Transcript EMC and Audio Equipment

EMC and Audio Equipment EN55103-1 and EN55103-2
Mark Briggs, Elliott Labs ([email protected])
Outline of the presentation
The CE Mark
The EMC Directive
Professional Audio Equipment
EN55103-1 - Emissions Standard
EN55103-2 Immunity Standard
Designing to meet the standards
The CE Mark
• Required to sell products into Europe.
• Used to declare compliance to applicable
Directives.
(link to directives)
The EMC Directive
• EMC = Electromagnetic Compatibility.
• Two essential requirements:
– The product does not interfere with bona fide
users of the radio spectrum (Emissions)
– The product will operate when subjected to
interference from bona fide users of the radio
spectrum and to naturally occurring EM
phenomena (Immunity)
Demonstrating Compliance
• Declare compliance to the most applicable
standard
– Standards are listed in the Official Journal of the European Union
• If a standard does not exist or cannot be
applied, use a Technical Construction File
(TCF)
– A “Competent Body” reviews the manufacturers technical file which provides
justification to why the product meets the essential requirements. Typically the
Competent Body will base their interpretation of “essential requirements” on the
most applicable standard
Standards Route
– Manufacturer declares compliance by stating that the
product meets the requirements of the most applicable
standard(s) for emissions and immunity
– Nowhere does it state that you must test - the actual
wording is that you “... apply the standard(s)”
– Standards are listed in the Official Journal (OJ) of the
European Union (link)
– Product specific standards take precedence. There are
generic standards for products which do not have a
specific standard
What about new standards ?
– As standards get revised or as new product standards
are released, the OJ will list the “Date of cessation” for
the superseded standard
– Products sold after the cessation date must meet the
requirements of the new standard
– In the transition period either the new or old standard
may be used.
Technical Construction File
– Manufacturer prepares a technical file which provides justification
as to why the product meets the essential requirements.
– The file contains
•
•
•
•
product descriptions,
design details (with emphasis on EMC design techniques)
Results from any EMC tests performed
Description of intended operating environment and the EMC phenomena
present in that environment
– A Competent Body reviews the file and, if it considers the essential
requirements are met, issues a technical certificate.
Demonstrating Compliance
– A declaration of Conformity (DoC) is produced which
details the product name, manufacturer, Directive(s)
and standard(s) or Technical certificates.
– It is a “good idea” to keep a technical file when using
the standards route. This would provide the evidence to
a European court if complaints were ever made against
a manufacturer.
– Apply the CE Mark to the product
– Maintain a copy of the DoC with the European
distributor for ten years after the last product is sold.
Professional Audio Equipment Standards
•
•
•
•
EN55103-1 (Emissions)
EN55103-2 (Immunity)
Effective as of September 1st 1999
The scope of the standards covers
professional audio, video, audio-visual and
entertainment lighting control equipment.
Definitions
• Professional: Apparatus for use in trades, professions or
industries that is not intended for sale to the general public.
• Audio, video, audio-visual and entertainment lighting
control equipment:
 Designed for the purposes of controlling audio, video, audiovisual or
entertainment lighting characteristics;
 Designed for processing audio, video or lighting control signals in
digital form;
 Designed to control the intensity, color, nature or direction of light
from luminaries with the intention of creating artistic effects in
theatrical, televisual or musical productions and visual presentations.
Products NOT covered by EN55103
 Consumer apparatus (Sound cards)
 These would probably fall under EN55022/EN55024 for PC-based
cards. EN55013/EN55020 apply to Broadcast receivers and
associated equipment (stereo components)
 Apparatus specifically designed for security systems
(CCTV video equipment)
 These would fall under the standard for alarm systems
 Radio communications devices (wireless microphones)
 Radio communications equipment have their own specific
standards
Requirements
 The limits on the emissions from products
are defined in EN55103-1
 The immunity requirements are detailed in
EN55103-2
 Limits and test levels depend on the
intended environment of the product
Product Environments
 E1: Residential environment
 E2: Commercial and light industrial (e.g. theatres)
 E3: Urban outdoors
 E4: controlled EMC environment (e.g. purpose
built broadcasting/recording studios, rural outdoors
some distance from railways, transmitters, overhead
power lines etc.). It should be noted that some
studios might be considered as environment E2.
 E5: Heavy industrial environment and
environments close to broadcast transmitters.
EN55103-1 Emissions
Emissions Tests
Test Description
Radiated Emissions
Conducted Emissions (AC
power)
Signal, control and dc power
port emissions
Magnetic Emissions
(Rackmount)
Magnetic Emissions
(Non-Rackmount)
Harmonics /Flicker on AC
Clicks on AC
(Discontinuous interference)
In-Rush Current AC power
Antenna Port conducted
emissions
Test Method/limitations
EN55022, 30 – 1000 MHz,
only if device is a source of
noise above 30 MHz
EN55022, 0.15 – 30 MHz,
required on all AC ports
CISPR G recommendation,
0.15 – 30 MHz, required on all
signal, control and dc ports,
regardless of length
50Hz - 50 KHz test at 10cm
Test method outlined in Annex
A of standard
50Hz - 50 KHz test at 1m
Test method outlined in Annex
A of standard
EN61000-3-2 and -3
EN55014 – required if device
produces click interference
(e.g. has electro-mechanical
switches)
Required on all AC power
ports (usually measured when
performing VDI test
EN55013, 30 – 1000 MHz,
required on all antenna
terminals of radio/TV receivers
E1
E2
E3
Limits are the same as EN55022 Class B
30 – 230 MHz
30dBuV/m
230 – 1000MHz 37dBuV/m
Limits are the same as EN55022 Class B
Freq
0.15 – 0.5 MHz
0.5-5.0 MHz
QP Limit
50-40 dBuV
40 dBuV
Avg Limit
40 – 30 dBuV
30 dBuV
E4
E5
Limits are the same as EN55022 Class A
30 – 230 MHz
40dBuV/m
230 – 1000MHz 47dBuV/m
Limits are the same as EN55022 Class A
Freq
QP Limit
0.15 – 0.5 MHz 63-53 dBuV
0.5 – 30 MHz 53 dBuV
50 Hz – 500 Hz: 4-0.4 A/m (linear with frequency)
500 Hz – 5 kHz: 0.4 A/m
Not required
50 Hz – 500 Hz: 1-0.01 A/m (linear with frequency)
500 Hz – 5 kHz: 0.01 A/m
Limits as detailed in EN61000-3-2 and EN61000-3-3
Refer to clause 4.2 of EN55014
No limits, but manufacturer must state the peak inrush current in the user-documentation
Refer to EN55013, table 2
Avg Limit
53 – 43 dBuV
43 dBuV
Radiated Emissions, 30 - 1000 MHz
 Should be tested on an Open Area Test Site (OATS) or a
suitable emissions chamber
 For FCC testing, the frequency range may extend above
1GHz (1000MHz) :
 If the highest frequency generated/used is > 108MHz then test to 2
GHz
 If the highest frequency > 500 MHz then test to 5 GHz
 If >1 GHz then test to 5x frequency
Radiated Emissions, 30 - 1000 MHz
 Emissions tend to occur at harmonics of the digital clocks
plus power-supply switching harmonics !
 Emissions require an antenna with a length greater than
/10 (30m / f in MHz)
 Generally the emissions below 300 MHz are due to
common mode noise on external interface cables
 Above 300 MHz emissions tend to radiate from slots in the
enclosure
 Best controlled through good circuit layout
Radiated Emissions, 50Hz - 50kHz
 Tested using a loop antenna as specified in the EN55103-1
standard
 Loop can be made (or purchased - it is equivalent to mil
Std 461 RE101 Loop antenna)
 For rack-mount equipment, test at 10cm. For other, test at
1m
 Typically problem frequencies will be
 Switching frequency of power supply
 Harmonics of AC frequency due to diode switching action
AC Conducted Emissions
• Limits the rf voltage between line/neutral and ground in
the frequency range 0.15 - 30 MHz
• Use a LISN to measure the voltage (cost about $3000) with
an EMI receiver ($30,000) - however a pre-compliance
analyzer may be purchased for about $15,000 (Agilent
EM-series)
Signal and I/O Conducted Emissions
• Limits the common mode current /voltage on signal lines
and dc power in the frequency range 150kHz - 30 MHz
• For shielded lines, the test is performed with the shield
terminated to ground via a 150 ohm resistor
• Unshielded cables - common mode termination by tying
each signal lead to ground via a 150 ohms x n resistor (n =
number of signal lines)
• RF current probe is placed around the signal lead to be
tested
Signal and I/O Conducted Emissions
To support equipment only if
necessary to ensure correct
EUT operation - preferred
method is to simulate load
with passiv e components.
From
EUT
Shield exposed to allow
connection of alligator clip
150 ohm resistor
connected to shield
of cable
Tied to ground plane
Termination of a shielded cable
Signal and I/O Conducted Emissions
To support equipment only
if necessary to ensure
correct EUT operation otherwise terminate signal
leads to simulate actual
impedances.
From
EUT
To Measurement
Receiver
600 ohm resistors
0.018 uF cap (if necessary)
(minimum capacitance
based on a four conductor
cable)
Tied to ground plane
Termination of a four-wire, unshielded cable
AC Current Harmonics
• This test restricts the current harmonics that can be
produced by a power supply.
• If using an external PS vendor, specify that it must
meet the EN61000-3-2 standard
• Typically a power-factor-corrected (pfc) supply
will meet the requirements on harmonic current
emissions
• Could use vendor data to show compliance with
requirements (make sure they tested at power rating of your product)
AC Voltage Flicker
• “Flicker” is the effect caused when a large load
current is switched, creating a short-duration dip
in the AC voltage (e.g. refrigerator, when compressor switches on the
lights dim momentarily)
• Can only be measured with a custom-built test
equipment - but could be evaluated using a light
bulb connected to the same AC outlet ?
Other Emissions Tests
• Discontinuous interference
– Click interference
• In-Rush Current
– No limits but must specify the in rush current in
the user documentation
• Antenna Port Emissions
– Required if the device has receiver antenna
ports
EN55103-2 IMMUNITY
Immunity Tests (1)
Test Method
ESD
EN61000-4-2
Radiated Immunity
EN61000-4-3
Fast Transients
EN61000-4-4
Surge
EN61000-4-5
Port under test/Notes
Enclosure
Enclosure
For receivers, use
EN55020
AC input and output power
ports.
Signal and control ports
with cables longer than 3m
DC ports longer than 3m
Performance
Criteria
B
E1
E2
E3
A
±8kV Air
±4kV Contact
80 - 1000MHz, 1KHz 80% AM, 3V/m
B
1.0kV
B
0.5 kV
E4
E5
±4kV Air
±2kV Contact
80 - 1000MHz,
1KHz 80% AM,
1V/m
0.5kV
±8kV Air
±4kV Contact
80 - 1000MHz,
1KHz 80% AM, 10
V/m
2.0kV
1 kV using
coupling trench
B
0.5 kV
2 kV using
coupling trench
Input and output DC ports for connection to cables longer than 3m Not required if the device uses an AC-DC adapter, provided ACDC adapter is tested. Not required of the unit uses a dedicated dc supply that supplies only the EUT and nothing else
Functional Earth ports
B
0.5 kV
2 kV using
Only for earth ports that connect to cables longer than 3m
coupling trench
AC inputs
B
1kV Common mode
0.5kV Common
2kV Common
0.5kV differential mode
mode
mode
Immunity Tests (2)
Test Method
Conducted Immunity
EN61000-4-6
Port under test/Notes
Performance
Criteria
Signal and control ports
connecting to cables longer
than 1m
Input and output DC ports for
connection to cables longer
than 3m
A
AC input and output power
ports
Functional earth port
Voltage Dips Interrupts
EN61000-4-11
Magnetic Fields
Refer annex A of
EN55103 for details
Audio Frequency
Common Mode Refer
Annex B of EN55103
Input AC ports
All dips/interrupts
synchronized with zero
crossing
Enclosure Non-Rackmount:
Use Helmholtz coil/large loop
Enclosure - Rackmount
Using small loop as per Mil
Std 461
Balanced signal and control
ports which may exceed 10m
(for telecom ports use product
standard)
E1
E2
E3
0.15 – 80 MHz, 3 Vrms, 80% AM 1kHz
A
E4
E5
0.15 – 80 MHz,1
Vrms, 80% AM
1kHz
0.15 – 80 MHz,
10 Vrms, 80%
AM 1kHz
0.15 – 80 MHz,
10 Vrms, 80%
AM 1kHz
0.15 – 80 MHz, 3 Vrms, 80% AM 1kHz
Not required if the device uses an AC-DC adapter, provided AC-DC adapter is tested.
A
0.15 – 80 MHz, 3 Vrms, 80% AM 1kHz
0.15 – 80 MHz,1
Vrms, 80% AM
1kHz
A
0.15 – 80 MHz, 3 Vrms, 80% AM 1kHz
0.15 – 80 MHz,1
Vrms, 80% AM
1kHz
B
100 % for 20 mS
C
60% for 100mS
C
100% for 5000mS
A
A
A
50Hz–5kHz:
1 – 0.01 A/m
5kHz–10kHz:
0.01 A/m
50Hz – 5kHz: 3 – 0.03 A/m
5kHz – 10kHz: 0.03 A/m
0.15 – 80 MHz,
10 Vrms, 80%
AM 1kHz
0.15 – 80 MHz,
10 Vrms, 80%
AM 1kHz
50Hz – 5kHz:
50Hz – 5kHz:
0.8 – 0.008 A/m
10 – 0.1 A/m
5kHz – 10kHz:
5kHz – 10kHz:
0.008 A/m
0.1 A/m
50Hz–5kHz: 4 – 0.04 A/m
5kHz – 10kHz: 0.04 A/m
CRT degradation permitted above 1A/m for E1-4 and 3A/m for E5
Refer to Annex B.
Performance Criteria
During immunity testing the product’s performance has to be assessed
against various performance criteria:

Criterion A:
EUT should continue to operate as intended

Criterion B:
Degradation during the test but conformity with product specs after the test

Criterion C:
Degradation during the test and after the test. Conformity with product spec
via user-intervention or automatic recovery. Replacement of fuses, or other
repairs, does not constitute user-intervention
Performance Criteria - Examples
Examples of symptoms of lack of immunity for audio equipment are:
Reduced signal-to-noise
Increased non-linearity distortion
Clicks and pops
Pitch variations
Intermittent muting
Change in gain
Change in operating mode (e.g. sample rate changes)
ESD Immunity
• EN61000-4-2
• Performance Criteria B
• ESD events create high-speed transients that can:
• Permanently damage ICs
• Cause false resets or other spurious reactions
• The performance criteria is B - so some degradation
in performance is permitted during the test but the
device MUST recover without user intervention.
• ESD events caused by people discharging directly
to the product or to nearby objects
Radiated Immunity
• EN61000-4-3
• Performance Criteria A
• The device is subjected to a radiated field from 80
- 1000 MHz
• The field is amplitude modulated by a 1kHz tone
• Simulates interference from radio (broadcast,
walkie-talkie etc)
• Products typically demodulate the 1kHz tone,
creating interference on audio signal channels or
on video displays
Conducted Immunity
• EN61000-4-6
• Performance Criteria A
• Simulates interference on signal leads generated
from AM and SW radio
• A common mode interference signal is
superimposed onto signal and power interface ports
from 0.15 - 80 MHz
• The signal is amplitude modulated by a 1kHz tone
• Shielded signal lines have the noise directly
coupled onto the shield
Fast Transients
•
•
•
•
•
EN61000-4-4
Performance Criteria B
Fast transients have a rise time of 5nS and width of 50nS
Simulates switching of inductive loads
They are applied in bursts
– Bursts are 15mS long
– Repetition rate of individual transients is 5kHz
– Bursts occur every 330mS
Surge
• EN61000-4-5
• Performance Criteria B
• The surge waveform simulates the transients induced onto
the AC power line by lightning events
• The wave-shape is 1.2/50 S open circuit voltage through
a 2 ohm resistor (line to line) or 12 ohm resistor (line to
ground). The short circuit current wave-form is 8/20S
Voltage Dips and Interrupts
• EN61000-4-11
• Simulates sags and brownouts in the AC
supply voltage
• Unit must self recover after a single cycle
dropout (Criterion B)
• Criterion C (user intervention permitted) for
the 60%/100mS dip and 100%/5 second
interruption
Magnetic Field Immunity 50Hz-10kHz
• Test methods detailed in Annex A of EN55103-2
• Criterion A
• For Rack-Mount equipment, test level equals the
limit for the emissions
– (so this is to ensure immunity from other equipment)
• Test method depends on installation
– (rack-mount vs non-rack mount)
• Specification details the construction of the loops
– Possible to build the loops and perform tests in-house
using an audio signal generator
Audio Frequency Common Mode
• Test methods detailed in Annex B of
EN55103-2
• Required only for balanced signal/control
ports that connect to cables longer than 10m
• Annex B of the standard details the test
circuit
• Should be possible to test in-house
• Performance should be detailed in usermanual
Design Techniques
Although the next section concentrates on radiated emissions
solutions, there is a reciprocity between emissions and
immunity design techniques - the techniques that reduce
emissions from a circuit can also reduce the amount of
energy that is coupled into a circuit
Typical Problems
 Products with digital circuits typically have
problems meeting the emissions
requirements
 Products with predominantly audio circuitry
typically have problems meeting the
immunity requirements
Good Circuit Layout (1)
Be VERY careful when splitting ground planes
 Current flows in loops. The actual current path is the path of least
IMPEDANCE
 Large loops (relative to wavelength) create good radiating
mechanisms to couple onto other signal traces
 Fortunately at rf frequencies, return currents want to flow as close
as possible to the signal current as this gives the path with least
inductance and reduce the current loop - so provide the return path
by routing fast signals next to power or ground planes.
 NEVER let digital clocks cross splits in power planes - it forces
current to flow in loops
Current Loops
• Trace Crosses complete split
Current Loops
• Trace Crosses split
Current Loops
• No Split - no loop
Good Circuit Layout (2)
 Keep clock lines as short as possible
 Keep clock lines away from the edge of the board
 Provide rf decoupling capacitors (ceramic, 0.01uF) on switching ICs
located as close as possible to the IC
 Decoupling caps are only effective to 100 MHz or so, above this
frequency the best decoupling is achieved by having adjacent power
and ground planes.
 Clock lines should be terminated when they exceed 3” x tr to prevent
ringing on the lines caused by reflections at either end of a line because
the impedance of the trace  load/source impedance.
tr = rise time in nS
Good Circuit Layout (3)
 Provide filtering on all interface ports (including AC & DC power )
 RF caps to a “clean” ground (typically chassis), common mode chokes
or ferrite beads make ideal circuit elements
 Include the filter components on ALL signal lines, including ground
(especially where the ground is a digital signal ground)
I/O Interfaces
 If possible, use PCB connectors with metal back shells as these can
prevent high frequency signals radiated from the board from coupling
onto the signal lines after the filter
 Shields ideally terminate 360 to the enclosure (NOT to digital
ground).
 Shielded cables should have the shield terminated to the enclosure at
the “noisy” end(s) - single ended grounding at rf does not work
 Never use pigtails to terminate shields - at best they make a shielded
cable ineffective, at worst they can increase emissions.
 XLR cables are not designed for effective use of the shields - if you
cannot terminate the shield directly to chassis (because of low frequency
ground loops) tie to chassis using ceramic capacitors (alternatively create
a capacitor on the PCB)
Enclosure Design
• Required to reduce emissions above 250 MHz
• Can help with ESD and other immunity problems
• Slots and seams less than /10 (3cm @ 1GHz)
– Select /10 based on
• Highest clock speed
• Preliminary test data
• Previous product
• Conductive finishes on metals
• Good metal-to-metal contact (no paint !)
• For low frequency emissions, consider using steel
AC Power Supply
• Just because a power supply is CE-marked does not indicate that it
meets any emissions (or immunity) limits - but it should indicate that it
meets an appropriate LVD (electrical safety) standards.
• If the vendor specifies that an RFI filter is required, use one
• When using filters, make certain that the metal case is bonded to the
enclosure.
• Do not route the output wiring from the filter past any circuits, the
wiring should exit the enclosure immediately to prevent noise coupling
back onto the AC wiring.
AC Power Supply
AC Wiring layout to power supply via filter - good layout and bad layout Examples
P/S
Filter
Circuit Board
On/Off
AC Power Supply
AC Wiring layout to power supply via filter - good layout
On/Off
Filter
P/S
Circuit Board
Immunity Solutions (1)
• ESD
– Filtering I/O lines
– L-C circuits reduce common mode noise coupled into receivers
– Transzorbs (or similar devices)
• Fast switching times required - the rise time of ESD test
signal is typ. < 1nS
• Device clamps input signal to a maximum level,
preventing damage to inputs of ICs
– Good enclosure design
– Re-direct the ESD current away from circuitry
Immunity Solutions (2)
• ESD continued...
– Problems can be solved in software
• By regularly re-setting input buffers
– One example is a software driver for a mouse that empties the serial
input buffer to prevent the mouse from locking up
• By polling devices to ensure they are still active
• By averaging data - throw away data samples that are unexpected and
average remaining samples.
Immunity Solutions (3)
• Radiated Immunity
– Solve problems in a similar manner to radiated emissions
– Restrict bandwidths
– Add common mode filtering to audio inputs
– Pay particular attention to high-gain stages - make sure they are
provided with adequate rf decoupling
• Fast Transients
– Transzorbs on I/O lines, filtering, enclosure design all have an
effect
• Surge
– Power supply design could incorporate MoVs line-to-line (line-toground typically prohibited by Safety standard)
– AC line filters can reduce surge effects.
Emissions Case Study
• Product failing emissions below 150 MHz. Long clock
lines on a back plane-style circuit board inside aluminum
enclosure failing at 150 MHz
• Signals were radiating from internal back-plane out of the
chassis and from shielded interface cables connected
outside of the chassis
The fixes……….
• Had to remove non-conductive coating from the aluminum
panels where they touched each other
– Problem - aluminum oxide is non-conductive and it oxidizes
quickly. Within a couple of days the emissions were high again
and had to remove oxide layer.
• Improved enclosure’s rf integrity using a conductive
coating and gaskets to ensure good metal-to-metal contact
• Added series termination to clock lines to reduce problem
at board level
• Improved grounding of the interface cable shields by
improving contact between connector shells and enclosure
EMC As Part Of The Development Cycle
Don’t leave EMC until the end !
• Remember EMC at the start of the project
– Define the intended environment so that the immunity
levels and emissions limits can be identified
• E1 - E3 require 10dB lower radiated emissions that E4 and E5
• E4 has lower immunity test levels
– Specify EMC requirements on external vendors based
on the intended environment (e.g. power supplies)
– Test prototype boards ( Emissions/ESD)
• Emissions tests:
– RF current probes can be used to measure common mode
current on I/O cables in-house (refer to Ott, Chapter 11)
• Keep common mode current below 15uA at any
frequency for Class A, 5uA for Class B
– If local test labs have chambers, get a “quick”scan of
boards in the development stage (typically < 2 hours per
test)
• Identify potential immunity problems :
– if the unit passes ESD with no errors, that is a good
indication that the unit will not be susceptible to most of
the EMC phenomena.
– ESD guns cost about $6,000 (Schaffner / Keytech)
– Can be rented (Metric / Telogy)
• Use emissions/immunity preliminary data:
– the enclosure can be designed to provide adequate
shielding
– enclosure design can be based on the highest significant
emissions observed during the preliminary scans
– filters can be placed on interface ports to reduce common
mode noise
– grounding strategies can be evaluated
Summary
• Professional audio equipment has many EMC test
requirements compared to generic products
• It is possible to perform some of the tests in-house
without spending $$$$
• It will probably be necessary to perform some
tests at a test lab
• If EMC is taken into consideration at the start of
the project time-to-market is reduced and redesign costs are minimized.
Literature References
• The Guide to The EMC Directive
Chris Marshman, IEEE Press
• Noise Reduction Techniques in Electronic Circuits
Henry Ott, John Wiley
• High Frequency Measurements and Noise in Electronic
Circuits
Douglas Smith, Van Nostrand Reinhold
Magazine subscriptions:
Compliance Engineering
Evaluation Engineering
EMC Test Equipment
• Fischer Custom Communications
• [email protected]
• Current probes for making common mode emissions
measurements (150kHz - 300 MHz)
• LISNs for making conducted emissions measurements on AC
• Agilent
• Spectrum Analyzers (8595EM analyzer)
• Haefely
• Immunity test equipment
• Schaffner
• Immunity test equipment
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