A ApplicnA031tion note

ApplicAtion note An031

1 Commercial Refrigeration Lighting System 2009.09.22

ApplicAtion note

An031commercial Refrigeration

lighting System2009.09.22



1. overviewFuture Lighting Solutions has developed an LED-based commercial refrigeration lighting system leveraging LUXEON® Rebel LEDs, providing a complete optical and thermal solution to enable applications such as reach-in/walk-in refrigeration units, found in grocery stores and supermarkets.

Four light strips have been produced that can be mounted on the sides and the center of a refrigeration unit. The center strip consists of two side strips attached together back-to-back. The blue lines in Figure 1 show the light strip placement in a refrigeration unit.

All the solutions described in this application note, as well as any mechanical drawings of the design, are available at Future Lighting Solutions to enable the implementation of the system for prototyping or volume production.

Demo kits that include the light strips have been assembled to showcase the functionality of the design along with their thermal and power solutions. These kits are available to be presented to demonstrate the design. Figure 2 shows the kit with the light strips and their power solution assembled.

Figure 1. Refrigeration Unit with light strips placement indicated Figure 2. Commercial Refrigeration light strips kit

Conducting research in the market revealed certain parameters that the lighting industry requires. These parameters were used as a starting point in developing the LED-based commercial refrigeration lighting system:

Target Luminaire Light Output 1200-1500 lux (Average)

Target Volume to Illuminate60 x 60 x 30 inches

(1.524 x 1.524 x 0.762 m)

Target Luminaire Efficacy 50-70 lm/W

Target Luminaire Lifetime 3-5 years, 50k hours

Target Luminaire Color Temperature 4000K

Target Luminaire CRI 70, 80, 85

Input Voltage Range (DC, 110, 220, Universal, 277) Universal or dedicated

Power Factor Requirements > 0.9

Table 1. Commercial refrigeration target specifications



2. SSl Designer AnalysisThe SSL Designer software (www.futurelightingsolutions.com/ssldesigner) considers the target light specifications such as the efficacy, illuminance, system lifetime, along with the maximum LED drive current as input parameters. It then determines the required minimum number of LEDs to meet the provided specifications. Moreover, it calculates the usable light (lm), the usable efficacy (lm/W), and the total power consumed by the LED-based system (W), among other output parameters.

The following are the SSL designer analysis results that meet the commercial refrigeration target specifications:

• Input Parameters: After selecting the target market and application, a uniform illuminance of 1300 lux is set to illuminate a square surface of 1.524m by 1.524m (60in by 60in). The input section with the set parameters is shown in Figure 3.

• LED System vs. Conventional Lamp System Performance Comparison: After entering the application input parameters and basic information about the light source, SSL Designer calculates required LED system performance, including the LED count and drive current. In addition, the tool calculates the performance of a conventional lamp system that meets the same specifications. Figures 4 and 5 show the performance calculations of both cases respectively. The results state that 48 LEDs (12 LEDs in 4 strips) driven at 350mA current are required to meet the specifications of light output, efficacy, and lifetime, while maintaining the junction temperature at an acceptable value for suitable LED operation. The total power consumption of the LED system was 61.46W, after losses, while that of the conventional lamp system was 272.94W. This shows the significant improvement achieved, in terms of power consumption, when using LEDs in commercial refrigeration applications.

Figure 3. SSL Designer Input

Figure 4. LED System Performance

Figure 5. Conventional Lamp System Performance



• LED Payback: One more feature in the tool is to calculate the payback of leveraging an LED system as compared to a conventional lamp system. After defining cost information for both systems, the tool produces payback information such as power savings, cost savings, and payback period. Figure 6 shows that the payback period for using an LED-based system in the commercial refrigeration light strips is 1.9 years.

Note: The above SSL Designer case is available as a default scenario that can be loaded in the tool and used as reference. Under “Target Application” select “Comm. Refrigeration – 2-Door Fridge (FLS AN031)” to load all case parameters.

3. lUXeon leDs12 Neutral White LUXEON Rebel LEDs were used in the commercial refrigeration light strips (p/n. LXML-PWN1-0100).

A significant increase in performance, of about 15%, will be achieved when the new LUXEON Rebel Illumination Portfolio LEDs are incorporated in the design. This is due to the improvements in the hot/cold factor, which generates increased light output at higher junction temperatures.

Generally in LED lighting, there is a trade-off between high flux and high CRI. For instance, both the LUXEON Rebel LXML-PWN1 and LXM3-PW51 LEDs are rated to provide a nominal CCT of 4000K, which meets the target CCT indicated in Table 1. If the application requires a high flux output, but no strict requirement for CRI, the LXML-PWN1, which provides a minimum luminous flux of 100 lumens, can be used. Conversely, if a high CRI is required by the application, the LXM3-PW51, which provides a minimum CRI of 80, can be used. Moreover, all the CCT bins for the illumination portfolio LEDs are ANSI compliant.

3.1. Board Design and leD connections

The 12 LEDs are connected in series on an FR4 board with thermal vias. The board dimensions are 1500mm x 10mm (59.1in x 0.4in), with 0.8mm thick FR4 and 2oz Copper. The extrusion with the board mounted in place is shown in Figure 7.

Figure 6. LED Payback

Figure 7. Light strip with LED board



4. optical SolutionsThe extrusion for the commercial refrigeration light strips was designed to have a dual role, namely optical and thermal. The extrusion design, where the LED board is mounted eliminates the need for an additional heat sink. Also, the precise shape of the extrusion helps direct the light from the LEDs to illuminate the required sections of the refrigeration unit, thus not requiring the use of secondary optics.

4.1. optical Simulations and MeasurementsAn optical simulation was performed to evaluate the performance of the light strips.

Figures 8 and 9 below show the illumination and the Rayset coverage of LED light strips, respectively.

In addition, optical measurements were performed on the LED strips to measure the light levels achieved in the refrigeration unit. With 12 LEDs per strip, the following are the measurements results:

• Minimum illuminance: 1106 lux

• Maximum illuminance 1881 lux

• Average illuminance: 1531 lux

• Uniformity: 0.72

Figure 10 shows all the illuminance values obtained from the optical measurements.

Figure 8. Optical simulation results showing illumination coverage Figure 9. Optical simulation results showing Rayset coverage

Figure 10. Lux values from optical measurement



5. thermal SolutionsAn Aluminum 6063 extrusion strip with oxidized surface treatment, of dimensions 33mm (L) x 22mm (H), was leveraged to mount the LED board on.

5.1. thermal Simulations and Measurements A thermal simulation was performed to evaluate the overall thermal performance of the fixture. QLED Thermal Simulation software (www.futurelightingsolutions.com/qled) was used to model the fixture and perform the simulation, as shown in Figure 11.

The QLED model was run with a forward current of 350mA, and ambient temperature of 5°C. The resulting junction temperature of the simulation was 32.3°C

The thermal performance of the fixture was also analyzed at different drive currents using QLED thermal simulation software. The following table summarizes the results of these simulations:

Note: for these simulations TAMB= 5°C

Current (IF) Junction Temperature (Tj)

350mA 32.3°C

500mA 45.3°C

700mA 63°C

Table 2. Results summary of QLED simulations

The results in Table 2 above show that, even at higher drive currents, the junction temperature is maintained within acceptable values for suitable LED operation.

Figure 11. QLED thermal simulation of one light strip



6. power Solutions

6.1. Modular Driver SolutionsEach LED strip is connected to a 15W AC-DC ROAL TROPO driver, shown in Figure 12, with an output current of 350mA and an output voltage of up to 48V.

Two versions were included to accommodate regional input voltage differences, i.e. 120V and 230V versions. The part numbers of the drivers used are:

• 120V: RLDD015L-350

• 230V: RLDD015H-350

6.2. ic-based Driver SolutionsOther driver solutions are possible for the commercial refrigeration light strips. These solutions can be a single stage AC-DC option or even a 2-stage AC-DC/DC-DC option.

The single stage options include:

• 1 driver per strip – SSL1523 or SSL2101, by NXP, to drive one strip

• 1 driver for all strips – NXP SSL1750, by NXP

Whereas the 2-stage option, shown in Figure 13, includes:

• Constant voltage AC-DC stage – SSL1750, by NXP, can be used for the AC-DC voltage mode stage (with an output voltage of up to 48V)

• Constant Current DC-DC stage – LM3402HV, by National Semiconductor, for the DC-

DC current mode stage, which can be mounted on the commercial refrigeration strip board directly

Figure 12. ROAL TROPO LED driver Figure 13. (a) NXP SSL1750 AC-DC driver (b) 4 National LM3402 DC-DC drivers



7. connectorsDifferent connector systems can be used with the commercial refrigeration lighting system to adapt to different design setups. The following is a description of the connector system used in the demo kit as well as other possible connector systems:

• Tyco hermaphroditic connector system

The demo kit includes a hermaphroditic connector system by Tyco Electronics that is integrated to the LED boards and used to connect the light strip to the power drivers.

A section of the connectors system used is shown in Figure 14.

The low profile connector system includes wire-to-board connectors and board-to-board connectors which are designed to make connecting of circuit boards faster and easier. The connectors support crimp snap contacts and positive latching for a secure connection. The hermaphroditic blade and receptacle design allows LED board strips to join with more flexibility. The capability to slide the two boards together vertically makes replacement of a board in mid-strip easier.

The part numbers for the Tyco hermaphroditic connector system used are:

i. Board-to-board hermaphroditic connector: 2058703-1 ii. Board-to-board connector dust cover: 2058128-1 iii. Wire-to-board housing: 2058299-1 iv. Wire-to-board socket contact: 2058302-1 v. Wire-to-board blade contact: 2058301-1

The other connector systems that can be used with this design include:

• Tyco sealed connector system

The sealed connector system, shown in Figure 15, is a low profile, single row LED connector system that offers ingress protection up to and including immersion in 1 meter of water for 30 minutes (as per IP67). The part numbers for this connector system are:

i. Wire-to-board right angle header: 2106056 ii. Wire-to-board vertical header: 2106053 iii. Wire-to-wire receptacle contact: 2106123 iv. Wire-to-wire tab contact: 2106124 v. Plug assembly (for header, recept., tab): 2106135

• AVX 9159 connector system

The AVX connector system, shown in Figure 16, offers board-to-board connectors for daisy chaining multiple LED boards together in series. The part numbers for this connector system are

i. Wired plug with latch: 11-9159-002-101-116 ii. Standard socket: 20-9159-002-101-116 iii. Standard plug: 10-9159-002-101-116 iv. Top loading socket: 22-9159-002-101-116 v. Shorting socket: 58-9159-002-000-006

Figure 14. Tyco hermaphroditic connector system

Figure 15. Tyco sealed connector system

Figure 16. AVX 9159 connector system



8. conclusionThe commercial refrigeration lighting system leveraging LUXEON Rebel LEDs developed by Future Lighting Solutions has proven to satisfy the requirements of light output, efficacy, and lifetime to enable lighting applications in the specialty lighting market.

The thermal and power solutions offered are geared towards optimal performance and longevity of the LED-based system. The design can accommodate different power solutions depending on the specifications required.

contAct inforMAtion

www.FutureLightingSolutions.com

In North America: 1-888-LUXEON2

[email protected]

In Europe: 00-800-44FUTURE

[email protected]

In Asia: +800-LUMILEDS

[email protected]

In Japan: +81-0120-667-013

[email protected]

Future Electronics and Future Lighting Solutions make no representation or warranty, express or implied, as to the accuracy, completeness, reliability or timeliness of the information provided herein. Any and all information is furnished on an “as is” basis and only as an accommodation to customers and not based upon any legal or contractual obligation to do so. Conclusions drawn from or actions undertaken on the basis of such information are the sole responsibility of the user. Future Electronics and Future Lighting Solutions specifically disclaim any liability or responsibility for any information provided herein or for any loss or damage resulting from the use of or reliance upon any such information.

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