Review on DROK 90483 8A/100W DC Car Power Supply Voltage Regulator Buck Converter, 12A Max, DC 5-40V to 1.2-36V Step Down Volt Convert Module by Andy Tunes

I'll start this review by saying that I like this module. It appears to be very well constructed and it is a marvel of Chinese manufacture that it can be sold at such a low price. Try estimating the cost of various components and heatsinks and you'll see what I mean. On the downside, along with the low price, there will also be some hiccups in infant mortality, so you could end up with the occasional 'smoker'. I bought this converter as an input regulator for a desktop programmable power supply I'm building. I only need a maximum of 3A at 3-26V, so I haven't tested it beyond those values. I can say that under these conditions the module almost does not heat up. Good heat dissipation and decent efficiency of the built-in switch. However, some information about the actual specifications of the module seems to be missing. In one place the data sheet says a maximum input voltage of 30V, in another it says a maximum of 40V. So what is that? For the record, I'll be powering it from a 24V AC transformer with a full-wave rectified voltage of about 32V, that makes a difference to me. XL4015. You won't be able to see any labels on the regulator's body without desoldering a few components, which I didn't want to do. To answer these questions, I ran some tests. First, using a digital oscilloscope, I measured the switching frequency at around 180kHz with some changes under load. (Ppp was about 60mV under load.) I also measured the built-in reference at the feedback pin to be 1.25V. BTW, XLSemi doesn't list XL4012 as a product anymore - it's probably obsolete.) However, XL4015 is still a candidate. It has the correct switching frequency and voltage reference, but is only rated for 5A continuous current. However, the XLSemi product page (http://www.xlsemi.com/product.html) lists the XL4016, which exactly meets the spec for this DROK controller. If you open the datasheet for the XL4016 (http://www.xlsemi.com/datasheet/XL4016%20datasheet.pdf) you can see: 1) It is rated for 40V input (which makes me happy) 2) It is designed for 8 A continuous output current (with suitable heatsink) 3) It has a switching frequency of 180 kHz and a reference voltage of 1.25 V. I made additional measurements on the module itself. The XL4016 data sheet states that the minimum input voltage is 8V. However, when I set the output voltage to 3.0V and connected a 2 ohm load (1.5A output), I was able to drop the input voltage down to 4.05V before that regulator started to disappear. Therefore, it works well at lower voltages than the XL4016's 8V spec, but with a slightly higher voltage drop. Finally, I looked at the voltage setting resistors. Potentiometer 50 kOhm. The regulated output voltage is set according to the following equation: Vout = 1.25V * (R2/R1 + 1) where R2 is the potentiometer setting and R1 is a fixed 1.5kΩ resistor (a small surface mount component found on located on the underside of the circuit board directly opposite the controller feedback input). Of course, this equation only applies if the input voltage exceeds Vout by at least the voltage drop. Someone noticed that they want to replace the potentiometer with a digital potentiometer. I plan to try this too. But it's not that easy to just add a digital pot. Almost full output voltage appears across R2, and very few digital potentiometers can withstand more than 5V. So the digipot is more likely to explode if you drop it. There are a few digipots that can handle higher voltages, but they are surface mount components. I personally prefer to work with continuous components because I don't enjoy designing PCBs when trying out new circuits for a project. However, there is a way to use low voltage digital potentiometers in these applications. More on that later, maybe for those who are interested. Post note: (03/15/15) I was able to replace the 50k potentiometer with a digital potentiometer (8 bit) and it works great with a step resolution of 100mV in my application. . To get around the 5V max voltage limit of the dihypoth I was using, I had to add some additional components - mainly a secondary op amp feedback circuit. Very simple, and if necessary, you can increase the resolution.