The basic structure of the LED lamp is a piece of electroluminescent semiconductor material, placed on a leaded rack, and then surrounded with epoxy resin to protect the internal core wire, so the LED has good shock resistance. LED is a fast-developing technology, which is widely used in many general lighting fields, usually called solid-state lighting. Typical applications of LED lighting are: indoor lighting (for commercial, industrial, and residential environments), outdoor lighting (street lights, parking lot lighting), and architectural, decorative lighting, etc. Initially, light-emitting diodes were used because they can emit colors across the entire spectrum Used for decorative lighting.
In some cases, LED has become an effective solution for architectural lighting. Compared with other lighting technologies, LED has more excellent performance, so it has become the mainstream solution in the current general lighting market:
1. Compared with other lighting technologies, LED has a longer service life. The working life of LEDs is up to 50,000 hours, while the service life of incandescent lamps is only 1,000 to 2,000 hours, and the service life of small fluorescent lamps (CFL) is about 5,000 to 10,000 hours. The significant advantages in service life make LEDs very suitable for commercial and industrial applications that require large labor costs to replace the lighting.
2. Energy efficiency is better than incandescent and halogen lamps, and is equivalent to fluorescent lamps. In addition, the efficiency of LEDs is also constantly improving; the efficiency of white LEDs (WLEDs) is expected to increase by about 50% in the next 3 to 4 years.
3. Smaller dimensions. The external dimensions of LED lamps are equivalent to MR16 and GU10, and CFL cannot meet such applications.
4. A suitable driver can be used to provide brightness adjustment. For applications that require brightness adjustment, fluorescent lamps have technical limitations. Although traditional LED designs have encountered similar problems, the innovative LED driver solutions provided by Maxim are compatible with SCR dimming and trailing edge dimming designs.
5. Has strong directional light emission. Unlike other lighting technologies, LEDs are ideal for applications that require directional lighting, such as small-angle reflector lamps.
6. Higher efficiency at lower temperatures. The working efficiency of fluorescent lamps will decrease at low temperatures. In contrast, LED is very suitable for low temperature working environment, such as: refrigerator light.
7. Can easily change the light color. This advantage makes RGBLED an ideal choice for architectural and scene lighting, and can change the color of the light in real time according to specific requirements.
In short, LED has many advantages that incandescent and fluorescent lamps do not have. Based on these advantages, designers are constantly exploring more applications suitable for LED lighting, but due to limited space, we will not repeat them here. This article will mainly discuss the replacement products of LED lighting for replacing incandescent, halogen or fluorescent lamps of the same specifications. These LED lights must be able to be installed within existing specifications and compatible with existing infrastructure.
LED replacement lamp
Many people believe that LED replacement lamps are currently the fastest growing market for LED lighting. The reason for the rapid growth is simple: these lights do not need to update the electrical infrastructure (ie wiring, transformers, dimmers and sockets), which is a significant advantage of LED technology.
For designers, there are two main challenges for installing LED lights on the existing infrastructure:
1. Dimensions.
The replacement lamp must be able to be installed in the framework of the previous lamp source.
2. Electrical compatibility. The replacement lamp must be able to work properly on the existing electrical architecture without flickering.
Below, we will discuss each challenge one by one.
Mounting to an existing frame The existing frame imposes physical restrictions on the replacement lamp (ie the driver board must be small enough) and thermal restrictions. These factors restrict the conditions for designers to change lighting solutions (such as PAR, R and A specifications), and the smaller the size, the greater the difficulties faced by applications, such as MR16 and GU10.
Size is the key factor restricting the replacement scheme, and thermal limitations are often more critical. LEDs only emit visible light. Unlike other technologies, they do not generate infrared radiation energy. Therefore, white LEDs are more energy efficient than incandescent or halogen lamps, and most of the heat is dissipated through the inner conductor of the lamp.
Heat dissipation is a key factor restricting the intensity of light that can be produced by the lamp. At present, the LED technology used in lighting replacement products is difficult to reach the brightness level acceptable to the mainstream market. In order to break through the brightness limitation, it is necessary to solve the heat dissipation problem, which is also an indispensable condition for the successful commercialization of the product.
The heat dissipation problem also directly affects the service life of the driver board. In order to emit higher light intensity, the lamp must be operated at a relatively high temperature (+ 80 ° C to + 100 ° C). At this temperature, the life of the driver board will limit the work of the entire lighting lamp, especially the electrolytic capacitor has become a difficult problem facing the design. Because electrolytic capacitors will dry quickly at high temperatures, under such conditions, the working life of such capacitors will not exceed thousands of hours, which has also become a factor restricting the service life of the entire lighting lamp. Longer working life is a major selling point of LED lamps. For designers, electrolytic capacitors with relatively short lifespan become the main barrier for design.
Maxim has introduced a unique LED drive solution for 120VAC / 230VAC input and 12VAC input replacement lamps. These LED driving schemes can save the electrolytic capacitors on the circuit board, and extend the life of the LED lamp from the usual less than 10,000 hours to 90,000 hours. Since the electrolytic capacitor is omitted, it also helps to reduce the size of the solution, so that the driving board can be installed in a small-sized replacement lamp frame.
Compatible with electrical infrastructure
The LED replacement lamps must work properly under the existing infrastructure, including corner dimming (triac and delay) dimmers and electronic transformers.
When connected to 120VAC / 230VAC power supply, the lighting can be adjusted first through the triac dimmer. The design of the triac dimmer can work well with incandescent lamps and halogen lamps, these lamps are purely resistive loads. However, when using LED retrofit lamps, the LED driver is usually a non-linear, impure resistive load, and the input bridge rectifier usually absorbs a large current transiently when the AC input voltage is in the positive and negative peaks. The triac dimmer cannot guarantee this requirement of the LED, because it can neither provide the required starting current nor the holding current. As a result, the dimmer cannot start normally or shut down normally during operation, and it also causes the LED to flicker, which is also an unacceptable phenomenon of the system.
As a replacement product, its electrical architecture is more in line with the design of 12VAC input lighting, because the electronic transformer and the trailing edge dimmer can be connected to the input of the lighting. However, the driver of the 12VAC input lighting uses the traditional bridge rectifier and DC-DC converter topology. Due to the incompatibility of the transformer and dimmer, flicker will also occur. The bridge rectifier is connected by four rectifier silicon chips, and the bridge rectifier plays a big role here.
Maxim's 120VAC / 230VAC and 12VAC input lighting solutions use single-stage conversion.
By shaping the input current, the lighting lamp will not flicker under the dimming state. These solutions are compatible with the design of bidirectional triac and trailing edge dimmer and electronic transformer. At present, no MR16 solution has this feature, and few PAR, R, and A lamp solutions have this feature. In addition, our solution has power factor correction better than 0.9 and requires very few external components. No electrolytic capacitors are needed, and these capacitors will severely restrict the operation of the driving circuit in a high-temperature environment. Both the 120VAC / 230VAC and 12VAC solutions use MAX16834IC, which can be used by users to estimate and put into mass production. These are Maxim's unique solutions, and Maxim is also the only supplier that can provide this combination of advantages.
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