The Important Information/Disclaimer is incorporated in the catalog where these specifications came from or

available online at www.avx.com/disclaimer/ by reference and should be reviewed in full before placing any order.

23

PULSE CAPACITOR APPLICATIONS

As mentioned earlier, the voltage drop in a circuit is critical as the circuit

will not operate below a certain cut-off voltage. There are two sources of

voltage drop (∆V) which occur, the first ∆VESR is because of the equivalent

series resistance (ESR) and the second, called the capacitive drop, is ∆VC.

From Ohm’s law,

voltage = current x resistance or V = IR

Let us say that the instantaneous starting voltage is Vo, or voltage for the

circuit from where the voltage drops. If the capacitor has an ESR of 100

milliOhms and the current is 1 amp,

∆VESR = 1 amp x (0.100) ohms = 0.1 volts or 100 milli-volts. On demand,

during the discharge mode, the voltage V = Vo

- ∆VESR = (Vo - 0.1) volts

The second voltage drop is because of the capacitance. This is shown in the

equation as a linear function because of simplicity. Simply put,

Q (charge) = C (capacitance) x V (voltage)

The derivative, dQ/dt = I (current, in amps) = C x dV/dt

Hence, ∆V

C (dV, the voltage drop because of capacitance)  = I  x dt/C.

This formula states that the larger the capacitance value the lower

the voltage drop. Compared to a Ta capacitor, this ∆VC is reduced by

a factor of about 10 to 100. So, BestCap® has an advantage where

higher capacitance is needed. If the current pulse itself is 1 amp, the

current pulse width is 1 second and the capacitance is 10 millifarads,

the ∆VC = 1A x 1Sec/0.01F, or a 100 volts; such an application is out of

the range of BestCap®. However, if the pulse width becomes narrower,

say 10 milliseconds, and the capacitance is 100 millifarads, the ∆VC

= 1 x (10/1000)/(100/1000) = 0.1 volt or 100 millivolts. This shows

the advantage of the large capacitance and hence the term “pulse”

capacitor. The specific power – specific energy graphs are used in the

battery industry to compare competitive products. As the dt becomes

smaller i.e.100 milliseconds, 10 milliseconds and then 1 millisecond,

our estimates show that the specific power for the BestCap® is the

highest as compared to our competitors because of our choice of

internal materials chemistry.

Conclusion: we now clearly show that BestCap® has an advantage over

competitors for short current pulse whose widths are smaller than a few

hundred milliseconds.

Figure 6a. Li-ION Battery at +25°C

Figure 6b. Li-ION Battery at +0°C

2

2.5

3

3.5

4

0

100

200

300

400

Cutoff Voltage Limits

Cutoff Voltage

3.4 Volts

3.5 Volts

3.6 Volts

Time (Minutes)

% Increase

28%

73%

300%

Battery Alone

Battery with Pulse Capacitor

GSM Pulse @ 2 Amps

2

2.5

3

3.5

4

0

100

200

300

400

LI-ION Battery

500

Cutoff Voltage

3.4 Volts

3.5 Volts

3.6 Volts

Time (Minutes)

% Increase

28%

100%

300%

Battery Alone

Battery with Pulse Capacitor

GSM Pulse @ 2 Amps 0°C

BestCap® Ultra-low ESR

High Power Pulse Supercapacitors

070820