The circuit protection scheme are engineers according to the protection grade products and working voltage, current and power values of actual design, selection of protection scheme is effective in design and an important factor - electronic protection device. What engineers how to buy ceramic discharge tube? The circuit protection experts on lightning protection devices tage electronic ceramic discharge tube as an example, to explain in detail the principles of purchasing ceramic discharge tube. Ceramic discharge selection principle:
(1) in the rapid pulse, GDT gas ionization requires a certain amount of time (usually 0.2 ~ 0.3 s, the fastest also has about 0.1 s), which has a higher amplitude spike will leak to the back. To curb the sharp pulse, there are several ways: A, in the discharge tube or shunt capacitor varistor; transmission line B, in the discharge tube after the series inductance or stay length is appropriate, the sharp pulse attenuation to the lower level; C, using two levels of protection circuit to discharge tube as the first stage in TVS tube or semiconductor discharge tube as second grade, two grade with resistance, inductance or self recovery fuse isolation.
(2) the selection of the DC breakdown voltage Vsdc: the minimum value of the DC breakdown voltage Vsdc should be greater than 1.2 times the maximum power peak voltage or the maximum signal voltage.
(3) the choice of impulse discharge current: to select the maximum surge current that may appear on the line or to protect the maximum surge current. Discharge tube impulse discharge current should be calculated according to the nominal impulse discharge current (or half of the single impulse discharge current).
(4) ceramic gas discharge tube for breakdown voltage error is large, generally do not make use of parallel.
(5) the continued flow problem: in order to make the normal arc discharge in shock after the breakdown in the possible freewheeling place (such as active circuit), in the discharge tube series varistor or self recover fuse limit continued flow, make it less than the holding current discharge tube.
(6) DC discharge voltage: never affected by protection of the normal operation of the system requirements, to DC discharge voltage discharge was higher. But the high voltage of the DC discharge tube, the impact of the discharge voltage is high; from the protection of electronic equipment tolerance, the hope that the DC discharge voltage of the tube is low.
Therefore, the discharge voltage of the discharge tube of the ceramic discharge tube should be made a compromise between these two kinds of mutual constraints.