Installation Guide

LED Lighting Surge Protection Modules

Design and Installation Guide

MOV2

MOV1

SPD

AC Input

LED DRIVER

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 8×20μs 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

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)