Analysis the challenges of LED lamp design

 LED is a fast developing technology, is widely used in many general lighting field, commonly referred to as solid state lighting. LED tube lighting is the typical application of indoor lighting: ( used for commercial, industrial and residential environment ), outdoor lighting ( lamps, parking lot lighting ) as well as the construction, decorative lighting, initially, light emitting diode due to launch the entire spectrum of color was used for decorative lighting.

In some cases, LED has become the effective scheme of building lighting. Compared with other lighting technologies, LED has more excellent performance, and thus become the general lighting market mainstream programme:

1.       Compared with other lighting technologies, LED has a longer service life. Working life of LED for up to 50000 hours, and the incandescent lamp service life of only 1000 to 2000 hours, compact fluorescent lamp ( CFL ) service life of about 5000 to 10000 hours. The service life of a significant advantage makes LED very suitable for those who need to invest more manpower cost replacement of lighting of commercial and industrial applications.

2.       better energy efficiency than incandescent lamps and halogen lamps, equivalent to the fluorescent lamp. In addition, the efficiency of LED has also been improved; the efficiency of white LED ( WLED ) over the next 3 to 4 years is expected to raise about 50%.

3.       smaller size. LED lamp dimensions are equivalent to the MR16 and GU10, and CFL cannot satisfy this kind of application.

4.        can adopt the appropriate driver provides brightness adjustment. The need for adjusting the brightness of fluorescent lamp, with the technical limitations. Although the traditional LED design also encountered similar problems, but Maxim provides LED drive innovation scheme compatible with the silicon controlled dimmer and dimmer design along.

5.       strong light direction. And other lighting technologies, LED is ideally suited to the needs of directional lighting applications, such as: small angle reflector lamp.

6.        when the low temperature with high efficiency. Fluorescent lamp work efficiency in the low temperature will drop. In contrast, LED is very suitable for the low temperature working environment, for example: refrigerator lamp.

7.       can easily change light color. This advantage makes RGBLED become the building and situational ideal lighting, according to the specific requirements of real time change of light and color.

8.       In short, LED has incandescent and fluorescent lamps do not have many advantages. Based on these advantages, design staff are also constantly explore for LED lighting application, however, due to limited space, we are not in this speech. This paper will mainly discuss LED lighting products, used as a substitute for the same specifications of the incandescent lamp, halogen lamp or a fluorescent lamp. These LED lamps must be installed into existing specifications and compatible with existing infrastructure.

LED replacement lamp

Many people believe that LED replacement lamp is currently the fastest growing LED lighting market. The rapid growth of the reason for this is simple: these lamps do not need to update the electrical infrastructure (wiring, transformers, dimmers and socket ), this is a significant advantage of LED technology.

For designers, LED lamp mounted to the existing infrastructure, there are two major challenges:

1.       dimension.

Replacement lamp must be able to install to the light source within the framework of.

2.       electrical compatibility. Replacement lamp must be able to in the existing electrical structure of the normal work, no flashing lights.

Below, we will discuss each of each challenge.

Mounted to the existing framework

  The existing framework on the generation of light presents physical limitations ( i.e. drive plate must be small enough ) and thermal limit requirements. These factors restrict the design personnel to replace the lighting programme conditions (such as PAR, R and A specifications ), the small size of the difficulties in applications will be large, such as MR16 and GU10.

  Size is the key factors restricting the replacement scheme, while the thermal limits are often more critical. LED only the emission of visible light, and other technical differences, they do not produce infrared radiation energy. Therefore, white LED than incandescent or halogen lamps more energy-efficient, the vast majority of heat through the light conductor dissipation.

  Heat dissipation is restricting the lamp can generate light key factors, present in the lighting products used in LED technology is difficult to achieve the mainstream market can accept the brightness level. In order to break through the brightness limit, need to solve the problem of heat dissipation, this product is also successfully commercialized essential condition.

 Heat is also a direct impact on the driver board service life. To emit a higher intensity, lamp must operate at relatively high temperatures ( +80° C to +100 °C ). This temperature, the drive plate life will limit the lamp work, especially electrolytic capacitor has become the design face a difficult problem. Because the electrolytic capacitor at high temperatures will soon dry, in such conditions, the capacitance of the working life of no more than thousands of hours, this has become restricts the entire service life of the lighting lamp factors. Long service life is LED lights one of the main selling points, designers, relatively short life of electrolytic capacitor design as the main barrier.

 Maxim for 120VAC\/230VAC input and 12VAC input replacement lamp launched a unique LED driving scheme. These LED driving scheme can save the circuit board of the electrolytic capacitor, so that the LED lamp life from the usual less than 10000 hours to 90000 hours. Due to the elimination of electrolytic capacitor, also help to narrow program size, the driving plate to be mounted to a small size replacement lamp frame.

 Compatible to the electrical infrastructure

LED replacement lamp must in the existing infrastructure work, including cut angle ( three triac and delayed ) dimmer and electronic transformer.

Access to 120VAC\/230VAC power supply, lighting firstly three triac dimmer control. The three end of the triac dimmer design is able to coordinate well with incandescent lamps and halogen lamps, these lamps are pure resistance load. However, the use of LED transform lamp, LED drives are typically nonlinear, non pure resistance load, input bridge rectifier is usually in the AC input voltage is positive and negative peak transient absorption current. Three triac dimmers can not guarantee LED of this demand, because it can not provide the required start-up current, cannot provide a holding current. Thus the dimmer does not start or when working normally closed, but it will also cause flashing LED, this is also the system cannot accept the phenomenon.

As a replacement, its electrical architecture more in line with the 12VAC input lighting design, because the electronic transformer and the dimmer can be connected to the lamp input. However, the 12VAC input lamp drive is used in conventional rectifier bridge and a DC-DC converter topology, because the transformer and dimmer incompatibility, will also produce scintillation.

Maxim 120VAC\/230VAC and 12VAC input lighting solutions using single level transformation.

The input current shaping, can make the lighting t8 led tube in the lighting States will not flicker occurs, these programs compatible with the two-way controllable silicon and the three end of the dimmer and electronic transformer design. At present, not a MR16 scheme has the characteristic, rarely have the PAR, R and A type light scheme has the characteristics of. In addition, our solution is better than 0.9 power factor correction, requires minimal external components. Without electrolytic capacitor, the capacitor under the environment of high temperature will seriously restrict the work of driving circuit. 120VAC\/230VAC and 12VAC solutions are used in MAX16834IC, available for users to * estimation and put into mass production. These are the unique Maxim scheme, Maxim is only able to provide the advantages of combination of suppliers.