[Deep Analysis] Reasons for choosing a modular LED driver

What are the risks of a custom drive? Why is a ready-made LED driver a better solution?

The content of the LED driver specification is usually very attractive, and the manufacturer promises to provide good performance and rich functions on a low price basis. However, in practical applications, there are many potential obstacles that are not mentioned in the specification, which may cause serious problems for developers. In addition, the development, testing and certification of LED drivers are time consuming and costly, especially for AC/DC LED drivers. Off-the-shelf and tested modules save on the high cost of research and development, which can save at least 80% of the design cost.

Modular VS Discrete: Overview

Traditionally, discrete LED drivers are more cost effective than modular solutions. However, it is not. If the price comparison is based only on the cost of the BOM (bill of materials), the price of the modular drive is higher than that of the discrete LED driver. But this is not a fair comparison, because the actual application cost of the discrete solution is much higher than the cost of the statistics in the BOM. In addition, it should be considered that the LED driver is usually the last component defined in the design process, and therefore time becomes a pressing factor.

Deciding whether to adopt a driver module or not is based on facts. The following questions must be considered:

1) Design

Companies must be well aware of whether they do have engineering staff and know how to develop a complete discrete solution. The modular drive is a plug-and-play product that can be easily integrated into the lighting system, reducing time-to-market. In addition, the cost of research and development of discrete solutions may be significantly higher than expected, as it may be necessary to redesign in the future. This makes it easy to calculate that the overall cost of a discrete solution may exceed the certified LED driver module.

2) Assembly / warehousing

For assembly and warehousing, it is very necessary to operate. With a modular solution, manufacturers only need to purchase a single component from a single supplier. This minimizes logistics costs and makes production more efficient because it is easy to assemble. Manufacturers benefit from a stable product quality and do not need to consider tolerances between components. And because of the lack of a material (such as capacitors, inductors, resistors, etc.), the risk of production stoppage is almost eliminated at the same time.

3) Certification

Certification of LED drivers is a very time consuming process and the cost of certification is high. In order to obtain the required certification, the component must be repeatedly applied after the test failure, and this situation is more common. The result is that it not only adds additional redesign costs, but also takes a lot of time. And if you choose a modular LED driver, there is no problem with certification and unexpected difficulties.

4) Reliability

Reliability will affect the overall image of the brand as well as warranty issues that are closely related to it. Although the company has the potential to accurately determine MTBF, it may not be able to use expensive systems for reliability and service life testing. Regardless of the development process and the associated time/cost factors, the manufacturer must decide whether he wants to rely on internal design or whether he or she wants an experienced supplier to provide products that have been certified to make him feel safer.

If the company still decides to move on to a discrete approach, it is often based on the following considerations:

●With development capability and time

●The number of products required is very large, such as transformation

●The long service life of the product, such as >20 years

In all other cases, a complete assembly and the use of tested and certified LED drivers remains the most cost-effective solution.

You can't find all the parameters you want in the specification.

The description of the specification of the LED driver usually contains a series of features that are very attractive to the customer. Simply browsing, you will feel that the manufacturer has promised a good drive solution that can be quickly implemented and fairly easy to implement. However, potential pitfalls are hidden in the details, as shown in the following example:

1) Efficiency & temperature

Most specifications are accompanied by a series of characteristic charts (Figure 1) to show the high efficiency of their drives. To accurately determine the performance limits of the IC and the characteristics between the temperatures, a more in-depth analysis is required. For example, this can be analyzed by a power consumption derating diagram (Figure 2). The curve in the figure, if the included features have been fully reflected, is generally found in the very part of the specification. The relationship between power consumption, maximum operating temperature and actual IC power can be best explained by the following two examples:

a) Vin (input voltage) = 12V, 3x1WLEDs output:

Based on the efficiency characteristics (red curve in Figure 1), this configuration achieves 90% efficiency. That is to say, the power consumption is 300mW (calculation: 3x1Wx10%). The power derating curve (Figure 2) shows that the maximum operating temperature for this configuration is around 80 °C. The drive has performed very well so far.

Figure 1 Efficiency versus input voltage and load curve

b) Vin (input voltage) = 24V, 5 x 1W LEDs output:

In this case, the driver efficiency reached 92% (yellow curve in Figure 1) and the power consumption was 400mW. However, according to Fig. 2, the maximum operating temperature in this state can only be 40 °C.

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