What are the similarities and differences between the polar and non-polar capacitors in terms of performance and principle structure?
A polar capacitor refers to a capacitor such as an electrolytic capacitor. It is formed by an aluminum foil of an anode and an electrolyte of a cathode, respectively, and two electrodes are formed by an aluminum oxide film formed on the anode aluminum foil as a dielectric capacitor. The structure has a polarity. When the capacitor is positively connected, the aluminum oxide film will remain stable due to the electrochemical reaction. When the connection is reversed, the aluminum oxide layer will become thinner, so that the capacitor is easily damaged by breakdown. Therefore, the electrolytic capacitor is The circuit must pay attention to the polarity. The ordinary capacitor is non-polar, and the two electrolytic capacitor anodes or cathodes can be connected in series to form a non-polar electrolytic capacitor.
1. The principle is the same. (1) Both store the charge and release the charge; (2) The voltage on the plate (where the electric potential of the charge builds is called the voltage) cannot be abruptly changed.
2. The media is different. What is the medium? To put it bluntly is the substance between the two plates of the capacitor. Most of the polar capacitors use electrolyte as the dielectric material, and usually the same volume of capacitor has a large capacitance capacity. In addition, different electrolyte materials and processes produce polar capacitors with the same volume capacity. There is also a close relationship between pressure resistance and the use of dielectric materials. There are also many non-polar capacitor dielectric materials, mostly using metal oxide film, polyester and so on. Due to the reversible or irreversible performance of the medium, the environment with extreme and non-polar capacitance is determined.
3. Performance is different. Performance is the requirement of use, and maximizing demand is the requirement for use. If the power supply part of the TV is filtered with a metal oxide film capacitor, and the capacitor capacity and withstand voltage required for filtering are to be achieved. I am afraid that I can only install a power supply inside the case. Therefore, as a filter, only polar capacitors can be used, and polar capacitors are irreversible. That is to say, the positive pole must be connected to the high potential end, and the negative pole must be connected to the low potential end. Generally, the electrolytic capacitor is above 1 microfarad, and it is used for coupling, decoupling, and power supply filtering. Most of the non-polar capacitors are below 1 microfarad, participating in resonance, coupling, frequency selection, current limiting, and so on. Of course, there is also a large capacity and high withstand voltage, which is often used in the reactive power compensation of electric power, the phase shifting of the motor, and the variable frequency power supply. There are many types of non-polar capacitors, not to mention them one by one.
4, the capacity is different. As mentioned above, capacitors of the same volume have different capacities and are not described one by one. 5. The structure is different. In principle, it is possible to use a capacitor of any shape in the environment in which the tip discharge is not considered. Commonly used electrolytic capacitors (having a polar capacitor) are circular, and the square shape is rarely used. The shape of the non-polar capacitor is very varied. Like tube type, deformed rectangle, sheet type, square type, round type, combined square type and round type, etc., it is used where it is used. Of course, there is invisible, here the invisible refers to the distributed capacitance. For distributed capacitors, high frequency and intermediate frequency devices must not be ignored. The function is the same. The main difference is that in terms of capacity, due to the influence of material structure, the capacity of general non-polar capacitors is relatively small, generally below 10uF, and the capacity of polar capacitors is generally large. For example, when power filtering, you have to use a large capacity of polar capacitors.
A basic principle of circuit design is to require designers to fully understand and master the real-world components. The components used are standard parts and common parts. It is best to be the most common type on the market (the versatility of components is better. The easier it is to purchase, the higher the supplier's output and the lower the procurement cost. For the components used in the drawings, if the materials are only available for customization, the cost is certainly not low. If it is not available, then this design is equivalent to waste paper.
In addition, large capacitors are suitable for filtering low-frequency signals, and small capacitors are used for filtering high-frequency signals (see the circuit basis, capacitive reactance and frequency). However, decoupling is only one function of the capacitor. Capacitors have other functions. Different types of capacitor characteristics have different usages. The capacitor on the schematic is just a symbol. There are many techniques behind it. This aspect is closely related to experience. It is impossible to be quick and can only be accumulated slowly through practice.