I'm reviewing a set of inductors for the Experimenting with Magnetic Components design challenge. At the end of the design challenge, I'd like to revisit the boost converter I made at the start.   In this post, efficiency measurement, and a number of current vs. voltage captures of the circuit's Bourns RLB Series 1mH Radial Lead InductorBourns RLB Series 1mH Radial Lead Inductor under different conditions.

Measuring Efficiency

The circuit is measured in 3 different scenarios: output at 20, 30 and 40 V, with a 2K7 load.

In each of these scenarios, I swept the input voltage between 9 and 12 V, in 0.5 V steps.

The 20 and 30 V scenarios are measured with 100 kHz switch frequency, 40 V is done at 60 kHz.

I recorded the duty cycle and input current, and took an oscilloscope capture each time.

The circuit is the same as used in posts 1 - 3

Results

How I measured:

I've done each measurement by hand. My function generator doesn't have a programming option.

I first set the input voltage to the desired value.

Then I modified the duty cycle to get the requested output voltage.

Because changing duty cycle on my generator changes the frequency, I then play with both duty and frequency controls until the output voltage, and frequency are where they should be.

I then recorded the duty cycle and the input current. The duty cycle out of interest, the input current because I need it for the efficiency calculation.

Each time, I captured the oscilloscope screen. These images are posted below.

Here's an extract of the spreadsheet I used to calculate efficiency. It's also attached to this post.

To put this on a graph, I first created a pivot table that maps out efficiency vs. input voltage, for the 3 output voltages.

I've also set out the efficiency vs. output voltage, for different input voltages:

Oscilloscope captures for each measurement point

(click to enlarge)

VOUT = 20 V, f = 100 kHz

VOUT = 30 V, f = 100 kHz

VOUT = 40 V, f = 60 kHz