The definitive MIDI controller | This is not rocket science

Testing the tiny switching regulators

The post for my tiny switching regulators wouldn’t be complete without some measurements. It’s easy to make a fake device that simply “does something” and still in the end doesn’t work like it’s supposed to. So here are some pictures of the regulator under load.

3.3V switching regulator under load 1

The input of the regulator is connected to a 9V power supply. The output goes into the blue/black box, which is my constant current load (more on these devices in a later post!), set to sink 800 mA. The voltage it’s showing is unfortunately too low; it’s measured at the end of all the wires, and thus includes wire losses. But the current is exact to the last digit. The regulator gives out 3.3V, and thus the total power consumed by the load is 3.3V * 0.8A = 2.64W.

According to its meters, the power supply is giving out 9V * 0.34A = 3.06W of power. notice that its current output is much less than 800 mA, so we’re indeed looking at a switching regulator. If we were measuring a linear 3.3V regulator, the power supply would have to also provide the full 800 mA, totaling 7.2W, and requiring a decent heat sink!

The efficiency of the switching regulator at this load is 2.64W / 3.06W = 86%. Nothing special there, at lower loads it improves a little bit, getting closer to 90%.

3.3V switching regulator under load 2

Here’s how the power output looks like on the oscilloscope. The ripple is at 13.6mV small enough to be difficult to measure on the Rigol oscilloscope, I couldn’t even get it to trigger correctly! The average voltage is very close to 3.3V.

The most important property of the regulator is of course its low heat dissipation, thanks to the high efficiency. The power was on for several minutes, and the regulator remained only slightly warm to touch. The power diode was the warmest individual spot. That concludes this wholly unscientific study. :-)

One Response

  1. You have some nice test equipment there. I have some old analog Heathkit stuff, which I could never afford when I was a kid, but at least the scope is faster than my old 5mHz single-trace. I’ve even got an analog frequency-sweep generator, which is nice.


    September 9, 2015 at 14:24

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