SSZTBX0 November   2015


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    2.     Energy-saving Schemes of DC/DC Converters – Do They Really Help?

Rich Nowakowski

Energy-saving Schemes of DC/DC Converters – Do They Really Help?

This weekend it was raining pretty hard, so I decided to tackle a project I’d been putting off for a while. I went to the hardware store and bought LED bulbs to finish installing them around my home. After all that hard work, I decided to dissipate in front of the TV and catch up on pre-recorded episodes of “Shark Tank.” Since I am a power guy at heart, I realized how many wall adapters and appliances in my home could be also wasting energy (like me) and how meeting Energy Star requirements can really help conserve resources.

Meeting Energy Star requirements to maintain energy efficiency is a constant design challenge. As the number of consumer devices in homes increases, taking energy from the grid, designers want to improve light-load efficiency without increasing cost or complexity. I found out that if all set-top boxes sold in the United States were Energy Star-compliant, the savings would be more than $1.8 billion per year, preventing more than 24 billion pounds of greenhouse gas emissions.

An obvious place to look for efficiency savings is the AC/DC supply, but point-of-load (POL) DC/DC converters can also help designers meet Energy Star requirements. Many POL converters from Texas Instruments offer an energy-saving Eco-mode™ pulse-skipping technique, so I had to see for myself how a conventional DC/DC converter compared to one with the Eco-mode control scheme. I looked at the TPS563210, a 4.5V to 17V input, 3A synchronous buck converter, recording the amount of power dissipated in watts versus a traditional efficiency plot that displays a percentage (Table 1).

Table 1 Power Dissipation in Watts
Device TPS563210 at 1.5V/3A TPS563219 at 1.5V/3A
Eco-mode control scheme Yes No
No load 0.006W 0.062W
10mA 0.007W 0.062W
100mA 0.03W 0.066W
25% full load 0.14W 0.14W
50% full load 0.32W 0.32W
100% full load 1.15W 1.16W

The power savings was significant. If the system included four POL converters, a rough estimation of the power dissipation at 10mA loading would be 28mW with the Eco-mode control scheme and 248mW without the Eco-mode control scheme. This translates to a savings of about 2kWh per year! With all those set-top boxes out there, the savings add up quickly.

How Else Have You Saved Energy in Your Projects?