LED lighting has lit up the electronics industry in terms of growth: In 2011, the market for lamps and luminaires based on LEDs grew by 69% to $9.4 billion, according to research firm Strategies Unlimited. Expectations show an expansion rate of 20% annually from 2011 to 2016, with the commercial and industrial lighting sector leading the charge.
This growth trend encompasses more than just the range of light sources. It also means dramatic changes in the nature of the supporting electronics, particularly connectors. They’re required to combine a number of LEDs into an integrated emitter or module, and interface the resulting light source with power and control signals from the outside world.
Though historically known to be electronically simple, lighting applications are, by virtue of their ubiquity, extremely diverse. This means that the components involved often must fit two sets of design requirements: those earmarked strictly for use in LED lighting, and those necessitated by the circumstances and environment in which the connector will be deployed.
For example, a domestic LED emitter design typically needs to fit into an existing physical lamp configuration, presenting special size and thermal-management constraints. However, a product intended for outdoor use, such as in architectural lighting, will also have to resist moisture ingress and more severe temperature fluctuations.
A well-defined set of design requirements for LED lighting applications typically revolve around size constraints and cost pressures, because lighting solutions are moving from purely electrical to electronic. On that front, simplicity is important—people expect changing a light bulb to be easy, and they believe that ease should run throughout the system. Lighting also tends to require connectors that deliver long service life and relatively few mating cycles.
Standard And Lighting-Specific Connectivity Options
In mass-market applications, LED lighting manufacturers face intense pressure to reduce costs. There’s also pressure to create easy-to-assemble interconnect systems that maintain in situ. Even high-efficiency LEDs dissipate substantial amounts of heat amongst an ever-widening array of lighting environments. Connectors must continue to function reliably when encountering high temperatures for sustained periods.
Thus, despite the fact that lighting is seen as a relatively simple application, choosing the right connector type and construction material can be quite a challenge.
The diversity of environments and physical form factors creates multiple options for designers to explore. At one end of the spectrum, standard board-to-board, wire-to-board, and wire-to-wire interconnect systems may be suitable. Sometimes, manufacturers modify these versions specifically for lighting applications. But suppliers have also created LED-specific connectors, often as custom components for particular lamp styles.
The most important factor is to ensure that the particular application drives the specification. The vast majority of applications can be satisfied with standard connectors, or customised cable assemblies created from these parts. However, a lighting-specific part may be right for a certain situation. For instance, the requirement may be extreme ease of assembly.
Outdoor, Stage, And Studio
One well-established area for LEDs is in stage and studio lighting. Lighting designers value LEDs’ greater flexibility in creating special effects whilst eliminating the problems caused by excessive heat and high power consumption of conventional lamps.
The challenge in these applications is often to combine rugged construction with ease of assembly and high mating/demating tolerance. A minimum of IP65/67 rating is essential, as is a degree of strain relief within the connector’s physical design to counter the risks of everyday use.
For instance, a system like Amphenol’s “Ecomate” circular connector can be a good fit for such requirements (Fig. 1). Originally developed for use in plant construction and machine building, it exemplifies a product type that’s been re-purposed for lighting applications.
The connector, featuring a rugged, moulded housing, is designed for quick assembly. It comes with a screwed cable gland, clamping ring, and combined strain relief and mounting gasket, as well as offers the necessary IP65/67 rating.
LED lighting also is seeing high adoption rates within the world of architectural lighting. In these applications, the connector often needs to withstand even more extreme conditions, e.g., total water immersion and wide ambient temperature variations. Amphenol LTW’s outdoor waterproof connectors, developed originally for military and aerospace applications, are being repurposed for LED lighting.
Specialisation With Lighting-Specific Connectors
Frequently, LEDs must be fitted into an existing standard form factor, at which point designers can opt for lighting-specific connectors. For this scenario, AVX developed a range of devices for low-power dc-dc interconnects—the9159, 9175, 9176, and 9177 series wire-to-board connectors and the 9608 and 9609 series of board-to-board connectors.
The 9608 and 9609 parts, specifically designed for LED applications, offer a 1.4mm mating height, claimed as the lowest in the industry. The low mating height matches the height of an SMD LED. As such, the connector can be positioned very close to the LED without causing a shadow.
The 9159 particular suits end-to-end stacking of boards in LED lighting strips. The strips’ low 3mm height and 5.5mm overall mated length enable the production of very compact lighting products. The connectors, with contacts rated at 125 V ac at 5 A, come in 2- to 6-pin versions, accommodate wires sizes from 22 to 24 AWG, and require no special tools for installation. They feature a locking clip for greater reliability.
Another entrant in this category is the Hirose DF59 multifunctional system, which has a mated profile of just 2.5mm (Fig. 2). Available in wire-to-board and board-to-board versions, only one type of receptacle is needed (whether the cable plug or board mount plug), reducing the number of required components. The 2- to 6-position connectors have an overall size of 8mm by 9mm, preventing shadows in LED lighting strips.
While form factor is often an absolute constraint in lighting applications, so too is the need to maintain safety standards. In particular, when using mains power, the designer must be aware of creepage (insulation distance along a surface) and clearance (insulation distance through air) standards. Like many connector ranges, the Hirose DF59 features a 2mm or 4mm pitch to accommodate these requirements.
As mentioned, quick and easy assembly often is a top priority in the lighting market. Solderless interconnect systems, for example, help accelerate and de-skill assembly tasks, leading to reduced costs in the creation of LED emitter and module assemblies.
Along these lines, TE Connectivity developed the SMIZ series solderless LED sockets, designed for use with Sharp’s Mini Zenigata LEDs. They allow LEDs to directly attach to a heatsink using two standard M2 screws. Similarly, the company’s Poke-In wire connectors offer ease of assembly in LED lighting fixtures. They come in 1- or 2-pole, through-hole, or SMT versions, and each contact is rated at 250 V ac, 5 A.
A Familiar Feel With Standard Connectors
While lighting-specific connectors provide a tailored solution to a defined problem, many designers prefer to stick to proven solutions if possible. The immense diversity of lighting applications, together with the vast portfolio of standard connector types, means that there’s often a standard product available which is fit for purpose.
Perhaps connector height isn’t a critical consideration, but there’s a desire to minimise inventory. Samtec came up with hermaphroditic board-to-board self-mating and board-to-board power connectors for just such a situation (Fig. 3). These shrouded and polarised connectors minimise the number of discrete parts within the interconnect system. An audible click confirms that they’re properly mated, speeding up assembly.
In other cases, even more familiar connectors—e.g., DIN 41612 and D-types—can also be used in solid-state lighting. The same is true for standard ribbon-cable connectors. such as those in FCI’s FFC/FPC/CIC families. The company’s modular jacks are often employed in data and power-over-Ethernet (PoE) connections between intelligent LED modules.
Special Needs For Specific Apps
Many applications present very particular connectivity requirements. Look no further than automotive and roadside lighting, which has special requirements driven by safety standards and approvals. These requirements often overshadow the elements of the specification derived from a connector’s use with LEDs.
For instance, Molex’s passive safety-pole connector (Fig. 4) was designed to meet new European requirements, which state that all roadside lighting and electrified signage must have a power quick-disconnect system. Much of this lighting and signage is now LED-based to reduce operating costs, both through saving energy and reducing maintenance requirements. To comply with the legislation, the connector system must disconnect the electrical supply to the pole or sign within 0.4 seconds of an impact.
Molex’s connectors, which are IP68-sealed and have a waterproof cap and built-in pole fixing strap, come pre-assembled with their cables. They’re designed for street lighting, traffic lights, traffic bollards or posts, or any other power-consuming system along roads.
Often, the challenge for designers making and using LED lighting products is not in finding a suitable connector, but rather selecting the right part from a myriad of choices. This is where a good distributor, who is familiar with the comparative strengths and weaknesses of connectors from a variety of manufacturers, can help simplify the process of creating a cost-effective, reliable LED lighting system.