All elements -- medical, industrial, power tools and home appliances and office equipment -- are well aware that electromagnetic interference (EMI) is largely inevitable. Experience has shown that suppressing EMI becomes more difficult as the frequency of switching mode converters increases. One suggestion is to reduce the need for suppression by designing components that generate less EMI. EMI, as engineers know it, is a phenomenon that causes an electronic device to be affected in some way by another device that is generating an electromagnetic field, namely stray energy in the radio frequency (RF) spectrum. At the system level, it is not easy to know how much interference the product will produce, or how local interference will affect its own subsystems. We can start by selecting components that produce low EMI, which can greatly help overcome the design challenges associated with low EMI becoming increasingly important when designing step-down converters.

To this end, Diodes Incorporated has developed a series of low EMI converters that allow engineers to design switching mode power supplies to reduce the amount of EMI generated by their designs. By using more efficient switchgear, it can also reduce heat and make it easier to develop more compact equipment. Low EMI buck converters are ideal for many applications, from network systems to power tools, laser printers, medical, industrial power supplies and 12V / 24V distributed power bus power supplies, as well as consumer electronics consumables requiring efficient converters for FPGAs, DSPs, and ASICs. Low EMI step-down converters are also suitable for home audio systems, game consoles, white and small appliances, flat screen TVs/monitors and set-top boxes.

The AP63200 is a 2A synchronous buck converter with input voltage range of 3.8V to 32V. It supports 5V, 12V and 24V power inputs, and can withstand surge input time of 40V and 400ms. Designed to provide first-class EMI performance and ultra-low static current. Ease of use through peak current mode control minimizes the number of external components. Also integrates high-end 125 m 68 m Ω Ω and low-end MOSFET, to support the effective step-down DC - DC conversion. The entire product line includes features that help minimize EMI when designing on-off mode PSU. These include a Frequency Spread Spectrum with a switching Frequency jitter of ± 6%, which reduces EMI by not allowing the transmitted energy to stay at any one Frequency for any appreciable time. They also have a proprietary gate driver solution that can resist switch node ringing without sacrificing MOSFET on-off and off-time, which also eliminates the high-frequency radiated EMI noise caused by MOSFET switches.

Today's social consensus, for the average person, if the conversion efficiency of home appliances is high, in the long run over a long period of time, the saving of electricity is quite considerable. Therefore, the power consumption voltage of IC itself is also a key point to enhance electricity consumption. The AP6320X series features ultra-low 22uA static current, up to 80% efficiency at 1mA and 88% efficiency at 5mA, adjustable low voltage locking point (UVLO) for added design flexibility, and?? Optimized Pin Out to minimize AC switching current loops to minimize system noise. In particular, the AP63203 and AP63205 units are fixed-output step-down converters that are best designed for reducing EMI, as a simpler PCB layout design reduces the number of external components required and ensures that the current loop on the PCB is shorter, resulting in less likelihood of EMI problems. The fixed 3.3V and 5V output options further reduce the number of external components. Obviously, by understanding the root cause, the best way to reduce the EMI of the switching power supply can be designed.

Medical Display Power Supply Scheme Based on Diodes AP63200 Low EMI 24V DC Conversion (Fig. 1)