Eliminating noise or EMI can present a serious challenge when designing power supplies for electronic circuit boards. While noise reduction may not be a critical issue for linear power supply design, the inherent noise created by switching devices is of paramount concern when designing switching power supply circuits. Fortunately, this problem can be sufficiently mitigated—as described in the following switching power supply FAQs.
Just the Facts
What is a switching power supply?
A switching power supply is one of the two major types of power supply design utilized in electronics products. These power supplies are characterized by the use of precise switching that allows for designs to accommodate DC to DC, DC to AC, AC to DC and frequency conversions.
What is the difference between a switching power supply and a SMPS?
Research and development of power supplies that used “switching” to improve efficiency over conventional linear power supplies dates back to the 1950s with early devices that utilized vacuum tubes; however, the first patented use of the term, “switch-mode power supply,” was in 1976 by Howard Scott of RCA. Today, the terms, “switching power supply” and “switch-mode power supply” (SMPS), are generally used synonymously.
What types of switching components are used in switching power supplies?
In contrast to linear power supplies that typically employ diodes, SMPSs utilize precise switching to control duty cycle operation. Therefore, transistors that allow for enhanced control are most often employed.
Where are switching power supplies used?
Switching power supplies are primarily used in digital systems such as telecommunication devices, computing equipment, audio equipment, mobile phone chargers, medical test devices, arc welding equipment and automotive chargers.
What is a switching power supply adapter?
Power supplies are essentially converters. Typically, they convert one or more parameters from supplied power to the parameter type and level required by a load or connected circuit. A power supply adapter allows for the utilization of a power supply whose output was not specifically designed for the utilized input. Power supply designs may consist of the conversion circuitry only or may consist of conversion and adapter circuitry on the same board.
What are the types of switching power supply design?
The most common design types for switching power supplies are:
- Half Bridge
- Full Bridge
What are the most significant challenges when designing switching power supply boards?
Precise control of the switching action is a critical design requirement for switching power supplies. However, this switching action creates high frequency and noise. For PCBAs, lower RF frequencies are not a significant concern. Yet, for high-speed board design, special considerations, such as trace lengths and terminations, board impedance, and material type, must be addressed.
How do you reduce the noise in switching power supply circuits?
The complete elimination of noise or EMI from your power supply design is not practically achievable. Instead, the objective is to reduce noise as much as possible to obtain electromagnetic compatibility. At this point, your power supply board is not only a good neighbor to nearby electronic devices, but also the amount of EMI on your board does not negatively impact functionality. Some of the best practices for reducing noise on PCBAs include the following: employing impedance matching, limiting trace lengths, and observing good creepage and clearance distances. Additionally, one of the most important considerations that also impacts your performance objectives for connected loads is filtering.
What are the most important factors for designing and building switching power supply PCBAs?
SMPSs are used across a wide range of applications. However, the following factors typically require special attention when developing switching power supply boards.
Optimizing Switching Power Supply PCBA Development
|Tempo’s Software-Driven Smart Factory Delivers the Industry’s Leading Custom Turnkey PCBA Manufacturing Services
By employing the items listed above, you can achieve a switching power supply design that will meet your performance objectives, address the most significant challenges and facilitate optimal development. At Tempo Automation, the industry leader in full turnkey PCBA manufacturing, we will work with you throughout development to ensure that your boards are built quickly and to the highest quality standards.
And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.