The demand for capabilities requiring complex and sophisticated technology is a trend that continues to grow exponentially, in almost every application from military use to industrial equipment, manufacturing and more. And with the ever-growing demand for highly developed electronic equipment across a variety of fields, the corresponding development of high-density DC-DC converters has been essential to designers in delivering mission critical electronics.
While they offer a host of advantages, these converters also have a significant bearing on a wide range of factors, including cost, performance, reliability. And in order to optimize their use, it is vital for designers to understand the role of electrical emissions when designing mobile-based ground equipment.
This blog post discusses the impact of electrical emissions, and takes a look at what considerations need to be taken into account during the design process.
As DC-DC converters are intrinsically electronically noisy, designers can incorporate noise attenuation into devices by using filter components. By using components with high frequency impedance, this can help to reduce the impact of electromagnetic interference, particularly in the converter’s switching frequency range.
But the performance of filters can be affected by a variety of different factors, such as filter technique, the physical location of components, and temperature characteristics, as well as ESR and ESL. One of the biggest issues for designers to counter is not base switching frequency as might be expected, but the high transitions across dv/dt and di/dt, which are the primary causes of electromagnetic interference, and can lead to both conducted and radiated noise.
Dealing with parasitic capacitance
One of the problems that can arise as frequencies reach higher rates is parasitic capacitance around switching components and diodes. This can arise due to the fact that smaller distributed capacitances have lower impedances at higher frequencies. But by taking the positioning of components into consideration, the effect of parasitic capacitance may be able to be reduced by designers. For example, by introducing a greater distance between the chassis and the tab of the device, its impact may be lowered.
But while changing positioning can reduce parasitic capacitance, designers will also need to reach a compromise in order to allow sufficient reduction as well as enabling thermal conductivity – increasing the distance might reduce capacitance, while a thinner space serves as a more effective medium for thermal conduction.
While electromagnetic interference might not be completely eliminated, there are other alternatives for power designers. Shielding a converter on all sides and adding slew rates to transients can also help to decrease the di/dt and dv/dt rates, and other internal modifications might help converters to change the operating frequencies, and improve communication with the system. By changing radio transmit and receive frequencies, for example, a converter can be commanded to change the switching frequency on demand, to another such that the base switching frequency is not directly related to the desired transmit or receive frequencies.
The benefits of DC-DC converters are extensive, improving output voltage, battery management and efficiency, and helping to reduce size, and demand for these devices only continues to grow. As they do, the challenges that come with the territory need to be tackled, in creative and practical ways.
What are your thoughts about how to manage the impact of electrical emissions? Leave a comment below.