# Why is the electronic circuit called "buck" converter?

Asked by thetas49 (194) July 20th, 2010

A buck converter is used in electronics to convert a dc power to
a different dc power, but why is it called “buck”?

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http://en.wikipedia.org/wiki/Bucking

Basically… the converter uses the Inductor to “buck” the voltage up. That is… when the switch is opened, the inductor “bucks”, increasing the voltage.

grumpyfish (6618)

Great thanks, but my understanding is that the converter can also decrease the voltage, “buck” implies increase, or does it?

thetas49 (194)

I think ‘buck’ implies decrease and ‘boost’ implies increase.

jfos (7362)

Also, some definitions for the verb form of buck are “to resist or oppose obstinately; object strongly to,” and “to split or saw (logs, felled trees, etc.).”

jfos (7362)

Makes sense, but the term “buck” is not really apt in this sense, I can’t see it as the opposite of “boost”, unless it has a meaning I’m not aware of.

thetas49 (194)

@jfos Is correct. Being simple here, a buck converter is just stepping down dc voltage in a very power effecient way without using too much energy/heat to accomplish this. A boost dc converter will do the opposite, step up the dc voltage (voltage multipliers in computer and tv monitors are a good example of this).

It is the same with a buck/boost transformer as well. The boost transformer will step-up the ac voltage for a small application in a circuit and the buck transformer will step down the ac voltage. One exception to a buck/boost application of controlling ac voltage is also the control of pulsed dc voltage as well. Using layman’s terms here.

Jabe73 (4010)

@thetas49 I got ahead of myself here and completely missed your real question. The term “boost” has an obvious meaning here but the term “buck” I am not as sure of this one myself. I looked at all the definitions for buck and none of them seems to match the term it is used for in electronics. I’m not sure why the word “buck” is used here in this way. I never really thought of this myself. I will see if I can find anything more on this.

Jabe73 (4010)

I’ve heard it said that the definition comes from somebody saying “I can make that circuit for less than a buck”, but that sounds suspicious to me.

thetas49 (194)

Yes “buck” is to oppose surely. The simple way to drop voltage is to use resistors but they get hot and use battery power.
A buck regulator uses the opposition of a coil to changing current (back EMF) to drop the voltage
Of course this opposition only lasts while the current is being switched on or off so a buck converter is constantly switching on and off to provide the buck. I E kick back to oppose the rise in current
This system causes very little heat and therefore uses less battery power
PS Don’t mean to talk down to anyone technically

mzman (1)

I’m with mzman. Buck as in bucking a trend is close, but I think that buck as in a bucking bronco is the real derivation. I believe it refers to the way inductors react to square waves, the way they “buck” (as in kick) at the rising and falling edges. You can almost picture a little bronco in there alternately digging in his front legs and then kicking up his back legs.

swampy (1)

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