DC-DC转换器设计与应用手册

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"DC-DC 设计指南，涵盖了高密度DC-DC转换器技术、控制引脚功能与应用、设计要求、电磁兼容性考虑、功率阵列中的电流共享、热性能信息、附件模块如Autoranging Rectifier Module (ARM)、Filter/Autoranging Rectifier Module (FARM)等，以及各种军用COTS滤波输入衰减器模块和输出纹波衰减器模块。此外，还包含了推荐的焊接方法（锡铅和无铅）以及表面贴装插座系统和通孔插座安装系统的信息。" 本指南深入探讨了DC-DC转换器的设计与应用，特别是Maxi, Mini, Micro家族的转换器和附件模块。首先，高密度DC-DC转换器技术部分介绍如何在有限的空间内实现高效能和高功率密度，这对于现代电子设备的紧凑化至关重要。控制引脚功能与应用章节则详细阐述了如何利用这些引脚来调整和优化转换器的工作状态。设计要求部分，讨论了在选择和设计DC-DC转换器时应考虑的关键因素，包括电压、电流、效率、稳定性以及负载调节。电磁兼容性（EMC）是电子设备设计中不可忽视的一环，本指南提供了关于减少电磁干扰和确保系统稳定运行的建议。电流共享在功率阵列中的实现是多电源系统设计的重要一环，该部分解释了如何使多个转换器模块协同工作，以确保负载电流的均匀分配。热性能信息章节则关注转换器的散热问题，提供热管理和冷却策略以确保长期稳定运行。附件模块部分详细介绍了各种功能模块，如ARM用于自动范围调整，FARM结合滤波和范围调整，ENMod构建模块化交流前端系统，而HAM则提供了高提升功能。滤波输入衰减器模块如FIAM和M-FIAM系列专为军用标准设计，用于降低输入噪声。MicroRAM则是针对微小尺寸应用的输出纹波衰减器。最后，焊接方法和插座系统部分为制造商提供了指导，包括符合RoHS标准的无铅焊接技术和传统的锡铅焊接技术，以及Surface Mount Socketing System (SurfMate) 和 Through-hole Socket-mount System (InMate) 的安装方法，确保了转换器模块在生产过程中的可靠性和可维护性。这些详尽的指导对于任何涉及DC-DC转换器设计和应用的工程师来说都是宝贵的参考资料。

vicorpower.com 800-735-6200 Applications Engineering 1-800-927-9474 Rev. 1.2

Page 13 of 80

3. Design Requirements

To calculate the required source impedance, use the

following formula:

Z = 0.1(V

LL)

/ Pin

where: Z is required input impedance

VLL is the low line input voltage

in is the input power of the module

Filters, which precede the module, should be well damped

to prevent ringing when the input voltage is applied or

the load on the output of the module is abruptly changed.

INPUT TRANSIENTS AND SURGES

The voltage applied to the input of the module must not

exceed the ratings outlined in the data sheet. Protection

devices such as Zener diodes and MOVs should be used

to protect the module from short-duration transients.

These shunt protection devices are effective only if the

source impedance is high relative to the impedance of

the protection device when it is conducting. For voltage

surges where the abnormal voltage is present for a long

period of time, shunt protection devices can easily be

damaged by the power dissipated. For this type of

condition, a voltage limiter in series with the input of

the module may be the best solution. Vicor Applications

Engineering can assist in recommending the appropriate

type of protection for the module.

SENSE LEADS (Mini and Maxi only)

The sense leads of the module must always terminate

either directly to the output pins (local sense) or at the

load (remote sense). When remote sense is used, the

output wiring impedance in combination with the load

impedance can cause significant loss of phase margin and

result in oscillation and possible damage to the module,

poor transient response, or activation of the output

overvoltage protection. Long sense leads may require a

compensation circuit for stability.

Protection circuitry is required if the possibility of reversed

sense leads can occur. Please contact Vicor Applications

Engineering for specific recommendations.

Do not

exceed 1 V between –S and –Out leads. This is

an important consideration if the converter is used in a

Hot-Swap application. ORing diodes, if used, should be

located in the +Output lead to avoid exceeding this rating.

Do not

exceed the rated power of the converter. The total

of the power consumed by the load plus the power lost in

conductors from the converter to the load must be less

than the output power rating of the converter.

OUTPUT CONNECTIONS

For systems designed to charge batteries, subject the

module output to dynamic loading, or loads that have

large reactive components, please contact Vicor

Applications Engineering to discuss your application

in detail.

Do not

externally drive the output of the module 10%

above its nominal setpoint voltage.

Modules, that are used to charge batteries should be

applied with a diode in series with the output of the

module. The charge current must be externally controlled

to ensure that the module is not operated in excess of its

power or current rating.

Current-carrying conductors should be sized to minimize

voltage drops.

Do not

use output ORing diodes with parallel arrays of

the Micro Family converters.

Output Overvoltage Protection (OVP). The OVP detection

circuitry within the converter is highly resistant to false

tripping. For the converter to shut down due to an OVP

condition two conditions must be satisfied (logical AND);

1. The voltage at the output terminals must be greater

than the OVP set point.

2. The secondary control IC within the converter must be

requesting a power conversion cycle from the internal

primary control IC.

By using this logic, false tripping of individual converters

due to externally induced OVP conditions such as load

dumps or, being driven by external voltage sources at the

output terminals is minimized. The user should not test

the OVP circuit by back driving the output terminals or by

any other means as the OVP circuitry is fully tested as part

of the inline manufacturing process.

OVERCURRENT PROTECTION

The Maxi, Mini, Micro converters incorporate a straight-

line type current limit. (Figure 3–1) As output current is

increased beyond Imax, the output voltage remains

constant and within its specified limits up to a point, I

KNEE,

which is typically 5 – 25% greater than rated current,

Imax. Beyond IKNEE, the output voltage falls to Ishortcircuit.

Typically, modules will automatically recover after the over-

current condition is removed.

vicorpower.com 800-735-6200 Applications Engineering 1-800-927-9474 Rev. 1.2

Page 14 of 80

3. Design Requirements

MAXIMUM OUTPUT CAPACITANCE

In general, adding external capacitance to the Maxi, Mini,

and Micro’s output is not required. However, it is often

common practice with power supply designs to add external

capacitance to the converter output for attenuation of

output ripple and / or improving dynamic load performance.

The Maxi, Mini, Micro converters typically have a faster

response to dynamic loads than other power solutions;

hence, external capacitors may not be necessary. In addition,

the output ripple and noise specification listed on the data

sheet may be acceptable for many applications.

A general equation for determining the maximum recom-

mended output capacitance is as follows:

out

(400x10

)

C(farad) =Vout

Vout

where: Pout is the output power of the converter

out is the nominal output voltage of the converter

The capacitance value is not the absolute maximum value,

but the value for which general application of the converter

can be deemed appropriate. Testing will be required to

ensure that the module is stable if this value is exceeded.

Approximately 10X the value calculated will cause the

converter to go into current limit at turn-on.

CAUTION:

If exceeding this value, it is recommended

that Vicor Applications Engineering be consulted.

ABSOLUTE MAXIMUM RATINGS

Please consult the latest module data sheets available on

the Vicor website for maximum ratings concerning pin-to-

pin voltages, isolation, temperature, and mechanical ratings.

GROUNDING OF BASEPLATE AND REFERENCING

OF INPUT AND OUTPUT TERMINALS

The baseplate of the converter should always be connected

to earth ground. If for any reason this is not possible in

your application please consult with Vicor Applications

Engineering for acceptable alternatives for your application.

The input and output leads of the converter should be

referenced to the baseplate at some point to avoid stray

voltages. For offline applications the input leads are often

referenced to earth ground at the AC source ahead of the

bridge rectifier. Either + or –Output terminal may be

referenced to earth ground and the baseplate. “Floating”

inputs or outputs should at a minimum have a high-

resistance divider to bleed off stray charges to avoid

damage to the insulation system.

HIGH FREQUENCY BYPASSING

All Vicor converters must be bypassed for proper operation.

(Figure 3–2) The minimum complement of high-frequency

bypass capacitors must consist of the following:

• 0.2 µF ceramic or film type connected between

+In and –In.

• 4.7 nF Y-capacitor between +In and baseplate

and –In and baseplate.

• 10 nF ceramic or film capacitor between +Out and

baseplate and –Out and baseplate.

All applications utilizing Maxi, Mini, Micro converters

should be properly bypassed, even if no EMC standards

need to be met. Bypass Vin and Vout pins to each module

baseplate as shown in Figure 3–2. Lead length should

be as short as possible. Recommended values vary

depending on the front end, if any, that is used with the

modules, and are indicated on the appropriate data sheet

or application note. In most applications, C1 is a 4,700 pF

Y-capacitor (Vicor P/N 01000) carrying the appropriate

safety agency approval; C2 is a 4,700 pF Y-capacitor (Vicor

P/N 01000) or a 0.01 µF ceramic capacitor rated at 500 V.

In PC board applications, each of these components is

typically small enough to fit under the module baseplate

flange. For PCB mounting of the module. Please refer to

Figures 3–3 and 3–4.

out

KNEE

MAX

SHORT CIRCUIT

out

Figure 3–1 — Typical Maxi, Mini, Micro current limiting

vicorpower.com 800-735-6200 Applications Engineering 1-800-927-9474 Rev. 1.2

Page 16 of 80

4. EMC Considerations

All switching power supplies generate potentially interfer-

ing signals as a result of high-frequency, high-power

switching. The Vicor power converter topology, to a large

extent, addresses the problem at the source by the use of

a quasi-resonant, zero-current switching (ZCS) and zero-

voltage switching (ZVS) topology. The switching current

waveform is a half sine wave that generates far less

conducted and radiated noise in both frequency spectrum

and magnitude. EMI filtering, if properly designed and

implemented, reduce the magnitude of conducted noise

an additional 40 – 60 dB, and as a result, the noise radiated

by the power conductors is reduced proportionally.

Conducted noise on the input power lines can occur as

either differential-mode or common-mode noise currents.

Differential-mode noise, largely at low frequencies, appears

across the input conductors at the fundamental switching

frequency and its harmonics. Common-mode noise, which

has mostly high-frequency content, is measured between

the converter’s input conductors and ground.

The Vicor power converter being an electronic device may

be susceptible to high levels of conducted or radiated

emissions. It is the responsibility of the user to assess

testing protocols in order to determine applicability of the

converter in the intended application.

1. Keep current loops small. The ability of a conductor to

couple energy by induction and radiation is reduced

accordingly.

2. For conductor pairs, use wide (low Z) copper traces

aligned above and below each other.

3. Locate filters at the source of interference; i.e., close

to the power converter(s).

4. Filter component values should be chosen with

consideration given to the desired frequency range of

attenuation. For example, capacitors are self-resonant

at a certain frequency, beyond which they look inductive.

Keep bypass capacitor leads as short as possible.

5. Locate components on the PCB with consideration

given to proximity of noise sources to potentially

susceptible circuits. For example, the FIAM is an input

line filter module that has been optimized for use

with Maxi, Mini, and Micro DC-DC converters. When

used in conjunction with the recommended external

components and layout, it will significantly reduce the

differential and common-mode noise returned to the

power source. The FIAM meets the requirements of

EN55022 “B”, FCC “B”, and Bellcore GR-001089-

CORE, Issue 2 when used with any combination of

Maxi, Mini, and Micro converters up to the FIAM’s

maximum rated current.

DC-DC converter inputs and outputs must be properly

bypassed, to system chassis or earth. Bypass Vin and Vout

pins to each DC-DC module baseplate. Capacitor lead

length must be as short as possible. (Figure 4–1)

EMI filtering can be application dependent. A packaged

filter module may not always be the appropriate solution,

and the general practice of bypassing Vin and Vout may

not produce optimal results. You may have to adjust the

values depending on the severity of common-mode and

differential-mode noise. (Figures 4–2 and 4–3)

Input transient suppression should be used in applications

where source transients may be induced by load changes,

blown fuses, etc. The level of transient suppression

required will depend on the expected severity of the tran-

sients. A Zener diode, TRANSORB™, or MOV will provide

transient suppression, act as a voltage clamp for DC input

spikes, and provide reverse input voltage protection. The

device voltage rating should be chosen above high-line

voltage limits to avoid conducting during normal

operation which would result in overheating.

Module shields that provide shielding around the belly

(label side) of the Maxi, Mini, Micro are also available for

applications that are highly noise sensitive. Module shield

information is available on the Vicor website, see links

provided, on the following page.

FILTERING AND TRANSIENT PROTECTION

BASIC GUIDELINES FOR SUCCESSFUL EMI FILTERING

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