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