Recently, I was working on a few consultancy projects where upto 36V dc voltage input was required and that’s when I started looking around for some readily available modules and bought a few of them for the experiment.
I did not use this or any other dc dc module in the design but noted a few interesting observations. Will share about one of them in this post.
I found a 36V DC input to 5V @ 5A dc dc converter module in one of the online shops and tested the module.
This dc dc converter module uses Texas Instruments Buck Controller IC along with external Power MOSFET (Toshiba TPCA8053-H) and Power Inductor.
IC can take up to 40V DC Input but the module is rated for 36V and its current capability is up to 5A. Here is the Spec of TPS40057 Controller IC.
For the testing, I used a Owon’s 30V 5A DC Power Supply, Fluke’s multimeter, Fluke’s IR temperature Gun, Electronic DC Load to test the heating of the module at various load conditions as well as efficiency at different loads.
I tested for no-load current, temperature rise in 30 min at room temperature with 25W load, and the efficiency and here are the results:
1. Quiescent current
The quiescent current of the dc dc converter is quite high, without load it consumes 21-22mA.
So definitely this module cannot be used in a low power design.
A different hardware strategy need to be used even if you need 5A or more current when device works in high performance mode but in sleep mode most of the time.
Check this article for Low IQ DC DC Converters, I tested a few interesting ones and documented.
Temperature Rise after 30min
With a load of 25W, the module started warming up and in 30 min the max. temperature was at the MOSFETs and it was around 56-60 Degree C. I kept my room fan OFF at the time of testing.
For the 25W power supply, I would say it was running quite cool and it is because of high power low RDDS ON Mosfets and High Power Inductor which is used in this synchronous buck converter design.
I have worked with other dc dc converter ICs and at 3A rating they heatup a lot, upto 75-85 Degree C, so it is clear that to handle more power we need to use external Mosfet design, PCB with high copper thickness, and Power Inductor should be selected in such a way that it has least DC resistance.
DC DC Converter Efficiency
After temperature testing, I did the efficiency test at various loads and here are the results:
| Load (Amps) | IP Voltage(Volts) | IP Current(Amps) | OP Voltage(Volts) | OP Current(Amps) | Efficiency % |
| 0.2A | 12.0V | 0.091A | 5.13V | 0.18A | ~85% |
| 0.5A | 12.0V | 0.220A | 5.13V | 0.45A | ~85% |
| 1.0A | 12.0V | 0.485A | 5.10V | 1.00A | ~88% |
| 2.0A | 11.96V | 0.936A | 5.09V | 1.96A | ~90% |
| 3.0A | 11.88V | 1.447A | 5.07V | 3.0A | ~89% |
| 4.0A | 11.84V | 1.927A | 5.06V | 3.97A | ~88% |
| 5.0A | 11.82V | 2.467A | 5.03V | 5.0A | ~86% |
Please note that, I am not recommending this module to be used as it is in your product.
I baught two of these modules and one of the module did not even work so reliability of these module is a big question mark.
These are good for experiements, protos for feasibility testing but if you really want to use readility available module, use modules from a trusted company where quality is assured.
I hope you found this post interesting and learned somethig new today.
Please do share your feedback in the comments below, can’t wait to hear from you.
You can read my other interesting blogs & articles on embedded system design here.
I help embedded engineers and companies build reliable and successful embedded products. If you need any help please let me know here.
Happy Learning to you!