Capacitance filtering Capacitance filtering is the process of continuous charging and discharging of the current in the capacitor, so as to achieve the effect of smoothing the voltage fluctuation of the penalty source.
For example, full-wave rectification outputs two positive half-wave voltages, and when the output voltage reaches a certain peak, the capacitor is charged; When it drops to a certain value, the capacitor discharges to keep the voltage output to the load stable. For the load, there is only voltage fluctuation, but it is always positive voltage, so there is no reverse current;
The capacitor is repeatedly charged and discharged, but the discharge is incomplete, which is carried out on the basis of a certain voltage;
This wave is a single bright light wave.
What does filtering in the circuit mean? What role does it play?
A filter circuit, which passes signals within the frequency range.
What is the specific meaning of capacitive coupling? Is it different from filtration?
Coupling refers to the process of signal transmission from the first stage to the second stage, which usually refers to AC coupling without labeling. Decoupling device
Take further filtering measures to the power supply, and eliminate the influence of signal interference between the two stages through the power supply. The coupling constant refers to
A time constant corresponding to the product of the coupling capacitance value and the input impedance value of the second stage.
Decoupling has three purposes: 1. Remove the high-frequency ripple in the power supply, and connect the high-frequency signals of multistage amplifiers with each other through the power supply.
The interference path is cut off; 2. When the large signal is working, the demand of the circuit for power supply increases, causing power supply fluctuation, which is reduced by decoupling.
Influence of power supply fluctuation on input stage/high voltage gain stage; 3. Forming floating ground or floating power supply in complex system.
Complete the coordination of ground wire or power supply in the system.
The high-frequency switching noise generated by active devices during switching will propagate along the power line. The main function of decoupling capacitor is to provide local DC power supply for active devices, so as to reduce the propagation of switching noise on the circuit board and guide the noise to ground.
From Lund's article "Circuit Board Level Electromagnetic Compatibility Design". This article describes the noise coupling and the use of paths, decoupling capacitors and bypass capacitors. Please refer to.
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Interference coupling mode
The interference signal generated by the interference source is the electromagnetic interference to the electronic control system through a certain coupling channel. The coupling mode of interference is nothing more than acting on the electronic control system through wires, space and public lines. The analysis mainly includes the following types.
Direct coupling: This is the most direct way to interfere with intrusion and the most common way in the system. If the interference signal directly invades the system through the conductor, it will cause interference to the system. For this coupling mode, filtering and decoupling can be used to effectively suppress the incoming electromagnetic interference signal.
Male * * * impedance coupling: This is also a common coupling mode. It often happens that the current paths in two circuits are the same. There are two kinds of common impedance coupling: common ground and power supply impedance. In order to prevent this coupling, the coupling impedance should be close to zero, and there is no common impedance between the interference source and the object.
Capacitive coupling: also known as electric field coupling or electrostatic coupling, is a coupling mode due to the existence of distributed capacitance.
Electromagnetic induction coupling: also known as magnetic field coupling. It is a coupling mode induced by electromagnetic field in internal or external space, and the common method to prevent this coupling is to shield the easily disturbed devices or circuits.
Radiation coupling: the radiation of electromagnetic field will also cause interference coupling, which is an irregular interference. This kind of interference is easily transmitted to the system through power lines. In addition, when the signal transmission lines are long, they can radiate and receive interference waves, which is the so-called big line effect.
Leakage coupling: The so-called leakage coupling is resistive coupling. This kind of interference often occurs when the insulation is reduced.
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I remember my previous point: decoupling capacitors generally have large capacity, which means to avoid noise coupling to other devices; The bypass capacitor has a small capacity and provides a low impedance noise return path.
In fact, this statement is not wrong. However, after occasionally consulting relevant information, it is found that there is basically no difference between decoupling and bypass, and they are interchangeable in terms of appellation. The function of the two is vulgar: as a power supply. The so-called noise is actually
It is the fluctuation of power supply, which comes from two aspects: the fluctuation of power supply itself, the voltage fluctuation caused by the change of load demand for current and the difference of corresponding capacity of power supply system. Decoupling capacitance and bypass capacitance are related to noise caused by load change. So the two of them don't have to do this.
Distinguish. Moreover, in fact, the size and number of capacitance values also have theoretical basis. If you choose it at will, you may encounter self-excited oscillation of decoupling capacitor (bypass) and distributed parameters in some cases. So the real decoupling and bypass are based on the load and power supply system.
According to the actual situation of the system. There is no need to make a distinction, and there is no essential difference.
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Capacitance is an essential component in circuit board design, and its quality has become a very important aspect for us to judge the quality of circuit boards. ......
What does the filter circuit mean by three decibels?
The output-input ratio (uo/ui) of the corner frequency point of the first-order filter circuit is 70%, which is expressed in decibels (db) according to the definition of Porter diagram.
Then 20LG (0.7) = 20 * (0.1549) =-3dB.
Does filtering in the circuit mean filtering?
It means filtering. Usually, the signal we understand is time-varying, that is, a function of time domain. In fact, we can transform it into frequency domain through equivalent transformation, that is, the variable is frequency. It is very convenient to analyze signals in frequency domain. Filtering refers to a signal processing operation in frequency domain, which filters out signals in some frequency bands and retains signals in other frequency bands.
What does the filter mean by popular?
Filters are used to filter electromagnetic waves, which have different frequencies. In order to avoid interference between frequencies, electromagnetic waves with unnecessary frequencies should be filtered by filters.
What is the main function of filtration?
The main function of filtering is to remove the AC component in the pulsating voltage and make it a smooth DC voltage.
This can avoid harmonic interference in the line.
What is the significance and function of rectification and filtering in the circuit? As detailed as possible! thank you
Simple, no details are needed. .
Rectifier: a circuit that converts alternating current into approximate direct current.
The most primitive rectifier circuit is a half-wave rectifier, that is, a diode is connected in series in the AC circuit, and the negative half-wave of AC is cut off by using the unidirectional conductivity of the diode, leaving only a positive half-wave with a half-wave slot in the middle. Because there is no negative half-wave, only the pulsating electromotive force of the positive half-wave, it is called a half-wave rectifier.
The higher stage is full-wave rectification, and four back-to-back diodes form a full-wave rectification circuit, which inverts the negative half-wave of alternating current and fills it in the time slot between two positive half-waves, so that the power supply current waveform becomes a continuous fluctuating approximate DC.
Filtering: Trim the approximate DC current with uneven waveform as flat as possible, or pick up the required frequency waveform in the circuit with many different frequency signals and remove other frequency waveforms.
The simplest filter is the power filter circuit. It says that full-wave rectification causes electromotive force fluctuation. A capacitor is connected in parallel with the output of the full-bridge rectifier circuit. By using the charging and discharging characteristics of the capacitor, the pulse current is charged when it reaches the peak, and discharged when it drops to the bottom of the curve, so as to supplement the current output and make the current waveform output to the load as straight as possible.
Or, in a circuit, only signals of a certain frequency are needed, but signals of other frequencies are mixed. Then, using the frequency sensitivity of RC circuit, an RC filter circuit sensitive to the frequency of useful signal is connected in series at the output end of the circuit, so that only the useful signal passes and other noise signals are blocked.
What does the power amplifier low-pass filter mean?
Just put down the low frequency and filter out the high frequency. The high frequency is generally used as the filter circuit of the subwoofer unit!
It's not easy to hit by hand. Please adopt it if it helps. Thank you! !