无线设备的大问题

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智能手机和平板电脑等无线设备正成为大多数人的生命线。
确保这条生命线在需要时具有动力是一个主要问题。
因此，系统设计人员会考虑各个方面，以最大限度地降
为了帮助实现每个器件的重要性，我们将在升压转换器中查看用于LED背光的肖特基二极管。
在该应用中，电池的电压被升高到以每串20mA驱动LED所需的电压用于背光。
此应用中使用的功率在很大程度上取决于LED的配置。
通常，该LED配置是两串六个LED。
其他重要参数是电感和开关频率。
为了最小化该解决方案的总板面积，理想的是使用高频率，这将允许使用更小的电感器。
出于我们的目的，我们将使用1.2 MHz的开关频率和4.7μH电感。
对于二极管选择，我们将比较两种用于此应用的流行肖特基二极管，NSR0340P2和NSR05F40NX。
NSR0340P2是一款采用SOD-923封装的低VF肖特基二极管。
NSR05F40NX是DSN2肖特基二极管，其尺寸与SOD-923相同。
根据所述设置，NSR0340P2的功率损耗为26.1 mW，而NSR05F40NX的功耗仅为17.0 mW。
将其与总系统输出功率768 mW进行比较。
我们假设系统的其余部分具有90％的效率。
考虑到这一点，使用NSR0340P2的整个系统的效率为87％，而使用NSR05F40NX的效率为88％。
通过简单地使用更优化的肖特基二极管，这可以提高1％的效率。
现在让我们来看看最终用户关心的东西，电池寿命。
我们将使用容量为7 Wh的电池来确定电池寿命。
如果此应用是唯一使用电源的应用，则NSR0340P2的电池寿命为476分钟。
NSR05F40NX的电池寿命为481.5分钟。
这导致电池寿命增加5.5分钟。
不可否认，从最终用户的角度来看，5.5分钟可能并不太明显。
然而，通过简单地改变LCD背光系统中的一个肖特基二极管来节省这些5.5分钟。
如果将此练习带到位于电源应用中的其他设备，这些1％的节省可能会延长30分钟，一小时甚至两个小时的延长电池寿命。
独立1％的节省可能不是什么大不了的事，但累计这些孤立的1％增加是一个大问题。

以上来自于谷歌翻译

以下为原文

Wireless devices such as smartphones and tablets are becoming the lifeline for most people.  Ensuring that this lifeline has power when needed is a major concern.  System designers therefore look at every aspect to minimize power loss.  To help realize that every device matters, we will look at the Schottky diode in the boost converter for the LED backlight.

In this application the voltage of the battery is boosted to the voltage needed to drive the LEDs at 20 mA per string for the backlight.  The power used in this application depends heavily on the configuration of the LEDs.  Typically this LED configuration is two strings of six LEDs.  Other important parameters are the inductor and the switching frequency.  To minimize the total board area of this solution it is ideal to use a high frequency which will allow a smaller inductor to be used.  For our purpose we will use a switching frequency of 1.2 MHz and a 4.7 µH inductor.
For the diode selection we will compare two popular Schottky diodes used for this application, NSR0340P2 and NSR05F40NX.  The NSR0340P2 is a low VF Schottky diode housed in a SOD-923 package.  The NSR05F40NX is a DSN2 Schottky diode that is the equivalent size of the SOD-923 package.  With the setup described the resulting power loss of the NSR0340P2 is 26.1 mW while the NSR05F40NX only dissipates 17.0 mW.  This is compared to a total system output power of 768 mW.  We will assume that the rest of the system has an efficiency of 90%.  With this taken into account the overall system with the NSR0340P2 will have an efficiency of 87% compared to 88% when the NSR05F40NX is used.  This is a one percent efficiency increase by simply using a more optimized Schottky diode.
Now let’s look at something that the end user cares about, battery lifetime.  We will use a battery with a 7 Wh capacity to determine the battery lifetime.  If this application is the only thing that uses power the battery lifetime would be 476 minutes for the NSR0340P2. The NSR05F40NX would provide a battery lifetime of 481.5 minutes.  This results in a 5.5 minute increase in the battery lifetime.

Admittedly 5.5 minutes may not be too noticeable from the end users perspective.  However, these 5.5 minutes were saved by simply changing one Schottky diode in the LCD backlight system.  If this exercise was carried to other devices located in power applications these 1% savings may add up to 30 minutes, an hour or even possibly two hours of extended battery lifetime.  Independently 1% savings may not be a big deal, but cumulatively these isolated 1% increases are a big deal.

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