Although RECOM DC/DC converters are designed to have low levels of output noise, a fully-featured EMC filter is not built in to every converter for both cost and size restrictions. The circuit designer is free to decide if an EMI filter is even necessary at component level and, if so, which class (A or B) of filtering is needed, depending on the application and budget. Filter networks can also reduce susceptibility to external EMI in the form of surges, ESD and transients.
Differential mode noise from DC line to return is usually attenuated by a series inductor or ‘choke’ which blocks high frequencies, combined with a capacitor which shunts the noise to ground or a return connection. Such inductor-capacitor (LC) filters can be fitted to both the inputs and outputs of DC/DC converters to reduce conducted emissions to the required level.
The component values can be calculated for the required level of attenuation, but parts from different sources can vary significantly in performance for the same nominal specifications. For example, the inductance varies with frequency and applied current at different rates for different models and the self-resonance, above which the inductor starts to look like a capacitor and the impedance starts to drop and noise attenuation decreases, is different depending on the manufacturer. This makes choosing the optimal LC components a lottery, with a poor choice affecting conducted and radiated EMI adversely.
To provide consistent and predictable results, RECOM has designed a range of low-cost inductors which have been optimized for use with RECOM DC/DC converters and verified for EMC performance by conducted and radiated EMI measurements in our in-house EMC test facility.
The range of inductors available in convenient SMD formats includes nominal values from 3.97µH to 100µH and with current ratings from 0.63A to 1.89A. Which inductors are best suited for which DC/DC converters are specified in our DC/DC converter data sheets along with other suggested EMI suppression components to make “First-time Pass” for EMC testing a reality.
RECOM converters and matching filter inductors provide a one-stop solution to EMI reduction, saving design effort, money and enabling faster time-to-market.
Differential mode noise from DC line to return is usually attenuated by a series inductor or ‘choke’ which blocks high frequencies, combined with a capacitor which shunts the noise to ground or a return connection. Such inductor-capacitor (LC) filters can be fitted to both the inputs and outputs of DC/DC converters to reduce conducted emissions to the required level.
The component values can be calculated for the required level of attenuation, but parts from different sources can vary significantly in performance for the same nominal specifications. For example, the inductance varies with frequency and applied current at different rates for different models and the self-resonance, above which the inductor starts to look like a capacitor and the impedance starts to drop and noise attenuation decreases, is different depending on the manufacturer. This makes choosing the optimal LC components a lottery, with a poor choice affecting conducted and radiated EMI adversely.
To provide consistent and predictable results, RECOM has designed a range of low-cost inductors which have been optimized for use with RECOM DC/DC converters and verified for EMC performance by conducted and radiated EMI measurements in our in-house EMC test facility.
The range of inductors available in convenient SMD formats includes nominal values from 3.97µH to 100µH and with current ratings from 0.63A to 1.89A. Which inductors are best suited for which DC/DC converters are specified in our DC/DC converter data sheets along with other suggested EMI suppression components to make “First-time Pass” for EMC testing a reality.
RECOM converters and matching filter inductors provide a one-stop solution to EMI reduction, saving design effort, money and enabling faster time-to-market.
