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The main technical parameters of the electrolytic capacitor
1 equivalent series resistance ESR
The level of the ESR, and the capacity of the capacitor, the voltage, frequency and temperature ...
are related, ESR requirements better. When the rated voltage is fixed, the capacity, the greater the
lower the ESR. When the capacity is fixed, choosing varieties of high rated voltage can reduce the
ESR. ESR at high frequency, high frequency low ESR, high temperatures also cause increased
ESR. Equivalent series resistance ESR many brands can be found from the specification.
(2) Leakage Current
One can understand that leak! Electrolytic capacitor leakage exists, and this is the physical
structure of the decision. Needless to say, the leakage current is of course the smaller the better.
The higher the capacitor, the greater leakage current; reduce operating voltage can reduce the
leakage current. In turn, choose a higher-pressure varieties will help reduce leakage current.
Combination of the above two parameters, under the same conditions of high pressure varieties
selected priority is indeed a good way to an easy feasible; reduce resistance, reduce the leakage
current, reduce losses and increase life expectancy. A lot of really good, only the price will be
higher. There is a saying, both electrolytic capacitors work well below the rated working voltage,
because it is not effective enough to sustain electrode with the electrolyte between the
depolarization effect, will result in the polarization of the electrolytic capacitor ripple current is
reduced, increasing Big ESR, thus premature aging. But the premise of this argument is "far below
the rated working voltage", some long-term practical experience integrated view, select the rated
voltage of the nominal value 2/3 of the normal operating voltage, it is more reasonable to * a.
Amateur circumstances can electrolytic capacitor leakage current general estimate. The same
capacity electrolytic capacitor is charged according to the rated withstand voltage, place some
time before detecting the voltage drop across the capacitor extent. Voltage drop, the less the
smaller the leakage current.
3. The nominal parameters
Capacitor case is the value listed on.
* Electrostatic capacity, expressed by UF. Not much to say.
* Operating voltage (working voltage) referred WV, safety should be the nominal value, ie the
application circuit must not exceed this nominal voltage.
* Most common temperature of 85 degrees, 105 degrees. High temperature conditions (eg Pure
Class A amplifier) should preferably 105 degrees nominal. Generally a high temperature
coefficient is preferably other parameters to improve performance a positive help.
4 Dissipation factor dissipation factor (DF)
Sometimes DF values expressed by the loss angle tan. DF value is high or low, and the
temperature, capacity, voltage, frequency ...... have a relationship; when the capacity is the same,
the higher the pressure the lower the value of DF. The higher the frequency the higher the DF
value, the higher the temperature the higher the DF values. DF values are generally not indicated
on the capacitor or specifications described above. Select a capacitor in the DIY, you can select a
higher priority to pressure, such as when the operating voltage of 45V, the 50V's not very
reasonable. Although the use of 50V withstand voltage from the normal work there is nothing
wrong, but the lack of DF values on a number of considerations. Use 63V or 71V breakdown
voltage will have better performance. Of course, no matter how high the price on uneconomical.
5 Ripple Current Irac
Ripple current filter circuit for stone, it is a very important parameter. Ripple Current Irac is as
high as possible. His low working frequency, the higher the frequency the greater Irac, the lower
the frequency the smaller Irac. The traditional think we need at low frequencies can have a high
ripple current, in order to get a good high-current discharge characteristics, so that the
low-frequency more solid and full flexibility, and good driving characteristics control; actually
high at high frequencies ripple current on the positive tone was also very helpful, you can make a
better high-frequency extension and reduced roughness.