Sunday, September 30, 2012

Power Supply Programming Examples

Hello everyone!

One of my responsibilities at Agilent is to oversee programming example generation for our new product introductions.  Programming examples are an area that we wish to improve upon.  Our goal is to provide a selection of programming examples that allow our customers to use the exciting new features of our products at introduction.

The first thing that we want to do is to make sure that we provide examples that our customers can use so I researched the most popular programming languages that customers use with power supplies.  The list that we came up with is: VB.NET, Labview, C#, and in some cases Matlab.  In terms of IO Libraries, we will use direct IO for everything.  We will not be including any driver examples in this plan.  We will also be providing a text file with the SCPI programs and an Agilent Command Expert sequence file.
I would like to solicit some feedback on this plan.  What do you think?  Can we improve this plan?  Are any programming languages missing? What do you look for in a programming example?  

 Please leave comments.

Wednesday, September 26, 2012

Battery-killing cell phone apps? – Part 2

Back on May 25, 2012, I posted about mobile device users avoiding security apps because they think the apps run down their batteries too quickly (read that post here). I also mentioned that a member of the Anti-Malware Testing Standards Organization (AMTSO) is using Agilent’s N6705B DC Power Analyzer to evaluate just how much the security apps affect battery run time and that the results would not be available for a few months. Well, the results are in and guess what? Which security app you choose does not make much difference in your battery run time.

On average, they reported that the effect of using a security app on reducing battery run time is only about 2% which translates into less than 30 minutes of lost battery life per day. And the study went on to explain that the differences in performance of one mobile security product to another were small (they tested 13 products each from a different vendor). I was amused by the author’s comment that they were “not providing a ranking” because it “could get misused by marketing departments”. Indeed!

Here is a link to the report:

The report shows a picture of Agilent’s N6705B DC Power Analyzer as the measuring device. They used this product because “This high-precision instrument can measure battery drain exactly”. A screen shot of Agilent’s 14585A Control and Analysis Software for the DC Power Analyzer was also shown in the report. The software allowed them to evaluate power consumption while performing various mobile phone tasks, such as making phone calls, viewing pictures, browsing websites, watching YouTube (I wonder if they watched any of the DC Power Analyzer videos we have posted!), watching locally stored videos, receiving and sending mails, and opening documents.

If the N6705B DC Power Analyzer and 14585A Control and Analysis Software can evaluate power consumption for all of those things, just think of what it could do for you! Check out Ed’s post from earlier this week for some of those things:

Monday, September 24, 2012

Optimizing Mobile Device Battery Run-time Seminars

On many occasions in the past here both I, and my colleague, Gary, have written about measuring, evaluating, and optimizing battery life of mobile wireless battery powered devices. There is no question that, as all kinds of new and innovative capabilities and devices are introduced; battery life continues to become an even greater challenge.

I recently gave a two-part webcast entitled “Optimize Wireless Device Battery Run-time”. In the first part “Innovative Measurements for Greater Insights” a variety of measurement techniques are employed on a number of different wireless devices to illustrate the nature of how these devices operate and draw power from their batteries over time, and in turn how to go about making and analyzing the measurements to improve the device’s battery run-time. Some key points brought out in this first part include:
  • Mobile devices operate in short bursts of activities to conserve power. The resulting current drain is pulsed, spanning a wide dynamic range. This can be challenging for a lot of traditional equipment to accurately measure.
  • Not only is a high level of dynamic range of measurement needed for amplitude, but it is also needed on the time axis as well, for gaining deeper insights on optimizing a device’s battery run-time.
  • Over long periods of time a wireless device’s activity tends to be random in nature. Displaying and analyzing long term current drain in distribution plots can quickly and concisely display and quantify currents relating to specific activities and sub-circuits that would otherwise be difficult to directly observe in a data log.
  • The battery’s characteristics influence the current and power drawn by the device. When powering the device by other than its battery, it can be a significant source of error in testing if it does not provide results like that of when using the battery.

Going beyond evaluating and optimizing the way the device makes efficient use of its battery power, the second part, “The Battery, its End Use, and Its Management” brings out the importance of, and how to go about making certain you are getting the most of the limited amount of battery power you have available to you. Some key points for this second part include:
  • Validating the battery’s stated capacity is a crucial first step both for being certain you are getting what is expected from the battery and serve as a starting reference point that you can correlate back to the manufacturer’s data.
  • Evaluating the battery under actual end-use conditions is important as the dynamic loading a wireless device places on the battery often adversely affects the capacity obtained from the battery.
  • Charging, for rechargeable batteries, must be carefully performed under stated conditions in order to be certain of in turn getting the correct amount of capacity back out of the battery. Even very small differences in charging conditions can lead to significant differences in charge delivered during the discharge of the battery.
  • The wireless device’s battery management system (or BMS) needs to be validated for proper charging of the battery as well as suitability for addressing the particular performance needs of the device.

In Figure 1 the actual charging regiment was captured on a mobile phone battery being charged by its BMS. There turned out to be a number of notable differences in comparison to when the battery was charged using a standard charging regiment.

Figure 1: Validating BMS charge regiment on a GSM/GPRS mobile phone

If you are interested in learning more about optimizing wireless device battery run-time this two part seminar is now available on-demand at:

I think you will enjoy them!

Wednesday, September 5, 2012

Early Power Transistor Evolution, Part 2, Silicon

As discussed in part 1 of this two-part posting on early power transistor evolution, by the early 1960’s germanium power transistors were in widespread use in DC power supplies, audio amplifiers, and other relatively low frequency power applications. Although fairly expensive at that time the manufacturers had processes establish to reliably produce them in volume. To learn more about early germanium power transistors click here to review part 1.

As with most all things manufacturers continued to investigate ways of making things better, faster, and cheaper. Transistors were still relatively new and ready for further innovation. Next to germanium silicon was the other semiconductor in widespread use and with new and different processes developed for transistor manufacturing, silicon quickly displaced germanium as the semiconductor of choice for power transistors. One real workhorse of a power transistor that has truly stood the “Test of Time” is the 2N3055, pictured in Figure 1. Also pictured is his smaller brother, the 2N3054.

Figure 1: 2N3055 and 2N3054 power transistors

Following are some key maximum ratings on the 2N3055 power transistor:
  • VCEO = 60V
  • VCBO = 100V
  • VEBO= 7V
  • IC = 15A
  • PD = 115W
  • hfe= 45 typical
  • fT = 1.5 MHz
  • Thermal resistance = 1.5 oC/W
  • TJ= 200 oC
  • Package: TO-3 (now TO-204AA)
  • Polarity: NPN
  • Material/process: Silicon diffused junction hometaxial-base structure

Diffused junction silicon transistors made major inroads in the early 1960’s ultimately making the germanium power transistors obsolete.  One huge improvement using silicon, especially for power transistors, is the junction temperature, which is generally rated for 200 oC.  This allowed operating at much higher ambient temperatures and at higher power levels when compared to germanium. 

While the alloy junction process being used for the early germanium transistors favored making PNP transistors, the diffused junction process on silicon favored making NPN transistors somewhat more. Silicon diffused junction NPN transistors are much more prevalent than PNP devices, and the PNP complements to NPN devices, where available, are more costly.  

The diffusion process made a giant leap in transistor mass production possible. Many transistors could now be made at once on a larger silicon wafer, greatly reducing the cost. The more precise nature of the diffusion junction over the alloy junction also improved performance. As one example, tor the 2N3055 the transition frequency increased roughly another order of magnitude over the 2N1532 germanium alloy junction transistor in part 1, to 1.5 MHz.  

The hometaxial-base structure is a single simultaneous diffusion into both sides of a homogenously-doped base wafer, one side forming the collector and the other side the emitter. A pattern on the emitter side is etched away around the emitter, down to the P-type layer, to form the base. The emitter is left standing as a plateau or “mesa” above the base.

The 2N3054 was electrically identical to the 2N3055 except for its lower current and power capabilities. It’s smaller TO-66 package however was never very popular and was quietly phase out in the early 1980’s, sometimes along with some of the devices that were packaged in it!

Process improvements beyond the single diffused hometaxial-base structure continued through the 1960s with silicon transistors, including double diffused, double- and triple diffused planar and epitaxial structures. The epitaxial structure is a departure from the diffused structures in that features are grown onto the top of the base wafer. With greater control of doping levels and gradients, and more precise and complex geometries, the performance silicon power transistors continued to improve in most all aspects.

Plastic-packaged power transistors have for the most part come to displace hermetic metal packages like the TO-3 (TO-204AA), first due to the lower cost of the part and second, with simpler mounting, reducing the cost and labor of the products they are incorporated into. One drawback of most of the plastic-packaged power devices is their maximum temperature rating has been reduced to typically 150 oC, taking back quite a bit of temperature headroom provided by the same devices in hermetic metal packages. Sometimes there is a price to be paid for progress! Pictured in figure 2 are two (of many) popular power device packages, the smaller TO-220AB and the larger TO-247.

Figure 2: TO-220AB and TO-247 power device plastic packages

It’s pretty fascinating to see how transistors and the various processes used to manufacture them evolved over time. In these two posts I’ve hardly scratched the surface of the world of power transistors and power devices. For one there is a variety of other transistor types not touched upon, including a variety of power FETs. Power FETs have made major inroads in all kinds of applications in power supplies. Also work continues to provide higher power devices in surface mount packages. These are just a couple of numerous examples, possibly something to write about at a future date!

References: “RCA Transistor Thyristor & Diode Manual” Technical Series SC-14, RCA Electronic Components, Harrison, NJ