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 ____________________________________________________ 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 Page 1 of 7 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 Page 2 of 7 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 Page 3 of 7 REFERENCE DESIGN NOTE LED Driver with MagI3C Power Module MagI3C Power Modules VDRM - LED Driver Application 𝑅3 = 75𝑚𝑉 𝐼𝐿𝐸𝐷𝑀𝐴𝑋 5. Schematic and Layout _________________________________________ Figure 4: Layout Figure 3: Schematic DNS001, 2015-04-27, RKr Page 4 of 7 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 Page 5 of 7 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 Page 6 of 7 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. 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Customers acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of WE products in such safety-critical applications, notwithstanding any applicationsrelated information or support that may be provided by WE. CUSTOMERS SHALL INDEMNIFY WE AGAINST ANY DAMAGES ARISING OUT OF THE USE OF WE PRODUCTS IN SUCH SAFETY-CRITICAL APPLICATIONS. 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 Toolbox: http://www.we-online.com/toolbox Web: http://www.we-online.com Max-Eyth-Str. 1, 74638 Waldenburg, Germany Email: [email protected] Product Catalog: http://katalog.we-online.de/en/ DNS001, 2015-04-27, RKr Page 7 of 7