If you're looking for a benchtop power supply, but you're unsure of what you should be looking for in a decent supply for your workspace, we have got you covered with this guide. We will look at the specifications to look out for in a power supply and what they relate to. We are of the opinion that when you are powering your projects, you'll need a versatile, accurate and stable power supply that doesn't chew a hole through your wallet. After the walkthrough of the relevant specifications on Power Supplies, we will recommend a couple of products that we know are a great value and high-quality choice. The first thing (and often most important specification) you should know is the field you will be working in, at least the majority of the time. Specifically, I mean the specifications of the device under testing (or DUT). This is the device you will be using with your benchtop supply, so it's of paramount importance that your device can be safely powered by your supply.
Let us explore some of those specifications we'll look at the basics of power measurements, the differences in variable and fixed voltage/current supplies, current limiting supplies, linear and switching supplies, interfaces and what they're for before finally suggesting a price sensitive option and a high-quality option.
When it comes to power you have 4 units to be aware of, Current, Voltage, Power, and Resistance. These measurements all relate to each other with the simple relationship of Power = Voltage x Current and Voltage = Current x Resistance. It's very important that if you are supplying your circuit with some voltage, your supply can keep up with the current drawn. The power envelope of your power supply will be the defining specification here, and it relates to the current possible at the different voltages.
You can have all different kinds of power supplies with different power envelopes, but the most versatile option is a rectangular power envelope. This means that regardless of your voltage, you can always provide a maximum current, essentially you will be covered if you needed to increase the current limitation of your supply and not worry about being under-specked for the task.
Current Limitation and Variable vs Fixed supplies
Current Limiting Control is another feature of a power supply that we see commonly and if you're a beginner, you'll probably want to opt for a model with it. It can be a fantastic tool when prototyping circuits. You will know that although you can supply a maximum current of say 3A, you have limited yourself down to a safer current ceiling and protected any of your components. In addition to current limitation, you will also be able to set the voltage of your supply if you choose a variable voltage supply.
You can get variable or fixed voltage supplies, but for a versatile supply, you will undoubtedly want a variable voltage constant current power supply. The next question would be how many channels you will need on your supply. There are many different options available but we recommend at least 2 channels for a benchtop supply, as it allows you to have 2 supplies going simultaneously (Think of all the 3.3V and 5V projects!).
Each channel in your supply will have a resolution for both the current and voltage supplied. Resolution refers to the smallest possible change in these specifications with your supply. This, of course, comes right back to your DUT, if you are using a 3.3V board, and you want to power it with your benchtop supply; you'll need at least a resolution of 0.1V.
Linear vs Switching Supplies
As our supplies are taking an AC power supply and converting it into a DC supply, we can get some ripple and noise (unfiltered AC current and Voltages present at the output of our supply). There are two different supplies that we can get and they are Linear and Switching types. There's a ton of differences between the two relating to efficiency etc. but the short story is if you require low noise/ripple, you'll want to go with a linear power supply.
When it gets to the higher level usage of your power supply, you'll notice a bunch of computer interfaces being listed as part of the specifications of your power supply. Essentially these allow you to control your test and measure equipment over these interfaces, which can be a fantastic feature for engineers and technicians, but for a beginner, these interfaces are more of a nice to have, not a requirement.
Additional Specifications, if you're interested
On the datasheet and specifications of any of the supplies you look at there will be a few additional specifications to look out for, depending on your depth of knowledge and the difficulty of your projects they might not even be relevant to your intended usage, either way I have decided to include a brief discussion on the 'important' specifications.
Load Regulation - This is the amount that your supply will change its supply when the impedance (load) of the circuit changes from no load to full load conditions. It will be given on the datasheet as a measurement of < X% + Y mV or mA.
Line Regulation - This is the percentage of the output of the supply that changes as the AC input line are changing. It will be given on the datasheet as a measurement of < X% + Y mV or mA and you'll be looking for the smallest % and offset amount
Efficiency - Measured as a percentage, it indicates the amount of power being output over the amount of power consumed in the system.
Looking for something easy on your wallet but still a great quality supply? Go no further than this Laboratory DC Power Supply from GwInstek. It’s a Linear 2-Channel, 0-30V DC Power supply, supplying up to 3A on each channel which is great for hobbyists and techs alike. It's got 2 LED displays per channel with a resolution of 0.01V/0.01A. The knobs on the front panel give you access to each value, and you can run the supply in independent, series or parallel mode, with a single OUTPUT On/Off switch. This particular supply won't come with all the computer interfaces a more hardcore user might be looking for, though. The price point is absolutely fantastic for a beginner's first supply, so this would be our clear cut recommendation if that's what you're looking for.
If you are looking for a benchtop supply and price is no worry, we get that. Sometimes you're better off spending a bit more now and your purchase will last you a lifetime. You can't go past the DP832 power supply from Rigol if this is the case. It's a Linear 3-Channel DC Power Supply, with 0-30V @ 3A on Channels 1 and 2 and [email protected] on Channel 3. You'll get Over Current/Voltage Protection, per channel current limiting, minuscule Load and Line Regulation Rates and very reasonable Ripple/Noise specs. The in-built 3.5 inch TFT LCD screen is a nice addition too, as you get Power, Amperage and Voltage measurements displayed per channel as well as waveform display and Analysis and Monitor options. Each supply has it's own individual control options on the front panel and the values of your channels can be controlled by direct entry on the keypad. The supply also comes with a 3-year warranty from Rigol, which is simply awesome for this kind of purchase. Oh and you'll have (almost) every interface you'll ever need too, with USB host and device, LAN, RS232, RS485 and USB-GPIB all being supported on the rear panel. Rigol are renown for their high-quality testing and measurement equipment and you can see the entire Rigol range here, from Power supplies to scopes and signal generators, Rigol has top quality equipment for your setup.
Thanks for taking the time to have a read of this guide, if you have any suggestions for the Price/Quality products we've linked let us know. Alternatively, if you have purchased one of these 2 supplies, we'd love to hear how it has been going for you. Start the conversation about Benchtop Power Supplies with our community below!