How to Choose a Switching Power Supply?

In your daily life and work, you often encounter different types of switching power supplies with various specifications like voltage, current, power, and load characteristics. It can be overwhelming, and you might not know how to pick the right one. To help you make a good choice and avoid mistakes, here are some tips for selecting a switching power supply. This way, you can opt for reliable switching power supplies and get better performance.

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Method 1: Choosing a switching power supply as your needs

Usually, you only consider buying a new power supply when your current one stops working. You can take your old power supply and contact companies that sell power supplies to find a suitable replacement model with matching specifications. Here are the key factors to consider for a replacement:

1. Input and output types of switching power supply

Input and output types can be roughly divided into ①AC/DC ②DC/DC ③DC/AC

Note: AC means alternating current, DC means direct current, such as AC/DC means AC input and DC output.

2. Input voltage

It is commonly used input voltage specifications include 110V, 220V, and universal input voltage (AC: 85V-264V). The input voltage specification should be selected according to the area of use.

3. Output voltage, current

When selecting a switching power supply, focus on matching the voltage first, and then consider the current. Make sure the power supply’s rated current is higher than the maximum current your load requires. For example, if your circuit needs 15V and draws 60mA, it’s advisable to choose a power supply rated at 100mA or more. Also, if the voltage matches, having a power supply with a higher current rating won’t cause any harm; only the needed current will pass through the circuit.

4. Switching the power supply function

① Regulated switching power supply: the input voltage and output voltage are rated at a certain value;

②Thyristor switching power supply: the output voltage can be changed by adjusting the input voltage;

③Adjustable switching power supply: within the rated range of the input voltage, the output voltage and current can be adjusted by means of potentiometers, etc.

5. Switching power supply load characteristics

For enhanced system reliability, it’s recommended to operate the switching power supply at a load of 50% to 80%, which means choosing a model with an output power rating of about 30%. For instance, if your power usage is 20W, select a switching power supply with an output power of 25W to 40W. When dealing with loads like motors, light bulbs, or capacitive devices, where there’s a surge in current during power-on, it’s important to choose an appropriate power supply to prevent overloading.

6. Ambient temperature

Consider the operating temperature of the switching power supply, whether you need extra cooling, and whether you should reduce the power output if it’s too hot. Consult the derating curve that shows how the output power changes with varying ambient temperatures.

7. Switching power supply power

Using a switching power supply at full load for extended periods can reduce its lifespan. So, it’s advisable to choose a power supply model with an output power rating that’s about 30% higher to ensure longevity.

8. Other needs

  1. Size: Custom sizes may have longer delivery times.
  2. Protection: Look for functions like overvoltage, overload, and overheating protection.
  3. Control: Check for options like analog, digital, or switch control.
  4. Special Features: Consider features such as power factor correction and uninterruptible power supply.
switching power supply
Din Rail Switching Power Supply

Method 2: Choose the switching power supply based on the load

Scenario: When using a single set of output terminals, select the switching power supply based on usage conditions, required output voltage, and current.

For instance, when decorating your home with LED DC light strips (specifications: 6W/meter, 12V DC), follow these steps to choose the right switching power supply:

Calculate the total power needed for the entire light strip based on its length. In this case, assuming a 5-meter length, the total load power is 30W.

Choose a suitable switching power supply with the right power rating. Examples include S-35W-12V, MS-35W-12V, and LRS-35W-12V.

Method 3: Select the switching power supply from the brand

With numerous brands of switching power supplies available, they typically offer a long service life and see extensive use. However, choosing high-quality products is crucial to avoid issues. Most people prefer purchasing superior products, even though prices vary in the market. For non-professionals, it can be challenging to compare product advantages or disadvantages. Therefore, opting for well-known brand products is advisable such as Mean well, Omron, and ABB. At, you can find the different brands of switching power supply with high quality. All products from reputable and major manufacturers have undergone rigorous testing by authoritative bodies, ensuring better quality.

You can assess the quality of switching power supply products by reviewing their specifications, focusing on key points:

  1. Ripple: Typically, the ripple value should be less than 1%.
  2. Load regulation: Ensure the load regulation is within ±0.5%.
  3. Line regulation: The line regulation should be around ±1%.

Method 4: Select the switching power supply from the after-sales service

Switching power supplies typically offer several years of use, assuming you’ve purchased a reputable product that ensures a long service life. When making a purchase, it’s crucial to confirm the terms with the seller. Reputable sellers often offer unconditional replacements or repair assistance if any issues arise within the first month of use. It’s not advisable to choose non-branded or subpar products, as their quality may be problematic and even pose safety risks. Opt for products from merchants providing better after-sales service, as they usually offer stronger quality assurance.

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