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.
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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
