Led Lighting Spd Design Installation Guide Page 19 LED Lighting SPD Design & Installation Guide

2015 Littelfuse LED Lighting SPD Module Design and Installation Guide www.littelfuse.com LED Lighting Surge Protection Modules Design and Installation Guide MOV2 MOV1 SPD AC Input I1 I2 I3 LED DRIVER G N L F1 R1 Figure 18. Residual voltage and current can damage an LED driver. Residual Voltage Determined by MOV1; therefore, a varistor with fast response time and low clamping voltage varistor is preferred. Residual Current The 820 s surge current waveform is calibrated to reach peak value (for example, 10kA) at the surge generator, before it is applied to the luminaire. When the surge current is discharged from the surge generator, it affects the SPD and power supply unit (PSU) at three major points. - I1: The current flow through the SPD (This is major portion of the surge current.) - I2: The current flow through the MOV in the PSU - I3: The current flow through the primary circuit in the PSU For MOV2, choose an MOV with a higher clamping voltage than the one used for MOV1 to maximize I1 and minimize I2 so that fuse F1 is not damaged by residual current. Fuse F1 should be also selected carefully, with a higher melting i 2 t rating to withstand residual surge current I2+I3. Below fuses are recommended for F1 as they are tested to withstand 3kA surge current. In poor coordination between MOV1 and MOV2, I2+I3 may go as high as 30%. These fuses can withstand 3kA residual surge current to help the luminaire survive the 10kA surge event. Power supply unit thus has higher compatibility with different SPDs and MOV1. Part Number Package Rating 8071630 9.2x6.4x12.4mm 6.3A 300V 219005 5x20mm 5A 250V 209007 4.5x14.5mm 7A 350V 477010 5x20mm 10A 500V R1, the equivalent resistance of the primary circuitry, including the NTC, EMI filter, rectifier, PFC, transformer, transistor, etc., could be adjusted higher if necessary in order to minimize I3 and component damage in the primary circuitry. TVS diode as ultimate protector in LED driver For components sensitive to and easily damaged by surge voltage or current, place TVS diodes in parallel with them to absorb "let-through" energy from the SPD module. Power Supply Unit Design Considerations (continued) 19

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