TI-PMLK Buck Experiment Board - part 1c: 1st Experiment Measure

RE: TI-PMLK Buck Experiment Board - part 1c: 1st Experiment Measure

Jan Cumps — Mon, 10 Jul 2017 20:08:30 GMT

Here are switch node captures in non-continuous mode:

Switch frequency 500 kHz

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-8a3f2f0e-2613-4dac-9968-38709891e86f/0181.contentimage_5F00_185274.png:620:372]

Switch frequency 250 kHz

[View:/resized-image/__size/620x372/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-8a3f2f0e-2613-4dac-9968-38709891e86f/3323.contentimage_5F00_185275.png:620:372]

RE: TI-PMLK Buck Experiment Board - part 1c: 1st Experiment Measure

balearicdynamics — Sun, 25 Jun 2017 18:51:12 GMT

All the blog are very well done Jan, better than many theory only explanations to learn a lot. Love this approach.

Enrico

RE: TI-PMLK Buck Experiment Board - part 1c: 1st Experiment Measure

jc2048 — Sun, 25 Jun 2017 17:44:45 GMT

It's obvious that my current measurement method (blue in the capure above vs. green in the TI manual) is not up to the game.

I don't know - it's quite good for something that you've improvised. But you have your blue trace upside down [just swap the secondary coil ends]. Then, if you integrate the waveform, you get back to the primary current. (The induced voltage is proportional to the rate of change of the current in the sense resistor.)

The biggest problem with what you are doing is that you lose the dc component - you see the ripple, but not the dc offset from zero [which isn't very good if you're trying to learn the fundamentals of dc-dc converters].

The 20A/50MHz probe they recommend would work in a similar way - integrating the output of a coil for the high-frequency part. Difference is that it would also have some way to do the dc and low-frequency part (a hall-effect sensor).

RE: TI-PMLK Buck Experiment Board - part 1c: 1st Experiment Measure

DAB — Sat, 24 Jun 2017 19:06:22 GMT

Great post Jan.

I was surprised to see the efficiency drop with the higher input voltage, so I learned something today.

DAB