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Editorial notes
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Tuesday, 05 September 2006 |
RoHS garnered a lot of ink in the trade press in the run-up to its going into effect. But in addition to RoHS, there is another European specification that can have a major effect on your product’s design.
The International Electrotechnical Commission specification IEC 1000-3-2 limits the harmonic component of the input current for line-powered systems of 75W or greater. This specification applies to consumer products in Europe and its net effect is that line current harmonics must be improved using either passive or active power factor correction (PFC).
Passive solutions use components such as line inductance and DC link chokes which are too heavy and bulky for practical implementation and may not be sufficient to meet future revisions of the IEC spec. Active solutions are elegant, but generate EMI and cost more. The cost of power factor correction is $0.10 to $0.30 per watt - enough to double the cost of the power supply and make the system cost uncompetitive.
As the secondary power approaches 75W, the overall power supply efficiency becomes critical, because it will determine if power factor correction must be used. For example, a set-top box that requires 60W of secondary power must have a power supply with at least 80% total conversion efficiency if power factor correction is to be avoided.
Achieving that 80% efficiency can mean adopting a sophisticated point-of-load power-supply architecture and employing micropower components. A point-of-load power supply converts the input mains voltage to an intermediate voltage – say 12V or 24V. This intermediate voltage is bused around the pc board and is converted locally into needed supply voltages. Such a power-supply architecture and achieve the required efficiency at a small price premium over single-inductor/multiple-taps supplies.
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Editorial notes
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Thursday, 04 May 2006 |
I can still remember the first time I saw a solid-state MP3 player. I was in a Fry’s, the legendary electronics chain in Silicon Valley, looking for a new modem card for my PC. Right in the middle of a shelf of modems was the Diamond Rio MP3 player. Thinking it was a modem, I pulled one box from the display and read the blurbs on it. It took me a little while to figure out what I was looking at. I was familiar with the MP3 audio compression work of the Frauhoffer Institute in Germany and playing MP3’s on my PC with WinAmp. When I figured out what the Diamond Rio was, I said to myself, “This is the end of the Walkman as we know it.”
For once my crystal ball was correct. Apple recently announced the one billionth download from iTumes. At $0.99 a pop that is a nice piece of change for Apple. And according to In-Stat, the worldwide market for Flash-based and Hard Disk Drive (HDD)-based players reached 140 million units in 2005, up from 35 million units in 2004. Expectations for this market are high, with In-Stat forecasting unit shipments to reach 286 million by 2010. Drivers for this thriving market include falling price points, the availability of legitimate subscription and pay-per-download online music sites, increasing Flash memory capacities, and enhanced functionality.
–Charles H. Small, editor |
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Last Updated ( Friday, 18 August 2006 )
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Letters to the Editor
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Wednesday, 29 March 2006 |
I'm using a Digital Data Synthesis system for waveform generation, but I need to find a way to reduce the noise. What are my best options ?
- PJ, Massachusetts
Dear PJ,
Here are the main things I would consider:
- Start with a high quality, high precision data source such as a CPU or DSP with high memory content.
- Follow with a very good DAC.
- Use a high performance fixed or programmable reconstruction filter.
- Finish with a low distortion, low noise programmable gain stage.
Hope that helps!
- Charles
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Last Updated ( Friday, 20 April 2007 )
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