At a recent press conference, Texas Instruments (TI) spoke of Low Electromagnetic Interference (EMI) as a major trend in energy management, as it reduces interference of power supplies with other system components and simplifies design and engineering processes for engineers. Cecilia Smith of Transparency International, Vice President and General Manager of Multichannel Direct Current / DC / DC, and Ganesh Srinivasan, Product Line Manager for Wide VIN Buck Switch Regulator, spoke about how to meet EMI industry standards and reduce emissions and radiation. For engineers designing power systems for automotive and industrial applications. Increased electronic content as well as increased conversion speeds for DC-to-DC solutions pose new challenges for power supply designers. The development of new enclosures, new semiconductor innovations, and new modeling techniques for energy management provide many tools for reducing EMI. It is of the utmost importance to reduce the size of the design of the Low EMI power supply, which reduces the number of components and the cost of the negative filter. This can also help reduce design time and complexity. Designers working on low EMI applications usually face two major challenges: the need to reduce EMI for their designs, and at the same time, reduce the size of the power supply solution. In a system that requires EMC, the components that act as electromagnetic sources are designed in a way that reduces transmission emissions. Electromagnetism is the electromagnetic energy produced as an unwanted by-product of exchanging currents and voltages. Conventional methods to reduce electromagnetic interference include the use of passive and active filters (Fig.1). Passive filters tend to be bulky, resulting in great power supply solutions. Passive filtering uses inductors and capacitors to filter, while active filtering uses an analog circuit to generate counter-phase current. Active EMI Filter (AEF) aims to reduce the size and therefore cost of a power supply solution while providing EMI performance that meets industry requirements. Two important examples are shown in Figure 2; The active part uses an operational amplifier circuit (op-amp) as a capacitive multiplier to replace the filter capacitor (CF) in the passive design. Impedances use relatively low capacitance values with small component footprints. Figure 1: Example of EMIs in a switching mode power source (Source: TI) Figure 2: Conventional Passive Filter (a) and Active Filter (B) Circuit Applications (Source: TI) Figure 3 Comparison of a Printed Circuit Board (PCB)) Two phase layout The passive and active filter is shown in Fig. 1. The effect of inductor is reduced from 5 x 5 mm to 4 x 4 mm. In addition, the two 1210 capacitors were replaced by several small constant value 0402 components for detection, injection, and AEF compensation. The built-in active EMI filter reduces the effect of the solution by approximately 50%, while the volume decreases by more than 75%. Figure 3: PCB layout size comparison between passive (a) and active (b) filter designs (source: TI) DC / DC buck controller with integrated active EMI filter During the briefing, speakers highlighted how TI DC / DC controllers are Buck with integrated active EMI filter, LM25149-Q1 and LM25149, can detect noise or voltage ripple when the device is input and feed out of phase signal with this noise to cancel, thus achieving improvement in EMI performance. This device incorporates another revolutionary technology, dual random spread spectrum [DRSS]Hence, between active EMI filter and DRSS technologies, this device can help power supply designers achieve improvement of up to 55 dB per micV by means of our previous pseudo-random innovations to further enhance the technology and improve the performance of our devices, ”TI said. Reducing filter size. ”Reducing filter size is a huge benefit, especially with the increase in electronics in the automotive and industrial sectors. TI said:“ In another of our flagship low EMI devices, the LMQ61460, we have incorporated bypass capacitors that help reduce parasitic inductance to the switch loop and improve EMI performance. ”“ The other unique thing along with the built-in bypass capacitors is our HotRod package with highly optimized pinout, so that engineers can get the best EMI performance out of the device. ”Reducing electromagnetic breakage in the power supply is an increasing design challenge, especially With the increase in electronic content in the advanced driver assistance systems, the infotainment system, and vehicle packages.The traditional way to ensure that a design meets the established EMI specification involves increasing the size of the passive EMI filter. External, which in turn increases the total volume of the energy solution. By incorporating active EMI filtering into the LM25149-Q1 and LM25149 buck controllers, TI enabled engineers to meet EMI standards while increasing the power density of their design (Fig.4). Figure 4: Typical Application Diagram for LM25149-Q1 (Source: TI) Maintaining a low EMI in a power supply and achieving a small solution is usually at odds in switching power supply designs. The LM25149-Q1 and LM25149 buck controllers allow engineers to meet stringent EMI standards and reduce solution volume by reducing the area and size of a passive EMI filter. Compared to competing solutions, engineers can achieve maximum savings of about 50% in area and over 75% in front EMI filter size of 440 kHz. By reducing the filtering load on passive elements, the built-in AEF reduces its volume, scale and cost, enabling engineers to achieve the smallest design possible for low power EMI modules. This article was originally published on its sister site, Power Electronics News. .
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