Rev. B 02/13

2

LYT4211-4218/4311-4318

www.powerint.com

Figure 3d. Typical Buck-Boost Schematic.

Figure 3c. Typical Tapped Buck Schematic.

Figure 3b. Typical Buck Schematic.

Figure 3a. Typical Isolated Flyback Schematic.

Table 2.

Performance of Different Topologies in a Typical Non-Dimmable 10 W Low-Line Design.

CONTROL

Topology

Isolation

Efficiency

Cost

THD

Output Voltage

Isolated Flyback

Yes

88%

High

Best

Any

Buck

No

92%

Low

Good

Limited

Tapped Buck

No

89%

Middle

Best

Any

Buck-Boost

No

90%

Low

Best

High-Voltage

PI-6841-081512

D

S

BP

V

FB

R

CONTROL

AC

IN

LYTSwitch

PI-6842-081512

D

S

BP

CONTROL

AC

IN

V

FB

R

LYTSwitch

Typical Circuit Schematic

Key Features

Flyback

Benefits

•

Provides isolated output

•

Supports widest range of output voltages

•

Very good THD performance

Limitations

•

Flyback transformer

•

Overall efficiency reduced by parasitic capacitance

and inductance in the transformer

•

Larger PCB area to meet isolation requirements

•

Requires additional components (primary clamp and bias)

•

Higher RMS switch and winding currents increases losses

and lowers efficiency

Buck

Benefits

•

Highest efficiency

•

Lowest component count – small size

•

Simple low-cost power inductor

•

Low drain source voltage stress

•

Best EMI/lowest component count for filter

Limitations

•

Single input line voltage range

•

Output voltage <0.6

× V

•

Output voltage for low THD designs

•

Non-isolated

Tapped Buck

Benefits

•

Ideal for low output voltage designs (<20 V)

•

High efficiency

•

Low component count

•

Simple low-cost tapped inductor

Limitations

•

Designs best suited for single input line voltage

•

Requires additional components (primary clamp)

•

Non-isolated

Buck-Boost

Benefits

•

Ideal for non-isolated high output voltage designs

•

High efficiency

•

Low component count

•

Simple common low-cost power inductor can be used

•

Lowest THD

Limitations

•

Maximum V

•

Single input line voltage range

•

Non-isolated

PI-6859-081512

D

S

BP

V

FB

R

CONTROL

AC

IN

LYTSwitch