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Zhaga Consortium responds to evolving requirements of LED industry

Posted on Monday February 23 2015, by Tim Whitaker


This article was published in NEMA's electroindustry magazine, February 2015

Author: Tim Whitaker, Director of Marketing Communications, Zhaga Consortium

Download the article (PDF file)


As the international Zhaga Consortium evolves, it is listening to the voice of the lighting industry and responding with new initiatives. Zhaga was established to develop specifications for interchangeable LED light sources, and is now building on its initial success by addressing new areas that represent a consensus requirement from the market.

For example, based on feedback from luminaire manufacturers and component suppliers, Zhaga is developing a new specification for chip-on-board (COB) LED arrays. The consortium is also making progress with its efforts to enable the independent interchangeability of LED modules and drivers.

Several new Zhaga interface specifications—known as Books— are getting closer to completion, while new proposals are being evaluated, including specifications covering different types of replaceable LED light engines (LLEs).

At the other end of Zhaga’s Book development process, the consortium recently signed a liaison agreement with the International Electrotechnical Commission (IEC). This is expected to result in the publication of an IEC publicly-available specification (PAS)* based on Zhaga Book 3 for spotlight modules. Zhaga is also making sure that the set of parameters in each of its specifications will enable interchangeability without restricting design freedom, as requested by the market.

Chip-on-Board (COB) arrays

Zhaga recently announced that it is working on a new Book that will include COB LED arrays. Such products are currently used throughout the industry, but different manufacturers offer a wide range of alternative sizes. This creates problems for luminaire makers and other stakeholders, such as COB holder suppliers, and limits their options to use alternative products from different suppliers without changing their luminaire or holder designs.

“We consulted many luminaire makers and other stakeholders, and received broad support for our plans to standardize this type of LED light source,” said Zhaga Secretary General Musa Unmehopa. “These companies asked us to standardize properties such as the mechanical dimensions of the modules, the position of electrodes, and the diameter of the light-emitting surface.”

The new Zhaga Book will define LED light engines made up of rectangular and square LED modules with a circular light-emitting surface (LES) and a separate LED driver. The Book will define a family of modules with the following printed circuit board dimensions: 12 x 15 mm, 16 x 19 mm, 19 x 19 mm, 20 x 24 mm, 24 x 24 mm, and 28 x 28 mm. The circular LES sizes defined in the new Book will correspond to the LES categories specified in current Books covering spotlight modules.

Driver and module interchangeability

Based on feedback from the industry, Zhaga announced that it will aim to enable independent interchangeability of LED modules and drivers. Current Zhaga specifications only define the conditions necessary for interchange of a complete LLE (which includes both module and driver). In the cases where modules and drivers are separate, independent interchangeability would allow a luminaire maker to use a different compatible LED module without also having to use a different driver.

Independent interchangeability requires appropriate specifications that describe the driver-module electrical interface. Zhaga is now evaluating suitable specifications that have been created by external organizations. It is anticipated that such specifications will be normatively referenced in some of Zhaga’s existing and new Books, where appropriate. 

It is not unusual for Zhaga specifications to reference other standards. For example, NEMA SSL 7A-2013 Phase Cut Dimming for Solid State Lighting—Basic Compatibility has already been referenced by Zhaga Books 2 and 8, which describe socketable integrated LLEs.

Transfer of Book 3 to IEC

As a result of Zhaga’s recent liaison agreement with IEC, it is expected that IEC publications will be based on Zhaga interface specifications, beginning with Book 3 for spotlight modules, in conjunction with Book 1, which contains generic definitions. 

In addition, preparatory work is underway to transfer Book 3 into a PAS. In this case, it represents a consensus in an industrial consortium external to IEC. IEC will work with the current edition (1.3) of Book 3, together with Book 1, which contains information referenced by all Zhaga Books. Once transferred to IEC, future amendments will be considered, and commented and voted on according to IEC rules. 

Book updates

Among the new specifications being discussed and developed, Zhaga is close to completing Book 9. It covers LLEs composed of a non-socketable LED module with a ring-shaped LES and a separate LED driver. The small, mid-power LED modules have diameters of 12 mm or 25 mm for the ring-shaped LES, and could enable LED luminaire products for use in consumer
lighting applications, such as small spotlights, track lighting, and other compact luminaires.

Zhaga is also building on the success of Book 3, which defines 50-mm diameter modules for spotlighting applications. It is extending the range of spotlight modules to both larger (75-mm diameter) and smaller (35-mm diameter) sizes. These are currently designated Book 10 and Book 11, respectively.

Stakeholder value

In order to provide maximum value to stakeholders, Zhaga is undertaking a comprehensive review of the parameters included in each of its specifications. The goal is to ensure that the full parameter set of each Book includes all the characteristics necessary to enable interchangeability. 

The starting point was to create an exhaustive list of properties associated with modular LED light sources described in Zhaga Books. A number of luminaire makers and other stakeholders were asked to explain their requirements and preferences for each of the properties in order to determine which properties should be included in each Book. In some instances, this may result in additional parameters, or the removal of properties unrelated to interchangeability.

The characteristic properties of LED light sources were assigned to one of three groups (see Table 1). The first group includes properties not relevant to interchangeability, and are therefore not included in Zhaga specifications. Examples include performance characteristics such as luminous efficacy and properties such as choice of materials.

The second group of parameters includes those restricted by Zhaga specifications, such that little or no variation is allowed. Many parameters in this group relate to mechanical fit (e.g., size and position of screw holes). Another example is the maximum outer dimensions of an LED module and corresponding demarcation area in the luminaire.

The third group contains parameters where the value must be known in order for a customer to determine if one light source is interchangeable with another. For some parameters, such as those relating to thermal interface, Zhaga created precise definitions so that provided values will allow product comparisons and facilitate luminaire design. For other parameters, such as luminous flux, Zhaga Books require the product to be placed into one of a series of categories. This enables a customer looking for closely-matched interchangeable products to select from alternatives that are in the same flux category.

It’s important to note that Zhaga promotes design freedom by only restricting those parameters that are essential to ensure interchangeability. Many other properties are listed on the product datasheet, but their values are not restricted by Zhaga specifications, which allows maximum value-added differentiation. Furthermore, because Zhaga requires LLE manufacturers to provide a detailed set of parameters for each product, this allows luminaire makers to draw meaningful comparisons and informed choices based on dependable data.

By listening to feedback from stakeholders and responding in a timely and efficient manner, the Zhaga Consortium is continuing to provide an important contribution to the ongoing growth and development of the LED lighting industry.

* Footnote
A PAS is a publication responding to an urgent market need. The objective is to speed up standardization in areas of rapidly-evolving technology.