1.3 Operating principle of Buck ConverterChargephase9RidV.DM6伟书=Lt=0
1.3 Operating principle of Buck Converter Chargephase
DischargephaseDM节Key note:-LIn steady state, the inductorcurrent will resume at theendof each cycle!t=0
Dischargephase Key note: In steady state, the inductor current will resume at the end of each cycle!
1.4 PWM control for Buck ConverterV。(desired)UcontrolAmplifierSwitchComparatorcontrolV(actual)(a)BlockdiagramsignalRepetitivewavetormUat=SawtoothvoltageUcontrol(amplified error)T(b)ComparatorsignalsUcontrol>UstOnorSwitchcontrolsignalOffOffPulseWidthModulationVcontrol<Ust(PWM)(switchingfrequencyf,=E-ma
E- 1.4 PWM control for Buck Converter PoPowwerer ElecElecttronronicicss mail: xjhuang@bjtu.edu.cn Pulse Width Modulation (PWM) (b) Comparator signals (a) Block diagram
2.1 Buck converter0SimplifyingAssumptions么1. Transistors, diodes and33Lotherpassive+T+ VL :Voi木components are all idealR12Va2. The input is a pure dcvoltage Vd.(a)3. The output voltage isVpurely dc without anyripple（纹波）, that isV.(t) =V。4. Continuous conductionmode，CcM（连续导电(b)模式)
0 Simplifying Assumptions 1.Transistors, diodes and other passive components are all ideal. 2. The input is a pure dc voltage Vd . 3. The output voltage is purely dc without any ripple（纹波）, that is o o v (t) ≈V , 4. Continuous conduction mode, CCM（连续导电 模式） voi Vd O t on t t o ff S T 1 = f s (b) + Vd - C R + vo=Vo - + voi - (a) L + vL - i d iL i o Vo 2.1 Buck converter
VbeILfmaxiufChargephase10LfmaOR,IifmaxILfmin'V1-LfmaxiDIyminEVin-VVLDischargephaseVRuicsVo102ofTOn
Charge phase Dischargephase