IE

Switch mode power supply

230 Vac 50 Hz

15 Vdc

Low frequency (50 Hz)

rectifying High frequency AC generation

Isolation, Adopting voltage

Stabilize DC-voltage

High frequency rectifying

IE

Switch mode power supply Transformer definition

V1 N1 N2 V2

=

=

=

2

2

1

2

1

1

2

2

1

2

1

2

1

NN

ZZ

NN

II

NN

VV

IE

Switch mode power supply Transformer

φm φ1

φ2

IE

Switch mode power supply Transformer equivalent circuit

reduced to one side

φ1 φ2

φM

IE

Forward converter

vC Rload

VDc Cdc

vS

C D2

D1 D3

Z

VD1

L

S

N1 N2

IE

Forward converter at turn on

vC Rload

VDc Cdc

vS

C D2

D1 D3

Z

VD1

L

N1 N2

Turn on

IE

Forward converter at turn off

vC Rload

VDc Cdc

vS

C D2

D1 D3

Z

VD1

L

N1 N2

Turn off

IE

Fly-back converter vD

vC

VDc Cdc

vS

C

IE

Fly-back converter at turn on

vD

vC

VDc Cdc

vS

C

Turn on

IE

Fly-back converter at turn off

vD

vC

VDc Cdc

vS

C

Turn off

IE

Fly-back converter Transformer snubber

vC C

IE

Fly-back converter Switch snubber

vC C

IE

Fly-back converter Diode snubber

vC C

IE

Fly-back converter RCD snubber at turn off

Leakage inductance requires a freewheeling path

IE

Switch mode power supply Transformer

φm φ1

φ2

IE

Fly-back converter RCD snubber at turn on

Transformer leakage inductance requires a freewheeling path. Design of capacitor C i based on voltage over C

C

stUCtIUCQechtoTime

FC

VUHL

AIExample

UILCWWequalEnergies

UCWCinenergyElectric

ILWenergyMagneticUvoltagecapacitorAllowed

em

e

m

µ

µ

µ

6610

151044arg

44151010

1510010

6

24

2

221

221

<⋅⋅

=⇒⋅=⋅⇒⋅=

=

⋅=

=∆==

∆

⋅=⇒=

∆⋅⋅=

⋅⋅=

∆

−

−

IE

Fly-back converter RC snubber over main switch

Needed due to fast switching and stray inductance

IE

Fly-back converter Diode snubber

vC C

vC C

IE

Fly-back converter Rectifier

IE

Fly-back converter Common mode filter

IE

Fly-back converter. Inrush current limitation

T-

IE

Fly-back converter Differential mode filter

T-