- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄364677 > AN-15 TOPSwitch Power Supply Design Techniques for EMI & Safety PDF資料下載
參數(shù)資料
| 型號： | AN-15 |
| 英文描述： | TOPSwitch Power Supply Design Techniques for EMI & Safety |
| 中文描述： | 的TOPSwitch電源電磁干擾設(shè)計(jì)技術(shù) |
| 文件頁數(shù)： | 7/36頁 |
| 文件大小： | 381K |
| 代理商： | AN-15 |
第1頁第2頁第3頁第4頁第5頁第6頁當(dāng)前第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁
A
6/96
AN-15
7
Typical AC Mains Input Voltage
Configurations
TOPSwitch
power supplies are typically connected to the AC
mains in either 2-wire or 3-wire configurations. For the purposes
of EMI design presented in this application note, 2-wire and 3-
wire configurations are now defined.
2-Wire AC Input
The
TOPSwitch
power supply 2-wire AC mains connection
may consist of one line wire and one neutral wire where the AC
mains neutral is eventually connected back to earth ground at a
local electrical panel. The 2-wire connection may also consist
of two separately phased line wires where neither is connected
directly to earth ground. The power supply SELV output may
or may not be connected directly to earth ground.
In this application note, the neutral wire will be treated as an
ungrounded AC mains or separately phased line conductor
requiring the same safety considerations as any AC mains line
conductor. In addition, the power supply SELV output return
will be assumed to connect directly to earth ground which
represents the worst case and most unfavorable connection for
safety considerations.
3-Wire AC Input
In 3-wire connections, the third wire earth ground wire will be
available for connection to EMI filter components, shields,
chassis, and enclosures. The neutral wire will be treated as an
ungrounded AC mains or separately phased line conductor
requiring the same safety considerations as any AC mains line
conductor. In addition, the power supply SELV output return
will be assumed to connect directly to earth ground which
represents the worst case and most unfavorable connection for
safety considerations.
EMI Filter Components
EMI filters are actually simple combinations of inductors or
chokes and capacitors. Series resistors, which lead to undesirable
power dissipation, are not normally used for reducing conducted
emissions.
Single-section EMI filters (one stage of common mode and
differential mode attenuation) take the least space and have the
lowest cost but require careful attention to details such as circuit
parasitics, component parasitics, and layout to meet the
specifications with adequate margin. Multiple-section filters
can also be used because one stage can be designed to overcome
the deficiencies of the other. The two section design will reduce
current emissions and increase margin below the specification
limit but may not address size or cost goals of the end product.
Understanding the basics of EMI filter design and application
allows the designer to implement small, low cost, single section
EMI filters.
PI-693-031592
Z
f
C
ESL
ESR
Z=
1
2
π
fC
Ideal
Z= 2
π
fESL
ESR
fr
Actual
Figure 9. Comparison of Ideal and Real Capacitor Impedance.
Capacitors
Proper capacitor selection for EMI filters requires attention to
three key parameters: impedance characteristics, voltage ratings,
and safety specifications.
Figure 9 shows impedance characteristics for ideal and non-
ideal capacitor behavior. An ideal capacitor has an impedance
characteristic that decreases linearly with frequency. A real
capacitor has parasitic inductance and resistance elements
which cause the impedance to behave quite differently from an
ideal capacitor.
Equivalent series inductance (ESL) creates a capacitor self
resonant frequency f
as shown on the plot. The impedance of
the capacitor at this self-resonant frequency is determined by
equivalent series resistance (ESR). Beyond the self-resonant
frequency (f
), the capacitor actually acts like an inductor.
Capacitors with plastic film, combination plastic film/paper, or
ceramic dielectrics usually have the highest self-resonant
frequencies and are commonly used in EMI filters.
Aluminum Electrolytic Energy Storage Capacitor
Switching power supplies always have a bridge rectifier and
high voltage bulk energy storage aluminum electrolytic capacitor
to convert AC mains input voltage to high DC bus voltage
(typically 100 to 400 Volts DC) shown as C
IN
in Figure 7.
The impedance of this capacitor, which must always be
minimized, provides the first level of differential mode conducted
emissions filtering.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AN-16 | TOPSwitch Flyback Design Methodology |
| AN-17 | Flyback Transformer Design for TOPSwitch Power Supplies |
| AN-18 | TOPSwitch Flyback Transformer Construction Guide |
| AN-19 | TOPSwitch Flyback Power Supply Efficiency |
| AN-20 | Transient Suppression Techniques for TOPSwitch Power Supplies |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AN1500-521P | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:AN0625-521P |
| AN1500A | 制造商:SAMES 制造商全稱:SAMES 功能描述:SINGLE CHIP TELEPHONE DEMO BOARD |
| AN15-02 | 制造商:SMC Corporation of America 功能描述:Silencer, Airline, 1/4PT Port 制造商:SMC 功能描述:Compact silencer Resin R1/4 |
| AN150210 | 制造商:AN# - MILITARY 功能描述: |
| AN150308 | 制造商:AN# - MILITARY 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。