Power-One LP34-3 Filter & ring core choke Datasheet

Accessories
Filter & Ring Core Chokes FP, L and LP Series
Description
These Filters and chokes are designed to reduce input interference and/or output ripple voltages occurring in applications 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 magnetisation 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 considerably exceed the rated current, by accepting a corresponding gradual loss of inductance (unlike ferrite core
chokes where inductance rapidly decreases above a certain DC magnetising level).
In applications where switching regulators have long supply
lines, filters and chokes are used in order to prevent oscillations caused by their negative input impedance. For further
information refer also to switching regulator data for "Option
L", and to section: Technical Information: Installation & Application.
Table 1a: Type survey of FP filter blocks
Table 1b: Type survey ring core chokes
Filter type
Part No.
Matching switching
regulator type
Type
Inductivity
Part No.
FP38
PSR 54
PSA 55
PSA 5A2
PSA 5A5
PSA 123
PSA 153
LP34-3
34 µH
3A
•
L20-7
20 µH
7A
•
LP20-7
20 µH
7A
•
LP183
2 ∞ 183 µH
8A
FP80
PSR 53
PSR 122.5
PSR 152.5
PSR 242
PSR 362
PSA 242.5
FP144
PSA
PSA
PSA
PSA
PSA
ILn
Single Symm.
coil
coil
•
121.5
151.5
241.5
361
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 regulators. This forms a complete external filter system optimised to prevent oscillations and to reduce superimposed
Table of Contents
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.
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
min
FP38
typ max
min
FP80
typ max
min
FP144
typ max
IFn
Rated current
L = 0.75 Lo
UFn
Rated voltage
TC min...TC max
RF
Ohmic resistance
18
Lo
No load inductance
IL = 0, TC min...TC max
30
TA
Ambient temperature
IF = IFn
–40
TC
Case temperature
–40
92
–40
92
–40
98
TS
Storage temperature
–40
100
–40
100
–55
100
4
5
4
40
5
20
22
18
34
38
30
80
–40
2
80
15
20
22
90
34
38
88
80
–40
Unit
A DC
144
V DC
95
100
mý
100
112
µH
95
°C
For currents IF > 4 A the following derating takes place: TA max = 100 – 1.3 • IF2 [°C], TC max = 100 – 0.49 • IF2 [°C]
Input Interference Reduction
Reduction of Output Ripple
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.
Even though switching regulators have an inherently low
output ripple, certain sensitive applications need even further 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).
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 filter will reduce these currents by approximately 25 dB at a
frequency of 150 kHz.
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 increase (up to 2 MHz approx.).
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).
inductive
resistive
capacitive
Interference voltage reduction
Att. [dB]
40
12009
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 corresponding data section).
Vo+
Vi+
U
Uo
PSR
Gi–
Uii
Filter
Uio
Gi
12010
UR
RL
Go–
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.
30
20
10
Z Line [ ]
0
0
1
REV. SEP 29, 2003
3
2
4
Source impedance
5
6
Fig. 1
Interference voltage reduction with FP filters at f = 150 kHz
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 battery (Ri < 0.5 Ω) with long supply lines (e.g. 2 m). The resulting superimposed interference voltage USL may be measured at the regulators input. The connection of a filter in
front of the power supply will reduce this interference accordingly:
2. This example shows, that with an inductive source impedance 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 supply lines. It can be calculated as follows:
USF = USL • 10 –18/20 [V]
2•l
Uii
l ZLine l ≅ 2 π • fS • LLine • 2 l
l ZLine l ≅ 2 π • (150 • 103) • 10-6 • 2 • 2 ≅ 3.8 Ω
Us ZLine
U
fS :
Switching frequency (150 kHz)
LLine : Supply line inductance (typically 1µH/m)
l:
Length of single supply line (twice for positive and negative path)
Uio
Filter
12011
Vo+
Vi+
Gi–
RL
Uo
PSR
Gi
Go–
Fig. 3
Reduction of voltage interference by FP filters
Low-Loss Ring Core Chokes L/LP-Series
12012
100
LP183
80
75
LP34-3
60
L/LP20-7
ILn
Series L/LP20-7 and LP34-3 are intended for use as differential mode filters and the current compensated choke
LP183 enables attenuation of common mode interference.
L /Lo [%]
ILn
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 isolation pad.
40
20
Fig. 4
Choke inductance versus current
0
0
2
3
4
6
7 8
10
12
14
IL [A]
Electrical Data Ring Core Chokes
General Condition: TA = 25°C unless otherwise specified
Table 3: Ring core chokes
Characteristics
Conditions
1
L20-7/LP 20-7
min
typ max
L = 0.75 Lo
min
LP34-3
typ max
min
LP183
typ max
ILn
Rated current
RL
Ohmic resistance
Lo
No load inductance
D TI
Current specific case
temp. increase 1
TA
Amb. temperature 1
–40
106
–40
104
–40
98
TC
Case temperature
–40
110
–40
110
–40
110
TS
Storage temperature
–40
110
–40
110
–40
110
IL = 0, TC min...TC max
7
3
8
A DC
5
5.5
6
18
20
22
2×2.9 2×4.2 2×5.5
mý
18
20
22
30
34
38
2×95 2×183 2×245
µH
0.19
K/A2
0.082
IL = ILn
Unit
0.68
1 If
°C
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
IL max =
TA max = TC max – IL2 max • D TI
D TI
REV. SEP 29, 2003
Page 3 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Input Interference Reduction
Reduction of Output Ripple
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 oscillations caused by the negative input impedance of the regulator. 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 Information: Installation & Application.
Even though switching regulators have an inherently low
output ripple, certain sensitive applications need even further 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 regard to the ripple and dynamic regulation.
The current compensated choke LP183 has a high permeability ring core with two identical separate windings. The
normal operating current will only see the small stray inductance between the windings. However common mode
interference will be blocked by the full inductance of the
choke.
LP183
LP34-3 or
L/LP20-7
U
12013
Vo+
Vi+
Uo
PSR
Cext 1
Cext 2
Cext 3
Gi–
RL
Go–
Fig. 5
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 relatively high AC component with a basic frequency fs (regulator's switching frequency of approx. 150 kHz). This alternating current produces an AC voltage component across rGo
which is superimposed upon URL.
To prevent this phenomenon, an inductance Le can be inserted 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–.
The formula for the remaining output ripple at the load RL is
calculated as follows:
UR = uo • ZC ext/ZLD
uo :
Output ripple of the regulator
ZCex: The impedance of the capacitor at the regulator's switching frequency (150 kHz) corresponds to the equivalent series resistance
(ESR) of the capacitor (please refer to the
corresponding data sheet).
ZLD = 2 π • fS • LD
fS:
150 kHz (regulator switching frequency)
Through the use of a common mode choke LP 183, the
common mode noise at the output can also be further reduced.
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.
The dynamic regulation is dependent on the size of the capacitor. Generally, the bigger Cex the smaller is the dynamic, however, recovery will be slower.
RD
PSR
Gi–
ZLD
ZC ext
12014
Vo+
Vi+
U
LD
Uo
Ce
UR
RL
Go–
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 transients 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
Le
U
PSR
Ur G
Ce
Gi–
rG
Uo
RL
URL
Go–
rGo
REV. SEP 29, 2003
Io
Vo+
Vi+
Ur Go
Fig. 6
Reduction of superimposed interference voltages in
grounded power supply systems, caused by ground loops
Page 4 of 5
Accessories
Filter & Ring Core Chokes FP, L and LP Series
Mechanical Dimensions
European
Projection
7.5 ±1
ø 3.8
3.6
b
(3.22)
4
13.7
6
b
3.66
b
30
15.24
12017
0.9 x 0.56
3.22 ±0.5
10.16
1
4
Legend: b = 5.08 mm 1
1 = Uii (input)
2 = Uio (output)
3 = Gi (ground)
4 = Positioning pins
22 ±1
3
2
ø1.3 ±1
37.8 ±0.5
min. 4.5
4
12016
16.6 ±1
6.8 ±1
M 2.5
25 ±0.5
(3.66)
Dimensions in mm. Tolerances ±0.2 mm unless otherwise specified
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
max 8
5.08
max 14.5
ø1
12019
ø 0.8
5 ±1
1
10
12018
M 2.5
3 –0.5
ø 0.9
2 x 5.08
17.5
Fig. 10
Differential mode choke LP34-3, weight 7 g
7.6
13.2
5.08
7.5
Fig. 11
Common mode choke LP183, weight 7 g
NUCLEAR AND MEDICAL APPLICATIONS - Power-One products are not authorized for use as critical components in
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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