The latest designs and solutions for power supply and LED lighting applications

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 effective 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.
Challenges in power supply and LED lighting application design.

These key power supply and LED lighting applications bring challenges to design engineers, requiring both increased energy efficiency density and improved power factor, as well as increased product reliability.

Specifically, due to total energy efficiency requirements and heat dissipation 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 power levels. 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 triac dimming . 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 emerging LED backlights , such as direct backlight or edge backlight, which not only helps slim TV design, but also helps reduce energy consumption and improve energy efficiency. If the current CCFL backlight, which still has 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 novel inverter driver solutions, such as LCD TV integrated power supply (LIPS), to reduce one power conversion stage, improve energy efficiency and reduce costs. ON Semiconductor supports the energy-efficient trend with leading products and solutions. As the leading supplier of high-performance and 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.), with cost parity or lower than traditional solutions. It should be emphasized that ON Semiconductor adopts a holistic approach to achieve high energy efficiency, including: 1) Reducing standby (no-load) energy consumption. Including the use of better topologies such as quasi-resonance (valley switching), turning off the PFC stage in a 2-stage converter, and adopting new technologies such as frequency foldback, skipping, soft skipping and high-voltage bootstrap circuits. 2) Improving the working efficiency of power supplies. Including the use of better devices such as field effect transistors (FETs) and diodes, and the use of better topologies such as frequency foldback, 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 255 W power supply reference design for ATX desktops with over 85% efficiency

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

For another example, in general LED lighting applications, ON Semiconductor redesigned a halogen desk lamp purchased from a retail store using LED modules . The input power of the original 35 W halogen lamp at 120 Vac is 41.7 W, and the brightness is 744 lumens . The input power of the LED desk lamp based on the LED module built by ON Semiconductor NCP1014 at 120 Vac is only 10.9 W, that is, the energy consumption is only 1/4 of the traditional halogen lamp, but the light output is higher than the 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. The circuit diagram of this LED module is shown in Figure 2.

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.

Summary:

Critical 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.