FORTRONIC POWER FORUM 2014
High isolation dc-dc converters applications and specifications
Paul Lee - Director of Business Development
Murata Power Solutions UK
www.murata-ps.com
High Isolation DC-DC converters – applications and specifications
Topics today
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Why ‘high’ isolation? - Applications
Grades of isolation
Other insulation characteristics
Testing
Pitfalls
Products
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
1. To provide immunity to noise transients across an isolation
barrier such as in an isolated data interface
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
Isolated data interface
No particular standard applies but 3kV functional typical
This example Analog Devices isoalted RS422 data interface
Actual voltage across barrier normally ~ zero
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
2. To allow DC-DC secondary to be referenced to a high
continuous or switched voltage eg ‘high-side’ gate drives
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
3. To provide a safety barrier to protect personnel or property
from electric shock
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
4. To provide a safety barrier to protect personnel or
property from electric shock
Faulty
equipment
240V
AC
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High Isolation DC-DC converters – applications and specifications
Why ‘high’ isolation?
5.
As a convenience in testing
End-to-end 4kV hi-pot
test imposes only 1kV
across the safety
barrier and 3kV
across the low
isolation barrier
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
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Functional
Basic
Supplementary
Double
Reinforced
Measures of protection MOOP, MOPP
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional
 Isolation that provides no agency rated safety barrier,
typically just enamel insulation on wire
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional
 Isolation that provides no agency rated safety barrier,
typically just enamel insulation on wire
 DC-DCs can have test agency eg UL recognition with
functional isolation but relates to other factors such as
temperature rise, flammability
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional
 Isolation that provides no agency rated safety barrier,
typically just enamel insulation on wire
 DC-DCs can have test agency eg UL recognition with
functional isolation but relates to other factors such as
temperature rise, flammability
 Eg Murata NKE 3kV DC functional isolation
production tested for one second
UL recognised and marked component
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional -continued
 3kV ‘functional’ rating is a production test voltage – gives
confidence in immunity to occasional transients not
continuous voltage!
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional -continued
 3kV ‘functional’ rating is a production test voltage – gives
confidence in immunity to occasional transients not
continuous voltage!
 Analogy is car engine - type tested at 8000rpm but you
wouldn’t continuously run at this figure!
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional -continued
 3kV ‘functional’ rating is a production test voltage – gives
confidence in immunity to occasional transients not
continuous voltage!
 Analogy is car engine - type tested at 8000rpm but you
wouldn’t continuously run at this figure!
 Continuous rating should be much less – depends on
construction/environment/age. Generally keep within SELV
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Functional -continued
 3kV ‘functional’ rating is a production test voltage – gives
confidence in immunity to occasional transients not
continuous voltage!
 Analogy is car engine - type tested at 8000rpm but you
wouldn’t continuously run at this figure!
 Continuous rating should be much less – depends on
construction/environment/age. Generally keep within SELV
 Some DC-DC data sheets give equivalent continuous ratings
– no basis. Current safety standards do not feature this
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Basic
 Insulation of hazardous parts providing ‘basic’ (minimum,
single) protection against electric shock
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Basic
 Insulation of hazardous parts providing ‘basic’ (minimum,
single) protection against electric shock
 Eg. Insulation from hazardous voltage to an earthed part
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Basic
 Insulation of hazardous parts providing ‘basic’ (minimum,
single) protection against electric shock
 Eg. Insulation from hazard to an earthed part
 One measure of protection in medical parlance
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Basic
 Insulation of hazardous parts providing ‘basic’ (minimum,
single) protection against electric shock
 Eg. Insulation from hazard to an earthed part
 One measure of protection in medical parlance
 Useful when combined with other barriers to provide the
equivalent of reinforced isolation from hazardous voltages
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Supplementary
 Independent insulation/isolation of the same grade as BASIC
or better that is added to BASIC insulation to give protection
against electric shock if the BASIC insulation fails
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Supplementary
 Independent insulation/isolation of the same grade as BASIC
or better that is added to BASIC insulation to give protection
against electric shock if the BASIC insulation fails
 Must be able to test the SUPPLEMENTARY and BASIC
insulation/isolation separately
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Double
 The combination of BASIC and SUPPLEMENTARY insulation
together in one insulation system
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Double
 The combination of BASIC and SUPPLEMENTARY insulation
together in one insulation system
 DOUBLE is sufficient for a product to be deemed safe by
safety agencies
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Reinforced
 A single isolation system of distance, solid material or
multilayer material providing protection not less than DOUBLE
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Reinforced
 A single isolation system of distance, solid material or
multilayer material providing protection not less than DOUBLE
 Multilayer material may have layers that cannot be tested
individually eg double/triple insulated wire
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Reinforced
 A single isoaltion system of distance, solid material or
multilayer material providing protection not less than DOUBLE
 Multilayer material may have layers that cannot be tested
individually eg double/triple insulated wire
 Reinforced provides adequate confidence of protection against
electric shock for a reasonable length of time in an assumed
environment if tested 100% in production and verified regularly
NOTE QUALIFIERS!
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So how are spacings/material type, grade and thickness
calculated to agency standards?
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So how are spacings/material type, grade and thickness
calculated to agency standards?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
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High Isolation DC-DC converters – applications and specifications
Operating system voltage is 264VAC but
DC-DC input is 12Vdc
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
 Pollution degree of the environment around the DC-DC
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
 Pollution degree of the environment around the DC-DC
 Altitude - 8 capital cities over 2000m including Mexico City
2240m, La Paz 3840m, Quito 2850m
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
 Pollution degree of the environment around the DC-DC
 Altitude
 Material group type for creepage surfaces
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
 Pollution degree of the environment around the DC-DC
 Altitude
 Material group type for creepage surfaces
 Particular standard applied
www.murata-ps.com
High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 So what’s required to achieve the different levels of
insulation?
 Depends on:
 Operating (system) voltage (Not input voltage to the DC-DC)
 Overvoltage category of the system voltage
 Pollution degree of the environment around the DC-DC
 Altitude
 Material group type for creepage surfaces
 Particular standard applied
 Constraints to use of the part eg temperature, fusing
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Examples:
 A given insulation system will achieve different levels
depending on all the above factors
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High Isolation DC-DC converters – applications and specifications
Grades of Isolation/Insulation
 Examples:
 A given insulation system will achieve different levels
depending on all the above factors
 2mm creepage and clearance in Murata product MEJ1
achieves BASIC or 1 x MOOP at a working voltage of
200Vrms at a max ambient of 85C to latest medical
standards.
2mm creepage and clearance in Murata product NMJ
achieves reinforced insulation according to UL 60950 at a
working voltage of 150Vrms in a 60C ambient
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High Isolation DC-DC converters – applications and specifications
Other insulation characteristics
 Capacitance
 Significant if operating voltage is AC – gives rise to
leakage current
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High Isolation DC-DC converters – applications and specifications
Other insulation characteristics
 Capacitance
 Significant if operating voltage is AC – gives rise to
leakage current
 dv/dt immunity
 In IGBT gate dive applications for example, DC-DC can
see >20kV/us dv/dt
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High Isolation DC-DC converters – applications and specifications
Other insulation characteristics
 Capacitance
 Significant if operating voltage is AC – gives rise to
leakage current
 Dv/Dt immunity
 In IGBT gate dive applications for example, DC-DC can
see >20kV/us dv/dt
 Partial discharge immunity
 With continuous high voltages, barrier should not
degrade significantly due to partial discharge in material
voids
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High Isolation DC-DC converters – applications and specifications
Testing
Can expect all DC-DC products are 100% production tested
(even functional grade)
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High Isolation DC-DC converters – applications and specifications
Testing
Can expect all DC-DC products are 100% production tested
(even functional grade)
Standards will often specify insulation test voltages for one
minute but allow shorter test time at higher voltages
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High Isolation DC-DC converters – applications and specifications
Testing
Can expect all DC-DC products are 100% production tested
(even functional grade)
Standards will often specify insulated rated for a voltage for
one minute but allow shorter test time at higher voltages
Testing should not be unnecessarily repeated – degrades
isolation however…
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High Isolation DC-DC converters – applications and specifications
Testing
Can expect all DC-DC products are 100% production tested
(even functional grade)
Standards will often specify insulated rated for a voltage for
one minute but allow shorter test time at higher voltages
Testing should not be unnecessarily repeated – degrades
isolation however…
Converters used for safety isolation should be regularly tested
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High Isolation DC-DC converters – applications and specifications
Pitfalls
 Beware misleading ‘approval’ statements – claims
meaningless unless all conditions stated
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High Isolation DC-DC converters – applications and specifications
Pitfalls
 Beware misleading ‘approval’ statements – claims
meaningless unless all conditions stated
 Far eastern suppliers have been known to fake approvals
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High Isolation DC-DC converters – applications and specifications
Pitfalls
 Beware misleading ‘approval’ statements – claims
meaningless unless all conditions stated
 Far eastern suppliers have been known to fake approvals
 Beware counterfeit parts!
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High Isolation DC-DC converters – applications and specifications
Recent ‘reject’ parts received at Murata marked as Murata
Pretends to be an NMS product UL rated for reinforced
insulation to 150Vrms
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High Isolation DC-DC converters – applications and specifications
Murata low power DC-DC Product examples
High isolation, ‘3kV functional’ rating:
NKE series
Miniature
1W UL
listed
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NMV series
SIP7 3W
UL listed
NTV series
1W SMT
High Isolation DC-DC converters – applications and specifications
Murata low power DC-DC Product examples
High isolation, ‘basic and higher’ rating:
MEJ1/2 series
1/2W SIP7
Basic/1 x
MOOP to
200Vrms
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NCM6 series
6W DIP24
Reinforced / 2 x
MOOP to
250Vrms
MGJ2 series
(IGBT)
2W SIP7
Basic / 1 x MOOP
to 200Vrms
Pending
High Isolation DC-DC converters – applications and specifications
Murata low power DC-DC Product examples
High isolation, ‘basic and higher’ rating: Coming soon
3W/6W
Reinforced / 2 x MOOPs
High dv/dt rating
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High Isolation DC-DC converters – applications and specifications
Thanks!
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