What is the role of safety capacitors in daily life?

Safety capacitors refer to safety capacitors that will not cause electric shock and do not endanger personal safety after the capacitor fails.

I believe that everyone is very clear about this, and today I will tell you about the application of safety capacitors in lifeThe definition of capacitors in physics is that a layer of insulator is sandwiched between two pieces of metal to form a capacitor, the role of the capacitor is to store electricity and discharge, and the capacitor unit is f, that is, volts.

Safety capacitors may be a little unfamiliar to some people, but if you use products that contain safety capacitors, you may not be so unfamiliar.

Safety capacitors are used in many electricity-related products, such as generators, pumps, etc.

Capacitor is simply a container of electricity, as a container of electricity, of course, the larger the capacity, the better, and now there are many people in the scientific community who are committed to the research and development of supercapacitors.

Capacitors are used in a wide range of applications in everyday life, and because they are a very small medium, they can be used in many places.

Since the Industrial Revolution, the world has begun to transition from the age of steam to the age of electricity, so the birth of capacitors is of great significance to the times.

The more power a capacitor can store, the more energy it can play, for example, today's mobile phones are getting thinner and thinner, and the most important reason is because the parts are getting smaller and smaller, but the role is getting bigger and bigger.

In the same way, the role of capacitors is the same, if the storage capacity can be increased to a higher level, in the future, in each electrical appliance or industrial use, the maximum benefit can be played with the smallest space.

This is also of cross-era significance for the electromechanical industry.

Nowadays, the types of capacitors are also divided into many kinds, such as ceramic safety capacitors, aluminum electrolytic safety capacitors, metallized polypropylene safety capacitors, etc., and the safety capacitors with multiple identities also play different roles in different places.

With the continuous progress of science, the medium is getting smaller and smaller, and mobile phones, computers, TVs, and tablets will become thinner and thinner.

When the capacitor can be stored and discharged to the extreme, the phone can become thinner and thinner, and the heat will become less and less.

The main function is to store electricity and phase deflection.

The functions of safety capacitors are as follows:

1. Safety capacitor, which can be divided into X capacitance and Y capacitance.

After the capacitor fails, it will not cause electric shock and endanger personal safety, and safety capacitors are usually only used for filtering in anti-interference circuits.

2. The discharge of safety capacitors is different from ordinary capacitors, the charge of ordinary capacitors will be retained for a long time after the external power supply is disconnected, and if you touch it by hand, it will be electrified, while safety capacitors have no problem. For safety and EMC considerations, safety capacitors are generally added to the power inlet.

3. At the input end of AC power supply, it is generally necessary to add 3 safety capacitors to suppress EMI conduction interference. They are used in power supply filters.

, it plays the role of power supply filtering, and plays a filtering role for common mode and differential mode interference.

Security Certifications:

As a safety capacitor, the Y capacitor must be certified by a safety testing organization. The appearance of Y capacitors is mostly orange or blue, and they are generally marked with safety certification marks (such as UL, CSA, etc.) and the words AC250V or AC275V for withstand voltage. However, its true DC withstand voltage is above 5000V.

It must be emphasized that the Y capacitor shall not be replaced by ordinary capacitors such as AC250V or DC400V with nominal withstand voltage.

Main Differences:

The discharge of safety capacitors is different from ordinary capacitors, which will retain their charge for a long time after the external power supply is disconnected, and will be charged if you touch it by hand, while safety capacitors have no problem. For safety and EMC considerations, it is generally recommended to add safety capacitors to the power supply inlet.

At the AC power input, it is generally necessary to add 3 safety capacitors to suppress EMI conducted interference. They are used in power supply filters to filter common mode and differential mode interference.

The safety capacitors in the power supply mainly have the functions of filtering and bypass.

1: Safety capacitors are used for filtering in the power supply.

Filtering is an important part of the role of safety capacitors. It is used in almost all power supply circuits. Theoretically, the larger the capacitance, the smaller the impedance and the higher the frequency at which it passes.

However, in fact, most capacitors over 1UF are electrolytic capacitors, which have a large inductance component, so the impedance increases when the frequency is high. Sometimes you will see a large capacitance electrolytic capacitor connected to a small capacitor in parallel, then the large capacitor passes on the low frequency and the small capacitor passes on the high frequency. The function of the capacitor is to pass high resistance and low resistance, and pass high frequency resistance and low frequency.

The larger the capacitance, the easier it is for low frequencies to pass through, and the larger the capacitance, the easier it for high frequencies to pass through. Specifically, it is used in filtering, with a large capacitance (1000uF) filtering low frequencies and a small capacitance (20pF) filtering high frequencies.

Safety capacitors are used as filter capacitors, which can be compared to "ponds". Since the voltage at both ends of the capacitor does not change abruptly, it can be seen that the higher the signal frequency, the greater the attenuation, but it is very figurative that the capacitor is like a pond, and will not cause a change in the amount of water due to the addition or evaporation of a few drops of water. It converts the change in voltage into a change in current, and the higher the frequency, the greater the current, thus buffering the voltage.

Filtering is the process of charging and discharging.

2. Safety capacitors are used as bypasses in the power supply.

A bypass capacitor is an energy storage device that provides energy to the local device, which can homogenize the output of the regulator and reduce the load demand. Like a small rechargeable battery, a bypass capacitor can be charged and discharged into the device. To minimize impedance, the bypass capacitor should be as close as possible to the power supply and ground pins of the load device.

This is a good way to prevent ground potential elevation and noise caused by too large input values. The ground bomb is the voltage drop at the ground junction when passing through a high-current burr.

Three: safety capacitors are used to remove lotus roots, also known as lotus roots.

In terms of circuits, it is always possible to distinguish between the source of the drive and the load being driven.

If the load capacitance is relatively large, the driving circuit should charge and discharge the capacitor in order to complete the signal jump, when the rising edge is relatively steep, the current is relatively large, so that the driving current will absorb a large power supply current, due to the inductance in the circuit, resistance (especially the inductance on the chip pins, will produce **), this current is actually a kind of noise relative to the normal situation, which will affect the normal operation of the pre-amp.

That's coupling.

The decoupling capacitor plays the role of a battery to meet the change of the current of the driving circuit and avoid coupling interference between them.

Combining a bypass capacitor with a decoupling capacitor will be easier to understand.

The bypass capacitor is actually decoupling, but the bypass capacitor generally refers to the high-frequency bypass, that is, to improve the high-frequency switching noise to improve a low-impedance leakage prevention path.

The high-frequency bypass capacitance is generally small, according to the resonant frequency, etc., while the decoupling capacitance is generally larger, 10uf or larger, according to the distribution parameters in the circuit, and the change of the driving current to determine.

Bypass is to filter out the interference in the input signal, while decoupling is to filter out the interference of the output signal to prevent the interference signal from returning to the power supply.

This should be their essential difference.

Fourth: the safety capacitor is used for energy storageThe energy storage capacitor collects the charge through the rectifier and transmits the stored energy to the output end of the power supply through the converter lead.

Aluminum electrolytic capacitors with a voltage rating of 40 450 VDC and a capacitance between 220 and 150000 UF (e.g. B43504 or B43505 from EPCOS) are more commonly used.

Depending on the power supply requirements, the devices are sometimes connected in series, parallel, or a combination thereof, and for power supplies with power stages of more than 10 kW, bulky screw terminal capacitors are usually used.

Applied to the signal circuit, mainly to complete the coupling, oscillation synchronization and time constant of the role of the fifth: safety capacitor for coupling with the transistor amplifier emitter has a self-sufficient bias resistor, it also makes the signal produce voltage drop feedback to the input terminal to form an input and output signal coupling, this resistance is the element that produces coupling, if a capacitor is connected in parallel at both ends of this resistor, because the capacitor of the appropriate capacity has a smaller impedance to the AC signal, so the coupling effect of the resistance is reduced, so this capacitor is called the decoupling capacitor.

6. Safety capacitors for oscillation Synchronous load capacitors, including RC, LC oscillators and crystals, belong to this category.

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The role of safety capacitors: safety capacitors are used in such occasions, even if the capacitor fails, it will not cause electric shock and will not endanger personal safety. It includes two types: X capacitor and Y capacitance.

The X capacitor suppresses differential-mode interference in the circuit, and the Y capacitor suppresses common-mode interference. Generally, the X capacitance is microfar-class, and the Y-capacitance is nanofar-class.

Safety capacitors are used in such occasions that after the capacitor fails, it will not cause electric shock and will not endanger personal safety.

It includes two types of X capacitors, X capacitors are capacitors that are connected between two lines of power lines (L-N), and metal film capacitors are generally selected; Y capacitors are capacitors that are crossed between two wires of a power line and ground (L-E, N-E) respectively, and generally appear in pairs. Based on the limitation of leakage current, the value of Y capacitance should not be too large, generally the X capacitance is UF class, and the Y capacitance is NF class. The X capacitor suppresses differential-mode interference, and the Y-capacitor suppresses common-mode interference.

Their security levels are listed in the table below:

Safety Capacitor Safety Level Allowable peak impulse voltage in the application Overvoltage level (IEC664).

x1 >

x2 ≤ x3 ≤

Safety Capacitor Safety Level Insulation Type Rated Voltage Range.

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