< > [Power](../) > Buck Converter
## Buck Converter
#### Efficient Step-Down
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While Linear Regulators just burn excess voltage off as heat, Switched Mode Power Supplies (SMPS) are a bit smarter, and can be ~95% efficient.
#### Operating Principle
Basically, we PWM some voltage at a duty cycle roughly proportional to the voltage output that we want, so t_pwm = v_out / v_in
Then we filter that PWM output to get a steady voltage.
The [wikipedia page](https://en.wikipedia.org/wiki/Buck_converter) actually explains in what looks like a good deal of detail.
#### Closed Loop
[Fancy DRV Buck](http://www.ti.com/lit/ds/slvsb56c/slvsb56c.pdf) uses feedback to match an output voltage, given varying input voltages.
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