ≤ 1 complement D’: D’ = 1 - D

PEREC Dc component of switch output voltage <>=D ared DTV s g DT Fourier analysis dc component average value T )÷(D)=DF

Power Electron cs i 4 Dc component of switch output voltage Dc component of switch output voltage Fourier analysis: Dc component = average value

aec Insertion of low-pass filter to remove switching e harmonics and pass only dc component 0 D 5

Power Electron cs i 5 Insertion of low Insertion of low -pass filter to remove switching pass filter to remove switching harmonics and pass only dc component harmonics and pass only dc component

PEREC Basic operation principle of buck converter Buck converter with ideal switch Rsv Q Realization using +v2()- power MOSFET and diode R

Power Electron cs i 6 Basic operation principle of buck converter Basic operation principle of buck converter Buck converter with Buck converter with ideal switch ideal switch Realization using Realization using power MOSFET power MOSFET and diode and diode

Thought process in analyzing basic DC/DC converters 4 Basic operation principle( qualitative analysis How does current flows during different switching states How is energy transferred during different switching states 4 Verification of small ripple approximation 4 Derivation of inductor voltage waveform during different SWItching states 4 Quantitative analysis according to inductor volt-second balance or capacitor charge balance 7

Power Electron cs i 7 Thought process in analyzing basic Thought process in analyzing basic DC/DC converters DC/DC converters Basic operation principle (qualitative analysis) Basic operation principle (qualitative analysis) – How does current flows durin How does current flows during different switching states g different switching states – How is energy transferred duri energy transferred during different switching states ng different switching states Verification of small ripple approximation Verification of small ripple approximation Derivation of inductor voltage waveform during different Derivation of inductor voltage waveform during different switching states switching states Quantitative analysis according to inductor volt Quantitative analysis according to inductor volt -second balance or capacitor charge balance balance or capacitor charge balance

F Actual output voltage waveform of buck converter 0)L Buck converter +V21 containing practical v R low-pass filter Actual output voltage actual waveform waveform v(t)=V+ripple vt=V+ ripple(t) Dc component I

Power Electron cs i 8 Actual output voltage waveform of buck converter Buck converter Buck converter containing practical containing practical low -pass filter pass filter Actual output voltage Actual output voltage waveform waveform v ( t) = V + vripple ( t )

PEREC The small ripple approximation v(t) actual waveform v()=+v) v(t=V+ ripple(t) y Dc component j In a well-designed converter, the output voltage ripple is small. Hence, the waveforms can be easily determined by ignoring the ripple I vrpe<<v

Power Electron cs i 9 The small ripple approximation The small ripple approximation v ( t) = V + vripple ( t ) In a well In a well -designed converter, the output voltage ripple is designed converter, the output voltage ripple is small. Hence, the waveform small. Hence, the waveforms can be easily determined by s can be easily determined by ignoring the ripple: ignoring the ripple:

Buck converter analysis inductor current waveform 1)L original converter I R vt) switch in position 1 switch in position 2 rATAN +V1D)- ○ R

Power E l ect r o n cs i 10 Buck converter analysis: Buck converter analysis: inductor current waveform inductor current waveform