news

It is well known that electronic products often encounter unexpected voltage transients and surges in use, which lead to damage of electronic products. The damage is caused by the semiconductor devices in electronic products (including diodes, transistors, SCR and integrated circuits) being burned or broken down.

1, one of the methods is to make the whole machine, and grounding system, the whole machine and the system of (public) and the earth shall be separated, the whole machine and the system of each subsystem shall have independent public side, between the subsystems to transfer data or signal, should to the earth as the reference level, ground wire (surface), it must be a large current, such as several hundred amperes.

2. The second protection method is to adopt voltage transients and surge protection devices in the key parts of the whole machine and system (such as computer display, etc.), so that the voltage transients and surge can be bypassed to the subsystem ground and earth through the protection devices, so that the transient voltage and surge amplitude entering the whole machine and system can be greatly reduced.

3. The third protection method is to use a combination of several voltage transients and surge protection devices to form a multistage protection circuit for important and expensive machines and systems.

Surge protector provides a simple, economical and reliable protection method for the power surge protection of electronic equipment. By means of surge protector (MOV), the surge energy can be quickly transmitted to the earth in case of lightning strike induction and operating overvoltage, so as to protect the equipment from damage.

(4) to strengthen the protection effect of electronic equipment, in the power supply and load between a series of super isolation transformer (also known as isolation method), in order to isolate the high-frequency peak interference, but also can make the secondary equipotential connection easy to carry out.

Isolation method mainly uses the isolation transformer with shielding layer.Because common-mode interference is a kind of relatively terrestrial interference, it is transmitted mainly through the coupling capacitance between transformer windings.If a shielding layer is inserted between the primary and secondary, and the shielding layer is well grounded, the interfering voltage can be shunned through the shielding layer, thus reducing the interfering voltage at the output.

Theoretically, the transformer with shielding layer can make the attenuation of about 60dB.But the isolation effect is good or bad, often depends on the shielding layer technology.It is best to choose 0.2mm thick copper plate, the original side, the deputy side each add a shielding layer.Usually, the primary shielding is connected to the secondary shielding through a capacitor, which is then connected to the ground of the secondary.The shielding layer of the primary edge may also be connected to the ground of the primary edge, and the shielding layer of the secondary edge may be connected to the ground of the edge.And the cross-sectional area of the grounding lead should also be larger.The isolation transformer with a shielding layer is a good method, but the volume is larger.

This method because the transformer function is too single, relative volume, weight, installation is not very convenient, in the middle and low frequency peak and surge protection effect is not good, so the market is limited, manufacturers are not much.So it’s not usually used on special occasions.

(5) absorption method

Absorbing method mainly uses wave absorbing device to absorb the interference voltage of surge peak.Absorbing devices all have a common characteristic, that is, they present high impedance below the threshold voltage, and once the threshold voltage is exceeded, the impedance drops sharply, so they have a certain inhibitory effect on the peak voltage.

This kind of absorbing device mainly includes varistor, gas discharge tube, TVS tube, solid discharge tube, etc.Different absorbing devices also have their own limitations in the suppression of peak voltage.If the current absorption capacity of the varistor is not large enough, the response speed of the gas amplifier tube is slow.