Inductor design for an ultra low profile DC-DC converter in OLED

lighting applications

Jurica Kundrata, Adrijan Barić

Integrated Circuits and Electromagnetic Compatibility Laboratory

Faculty of Electrical Engineering and Computing

University of Zagreb

January 2013

IC & EMC Lab

Outline

• The FP7 project IMOLA

• Planar inductor: – Design approaches:

• Electrical

• Electromagnetic

• Thermal

– Analysis approaches:

• Mathematical models

• Numerical models (simulations)

• Measurements

• Current work

• Conclusion

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The FP7 project IMOLA – General info

• “Intelligent light management for OLED on foil applications”

• Project objective: – Large-area OLED-based lighting modules with built-in intelligent light

management

• Applications: automotive (dome and tail lightning), wall light

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• Funding: – Seventh Framework

Programme (FP7)

• Project duration: – 2011-10-01 to 2014-09-30

The FP7 project IMOLA – Partners

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The FP7 project IMOLA – Motivation

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• Responsibilities: – Embedded inductor design

(DC-DC converter)

– Electromagnetic compatibility (the whole module)

• Objectives: – Embedded inductor design of:

• Low series resistance (≤ 1 Ω)

• High inductivity (5-10 µH)

• High resonant frequency (≥ 50 MHz)

– Conformity of the lighting modules to EMC standards (CISPR 15)

Planar inductor – Design approaches

Electrical properties

Electromagnetic properties

Thermal properties

Heat spreading layer application

Inductor parameter space analysis

(w, s, R)

Two-layer inductor structures

Ferrite (FPC) layer application

Multi-coil inductor

structures

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Planar inductor – Analysis approaches

Electrical properties

Electromagnetic properties

Thermal properties

COMSOL Multiphysics RF & Heating Module

VNA measurements

Agilent ADS Momentum

Large Loop Antenna (LLA) setup

COMSOL Multiphysics RF Module

Mathematical models

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Planar inductor – Electrical properties (I)

• Electrical analysis: 1. Agilent ADS and COMSOL Multiphysics simulations (2-port S-params)

2. Electrical modelling

3. Verification (VNA measurements)

• Inductor parameter space analysis: 1. Rectangular grid in w-s-R space

2. Identifying parameter-response relationships

3. Mathematical modelling

4. Analysis in the context of the DC-DC converter requirements

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Planar inductor – Electrical properties (II)

Qmax

high Q

C3,min

C3,min low C3 low C3

fr,min limit

The w-s-R space center-point

gradients

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Planar inductor – Electrical properties (III)

Single layer structure Double layer structure

Alternative double layer structure

Ls = 0,233 µH

fr = 181 MHz

Ls = 0,594 µH

fr = 48 MHz

Ls = 0,543 µH

fr = 77 MHz

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Planar inductor – Electrical properties (IV)

• FPC layer application: – “Ferrite Polymer Compound” FPC

– A composite of ferrite particles (D ~ 10 µm) and polymeric filler

– Ferrite NiZn, MnZn, CoZrO, CoNiFe, …

FPC application effects FPC layer thickness effect

Brandon et al., 2003

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Planar inductor – Electromagnetic properties (I)

• Electromagnetic analysis: – COMSOL Multiphysics simulations

– Explicit EM field equations (MATLAB)

– Verification Large Loop Antenna System

(CISPR 16 Annex C, [300 kHz, 30 MHz])

• Multi-coil inductor structures:

+

CISPR 15 limit

noise margin

1L

4L

2L

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Planar inductor – Electromagnetic properties (II)

• Modelling EM field via explicit equations

1L 2L 4L

Magne

tic

fie

ld lin

es

Fa

r-fie

ld

rad

iatio

n

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Planar inductor – Electromagnetic properties(III)

• FPC layer application:

GND

FPC

CISPR 15 limit

noise margin

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Planar inductor – Thermal properties (I)

• Motivation: – Inductor is embedded in an OLED cell backplane

– The OLED cell is sensitive to thermal influences

– Increasing the operating temperature by 10 °C shortens the life span by 1,5 times

– Maximum temperature difference < 2 °C

• Thermal analysis: – Coupled elektromagneic i thermal simulations in COMSOL Multiphysics

– The heating effects of the inductor structure and the DC-DC converter IC

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Planar inductor – Thermal properties (II)

Aluminum heat spreading

layer application

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• DoE-based FPC layer analysis: – ferrite filler percentage, FPC layer thickness, track width and fill ratio

• Discrete DC-DC converter (1+ MHz) design

• EM radiation analysis of an OLED matrix

• OLED modules DALI Interface

• COMSOL Multiphysics Structural Mechanics

module

Current work

UPWM

IOLED

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Conclusion

• General information on the FP7 project IMOLA

• Description of the OLED lighting module

• Planar inductor design approaches: – Inductor design in w-s-R parameter space

– Different inductor structures (double-layer and multi-coil structures)

– Application of different layers (ferrite and heat-spreading layers)

• Planar inductor analysis approaches: – Mathematical models (EM-field and electrical parameters)

– Numerical models (simulations in ADS Momentum and COMSOL)

– Measurements (VNA and Large Loop Antenna)

• Current work

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