IEEE C62.37.1-2012 pdf download IEEE Guide for the Application of Thyristor Surge Protective Device Components
2.Normative references
The following referenced documents are indispensable for the application of this document (i., thcy mustbe understood and used, so each referenced document is cited in text and its relationship to this document isexplained). For dated references, nly the edition cited applies. For undated references, the latest edition ofthe referenced document (including any amendments or corrigenda) applies.
IEEE Std C62.37TM.996 (Reaff 2010), IEEE Standard Test Specification for Thyristor Diode SurgeProtective Devices.2. 3
3. Definitions
For the purposes of this document, the terms and definitions given lEEE Std C62.37-1996 and thefollowing apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in thisclause.
anti-parallel (connection): A parallel combination of two semiconductor elements, where the main currententry electrode of one element connects to the main current exit electrode of the other element, allowingone element to pass current in one voltage polarity and the other element to pass current in the oppositevoltage polarity.Syn: inverse-parallel connection.
4.Basic function and component description
This clause covers the basic device structure, its equivalent circuit, characteristic values, operationalparameters,and structures with increased functions.
4.1 Basic device structure
Thyristor overvoltage protectors are manufactured by creating a scries of N-type and P-type layers in asilicon chip. The basic thyristor structure has three PN junctions, which requires four layers (NPNP).Asone layer can be the starting silicon (N- or P-Type), further layers need to be constructed to obtain therequired four layers.
Figure 1 shows the simplified structure of a unidirectional thyristor SPC. The switching quadrant (seeFigure 3) occurs when the bottom contact is positive with respect to the top contact. Also shown are thelumped equivalent circuit elements created by the semiconductor layers. This example started manufacturewith an N slice of silicon. Layers of P material are then created at the top and bottom. A further N* regionis then made on the top surface. Finally the top and bottom metallization are added to provide contacts. Theupper right section of the contact metal is not shown in order to illustrate the detail of the topside siliconsurface.
4.2 Device equivalent circuit In Figure 1, transistor TRI is formed by the NPN layers. Similarly transistor TR2 is formed by the PN P layers. The device breakdown voltage is determined by the breakdown of the central N P layers, which form a shared collctor-base junction for transistors TRI and TR2. For clarity, the breakdown function is shown as breakdown diode D1. Resistance R1 is the lateral resistance of the P layer. Resistor R2 together with resistor RI shunt the base-emitter junction of transistor TR1 to define the value of holding current, Resistor R2 has a relatively low value of resistance and is considered as a localized short circuit between base and emitter. During the manufacturing process, the emitter N+ diffusion is perforated with a series of dots to create these short circuits. In Figure 1 some of the top metallization has been omitted to show the P- type shorting dots.