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常见问题 - Energy

低效线性电源为何依然存在？

尽管有体积大、功率转换效率低等缺点，线性电源却依然普遍存在，这是因为它们的制造成本非常低廉。此前不久，5 W以下的开关电源在成本上尚无竞争优势，且由于产品制造商不需为电费买单，因此对他们而言，考虑将节能纳入产品设计之首也就没有丝毫动力。只是近几年，政府和环保机构才开始制定待机能耗政策，奖励或在某些情况下强制执行节能设计。

为什么待机功率损耗是一个需要解决的问题？

虽然单个设备的待机损耗可能看起来微不足道，但是如果您将住宅数量与住宅中的家电数量及每台家电的待机时间相乘时，问题很快会凸显出来。据国际能源机构估计，全球5% - 15%的家用电器耗电量是在待机模式下产生的。在美国，每瓦电能的成本大约是每年1到1.5美元。美国劳伦斯伯克力国家实验室(Lawrence Berkeley National Lab)估计，在美国家庭一年的电费中，待机功耗费用会超过50亿。根据美国能源部的报告，美国每年使用的待机电能相当于26座平均规模的电站的发电量！

随着家用电器的普及以及带有电子控制和多种功能的新设备的增加，这一问题也将会日益突出。

哪些设备使用待机功率？

所有带有外接电源或墙上电源供应器、遥控器或时钟显示的设备均消耗待机功率。严格来说，包括所有需要插接到墙壁插座上的电子产品，比如电视机、VCR、DVD、洗衣机、手机充电器、照明灯、无绳电话和功能手机、冰箱、有线电视解码器、卫星电视解码器、收音机、计算机、打印机、显示器、传真机、复印机、调制解调器、音频放大器、工业控制装置以及电机控制装置等等。据估计，全球每年交流到直流的供电量大约为30到40亿瓦。美国劳伦斯伯克力实验室待机功率(Lawrence Berkeley Lab Standby Power)网站提供有一张设备待机功耗状况图表。

当今线性电源技术的弊端是什么？

因其耗能特性而被我们称之为“能源吸血鬼”的线性电源，使用了与当前创新已格格不入的十九世纪初的老旧技术。线性变压器需要使用大块的铁芯以及大量圈数的铜线，才能将常规的50/60个周期的家用交流电压转换成为我们的家用电器和电子设备供电的较为安全的直流低电压。结果是，它们的体积变得异常庞大，时常要占用墙式插座板或插线板上两个插座的位置。而且，线性电源不具备智能元件，因此无法识别设备处于待机模式或睡眠模式，从而无法减少损耗。结果它们消耗的功率远远超过了实际所需的瓦数。您可以测试一下，去触摸墙壁插座上其中一个插接的大体积线性电源。摸起来很热…这正是浪费的功率！

EcoSmart的功率范围有哪些？

如今，Power Integrations使用EcoSmart技术的产品涵盖超过90%的全球所有AC-DC电源的功率范围：

器件系列	输出功率范围(W)
LinkSwitch-II LinkSwitch-XT LinkSwitch-LP LinkSwitch-TN	0 W - 5.5 W
TinySwitch-III	5 W - 28 W
PeakSwitch	9 W - 45 W（峰值功率为86 W）
TOPSwitch-GX	7 W - 210 W
TOPSwitch-HX	11 W - 150 W

什么是待机功耗？

当VCR、DVD以及手机充电器等电器设备插接在墙壁插座中时，即使这些产品处于闲置状态，仍然在消耗电能。消费者通常会认为他们的设备已经关机，而事实上，其设备只是处于待机状态，仍然在消耗着功率。

譬如，当您使用遥控器关闭VCR后，由于VCR内部的电源仍然处于接通状态并为遥控接收器供电，因此VCR仍在待机或睡眠模式下消耗着电能。尽管遥控接收器消耗的功率微乎其微（大约0.1 W），但由于采用低效技术的电源（如线性电源）不够智能，无法减少待机状态下的功率消耗，结果往往会浪费几瓦的功率。这就是我们所说的待机功耗。

什么是空载功耗？

空载功耗是待机功耗的一个子类。空载功率是指设备在与负载断开且不执行任何功能时所使用的电能。例如，插接在墙壁插座上的手机充电器，虽然未与手机相连，但仍会消耗功率。线性充电器即使在与手机断开连接时，仍可消耗0.8 W到2 W的功率。

EcoSmart的工作原理是什么？

在采用Power Integrations的EcoSmart技术设计的IC中，芯片上集成有额外的电路（使用无额外成本的外部元件），该电路可以检测到电源处于低功率状态（空载或待机）。EcoSmart“智能”元件随后会采取一个或多个步骤，以提高电源在此状态下的效率：

它会降低“占空比”，即限制对负载的供电，这样市电可以输出更少的电流
它会“周期跳频”，向负载突发短暂供电，等待设备“醒来”，因而只在每一短暂的时间内使用电能
它会降低电源的工作频率，减小“开关损耗”，从而在低功率条件下提高效率

上述措施之所以能够显著提高整体电源效率，主要是基于以下两个简单的事实：电源适配器、电池充电器及电器始终接入电源，并且它们供电的设备通常每天22小时或更长时间都处于低功率状态。自EcoSmart技术面世后，全球各制造商已将Power Integrations的IC产品应用到了超过十亿的电源产品设计中。

如何降低待机功耗？

多达90%的待机功耗是由低效电源设计和不必通电的元件造成的。美国劳伦斯伯克力国家实验室(Lawrence Berkeley National Lab)估计，如果采用新设备，可能会减少75%的待机功耗，而且可以利用待机总功耗为1瓦甚至更低的设备执行几乎所有的待机功能。要达到此目的，可以采用改进的电源技术和设计，也即，使用更为智能的开关电源代替低效的线性电源。

开关电源的优势何在？

第二代电源，我们称之为开关电源或简称“开关”，出现于二十世纪六十年代晚期。工程师们发现，他们可以通过将交流频率从每秒50或60个周期提高到每秒数千个周期，以此来缩小变压器的体积和重量，并可显著提高变压器的效率（降低散热形式的能源浪费量）。

是否存在既有成本效益又具节能优势的替代电源？

1998年，Power Integrations推出了一种革命性的节能电源技术-“EcoSmart®”。利用EcoSmart技术设计的开关电源能够在待机或空载条件下以更高的效率进行工作。而且，EcoSmart采用了革新的集成电路(IC)技术，最终使得使用5 W以下的线性变压器的开关设计变得具有成本优势。通过集成，电源不再需要任何外部元件，这样不仅能降低系统成本，还可以极大地提高可靠性。

What is standby power waste?

When appliances such as VCRs, DVDs and cell phone chargers are plugged into the wall, they consume energy even when the product is not in use. Consumers often believe that their appliance is off, when in fact it is standing by and still consuming power.

For example, when you turn off a VCR with a remote control, it continues to consume energy in the standby or sleep mode because the power supply inside the VCR is still on, powering the remote control receiver. Even though the remote control receiver consumes very little power (approximately 0.1 W), power supplies that use inefficient technology such as linears, are not smart enough to reduce consumption during the standby state and end up wasting several watts of power. This is what we refer to as standby power waste.

What is no-load power waste?

No-load power waste is a subset of standby power waste. No-load power is the energy used by a device when it is disconnected from it's load and performing no function. For example, a mobile phone charger that is plugged into the wall, but not connected to the phone will still consume power. Linear chargers can consume between 0.8 W to 2 W even when they are disconnected from the phone.

Which devices use standby power?

Any device with an external power supply or (wallpack), remote control, or clock display requires standby power. Literally every electronic product that plugs into the wall such as TVs, VCRs, DVDs, washing machines, cell phone chargers, night lights, cordless and feature phones, refrigerators, cable TV decoders, satellite TV decoders, radios, computers, printers, monitors, fax machines, copiers, modems, audio amplifiers, industrial control units, motor controls, etc. etc. It is estimated that there are approximately 3 to 4 billion AC to DC power supplies world wide every year. The Lawrence Berkeley Lab Standby Power website has a chart on Standby Power Use By Device.

Why are standby power losses a problem?

While individual device standby losses may seem insignificant, when you multiply the number of households, by the number of devices in a household and the amount of time each spends in standby, the problem adds up quickly. It is estimated by International Energy Agency that 5 to 15% of household electricity consumption worldwide is wasted in standby mode. In the US, each watt of energy costs approximately $1 to $1.5 per year. The Lawrence Berkeley National Lab estimates that standby waste costs US households over $5 Billion in electricity a year. According to the Department of Energy, the amount of standby energy used per year in the US is equivalent to 26 average sized power stations!

As the popularity of home electronics and number of new appliances with electronic controls and features increase, this problem will continue to grow.

How can standby power consumption be reduced?

Up to 90% of standby power is wasted energy consumed by inefficient power supply designs and unnecessarily energized components. The Lawrence Berkeley National Lab estimates that a 75% reduction is possible in new equipment and that nearly all standby functions can be performed with a total appliance standby power of one watt or less. This can be achieved by using improved power supply technologies and designs, namely, by replacing inefficient linear power supplies with smarter switch-mode power supplies.

What’s wrong with the current technology -- linear power supplies?

Linear power supplies, also referred to as "energy vampires" because of their energy-sucking nature, work off of old technology from the 1800's, which hasn't kept pace with current innovation. Linear transformers use large iron cores and require many turns of copper wire in order to convert regular 50/60 cycle AC house current to the safer low-voltage DC needed to power our appliances and electronic devices. As a result, they are extremely large and bulky, often times covering two outlets on your wall plate or power strip. Moreover, linears do not have the smarts to recognize the standby or sleep mode of the appliance and cut back the consumption accordingly. As a result they consume many more watts than necessary. As a test, go feel one of the bulky linears plugged into the wall. It will be warm to the touch...those are wasted watts!

How are switch-mode power supplies better?

The second-generation power supply, called the switch-mode power supply or "switcher" for short, arrived in the late 1960s. By increasing the AC frequency from 50 or 60 cycles-per-second to several thousand cycles-per-second, engineers discovered they could reduce the size and weight of the transformer and significantly improve its efficiency (reduce the amount of energy wasted in the form of heat dissipation).

Why do inefficient linears still exist?

Despite being bulky and inefficient at converting power, linears are popular because they have become very cheap to manufacture. Until recently, under 5 W switch-mode power supplies haven't been competitive in cost and since product manufacturers don't have to pay the electric bill, there hasn't been an incentive to prioritize energy efficient designs. It's only been in recent years that governments and environmental agencies have started to develop standby energy policies that reward, or in some cases, mandate energy efficient designs.

Are there cost-competitive AND energy efficient power supply alternatives?

In 1998, Power Integrations introduced a revolutionary energy efficient power supply technology called, "EcoSmart®". EcoSmart enables a switch-mode power supply design to operate with much higher efficiency when in standby or when the load is not connected. Moreover, by using innovative integrated circuit (IC) technology, it finally allowed switcher designs to be cost-competitive with the linear transformer under 5 W. Through integration, external components are eliminated, lowering system cost and improving reliability considerably.

How does EcoSmart work?

ICs with Power Integrations' EcoSmart technology include extra circuitry on the chip (using no additional-cost external components) that senses when a power supply is in a low-power state (no-load or standby). The "smarts" in EcoSmart then takes one or more steps to improve the efficiency of the power supply in this state:

It lowers the "duty cycle", that is it limits the supply of power to the load, drawing less current from the electric utility
It "cycle skips", supplying short bursts of power to the load, waiting for the device to "wake-up," using electric energy only during each short burst
It lowers the frequency of the power supply, reducing the "switching losses," thus improving efficiency while in low-power operation

The above measures significantly improve the overall power supply efficiency because of two simple facts: power adapters, battery chargers and appliances are always plugged in; and the devices they power are typically in a low power state as much as 22 or more hours per day, every day. Since its introduction, manufacturers worldwide have adapted their designs to use Power Integrations' ICs in over one billion power supplies.

What power ranges are covered by EcoSmart?

Currently, Power Integrations produces EcoSmart products that cover the power range of over 90% of all AC to DC power supplies built worldwide using the following device families:

Device Family	Ouput Power Range (W)
LinkSwitch-II LinkSwitch-XT LinkSwitch-LP LinkSwitch-TN	0 to 5.5
TinySwitch-III	5 to 28
PeakSwitch	9 to 45 (86 W Peak)
TOPSwitch-GX	7 to 210
TOPSwitch-HX	11 to 150