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How to choose a power supply

Power supply, as one of the most fundamental electronic development tools, plays an indispensable role in the field of testing and measurement. DC regulated power supplies have been widely used in single-board development and testing, battery testing, and other fields. Choosing a suitable DC power supply can greatly facilitate development testing and production debugging. With the help of the following 10 considerations, you can choose an economical and practical DC power source.

1. Types

DC power supplies are mainly divided into two types: linear and switch-mode. Linear power supplies first reduce the amplitude of AC voltage through a power-frequency transformer, then rectify it through a rectification circuit to obtain pulsed DC voltage, which is then filtered to obtain DC voltage with small ripple voltage. To achieve high-precision DC voltage, voltage stabilization circuitry is required for voltage stabilization.

Switch-mode power supplies directly convert rectified AC voltage into AC voltage, and then control the on/off of the current with a switch under the action of a high-frequency circuit oscillation to form high-frequency pulse electricity. A stable low-voltage DC output passes through the inductance.

The features of linear power supplies and switch-mode power supplies are different. The advantages of linear power supplies are high stability and load stability, low output ripple voltage, fast transient response speed, simple circuit structure, and no switch interference. However, there are also some disadvantages, such as high power consumption, low efficiency (generally only about 45%), large size, heavy weight, and inability to be miniaturized without large-capacity filtering capacitors. The disadvantages of linear power supplies are also the advantages of switch-mode power supplies. Switch-mode power supplies have larger ripple due to their switch structure, and their circuit structure is more complex. Nowadays, switch-mode power supply technology is constantly improving, and performance is constantly improving. In addition, switch-mode power supplies are used in high-power supply fields. Therefore, when selecting a power supply, it is necessary to choose according to the project requirements. If purity, interference-free operation, and sensitivity to ripple are required, it is recommended to choose a linear power supply. When high efficiency and miniaturization are required, it is best to use a switch-mode power supply.


Figure 1 UNI-T DC power supply overview

2.Output capacity

Figure 2 UDP6700 wide range working mode


 Figure 3 UNI-T DC power supply product portfolio

The output capability of a power supply is often the primary factor to consider, as it directly relates to the range of products it can be used for. Generally, an output voltage of 30V is sufficient to cover lighting, mobile phones, portable computers, wearable electronics, communication terminal equipment, and most power modules. The UDP6700 series increases the output voltage to 60V and 80V, and the maximum output current is 30A, covering a range of communication power supplies, electric vehicles, and various battery packs. Moreover, the UDP6700 series adopts wide-range output technology, combining three small power supplies into one, bringing more benefits to users.

Here’s the UNI-T DC power supply product portfolio for your reference.

3. Number of Channels

If you only need one channel for an automated testing or production environment, a single-channel switch-mode power supply is a good choice because of its superior performance, compact design, and light weight. However, sometimes there are multiple power supplies on a product's single board that need to be tested. If you test them one by one, it will waste time and manpower, so there is a demand for multi-channel power supplies. UNI-T linear multi-channel power supply comes with a standard output for the third channel, which conveniently provide a fixed voltage output by pressing a button. The output range of the two main channels with equal performance is ideal for the application requirements of multiple product fields. By the way, they are linearly adjustable.

Note that there is a very important indicator that needs to be considered. When you choose a multi-channel power supply, be sure to pay attention to whether all channels of the power supply are isolated. Isolation between channels is critical for reliable performance and safety operation. UNI-T multi-channel power supplies come with full-channel isolation design. On top of that, our power supplies also ensure the isolation between communication and output, which makes multiple machines remote control an easier task.

UNI-T multi-channel power supply also provides a quick function key for series-parallel operation, which instantly switches the 30V, 5A output channel to 60V, 10A, greatly expanding the output range. This function also provides convenience for laboratory applications in the education field.

Figure 4 UDP3305S four-channel output power supply

Figure 5 Function key for series and parallel connection

4. Remote Control

Figure 6 UDP3305S PC software interface


Figure 7 Programmable and non-programmable product overview

Nowadays, automation is the technology trend for not only testing and measurement but also production debugging. Therefore, when choosing a DC power supply, you need to define whether a programmable or a non-programmable device is needed. UNI-T provides you with a wide selection of power products meet your needs. We mainly offer programmable power supplies with PC software as well as SCPI communication protocol compliance, which help automation control platform buld-ups.

The UDP3000S series power supply comes with multiple communication ports , including USB, LAN, and RS232. You may  select from the remote control commnications port accordingly as needed.

5. Performance Indicators

In addition to the above four factors, let’s move onto the performance of the power supply. The load regulation and linear regulation of a power supply directly affect its load capacity. Choosing a stable and high-precision power supply improves the overall quality. Ripple is always an important indicator of DC power supplies, and in some industries that require pure power supplies, such as the semiconductor industry. There is an even higher requirements on ripple for wearable electronic products.

The UNI-T UDP3305S DC power supply with a ripple of less than 350μVrms/2mVpp, ensures a high-purity DC source. For the switching power supply UDP6700 series, its ripple is also less than 2.0mVrms. You can also find good adjustment rate and accuracy for UNI-T power supplies.


Figure 8. Ripple of the UDP3000S series.


Figure 9. Protection functions of UNI-T DC power supply.


Figure 10. Monitor function of UDP3000S

Safety is key to a power supply. The protection against overvoltage, overcurrent, and overtemperature are the basic features of a power supply. These protection measures can prevent damage to itself and the load in case of input abnormality, preventing unnecessary losses. In addition to input protection, output protection should also be considered. Configurable protection level according to the tested load is designed to ensure the safety of the tested product.

UNI-T DC power supplies protect your testing with OVP, OCP, and OTP protection functions, as well as configurable output limit function. In addition, the UDP3000S series with a monitor function help you better control the load limit for tests.

7. Advanced features

Is a DC power source just providing stable voltage and current? Do we need more efficient functions? The answer is yes. Imagine you are conducting a power on/off experiment, pressing the switch 1000 times repeatedly. It is such a waste of manpower, time, and money. The timer function help you solve this issue. In addition, the list function loads the changing voltage and current to the tested load end, test its tolerance ability, and save you the trouble of repeated adjustment. This can greatly assist you in aging tests. What’s better, there are more concise and intelligent functions, such as the monitor function described above, which may meet you need.

Both the UDP3000S and UDP6700 are equipped with list and timer functions. The UDP3000S series, with its 4.3-inch screen, offers even more diverse display functions, allowing the output visualization during testing. This intuitive design makes testing work easier.



Figure 11. LIST and DELAYER


Figure 12. Save function for UDP3000S


Good user interface design is essential for instruments. Display is especially critical. The displayed information should be comprehensive, clear, and easy to operate, which will surely improve the work efficiency. The UDP3000S equipped with a 4.3-inch full-color LCD screen, displays the data, presets, and protection values of the three channels in parallel classified by three colors, making it clear and easy to understand. The UDP6700, a compact design power supply, equipped with a 2.8-inch full-color LCD screen, comes with a clear display and a good user experience.

Figure 13. UNI-T classified color display


Configuring communication interfaces makes remote control and automation possible. The common interfaces for power supplies are RS232, USB, and LAN. The UDP3000S power supply equipped with all three interfaces, makes remote control more flexible. In addition, there is a USB host port for connecting external devices for storage and retrieval.

In addition to communication interfaces, there are different characteristics for power supplies. Long power cord may cause significant voltage drop, so a remote compensation port is it’s a good idea. The UDP6700 series is equipped with a remote compensation port, which can adjust line loss by connecting to the remote load sense wire to ensure a stable power supply. At this time, the voltage displayed on the power supply is the remote load voltage, which ensure the accuracy of the measurement.


Figure 14. Various interfaces

The above 10 considerations will help you choose a high cost-effective DC power supply. If you have any questions, please feel free to contact the UNI-T tech support. We will be more than happy to assist you whereas possible.

Recommended Products


UDP3000S Series


UDP6700 Series