EMC VI-200 User's Manual
Contents
1. resulting in a spike of noise current at 50 70 MHz that flows from primary to secondary Figure 9 8 This noise current is common mode as opposed to differential and therefore should not affect the operation of the system It should be noted however that oscilloscopes have a finite ability to reject common mode signals and these signals can be abnormally emphasized by the use of long ground leads on the scope probe Primary Baseplate C FET C Rectifier Secondary C Rectifier C External C External Ycaps Ycaps Figure 9 8 Noise coupling model MEASURING OUTPUT NOISE Long ground leads adversely impact the common mode rejection capability of oscilloscopes because the ground lead has inductance not present on the signal lead These differing impedances take common mode signals and convert them to differential signals that show up on the trace To check for common mode noise place the oscilloscope probe on the ground lead connection of the probe while the ground lead is tied to output return Figure 9 9 If the noise is common mode there will still be noise observed at the same test point NOTE The output return must be at the same relative potential as the earth ground of the oscilloscope or damaging current may flow through the oscilloscope ground lead Capacitors are required from the IN to the baseplate thereby shunting common mode current thus reducing noise current on the input power lines The ca2. the DC source and returns to the converter via the grounded baseplate or output lead connections This represents a potentially large loop cross sectional area which if not effectively controlled can generate magnetic fields Common mode noise is a function of the dv dt across the main switch in the converter and the effective input to baseplate and input to output capacitance of the converter The most effective means to reduce common mode current is to bypass both input leads to the baseplate with Y capacitors C2 keeping the leads short to reduce parasitic inductance Additionally a common mode choke L1 is usually required to meet FCC VDE A or B Figure 9 2 Typical Vicor Module 48 V Input 5 V Output VI 230 CV C1 100 uF C2 4 700 pF C3 0 01 uF Nominal Line 48 V Conducted Noise vs Load 3 Amp Load 15 Amp Load j j A LUEN JAN J Unt o E Diw 20 be 18 ea RBH T STAr ao sec En 18 P P p aia HZ Figure 9 1 Conducted input noise no additional filtering vicorpower com 800 735 6200 ihe in ATE d5 r _18GE08 086 PZ Applications Engineering 1 800 927 9474 Conditions Light Load 3 A Nominal Load 15 A Full Load 30 A 30 Amp Load i tty Li i bith Enid TEE opa BRE H ay ae ly Hz Bo L RARGE Re 0 1 104Be Rev 2 1 M E a Page 18 of 88 Design Guide amp Applications Manual 9 EMC Considerations For VI 200 and VI JOO Family DC DC Converter
3. 0 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 28 of 88
4. 9 EMC Considerations CONDUCTED NOISE Conducted noise is the AC current flowing between the source voltage and the power supply It includes both common mode and differential mode noise Vicor zero current switching converters are 20 40 dB lower in conducted noise than a traditional board mounted PWM converter however if a specific EMC specification such as FCC or VDE must be met additional filtering may be required Since the noise generated is ten to a hundred times lower than fixed frequency converters an existing filter should provide equal or better performance when the conditions in the Module Do s and Don ts section are followed Section 3 In the event the system does not contain an existing filter the following will provide valuable information relative to the attainment of system conducted noise objectives System requirements such as Tempest military or UL544 EN60601 medical require a somewhat different approach Medical requirements vary as a function of the application and country please contact Vicor Applications Engineering for additional details Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies Common Mode Noise with No Additional Filtering Common mode conducted noise current is the unidirectional in phase component in both the IN and IN pins to the module This current circulates from the converter via the power input leads to
5. CV 48 V Input 5 V Output C1 100 pF C2 C2 4 700 pF Vicor Part 01000 C3 C3p 0 01 pF Vicor Part 04872 Conditions Light Load 3 A Nominal Load 15 A Full Load 30 A C4 2 2 uF L1 20 pH L2 20 pH Conducted Noise vs Load 3 Amp Load F EF U i j a N A r i oan WV Lj Alaa on ee POA Figure 9 5 Conducted noise differential mode filtering vicorpower com 800 735 6200 15 Amp Load 1 a reer eth AMN PT o e Applications Engineering 1 800 927 9474 30 Amp Load Lhi il Eraill rs cd linn e pA aA Rev 2 1 M E a Page 22 of 88 Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies RADIATED NOISE Radiated noise may be either electric field or magnetic field Magnetic radiation is caused by high di dt and is generally what is measured by FCC VDE or MIL STD 461 Vicor converters utilize zero current switching with the advantage over PWM non zero current switching being that zero current switching topologies contain minimal discontinuities in the switched current waveforms resulting in lower di dt s Electric field radiation caused by dv dt is near field i e it decays rapidly as a function of distance and as a result does not typically affect radiated measurements Radiation can be minimized by proper board layout Keep all leads with AC current short twisted or routed as ove
6. Configurable Power Supplies Differential and Common Mode Filter with More than One Module No special precautions are needed when using two or more modules The filter required will have the same characteristics as a single module filter 9 EMC Considerations however the wire size on the magnetics will need to reflect the increased input current Shown below is the input conducted noise for two modules sharing a common input source Differential and Common Mode Filter with More than One Module 48 V Inputs 5 V Outputs Two Vicor VI 230 CV Modules Three common mode chokes are offered as standard accessories Resistance Each Winding Inductance Maximum Each Winding DC Current NOTE Common mode filters may be common to one or more modules but only one should be used with modules interconnected via GATE IN s or GATE OUT to GATE IN As an example Driver Booster arrays or Drivers with GATE IN s tied together to provide a common disable function Part Number C2q 47 uF 4 700 pF 0 01 UF 2 2 UF 3 000 uH 20 WH Conditions Light Load 3 A Nominal Load 15 A Full Load 30 A Vicor Part 01000 Vicor Part 04872 Vicor Part 31742 Conducted Noise vs Load 3 Amp 3 Amp Load 3 Amp 6 Amp Load 3 Amp 30 Amp Load ata prairie sp a eea a paa nar GE emer el E E aeania eneket EE HF ay ae ae Ub i Bik a aED int ilice deca anaia e om J tajli D1 Dpi START 2 222 000 Hz 20 89 10 69
7. STOP 3 Gee Geo Bee He 2 i G23 88 Hz REH 23 0 sec RANGEIR 16 T 20din S 12 fe 20E 1 KHz T 12 ST0P _tappage Ada HZ Figure 9 4 Conducted noise multiple zero current switching converters y SE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 21 of 88 9 EMC Considerations Differential Mode Noise Filter Ditferential mode conducted noise current is the component of current at the input power pin which is opposite in direction or phase with respect to the other input power pin All Vicor converters have an internal differential mode LC filter which in conjunction with a small external capacitor C1 minimum value in uF 400 Vin reduces ditferential mode conducted noise The external capacitor should be placed close to the module to reduce loop cross sectional area Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies Care should be taken to reduce the loop cross sectional area of differential mode current flowing between the source and C1 Since differential mode input current is by definition opposite in phase twisting the input leads causes noise cancellation PCB power planes can reduce radiated noise if the traces are on opposite sides of the PCB directly over one another If differential mode inductance is used it may be common to one or more modules Differential Mode Filter Typical Vicor Module VI 230
8. V p p E ES e gt ey T i y SEE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 25 of 88 9 EMC Considerations Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies Addition of Output Capacitor Typical Vicor Module VI 230 CV 48 V Input 5 V Output Ci 100 pF Conditions C2 C2 p 4 700 pF Vicor Part 01000 Light Load 3 A C3 C3p 0 01 pF Vicor Part 04872 Nominal Load 15 A C4 270 pF Tant PUM EDAT OUA C2 NOTE A low ESR capacitor should be used on the output preferably tantalum Output Ripple vs Load 3 Amp Load 15 Amp Load 30 Amp Load CH1 50 mVac ewl 2 uS CH1 20 mVac swm 500 nS CH1 20 mVac evn 500 nS 99 5 mV p p 48 4 mV p p 53 8 mV p p a eee _ S a EE SSS Figure 9 11 Output noise additional output capacitance y SE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 26 of 88 Design Guide amp Applications Manual 9 EMC Considerations For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies LC Output Filter Typical Vicor Module VI 230 CV 48 V Input 5 V Output 100 uF 4 700 pF Vicor Part 01000 Conditions 0 01 uF Vicor Part 04872 Light Load 3 A 270 uF Tant Nominal Load 15 A 200 nH Vicor Par
9. nalog systems such as input to the converter has 30 V p p of ripple the output ultrasound systems will probably require additional output p p ripple would be 15 8 mV It is not practical to filtering See additional output filter choices in Table 9 1 attenuate this component further with passive filtering due to its low frequency hence active filtering is required The RAM contains both a passive filter for high frequency noise and an active filter for low frequency noise Line Related Output Noise Line related output noise can be determined from the converter specification Input Ripple Rejection As an example a VI 260 CV 5 V Outputs 12 15 V Outputs 24 48 V Outputs No Additional Filter 2 p p Typical Low ESR Output Cap 1 p p Typical 0 5 p p Typical LC Output Filter 0 4 p p Typical 0 2 p p Typical RAM Filter VI 200 lt 3 mV p p Maximum lt 3 mV p p Maximum RAM Filter VI JOO lt 10 mV Maximum lt 10 mV Maximum lt 10 mV Maximum Table 9 1 Output filter options and output voltage and ripple Differential Output Filtering Typical Vicor Module VI 230 CV 48 V Input 5 V Output Conditions Ci 100 uF Light Load 3A C2 C2 4 700pF Vicor Part 01000 Nominal Load 15 A C3 C3p 0 01 UF Vicor Part 04872 Full Load 30 A Output Ripple vs Load 3 Amp Load 15 Amp Load 30 Amp Load CH1 50 mVac ew 2 yS CH1 50 mVac aw 500 nS CH1 50 mVac aw 500 nS 148 mV p p We nv ee 141 m
10. ons Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies Typical Vicor Module VI 230 CV 48 V Input 5 V Output Three common mode chokes are offered as standard accessories Part Inductance Maximum Resistance Number Each Winding DC Current Each Winding 1 000 uH 12 Amperes 6 5 MQ 3 000 pH 18 mQ NOTE Common mode filters may be common to one or more modules but only one should be used with modules interconnected via GATE IN s or GATE OUT to GATE IN As C2p C3 an example Driver Booster arrays or Drivers with GATE IN s 100 uF tied together to provide a common disable function 4 700 pF Vicor Part 01000 Conditions 0 01 uF Vicor Part 04872 Light Load 3 A 2 2 uF Nominal Load 15 A 3 000 pH Vicor Part 31742 Full Load 30 A Conducted Noise vs Load 3 Amp Load 15 Amp Load 30 Amp Load ip Ti i J j 1 i Wiara prt adaki sith ama A EI oe f pk Ei E amp 5 I E STAR 188 GEC OCA Hz iv Diw START 160 F00 CCE Hz r STOP 36 BOO OBB BOD He co e Lo 0p 31T0F J30 BBE ERE OBE He T F cee RANGE S amp B T iDdff Pfu i0 Khz T46 dJ set RANGE R D Ta ipdEa 2 STAR Bee HZ Figure 9 3 Conducted input noise with common mode choke y SEE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 20 of 88 Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and
11. pacitor must vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies have very short leads since the frequency is high It must also be a good capacitor i e ceramic or other material that has a low ESR ESL This type of capacitor is most important on high input voltage units since the dv is larger but is required for all units For off line applications this capacitor must have the appropriate safety agency approvals Insert probe into female receptacle Vicor P N 06207 for proper output differential noise measurement technique To Scope ce Ground Ring on Probe To Scope Figure 9 9 Output ripple measurement technique A capacitor from Vout to the baseplate is required since the output rectifier has a changing voltage on it and like the FET can generate common mode noise This capacitor is similarly recommended for high output voltage units 48 V Common mode noise is not differential with respect to the output It does however flow in both input and output leads of the power supply and is a noise parameter that is measured by the FCC or VDE It can cause power systems to fail radiated emission tests so it must be dealt with Bypass capacitors to the baseplate with a common mode filter on the input of the module or the main input of the power su
12. pply is required The common mode filter is typically placed on the input as opposed to the output Theoretically since this current flows from primary to secondary the choke could be placed in either the input or the output but is preferably placed in the input leads for the following reasons 1 input currents are smaller since the input voltage is usually higher 2 line regulation of the module can correct for voltage drops across the choke and 3 if the choke is on the output and the senses are connected to the other side of it the stability of the loop may be impacted Differential output noise is the AC component of the output voltage that is not common to both outputs The noise is comprised of both low frequency line related noise typically 120 Hz and high frequency switching noise Rev 2 1 A Page 24 of 88 Design Guide amp Applications Manual 9 EMC Considerations For VI 200 and VI JOO Family DC DC Converters and Configurable Power Supplies High Frequency Switching Noise Peak to peak output 300 Vin to 5 Vout has a rejection specification at 120 Hz voltage ripple is typically 2 or less 1 for 12 V outputs of 30 20 Log Vin Vout Vin 300 and Vout 5 and above Hence additional output filtering is generally hence its rejection is 30 35 56 65 56 dB which not required Digital systems rarely need additional provides an attenuation factor of 1 89 k Therefore if the filtering However some a
13. r Supplies The use of the RAM MI RAM is very straightforward but a couple of precautions should be noted The LC filter is in the positive output lead so if that lead is shorted then the high frequency attenuation is compromised The active circuit is in the negative output lead so if that lead is shorted the low frequency attenuation is compromised The RAM must be used with a common mode choke at the input of the converter The RAM is intended to be used with the Vicor VI 200 VI JOO and the MI RAM is intended to be used with Vicor MI 200 MI JOO Family of DC DC converter modules It is also available in a chassis mounted version as VI LRAM xx MegaMod package or VI RAM xx B1 BusMod package NOTE Do not use if load is inductive as instability may result The addition of the RAM will increase the converter s current limit setpoint by 14 RAM Output Filter Typical Vicor Module VI 230 CV 48 V Input 5 V Output with VI RAM C2 N 4O0UT S IN S RAM S IN S IN OUT Conditions C1 100 pF Light Load 3 A C2 C2p 4 700 pF Vicor Part 01000 Full Load 15 A C3 C3p 0 01 uF Vicor Part 33643 Overload Condition 30 A C4 220 uF Electrolytic Output Ripple vs Load 30 Amp Load 3 Amp Load Overload Condition 15 Amp Load i ertiinis ici bake ae tap eda NEE L kir Ahiria Epey T mig PEETI EA AEA TA es a Pr i EEUN op ee t E Pe TAS wid 1 if ion eee y SEE vicorpower com 80
14. rlapping planes to minimize loop cross sectional area Also keep in mind the effects of capacitive coupling even when not expected Do not put an unshielded filter on the opposite side of the PCB from the module Conducted noise can be capacitively coupled around the filter Do not route input and output leads in the same cable bundle Again no special precautions just good design practice NOISE CONSIDERATIONS All switchmode power supplies generate a certain amount of noise yet it remains one of the least understood parameters in power conversion VI 200s and VI JOOs both use the same topology so their operation is very similar These products are zero current switching converters i e the current is zero when the main switch is turned on or off While the switch is on the current through the switch or the primary of the transformer is a half wave rectified sine wave Similar in operation to a resonant converter these products are commonly referred to as quasi resonant converters The LC resonant frequency is fixed so the on time of the switch is about 500 ns When the switch turns on energy builds up in the leakage inductance of the transformer L and then transferred into the capacitor on the secondary side of the module C Figure 9 6 The energy processed in each pulse is fixed and is ultimately the energy stored in this capacitor 1 2 CV2 Since the energy in every pulse is fixed the repetition rate of
15. s and Configurable Power Supplies Common Mode Noise with Common Mode Choke NOTE In most cases a fixed frequency converter There are no special precautions that must be exercised in generates more input conducted noise with a filter the design of input filters for Vicor converters In fact if than Vicor s zero current switching converter without the system contains an EMC filter designed for typical a filter Also note that fixed frequency converters fixed frequency converters it should be sufficient as is using a construction technique involving control although not optimal in terms of size as zero current circuitry on the same metal plate as power processing switching converters inherently generate significantly less components will generate significantly more input conducted noise noise than shown The plots in Figure 9 2 are representative of fixed frequency converters with input filtering Typical Fixed Frequency Converter PWM 48 V Input 5 V Output Conditions C1 2 2 uF Light Load 3 A C2 100uF Nominal Line 48V Nominal Load 15 A C3 Internal Full Load 30 A C4 Internal L1 3 mH Conducted Noise vs Load 3 Amp Load 15 Amp Load 30 Amp Load re MR j tf iio va bach tial a Paget anana ana He Figure 9 2 Conducted input noise typical fixed frequency converter with filter y SE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 19 of 88 9 EMC Considerati
16. t 30268 Full Load 30 A Output Ripple vs Load 3 Amp Load 15 Amp Load 30 Amp Load CH1 20 mVac em 2 ps CH1 20 mVac ew 1 p5 CH1 20 mVac ew 500 nS 28 4 mV p p 17 0 mV pep 20 8 mV p p F E i 4 T i f k ae ee eee a rivet pert feet nee Figure 9 12 Output noise additional output inductor and capacitor L C Filter y SE vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 Rev 2 1 Page 27 of 88 9 EMC Considerations RAM MI RAM OPERATION The RAM MI RAM attenuates output noise in two ways First an LC filter in the RAM MI RAM attenuates high frequency components associated with the switching frequency Secondly the RAM MI RAM contains an active filter that attenuates low frequency components associated with the input to the converter These frequencies are on the order of 60 120 Hz and harmonics would require very large output LC if a passive approach were to be used Essentially the active circuit looks at the output ripple from the converter multiplies it by 1 inverts and adds it to the output This effectively cancels out the low frequency components The RAM does not contain any common mode filtering so whatever common mode noise is present Is passed through It only provides differential filtering of noise that is present on one output pin relative to the other Design Guide amp Applications Manual For VI 200 and VI JOO Family DC DC Converters and Configurable Powe
17. the pulse train is varied as a function of load to regulate the output voltage Maximum repetition rate occurs at minimum line full load and is approximately twice the LC time period or 1 us If the load drops by 50 then the repetition rate is approximately one half of maximum since the energy in every pulse is fixed Therefore the pulse repetition rate varies linearly with load to a first order approximation vicorpower com 800 735 6200 Applications Engineering 1 800 927 9474 9 EMC Considerations Figure 9 6 Basic zero current switching converter topology VI 200 VI JOO Since the energy in every pulse is related to the square of the applied voltage CV2 the pulse repetition rate varies as approximately the square of the line voltage For example a 300 V input unit can vary from 200 400 v or a factor of two therefore it follows that the repetition rate must vary by approximately a factor of four to regulate the output As previously established the current in the primary is a half wave rectified sine wave but the voltage on the primary is a square wave Since this voltage is a square wave it contains harmonics of the fundamental switching trequency It also includes frequencies that extend to 70 MHz These frequencies can be of interest in the following circumstances Rapidly changing voltages high dv dt can generate E fields primarily near field which do not usually cause system noise problems since
18. they significantly decrease as a function of distance For this reason E tields are not measured by agencies such as the FCC or VDE These agencies do however measure the magnetic radiation caused by high frequency currents in a conductor The half wave rectified sine wave in the transformer is an example of this but since there are minimal discontinuities in the current waveform and the loop cross sectional area is very small the resultant E field is very small E fields can be a problem if sensitive circuitry is located near the module In this case a shield can be positioned under the label side of the module as a discrete element or as a ground plane on the PCB The other effect that occurs as a result of the 50 70 MHz component on the main switch is common mode noise Figure 9 7 Parasitic Capacitance FET aN Rectifier Shield ra Shield Ceramic N Ceramic O Ge Baseplate Figure 9 7 The shield layer serves to reduce the capacitance Rev 2 1 E a Page 23 of 88 9 EMC Considerations The dv dt of the switch FET is a noise generator This FET is mounted on a two layer insulating and shielding assembly which is attached to the baseplate Since ceramic is a dielectric there is capacitance from the FET to the baseplate Figure 9 7 The output rectifiers are also tied to the baseplate with ceramic insulators adding additional capacitance The dv dt of the FET Is differentiated by these two series capacitors
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