SMPS Buying Guide


What is SMPS?

SMPS or Switched-Mode Power Supply is a device that uses switching regulator as a medium to control and stabilize the output voltage by switching the load current on and off. These power supplies offer efficient power conversion and reduce the overall power losses. Basically it’s a device in which energy conversion and regulation is done using mix of inductors, capacitors and other electronics unit units that are continuously switching “on” and “off” at high frequency.

These supplies have higher efficiencies that is why they are widely used in a variety of electronic equipment which include computers and other sensitive equipment requiring stable and efficient power supply. They are widely used in electronics because of their advantages offered in terms of size, weight, cost, efficiency and overall performance.

Why is there a need of SMPS?

The power drawn from the power units cannot be directly supplied to the ICs and other electronic components that are used in electronic devices in automated office and factory equipment without destroying the components due to the very high voltage of commercial AC power. Therefore there is a need of devices which can transform and regulate these high power to small scale. These devices are known as power supplies or regulated DC power supplies. They are required to convert commercial AC power into regulated DC power which can drive ICs and other electronic components.


Picture representing Switched Mode Power Supply

Working of SMPS

Switch-mode power supply converts AC power into high-frequency DC power using the high-speed switching of semiconductors. Switch-mode power supplies are so compact, light, and efficient that they are used as power supplies in most electronic devices. The basic concept behind a switch mode power supply or SMPS is the fact that the regulation is done with the help of switching regulator. Voltage regulation is achieved by varying the ratio of on-off time.


Block diagram representing working of Smps

Circuit Diagram representing the working of Smps

Switch mode power supply terminology

Switch mode power supply technology may be referred to by a number of similar terms. While they all look at the same basic technology, they refer to different elements of the overall technology:

Common Terminology are as follows :-

Switch mode power supply : The term switch mode power supply is generally used where they can be connected to the mains or any other external supply so that power can be  generated in the required form.

Switch mode regulator :   This typically refers to the component which provides regulation. A switch mode regulator will be a part or a sub-unit of the overall switch mode power supply.

Switch mode regulator controller :   Most of the switch mode regulator integrated circuits do not contain switching element. They are required because external series switching element would be able to handle the higher current and voltage level as well as the resultant power dissipation more effectively and efficiently.


Classification of Smps according to the type of input and output voltages which are as follows  :-

  • AC to DC
  • DC to DC
  • DC to AC
  • AC to AC

Classification of Smps on the basis of working :-

  • C. to D.C. Converter
  • Forward Converter:
  • Flyback Converter:
  • Self-Oscillating Flyback Converter

DC-DC converter

The power received from AC main is rectified and filtered as high voltage DC. It is then switched at a high rate of speed and fed to the primary side of the step-down transformer. The step-down transformer is small in size thereby relieves  the size and weight problems. The filtered and rectified output at the secondary side of the transformer is now sent to rectifiers, filters and regulators.. A part of this power output is sent back to the switch to control the output voltage.



Block diagram of DC-DC converter

Forward converter

A forward converter is a type of switching mode power supply that transfers the energy from the primary to secondary part of transformer while the switching element is “on,” which is the opposite of a flyback converter. The output voltage is determined by the input voltage which depends on the transformer’s turn ratio and the duty cycle. The diode carries the current during the OFF period of the transistor and therefore energy flows to the load during both the periods. The choke stores energy during the ON period and also passes some energy into the output load. The forward converter is also known as a DC-DC buck converter.


Block diagram representing Forward converter

Flyback converter

The flyback converter is derived from buck-boost topology with the inductor split to form a transformer. This is done so that the voltage ratios are multiplied with an additional advantage of isolation. Here the magnetic field of the inductor stores energy during the ON period of the switch. The transformer provides a voltage ratio from input to output and the advantage of galvanic isolation.  The energy is then passed into the output voltage circuit when the switch is in the open state. The duty cycle determines the output voltage. The flyback converter is used in both AC-DC and DC-DC conversion with galvanic isolation between the input and any output sides.


Circuit diagram representing Flyback converter

Diagram representing Self-Oscillating Flyback Converter

Self-Oscillating Flyback Converter

This is a type of Smps where flyback converter does not require a separate oscillator but the switching of primary current is achieved by a built-in self-oscillatory action. During the conduction time of the switching transistor, the current through the transformer primary starts ramping up linearly with the slope equal to Vin/Lp.  The voltage induced in the secondary winding and the feedback winding make the fast recovery rectifier reverse biased and hold the conducting transistor ON. When the primary current reaches a peak value Ip, where the core begins to saturate, the current tends to rise very sharply. This sharp rise in current cannot be supported by the fixed base drive provided by the feedback winding as a result, the switching begins to come out of saturation.

Things to know before selection of a Power Supply

  • Input Supply
  • Output Supply
  • Mounting methods
  • Safety standards


Advantages Of SMPS

  • High efficiency
  • Compact and light
  • Flexible technology
  • Compact, and light.
  • A wide input voltage range.

Brands Industrybuying are offering


OMRON provides various types of power Supplies, like the type mounted to DIN rail or the type built into equipment. OMRON also brings to you  the S8VS which provides alert notification in case of  replacement timing, and a buffer block that handles intermittent  power interruptions and other highly trusted power supplies at the same time.


MEANWELL has proven to meet different power supply requirements of numerous  industries with a comprehensive line of product, flexibility of production, planned stock, and a global channel. It has an established track record of providing the best cost/ performance ratio of standard power supplies (PQC) and services (DSR) AC / DC power supply, LED driver, AC / DC battery chargers, DC / DC converters and DC / AC inverter.

Shop for quality SMPS only at

As the market is flooded with different alternatives with respect to e-commerce, Industrybuying offers one point solution. At Industrybuying you can look for different brands and filter the right product that matches your requirements. You can get to choose from a wide variety of SMPS like single input single output SMPS, double input single output SMPS, double input double output SMPS, double input triple output SMPS, double input four output SMPS etc and a lot of other industrial automation tools. We will provide you the best of the product at best of the prices at your doorstep. You can buy huge quantities  without any limits, and we are sure to provide you the best rates for quantities purchased in bulk.

Industrybuying offers you the best of the costs and quality industrial automation items in flexible payment modes like Cash on Delivery (COD), Net Banking, Debit and Credit Card Payment, Mobile Wallets (Paytm, Mobikwik), Cheques and NEFT. We are the ones who provides easy solutions to our B2B customers. So, experience  the ease of shopping online for better, faster, cheaper and get a one point solution to all your  industrial requirements anywhere and anytime that too within a specific time-frame with Industrybuying.

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