The difference between TVs diodes and Zener diodes

The difference between TVs diodes and Zener diodes

When the TVs tube exceeds its withstand voltage, it will momentarily short-circuit the reaction speed at the NS level,

And the regulator is the regulator, more than its voltage regulator value, as long as the power does not exceed its tolerance value, it will be stable in its regulated value range.

TVS is a transient suppression diode that is mainly used to suppress instantaneous voltage spikes and reduce the loss of the component by the spike voltage.

Voltage regulator diode is mainly the role of the regulator.

A bidirectional breakdown diode, also known as a transient voltage suppressor diode (TVS), is an overvoltage protection device with bidirectional voltage-stabilizing characteristics and bidirectional negative resistance, similar to Varistors.

It is used in a variety of AC and DC power circuits to suppress transient overvoltage.

When the protected circuit instantaneous surge pulse voltage, two-way breakdown diode can quickly zener breakdown, from the high-impedance state into a low-impedance state, the surge voltage shunt and clamp, so as to protect the circuit components from the instantaneous surge pulse voltage damage.

Voltage regulator principle of Zener diode:

The characteristic of voltage regulator diode is that after breakdown, the voltage at both ends is basically unchanged.

In this way, when the regulator is connected to the circuit, if due to fluctuations in the supply voltage, or other causes of voltage fluctuations in the circuit, the load on both ends of the voltage will remain basically unchanged.

Fault characteristics: Voltage Regulator diode failure is mainly manifested in open circuit, short-circuit and unstable voltage stability.

In these 3 kinds of faults, the previous fault shows the increase of supply voltage.

The following 2 types of faults show that the supply voltage becomes low to 0 volts or the output is unstable.

Commonly used Zener diode model and voltage regulator values are as follows:

Model 1n4728 1n4729 1n4730 1n4732 1n4733 1n4734 1n4735 1n4744 1n4750 1n4751
Regulated value 3.3V 3.6V 3.9V 4.7V 5.1V 5.6V 6.2V 15V 27V 30V

In short, the Transient voltage suppression diode (TVS) is not penetrated, it can reduce the resistance when the voltage is very high,

So that the current shunt or control its flow, so as to protect the circuit elements in the transient voltage is too high in the case of not be burnt-out regulators can be penetrated,

But the voltage at the ends of the breakdown remains constant, so that the circuit is stable and the voltage is stable, so that the circuit element is protected from an open circuit.

The reaction speed of the transient suppression diode is fast, and the pulse spike with the elimination of interference is used.

The most important feature of Varistors is that when the voltage above it is lower than its threshold "UN", the current flowing through it is very small, equivalent to a dead valve,

When the voltage exceeds UN, the current flowing through it surges, equivalent to opening the valve.

This function can suppress the abnormal overvoltage in the circuit and protect the circuit from the voltage damage.

The voltage regulator diode reverse voltage to a certain extent will penetrate, yes, is stable, for the regulator.

The transient suppression diode is a variant of the avalanche diode (regulator tube)!

The characteristic is that the current in the rated working area is very small! The current is greatly increased after overpressure!

The difference between a transient suppression diode and a Zener diode is that the former works in the cutoff area!

The latter works in the conduction zone!

And the pressure-sensitive group is composed of two ends fusible conductive inner sandwich resistance film!

Under normal conditions it is a fixed value resistor! When the voltage high current is too large, the film will penetrate the melting ends of the fusible conductor!

To protect other components of the circuit by short circuit or circuit breaker!

Transient diodes (Transient Voltage suppressor)

Referred to as TVs, is a high-performance protection device in the form of diodes.

When the two poles of a TVs diode are subjected to a reverse transient high-energy shock, it can change the high impedance of the two poles to a low impedance at a rate of 10 minus 12 seconds.

Absorbs up to thousands of watts of surge power, allowing the voltage between the poles to be clamped to a predetermined value to effectively protect the precision components in the electronic circuitry from the damage of various surge pulses.

CharacteristicsTVS have the same circuit symbols as regular zener diodes. its forward characteristic is the same as the ordinary diode, and the reverse characteristic is typical PN junction avalanche device.   in the transient peak current pulse, the current flowing through the TVS, from the original reverse leakage current ID rose to the IR, its bipolar voltage from the rated reverse shutdown voltage VWM rise to the breakdown voltage Vbr,tvs is penetrated.   With the advent of peak pulse currents, the current flowing through TVs reaches the peak current pulse IPP. The voltage at its poles is clamped below the predetermined maximum clamping voltage. Thereafter, as the pulse current is attenuated exponentially, the voltage on the TVS poles is also declining and finally returning to the starting state. This is the whole process of TVs suppressing the potential surge pulse power to protect electronic components.   parameter ① maximum reverse leakage current ID and rated reverse shutdown voltage VWM. The VWM is the maximum continuous DC or pulse voltage of the TVs, when the reverse voltage is added to the TVs ' poles, it is in a reverse shutdown state, and the current flowing through it should be less than or equal to its maximum reverse leakage current ID.  ② minimum breakdown voltage VBR and Breakdown current IRVBR is the smallest avalanche voltage in TVs. At 25 ℃, TVS are not conductive until this voltage is applied. When TVs flows through the specified 1mA current (IR), the voltage between the TVs poles is added to its minimum breakdown voltage VBR. According to the discrete degree of VBR and standard value of TVs, TVs can be divided into two kinds of ±5%VBR and ±10%VBR. For ±5%VBR, VWM=0.85VBR; for ±10%VBR, VWM=0.81VBR.  ③ Maximum clamping voltage VC and Maximum peak Pulse current IPP the maximum peak voltage that occurs between its poles is VC when the pulse-peak-currents IPP, which has a duration of 20 microseconds, flows through TVs. It is a combination of a series resistor and a voltage rise due to a temperature coefficient. VC and IPP reflect the surge suppression capability of TVS devices. The ratio of VC to VBR is called clamping factor, usually between 1.2~1.4.  ④ capacitance c capacitance C is determined by the TVs Avalanche Junction section, measured at a specific 1MHZ frequency. The size of C is proportional to the current withstand capacity of TVs, and C is too large to attenuate the signal. Therefore, C is an important parameter of selecting TVs for data interface circuit.  ⑤ Maximum peak pulse power dissipation pmpm is the maximum peak pulse dissipation power that TVs can withstand. For the specified test pulse waveform and the various TVs PM values, please refer to the relevant product manuals. At a given maximum clamping voltage, the larger the power consumption pm, the greater the withstand capacity of the inrush current, and the lower the clamp voltage VC under a given power consumption pm, the greater the withstand capacity of its inrush current. In addition, peak pulse power consumption is also related to pulse waveform, duration and ambient temperature. And the transient pulses that TVs can withstand are non-repetitive, and the pulse repetition frequency specified by the device (duration and intervalRatio) is 0.01%, if repetitive pulses occur within the circuit, the "accumulation" of pulse power should be considered, potentially damaging the TVs. The  ⑥ clamping time TCTC is the time at which TVs have voltages from zero to the minimum breakdown voltage VBR. The unipolar TVs are generally 1x10-12 seconds, and the bipolar TVs are typically 1x10-11 seconds.   Pressure Protection (a): analysis of the working principle of TVs tube, the role of TVs transient suppression of the two-polar tube

In the case of a voltage device, the application of TVs two is extremely broad, and as an engineer, it is necessary to understand the working principle, characteristic parameters, sealing form, etc. of TVs two pole.

And with the familiarity of TVs two pole count, the role of the engineer can be the edge of the rest of the customer to do TVs two-pole selection of reference.

In the case of TVs two, some of the questions that novice engineers must ask are:

How does the TVs two polar tube work?

Does the TVs tube have positive and negative polarity?

The characteristic parameters of TVs tubes, the selection criteria of TVs tubes, and the effect of TVs transient suppression of two-polar tubes.

With this issue of protection, little masters for all of the engineers and acquisitions that focus on TVs transient suppression of the two-polar tubes. The protection of the TVs tube.

The first thing to know is the TVs transient suppression diodes, the instantaneous suppression of the two polar tubes (Transient Voltage suppressor) simply called the TVs tube,

The electrical characteristics of TVs tubes are determined by the p-n, blended, and wafer resistance.

Its ability to withstand surge currents is proportional to its p-n. When the TVs two polar is subjected to a reverse transient high-energy shock,

It can change the high impedance of its two poles to a low impedance at a rate of 10 minus 12 seconds, absorbing the surge power of high kw

The two-polarity voltage is clamped to a predetermined value, effectively bunkers the precision components in the protection circuit from the damage of various waves.

How TVs Tubes work:

The device is in the electrical circuit, and when the circuit is working normally, it is in the cutoff state (high impedance), and does not affect the normal operation of the circuit,

When the circuit is constantly stressed and reaches its hit-and-run voltage, it quickly changes from high impedance to low impedance, providing a low resistance path to the transient current,

At the same time, the abnormal high pressure clamp in a safe level, from the protection of the IC or circuit;

When the pressure disappears, it is restored to a high impedance and the circuit works normally.

TVS allows the forward-wave currents to reach 50~200a under ta=250c,t=10ms conditions.

The two-way TVs absorb instantaneous power in both directions and fangs the voltage to a predetermined level,

The dual-channel TVs are suitable for use on AC power, and are generally used on direct-current TVs.

It is an ideal protection device for lightning protection, anti-voltage, anti-interference, absorbing wave power and so on. Tolerance is expressed in Watts (W).

TVS two tubes can be easily integrated with other devices on a single chip, and there are a number of devices that integrate EMI-discard and RFI protection features with TVs tubes,

Not only reduces the number of devices used to reduce costs, but also to avoid the PCB board on the wire easily lure the associated self-inductance.

Anti-stress Protection (ii): TVs transient suppression two-pole choice, TVs two polar select parameters Analysis

In the previous article, Little Masters introduced what is the working principle of TVs transient suppression diodes, TVs two poles, and the role of TVs tubes,

Even novice engineers are well aware of the TVs two tubes for customers who need them.

But want to be independent of the customer's TVs tube selection, or to understand the instantaneous suppression of the two-polar tube selection techniques and selection parameters.

Masters, who is the best known novice engineer, has long been considering this noodle. For this issue, there is an urgent need for a novice engineer to suppress the two-pole selection of the diodes and TVs two polar select parameters.

The best way to handle transient pulse damage is to bring the instantaneous current from the sensing element.

The TVs two pole is on the circuit board with the protected line, and when the transient voltage is over the circuit, the voltage

The TVs two pole produces an avalanche that provides an ultra-low resistive path to the instantaneous current, which results in instantaneous currents being induced through the two-polar tubes,

Avoid the protected element and keep the protected circuit off voltage until the voltage is normal.

When the instantaneous pulse ends, the TVs two tubes the high impedance, and the entire circuit enters normal voltage.

Many components are subjected to multiple attacks and their parameters and performance degrade,

and to work within limits, the two poles will not be damaged or degraded.

As you can see from the above process, there are a couple of options to be aware of in the TVs two polar selector:

1. Minimize the power-on voltage VBR and attack-through current IR.

VBR is the smallest hit-and-wear voltage in TVs, which, at 25 ℃, does not produce avalanches as low as this voltage TVs.

When TVs flows through a 1mA current (IR), it is added to TVs's two-pole voltage for its minimum attack on the voltage v BR.

VBR can be divided into 5% and 10% according to the dispersion of the VBR and standard values of TVs.

For a VBR of 5%, VWM =0.85VBR, V WM =0.81VBR for 10% VBR.

To meet the Iec61000-4-2 international standard, TVs two tubes must be able to handle the minimum 8kV (touch) and 15kV (air) ESD attacks,

Some semi-directors have used higher anti-shock standards on their products.

For certain carrying equipment with special requirements, the designer can select the components according to their needs.

2. Maximum reverse leakage current ID and additional reverse-cut voltage vwm.

The VWM is a two-pole voltage that can withstand normal condition, which is greater than or equal to the normal operating voltage of the protected circuit,

Otherwise, the diodes will keep the cutoff loop voltage, but it needs to be close to the normal operating voltage of the protected circuit,

This will not cause the entire loop to be threatened before the TVs work.

When this counter-cut voltage VWM is added to the TVs at the two poles it is in reverse state, streaming its current is less than or equal to its maximum reverse leakage current ID.

3. Maximum fangs bit voltage VC and maximum peak pulse current I PP.

The maximum peak voltage that is present at both ends of the 20ms peak current-stream IPP when it passes through TVs is VC.

V C, IPP reflects the ability of TVs to suppress the surge.

The ratio of VC to VBR is referred to as fangs factor, usually between 1.2~1.4. The VC is the voltage provided by the two pole in the cut-off state, that is, the voltage of the TVs through the ESD Impulse,

It cannot be larger than the tolerable voltage of the protected circuit, or the component is at risk of damage.

4. PPPM Pulse Power,

This is based on the maximum cutoff voltage and the peak pulse current at this time.

For handheld equipment, the 500W TVs are generally enough.

The maximum peak pulse power consumption PM is the maximum peak power consumption value that TVs can withstand.

The larger the power consumption pm, the greater the withstand power of the surge current in a given maximum fangs bit voltage.

Under a specific power consumption pm, the lower the fangs-bit voltage VC, the greater the withstand capacity of its surge current.

In addition, peak power consumption is also related to the pulse waveform, continuous time, and environmental temperature.

Also, the transient pulse that TVs can withstand is not repeated, and the component's pulse repeat frequency (the ratio of time to time and time to rest) is 0.01%.

If the circuit has a repeating pulse, it is possible to damage the TVs by considering the accumulated power of the pulse.

5. The volume of the electronic container C.

The volume C of the container is determined by the TVs avalanche, which is measured at a specific 1MHz frequency rate.

The size of C is proportional to the current capacity of the TVs tube, and C is too large to reduce the number of signals.

Therefore, C is an important reference for the use of TVs for the media. The higher the circuit of the electronic container to the higher the frequency of the digital/

The greater the interference of the two-pole tube on the circuit, the stronger the noise or attenuation signal, and therefore the need for the characteristics of the circuit to determine the cell range of the selected component.

High frequency circuits generally choose a small amount of battery (e.g. SAC (500w,50pf,±10%), LCE (1.5KW,100PF), low-battery TVs),

And the circuit of the electronic container is not high requirements of the choice can be higher than 40pF.

The difference between TVs diodes and Zener diodes