DCDC基础知识
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Buck-Boost Converter
Step down-up Voltage Regulator
Buck-Boost
State 1: S is on, the inductor current rises linearly: V D di ∆I pk = in L L = Vin Lf S dt
Useful Power Level: 1 to 50 W Switch Voltage Stress: Vout Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
State 2: S is off, the inductor current decreases linearly: di (V − Vin )(1 − D) − L L = Vin − Vo ∆I pk = o dt Lf S
Boost
Boost
CCM
DCM
Boost
The voltage ripple of output capacitor: iD>Io, Cout is charged
Rectifier: VRRM > Vo IF(AV) > Io
Power Switch: VDDS > Vo IDmax > Io/(1-D)+∆I/2 fS = 1/TS D = Ton/TS Vo =Vin/(1-D)
3 The Buck-Boost Converter
Buck-Boost
∆U o = ESR • ∆I Lpk =
DVin • ESR Lf fS
Boost
Critical condition between DCM and CCM
I in V in D 1 = I L max = 2 2L f fS
Power Balance
DCM
I in < V D 1 I L max = in 2 2L f f S
State 2: S is off, the inductor current decreases linearly: di V (1 − D) − L L = Vo ∆I pk = o dt Lf S
Volts Second Balance: Vo = VinD/(1-D), D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = Io (1-D)/D
1) Integral during the period
1 Ton ∆U o = ∫ io dt C 0 DI o = Cout f S
2) The charge during the period
∆Q = DI oTs ∆U o = DI o ∆Q = Cout Cout f S
Take ESR into Account:
Power Balance
DCM
(Vin − Vo ) D 1 I o < I L max = 2 2L f f S
Toff = D' TS = Vo D = Vin D + D ' (Vin − Vo ) D TS < (1 − D)TS Vo
Volts-Sec Balance
Ton + Toff V −V D2 1 Vin in o Io = I L max = TS Vo 2 2LfS
Power Switch: VDDS > Vinmax IDmax > Io+∆I/2 Rectifier: VRRM > Vinmax fS = 1/TS IF(AV) > Io(1-D)
D = Ton/TS Vo = DVin
2 The Boost Converter
Boost
Boost Converter
State 2: S is off, the inductor current decreases linearly: di nV (1 − D) − L L = nVo ∆I pk = o dt Lf S
Volts Second Balance: Vo = VinD/n(1-D), D = Ton/ T, n=Np/Ns Vin ⋅ Iin = Vo ⋅ Io, Iin = Io (1-D)/D
Rectifier: VRRM > Vinmax+Vo Power Switch:
VDDS > Vinmax+Vo IDmax > Io/(1-D)+∆I/2
IF(AV) > Io
fS = 1/TS D = Ton/TS Vo =Vin/(1-D)
Conclusion
3 The Fly Back Converter
Vin D TS < (1 − D )TS Vo − Vin
Volts-Sec Balance
Toff = D ' TS = Vo D + D ' = Vin D'
Toff D2 Vin2 1 Io = ILmax = 2 TS 2LfS Vo −Vin
Boost
Disadvantages: a limited power range a relatively
(Vin-VDSS)Ton = VflToff
Vfl = nVo n = Np/Ns VDSS = 0
Fly Back
Volt-Second Balance
The net change in energy in the inductor must be Zero (average voltage: 0) over one cycle. The integral of voltage over time volt-seconds across the inductor during turn on must equal that across the secondary during turn off
State 2: S is off, the inductor current decreases linearly: di V (1 − D) − L L = Vo ∆I pk = o dt Lf S
Buck
Buck
CCM
DCM
Buck
The voltage ripple of output capacitor: iL>Io, Cout is charged
Step Up Voltage Regulator
Boost
State 1: S is on, the inductor current rises linearly: V D di ∆I pk = in L L = Vin Lf S dt Volts Second Balance: Vo = Vin/(1-D), D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = Io ( 1-D)
Buck-Boost
Buck-Boost
CCM
DCM
Buck-Boost
Critical condition between DCM and CCM
I in V in D 1 = I L max = 2 2L f fS
Power Balance
DCM
I in < V D 1 I L max = in 2 2L f f S
1) Integral during the period
1 Ton 1 ∆U o = ∫Ton iC dt + C 2 C (1 − D)Vo = 2 8 L f C out f S
2) The charge during the period
1 ∆I Lpk Ts ∆Q = 2 2 2 (1 − D )Vo ∆Q ∆U o = = C out 8 L f C out f S 2
Vin D TS < (1 − D)TS Vo
Volts-Sec Balance
Toff = D' TS = Vo D = Vin D'
Toff D2 Vin2 1 Io = ILmax = 2 TS 2LfS Vo
Buck-Boost
DCM
1 2 Pin = LI L pk f S 2
1 D= Vin
Disadvantages: a limited power range a relatively
high output ripple due to all of the off-time energy coming from the output capacitor
Advantages: simplicity, low cost and the ability to
high output ripple due to all of the off-time energy coming from the output capacitor
Advantages: simplicity, low cost and the ability to
achieve up conversion without a transformer
Fly Back
Vin
T
D
Io
Vo
Cin
Ip
Q
Is
Ic
Co
Fly Back Converter
Single End Converter
It is derivate from the Buck-Boost
Fly Back
State 1: S is on, the inductor current ramps up linearly: V D di ∆I pk = in L L = Vin Lf S dt
Buck
Disadvantages: a limited power range Advantages: simplicity and low cost Useful Power Level: 1~50 W Switch Voltage Stress: Vin Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
Fly Back
Volt-Second Balance
The net change in energy in the transformer must be zero over one cycle. The volt-seconds across the primary during turn on must equal that across the secondary during turn off, reflected to the primary.
achieve negative conversion without a transformer
Useful Power Level: 1 to 50 W Switch Voltage Stress: Vinmax +Vout Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
∫
Ton +
Toff 2
Ton
iC dt
Take ESR into Account:
∆U o = ESR • ∆I Lpk =
(1 − D)Vo • ESR Lf fS
Buck
Critical condition between DCM and CCM
Io 1 (V in − V o ) D = I L max = 2 2L f fS
1 D2 = Vo
I Lpk =
2 Pin Lf S
D=Ton/TS D2=Toff/TS TS=Ton+Toff+Toff1
2 Pin Lf S
2 Pin Lf S
Dmax + D2 max ≤ 1
Байду номын сангаас
1 Lo ≤ 1 1 2 2 Pmax f S ( + ) Vin min Vo
Buck-Boost
Technical
Training
Adlsong
SMPS Topologies
The Buck Converter
Buck
Buck Converter
Step Down Voltage Regulator
Buck
State 1: S is on, the inductor current rises linearly: (V − V ) D di L L = Vin − Vo ∆I pk = in o Lf S dt Volts Second Balance: Vo = DVin, D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = IL = Io/D
Step down-up Voltage Regulator
Buck-Boost
State 1: S is on, the inductor current rises linearly: V D di ∆I pk = in L L = Vin Lf S dt
Useful Power Level: 1 to 50 W Switch Voltage Stress: Vout Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
State 2: S is off, the inductor current decreases linearly: di (V − Vin )(1 − D) − L L = Vin − Vo ∆I pk = o dt Lf S
Boost
Boost
CCM
DCM
Boost
The voltage ripple of output capacitor: iD>Io, Cout is charged
Rectifier: VRRM > Vo IF(AV) > Io
Power Switch: VDDS > Vo IDmax > Io/(1-D)+∆I/2 fS = 1/TS D = Ton/TS Vo =Vin/(1-D)
3 The Buck-Boost Converter
Buck-Boost
∆U o = ESR • ∆I Lpk =
DVin • ESR Lf fS
Boost
Critical condition between DCM and CCM
I in V in D 1 = I L max = 2 2L f fS
Power Balance
DCM
I in < V D 1 I L max = in 2 2L f f S
State 2: S is off, the inductor current decreases linearly: di V (1 − D) − L L = Vo ∆I pk = o dt Lf S
Volts Second Balance: Vo = VinD/(1-D), D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = Io (1-D)/D
1) Integral during the period
1 Ton ∆U o = ∫ io dt C 0 DI o = Cout f S
2) The charge during the period
∆Q = DI oTs ∆U o = DI o ∆Q = Cout Cout f S
Take ESR into Account:
Power Balance
DCM
(Vin − Vo ) D 1 I o < I L max = 2 2L f f S
Toff = D' TS = Vo D = Vin D + D ' (Vin − Vo ) D TS < (1 − D)TS Vo
Volts-Sec Balance
Ton + Toff V −V D2 1 Vin in o Io = I L max = TS Vo 2 2LfS
Power Switch: VDDS > Vinmax IDmax > Io+∆I/2 Rectifier: VRRM > Vinmax fS = 1/TS IF(AV) > Io(1-D)
D = Ton/TS Vo = DVin
2 The Boost Converter
Boost
Boost Converter
State 2: S is off, the inductor current decreases linearly: di nV (1 − D) − L L = nVo ∆I pk = o dt Lf S
Volts Second Balance: Vo = VinD/n(1-D), D = Ton/ T, n=Np/Ns Vin ⋅ Iin = Vo ⋅ Io, Iin = Io (1-D)/D
Rectifier: VRRM > Vinmax+Vo Power Switch:
VDDS > Vinmax+Vo IDmax > Io/(1-D)+∆I/2
IF(AV) > Io
fS = 1/TS D = Ton/TS Vo =Vin/(1-D)
Conclusion
3 The Fly Back Converter
Vin D TS < (1 − D )TS Vo − Vin
Volts-Sec Balance
Toff = D ' TS = Vo D + D ' = Vin D'
Toff D2 Vin2 1 Io = ILmax = 2 TS 2LfS Vo −Vin
Boost
Disadvantages: a limited power range a relatively
(Vin-VDSS)Ton = VflToff
Vfl = nVo n = Np/Ns VDSS = 0
Fly Back
Volt-Second Balance
The net change in energy in the inductor must be Zero (average voltage: 0) over one cycle. The integral of voltage over time volt-seconds across the inductor during turn on must equal that across the secondary during turn off
State 2: S is off, the inductor current decreases linearly: di V (1 − D) − L L = Vo ∆I pk = o dt Lf S
Buck
Buck
CCM
DCM
Buck
The voltage ripple of output capacitor: iL>Io, Cout is charged
Step Up Voltage Regulator
Boost
State 1: S is on, the inductor current rises linearly: V D di ∆I pk = in L L = Vin Lf S dt Volts Second Balance: Vo = Vin/(1-D), D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = Io ( 1-D)
Buck-Boost
Buck-Boost
CCM
DCM
Buck-Boost
Critical condition between DCM and CCM
I in V in D 1 = I L max = 2 2L f fS
Power Balance
DCM
I in < V D 1 I L max = in 2 2L f f S
1) Integral during the period
1 Ton 1 ∆U o = ∫Ton iC dt + C 2 C (1 − D)Vo = 2 8 L f C out f S
2) The charge during the period
1 ∆I Lpk Ts ∆Q = 2 2 2 (1 − D )Vo ∆Q ∆U o = = C out 8 L f C out f S 2
Vin D TS < (1 − D)TS Vo
Volts-Sec Balance
Toff = D' TS = Vo D = Vin D'
Toff D2 Vin2 1 Io = ILmax = 2 TS 2LfS Vo
Buck-Boost
DCM
1 2 Pin = LI L pk f S 2
1 D= Vin
Disadvantages: a limited power range a relatively
high output ripple due to all of the off-time energy coming from the output capacitor
Advantages: simplicity, low cost and the ability to
high output ripple due to all of the off-time energy coming from the output capacitor
Advantages: simplicity, low cost and the ability to
achieve up conversion without a transformer
Fly Back
Vin
T
D
Io
Vo
Cin
Ip
Q
Is
Ic
Co
Fly Back Converter
Single End Converter
It is derivate from the Buck-Boost
Fly Back
State 1: S is on, the inductor current ramps up linearly: V D di ∆I pk = in L L = Vin Lf S dt
Buck
Disadvantages: a limited power range Advantages: simplicity and low cost Useful Power Level: 1~50 W Switch Voltage Stress: Vin Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
Fly Back
Volt-Second Balance
The net change in energy in the transformer must be zero over one cycle. The volt-seconds across the primary during turn on must equal that across the secondary during turn off, reflected to the primary.
achieve negative conversion without a transformer
Useful Power Level: 1 to 50 W Switch Voltage Stress: Vinmax +Vout Switch Power Stress: Pin Transformer Utilization: N/A Duty Cycle: <1.0 Output Ripple Frequency: fS Relative Cost: Low
∫
Ton +
Toff 2
Ton
iC dt
Take ESR into Account:
∆U o = ESR • ∆I Lpk =
(1 − D)Vo • ESR Lf fS
Buck
Critical condition between DCM and CCM
Io 1 (V in − V o ) D = I L max = 2 2L f fS
1 D2 = Vo
I Lpk =
2 Pin Lf S
D=Ton/TS D2=Toff/TS TS=Ton+Toff+Toff1
2 Pin Lf S
2 Pin Lf S
Dmax + D2 max ≤ 1
Байду номын сангаас
1 Lo ≤ 1 1 2 2 Pmax f S ( + ) Vin min Vo
Buck-Boost
Technical
Training
Adlsong
SMPS Topologies
The Buck Converter
Buck
Buck Converter
Step Down Voltage Regulator
Buck
State 1: S is on, the inductor current rises linearly: (V − V ) D di L L = Vin − Vo ∆I pk = in o Lf S dt Volts Second Balance: Vo = DVin, D = Ton/ T Vin ⋅ Iin = Vo ⋅ Io, Iin = IL = Io/D