LP34-3 [POWER-ONE]
Filter & Ring Core Chokes; 过滤器和环形铁芯电感
| 型号： | LP34-3 |
| 厂家： | 
POWER-ONE |
| 描述： | Filter & Ring Core Chokes |
| 文件： | 总5页 (文件大小：111K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Description
These Filters and chokes are designed to reduce input in-
terference and/or output ripple voltages occurring in appli-
cations with switched mode power supplies. Since all our
filters contain a Moly Permalloy Powder (MPP) ring core
they feature very low DC losses as well as high DC mag-
netisation and operate perfectly at the input and/or output
of switching regulators ensuring effective filtering even at
elevated DC current levels. These special characteristics
allow the chokes to be operated at DC currents which con-
siderably exceed the rated current, by accepting a corre-
sponding gradual loss of inductance (unlike ferrite core
chokes where inductance rapidly decreases above a cer-
tain DC magnetising level).
In applications where switching regulators have long supply
lines, filters and chokes are used in order to prevent oscilla-
tions caused by their negative input impedance. For further
information refer also to switching regulator data for "Option
L", and to section: Technical Information: Installation & Ap-
plication.
Table 1a: Type survey of FP filter blocks
Table 1b: Type survey ring core chokes
Filter type
Part No.
Matching switching
regulator type
Type
Part No.
Inductivity
ILn
Single Symm.
coil
coil
FP38
FP80
FP144
PSR 54
PSA 55
PSA 5A2
PSA 5A5
PSA 123
PSA 153
LP34-3
L20-7
34 µH
20 µH
20 µH
3 A
7 A
7 A
8 A
•
•
•
LP20-7
LP183 2 ∞ 183 µH
•
PSR 53
PSR 122.5
PSR 152.5
PSR 242
PSR 362
PSA 242.5
PSA 121.5
PSA 151.5
PSA 241.5
PSA 361
PSA 481
Filter Blocks FP Types
The filter blocks contain, in addition to a MPP ring core, a
capacitor and an attenuation resistor, capable of handling
the high ripple currents seen at the input of switching regu-
lators. This forms a complete external filter system opti-
mised to prevent oscillations and to reduce superimposed
interference voltages and currents, specially designed for
use in PCB applications together with switching regulators
in an A01 case size. For selection of filters refer to the type
survey.
Table of Contents
Page
Page
Description ....................................................................... 1
Filter Blocks FP Types ..................................................... 1
Low-Loss Ring Core Chokes L/LP-Series ....................... 3
Mechanical Dimensions ................................................... 5
REV. SEP 29, 2003
Page 1 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Electrical Data Filter Blocks
General Condition: TA = 25°C unless otherwise specified
Table 2: Filter blocks FP
Characteristics
Conditions
FP38
FP80
FP144
min
typ max
min
typ max
min
typ max
Unit
A DC
V DC
mý
IFn
Rated current
L = 0.75 Lo
4
4
2
UFn Rated voltage
TC min...TC max
5
40
5
80
15
90
144
RF
Lo
Ohmic resistance
18
20
34
22
38
18
20
34
22
38
95
100
112
95
No load inductance
IL = 0, TC min...TC max
30
30
88
100
µH
TA
TC
TS
Ambient temperature IF = IFn
Case temperature
–40
–40
–40
80
–40
–40
–40
80
–40
–40
–55
°C
92
92
98
Storage temperature
100
100
100
2
2
For currents IF > 4 A the following derating takes place: TA max = 100 – 1.3 • IF [°C], TC max = 100 – 0.49 • IF [°C]
Reduction of Output Ripple
Input Interference Reduction
Even though switching regulators have an inherently low
output ripple, certain sensitive applications need even fur-
ther reduction. In such cases, the filters designed to reduce
disturbances at the input, can also be used for reducing the
ripple on the output voltage (even better results with regard
to the ripple and dynamic control deviation can be achieved
by using low-loss ring core chokes in combination with an
external capacitor, see below).
An AC ripple current can be measured at the input of any
switching regulator, even if they are equipped with an input
filter. Depending on the types of filters used, common and/
or differential mode interferences can be reduced.They will
also help to further increase the surge and burst immunity
of the power supplies.
The FP filters considerably increase the source impedance
of the regulators superimposed interference, to a value
which is normally high in comparison to the impedance of
the source (ZLine). The interference currents are therefore
practically independent of their source impedance. The fil-
ter will reduce these currents by approximately 25 dB at a
frequency of 150 kHz.
The output ripple can be reduced by the use of filter blocks
by about 24 dB. The formula for the ripple uR at the load RL
is as follows:
uR = 0.063 • uo
(Ripple voltage uo is given for specific regulators in the cor-
responding data section).
The interference voltages at the filter input are due to the
remaining interference currents flowing through the source
impedance. The resulting interference voltage reduction
can be seen in the following figure. For frequencies above
the regulator switching frequency the attenuation will in-
crease (up to 2 MHz approx.).
Uio
Uii
12010
Vo+
Vi+
Filter
Gi
UR
U
RL
Uo
PSR
Gi–
Go–
Parallel operation: When several switching regulator inputs
are connected in parallel, each regulator should be
equipped with a separate input filter. Interconnections
should only be made in front of the filter or at its input Uii
(i. e. the central ground point should be before or at the filter
and under no circumstances at the regulator input).
Fig. 2
Reduction of voltage interference by FP filters
Consider, that the filter not only affects the output ripple but
can also influence the voltage across the load RL in the
event of load changes. The static load regulation increases
with the ohmic resistance of the choke i.e. 24 mV/A for the
FP 38 and FP 80 filters and 95 mV/A for the FP 144 filter.
inductive
resistive
Att. [dB]
capacitive
12009
40
30
20
10
0
ZLine [ ]
Fig. 1
0
1
3
2
4
6
5
Interference voltage reduction with FP filters at f = 150 kHz
Source impedance
REV. SEP 29, 2003
Page 2 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Typical Application
The example in figure Reduction of voltage interference by
FP filters shows a switching regulator operating from a bat-
tery (Ri < 0.5 Ω) with long supply lines (e.g. 2 m).The result-
ing superimposed interference voltage USL may be meas-
ured at the regulators input. The connection of a filter in
front of the power supply will reduce this interference ac-
cordingly:
2. This example shows, that with an inductive source im-
pedance of 3.8 Ω, the insertion of the filter results in an
interference voltage reduction of approx. 18 dB (see
fig.: Interference voltage reduction with FP filters at f =
150 kHz).
3. The original superimposed interference voltage will be
reduced by a factor of approx. 8:
1. The regulator's source impedance is mainly inductive
because of the low battery impedance and the long sup-
ply lines. It can be calculated as follows:
USF = USL • 10–18/20 [V]
2 • l
Uio
Uii
12011
Vo+
Go–
Vi+
Gi–
l ZLine l ≅ 2 π • fS • LLine • 2 l
l ZLine l ≅ 2 π • (150 • 103) • 10-6 • 2 • 2 ≅ 3.8 Ω
Filter
Us
ZLine
RL
Uo
U
PSR
Gi
fS:
Switching frequency (150 kHz)
LLine : Supply line inductance (typically 1µH/m)
Fig. 3
l :
Length of single supply line (twice for posi-
tive and negative path)
Reduction of voltage interference by FP filters
Low-Loss Ring Core Chokes L/LP-Series
L/Lo [%]
The ring core chokes, in combination with a capacitor, may
easily be used for application specific LC filters at the input
or output of switched mode power supplies. All chokes are
suitable for PCB mounting. They are either moulded into
plastic cases or isolated from the PCB by means of an iso-
lation pad.
12012
100
LP183
80
75
LP34-3
60
Series L/LP20-7 and LP34-3 are intended for use as differ-
ential mode filters and the current compensated choke
LP183 enables attenuation of common mode interference.
L/LP20-7
I
I
40
20
0
Fig. 4
Choke inductance versus current
IL [A]
0
2
3
4
6
7
8
10
12
14
Electrical Data Ring Core Chokes
General Condition: TA = 25°C unless otherwise specified
Table 3: Ring core chokes
Characteristics
Conditions
L20-7/LP 20-7
LP34-3
LP183
min
typ max
min
typ max
min
typ max
Unit
ILn
RL
Lo
Rated current 1
L = 0.75 Lo
7
3
8
A DC
mý
Ohmic resistance
5
5.5
20
6
18
30
20
34
22
38
2×2.9 2×4.2 2×5.5
2×95 2×183 2×245
0.19
No load inductance
IL = 0, TC min...TC max
18
22
µH
DTI Current specific case
0.082
0.68
K/A2
temp. increase 1
TA
TC
TS
Amb. temperature 1
Case temperature
Storage temperature
IL = ILn
–40
–40
–40
106
110
110
–40
–40
–40
104
110
110
–40
–40
–40
98
°C
110
110
1 If the choke is not operating at the rated current ILn, the maximum ambient temperature TA max and the maximum direct current IL max
change according to the following equations:
TC max –TA max
2
IL max
=
TA max = TC max – IL max • DTI
DTI
REV. SEP 29, 2003
Page 3 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Reduction of Output Ripple
Input Interference Reduction
Even though switching regulators have an inherently low
output ripple, certain sensitive applications need even fur-
ther reduction. In such cases, the low-loss ring core chokes
designed to reduce disturbances at the input can also be
used for reducing the ripple on the output voltage. The
chokes in combination with an external capacitor can
achieve even better results than the Filter Blocks with re-
gard to the ripple and dynamic regulation.
Using L- or LP-series chokes together with an additional
external capacitor a similar attenuation can be achieved as
with filter blocks. The capacitor between the choke and the
converter input is necessary in order to avoid possible oscil-
lations caused by the negative input impedance of the regu-
lator. This phenomenon could cause the input voltage to
leave the specified regulator input range. The relatively
high ripple current flowing through the capacitor must be
considered for the design. Refer also to: Technical Informa-
tion: Installation & Application.
The formula for the remaining output ripple at the load RL is
calculated as follows:
The current compensated choke LP183 has a high perme-
ability ring core with two identical separate windings. The
normal operating current will only see the small stray in-
ductance between the windings. However common mode
interference will be blocked by the full inductance of the
UR = uo • ZC ext/ZLD
uo:
Output ripple of the regulator
ZCex
:
The impedance of the capacitor at the regu-
lator's switching frequency (150 kHz) corre-
sponds to the equivalent series resistance
(ESR) of the capacitor (please refer to the
corresponding data sheet).
choke.
LP34-3 or
LP183 L/LP20-7
12013
Vo+
Go–
Vi+
Gi–
ZLD = 2 π • fS • LD
fS:
150 kHz (regulator switching frequency)
U
Uo
RL
PSR
Through the use of a common mode choke LP 183, the
common mode noise at the output can also be further re-
duced.
Cext 1
Cext 3
Cext 2
Fig. 5
Consider that the filter not only affects the output ripple but
can also influence the voltage UR across the load RL in the
event of load changes. The static regulation increases with
the ohmic resistance of the choke, i.e. 6 mV/A for the choke
L/LP20-7 and 20 mV/A for the LP34-3.
L/LP type chokes and capacitors used as input filter
Typical Application
A voltage drop UrGo = rGo • (Io – Ii) is produced across the
ground loop resistance rGo. It is superimposed upon the
regulators output voltage Uo and generates the voltage UR
= Uo – Ur Go across the load resistance RL. Without an input
inductance Le the current Ii in the input circuit has a rela-
tively high AC component with a basic frequency fs (regula-
tor's switching frequency of approx. 150 kHz).This alternat-
ing current produces an AC voltage component across rGo
The dynamic regulation is dependent on the size of the ca-
pacitor. Generally, the bigger Cex the smaller is the dy-
namic, however, recovery will be slower.
LD ZLD ZC ext
RD
12014
Vo+
Go–
Vi+
which is superimposed upon URL
.
U
UR
PSR
Uo
RL
Ce
To prevent this phenomenon, an inductance Le can be in-
serted into the input circuit. This causes the AC component
of the input current to be supplied entirely from the input
capacitor Ce; thus, Ii is a pure direct current. Ce should be
wired as close as possible to the regulator's input terminals
Vi+ and Gi–.
Gi–
Fig. 7
Low-loss ring core choke with external capacitor (Cex
approx. 1000 µF) used as output filter
Le and Ce additionally provide protection against input tran-
sients and reduce radio interference voltages.
External connection of Gi– and Go– or connection via a
common ground is not recommended. The internal voltage
drop UrG in the regulator would be superimposed on the
output voltage.
12015
Io
Vo+
Vi+
Le
PSR
UrG
RL
U
URL
Uo
Ce
Gi–
Go–
rG
Fig. 6
rGo
Reduction of superimposed interference voltages in
UrGo
grounded power supply systems, caused by ground loops
REV. SEP 29, 2003
Page 4 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Mechanical Dimensions
Dimensions in mm. Tolerances ±0.2 mm unless otherwise specified
European
Projection
16.6 ±1
22 ±1
6.8 ±1
25 ±0.5
ø 3.8
4
3
min. 4.5
1
2
4
b
b
3.22 ±0.5
1
(3.22)
Legend: b = 5.08 mm
1 = Uii (input)
2 = Uio (output)
3 = Gi (ground)
4 = Positioning pins
0.8
Fig. 8
Filter blocks FP weight 30 g
27
38.1
47.5
Fig. 9
Differential mode choke L20-7, weight 30 g
M 2.5
ø 0.8
ø 1
max 8
ø 0.9
5.08
7.6
2 x 5.08
17.5
13.2
7.5
Fig. 10
Differential mode choke LP34-3, weight 7 g
Fig. 11
Common mode choke LP183, weight 7 g
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life support systems, equipment used in hazardous environments, or nuclear control systems without the express
written consent of the respective divisional president of Power-One, Inc.
TECHNICAL REVISIONS - The appearance of products, including safety agency certifications pictured on labels, may
change depending on the date manufactured. Specifications are subject to change without notice.
REV. SEP 29, 2003
Page 5 of 5
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