Comparison of parameters between TVs tube and zener diode

TVS tube And Zener diode , What's the difference ！

Zener diode (Zener Diod Zener diode )

A. principle

It works in the state of voltage reverse breakdown , When the reverse voltage reaches and exceeds the stable voltage , The reverse current suddenly increases , The voltage across the diode is constant .

B. classification

From the high and low of voltage stabilization : Low voltage zener diode (<40V); High voltage zener diode (>200V)

From material points :N type ;P type

C. main parameter

① Steady voltage VZ: In the regulated regulator , Reverse working current IZ Next , Corresponding reverse working voltage ;

② Steady current IE;

③ Dynamic resistance rZ ;

④ Maximum dissipation power PZM;

⑤ Maximum stable working current IZmax And minimum stable working current IZmin;

⑥ temperature coefficient at, Higher temperature , The greater the voltage stabilization error .

D. purpose

① Clamp the drain and source

Silicon zener diode Zener circuit , It uses the reverse breakdown characteristic of the zener diode to stabilize the voltage , Because the reverse characteristic is steep , Large current changes , It will only cause small voltage changes .

Transient suppression diode is abbreviated as TVS

(Transient Voltage Suppressor)

1. characteristic

Under the specified reverse application conditions , When withstanding a high-energy instantaneous overvoltage pulse , Its working impedance can be immediately reduced to a very low conduction value , Allow large current to pass , And clamp the voltage to a predetermined level , So as to effectively protect the precision components in the electronic circuit from damage . Fast response speed ( by pS level ), Small volume , The clamping voltage is low , High reliability, bidirectional TVS Suitable for AC circuit , A one-way TVS Generally used in DC circuit .

2. classification

According to polarity, it can be divided into unipolar and bipolar .

3. Symbol : Symbol

4. Characteristic diagram of diode

5. Diode suppresses transient voltage 例 Figure and one-way protection figure

6.TVS Main parameters of

① VBR :Reverse Breakdown Voltage ( The reverse breakdown voltage is the breakdown voltage )

Definition : When TVS Flow through the specified 1mA electric current （ IR ） when , Geodesic TVS Voltage between two poles VBR yes TVS Minimum avalanche voltage .25℃ when , Before this voltage ,TVS Is not conductive , When the transient voltage exceeds VBR , The transient voltage suppression diode will collapse to suppress the transient voltage at a certain level , Provide an ultra-low resistance path for transient current , Let the transient current pass through the transient voltage The control diode is switched off , Avoid being insured Protective element .

② IR: Reverse Leakage Current ( Reverse leakage current )

When the maximum reverse operating voltage is applied to TVS Upper time ,TVS The tube has a leakage current IR, Generally, there are 10-100μA Reverse leakage current . When TVS When used in high impedance circuits , This leakage current is an important parameter .

③VRWM: Maximum reverse operating voltage (Reverse Stand-off Voltage: Bearable reverse voltage ) When the device works in reverse , According to the regulations IR Next , Voltage value at both ends of the device . At this time, the diode is in a non-conductive state , Usually VRWM=（0.8~0.9）VBR. When using , Should make VRWM Not lower than the normal working voltage of the protected device or line .

④ VC(max ): Maximum clamping voltage (TVS diode Clamping Voltage : Suppression voltage )

At pulse peak current Ipp Under action , The maximum voltage across the device is called the maximum clamping voltage . When using , Should make VC(max ) Not higher than the maximum allowable safety voltage of the protected device . The ratio of the maximum clamping voltage to the breakdown voltage is called the clamping factor . namely : Clamping coefficient =VC(max )/VBR The general clamping coefficient is 1.3 about .

⑤ Cj:TVS diodeJunction Capacitance ( Capacitance value of transient diode )

TVS The capacitance is determined by the area of the silicon chip and the bias voltage , The capacitance is zero biased , As the bias voltage increases , The capacitance value shows a downward trend . The capacitance will affect TVS Response time of the device . The larger the capacitance of the transient voltage suppression diode, the greater the interference to the circuit , The greater the noise or attenuation The stronger the signal , For data / The higher the frequency of the signal , The capacitance value shall not be greater than 10pF.

⑥ IPP: Maximum peak pulse current .

When working in reverse , Under the specified pulse conditions , The maximum pulse peak current allowed by the device .

⑦ PPR: Reverse pulse peak power .

TVS Of PPR Depending on the pulse peak current IPP And maximum clamping voltage VC, in addition to , And the pulse shape 、 The pulse time is related to the ambient temperature .

7. Transient suppression diode TVS The naming convention of

8. Method of detecting diode

With a multimeter R×1k Stop measuring the quality of the pipe ：

① For unipolar TVS, According to the method of measuring ordinary diodes , Its positive can be measured 、 Reverse resistance , Generally, the forward resistance is 4k5 about , The reverse resistance is infinite .

② For bi polar TVS, Exchange red at will 、 The resistance between the two pins measured by the black lead should be infinite , otherwise , State that the tube is malfunctioning or has been damaged .

9. TVS Typical examples in circuit applications

Examples of selection in DC :

DC working voltage of the whole machine 12V, Maximum allowable safe voltage 25V（ Peak value ）, Impedance of surge source 50MΩ, Its interference waveform is square wave ,TP=1MS, Maximum peak current 50A.

Examples of AC circuit applications ：

The DC line adopts unidirectional transient voltage suppression diode , AC must use bidirectional transient voltage suppression diode . AC is the grid voltage , The transient voltage generated here is random , Sometimes I encounter lightning （ Transient voltage generated by lightning induction ） Therefore, it is difficult to quantitatively estimate the instantaneous pulse power PPR. However, the maximum reverse working voltage must be selected correctly . The general principle is to multiply the AC voltage by 1.4 Times to choose TVS The maximum reverse working voltage of the tube . For DC voltage, press 1.1～1.2 Times to choose TVS The maximum reverse working voltage of the tube VRWM. The figure below shows a microcomputer power supply using TVS Schematic diagram of line protection .

1. In the incoming line 220VAC Add TVS Tube inhibition 220V Peak interference in AC network .

2. Add an interference filter to the incoming line of the transformer , Filter out small peak interference .

3. At the transformer output VAC=20V Add TVS tube , Suppress interference again .

4. To DC 10V Output with TVS Tubes suppress interference .

disclaimer ： This article is from the Internet , The copyright belongs to the original author , If involves the work copyright question , Please contact us in time , thank you ！ Reference to the original ：《TVS tube And Zener diode , What's the difference 》