Many electronic designers are aware of the role of filtering capacitors in the power supply, but the filtering capacitance used in the output of the switching power supply
On the filter capacitors used in the output of the switching power supply, and the filter capacitors selected in the industrial frequency circuit is not the same, in the industrial frequency circuit used as a filter of ordinary electrolytic capacitors, its
On the pulsating voltage frequency of only 100 Hz, charging and discharging time is milliseconds order of magnitude, in order to obtain a smaller pulsation coefficient, the need for capacitance up to hundreds of thousands of microfarads, and thus the general low-frequency manufacturing of ordinary aluminum electrolytic capacitors, the goal is to improve the capacitance is the main capacitance, capacitor capacitance, loss of angular tangent value and the leakage current is to identify its advantages and disadvantages of the main parameters.
In the switching regulator power supply as the output filter with electrolytic capacitors, the frequency of the sawtooth wave voltage up to tens of kilohertz, or even tens of megahertz, it is the main parameter to identify the quality of the capacitor.
Hertz, or even tens of megahertz, its requirements and low-frequency applications are different, the capacitance is not the main indicator, to measure its good or bad is
It is its impedance and frequency characteristics, it is required to have a low impedance in the operating frequency band of the switching regulator, at the same time, for the
Inside the power supply, due to the semiconductor devices start work produced by up to hundreds of kHz spike noise, can also have a good filtering
General low-frequency with ordinary electrolytic capacitors in about 10 kHz, its impedance will begin to show inductive, can not meet the switching power supply requirements.
Power supply requirements.
Switching voltage regulator power supply special high-frequency aluminum electrolytic capacitors, it has four ends of a son, positive aluminum sheet of the two ends were led out as a
The two ends of the positive aluminum piece are led out as the positive pole of the capacitor, and the two ends of the negative aluminum piece are also led out as the negative pole. The current of the regulated power supply flows from one positive end of the four-terminal capacitor, through the inside of the capacitor, and then through the negative end of the capacitor.
end of the four-terminal capacitor, and then flows to the load from the other positive end; the current returned from the load also flows from the negative end of the capacitor, and then flows to the load from the other negative end.
The current returning from the load also flows from one negative end of the capacitor, and then flows to the negative end of the power supply from the other negative end.
Because the four-terminal capacitor has good high-frequency characteristics, it reduces the pulsation component of the output voltage and suppresses the switching spike noise.
sound provides an extremely favorable means.
High-frequency aluminum electrolytic capacitors also have a multi-core form, which will be divided into a number of short segments of aluminum foil, with a number of parallel connection of the lead sheet to reduce the capacitive impedance in the
It divides the aluminum foil into several short segments and connects them in parallel with multiple lead sheets to reduce the resistive component in the capacitive impedance, and at the same time, adopts low-resistivity materials and uses screws as lead terminals to enhance the capacitor's ability to withstand large currents.
The capacitors are also called non-inductive capacitors.
Stacked capacitors are also known as non-inductive capacitors. Generally, the core of electrolytic capacitors is rolled into a cylindrical shape with a large equivalent series inductance;
The structure of laminated capacitors is similar to the book, because the magnetic flux generated by the flow of current in the opposite direction is canceled, thus reducing the inductance of the
value, with more excellent high-frequency characteristics, this capacitor is generally made into a square, easy to fix, but also can be appropriately reduced to account for machine
Volume.
In addition, there is a combination of four-terminal and laminated four-terminal laminated high-frequency electrolytic capacitors, which synthesizes the advantages of the two
It combines the advantages of the two, and has better high frequency characteristics.
