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What is a switch mode power supply and why choose Finder?


What is meant by switch mode power supply?

A switch mode power supply (SMPS) is a popular and sometimes imperative device. It’s needed to take an unsuitable voltage and convert it to a suitable voltage required for the application. In many cases, the unsuitable (e.g., higher) voltage is the mains (230V 50Hz AC in the UK)  and the lower voltage is 12 or 24V DC.

The device helps:

  • provide Isolation – keeping the low voltage equipment separated from the higher mains voltage.
  • regulate the output voltage, keeping it constant even if the mains supply voltage goes up or down.
  • regulate the output current, helping prevent short circuits from damaging the power supply and other equipment.

What is the difference between linear and switch mode power supply?

Switch Mode PSU

A switch mode PSU uses high-frequency switching (40kHz – 40 thousand or more typically) operations a second to transfer power through the transformer. The high-frequency switching means the same amount of power can be delivered from a much smaller, lighter power supply. This on-off switching and the use of high-performance ferrite transformers also makes the switch mode PSU far more efficient than a traditional linear power supply.

Linear Power Supply

At the heart of a traditional linear power supply is a laminated iron transformer. This transformer operates at mains frequency (50 Hz) and converts the mains sine wave to a low voltage sine wave (this is the ‘Linear’ part). The low frequency of operation means more power must be transferred per mains cycle for any required output. This means that the transformer must be quite large and heavy. The laminated iron core also suffers far more losses in operation which as well as being inefficient generates unwanted heat.


Why would a SMPS be used?

A switch mode power supply is used to supply power to low voltage equipment for both industrial and domestic applications. More and more modern equipment require a low voltage supply, even if it is ultimately controlling mains or high voltages. A power supply simplifies the task of maintaining safety isolation in wet or polluted environments.

So, in many circumstances, it makes perfect sense to use extra low voltage relays and timers to do all the control, even if what’s being controlled runs on mains voltage. An example here might be the pumping, dosing, heating of a swimming pool.

Why choose Finder’s switch mode power supplies?


Each power supply is subject to a series of rigorous tests before leaving the factory. This is the way we guarantee that you can fully trust our products. Finder’s power supplies are protected against overloading and short-circuiting.


Finder’s power supplies are built to provide top-of-the-range performance in terms of efficiency and low energy use.


The output of the power supply can be adjusted to meet the requirements of the application.

The high-performance switch mode power supplies of the 78 Series are suitable for a wide range of applications, thanks to adjustable output voltage, overvoltage and short circuit protection.

Finder’s 78 Series switch mode power supplies are ideal for LED strips, video door entry systems and home automation systems. They stand out for their high standards of workmanship, are 100% made in Italy, and feature an array of functions including: the front panel replaceable fuse for input protection, a compact design, and a very low energy use when in stand-by mode.

The Types 78.51 and 78.61 models also have characteristics specifically intended for battery charging. They are ideal for supplying emergency lights, CCTV systems and access control systems.

Finder’s 78 Series switch mode power supplies

Finder’s 78 Series is a range of switchmode power supplies with low dimensions for control cabinets and other industrial applications.

Other features include (according to Type):

  • Output powers 12, 36, 50, 60, 120 or 130 W
  • Input (110 … 240) V AC or 220 V DC
  • Class B according to EN 55022
  • Replaceable input protection fuse plus spare
  • Varistor for protection against overvoltages
  • Width 17.5, 40 or 70 mm
  • A KNX power supply with rated output 30V DC 640mA is also available.

Click here for the datasheet.

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