DNS001: LED Driver with MagI³C Power Module

REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
DNS001: BY ROLAND KRATZ
7 - 24V INPUT / 0 – 1.5A LED CURRENT
1. Introduction _________________________________________________
The DNS14 is a reference design for the WLMDU9456008T LED driver capable of driving up to 1.5 A output
current using a voltage regulated module and an external secondary regulation loop to establish current
regulation. The external loop regulates a DC output current which results in a constant photon flow. Compared
to other solutions with PWM, this solution is less harmful to the eyes due to the constant photon flow, allowing
the pupil opening to be the proper size for the light intensity emitted. Depending on the LED flux voltage up to
4 LEDs in series can be connected.
2. Features ____________________________________________________
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




Input voltage range from 7 V to 24 V
Output current up to 1.5 A
Adjustable current from 10 mA to 1.5 A
Dimming voltage 0 V (10 mA) to 5 V (1.5 A)
Current regulation
Output current ripple typ. < 10 mA
Output power up to 22.5 W
Series connected LEDs up to 15 V total flux voltage
Figure 1: Development Example
Figure 2: Simplified Schematic
DNS001, 2015-04-27, RKr
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
3. Description __________________________________________________
The power consumption of LEDs on the lighting market is constantly increasing. LEDs require currents of 700
mA, 1 A or higher. High output currents are supported commonly with voltage regulated modules. Constant
high current led drivers are uncommon on the market. This design note describes how to convert a voltage
regulated module to a current regulated module. Typical supplies for LEDs are modules operating as current
sources. They include dual protection against output short circuits. A current regulated circuit is - if designed
properly - short circuit protected by itself due to its nature of forcing a defined current into the load regardless
if the load is an LED or a low resistance like a short circuit. The second overcurrent protection circuit is
integrated in the module commonly through a cycle by cycle current limit.
A MagI3C VDRM module is used in this application. Natively it is voltage regulated. The current through a
specific number of LEDs will flow from LED+ pin through the LEDs to the LED- pin. The LED current flows
through a shunt resistor, R3, and the voltage across R3 is compared with a dimming voltage. A 5 V dimming
voltage at the DIM terminal results in a voltage of 75 mV at the regulation loop amplifier (IC3, pin4) with which
the shunt voltage (IC3, pin 3) is compared. IC3 is used for an outer and slower regulation circuit which drives
the feedback pin of the VDRM module. The compensation network consists of C8, C9 and R6, which may be
trimmed by the design engineer depending on the customer PCB layout if modified from the reference design
PCB layout.
An external dimming (adjusting) voltage is always required. This can be derived directly from VIN if stable or
from a resistor divider from the 3.3 V of the linear regulator (IC2).
The supply of the operational amplifier is derived from VIN with a linear regulator (IC2) with a capability of abs.
max. 40V or 60V input voltage. Its output voltage is set to 3.3V. The Input voltage of the design ranges from 7
V to 50 V (only with the 60 V version of the LM2936, which is not available in this small package) and the
output current ranges from 0 A to 2.5 A. Note that the output power shall not exceed 22.5 W. The compensation
may be adapted for various operating points.
This Reference Design is developed using the following specification:
Vin = 7 V - 24 V
Vout = 0 V - 15 V
DNS001, 2015-04-27, RKr
Iout = 10 mA - 1.5 A
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
4. Bill of Material _______________________________________________
Index
Description
Size
Value
Order Code
Supplier
IC1
MagI3C power module
BQFN-41
WPMDU1251501N
171 021 501
Würth Elektronik
eiSos
IC2
Linear regulator
SOT-223
LM2936(HV)
LM2936MP-3.3
(40V)
Texas
Instruments
IC3
Operational amplifier
SOT-23
OPA364
OPA364
Texas
Instruments
R5,R6,R8,R13
0603 1% TK100
125mW
1K00
R10,R11,R12
0603 1% TK100
125mW
2K00
R1
0603 5% TK100
125mW
10R0
R2
0603 5% TK100
125mW
0R02
R4,R9
Change R9 to your UVLO needs
0603 1% TK100
125mW
10K0
R7
Defines max current at 5 V at DIM
pin/pad (5 V = 1.5 A)
0603 1% TK100
125mW
64K9
R3
Shunt resistor
1210 0,5%
250mW
0R05
C2,C3
X5R or X7R
1210 10%
10µ/50V
C5,C10,C11
X7R 0603 10%
100n/50V
885 012 206 095
Würth Elektronik
eiSos
C7,C9
COG,NP0 0603
10%
22p/50V
885 012 006 053
Würth Elektronik
eiSos
C8
X7R 0603 10%
22n/50V
885 012 206 091
Würth Elektronik
eiSos
C6
X5R 0805 20%
10µ/10V
885 012 107 010
Würth Elektronik
eiSos
Table 1: Bill of Material
DNS001, 2015-04-27, RKr
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
3 =
75

5. Schematic and Layout _________________________________________
Figure 4: Layout
Figure 3: Schematic
DNS001, 2015-04-27, RKr
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
6. Suitable Würth Elektronik eiSos High power LEDs _________________
Figure 5: Recommended High Power White LEDs
DNS001, 2015-04-27, RKr
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
Figure 6: Recommended High Power Colored LEDs
DNS001, 2015-04-27, RKr
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REFERENCE DESIGN NOTE
LED Driver with MagI3C Power Module
MagI3C Power Modules
VDRM - LED Driver Application
IMPORTANT NOTICE
The Application Note is based on our knowledge and experience of typical requirements regarding these areas: It serves
as general guidance and should not be construed as a commitment for the suitability for customer applications by Würth
Elektronik eiSos GmbH & Co. KG. The information in the Application Note is subject to change without notice. This
document and parts thereof must not be reproduced or copied without written permission, and contents thereof must not
be imparted to a third party nor be used for any unauthorized purpose.
Würth Elektronik eiSos GmbH & Co. KG and its subsidiaries and affiliates (WE) are not liable for application assistance of
any kind. Customers may use WE’s assistance and product recommendations for their applications and design. The
responsibility for the applicability and use of WE Products in a particular customer design is always solely within the
authority of the customer. Due to this fact it is up to the customer to evaluate and investigate, where appropriate, and
decide whether the device with the specific product characteristics described in the product specification is valid and
suitable for the respective customer application or not.
The technical specifications are stated in the current data sheet of the products. Therefore the customers shall use the
data sheets and are cautioned to verify that data sheets are current. The current data sheets can be downloaded at
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USEFUL LINKS
CONTACT INFORMATION
Application Notes:
http://www.we-online.com/app-notes
Würth Elektronik eiSos GmbH & Co. KG
Component Selector:
http://www.we-online.com/component-selector
Tel.: +49 (0) 7942 / 945 – 0
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http://www.we-online.com/toolbox
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Email: [email protected]
Product Catalog:
http://katalog.we-online.de/en/
DNS001, 2015-04-27, RKr
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