Electronic Transformer Compatible
Step-down Converter for 3W MR16 Lamp with
ILD4035
Application Note AN214
Revision: 1.0
Date: 2011- 09- 02
Power Management & Multimarket
Edition 2011-09-02
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2012 Infineon Technologies AG All
Rights Reserved.
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Application Note AN214
Electronic Transformer Compatible Step-down Converter for 3W MR16 Lamp with ILD4035
Application Note AN214
Revision History: 2011-09-02
Previous Revision: Previous_Revision_Number
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Subjects (major changes since last revision)
Application Note AN214, 1.0
3 / 10
2011-09-02
Application Note AN214
Electronic Transformer Compatible Step-down Converter for 3W MR16 Lamp with ILD4035
1
Introduction
1.1
Features
•
•
•
•
•
Driver number of LED, 3 in series
Output Power, 3 Watt
12 Volt AC operation
Stable LED current vs. input voltage
Termerature protection
1.2
Brief Description
The ILD4035 provides a low-cost solution for driving 1W LEDs with a LED current up to 400mA. The supply
voltage of this LED driver IC is up to 22V; hence this IC is suitable for MR16 application at 12VAC operation.
2
LED Driver PCB Design
The 3W MR16 control board has 2 input pins, it connect to 12 VAC input power supply. There are 2 LED terminal
pins, it allow use connect to 3 LED in series. The demo board is configured with 350mA LED current.
2.1
Calculation of Rsense resistance
The internal voltage reference for the R
sense
resistors is typically (V
s
-
Vsense
) = 0.114V
To set the LED current to near 0.35 A, the effective resistance between V
S
and V
sense
pin is calculated as:
R
sense
=0.114V/0.35A =0.33
Ω
This
Rsense
can be achieved by paralleling three physical resistor, R1=R2=R3=1.0
Ω
(Or one piece of 0.33
Ω
resistor).
2.2
Given the following data:
Calculation of the L1 inductance
Buck-switching frequency f = 200 kHz,
Duty-on-cycle of V
switch
of ILD4035, D = 90%,
Voltage drop of LEDs, V
fLEDS
= 3.3V x 3 pcs in series = 9.9V,
Voltage drop of schottky diode, V
fD
= 0.3V,
Voltage drop of Vswitch to ground when internal switch is on, V
drop
= 1.1V,
Average LED current, I
LED
= 0.35A,
Inductance of L1 can be calculated approximately as:
The next higher practical value for SMD inductance is 100 μH.
Application Note AN214, 1.0
4 / 10
2011-09-02
Application Note AN214
Electronic Transformer Compatible Step-down Converter for 3W MR16 Lamp with ILD4035
2.3
PCB schematic and layout
Figure 1
Schematic LED Driver Design
Figure 2
PCB Layout Top View of Driver Board.
Application Note AN214, 1.0
5 / 10
2011-09-02
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