Brief introduction

Application of most power source must reduce electromagnetism to disturb (EMI) in order to satisfy relevant requirement, systematic design personnel must try all sorts of methods to decrease conduct and radiation blasts off.

 

Electromagnetism compatibility (of EMC) standard add up to compasses sex (for example, be aimed at the CISPR 32 of multimedia equipment, the CISPR 25 that is aimed at car application) it is a very main task, with the product development cost is mixed appear on the market time be closely bound up.

 

To DC/DC converter, although use switch,faster power source parts of an apparatus can promote switch frequency narrow measure, but the switch voltage that appears during switch is changed and voltaic changeover rate (Dv/dt and Di/dt) promote somewhat, cause EMI aggravate normally, cause whole system occurrence problem.

 

For example, nitrogen changes gallium (the switch speed of parts of an apparatus of GaN) power source is splitting, bring about the EMI below high frequency condition to increase 10dB. EMI filter is the component with indispensable system of electric power electron, occupy in total volume and gross weight respect than opposite bigger. Accordingly, the EMI that must pay close attention to a system very much falls a confusion of voices and restrain, want to satisfy EMC standard not only, still need to reduce solution cost and increase systematic power density.

 

The article is the first part of EMI series article, reviewed relative standard and measure a technology, conducted emission of main side overweight. Watch 1 listed the commonly used abbreviate that concerns with EMI and nomenclature.

 

EMC superintends a standard

EMC points to a system or embedded yuan of parts of an apparatus move by the requirement in its electromagnetism environment, won’t generate the capacity that the electromagnetism that exceeds tolerance disturbs to any equipment in the environment. This kind of interference may cause serious consequence, because all sorts of home and this international are superintended,EMC provision all was established in the standard.

 

Inside European Union area, the power source product that communication market sells uses level of product of EN 55022/CISPR 22 normally for years, be in thereby conduct and radiation launchs two respects to satisfy add up to compasses sex requirement, the power source product that this standard consults besides the European Union uses CE accordance to state (DoC) , of 2014/30/EU of instruction of EMC of contented European Union add up to compasses sex.

 

The product that designs in the light of North America market accords with FCC the bounds of the 15th part is worth. Standard of general EMC of IEC 61000-6-3 and IEC 61000-6-4 applies to light industry and industrial environment respectively.

 

However, in radiation respect, standard of EN 55032 product already replaced EN 55022 (ITE) , EN 55013 (broadcast receiver and relevant equipment) with EN 55103-1 (phonic video equipment) . This one new standard makes the unified radiate standard that accords with EMC instruction formally. More specifically, the test has according to EN 55022 before and go to in the carry after March 2, 2017 all products of the European Union, must accord with the requirement of EN 55032.

 

Replace by EN 55032 as cancel of EN 55022 standard, power source manufacturer and supplier need replace its DoC letter according to new standard, use label of CE attestation badge legally thereby. Graph 1 showed come in 150kHz inside the applicable frequency limits of 30MHz, use exact peak value (QP) and average (the EN 55022/32 A of the conducted emission that AVG) signal detector undertakes kind with B kind be restricted to be worth.

 

 

Graph 1: The EN 55022 A that uses detector of exact peak value and average kind with B kind conducted emission is restricted to be worth.

 

To car terminal unit, prospective EMC adds up to the main impetus of compasses sex come from the own car that backs at passing the communication between car undoubtedly. In the light of “ board the CISPR 25 standard that holds receiver to protect ” already set strict restriction in the light of conducted emission, in FM frequency band (76MHz comes 108MHz) limitation particularly strict.

 

From superintendency angle character, code of UNECE 10 name replaced the 2004/104/EC of car EMC instruction of the European Union in November 2014, ask manufacturer must obtain all car, electron among them yuan parts of an apparatus (ESA) , yuan parts of an apparatus and the type attestation with independent unit technology.

 

The conducted emission that CISPR 25 checks all comes in 150kHz undertake metrical inside the specific frequency band of 108MHz frequency limits. Specific and character, adjust frequency limits distributings to serve frequency band in AM broadcast, FM broadcast and shift between, if pursue,2 medium image and form place are shown. Graph 2 return scale CISPR 25 5 kind (the requirement of the most severe exacting) relevant be restricted to be worth image. Although the belt between frequency band is unoccupied place,allow taller noise aiguille, but car manufacturer may ask to choose to expand according to its specific in-house EMC these frequency limits. These requirements are based on international IEC standard normally, a few parameter that change disparate test only or are restricted to be worth, its core content keeps changeless.

 

 

Graph 2: CISPR 25 5 kind conducted emission is restricted to be worth.

 

Be restricted to be worth bounds challenge to answer CISPR 25, especially respect of FM frequency band, ask an attention, 50Ω measures the noise electric current of the 18dBμV correspondence that resistor produces to be 159nA only.

 

Measure conduct EMI

LISN measures the conducted emission that EUT produces. It is to insert EMI source and power source between the interface of measurement point, ensure EMI measures an outcome but repeatability and comparable sex. The functional equivalent circuit that the graph shows the standard 50μH LISN that for the basis CISPR 16-1-2 [12] or ANSI C63.4 standard define 3 times (be not whole principle to pursue) .

 

LISN offers:

•In give frequency range inside, the impedance of stable signal source that produces course calibration.

•Inside this frequency limits, mix EUT measure equipment and segregation of input power source.

•With measure equipment to establish safe and applicable link.

•Measure the total noise level of two circuitry alone, graph 3 in express with L and N.

 

 

Graph 3: The conducted emission that use V LISN undertakes is measured.

 

In short, impedance of use signal source is foregone define test program to be able to be obtained beforehand but repeatability result. Note: LISN may include circuit of one or more independent LISN.

 

The essence of LISN is Pi filter network. Feel through low electrify – capacitance (LC) filter, EUT and L of input power supply cord and N are linked together, if pursue,3 are shown. LISN inductance value is based on in product ideal installation condition falls, the anticipation of power supply cord inductance.

 

CISPR 16 and ANSI C63.4 appointed inductance of a 50μH for LISN, the inductance conform to of 50 meters distribution wiring system is made an appointment with in this value and telegraphic equipment. Contrary, CISPR 25 appoints 5μH LISN, answer relatively with the approximate inductance of car wiring harness.

 

LISN offers the impedance of specific definition for noise transmit. LISN manufacturer offers calibration curve normally, the directive is specific measure frequency range inside nominal impedance. According to CISPR 16-1-2, permission tolerance is the amplitude of ±20% and ±11.5° is phasic.

 

Measure to using what EMI receiver or spectrum analyzer undertake, noise signal can be passed connect filter network high (if the graph is shown 3 times) obtain, the coupling capacitance of this network is 0.1μF, discharge resistor is 1kΩ , the termination resistance that measures port is 50Ω . Graph 4 showed come in 150kHz the frequency limits of 30MHz, (50μH + 5Ω) | | 50ΩThe imitate impedance of LISN pursues.

 

 

Graph 4: In the 150kHz adjustment to 30MHz inside frequency limits, measure the 50Ω that port is in, 50μH LISN is nominal impedance is characteristic.

 

The CISPR 25 that is aimed at car application tests device

Graph the 5 conducted emission that showed CISPR 25 is recommended test device. This standard was defined wait for the processing that surveys a system means and measure plan and equipment. According to CISPR 25 standard, LISN herein is appointed for AN. When line of car power circumfluence exceeds 200mm, EUT long-range ground connection, need two AN: Both is used at line of positive electricity source and power circumfluence line respectively. Contrary, if car power answers streamline not to exceed 200mm, criterion ground connection of EUT this locality, need to use an AN Yu Zheng power source only.

 

AN direct installation is over plane of standard ground contact, AN crust and ground connection plane are linked together. Circumfluence line returns power source to be linked together with the ground connection plane between power source and AN. Connect EMI receiver those who receive corresponding AN to measure port to be able to ensure the success measures the conducted emission on every power supply cord. Meanwhile, the measurement of the AN that inserts another power supply cord port termination 50Ω is laden.

 

 

Graph 5: CISPR 25 conducts EMI to test program (voltage law) overview.

 

Graph 6 showed the lab of CISPR 25 conducted emission that is used at combining compasses test beforehand. LISN is the blue casing on the right side of, car batteries is located in lithium ion ever since, DUT is located in on left insulating material. To be in voltage of specific power source falls (for example 13.5V) have a test, use alterable voltage source from the experiment the ministry outdoor passes clapboard feed. The result passes respective LISN online Lu Duan (hot loop) and return end (ground connection) get.

 

 

Graph 6: The CISPR 25 that uses LISN of two sheet pole and plane of Copper Foil ground connection conducts EMI to test device.

 

Graph the 7 CISPR 25 that showed a pattern conduct EMI scanning result, yellow and blue represent peak value and average measured value respectively. We can see DC/DC converter moves quietly, conducted emission is far be restricted to be worth under 5 strict kinds. This kind measures a technology to produce a change in 30MHz above, because the RBW of EMI receiver is adjusted from 9kHz,be 120kHz, the likelihood is brought about measure bottom of a confusion of voices to produce change.

 

Graph 7: Typical CISPR 25 conducts EMI to measure.

 

Summary

The electromagnetism energy that perhaps produces innocently of purpose all causes electromagnetism interference to other equipment. The electromagnetism energy that commercial product need produces in lieutenant general of normal moving procedure falls to lowermost level.

A lot of administrations of world each district all are conducted to allowing what end item arises and the grade of radiation EMI undertook formulary. Use applicable measurement OK and quantitative analysis projects the technology this kind, so that take proper step,accord with code add up to compasses sex.

 

EMC asks normally the issue closes in AC power supply cord (with line) the integral situation that measures a system, and DC/DC converter serves as child yuan parts of an apparatus, be restricted to be worth without specific EMC. However, the user can be carried out combine compasses sex test beforehand, whether does affirmatory EMI cause undesirable effect.