High-efficiency energy-saving technology to meet stricter power efficiency regulations

　   As people's awareness of energy conservation and environmental protection continues to increase, more stringent energy efficiency regulations have emerged in the fields of computers, lighting, consumer electronics, power adapters and home appliances. Taking the US "Energy Star" project, which has a wide influence in the world, as an example, the new version 1.0 solid-state lighting (SSL) specification has been implemented since October 1, 2008, the version 2.0 adapter/external power supply specification and the version 3.0 TV specification have also been implemented on November 1 of the same year, and the version 2.0 set-top box (STB) specification has also taken effect on January 1, 2009.

　　These energy efficiency specifications have higher requirements than previous versions in terms of working energy efficiency, standby energy consumption and power factor. For example, the working energy efficiency requirement of the 2.0 version adapter specification (taking an output power greater than 49 W as an example) is no less than 87%, while the previous 1.1 version required no less than 84%. In addition, the standby energy consumption requirement of the 3.0 version TV specification is no more than 1 W, and subsequent specifications may further reduce it to no more than 0.3 W or even 0.1 W.

　　These more stringent energy efficiency regulations have brought more difficult energy-saving challenges to power designers. As a leading global supplier of high-performance, high-efficiency silicon solutions, ON Semiconductor has a unique advantage in responding to more stringent power efficiency regulations with efficient energy-saving technologies, providing high-efficiency overall power solutions that can help designers simultaneously reduce power standby energy consumption, improve working energy efficiency, and apply power factor correction (PFC).

　　Optimize PFC control mode and combine PFC with main converter

　　Energy efficiency specifications for many applications, including computer power supplies and external adapters, include power factor requirements, such as mandatory PFC for personal computers, TVs, and monitors with power greater than 75 W. An important part of ON Semiconductor's overall solution is to combine PFC with the main converter and optimize the PFC control mode for the specified application and power level.

　　Depending on the current characteristics, common PFC operating modes include discontinuous conduction mode (DCM), critical conduction mode (CrM), continuous conduction mode (CCM) and frequency clamped critical conduction mode (FCCrM), and their characteristics are also different.

　　ON Semiconductor offers a wide range of PFC controllers, such as NCP1601/5/6/7/8, NCP1631, NCP1650/1/2/3/4, etc., covering the above different working modes and optimized for applications with different powers, see Table 1. For example, NCP1606/7/8 adopts CrM working mode, which is suitable for medium-power applications with power usually below 300 W, such as electronic ballasts, LCD TVs, plasma TVs, desktop computers and AC adapters. The newly launched NCP1654 works in CCM mode and is suitable for occasions with power greater than 200 W. The predecessor of NCP1654, NCP1653, has achieved great success in the past few years and is widely used in desktop computers, open power supplies and other fields. Especially in LCD TVs and plasma TVs, it occupies the vast majority of the market share.

Table 1: ON Semiconductor PFC controllers for different output power levels and applications.

　　与此同时，安森美半导体还开发了较新的PFC架构，如将PFC段与脉宽调制(PWM)主转换器段结合在一起，推出单段式的PFC控制器。实际上，NCP1651及NCP1652就是这种架构的典型产品。这种单段式PFC减少控制IC、电感和MOSFET的使用数量，帮助提升能效及显著降低成本。NCP1652单级PFC采用反激式拓扑结构，既可以工作在CCM，也可以工作在DCM，结构简单且成本优势明显，特别适合于25 W至150 W功率范围的应用，包括大电流电池充电器、分布式电源系统前端和大功率固态照明(SSL) 等。采用CCM工作模式时，NCP1652帮助提供极优的功率因数，同时限制峰值初级电流。

　　ON Semiconductor is also actively developing novel PFC control technologies such as interleaved PFC and a single-chip interleaved PFC controller in FCCrM mode, the NCP1631. This interleaved PFC is easier to design, facilitates the use of modular solutions, and simplifies electromagnetic interference (EMI) filtering. In particular, the design using two smaller PFCs can support ultra-thin LCD TV designs with a thickness as low as 10 mm, providing excellent energy efficiency in the full power range, as shown in Figure 1.

　　Use better devices and topologies to improve power efficiency

　　In addition to its efforts in PFC, ON Semiconductor also uses topologies such as frequency flyback, synchronous rectification, and soft switching (including quasi-resonance, full resonance, and active clamping (flyback or forward)) in switch controllers, while using good field-effect transistors (FETs) and diodes to improve the efficiency of power supply solutions.

　　Among them, as for AC-DC offline switching power supply controllers, ON Semiconductor provides a variety of options with and without high-voltage startup circuits, such as NCP1237/8, NCP1287/8, NCP1379, NCP1380, NCP1252, NCP1351, NCP1395/6/7, etc. Taking NCP1379/80 as an example, these two devices are high-performance quasi-resonant (QR) controllers with valley lock function, support valley conversion, provide excellent working efficiency under a wide range of conditions (see Table 2a), and significantly reduce noise, suitable for use in notebooks, LCD monitors and game consoles AC-DC adapters, auxiliary power supplies for flat-panel TVs, and consumer applications such as DVDs and set-top boxes.

Table 2: The NCP1379/80 controllers offer high operating efficiency and low light load and standby energy consumption.

　　In addition to the main switch controller, ON Semiconductor plans to launch a series of new high-voltage power MOSFETs to improve power solutions, such as NDFxxN60Z. These MOSFETs use advanced packaging technologies, including the DPAK surface mount (SMT) package and TO220FP, TO-220 perforated packages launched in 2009, as well as D2PAK, SOT-223 and other surface mount packages, and I2PAK, TO-30, IPAK and TO-92 perforated packages launched in 2010. In addition, ON Semiconductor also has a wealth of rectifier products, which cover power supply markets such as adapters, ATX power supplies, and LCD TV power supplies, as well as automotive markets such as power systems, safety and control, comfort and convenience, and body electronics.

       Research on new green energy-saving technologies

　　As a world-leading supplier of high-performance, high-efficiency silicon solutions, ON Semiconductor not only helps customers build high-efficiency overall power solutions with existing products and technologies, but also continues to promote research on new green energy-saving technologies to help meet the higher requirements of subsequent energy efficiency regulations and higher expectations of customers.

　　For example, in terms of improving PFC energy efficiency, in addition to novel technologies such as interleaved PFC, ON Semiconductor has also studied bridgeless PFC solutions. This PFC architecture aims to remove the diode rectifier bridge, reduce power loss during rectification, and greatly improve PFC energy efficiency. ON Semiconductor has developed a prototype of an 800 W PFC segment based on this architecture. This prototype uses the NCP1653 PFC controller and the MC33152 MOSFET driver. After testing, the prototype has an energy efficiency of 94% under 90 Vrms, full load, and no fan (chassis open, room temperature), and 95% at 100 Vrms. At 20% load, the energy efficiency is closer to or exceeds 96%. This bridgeless PFC architecture will be an extremely energy-efficient solution for high-power applications.

                 Figure 2: Schematic diagram of the new interleaved LLC topology for improving PWM energy efficiency.

　　Secondly, in terms of improving the PWM energy efficiency of the main converter, in addition to continuing to develop soft switching topologies such as active clamp forward (ACF) and half-bridge resonance (LLC), ON Semiconductor is also developing a new interleaved LLC (ILLC) topology for higher power applications. When large output current (such as greater than 15 A) and/or low thickness design are required, ILLC can be used to provide extremely high energy efficiency and greatly reduce the secondary capacitor ripple current. It is possible to build an ILLC control unit based on the NCP1395/6 controller, add division logic and two half-bridge drivers NCP5106. The evaluation board test results show that this topology can maintain an extremely high energy efficiency of more than 95% when phase 2 is lightly loaded and turned off. ON Semiconductor is also actively developing new secondary synchronous rectification technologies, such as the NCP4303A/B universal synchronous rectification controller, which has externally adjustable minimum on and off time characteristics, optimizes the use of switching cycles, and provides high energy efficiency.

　　Energy-efficient reference design accelerates the time-to-market for “green” power supplies

　　In order to help customers shorten the development cycle and speed up product launch, ON Semiconductor has also launched a variety of GreenPoint® power supply reference designs, such as the extremely energy-efficient 255W computer ATX power supply reference design, the 220W high-voltage LIPS LCD TV power supply reference design, etc. The documents provided in these public reference designs include functional block diagrams and full schematics, bill of materials (BOM), circuit board layout diagrams, design descriptions, performance test results, and performance verification from third-party tests.

　　Summarize:

　　More and more stringent power efficiency standards have emerged in the fields of computing, consumption, lighting and adapters, bringing important challenges to designers. As a leading global supplier of high-performance and energy-efficient silicon solutions, ON Semiconductor continues to launch a variety of novel key control devices, MOSFETs and rectifier products, while continuing to conduct research on green energy-saving technologies to help customers improve power factor, improve working energy efficiency and reduce standby energy consumption in an overall way, and provide highly efficient GreenPoint® power reference designs that have been tested and proven to have extremely high energy efficiency and meet the requirements of 80 PLUS and "Energy Star" regulations, helping customers shorten the design cycle and accelerate the process of listing products.