Is it easy to easily renovate an LED driver?

LED lighting is a near-mainstream technology. The replacement LEDs allow property managers and owners to take advantage of the traditional power infrastructure to enjoy the long working life and energy efficiency of LEDs. Local area networks (LANs) are installed in these environments, and Power over Ethernet (PoE) technology provides unprecedented ability to dynamically monitor and control each LED light as well as intelligent LED lighting/sensor concentrators.

In 2015 and beyond, LED will definitely drive the design of lighting systems

A light emitting diode (LED) is a semiconductor device that emits light when passing current. The application advantages of LEDs are constantly evolving and maturing, making them the first choice for more and more traditional and new lighting applications.

The advantages of LEDs include longer working life, higher energy efficiency (lumen/watt) and a small form factor. For example, LED lamps have a working life of 50,000 hours, far exceeding the typical working life of 1,000 to 2,000 hours for incandescent lamps, and 5,000 to 10,000 hours for compact fluorescent lamps (CFLs). Therefore, LEDs are well suited for a wide range of commercial and industrial applications, where energy efficiency is required, and contact/safety risks and high labor costs are not conducive to replacing lamps. The brightness of a 10W LED lamp is equivalent to about 60W incandescent lamp, which makes the LED lamp use and maintenance cost much lower. LEDs can be used with conventional luminaires such as the MR16; they are ideal for replacing these pedestals, providing longer time and more energy efficient lighting.

The wavelength or color of the LED illumination depends on the materials used in the LED construction. With the right driver, LEDs offer greater design flexibility for dimming and changing the color of the luminescence. When used with suitable controllers and sensors, the amount and color of the light can be adjusted according to changes in the environment. This capability makes it ideal for indoor lighting as well as applications such as dimmable street lights and outdoor lighting, changing its brightness depending on ambient light changes. LED dimming saves about 1:1, so dimming the LED to 50% will save about 50% of the energy.

Designers continue to apply LEDs to a growing variety of lighting applications. We discuss LED applications in two scenarios. Designers use LED modules in traditional luminaires, such as the MR16, which must work with existing power infrastructure to take advantage of LED lights. In contrast, Power over Ethernet (PoE) LED lighting networks use new or parallel power infrastructure. Before discussing these application spaces, let's briefly review the LED drivers.

Figure 1: LED driver converts the input voltage to the level required by the LED

LED driver

The LED driver is a low voltage component that converts the input voltage, such as 120V, 220V or 277V, to the low voltage required by the LED. These drivers also parse the control signals, dim, brighten, and change the illuminating color (Figure 1). The LED driver can be configured with a constant current (eg 350mA, 700mA or 1050mA) or a constant voltage (typically 12V or 24V). These two types of drives are not interchangeable. The luminaire manufacturer selects the drive type and configuration to match the electrical requirements of the LED modules used in the luminaire. In this paper, we discuss the constant current driver as an example.

The constant current driver supports Pulse Width Modulation (PWM) and Constant Current Dimming (CCR) to regulate the output current during LED dimming. LED applications require a constant current to ensure that the LED lamp output remains constant as the input voltage fluctuates. LED drivers not only drive high-end and low-end illumination, but are also responsible for continuous or step dimming. The designer matches the drive to the LED according to various combinations of application requirements, including the number of LEDs driven, the type of power supply, and the functional characteristics of the LED. Matching or poorly implemented LED drivers can actually shorten the operating life of the illuminator, causing unpredictable lighting problems, such as flicker.

If the amplitude and/or frequency of the LED illumination is periodically modulated or fluctuated (unpredictable), the human eye will sense it. If the input current changes rapidly and the LED lamp output changes rapidly, the LED is prone to flicker. There are many causes of flicker, including power supply noise, control noise, component tolerance, and LED driver circuit design issues.

A good LED driver design should consider all internal and external factors to provide a constant, non-oscillating current to the LED for flicker free dimming.

Renovation

The longer life and higher efficiency of LEDs make them ideal for replacing other lighting technologies, especially incandescent and halogen lamps. There are two main challenges when using LEDs for existing lighting infrastructure. First, the replacement lamp must conform to the dimensions of a conventional light source; secondly, it must work correctly without flicker in an existing electrical infrastructure environment.

Mounting the LED to an existing form factor, such as the MR16 (Figure 2), not only limits the size of the driver board, but also the thermal issues of the design itself.

Figure 2: MR16 size luminaires are retrofitted to LED versions