We've been tracking an interesting trend in the POE world and it should come as no surprise to anyone who pays an electricity bill… or knows someone who pays an electricity bill: Growing concern with total power consumption over a product’s lifetime.
Total cost of ownership is generally considered to be the sum of CAPEX (capital expense.. or purchase price) and OPEX (Operating Expenses… or what it costs to run ). Designers and hardware development managers have historically been more concerned with CAPEX than OPEX, but are starting to see a shift toward total cost of ownership as the correct metric by which to judge solutions. This is coming from the end users who actually have to pay to purchase and run such equipment.
A similar shift started in the telecom industry a few years back when we started seeing board/system redesigns expressly for the purpose of increasing efficiency. Until that point all telecom boards were using ORing diodes to merge the redundant -48 V feeds on high and low side. Using FETs and ORing controllers was viewed as far too risky when diodes were cheap, rock solid, and 100% derating was easy. Enter customer demands for higher efficiency and ORing FETs with controllers began appearing in many designs. Now, they are the norm. It’s not often that efficiency can be boosted by 1.5% with a simple change like that.
Today’s example is Power over Ethernet (PoE) solutions; Specifically, PoE cameras.
With many IEEE compliant POE solutions available today there are not many ways to differentiate a solution. More features and gee whiz functions are not necessarily the best way to impress the majority of the IT, security, and infrastructure buyers around the world. What seems to draw the most interest is low cost of ownership, which means low OPEX.
The math is pretty simple, even if some assumptions are used.
Lifetime Savings = Number of Cameras x $/kWh x 22hours/day x 365days/year x 10 years x 1kW/1000W x (PDIS_NORMAL – PDIS_HIGHEFFICIENCY)
Running some numbers through the equation above, a facility with 100 cameras paying $0.14/kWh will save almost $400 in ten years.
This savings will not require extra upfront silicon costs and that $400 goes right to the bottom line. (Note: The assumed electricity costs were based on relatively low US pricing. In Europe, the savings will be 2 to 2.5 times as great, and those costs are only going up.)
But Tex…How can my design reduce POE OPEX ???
A fine question.
TI has recently released two POE PD controllers specifically designed for high efficiency over very broad load ranges. The TPS23751 and TPS23752 operate as standard isolated flyback converters while under load. When the load drops off and the device goes into idle, three features kick in to reduce power consumption:
Wishing you lower energy costs,-Jim Bird
Index of all Power House blog posts.
Tell me, how has this helped you in reduce operating expenses?
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