CN201663544U - Filtering module with anti-electromagnetic interference and transient suppression functions - Google Patents

Abstract

The utility model discloses a filtering module with anti-electromagnetic interference and transient suppression function, include: the transient suppression circuit comprises a gas discharge tube, a first inductor, a transient suppression diode, a second inductor, a first capacitor and a second capacitor; the first end of the gas discharge tube is connected with the first end of the first inductor; the second end of the first inductor is connected with the first end of the transient suppression diode, the first end of the first capacitor and the first end of the second inductor; the second end of the second inductor is connected with the first end of the second capacitor; the second end of the gas discharge tube, the second end of the transient suppression diode, the second end of the first capacitor and the second end of the second capacitor are connected and are all grounded; a first terminal of the gas discharge tube and a first terminal of the second capacitor are connected to a load. The filtering module has three functions of peak transient pulse suppression, surge suppression and EMI suppression, reduces the volume for realizing the same effect, reduces the purchase cost of users, and improves the competitiveness of products.

Description

Filter module with anti-electromagnetic interference and transient suppression functions

technical field

The utility model relates to a filter module, in particular to a filter module with functions of anti-electromagnetic interference and electromagnetic immunity. the

Background technique

Electronic systems and network lines are often disturbed by external transient overvoltages. These interference sources mainly include: operating overvoltages caused by switching inductive loads or starting and stopping high-power loads, line faults, etc.; caused by natural phenomena such as lightning lightning surge. This overvoltage (or overcurrent) is called surge voltage (or surge current), which is a kind of transient interference. Surge voltage can seriously endanger the safe operation of electronic systems. Eliminating surge noise interference and preventing surge hazards have always been the core issues related to the safe and reliable operation of electronic equipment. In order to prevent the surge voltage from damaging electronic equipment, shunt defense measures are generally adopted, that is, the surge voltage is shorted to the ground in a very short period of time, so that the surge current is shunted into the ground, so as to weaken and eliminate overvoltage and overcurrent. So as to protect the safe operation of electronic equipment. the

At present, the electromagnetic interference filter is the most important means to suppress conducted interference and has been widely used in various military equipment and civilian equipment. The surge suppression devices used in traditional EMI filters are generally gas discharge tubes, transient voltage suppressors, and silicon diodes. The working principles of these devices are different, but they have similar volt-ampere characteristics, that is, when the voltage at both ends is lower than the specified voltage, the passing current is very small, and when the voltage at both ends is higher than the specified voltage, the passing current will increase exponentially. This volt-ampere characteristic enables it to meet the requirements of surge suppression effusion and limiting at the same time, so it becomes the leading device for surge suppression. the

Using one of the above-mentioned devices alone, although both have a certain inhibitory effect on the spike voltage, each has its own shortcomings. For example, the residual voltage of gas discharge tube is high, the response time is slow (≤100ns), the action voltage accuracy is low, and there is following current (freewheeling); while the transient voltage suppressor has poor current resistance and small flow capacity, generally only a few hundred amps. Therefore, according to specific application occasions, one or a combination of several of the above-mentioned devices is generally used to form a corresponding protection circuit. the

However, the existing electromagnetic interference filters using the above-mentioned devices have poor suppression effects on transient oscillations lasting more than several milliseconds, surge voltages, and spike voltages on nanosecond-level rising edges, and cannot simultaneously satisfy the above-mentioned suppression requirements. interfering requirements. Moreover, the existing filtering device is bulky and takes up a lot of space. If it is necessary to simultaneously suppress transient oscillations lasting more than several milliseconds, surge voltages, and spike voltages for nanosecond-level rising edges, different suppression devices need to be purchased, resulting in increased costs. the

Therefore, there is a need for a filter module with an improved combination function, which has a good suppression effect on transient oscillations lasting more than several milliseconds, surge voltages, and spike voltages on nanosecond-level rising edges, and effectively improves weaponry. And the ability of civilian equipment to deal with complex electromagnetic effect environments. And it is hoped that the filter module is small in size and low in cost, so as to increase product competitiveness, thereby rapidly changing the backward state of my country's current military equipment (system). the

Contents of the invention

Therefore, the purpose of this utility model is to provide a filter module that can overcome the above-mentioned disadvantages. the

According to an embodiment of the present utility model, the filtering module with combination function includes:

Gas discharge tube, first inductor La, transient suppression diode V2, second inductor Lb, first capacitor C1 and second capacitor C2; where,

The first end of the gas discharge tube V1 is connected to the first end of the first inductor La; the second end of the first inductor La is connected to the first end of the transient suppression diode V2, the first The first end of the capacitor C1 is connected to the first end of the second inductance Lb; the second end of the second inductance Lb is connected to the first end of the second capacitor C2; the gas discharge tube V1 The second terminal, the second terminal of the transient suppression diode V2, the second terminal of the first capacitor C1 and the second terminal of the second capacitor C2 are connected to each other, and are all grounded; the gas discharge tube V1 The first terminal of the first capacitor and the first terminal of the second capacitor C2 are connected to a load. the

Therefore, the utility model organically integrates the three major functions of peak transient pulse suppression, surge suppression and EMI suppression in the same anti-electromagnetic interference (EMI)/electromagnetic immunity (EMS) combined function power filter device, The volume to achieve the same effect is reduced, the purchase cost of the user is reduced, and the competitiveness of the product is improved. At present, there is no similar product in China. The successful research and development of the product can fill the gap in domestic products, effectively improve the ability of weapons and equipment to deal with complex electromagnetic effect environments, and achieve good economic benefits. the

Description of drawings

In order to explain the utility model, the following will describe the exemplary embodiment of the utility model with reference to the accompanying drawings, wherein:

Figure 1A shows a schematic diagram of the change in voltage of the switch at the moment of disconnection;

Figure 1B shows a schematic diagram of the principle of electrical fast transient burst generation;

Fig. 2A shows the waveform diagram of single transient pulse signal;

Fig. 2 B shows the repetition rate schematic diagram of electrical fast transient burst;

Fig. 3 shows the schematic circuit diagram of the filtering module according to an embodiment of the present utility model;

Fig. 4 shows the insertion loss curve of the EMI/EMS combined function DC power filter module according to a new embodiment of the present invention;

Fig. 5 shows a schematic diagram of the shell size of a DC power filter module with combined EMI/EMS functions according to a new embodiment of the present invention. the

Detailed ways

The filter module disclosed by the utility model includes a gas discharge tube, a transient suppression diode and a first-stage filter circuit, wherein the gas discharge tube and the transient suppression diode are combined to form a peak and surge suppression circuit, and further combined with the first-stage filter circuit The suppression of peak, surge interference and conduction interference can be realized at the same time, so as to realize high insertion loss and small volume passive electromagnetic interference filter module. the

As is known, electronic systems and network lines are often interfered by external transient signals, such as fast transient bursts, surge signals, and the like. the

Electrical Fast Transient Bursts

Fast transient bursts will cause digital system bit errors, system resets, memory errors, and freezes. At the IC input, the fast transient burst charges the parasitic capacitance, accumulates, and finally reaches and exceeds the immunity level of the IC chip. It may be the case that a few pulses (or bursts of short duration) will not cause the digital system to fail, whereas bursts of long duration will disable the device. Each logic component of the microprocessor and peripheral devices has a corresponding level and noise tolerance. As long as the external noise does not exceed the tolerance value of these components, the system can maintain normal; once the noise that invades the system exceeds a certain tolerance, Just may cause the microprocessor system to go wrong, become the important reason of device misoperation, refusal to move. the

Electrical fast transient bursts are generated during switching inductive load transients, such as a series of short rise time, high repetition rate and low energy transients caused by relay contact bounce action, motor, timer, etc. interfering bursts. FIG. 1A and FIG. 1B take the discharge process between mechanical switch contacts as an example to illustrate the physical process of electrical fast transient bursts. FIG. 1A shows a schematic diagram of the voltage change of the switch at the moment of turning off, and FIG. 1B shows a schematic diagram of the principle of generating electrical fast transient bursts. the

As shown in Figure 1A, when the switch contact is disconnected, since the current in the inductive load (such as an inductor) cannot change abruptly, a high counter electromotive force will be generated on the inductive load to maintain the original current. According to Lenz's law, this The electromotive force E is:

E＝dФ/dt＝-L(di-dt)

Among them, Ф is the magnetic flux in the inductor, L is the inductor, i is the current flowing in the inductor, and t is the time. When the switch is turned off, to maintain the current in the inductor, only the air between the contacts is broken down and the arc is used to conduct. Arc means that when the electric field strength applied to the gas is strong, the free electrons or ions in the gas can gain enough energy to hit other atoms or molecules, resulting in a glow discharge, thus generating more free electrons and ions, forming a conductive gas. This glow discharge can produce strong electromagnetic radiation. the

Referring to Figure 1B, assuming that the contacts gradually separate from t ₀ , when the voltage between the contacts (V ₁ ) exceeds the insulation voltage, a spark discharge occurs between the contacts, causing the voltage between the contacts to drop instantaneously, reaching t ₁ zero. At this time, because there is still energy in the inductance, the voltage between the contacts begins to rise again. As the distance between the switch contacts continues to increase, the voltage of spark discharge between the contacts also increases correspondingly. When the voltage (V ₂ ) exceeds the insulation voltage again, a second spark discharge occurs. Similarly, after the second spark discharge occurs, the voltage between the contacts drops instantly, reaches zero at _t2 , and then rises slowly, and then the third (V ₃ ) and fourth (V ₄ ) can be generated.. .Spark discharge. When the distance between the contacts is large enough, glow discharge can occur between the contacts, at this time all the energy in the inductor is consumed, and the discharge process ends. For the AC 220V power grid, the voltage amplitude of this electrical fast transient burst can reach as many as several thousand volts. In the electrical fast transient pulse group, the rising edge of a single pulse is at the nanosecond level, and the pulse duration is tens of nanoseconds to several milliseconds. Refer to FIG. 2A and FIG. 2B , wherein FIG. 2A shows a schematic waveform diagram of a single transient pulse signal, and FIG. 2B shows a schematic diagram of a repetition frequency of an electrical fast transient pulse group.

The electrical fast transient burst may be coupled to the internal circuit of the device through the power port and signal port of the electrical and electronic device, affecting the normal operation of the device and causing damage to the device and the system connected to it. Electrical fast transient bursts are very destructive to instruments and equipment, especially for high-power and sensitive instruments and equipment, special attention should be paid. the

surge signal

A surge signal is a transient signal of current, voltage or power propagating along a line, characterized by a rapid rise and then a slow fall. Surges are caused by switching and lightning transient voltages, where switching transients are related to: mains power system switching disturbances, such as switching of capacitor banks; slight switching activity or load changes in the vicinity of instruments within the distribution system; and Resonant circuits related to switching devices, such as thyristors; various system faults, such as short circuits and arc faults to the grounding system of the equipment group. The principle of surge voltage generated by lightning is as follows: direct lightning strikes the external circuit, and the injected large current flows through the grounding resistance or external circuit impedance to generate voltage; indirect lightning strike can induce voltage and current on the internal and external conductors of the building; The lightning current of the lightning discharge to the ground is coupled to the common grounding path of the equipment group grounding system. When the arrester operates, voltage and current may change rapidly and may couple into internal circuits. These voltages or currents that are directly injected or coupled into the device will not only damage the device, but also affect adjacent devices or even the entire system. the

Although gas discharge tubes and TVS diodes have different working principles, they have similar volt-ampere characteristics, that is, when the voltage at both ends is lower than the specified voltage, the passing current is very small, and when the voltage at both ends is higher than the specified voltage, the passing current will decrease. exponential growth. This volt-ampere characteristic enables it to meet the requirements of surge suppression, effusion and limiting at the same time. Therefore, gas discharge tubes and transient suppression diodes are often used to suppress interference signals such as surge signals and electrical fast transient bursts. the

gas discharge tube

Gas discharge tubes can be used for surge protection in data lines, cable television, AC power, telephone systems, etc. The general device voltage ranges from 75 to 10,000V, the peak impact current is 20,000A, and it can withstand discharges of up to several thousand joules. the

The main parameters of the gas discharge tube include:

1) The response time refers to the time from when the applied voltage exceeds the breakdown voltage to when the breakdown occurs. The response time of the gas discharge tube is generally in the order of μs. the

2) Power capacity refers to the maximum energy that a gas discharge tube can withstand and dissipate, which is defined as the current that can be withstood and dissipated under a fixed current waveform of 8×20μs. the

3) Capacitance refers to the capacitance between the two poles of the gas discharge tube measured at a specific frequency of 1MHz. The capacitance of the gas discharge tube is very small, generally ≤1pF. the

4) DC breakdown voltage When the applied voltage rises at a rate of 500V/s, the voltage when the discharge tube generates sparks is the breakdown voltage. Gas discharge tubes have a variety of DC breakdown voltages with different specifications, and their values depend on factors such as the type of gas and the distance between electrodes. the

5) Temperature range The working temperature range is generally between -55°C and +125°C. the

The advantages of gas discharge tubes are large flow capacity, high insulation resistance, and small leakage current; their disadvantages are high residual voltage, slow response time (≤100ns), low accuracy of operating voltage, and following current (freewheeling). the

Transient Suppressor Diodes (TVS)

Also known as Zener diode, it is a device specially used to suppress overvoltage. Its core part is a PN junction with a large cross-sectional area. When the PN junction works in an avalanche state, it has a strong pulse absorption capability. the

The advantages of TVS diodes are low residual voltage, high action accuracy, fast response time (<1ns), and no following current (freewheeling); its disadvantages are poor current resistance and small flow capacity, generally only a few hundred amperes. the

The inventor of the utility model believes that the key to realize high insertion loss and small size passive EMI filter is to correctly select the magnetic core material and the number of stages to form the circuit under the premise of limited volume and rated power. Therefore, according to one embodiment of the present invention, the filter module is used as a DC power filter, which includes a gas discharge tube, a TVS diode and a primary filter circuit, wherein the combination of the gas discharge tube and the TVS diode forms a peak, Surge suppression circuit, and further combined with a first-stage filter circuit can simultaneously suppress the suppression of spikes, surge interference and conduction interference. the

Fig. 3 shows a schematic circuit diagram of a filter module according to an embodiment of the present invention. As shown in the figure, the left half of the circuit uses a peak and surge suppression circuit that combines a gas discharge tube and a transient suppression diode. Because the transient suppression diode has the characteristics of fast response but small flow rate, and the gas discharge tube has the characteristics of large flow rate but slow response and high residual voltage, the combined use of the two can eliminate each other's shortcomings and achieve the peak and surge suppression circuit design. Require. The right half of the circuit adopts π-type filter circuit, which can effectively suppress common-mode interference and meet the requirements of GJB 151A. And it can be seen that the filter module combines the functions of anti-electromagnetic interference and electromagnetic susceptibility (EMS), and has surge and spike suppression characteristics, which can make military equipment or civilian equipment using this filter module meet GJB151A-97: CE102, CE107, Specification requirements such as CS106 and GJB1389A. the

In Figure 3, V1 represents the gas discharge tube, La represents the first inductance (such as a differential mode inductor), Lb represents the second inductance (such as a differential mode inductor), V2 represents a TVS diode, and C1 represents the first capacitor (such as a patch Capacitor), C2 represents the second capacitor (such as chip capacitor). the

Specifically, the first end of the gas discharge tube V1 is connected to the first end of the first inductor La; the second end of the first inductor La is connected to the first end of the transient suppression diode V2, the The first end of the first capacitor C1 is connected to the first end of the second inductance Lb; the second end of the second inductance Lb is connected to the first end of the second capacitor C2; the gas discharge The second end of the tube V1, the second end of the transient suppression diode V2, the second end of the first capacitor C1, and the second end of the second capacitor C2 are connected, and are all connected to ground; The first end of the gas discharge tube V1 and the first end of the second capacitor C2 are connected to a load. the

The operating temperature range of the filter module is -55°C～+105°C/-85°C～+125°C, its rated voltage is 28/VDC, rated current is 3A, attenuation at 500KHz, 40dB and 1MHz, 50dB. the

Fig. 4 shows the insertion loss curve of the EMI/EMS combined function DC power filter module according to the embodiment of the present utility model. Since the two phase wires of the filter module circuit are positive and ground respectively, the insertion loss only has common mode insertion loss and no differential mode insertion loss. the

The surge suppression characteristics of the filter module according to the embodiment of the present utility model are as follows: maximum line current: 3A, maximum line voltage: 28VDC, leakage current (at rated voltage): <0.1mA, nominal discharge current (8/20μs, 10times): 10KA, maximum discharge current (8/20μs, 1times): 20KA, working temperature: -25℃-+85℃, protector failure: short circuit. the

In addition, in order to help those skilled in the art to implement the filter module, FIG. 5 shows a schematic diagram of the shell size of the DC power filter module with combined EMI/EMS functions. the

Although exemplary embodiments are disclosed herein, using specific terms, and specific component names and dimensions, these terms and specific component names and dimensions are used for purposes of illustration and description only, and not for Restricted Purposes. Accordingly, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as defined by the appended claims. the

Claims (1)

1. A filter module with anti-electromagnetic interference and transient suppression functions, comprising: Gas discharge tube (V1), first inductor (La), transient suppression diode (V2), second inductor (Lb), first capacitor (C1) and second capacitor (C2); wherein, The first end of the gas discharge tube (V1) is connected to the first end of the first inductance (La); the second end of the first inductance (La) is connected to the transient suppression diode (V2) The first end, the first end of the first capacitor (C1) and the first end of the second inductance (Lb) are all connected; the second end of the second inductance (Lb) is connected to the second end of the second capacitor (C2) is connected to the first end; the second end of the gas discharge tube (V1), the second end of the transient suppression diode (V2), the second end of the first capacitor (C1) and the The second end of the second capacitor (C2) is connected to the ground, and the first end of the gas discharge tube (V1) and the first end of the second capacitor (C2) are connected to a load. the

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