DNS001: LED Driver with MagI³C Power Module

sleuz — Mon, 22 Feb 2021 10:52:32 GMT

Current Revision posted to Documents by sleuz on 2/22/2021 10:52:32 AM

REFERENCE DESIGN NOTE

LED Driver with MagI³C Power Module

MagI³C Power Modules

VDRM - LED Driver Application

7 -24 V INPUT / 0 - 1.5A LED CURRENT

DNS001: BY ROLAND KRATZ

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

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

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 Iout = 10 mA - 1.5 A

4. Bill of Material

Index	Description	Size	Value	Manufacturer Order Code	Farnell Order Code	Supplier
IC1	MagI³C power module	BQFN-41	WPMDU1251501N	171 021 501	2505851	Würth Elektronik eiSos
IC2	Linear regulator	SOT-223	LM2936(HV)	LM2936MP-3.3 (40V)	3122053	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 5V at DIM pin/pad (5V = 1.5A)	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	2495187	Würth Elektronik eiSos
C7,C9		COG, NP0 0603 10%	22p/50V	885 012 006 053	2495135	Würth Elektronik eiSos
C8		X7R 0603 10%	22n/50V	885 012 206 091	2495183	Würth Elektronik eiSos
C6		X5R 0805 20%	10μ/10V	885 012 107 010	2533951	Würth Elektronik eiSos

Table 1: Bill of Material

5. Schematic and Layout

Figure 3: Schematic

Figure 4: Layout

6. Suitable Würth Elektronik eiSos High power LEDs

Figure 5: Recommended High Power White LEDs

Figure 6: Recommended High Power Colored LEDs

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 www.we-online.com. Customers shall strictly observe any product-specific notes, cautions and warnings. WE reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services.

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DIRECT LINK

https://www.we-online.com/web/en/index.php/download/media/07_electronic_components/download_center_1/application_notes_berichte/led_driver_with_magi3c_power_module/DNS001_LED_Driver_with_MagIC_Power_Module.pdf

CONTACT INFORMATION

Würth Elektronik eiSos GmbH & Co. KG

Max-Eyth-Str. 1, 74638 Waldenburg, Germany

Tel.: +49 (0) 7942 / 945 – 0

Email: appnotes@we-online.de

Web: http://www.we-online.com