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Intelligent LED Lighting Requires Innovative Control And Dimming

Apr 26, 2018

The challenges facing lighting designers The government's tightening of controls and consumer demand has made modern lighting designers increasingly challenged. Energy stars and the European Commission, among others, are concerned not only with the energy efficiency of electronic devices, including lighting, but also by their standby power consumption, which could be a significant source of energy consumption for a long time. Under smart lighting, this challenge becomes more tricky, as the power supply must remain "powered on" to search for signals from the controller, so it continues to absorb the current.

  At present, Energy Star regulations allow the standby power consumption of 0.5W, but the California Energy Commission (CEC) and other agencies are planning to reduce this number to 0.2W by 2019, which will further upgrade the challenge. With the lighting from the incandescent light to LED technology, dimming has changed.

  More complex pulse-width modulation (PWM) technology is gradually replacing simple resistors or triac dimming, which requires designers to adopt different methods. LEDs are a low voltage technology, which means they cannot be driven directly by the mains like incandescent bulbs, but require a power supply that provides constant voltage (CV) or constant current (CC) power according to the LED application.

  The power supply has a substantial impact on the overall performance and energy efficiency of the lighting solution, so it needs to be subject to rigorous scrutiny, at least as led itself. There are many different lighting solutions available on the market, ranging in power from several watts to hundreds of watts. Therefore, the drive power supply is designed in a variety of ways.

  At lower power levels (usually less than 10W), a single-stage transition topology is the most popular scenario.

  Since the application of multifunctional solid-state illumination is more and more extensive, as a result, LED and the associated power supply space is also squeezed less and less, which means that efficiency is critical, so that the production of residual heat can be minimized, and can be in small and usually airtight space to install and run the lighting scheme reliably. An important reason for the rapid development of LED lighting program is the decline of the LED itself price.

  As a result, installers and consumers not only want the LED power supply to achieve better performance in smaller spaces, but also expect similar price cuts (which means designers need to reduce the number of components and reduce overall BOM costs).

  Modern lighting Power Conversion mode Lighting within the 25w-100w range and applicable to offices, factories and residences is one of the fastest growing market segments, with the two-segment approach being the most common solution.

  In many applications, the flyback power Factor Corrector (PFC) is used and is equipped with a buck-DC converter. This method is especially suitable for the solution of dimming requirement.

  It can also easily turn off LEDs in standby mode and can simply control multiple led strings for more complex lighting solutions.

  Anson Semiconductor recently launched an integrated solution for this type of application that can use two IC products and a small number of external components to design high-performance lighting power.

  FL7740 is a single-segment CV primary-end-regulation (PSR) controller that can be adjusted for CV (±3%) with built-in dynamic functions (including fast response time), and can minimize the overshoot and lower flushes caused by line and load transients to less than 10% of the output voltage. The controller supports universal wide-range AC input for 80V ac to 382V AC, and is suitable for mains power applications anywhere in the world. It delivers up to 100W of power, while in standby mode power consumption is 0.15w--easily beyond all regulatory requirements.

  It also implements a "continuous boot" operation that is critical to intelligent lighting solutions. The built-in PFC level can reach "0.9" at full load, and THD "10%." In the case of half load, the optional PF optimizer is used, while the value of 0.9 pf remains unchanged.

  This ensures that input disturbances can be kept to a minimum level within a wider load range, allowing FL7740 to be widely used.

  This advanced controller includes a range of protection functions critical to the safe operation of the lighting system: overload protection, output diode short circuit protection, inductive resistance short-circuit/open circuit protection, and VDD and vs over voltage protection. The FL7760 Buck ("Buck") controller, which runs in continuous current mode (CCM), provides a secondary conversion.

  The device can operate in the range of 8V to 60V wide voltage input, and support wide analog and PWM dimming, and the power consumption is only 150μa. Importantly, FL7760 PWM dimming can cover the entire output range of 1-100%, although some operating conditions, due to the operating frequency of PWM, may appear undesirable strobe and audible noise. Analog dimming range is 5-100%, compared with the current 15-100%, this is a significant improvement of the existing technology.

  In general, analog dimming is favored because it does not have a PWM flaw, and FL7760 makes it the first viable option.

  One of the significant advantages of dimming that is below the analog threshold of 5% is that FL7760 can combine analog and PWM to provide a mix of dimming, seamless combination of these two ways to provide a full range of dimming function, without the existence of stroboscopic and audible noise problems.

  Like FL7740, FL7760 offers a variety of protection features, including thermal shutdown and overcurrent protection.


  LED lighting is increasingly popular with its low power consumption, versatility, and inherent compatibility with intelligent lighting schemes, so designers are increasingly demanding on performance, especially for low standby power and the ability to provide a wide range of dimming capabilities. The semiconductor devices such as the fl7740/fl7760 combination of semiconductors meet these performance challenges and provide a compact, low component number solution that delivers the most advanced lighting power solutions at a very competitive cost.