Planar Magnetics

benefits

Planar Technology

• The Same Physics - used in an innovative way

• Tremendous decrease in size/volume

• Incredible weight reduction

• Very High efficiency - 98% typical

• Excellent parameter repeatability and consistency

• Operating frequency range 50 kHZ – 2 MHZ

• Unique safety solution.

• Decrease inner temperature of Power Supply

Planar Transformer Structure

Ferrite

Conductors

Bobbin (Optional)

Insulators

Ferrite

Bobbin (Optional)

Conductors

Insulators

Planar Planar

Conventional

SMPS Block Diagram

Dimensions

Transformer dimensions

Cooling Power Frequency

Current Voltage

Cores cross section Ae Turns Ratio Current Density Copper Area

Flux Density Bp

Core Losses Insulation Losses Copper Losses

(Skin & Proximity)

Total

Losses

Temperature

Less Copper Loses

• Skin Effect

• Proximity Effect

• Leakage inductance

Function of the Construction

Smaller Skin Effect

High frequency currents in the conductor

generate a variable magnetic field that induces

voltages and, consequently, currents. The

latter are directed in such a way to reinforce the

current flowing close to the conductor surface

DPEN

JREAL JEQUIVALENT

DW

Current lines

DPEN = skin depth

Current effective area

Less Proximity Effect influence

• The current in a close path distributes itself

in such a way so as to minimize the energy

drawn from the source.

Opposite current direction Same current direction

Current effective area

Current effective area

Leakage inductance less then 0.3%

The same Leakage inductance on different production lots

Conventional transformer

Pri

Sec

Sec

Planar Transformer

Combined Pri

and Sec

Better Leakage inductance

Combined Pri and Sec

0.9%

Magneto-motive Force in the Core Window

m.m.f.

(dc)

0

NIdH.f.m.m

m

Magneto-motive Force in the Core Window

Secondary

winding Primary

winding

Isolation gap

m.m.f.

(dc)

0

LF Current

Distribution in Windings

Multiple winding transformer

with interleaved

primary/secondary windings

Pa Pb Sb Sa

F=NI

Energy

density

[J/m] W [J]

Reduced leakage

inductance

* Interleaving: wide single layer winding folded accordion-wise to fit

available core winding breadth

* Drawing shows windings folded into 6 winding sections

* Each layer is a single turn stamped copper foil

* Same as having 6 times the core winding breadth

* Field is zero at each section boundary

* Each layer can be thicker than skin depth,

reduces DCR, aids heat removal

Interleaving the Windings

Top

Advantages

Large magnetic cross-section

Short winding length

Little winding extending outside core

* Reduced EMI

Disadvantages

Smaller winding breadth

Bottom

Advantages

Greater winding breadth

Manufacturability – cost

Large magnetic cross-section

Disadvantages

Longer winding length

Winding extends beyond core

* EMI

Core Shapes Planar

Core material (Ferrite) Conventional

1.Small winding area

2.Small number of turns (less then 20)

3.Force designing under high Frequency

Planar

Turns ratio

Bigger Surface for heat sink attaching

or cooling area

The two option benefits

1. Smaller dimensions With the same Power

2. Same dimensions With twice the Power

Efficiency = 100%- ΔP/P% ΔP - total losses P- Output Power

Example @ Total Losses are the same

Transformer 1

•Efficiency= 96%

•Losses= 4%

•Output Power=500W

Transformer 2

•Efficiency= 98%

•Losses= 2%

•Output Power=1000W

Example @ Total Losses are half

Transformer 1

•Efficiency= 96%

•Losses= 4%

•Output Power=500W

Transformer 2

•Efficiency= 98%

•Losses= 2%

•Output Power=500W

Main points for design request

• Total output Power

• Input / output voltages

• Working frequency

• Dielectric strength

• Special safety requirements (optional)

• Cooling conditions

• Mechanical dimensions requirements

• Qty & price

Planar Conventional

Payton can offer both solutions