Key power supply and LED lighting application solutions

As people are becoming more and more environmentally conscious, energy conservation is not only a hot topic, but also a practical action project for important regulatory agencies and leading manufacturers in various countries. Looking around our work and living environment, the most commonly used, most common or most energy-saving electronic appliances naturally become the first targets of energy conservation actions, such as computers, flat-screen TVs, set-top boxes, power applications such as adapters/external power supplies, and light-emitting diode (LED) lighting. Important global regulatory agencies, such as the US "Energy Star", the US 80 PLUS, the European Energy Efficiency Code of Conduct (COC), the EU EuP, Japan Top Runner, the China National Institute of Standardization, etc., have released newer and more high-efficiency specifications for these key applications, allowing electronic products to perform the same functions with less electricity and improve the efficiency of electricity use.

Taking multi-output desktop ATX power supplies as an example, the 80 PLUS Silver and Computing Industry Climate Change Initiative (CSCI) Silver specifications have been in effect since July 2009, requiring multi-output desktop ATX power supplies to achieve 85%, 88% and 85% efficiency at 20%, 50% and 100% of rated output power, respectively. The subsequent 80 PLUS Gold and CSCI Gold specifications will take effect in July 2010, further raising the efficiency requirements to 87%, 90% and 87%.

Another example is the energy consumption of flat-panel TVs, which has become a growing concern in the industry as their sizes increase. The Energy Star 4.0 specification for TVs will take effect on May 1, 2010. This specification requires that the energy consumption of flat-panel TVs with visible screen diagonal sizes of 32 inches, 42 inches, and 60 inches in working mode shall not exceed 78 W, 115 W, and 210 W, respectively. The subsequent 5.0 specification, which will take effect on May 1, 2012, further requires that the working energy consumption of these sizes of flat-panel TVs shall not exceed 55 W, 81 W, and 108 W, as shown in Table 1. The European EuP directive has similar requirements. In addition to requiring a reduction in working energy consumption, these specifications also require a reduction in standby energy consumption, because data shows that a considerable amount of electricity is consumed in standby mode. Energy efficiency specifications such as Energy Star currently require standby energy consumption to be no more than 1 W, and in the future may require no more than 0.3 W or even no more than 0.1 W.

Table 1: Energy Star 4.0 and 5.0 TV specifications operating energy requirements

As for adapters/external power supplies widely used in notebook computers and other products, the Energy Star 2.0 specification has been in effect since November 1, 2008. Taking the Energy Star 2.0 external power supply specification as an example, this specification requires that the working efficiency of external power supplies with an output power greater than 49 W (typical products such as notebook adapters) be increased from 84% in version 1.1 to 87%, and the standby (no-load) energy consumption be reduced from no more than 750 mW to no more than 500 mW, and the power factor (PF) is also required to be no less than 0.9. The first and second phase requirements of the EU EuP Eco-design Directive 2005/32/EC Regulation No 278/2009 will take effect in April 2010 and April 2011 respectively. The first phase requires that the working efficiency of external power supplies with an output power greater than 51 W be no less than 85%, and the no-load energy consumption shall not exceed 500 mW. The no-load energy consumption requirement of the second phase remains unchanged, but the energy efficiency requirement is increased to 87%.

In addition to these applications, LED lighting or solid-state lighting (SSL) is also a hot application today. The 1.0 version of the "Energy Star" SSL specification has been in effect since October 1, 2008, requiring zero off-state energy consumption. The minimum energy efficiency requirements vary depending on the application (such as spotlights, outdoor lights, etc.). In terms of power factor requirements, commercial applications are not less than 0.9, and residential applications are not less than 0.7.

Power supply and LED lighting application design challenges

These critical power and LED lighting applications present challenges to design engineers, requiring increased energy efficiency density, improved power factor, and increased product reliability.

Specifically, due to overall energy efficiency requirements and thermal limitations, design engineers must strive to improve energy efficiency, even in low-power applications (or light loads). In addition, power factor correction (PFC) is not only required at higher power levels, but may also be required at relatively low powers. In addition, these applications often face space constraints, especially in applications where LED lighting replaces traditional bulbs. Overall reliability is also very important. The input power range is also wider, supporting 277 Vac voltage. In addition, there are some specific lighting requirements, such as triacs. Thyristor

Coping strategies

To meet the design challenges of these key power supplies and LED lighting applications, newer technologies or optimized power topologies and solutions are needed.

Taking flat-panel TV applications as an example, in order to maximize energy efficiency, the traditional cold cathode fluorescent lamp (CCFL) backlight can be replaced with an emerging LED backlight, such as direct backlight or edge-lit backlight, which not only helps slim TV design, but also helps reduce energy consumption and improve energy efficiency. If the current CCFL backlight with a higher cost-effectiveness is maintained, different effective measures can also be taken, such as reducing the number of lamps and reducing energy consumption under the condition of providing the same light output, or adopting a novel inverter driver solution, such as LCD TV integrated power supply (LIPS), to reduce a power conversion stage, improve energy efficiency and reduce costs.

ON Semiconductor supports high energy efficiency trend with leading products and solutions

As a premier supplier of high-performance, energy-efficient silicon solutions, ON Semiconductor provides power management and LED lighting solutions to save energy, helping customers meet and exceed power supply specifications around the world (working efficiency, standby energy consumption, low quiescent current and power factor correction, etc.) at a cost parity or lower than traditional solutions.

It is important to emphasize that ON Semiconductor takes a holistic approach to achieving high energy efficiency, including:

1) Reduce standby (no-load) energy consumption. This includes using better topologies such as quasi-resonance (valley switching), turning off the PFC stage in a two-stage converter, and using new technologies such as frequency foldback, cycle skipping, soft cycle skipping, and high-voltage bootstrap circuits.

2) Improve the energy efficiency of power supply, including using better devices, such as field effect transistors (FETs) and diodes, and using better topologies, such as frequency flyback, synchronous rectification, and soft switching technologies such as quasi-resonance, full resonance, and active clamping (flyback or forward).

3) Power factor correction (or harmonic reduction). This includes combining PFC with the main converter and optimizing the PFC control mode for the specified application and level, such as discontinuous conduction mode (DCM), critical conduction mode (CrM), or continuous conduction mode (CCM).

ON Semiconductor provides a wide range of leading products for these key power and LED lighting applications, such as PFC controllers, AC-DC controllers, high-voltage MOSFETs, LED drivers, rectifiers, secondary synchronous rectification controllers, DC-DC switching regulators and low-dropout (LDO) regulators. Based on these leading products, it provides energy-efficient GreenPoint? reference designs for ATX power supplies, notebook and printer power adapters, TVs, solid-state lighting and other applications.

Figure 1: ON Semiconductor’s 255W power supply reference design for ATX desktops with >85% efficiency

For example, ON Semiconductor's 255W GreenPoint? power supply reference design for desktop ATX power supply has an energy efficiency of more than 85% under conditions of 100, 115, 230 and 240 Vac input voltage and 25%, 50% and 100% rated output power, meeting 80 PLUS Silver energy efficiency specifications and Energy Star 5.0 desktop power supply specifications, and meeting IEC61000-3-2 power factor requirements, with a power factor higher than 0.95 under various input voltage conditions. It is worth mentioning that these data are obtained at the end of a 41-meter long cable, which has been fully tested, is strong and cost-effective, and is a production-ready design, see Figure 1.

For example, in general LED lighting applications, ON Semiconductor redesigned a halogen lamp purchased from a retail store using LED modules. The original 35 W halogen lamp had an input power of 41.7 W at 120 Vac and a brightness of 744 lumens, while the LED lamp based on the LED module built by ON Semiconductor NCP1014 had an input power of only 10.9 W at 120 Vac, which means that the energy consumption is only 1/4 of that of a traditional halogen lamp, but the light output is higher than that of a halogen lamp, reaching 795 lumens. This new desk lamp design using LED modules not only reduces the product size, but also achieves excellent energy saving. See Figure 2 for the circuit diagram of this LED module.

Figure 2: Circuit diagram of a desk lamp redesigned with an NCP1014-based LED module

ON Semiconductor aims to become the preferred supplier of high-quality, cost-effective, high-performance power management solutions. In addition to launching key control, drive and power conversion ICs, it also launches high-voltage MOSFET and rectifier products, and provides a rich rectifier packaging system, including the new SO-8 FL rectifier package, whose thermal performance is almost as good as the DPAK compact package.

Summarize:

Key power applications such as computers, flat-panel TVs, adapters, and LED lighting applications are facing higher energy efficiency requirements, which brings challenges to designers. ON Semiconductor currently has advanced technologies and products for building high-efficiency power and LED lighting applications, and is a complete solution provider, providing differentiated GreenPoint? reference designs with high performance and low total system cost, which not only improves working energy efficiency, but also reduces standby energy consumption, while also providing high power factor, helping customers meet or exceed high energy efficiency regulations around the world in an overall way.