How to choose the best benchtop DC power supply06/16/2022
Working on the prototype of one of the new Bike Pixel model, I’ve started to miss a benchtop power supply. They are devices that provide us with a regulated DC voltage and current. This makes them ideal for testing prototype designs or new components. It is one of the tools that should be present in any electronics workshop.
There are a multitude of options, so we must select the one that best suits our needs and budget. You must take into account its characteristics but also other factors such as quality and safety. A good regulated power supply must provide a stable and accurate voltage and current, with minimum noise at any type of load. How well the power supply fulfils this task and where it reaches its limits is defined in its technical specifications.
Technical specifications to be compared
Although the technical specifications can be very exhaustive, when choosing your benchtop power supply, it is advisable to look at least at the following parameters:
Maximum voltage and current
Most benchtop power supplies move in voltage ranges between 0 and 30V and currents from 0 to 10A. If our projects are outside this range we will have to work with more specific (and also more expensive) equipment.
Number of channels
Specifies the number of current outputs. Normally one will be enough but as we begin to work with more complex circuits we may need some extra sockets. They are more expensive but the investment is worth it in the long run. In addition they allow different working modes being able for example, to connect the outputs in series or parallel in order to allow higher voltages and currents.
The resolution is how small a change can be made on voltage or current. Unless we are dedicated to circuit analysis or work with very sensitive components, equipment with a resolution of 10 mV and 1mA will be more than enough.
It determines the difference between what you see on the display and the actual value output by each channel. Usually only a few mV and mA. As you have probably already guessed, more accurate equipment is more expensive.
DC power supplies usually have different controls for setting voltage and current and displays showing the selected values.
In more modern and advanced models, these are complemented by screen displays that include memory setup, current charts, signal programming and other additional information.
Linear or switched
Depending on the way they convert alternating current into direct current, bench top power supplies can be either linear or switching:
- Linear power supplies use classic transformers and are therefore usually larger, heavier and less energy efficient. But among their advantages are that they are usually cheaper, generate little noise and ripple at the outputs.
- Switched power supplies work by filtering alternating current into pulses with a frequency of around 60 kHz and feeding it into a transformer. They are much smaller, lighter, more efficient and therefore give off much less heat. But the signals generated can be noisy and they are usually somewhat more expensive.
Programmable or non-programmable
To be able to perform automated tests and more in-depth testing of our prototypes we can consider using programmable laboratory power supplies. They are somewhat more complex and intended for more advanced users.
Include a more complete interface and the possibility of connection to our PC via USB or serial port allowing us to program sequences of voltage and current values. Thus we can analyze how our circuits respond to different situations and check how our prototypes perform under anomalous situations.
Tips before you buy
Beware of clones
Sometimes the same equipment is camouflaged with different brands by simply modifying the name, adding a certificate or some other accessory and of course increasing the price. For example in the following case we have the same adjustable power supply but with different prices. The original manufacturer is SIGLENT, with a price of $399. Then we have two clones, one of the brand RS-Pro (at $528) and another Teledyne (at $815).
Best benchtop power supplies are equipped with various safety features. They are designed both to protect the power supply from misuse and to prevent damage to the electronics that are powered by them. Therefore, before purchasing a power supply, it is important to check that it includes safeguards against:
- overvoltage and overcurrent (OPV and OPC),
- short circuits.
All of the adjustable power supplies listed below are equipped with these safety measures.
Comparison of best benchtop power supplies
Following you can found all the power supply models that I was comparing before buying mine along with links where you can purchase them.
In general they are all pretty good and you can use them in any project. Normally with a single channel will be more than enough but for more professional uses we can opt for more channels or sources with greater precision.
This is a DC power supply model quite affordable and designed for anyone. It presents a very simple interface in which we can adjust voltage and current.
It has all the safety measures available in the more expensive models. We can set both the maximum current and voltage limits (with the OCP and OVP buttons respectively).
As an added bonus, its accuracy is quite good and it has three memory buttons to save our most common settings.
Although I have hesitated a lot if not save a little more and buy a model with more channels in the end I have opted for this power supply. It is a programmable laboratory power supply and has a modern user interface.
Apart from the DC output channel it has two USB ports, one with a fixed output of 5V and up to 1A and another (on the back) that allows us to connect it to our computer (only for Windows unfortunately). In this way we can update and control the device.
In addition, unlike the most common models, it has a 2.8-inch TFT screen that gives a more modern touch to its user interface with different display modes and more saving and configuration options.
|Precision||Voltage||≤0.1% ± 20 mV|
|Intensity||≤0.1% ± 10mA|
|Channels number||1 + USB 5V1A|
|Programmable||Yes (USB PC)|
Before moving on to devices with more than one channel and simply as a comparison I leave you with this professional regulated power supply. Its price is quite high but in return we get a very accurate device with an advanced user interface including a 3.5 inch LCD screen. Not suitable for beginners.
It allows to obtain very stable and noise-free signals with a very high resolution. In addition, the manufacturer offers a 3-year warranty so we can assume that it is a very durable equipment.
SIGLENT SPD3303X-E y SPD3303X
Moving on to multi-channel power supplies, the SIGLENT SPD3303X series are semi-professional devices and, as we have seen before, are also cloned for other manufacturers due to its good quality. In this case we have 3 channels. Two of them are fully adjustable and a third with standard outputs at 2.5V; 3.3V and 5.0V with up to 3.3A.
It has a very attractive interface and a large 4.3 inch display that allows different display modes. In addition, this model has a high precision version (SPD3303X) in which we can obtain signals with a resolution of 1mV and 1mA. Finally, it should be noted that apart from being able to perform its programming with the included software, thanks to its support for the LabVIEW controller we can use Python for its programming.
|Channels number||2 + 1 up to 5V|
|Programmable||Yes (USB PC)|
|Size||16 x 13.3 x 10.4 inches|
|Weight||17.6 Pounds||17.8 pounds|
Finally I leave you another professional model. It has 3 independent channels, two of them up to 30V at 3A and another one up to 5V at 3A. It features very low output noise, excellent performance metrics and multiple analysis functions.
It has an advanced and very complete user interface on a 3.5 inch TFT screen. It also offers multiple connection options for programming including LAN, USB, RS232 serial port and Digital IO.
|Precision||Voltage||≤0.01% ± 2mV|
|Corriente||≤0.01% ± 250uA|
|Channels number||2 + 1 up to 5V|
Conclusion and more information
The day finally comes when we need more than just our Arduino or that old cell phone charger to power or test our prototypes. That’s why a good adjustable power supply is a must. Before buying yours do not forget to check all the technical specifications and above all, if they have the basic safety measures.
Below are links to the full technical specifications of some of the equipment reviewed: