diodes Calculation and Selection (01)

TVS diodes Calculation and Selection (01)

When it comes to TVS, it is well-known that it is used for port protection to prevent damage to subsequent circuits caused by transient voltage surges at the port. Because of its extremely important position in the circuit, however, many manufacturers directly recommend the circuit for TVS selection process, telling the designer which device to choose, but rarely provide theoretical calculation for the selection process. Most electronic engineers rely on experience and new people rely on reference when selecting TVS diodes. Once the manufacturer or test conditions are changed, there is no way to start, This article specifically addresses this issue, enabling both new and elderly people to be proficient in TVS selection.

operational principle

Transient Voltage Suppressors, also known as avalanche breakdown diodes. It is a device made using semiconductor technology to integrate a single PN junction or multiple PN junctions. TVS diodes can be divided into unidirectional and bidirectional, with unidirectional TVS diodes generally applied to DC power supply circuits and bidirectional TVS applied to circuits with alternating voltage. As shown in Figure 1, when applied to a DC circuit, one-way TVS is in reverse parallel to the circuit. When the circuit works normally, TVS is in the cut-off state (High impedance), which does not affect the normal operation of the circuit. When an abnormal over-voltage occurs in the circuit and reaches the TVS (avalanche) breakdown voltage, the TVS rapidly changes from a high resistance state to a low resistance state, discharges the instantaneous over-current caused by the abnormal over-voltage to the ground, and clamps the abnormal over-voltage to a lower level, thus protecting the rear circuit from damage caused by the abnormal over-voltage. When the abnormal overvoltage disappears, the TVS diodes resistance returns to the