The Chip-on-Board (CoB) format for the packaging of high-power LEDs for lighting is enjoying a spectacular surge in popularity. Just like discrete LEDs assembled by the user on a user-designed board, CoB LED modules consume less energy than any other light source, providing a combination of high brightness, good light quality, robustness and long life.
When using a CoB, however, the lighting equipment manufacturer does not need to call on any special expertise in the design and assembly of electronic circuits, as it would do if using discrete LEDs. Instead, CoB modules are supplied as a fully integrated solution: the bare LED chips are mounted directly on a thermally-efficient substrate (made of alumina or ceramic), and are covered by a phosphor overlay to produce a light output of the required colour temperature. The whole assembly is normally mounted in a housing with a convenient footprint, mounting points and terminals, in many cases conforming to the LED industry’s Zhaga standard. CoB LED modules, then, make it easy for lighting equipment manufacturers to implement new LED lighting designs without having specialist electronics expertise. Can the implementation of a power supply for CoB modules be as straightforward?
In fact it can. Power supply manufacturers have been providing integrated LED drivers already for many years. Common features in these drivers include:
- accurate regulation over a wide input-voltage range
- various protection features, including thermal and current overload and short-circuit protection
- support for dimming and control functions, including standard protocols such as DALI
To implement such an integrated power supply in an LED design calls for no more than the connection of a power input at one terminal, and of the LEDs at the other. It is by design a ‘Plug and Play’ type of device.
Tailor-made drivers for CoB LED modules
Now, the industry is extending the choice of off-the-shelf power supplies available to lighting equipment manufacturers to include power supplies optimised for use with CoB LED modules. Recom is one of the leaders in the field of CoB LED power supplies with its RCOB series of drivers. The series includes 11 models with output voltages ranging between 25V DC and 44V DC, and offering constant-current outputs between 350mA and 1,050mA. This meets the requirements of the vast majority of CoB LED modules available today from manufacturers such as Lumileds, Bridgelux and LG Innotek.
The affordable RCOB drivers come with active power factor correction and provide a power factor rated at more than 0.95. Power-conversion efficiency is as high as 90%. Thanks to their compact and flat design, measuring 106mm x 67mm x 22mm, the drivers can be accommodated in most types of lighting system.
The inputs and outputs are located on the same side of the driver to make assembly easy. The RCOB-A versions of the series also come with a 1-10V input, and may be dimmed from 100% to 0% of maximum light output. Designed for the European market, the RCOB series’ input voltage is a nominal 230V AC (198-264V AC). The drivers’ operating temperature range is -20°C to 50°C. A number of safety features are provided in the drivers, to protect them against short circuits, overload, over-voltage and overtemperature, helping to ensure maximum availability and reliability. The RCOB LED drivers come with a three-year warranty. More information can be found at www.recom-international.com.
The advantages of CoB modules in LED lighting
- CoB modules enable the manufacturer to achieve high light density, since many LEDs may be mounted in a small area. This is possible in part because of the excellent heat-conducting properties of the CoB substrate. • The low thermal resistance of CoB modules helps to prolong the LEDs’ operating life, because it reduces the rate of degradation attributable to heat. • CoB modules produce less glare – that is, a less dazzling effect – than a discrete LED assembly. CoB modules produce a homogeneous light output, with no detectable variance in colour temperature. • The round shape of a CoB module’s Light-Emitting Surface (LES) also produces high uniformity in the beam, close to a value of 1. The same applies to the rotational symmetry of the LES. • The manufacturers of CoB modules are supported by a complete ecosystem of suppliers which provide the other elements of a CoB-based lighting fixture, including sockets, optics, connectors and drivers. All are available from Future Lighting Solutions, the sister company of Future Power Solutions.
