Many users have encountered the same problem, that is, how to calculate the discharge time of a certain capacity super capacitor when discharging at a certain current, or how to select the capacity of the super capacitor according to the discharge current and discharge time. Below we give a simple calculation company. According to this formula, the user can simply calculate the capacitance capacity, discharge current, and discharge time, which is very convenient.
C(F): the nominal capacity of the supercapacitor;
R (Ohms): the nominal internal resistance of the supercapacitor;
ESR (Ohms): equivalent series resistance at 1KZ;
Vwork (V): normal working voltage
Vmin(V): cut-off operating voltage;
t(s): requires continuous working time in the circuit;
Vdrop(V): the total voltage drop at the end of a discharge or high current pulse;
I(A): load current;
An approximate calculation formula for the capacitance of the supercapacitor,
Maintain the required energy = the energy reduced by the supercapacitor.
Energy required during the hold period = 1/2I (Vwork + Vmin) t;
Supercapacitor reduces energy = 1/2C (Vwork2-Vmin2),
Thus, its capacity can be obtained (ignoring the voltage drop caused by IR)
C=(Vwork+Vmin)It/(Vwork2-Vmin2)
Examples are as follows:
For example, in the application system of the single-chip microcomputer, the super capacitor is used as the backup Power Supply. After the power is turned off, the super capacitor is needed to maintain the current of 100 mA for 10 s. The cut-off working voltage of the single-chip system is 4.2 V, so how much capacity of the super capacitor can ensure the system. normal work?
It can be known from the above formula:
Working starting voltage Vwork=5V
Working cutoff voltage Vmin=4.2V
Working time t=10s
Working power I=0.1A
Then the required capacitance is:
In application, many users encounter the same problem, that is, how to calculate the discharge time of a certain capacity of super capacitor when discharging at a certain current, or how to select the capacity of the super capacitor according to the discharge current and discharge time. According to this formula, the user can simply calculate the capacitance capacity, discharge current, and discharge time, which is very convenient.
C(F): the nominal capacity of the supercapacitor;
R (Ohms): the nominal internal resistance of the supercapacitor;
ESR (Ohms): equivalent series resistance at 1KZ;
Vwork (V): normal working voltage
Vmin(V): cut-off operating voltage;
t(s): requires continuous working time in the circuit;
Vdrop(V): the total voltage drop at the end of a discharge or high current pulse;
I(A): load current;
An approximate calculation formula for the capacitance of the supercapacitor,
Maintain the required energy = the energy reduced by the supercapacitor.
Energy required during the hold period = 1/2I (Vwork + Vmin) t;
Supercapacitor reduces energy = 1/2C (Vwork2-Vmin2),
Thus, its capacity can be obtained (ignoring the voltage drop caused by IR)
C=(Vwork+Vmin)It/(Vwork2-Vmin2)
Examples are as follows:
For example, in the application system of the single-chip microcomputer, the super capacitor is used as the backup power supply. After the power is turned off, the super capacitor is needed to maintain the current of 100 mA for 10 s. The cut-off working voltage of the single-chip system is 4.2 V, so how much capacity of the super capacitor can ensure the system. normal work?
It can be known from the above formula:
Working starting voltage Vwork=5V
Working cutoff voltage Vmin=4.2V
Working time t=10s
Working power I=0.1A
Then the required capacitance is:
C=(Vwork+Vmin)It/(Vwork2-Vmin2)
=(5+4.2)*0.1*10/(52-4.22)
=1.25F
According to the calculation results, you can choose 5.5V1.5F capacitor to meet the needs.
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