I am curious what characterisation data for cheap DC-DC buck converter would be useful to others or even if the data has been previously provided.
In my experience I have found a mix of results even among a batch of identical modules and therefore almost impossible to determine what is viable from an ebay listing.
As such I thought a repository of all things relating to these cheap modules maybe useful.
Things to consider may include:-
1. Pin pitch
2. Vpp Ripple at a given Vin, Vout Iout. How much ripple is too much?
3. Vin, Iout where the module shuts down
4. Ripple Freq
5. Other
There are many cheap adjustable DC-DC converters available from ebay.
However, the casual buyer has no real data (apart from the very optimistic specs below) to base decisions on so I am curious if it be worth publishing the data and charts along with the python script etc. If so where would be the best forum, (here, hackaday, youtube).
Thus far I have automated a characterisation test. The test is basically:-
FOR Iout = 0 to 2.5A in 50mA steps
FOR Vin = 7V to 21V in 250mV steps
Measure Vin, Iin, Pin, Vout, Iout, Pout, Efficiency, Vpp, Vripple-freq
Terminate if Vout deviates more than 0.4V
Loop Vin
Loop Iout
The setup uses SCPI commands via telnet to control DP832A (Rigol bench PSU), DL3021A (Rigol DC load) and SCPI commands via HTTP POST requests to control RTB2004 (R&S Scope) to measure ripple and freq.
I now have many tables and graphs see example attached but I would like to know what data is most important or useful.
I am hopeful for suggestions on ideal step sizes for Vin and Iout, Vpp and Vout delta limits etc. What parameter is best to plot against which parameter. i.e Current verses Ripple for a given fixed input voltage or Efficiency verses Vin for a given current (similar to the attachment)
An example of the data usefulness: It can be seen from the graphs etc that the optimistic efficiency spec of 96% is almost achievable if Vout is set to 5V, Vin is 7V and load current is about 200mA.
Below is ebay (very optimistic) specs for A DC-DC module identifiable by D-SUN silkscreen and MP1584 controller:-.
Input Voltage: 4.5-28V
Output Voltage: 0.8-20V
Output Current: Rate Current 3A(MAX)
Switching Frequency: 1MHz
Output Ripple: less than 30mV
Efficiency: 96%(max)
All thoughts, suggestions warmly welcome.