technical guide

Conductive Polymer Aluminum Solid Capacitors
2015-01
2
Area of Application of OS-CON
Precautions when using OS-CON in circuits
1. Explanation of the rush current suppression methods
3
2. Example of rush current suppression methods
4
3. Sudden discharge current suppression
5
4. Precautions when connecting an OS-CON and an aluminum electrolytic capacitor in parallel
6
Application
7-15
1. Voltage reduction capability of OS-CON
2. OS-CON high speed back-up performance(Back-up capacitor for dynamic load)
3. Influence of output ripples from switching power supply on actual images
16-18
19
4. OS-CON equivalent circuit model
20-22
5. Application to low-pass filter circuits
23-24
6. Application of switching power supply for smoothing capacitor
25-29
Capacitors Selection Sheet
30
About this note
䕔The performance, characteristics, and features of the products described in this note are based on the products working alone under prescribed conditions. Data listed here is not
intended as a guarantee of performance when working as part of any other product or device. In order to detect problems and situations that cannot be predicted beforehand by
evaluation of supplied data, please always perform necessary performance evaluations with these devices as part of the product that they will be used in.
䕔This TECNICAL NOTE may change without prior notice.
䕔Unauthorized duplication of this note in part or in whole is forbidden.
industrial.panasonic.com/
Area of Application of OS-CON
Conductive Polymer Aluminum Solid Capacitors
Area of Application of OS-CON
Vout
Vin
Smoothing Capacitor in
Power Supply Circuit
In order to reduce line impedance in circuit
designing, various capacitors such as OS-CON
are widely used as backup capacitors and
bypass capacitors.
Among them, OS-CON characterized with its
extra-low ESR can replace general electrolytic
capacitors, offering a smaller mounting area, and
serves greatly to reduce ripple noise in a
smoothing circuit of a switching power supply,
which is the most commonly used power supply.
Capacitor in Filter Circuit
OS-CON is also useful in a filter circuit for
reducing noise that tends to occur with
miniaturizing and digitalizing of electronic
systems.
In addition, OS-CON has small characteristics
Backup Capacitor
Bypass Capacitor
IC
change by temperature. Therefore, in various
environments, OS-CON realizes stable operation.
These advantages of OS-CON lessen
noise-related troubles, and contribute greatly to
shortening of circuit designing period and
miniaturizing of electronic systems.
2
Precautions when using OS-CON in circuits
Conductive Polymer Aluminum Solid Capacitors
1. Explanation of the rush current suppression methods
When the OS-CON is used in the following circuit as figure 1, a rush current may flow because the ESR is extremely small. Maintain the rush current at 10A or less.
If as long as 10 times of the allowable ripple current of the OS-CON exceeds 10A, reconfigure so that the ripple current does not exceed 10 times.
1-1. DC-DC converter input circuits
(a) DC-DC converter circuits are usually a PCB block shape and use a
low ESR capacitor in the input section for high performance and
miniaturization.
(b) Consideration must be given to the rush current that flows from the
equipment when the DC-DC converter is adjusted and inspected.
䈜There is the possibility that an extremely large amount of a rush current will flow through the
OS-CON during voltage adjustment or inspection of the DC-DC converter‘s circuit block
when the power impedance supplied from the equipment being adjusted or inspected is
exceedingly low and the current suppression function of the current limiter and such is
provided. (Refer to Figure 1)
䈜A rush current suppression measures must be taken for DC-DC converter adjustment and
inspection equipment.(Refer to P. 13)
1-2. Circuits driven by chargeable batteries
(a) Circuit power lines equipped with batteries or rechargeable batteries use
capacitors such as the OS-CON with extremely low ESR to increase
performance and facilitate miniaturization.
Inductance coil
䈜There is the possibility of an extremely large amount of a rush current flowing through
the low ESR capacitors arranged along the power line when the power is turned on
for circuits driven by nickel cadmium chargeable batteries etc. that have a very low
internal resistance.(Refer to Figure 1.)
䈜A protection circuit like that is shown left is usually used to suppress rush current of charging
battery.
Direction of current flow
Diode for absorbing counter electromotive force
䈜The main points.
The peak current value of the diode when absorbing counter electromotive force.
1-3. A rush current without protection resistor
:KHQWKHUHLVQRSURWHFWLRQUHVLVWRU=DVVKRZQLQ)LJXUHDQGWKHSRZHUVXSSO\KDV5HQHDUO\ ȍ7KHOS-CON rush current is as
follows.
Supplied DC voltage (E)
A rush current (A) =
(655H=ȍ
Example : For 25SVPD10M
(65 PȍRUOHVVDQG䠋Supplied DC voltage=20V,
20V
= 300A or more
OHVVWKDQȍ
Fig. 1
Z (Protection resistor)
Capacitor
Power supply
internal resistance Re
ESR
Capacitance
Load
resistance
Power supply
voltage E
3
Precautions when using OS-CON in circuits
Conductive Polymer Aluminum Solid Capacitors
2. Example of rush current suppression methods
2-1. Resistor method
R
2-2. Resistor and relay method
Resistor for current suppression
Relay contact
Capacitor
Power supply
internal resistance
Re
Power supply
voltage E
Capacitor
R
ESR
Power supply
internal resistance
Re
Power supply
voltage E
Capacitance
ESR
Relay coil
Capacitance
(a) Rush current is as shown below.
E (V)
Re+ESR+R (ȍ)
Rush current (A) =
(b) Rush current is usually determined mainly by R as Re and ESR are low.
(c) Although the current is simply and clearly suppressed with this method, resister
R for suppressing current causes the voltage to drop.
2-3. Resistor and MOS-FET method
(a) A rush current is exactly the same as in the resistor method. There is almost no
voltage drop caused by the current suppression resistor from the time the relay
contact goes on.
(b) Note: After the capacitor has finished recharging, it may take some time or
setting of voltage to turn the relay ON.
2-4. Power thermistor
Power thermistor
R
Capacitor
Re
Power supply
voltage E
Capacitor
ESR
Re
MOS-FET
Capacitance
(a) Resistor method is exactly the same to using suppressed resistor R to suppress
a large current rush. There is almost no voltage drop caused by suppressed
resistor after MOS-FET is on.
(b) Note: As with the resistor and relay method, after the capacitor has finished
recharging, it may take some time or setting of voltage to turn the MOS-FET ON.
Power supply
voltage E
ESR
(a) Taking
Capacitance
an example of a
common power thermistor,
the value is 8ȍ at 25䉝, but
becomes 0.62ȍ at 130䉝.
(b) When the power thermistor is connected as shown in the above diagram, rush
current is suppressed due to the large resistor value at the moment the switch is
turned on. The output loss (voltage drop) is reduced after this.
(c) The power thermistor has a heat constant, meaning that the large resistor value
in the initial state cannot be regained the moment the switch is turned off. As a
result, the ability to suppress current is lost when the switch is turned off and on
quickly.
4
Precautions when using OS-CON in circuits
Conductive Polymer Aluminum Solid Capacitors
3. Sudden discharge current suppression
OS-CON has an exceedingly low ESR. When the load impedance during discharge is extremely low, there is the chance that it allows a large amount of discharge
current to flow for an instant.
7KHUHLVWKHFKDQFHDQH[WUHPHO\ODUJHDPRXQWRIGLVFKDUJHFXUUHQWZLOOIORZZKHQHOHFWULFFKDUJHLVGLVFKDUJHGZLWKȍORDGLQJ
䈜The discharge equivalent circuit is as shown to the left.
䈜The formula for estimating discharge current is given below.
Protection resistor
Z1
Capacitor
ESR
Z2
Load
circuit
Discharge current (A) =
Charging voltage (V)
(65==ȍ
Capacitance
Example : For 25SVPD10M
Ɣ
(65 PȍRUOHVV
Ɣ
Charging voltage=20V
Ɣ
== ȍ
Discharge current (A) =
is set, then
Charging voltage 20V
(65ȍRUOHVV
= 300A or more
When the OS-CON is to be used in sudden discharge operations, configure the circuit so that the peak discharge current becomes 10A or less, using the above
mentioned rough estimate expression as a guide. However, if 10 times the allowable ripple current of the OS-CON exceeds 10A, reconfigure so that 10 times the
allowable ripple current is not exceeded.
5
Precautions when using OS-CON in circuits
Conductive Polymer Aluminum Solid Capacitors
4. Precautions when connecting an OS-CON and an aluminum electrolytic capacitor in parallel
Aluminum electrolytic capacitors and OS-CON are often connected in parallel to improve circuit density an cost performance of ripple absorbing capacitors as follows.
Fig.1
lr
(a) Ripple current flowing through each parallelly
connected capacitor can be found by using the
values symbolized in the reference equivalent
circuit in Figure 1.
(b) The equivalent circuit in Figure 1 can be simplified
as shown in Figure 2 when it is to be used for
frequencies between 100kHz and a few MHz.
(Assuming the capacitor's capacitance is more than
10ȝF.)
lr1
lr2
C1
C2
ESR1
Zc1
ESR2
Zc2
Ir 䚷㻌 䠖Total ripple current
ESR 䠖Capacitor's equivalent series resistance
Zc
䠖Impedance of the capacitor's capacitive
䚷㻌䚷components
Since impedance becomes exceedingly low when the capacity is more than 10mF. And frequencies higher than 100kHz, each Zc in Figure 1 can be omitted
changing the actual ripple current value to that shown in Figure 2.
Fig.2
lr=1000mArms
OS-CON100ȝF
lr1
lr2
AI-E1000ȝF
ESR1
ESR2
30mȍ
80mȍ
(c) As shown here, although the OS-CON has 1/10th of the capacitance that of the mated
capacitor, it allows 73% of the total ripple current to flow.
(d) When OS-CON and an aluminum electrolytic capacitor are to be used in parallel
connection, select the appropriate type of OS-CON that has an extra margin of capacity
since a large amount of ripple current flows through it.
Formula for calculating the ripple current value
Ir1 = Ir X
ESR2
ESR1 + ESR2
= 1000mA X
80mȍ
䍦 727mArms
30mȍ + 80mȍ
6
Application
Conductive Polymer Aluminum Solid Capacitors
1. Voltage reduction capability of OS-CON
While there is a tendency to downsize switching power supplies capacitors still remain one of the parts occupying large areas of circuit boards. The working temperature is an
important consideration when selecting a capacitor, since it generally results in widely varying capacitor characteristics. The following experiment shows the superior ripple removal
capability of the OS-CON at higher frequencies in wide range of working temperature.
1-1. The number of capacitors needed to keep the same ripple voltage level
L
(a) Experiment content
A general chopper switching power supply was used to test the OS-CON against
two alternatives. OS-CON, low-impedance aluminum electrolytic capacitor, and
low-ESR tantalum capacitors were each connected as the capacitor in the output
side smoothing circuit at working temperature range of -20䉝, 25䉝 and 70䉝 to
compare the output ripple voltage.
VOUT = 3.3V, IOUT = 3A
+
VIN =
5V
SW IC
Oscilloscope
RL
C
200kHz
Specimen
(1) Initially OS-CON䞉100uF/6.3V (6SVP100M䞉ij6.3mm×L6.0mm) was used as the output side smoothing capacitor (C) in the above test circuit, the ripple voltage was
measured at ambient temperature of each temperature. Refer to table 3.
(2) Low-impedance aluminum electrolytic capacitors and Low-ESR tantalum capacitors were selected for measurement at each temperature so that the ripple voltage became
equal to that achieved when the OS-CON䞉100uF/6.3V was used. Refer to table 3.
(3) The ripple voltage was measured at each temperature (-20䉝 to 70䉝) with an equal number of side smoothing capacitors to the 25䉝 conditions, and the rates of change in
the ESR of the smoothing capacitors were calculated from the amounts of change. Refer to table 2.
(b) Experiment result
Table1 On-board area ratios of capacitors at each temperature
(when the ripple voltage is on the same level)
Table2 Rates of change in ESR on the basis of 25䉝(䈜)
Ambient
temperature
OS-CON
Aluminum
Electrolytic capacitor
Tantalum
capacitor
25䉝
1
7.15
1.46
25䉝
䠉20䉝
1
16.7䚷
1.46
䠉20䉝
70䉝
1
4.77
1.46
70䉝
䈜Rate of change in ESR =
Ambient
temperature
Ripple voltage at ambient temperature X Oscillation frequency at ambient temperature
Ripple voltage at 25䉝 X Oscillation frequency at 25䉝
OS-CON
Aluminum
Electrolytic capacitor
Tantalum
capacitor
1
1
1
1.14
3.03
1.27
0.952
0.587
0.85
From the above results, it can be seen that
OS-CON excels in temperature characteristics.
7
Application
Conductive Polymer Aluminum Solid Capacitors
Table3 Measurement comparison at 25䉝
Ambient temperature
25䉝
Capacitor type
OS-CON
Aluminum Electrolytic capacitor
Tantalum capacitor
capacitance/voltage
100ȝF/6.3V
680ȝF/6.3V
100ȝF/10V
Size䠄䈜1䠅䠄mm䠅
6.6 X 6.6
10.5 X 10.5
7.5 X 4.5
1
7.15
Quantity
On-board area ratio
Oscillation frequency
1.46
200kHz
22.8mV
ripple voltage
23.8mV
Fig1
24.8mV
Fig2
(2us/div)
CH1䠙20mV
AC 1:1
Fig3
(2us/div)
CH1䠙20mV
AC 1:1
22.8mV
(2us/div)
CH1䠙20mV
AC 1:1
24.8mV
23.8mV
Fig
200kHz
200kHz
200kHz
䈜1 The base plate dimensions were taken as the maximum dimensions except for Ta.
8
Application
Conductive Polymer Aluminum Solid Capacitors
Table4 Measurement comparison at -20䉝
Ambient temperature
-20䉝
Capacitor type
OS-CON
Aluminum Electrolytic capacitor
Tantalum capacitor
capacitance/voltage
100ȝF/6.3V
680ȝF/6.3V
100ȝF/10V
Size䠄䈜1䠅䠄mm䠅
6.6 X 6.6
10.5 X 10.5
7.5 X 4.5
1
16.7
Quantity
On-board area ratio
Oscillation frequency
1.46
250kHz
20.8mV
ripple voltage
25.2mV
24.4mV
Fig4
Fig5
(2us/div)
CH1䠙20mV
AC 1:1
Fig6
(2us/div)
CH1䠙20mV
AC 1:1
25.2mV
24.4mV
20.8mV
(2us/div)
CH1 = 20mV
AC 1:1
Fig
250kHz
250kHz
250kHz
䈜1 The base plate dimensions were taken as the maximum dimensions except for Ta.
9
Application
Conductive Polymer Aluminum Solid Capacitors
Table5 Measurement comparison at 70䉝
Ambient temperature
70䉝
Capacitor type
OS-CON
Aluminum Electrolytic capacitor
Tantalum capacitor
capacitance/voltage
100ȝF/6.3V
680ȝF/6.3V
100ȝF/10V
Size䠄䈜1䠅䠄mm䠅
6.6 X 6.6
10.5 X 10.5
7.5 X 4.5
1
4.77
Quantity
On-board area ratio
Oscillation frequency
1.46
170kHz
25.6mV
ripple voltage
24.0mV
Fig7
24.8mV
Fig8
(2us/div)
CH1䠙20mV
AC 1:1
Fig9
(2us/div)
CH1䠙20mV
AC 1:1
25.6mV
(2us/div)
CH1䠙20mV
AC 1:1
24.8mV
24.0mV
Fig
170kHz
170kHz
170kHz
䈜1 The base plate dimensions were taken as the maximum dimensions except for Ta.
10
Application
Conductive Polymer Aluminum Solid Capacitors
1-2. Ripple voltage removal capability before and after endurance test
(a) Experiment content
OS-CON and low-impedance aluminum electrolytic capacitors were respectively connected to the output side of chopper switching power supply, as soothing capacitors. Output
ripple voltage made by the two kinds of capacitor was respectively measured before and after endurance tests (125䉝×1000h, rated voltage applied) of the capacitors.
The ripple voltage measurement was done at the ambient temperatures of 25䉝, 0䉝, and -20䉝.
+
VIN =
12V
Oscilloscope
VOUT = 3.3V, IOUT = 1A
L
SW IC
OS-CON 56ȝF/10V(10SVPD56M ij6.3mm×L6mm) and low-impedance aluminum
electrolytic capacitor 330ȝF /10V (ij10mm×L10mm) were used for this experiment.
Measured ESR value of the OS-CON was 38mȍ, while that of the aluminum electrolytic
capacitor was 180mȍ. To match the equivalent ripple voltage one OS-CON brings, four
pieces of the aluminum electrolytic capacitor were used.
RL
C
200kHz
Specimen
Ripple current through coil
Output ripple voltage(outline) =
ESR of capacitor
(1) Specifications of test samples
capacitance/voltage
ESR
(2) ESR change of test samples
OS-CON
Aluminum electrolytic capacitor
56ȝF/10V
330ȝF/10V
45mȍ
Category temperature
range
䠉55䉝䡚䠇125䉝
Endurance
125䉝×2,000h
300mȍ
OS-CON
Ambient
temperature
in measuring
Initial
Aluminum electrolytic capacitor
Initial
value
Value after 125䉝×
10V applied×1,000h
value
Value after 125䉝×
10V applied×1,000h
25䉝
38mȍ
40mȍ
180mȍ
231mȍ
䠌䉝
39mȍ
41mȍ
369mȍ
663mȍ
䠉20䉝
38mȍ
40mȍ
907mȍ
2,212mȍ
䠉40䉝䡚䠇125䉝
125䉝×2,000h
Size(mm)
ij6.3×L6
ij10×L10
11
Application
Conductive Polymer Aluminum Solid Capacitors
(3) Endurance䠄125䉝×10V applied䠅
䛊ESR䛋
ESR (mȍ at 100kHz)
OS-CON䠄10SVPD56M䠅56ȝF/10V
Aluminum electrolytic capacitor 330ȝF/10V
100
25䉝
100000
0䉝
䠉20䉝
10
0
200
500
1000
2000
䠉40䉝
10000
Time (h)
1000
100
0
200
500
1000
2000
Time (h)
䛊Capacitance䛋
(% at 120Hz)
Capacitance Change
OS-CON䠄10SVPD56M䠅56ȝF/10V
Aluminum electrolytic capacitor 330ȝF/10V
20
10
0
ʊ10
ʊ20
ʊ30
ʊ40
25䉝
0䉝
䠉20䉝
䠉40䉝
0
200
500
1000
Time (h)
2000
20
10
0
ʊ10
ʊ20
ʊ30
ʊ40
0
200
500
1000
2000
Time (h)
12
Application
Conductive Polymer Aluminum Solid Capacitors
(b) Experiment result
(1) Comparison of ripple voltage waveform at 25䉝
After endurance test (125䉝×10V applied×1000h)
Initial
OS-CON䠄10SVPD56M䠅
56ȝF/10V×1pc
䠄2us/div䠅
CH1䠙50mV
䚷AC 1:1
CH1䠙50mV
䚷AC 1:1
31.0mV
䠄2us/div䠅
31.0mV
ĺ
Initial
Aluminum electrolytic
capacitor
330ȝF/10V×4pc
After endurance test (125䉝×10V applied×1000h)
䠄2us/div䠅
CH1䠙50mV
䚷AC 1:1
CH1䠙50mV
䚷AC 1:1
䠄2us/div䠅
51.0mV
42.0mV
ĺ
Result
Initial
After endurance test
OS-CON
31mVp-p
31mVp-p
Aluminum electrolytic capacitor
42mVp-p
51mVp-p
13
Application
Conductive Polymer Aluminum Solid Capacitors
(2) Comparison of ripple voltage waveform at 0䉝
After endurance test (125䉝×10V applied×1000h)
Initial
OS-CON䠄10SVPD56M䠅
56ȝF/10V×1pc
䠄2us/div䠅
CH1䠙50mV
䚷AC 1:1
CH1䠙50mV
䚷AC 1:1
䠄2us/div䠅
32.0mV
30.0mV
ĺ
Initial
Aluminum electrolytic
capacitor
330ȝF/10V×4pc
After endurance test (125䉝×10V applied×1000h)
䠄2us/div䠅
CH1䠙50mV
䚷AC 1:1
CH1䠙50mV
䚷AC 1:1
䠄2us/div䠅
128.0mV
78.0mV
ĺ
Result
Initial
After endurance test
OS-CON
30mVp-p
32mVp-p
Aluminum electrolytic capacitor
78mVp-p
128mVp-p
14
Application
Conductive Polymer Aluminum Solid Capacitors
2. OS-CON high speed back-up performance
(Back-up capacitor for dynamic load)
IC, especially MPU that are lately used in electronic devices operate at very high processing speed. PCB’s are able to be more densely populated by lowering voltage and getting
narrow pattern space. Involved in changing to lower voltage, load current is increasing with a development of new MPU.
A sudden change of load current with larger dynamic load at high speed causes the voltage fluctuation of power supply line, and it makes MPU work wrong.
Capacitors with low ESR and large capacitance are necessary for high-speed load current transients.
The OS-CON can provide the largest capacitance among low ESR capacitors, and in this regard, the OS-CON is a suitable back-up capacitor.
Let us explain the excellent back-up performance of OS-CON compared to that of other electrolytic capacitors.
2-1. Test condition
Test circuit
(a) Switching wave form
1W
Backup waveform
Whole wave form
SW
Dynamic load current
Power
supply
CH3䠙2V
AC 10 : 1
Rising wave form
5us/div
CH3䠙2V
AC 10 : 1
20ns/div
V Oscilloscope
2ȍ
Sample
Load condition
Item
Condition
Load width
5ms
Cycle
12.5ms
Rising time
20ns
Dynamic load current
2A
Voltage
4V
Power supply
impedance
2V/div
5ms/div
2V/div
20ns/div
1ȍ
Suitable back-up capacitor for an AC volt tolerance can be estimated from the following equation:
ǻ V : AC Volt tolerance (V)
V=
I×
C
t
×
T䠉 t
T
䠇 I×ESR
ǻ I : Dynamic load current (A)
ǻ t : Load width (s)
C : Capacitance (F)
ESR : ESR (ȍ)
T : Cycle (s)
16
Application
Conductive Polymer Aluminum Solid Capacitors
2-2. Result
(a) Comparison between OS-CON and other capacitors with same capacitance
Compared with same capacitance, OS-CON voltage change of supply line is 104mV, but low-impedance Aluminum electrolytic capacitor indicates 548mV (5.3times
of OS-CON), and low ESR Tantalum electrolytic capacitor indicates 212mV (2times of OS-CON).
OS-CON
Low Z Aluminum capacitor
Low ESR Tantalum capacitor
10SVP100M, ESR : 21mȍ
10V100ȝF, ESR : 245mȍ
10V100ȝF, ESR : 85mȍ
CH2䠙200mV
AC 1 : 1
ǻV=104mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=548mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=212mV
5us/div
200mV/div
5ms/div
(b) Examination of same level variable load
To obtain similar level of voltage change to 10SP100M, Low Z Aluminum electrolytic capacitor needs 1,500ȝF or more. Low ESR Tantalum electrolytic capacitor
needs 220ȝF X 2pcs or more.
OS-CON
Low Z Aluminum capacitor
Low ESR Tantalum capacitor
10SVP100M
10V1,500ȝF
10V220ȝF×2
CH2䠙200mV
AC 1 : 1
ǻV=104mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=128mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=116mV
5us/div
200mV/div
5ms/div
17
Application
Conductive Polymer Aluminum Solid Capacitors
(C) Comparison with lower temperature (-20䉝) of (b)
Compared them under the lower temperature, OS-CON is able to keep stable, while the low Z aluminum capacitor has 3.2 times larger drop of the voltage and
the low ESR tantalum capacitor has 1.2 times larger change of the voltage.
OS-CON
Low Z Aluminum capacitor
Low ESR Tantalum capacitor
10SVP100M
10V1,500ȝF
10V220ȝF X 2
CH2䠙200mV
AC 1 : 1
ǻV=104mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=404mV
5us/div
200mV/div
5ms/div
CH2䠙200mV
AC 1 : 1
ǻV=144mV
5us/div
200mV/div
5ms/div
18
Application
Conductive Polymer Aluminum Solid Capacitors
3. Image effect caused by power line noises
Let’s see how capacitor differences affect an image, in other words, how digital noises affect analog signals.
(a) Effect on a security camera image
OS-CON and low Z aluminum electrolytic capacitors were respectively mounted on the filter circuit of a security camera’s power line. Then the recorded images in both cases
were compared at normal and low temperatures. No differences were seen at initial recordings. But a difference appeared at 䞊20䉝 after an endurance test on the respective
capacitors.
After Endurance Test (105䉝×16V×2,000h)
OS-CON (SVP series)
20V䠋22ȝF Size ij6.3×L6.0mm
Initial ESR
ESR after
endurance
42mȍ (25䉝)
42mȍ (䠉20䉝)
45mȍ (25䉝)
45mȍ (䠉20䉝)
ĺ
image1
25䉝
image3
䞊20䉝
gamma adjusted(3.0)
Low Z aluminum electrolytic capacitor
16V䠋100ȝF Size ij6.3×L6.0mm
Initial ESR
ESR after
endurance
303mȍ (25䉝)
1,080mȍ (䠉20䉝)
418mȍ (25䉝)
1,640mȍ (䠉20䉝)
ĺ
image2
25䉝
image4
䞊20䉝
gamma adjusted(3.0)
(b) Summary
(1)With OS-CON : No image defects were seen at both 25䉝 and 䞊20䉝.
(2)With low Z electrolytic capacitors : The capacitor’s deteriorated ESR (1,640mȍ) caused an image distortion (pale and striped effect) at 䞊20䉝. See the gamma adjusted
images for easier distinction. The red-circled part best shows the striped effect.
19
Application
Conductive Polymer Aluminum Solid Capacitors
4. OS-CON equivalent circuit model
Using a circuit simulation increased for shortening the circuit design in recent years.
A resistance and inductance element of the pattern are simulated considerately due to CPU's voltage accuracy is severe.
Concerning a backup capacitor, the simulation model that characteristic is close to actual measurement is required
4-1. Current equivalent circuit's issue
In the simulation of a power supply circuit, the simulation is done in the equivalent circuit of the ideal capacitor as Figure 1.
There has rarely problem for the purpose to confirm a ripple voltage and a ripple current. But it cannot satisfy that higher accuracy simulation such as the load changes of CPU.
There might be a large difference between a real circuit and the simulation result. This is because ESR & capacitance frequency characteristic are not reflected.
4-2. Equivalent circuit for more accurate simulation
We made the equivalent circuit as shown in Figure 2.
As a result, capacitor has the frequency characteristics which are close to the measurement result and it is useful for a simulation near the real operation in circuit.
Fig.1 Current equivalent circuit
Fig.2 Equivalent circuit for more accurate simulation
20
Application
Conductive Polymer Aluminum Solid Capacitors
ƔComparison of frequency characteristics of measurement and simulation
䛊Current equivalent circuit䛋
10000
䛊Equivalent circuit for more accurate simulation䛋
10000
Measured Value Z
Simulated Value Z
Measured Value ESR
Simulated Value ESR
ĺ
100
10
1
0.1
1
10
100
1000
10000
lmpedance & ESR䠷mȍ䠹
1000
100
10
1
100000
0.1
1
10
ESL䠷nH䠹
1000
ĺ
100000
10.0
Measured Value C
Simulated Value C
Measured Value L
Measured Value C
Simulated Value C
Measured Value L
Simulated Value L
1
10000
ESL䠷nH䠹
10.0
0.1
1000
C䠷ȝF䠹
1000
100
100
frequency䠷kHz䠹
frequency䠷kHz䠹
C䠷ȝF䠹
lmpedance & ESR䠷mȍ䠹
1000
Measured Value Z
Simulated Value Z
Measured Value ESR
Simulated Value ESR
10
100
1000
10000
1.0
10000
100
0.1
frequency䠷kHz䠹
Simulated Value L
1
10
100
1000
10000
1.0
10000
frequency䠷kHz䠹
Model䠖2SEPC560MW䠄2.5V-560ȝF䠅
21
Application
Conductive Polymer Aluminum Solid Capacitors
4-3. Frequency characteristics of Capacitance
The frequency characteristics of capacitance cannot show a normal value around the resonance point when a capacitor is measured.
This is because measuring instruments that impedance analyzer or LCR meter, etc. impress the voltage signal, and capacitance is calculated from the phase lag with the current.
This phase lag is decided by the difference between impedance Zc of capacitance and impedance ZL of inductance. It becomes ''Zc䠚䠚ZL'' when the frequency is lower, and
inductance hardly influences it. It comes to receive the influence of ZL as the frequency rises. The phase lag decreases around the resonance point (Zc䍦ZL). The direction
changes and capacitance cannot be measured.
However, it becomes possible to guess the capacitance frequency characteristics with this equivalent circuit (Fig.2). Capacitance frequency characteristics can be shown by
assuming all inductance of an equivalent circuit to be zero. Below figure shows graphing of the calculation result. The resonance point of the capacitor is at 190kHz. It is influenced
by ZL from the 1/10 frequency.
Model䠖2SEPC560MW䠄2.5V-560ȝF䠅
Impedance element
1000
ESR
ZL
ZC
ZL-ZC
[Truth]
ZC
ZC
[Calculated
Value] -j
į
ș
R
C䠷ȝF䠹
j
Z
Measured Value C
ESR = Z × cosș
ZC = Z × sinș
Simulated Value C
100
0.1
1
10
100
1000
10000
10000
frequency䠷kHz䠹
22
Application
Conductive Polymer Aluminum Solid Capacitors
5. Application to low-pass filter circuits
As a means of removing noise from power supply lines, a low-pass filter such as shown below may be used.
In recent years, switching power supplies have been become a main power sources, that are compact and highly efficient, but its make a large noise sources. Also, digital circuits
make noise easily, and in most of the devices with mixed noise-sensitive analog circuits, entry of high-frequency noise into the analog circuits is prevented by connecting these
low-pass filters to the power supply lines of the analog circuits.
(a) The damping effect of the filter gets closer to an ideal damping rate as capacitor has lower ESR.
Fig.1 LC Filter
Fig.2 RC Filter
(b) Capacitance and ESR have 0 point frequency (fz), when the frequency is higher than 0 point
frequency, +20dB/dec cancel the damping effect.
(c) LC filter : -40dB/dec is to be -20dB/dec
RC filter : -20dB/dec is to be 0 (non-damping effect)
(d) Even if capacitance is increased, there has no effect of noise cutting, it is influenced by the 0
point frequency.
OS-CON is most effective in low-pass filter because of low ESR.
Fig.3 Actual damping factor
Frequency
Frequency
Damping factor
when ESR is lower
Attenuation
ec
/d
dB
20
In case Capacitance
increased
fz (Frequency at 0 point)
0dB
䠉
Actual
damping factor
ec
/d
dB
20
䠉
Attenuation
fc
fz (Frequency at 0 point)
fc
ec
B/d
0d
䠉4
0dB
Actual
damping factor
Damping factor
when ESR is lower
In case Capacitance
increased
Ideal
damping factor
(a) LC Filter
Ideal damping factor
(b) RC Filter
Compare the actual damping factor of the following OS-CON with an aluminum electrolyte capacitor on the next page
OS-CON䠄20SEP33M䠅
Aluminum electrolytic capacitor
20V/33ȝF䠈ESR=37mȍ(The actual measurement)
10V/33ȝF䠈ESR䠙1410mȍ(The actual measurement)
23
Application
Conductive Polymer Aluminum Solid Capacitors
5-1. LC Filter (L=10ȝH)
Aluminum electrolytic capacitor
80
60
60
40
40
Gain [dB]
Gain [dB]
OS-CON
80
20
0
20
0
䠉20
䠉20
䠉40
䠉40
䠉60
䠉60
䠉80
10
100
1k
10k
100k
Frequency [Hz]
䠉80
10
1M
100
1k
10k
100k
Frequency [Hz]
1M
OS-CON shows a damping effect in higher frequency regions
comparing with an aluminum electrolytic capacitor.
These measurements were made at room temperature. The
difference in damping effect will be larger when the temperature is
under 0䉝, because ESR of an aluminum electrolytic capacitor will
5-2. RC Filter (R=5.6)
extremely increase. Oppositely OS-CON has little increase that
Aluminum electrolytic capacitor
80
80
60
60
40
40
Gain [dB]
Gain [dB]
OS-CON
20
0
20
0
䠉20
䠉20
䠉40
䠉40
䠉60
䠉60
䠉80
10
100
1k
10k
Frequency [Hz]
100k
1M
does not affect the damping effect of the filter.
䠉80
10
100
1k
10k
100k
1M
Frequency [Hz]
24
Application
Conductive Polymer Aluminum Solid Capacitors
6. Application of switching power supply for smoothing capacitor
For restraining output ripple current, the output smoothing capacitor of the switching power supply is need to use low ESR capacitor. However the lower ESR capacitor makes the
phenomenon sometimes occurs, which is called the abnormal oscillation of output voltage.
The abnormal oscillation of output voltage varies depending on the regulator method or the topology such as buck
Fig.1 Control block of switching power supply
type, boost type, etc. We explain the mechanism and the treatment method of output voltage oscillation with the
sample of the Buck style switching regulator under the voltage control mode.
Q1
L
Zi
Cin
The switching power supply usually has the negative feed-back circuit to stabilize output voltage.
The difference between output voltage and standard voltage Vref are amplified with the error amplifier and convert to
the digital signal with the PWM comparator and flip on and flip off switch Q1.
Input voltage Vin becomes a square wave form by Q1, and you obtain DC output voltage Vout by make it smooth
with coil L and capacitor Cout. L and also Cout assumed that they form the second low pass filters.
D
Cout
Zc
Error Amp.
PWM Comparator
The frequency characteristics of the output LC filter is expressed with the Bode diagram like Figure 2.
The phase is delayed 180 degrees originally, because the error amplifier is a negative feedback circuit. Therefore,
the phase delay of the output LC filter and the error amplifier occur at the same time, and when 360 degrees delay
occur, the output voltage oscillates.
Vref
OSC
Fig.2 Frequency characteristic of LC filter
180
90
Gain
Phase
80
70
60
160
140
120
Cut-off frequency
100
40
80
30
Zero point frequency 60
20
40
10
20
0
0
䠉10
䠉20
䠉20
䠉40
䠉30
䠉60
Phase [deg]
50
Gain [dB]
The damping rate of the LC filter is -40dB/dec and the cut-off frequency becomes 2p
䚷䚷1LC
䚷䚷䚷, and
become Gain and Phase like the dotted line of Figure 2.
With an ideal filter the output voltage oscillates because it is delayed 180 degrees. But more than
some frequency that is called zero frequency, damping rate of Gain becomes -40dB/dec to
-20dB/dec. Furthermore the Phase returns to delay 90 degrees from delay 180 degrees. This is
because the first order Phase lead network is formed by the capacitance value and ESR of
1 䚷䚷䚷䚷䚷, the Gain damping rate goes on
Cout. Because, after the zero point frequency 2p Cout
ESR
the Phase of +20dB, +90 degrees. However, when the low ESR capacitor is used, it works as a
LC filter up to high frequency band, and the phase delay to nearly 180 degrees and it becomes
easy to oscillate.
30 degrees to 40 degrees or more of Phase margin is thought as a necessity to inhibit the
oscillation of output voltage with a general negative feed-back circuit. The Phase margin is
numerical value how much the minimum value of the Phase is distant from-180 degrees. The
smaller the Phase margin gets, the higher the possibility to oscillate by the characteristic dispersion
and temperature change of the component will be.
Vout
Vin
6-1. Abnormal oscillation of output voltage
䠉80
䠉40
Large
䠉50
䠉60
䠉100
䠉120
ESR
䠉70
䠉140
䠉160
䠉80
Small
䠉90
1
10
100
1000
10000
100000
䠉180
1000000
Frequency [Hz]
25
Application
Conductive Polymer Aluminum Solid Capacitors
6-2. Inhibition method of oscillation
By doing Phase compensation with the feed-back circuit of the error amplifier the
oscillation of output voltage can be inhibited.
There are various kinds in Phase compensation. It is most effective to use the
Phase compensation circuit like the following in the switch power supply of the
voltage control mode.
Figure 3 : 䐠 & 䐢 form first order Phase lead network. 䐟 & 䐡 form first order Phase lag
network.
By adjusting these values, it does the Phase compensation by which Phase will occur
and improve Phase delay of the whole negative feed-back circuit by the frequency
characteristic of output LC filter at the frequency band which the Phase indicates the
lowest.
Fig.3 Phase compensation network of Voltage Control Mode
Zc
䐡
Zi
䐠
䐟
䐢
from Vout
PWM
Comparator
Error Amp.
Vref
Fig.4 Frequency characteristic of Phase Compensation Network
90
180
80
160
Gain
60
Phase
50
140
120
100
40
80
30
60
20
40
10
20
0
0
䠉10
䠉20
䠉20
䠉40
䠉30
䠉60
䠉40
䠉80
䠉50
䠉100
䠉60
䠉120
䠉70
䠉140
䠉80
䠉160
䠉90
Phase[deg]
70
Gain[dB]
Figure 4 : Example. As the Phase of the output LC filter of Figure 2 becomes a lowest
point at around 10kHz, it has about 30 degrees of Phase lead around that frequency.
Because of this, it can secure the Phase margin of 30 degrees even if the Phase delay of
LC filter becomes 180 degree nearly, the oscillation of output voltage can inhibited.
䠉180
1
10
100
1000
10000
100000
1000000
Frequency[Hz]
26
Application
Conductive Polymer Aluminum Solid Capacitors
6-3. Concrete design examples of prevention oscillation
Fig.5 Step-down DC-DC converter design example
Q1
10uH
Vin
Zi
Vout
C in
D
C out
Zc
+
Vref
Error
amplifier
+
-
DV
PWM
comparator
Triangular wave generator
200kHz
The ESR of the output capacitor necessary to make an output ripple voltage of 20mVp-p
can be obtained as follows:
ESR < Vripple / ((Vin-Vout) / L*Vout / Vin / fosc) = 35.7mȍ
Consequently, the following capacitors have been selected.
[Specification]
• Input voltage (Vin)
: 5V
(a) OS-CON
6SVP100M䚷 1-parallel䚷 ij6.3×L6mm 䚷ESR = 32mȍ 䈜ESR is an actual measurement.
• Output voltage (Vout) : 3.3V
• Output current (Iout)
: 3.2A
• Output ripple voltage (Vripple) : 20mVp-p
(b) Aluminum electrolytic capacitor
6V/680uF 䚷 3-parallel
ij10×L8mm䚷 ESR = 128mȍ/p.
Total ESR = 43mȍ
Photograph 1: Measuring evaluation board using the above capacitors
We can downsize by using the OS-CON compared with aluminum electrolytic capacitors if the most favorable phase compensating circuit is provided as follows.
Photo 1 Evaluated circuit boards
OS-CON
Aluminum electrolytic capacitor
27
Application
Conductive Polymer Aluminum Solid Capacitors
6-4. Examples of design with aluminum electrolytic capacitors
Fig.6 Frequency characteristics of the LC filter with the AL-E
used, the frequency characteristics of the output
20
40
LC filter are as shown in Fig.6, and there is a
10
20
0
0
sufficient phase margin to such an extent that
Therefore, the phase compensating circuit in Fig.7
is sufficient.
Gain
Phase
䠉10
Gain[dB]
there is no need to make phase compensation.
䠉20
Fig.7 Phase compensating circuit
䚷䚷 with the AL-E
䠉20
䠉40
䠉30
䠉60
䠉40
䠉80
䠉50
䠉100
䠉60
䠉120
䠉70
䠉140
䠉80
䠉160
䠉90
Phase[deg]
When the aluminum electrolytic capacitors are
Rin䠖20kȍ
Rc䠖33kȍ
Cc䠖10000pF
Zc
Cc
Rc
Zi
Rin
Vout
+
PWM To PWM
comparator
Error amplifier
Vref
䠉180
10
100
1000
10000
100000
Frequency[Hz]
Fig8 Total frequency characteristics with the AL-E
the total frequency characteristics are as shown in Fig.
50
8, and there is a sufficient phase margin.
40
Gain[dB]
(properly speaking, phase compensation is not made),
60
Fig.9 Output ripple voltage waveform with the AL-E
180
Gain
Phase
90
20
60
10
30
0
0
䠉10
䠉30
䠉20
䠉60
䠉30
䠉90
䠉40
䠉120
䠉50
䠉150
100
(2us/div)
120
30
䠉60
CH2䠙5mV
AC 1:1
150
Phase[deg]
With the phase compensation network is Fig. 7
22mVp-p
䠉180
1000
10000
100000
Frequency[Hz]
28
Application
Conductive Polymer Aluminum Solid Capacitors
6-5. Examples of design with the OS-CON
When the aluminum electrolytic capacitors used in power supply circuits are replaced with the OS-CON without changing the phase compensation network, the output
voltage oscillates. (Fig.10)
As a reason, we can say that the phase margin is lost because the phase compensation network is not changed despite the fact that the frequency characteristics of
the output LC filter change as shown in Fig.6, where the aluminum electrolytic capacitors are used, to Fig.11, where they are replaced with the low ESR OS-CON.
CH4䠙100mV
AC 10:1
Fig.11 Frequency characteristics of the
䚷䚷䚷 LC filter with the OS-CON
(20us/div)
20
40
10
0
Gain[dB]
Fig.12 Phase compensating circuit with the OS-CON
Gain
20
Phase
0
䠉10
䠉20
䠉20
䠉40
䠉30
䠉60
䠉40
䠉80
䠉50
䠉100
䠉60
䠉120
䠉70
䠉140
䠉80
䠉160
䠉90
10
1000
10000
Zc
Cc1
Zi
Rin2 Cin
Rc
Rin1
Vout
Cc2
+
PWM To PWM
comparator
Error amplifier
䠉180
100
Cc1䠖330pF
Cc2䠖33000pF
Cin䠖4700pF
Rc䠖3.3kȍ
Rin1䠖20kȍ
Rin2䠖680ȍ
Phase[deg]
Fig.10 Oscillating output voltage waveform
Vref
100000
Frequency[Hz]
Fig.13 Total frequency characteristics with the OS-CON
shown in Fig.11, appropriate phase compensation
60
can
50
be
made
by
using
such
a
phase
Gain
Phase
120
30
90
forming phase leads at Zi and Zc in Fig.12.
20
60
10
30
0
0
Gain[dB]
40
This is to cancel the deepened phase lag by
䠉10
䠉30
is
䠉20
䠉60
sufficient; and the output ripple voltage waveform
䠉30
䠉90
(Fig.14) is almost the same as is the case with the
䠉40
䠉120
aluminum electrolytic capacitors.
䠉50
䠉150
are
as
shown
in
Fig.13;
the
phase
margin
䠉60
100
1000
10000
CH2 = 5mV
AC 1:1
150
compensation network as shown in Fig.12.
Because of this, the total frequency characteristics
Fig.14 Output ripple voltage waveform
䚷䚷䚷 with the OS-CON
180
Phase[deg]
When the LC filter has little phase margin as
(2us/div)
19m Vp-p
䠉180
100000
Frequency[Hz]
29
Capacitors Selection Sheet
Conductive Polymer Aluminum Solid Capacitors
Company
Application
Dept.
Power Supply / Filter / By-pass Capacitor / Coupling Circuits /
Others (
Name
Equipment
TEL
)
PC / PC Peripheral Unit / Audio / Communication / Automobile /
Other (
FAX
)
mm
Height limit
E-mail
Radial
SMD
Option
Indispensable item
Unit
Item
Symbol
Switching Frequency
fosc
kHz
Current Change
ǻI
A
Input Voltage
Vin
V
Voltage Drop
ǻVdrop
mV
Output Voltage
Vout
V
Control IC
Output Current
Iout
A
mVp-p
Item
Mount type
Symbol
Value
Ripple Voltage
ǻVripple
Ambient Temperature
Ta
䉝
Primary Inductance
L1
ȝH
Inductance
L
Winding ratio
n1 : n2
Value
Unit
Iout
ǻI
0A
Vout
ȝH
ǻ Vripple
ǻ Vdrop
:
0V
䕺Please enclose the use circuit in a circle.
䐟BUCK
Vin > Vout
䐠BOOST
䚷Vin < Vout
Iout
L
+
+
+
Vout
Vin
Vin
fosc
䐡BUCK-BOOST
䚷0 > Vout
Iout
L
+
+
fosc
Iout
Vout
Vin
L
+ Vout
fosc
䐣FLYBACK
䐢FORWARD
L
n1
L1
+
Vin
fosc
n2
Iout
Iout
+
Vout
n1
L1
+
n2
+
Vout
Vin
fosc
The design support tool is available at the following URL on the Internet.
http://industrial.panasonic.com/
30