TVS (Transient Voltage Suppressor) diode is a component specially used for protecting circuits. It can absorb excessive voltage pulses in an instant to prevent the protected system from being damaged. This article will introduce the working principle, parameters, application, selection and precautions of TVS diodes in detail.
What is a TVS diode?
TVS diode is characterized by high response speed, low steady-state resistance, high peak power consumption and extremely low reverse leakage current. It can be started within nanoseconds, so that circuit equipment can be better protected in high voltage shock events.
TVS diode is a protective electronic component that can protect electrical equipment from voltage spikes introduced by wires. There are unidirectional and bidirectional ones.
Unidirectional: TVS diode is similar to a rectifier when operating in the forward direction, but its design allows it to withstand a large peak current. The instantaneous power of the 1.5KE series can reach 1500 w.
Bidirectional: TVS diode can be regarded as two avalanche diodes with opposite polarity connected in series, and then connected in parallel with the circuit to be protected. Although it is marked as two diodes in the circuit, the actual component is to encapsulate two diodes in the same package.
TVS diode is an effective circuit protection device commonly used in the market. Its appearance is the same as that of ordinary diodes. It is divided into two categories: axial type and patch. Its main function: it can absorb surge power up to several kilowatts. Its main feature is that under reverse application conditions, when subjected to a high-energy large pulse, its working impedance immediately drops to a lower conduction value, thereby allowing large current to pass through, while keeping the voltage foil at a predetermined level, and its response time is only 10-12 milliseconds. Therefore, it can effectively protect the precision components in electronic circuits. Then the bidirectional TVS can absorb instantaneous large pulse power in both positive and negative directions, and keep the voltage foil at a predetermined level. Bidirectional TVS is suitable for AC circuits, and unidirectional TVS is generally used for DC circuits. It can be used for lightning protection, overvoltage protection, anti-interference, surge power absorption, etc. It is an ideal protection device.
Parameters
The main parameters of TVS diodes include maximum reverse working voltage, maximum peak discharge current, maximum reverse surge current, etc.
The maximum reverse working voltage refers to the maximum reverse voltage that the TVS diode can withstand. If this voltage is exceeded, the TVS diode will lose its protection ability. The maximum peak discharge current refers to the maximum current that the TVS diode can absorb when it is hit by a voltage pulse.
The maximum reverse surge current refers to the maximum reverse surge current that the TVS diode can withstand after being hit by a voltage pulse.
Working principle of TVS diode
The working principle of TVS diode is based on the Zener effect, that is, when the voltage on both sides of the PN junction exceeds a certain critical value, the PN junction will break down and conduct instantly. The TVS diode is a specially designed Zener diode that can withstand higher current and power, giving it better protection in transient high-voltage events. The working principle of the TVS diode is based on the unidirectional conductive properties similar to normal diodes. But the difference is that when the external voltage exceeds a certain range, the TVS diode will quickly become a low-impedance state, absorb the voltage overload pulse, and prevent these pulses from entering the protected circuit, thereby protecting the circuit system from voltage peaks.
Specifically, when the voltage of the input circuit exceeds the operating voltage range of the TVS diode, the TVS diode will start immediately and direct the excess charge to the ground or other low-impedance paths, thereby preventing the circuit equipment from being damaged by overvoltage.
Application of TVS diodes
Due to the advantages of fast response speed, strong fragility and good limiting voltage stability of TVS diodes, it is widely used in transient protection and ESD protection of various electronic circuits. The following are several common application scenarios:
Power supply protection: TVS diodes can be used to protect the power input end from overshoot and overvoltage damage of the power line voltage.
Communication interface protection: TVS diodes can be used to protect devices of communication interfaces such as serial ports, network ports, USB ports, etc. from damage caused by sudden voltage events such as lightning and ESD.
Automotive electronics: TVS diodes can be used in automotive electronics to resist overvoltage events in analog circuits and digital circuits, protect automotive electrical equipment from overvoltage, surge and ESD, and prevent equipment failure caused by voltage disturbances caused by car starting, flameout, sudden braking, etc.
Electronic devices: TVS diodes are widely used in various electronic devices, such as computers, mobile phones, digital cameras, etc. to protect key circuits from transient voltages.
Industrial automation: TVS diodes are also needed in industrial automation systems to protect the stable operation of key controllers such as PLCs and DCSs.
Selection and considerations of TVS diodes
When selecting TVS diodes, the following factors need to be considered:
Peak power dissipation capability: Select a TVS diode with sufficient peak power dissipation capability based on the magnitude and duration of the transient peak voltage.
Operating voltage: The operating voltage of the TVS diode must be greater than the maximum voltage of the protected system.
Extreme withstand power: Select an appropriate TVS diode based on the power requirements of the protected system.
Response time: The TVS diode must be able to respond quickly to overvoltage in the protected system to prevent damage.
Maximum pulse current: The maximum pulse current of the TVS diode must be greater than or equal to the maximum pulse current of the protected system.
Operating temperature range: When selecting a TVS diode, ensure that it can operate normally within the operating temperature range of the protected system.
