Archive: Sep 2020

Switch Mode Power Supply Transformers FAQ

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MPS Industries is a U.S.-based magnetic components manufacturer specializing in the design of custom transformers, inductors, common mode chokes, current sensors and many other custom magnetics. 

Switch mode power supply (SMPS) transformers use different switching topologies, transferring the required power from input to output in the electronic systems. Here, we have answered some of the most frequently asked questions regarding this unique and efficient transformer technology. 

How Does a Switch Mode Power Transformer Work?

Switch mode transformers are used within switch mode power supplies to provide power to a range of commercial and industrial electronic systems. These transformers are highly efficient at converting alternating current (AC) main power to direct current (DC) output voltage. The AC main power is filtered through a capacitor when power is switched on, allowing it to be converted from AC voltage with rectifiers to unregulated DC voltage. Using a regulator, the switch mode transformer then converts this unregulated DC voltage into regulated DC output voltage at different voltage levels.

What Are the Common Applications of a Switch Mode Power Transformer?

Most modern electronic applications rely on power supplies that can very efficiently convert low-frequency main AC power to the well-regulated DC voltage required by the circuit. SMPS transformers are often preferred due to their ability to provide a tightly regulated output voltage. A few specific applications of these transformers include:

  • Medical devices
  • Communication devices
  • Commercial power supplies
  • Security systems
  • Support supplies for PLCs
  • Audiovisual products

What Makes Switch Mode Power Transformers Different From Other Transformers?

By internally switching the transistor between an on and off state, switch mode transformers can minimize a power supply’s energy dissipation, resulting in a higher efficiency with less heat produced when compared with those transformers used in linear power supplies. Linear power supplies typically require large power transformers to step up or down voltage before it can be applied to the regulator circuit. In general, linear power transformers tend to be bulkier and substantially less efficient than switch mode power transformers which are smaller and compact given their higher operating frequency.

What Are the Different Switch Mode Power Transformer Topologies?

The topology of a switch mode power transformer refers to its specific circuit configuration. A few of the basic topologies used in power design include:

  • Flyback: The flyback is an isolated topology in which energy accumulated and stored during the “on” state of the switch is transferred to the output during the “off” state. This is one of the simplest and lowest-cost isolated topologies and is best suited for lower-power applications.
  • Forward converter: Rather than storing energy in the core, forward converters directly transfer energy between the primary secondary sides. Like flybacks, forward converters are best suited for lower power applications.
  • Push-pull: The push-pull topology is basically a forward converter with a dual-drive winding, making it much more efficient at utilizing the core of the transformer when compared with flybacks or simple forward converters.
  • Half-bridge: The half-bridge is a type of forward converter topology. Half-bridge topologies are designed so that the load current can flow in two directions.
  • Full-bridge: The full-bridge topology is essentially two half bridges. It has similar switch ratings as the half-bridge but provides twice the output power.
  • Gate-drive: Gate-drive transformers are used in switch mode power supplies to control circuit timing through the delivery of electrical pulses.

What Are the Advantages of Using a Switch Mode Power Transformer?

When it comes to modern electronic applications, SMPS transformers offer several clear advantages over alternative methods of converting DC power. These include:

  • Higher efficiency: The regulator’s switching action allows it to be in either on or off mode. Because of this, energy dissipation is minimal and power can be used extremely efficiently.
  • Lighter weight: Compared with linear transformers, switch mode power transformers are much smaller and lighter. This is possible due to their high operating frequency and highly efficient power usage.
  • Greater flexibility: Unlike linear transformers, switch mode power transformers are capable of creating high conversions in both voltage-boosting and voltage step-down applications.

What Are the Design Considerations for an SMPS Transformer? 

When designing an SMPS transformer, it is important to consider the following parameters:

  • Input and output voltage
  • Output power or current
  • Switching frequency
  • Operating mode
  • Maximum duty cycle of the IC
  • Safety standards
  • Temperature requirements
  • Size requirements

Three primary design considerations are core shape, type, and size, all of which should be chosen based on your application’s power requirements, switching topology, and anticipated switching frequency. Certain core materials have properties that make them better suited for higher-frequency applications. It is also important to make sure the components and wiring do not go above their rated temperatures, as this will affect overall circuit reliability. Industry-specific safety requirements should also be kept in mind to ensure the compliance of your design with relevant regulatory standards.

Are There Any Transformer Design Considerations for IC Chips?

Generally, our customers’ design engineers will start with an integrated circuit/IC chip, which typically has some kind of reference design with suggestions on transformers and other components to be used with the chip. They can either start with the reference design and modify it to suit their application, or they might opt for their own custom design using the chip.  

We currently work with several IC companies and are on some reference designs already. However, we can definitely work with the customer to supply transformers per their reference designs or create a custom design to meet their application needs.

Contact MPS Industries for SMPS Transformer Guidance

At MPS Industries, our electrical engineering team regularly provides magnetic component guidance and design assistance for even the most complex industrial systems. Whether you require minor modifications to a standard product or a complete custom design from scratch, our engineers possess the insight and resources to meet your exact specifications. We uphold a strong quality management system to make sure that every product we deliver meets or exceeds customer expectations and complies with all relevant industry standards.

To learn more about SMPS transformers at MPS, check out the links below: 

Contact us today about any of our magnetic component solutions or services!