Power Supply User's Manual

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Design Guide & Applications Manual

For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

vicorpower.com 800-735-6200 Applications Engineering 1-800-927-9474 Rev. 2.1

Page 18 of 88

+IN

GATE

OUT

–IN

+OUT

TRIM

–S

–OUT

C1 = 100 μF

C2 = 4,700 pF

C3 = 0.01 μF

Conditions:

Light Load = 3 A

Nominal Line = 48 V Nominal Load = 15 A

Full Load = 30 A

Figure 9–1 — Conducted input noise, no additional filtering

3 Amp Load 15 Amp Load 30 Amp Load

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.

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 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)

9. EMC Considerations

Conducted Noise vs. Load

Typical Vicor Module

48 V Input, 5 V Output (VI-230-CV)

Summary of content (11 pages)

PAGE 1
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies 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.
PAGE 2
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies Common-Mode Noise with Common-Mode Choke. There are no special precautions that must be exercised in the design of input filters for Vicor converters.
PAGE 3
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output C2a L1 C4 C3a +IN GATE IN GATE OUT –IN C1 C2b Three common-mode chokes are offered as standard accessories. Part Number 31743 31742 31943 +OUT +S TRIM –S –OUT C3b (Vicor Part # 01000) Conditions (Vicor Part # 04872) Light Load = 3 A Resistance Each Winding 6.5 mΩ 18 mΩ 42 mΩ Nominal Load = 15 A C4 = 2.
PAGE 4
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and 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, however the wire size on the magnetics will need to reflect the increased input current.
PAGE 5
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies Differential-Mode Noise Filter. Differential-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.
PAGE 6
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies RADIATED NOISE Vs 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.
PAGE 7
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies 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.
PAGE 8
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies High Frequency Switching Noise. Peak-to-peak output voltage ripple is typically 2% or less (1% for 12 V outputs and above). Hence additional output filtering is generally not required. Digital systems rarely need additional filtering. However some analog systems, such as ultrasound systems, will probably require additional output filtering.
PAGE 9
. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies Addition of Output Capacitor Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output C3a C2a C1 +IN +OUT GATE IN GATE OUT –IN +S TRIM –S –OUT C1 = 100 µF C4 C2a – C2b = 4,700 pF (Vicor Part # 01000) C3a – C3b = 0.01 µF (Vicor Part # 04872) C4 = 270 µF (Tant.
PAGE 10
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies LC Output Filter Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output C2a C3a L1 C1 +IN +OUT GATE IN GATE OUT –IN +S TRIM –S –OUT C4 C1 C2a – C2b C3a – C3b C4 L1 = = = = = 100 µF 4,700 pF 0.01 µF 270 µF 200 nH (Vicor Part # 01000) (Vicor Part # 04872) (Tant.
PAGE 11
9. EMC Considerations Design Guide & Applications Manual For VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies 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.