Semiconductor arrester

Abstract: To enable the mounting of a diode-bridge thyristor type arrester in a small sized package of resin sealed type for general use, such as a TO-92 package or a TO-220 package, the arrangement of the diodes (D1 - D6) and the thyristor (T1) is modified. The arrester comprises a pair of opposed metal plates (20, 21); a thyristor (T1) located between the metal plates (20, 21); three pairs of diodes (D1, D2; D3, D4; D5, D6) located between the metal plates (20, 21); and three leads (22, 23, 24), each interposed between its respective pair of diodes.

Description: The present invention relates to a semiconductor arrester which is a safety device for protecting a communication instrument or the like from an abnormally high voltage caused by lightning, contact with a power cable, or short-circuit or failure in the communication instrument. Particularly, it relates to a semiconductor arrester of diode-bridge thyristor type. Fig. 9 shows the circuitry of a semiconductor arrester of diode-bridge thyristor type as disclosed in US-A-5,175,662, (hereinafter referred to as "a semiconductor arrester"), having three terminals (T; tip, E; earth, R; ring), six diodes (D1 to D6) and one reverse-blocking diode thyristor (T1), wherein an anode of D1 and a cathode of D2 are connected with terminal T (or terminal R); an anode of D5 and a cathode of D6 are connected with terminal E; cathodes of D1, D3 and D5 are connected with an anode of T1 and anodes of D2, D4 and D6 are connected with a cathode of T1. In such a circuit structure, if it is assumed that an abnormally high voltage of positive polarity is applied, for example, to terminal T, then D1, T1 and D5 are sequentially biased in the forward direction and T1 is turned on to connect terminal T to terminal E via a low resistance. Accordingly, the abnormally high voltage can be released to terminal E (earth) so that the communication instrument connected to terminal T is protected. Fig. 10 shows a package structure for the conventional semiconductor arrester also disclosed in US-A-5,175,662, seen from the above when a cap is removed, wherein the first to the sixth metallic members 11 through 16 are mounted on an insulating base plate 10. The first, second, fifth and the sixth metallic members 11, 12, 15 and 16 all penetrate the insulation base plate 10 from the front side to the back side thereof. The first metallic member 11 exposed on the back side of the insulation base plate 10 is used as terminal T (or terminal R), and the second metallic member 12 on the back side is as terminal R (or terminal T). Also, the fifth metallic member 15 and the sixth metallic member 16 on the back side are both used as terminal E or one of them is as terminal E while being connected with the other. The first metallic member 11 on the front side of the insulation base plate 10 is used as anode contact of D1 and cathode contact of D2; the second metallic member 12 on the front side is as anode contact of D3 and cathode contact of D4; the fifth metallic member 15 on the front side is as cathode contact of D6; and the sixth metallic member 16 on the front side is as anode contact of D5 Further, the third metallic member 13 is used as anode contacts of D2, D4 and D6 as well as cathode contact of T1; and the fourth metallic member 14 is as cathode contacts of D1, D3 and D5 as well as anode contact of T1. In the conventional package structure of semiconductor arrester described above, since the elements were actually arranged in the circuitry as they are illustrated in Fig. 9, there is a problem in that, for example, D6, T1 and D5, are located in one row to require a longer space, and the thyristor and the diodes are not base chips, but are thickly covered, whereby they can be installed only in a relatively large package. The primary object of the present invention is to provide a semiconductor arrester capable of being installed in a small-sized package of a resin-sealed type for general use, such as a TO-92 package or a TO-220 package, wherein the arrangement of diodes and thyristor are designed to be compact. According to this invention a diode bridge thyristor type semiconductor arrester, comprising: a pair of opposed metallic plates, three terminals, six diodes and a thyristor, wherein: the anode of a first diode and the cathode of a second diode are connected with a first terminal; the anode of a third diode and the cathode of a fourth diode are connected with a second terminal; the anode of a fifth diode and the cathode of a sixth diode are connected with a third terminal; cathodes of the first, third and fifth diodes are connected with the anode of the thyristor and one of said metallic plates; and anodes of the second, fourth and sixth diodes are connected with the cathode of the thyristor and the other one of said metallic plates, and wherein: the thyristor is located between the metallic plates; the first and second diodes are arranged as a pair and located between the metallic plates, with the first terminal located between the first and second diodes; and the third and fourth diodes are arranged as a pair and located between the metallic plates, with the second terminal located between the third and fourth diodes; is characterised in that the fifth and sixth diodes are arranged as a pair and located between the metal plates, with the third terminal located between the fifth and sixth diodes and the terminals comprise leads. With this arrangement, the thyristor is solely sandwiched between the metal plates. Therefore, the thyristor and the two diodes are not arranged end to end in a row as is the conventional case. Thus, the package size can be reduced by at least an extent corresponding to the thickness of the thyristor, whereby the inventive arrester is capable of being accommodated in a small sized package of a resin sealed type for the general use such as a TO-92 package or a TO-220 package. Preferred embodiments of arresters in accordance with this invention will now be described with reference to the attached drawings, in which:- Fig. 1 is a front view of one embodiment of a semiconductor arrester according to the present invention; Fig. 2 is a side view of the semiconductor arrester shown in Fig. 1; Fig. 3 is a bottom view of the semiconductor arrester; Fig. 4 is a front view of one type of compact package according to the present invention; Fig. 5 is a front view of another type of compact package; Fig. 6 is a front view of one modification of the plates; Fig. 7 is a front view of another modification of the plates; Fig. 8 is a front view of yet another modification of the plates; Fig. 9 is the circuitry of a semiconductor arrester of diode-bridge thyristor type; and Fig. 10 is the top view of a conventional structure. Each of a first metallic plate 20 and a second metallic plate 21 is equally formed into generally T-shape and has three ends and one cross-point, on which are provided, respectively, contacts 20a to 20d in the case of the first metallic plate 20 or contacts 21a to 21d in the case of the second metallic plate 21. The first and second metallic plates 20, 21 are located so that the contacts of the one plate are opposite to those of the other plate. Between the pair of contacts 20a and 21a is fixedly sandwiched a reverse-blocking diode thyristor T1 (see Fig. 9) by soldering. Also, between the remaining three pairs of contacts 20b, 21b; 20c, 21c; and 20d, 21d are intervened a first lead 22 (terminal T or R), a second lead 23 (terminal E) and third lead 24 (terminal R or T), respectively, in a non-contacting state. Between the leads 22, 23, 24 and the contacts 20b, 21b, 20c, 21c, 20d, 21d, except for the pair of contacts 20a, 21a, are fixedly sandwiched diodes D1 through D6 (see Fig. 9), respectively, by soldering. Concretely, D1 is sandwiched between one side of the first lead 22 and the contact 20b; D2 is between the other side of the first lead 22 and the contact 21b; D6 is between one side of the second lead 23 and the contact 20c; D5 is between the other side of the second lead 23 and the contact 21c; D3 is between one side of the third lead 24 and the contact 20d; and D4 is between the other side of the third lead 24 and the contact 21d, respectively. Polarities of T1, D1 through D6 are listed in the following table: Element Partner of Anode Partner of Cathode T1 contact 20a contact 21a D1 first lead 22 contact 20b D2 contact 21b first lead 22 D3 third lead 24 contact 20d D4 contact 21d third lead 24 D5 second lead 23 contact 20c D6 contact 21c second lead 23 According to such a structure, it is possible to arrange D1, T1 and D6 (or D5, T1 and D2) between the first lead 22 (terminal T or R) and the second lead 23 (terminal E) and to arrange D3, T1 and D6 (or D5, T1 and D4) between the third lead 24 (terminal R or T) and the second lead 23 (terminal E), in the forward direction, whereby the circuit shown in Fig. 9 is obtainable. Moveover, since T1 is solely sandwiched between the first metallic plate 20 and the second metallic plate 21 in this embodiment, it is possible to shorten the distance between the plates 20 and 21 by at least an extent corresponding to the thickness of T1, compared with the conventional device described at the beginning of this specification. Accordingly, a total size of the arrester can be reduced to reduce the package contour (shown by the dotted line A), whereby the arrester can be mounted in a small-sized package for general use, such as the T0-92 package shown in Fig. 4 or the T0-220 package shown in Fig. 5. In this connection, T0-92 and T0-220 packages are defined by JEDEC (Joint Electron Devices Engineering Council) standard, and are mainly used for sealing power source regulator IC or the like. In either cases, three leads 31 through 33 extend outside from a body molded (sealed) by a sealing resin 30 such as plastic. These leads 31 through 33 correspond to the parts of the first lead 22, the second lead 23 and the third lead 24 shown in Figs. 1 - 3 (that is, the terminal portions to be connected with outside) except for the end portions thereof to be connected with diodes D1 through D6. The difference between a T0-220 type package and a T0-92 type package is that the former is provided with a mounting 34 which can also be used as a heat sink. In the above embodiment, while the first and second metallic plates are formed into a T-shape, the present invention is not limited thereto. For example, the metallic plate may be of a Y-shape (directed downward) as shown in Fig. 6, an arrow shape as shown in Fig. 7, or a modified T-shape as shown in Fig. 8. In short, any shape may be used if three ends T 1 , T 2 and T 3 and one cross-point K 1 are provided. Since a thyristor is sandwiched between only the first and the second metallic plates in the present invention, it is possible to minimize the package size by at least an extent corresponding to the thickness of thyristor, as compared to a conventional package, whereby the arrester can be mounted in a small-sized package of a resin-sealed type for general use such as a T0-92 package or a T0-220 package.

Claims: A diode bridge thyristor type of semiconductor arrester, comprising a pair of opposed metallic plates (20,21), three terminals (T,E,R), six diodes (D1 to D6) and a thyristor (T1), wherein: the anode of a first diode (D1) and the cathode of a second diode (D2) are connected with a first terminal (T or R); the anode of a third diode (D3) and the cathode of a fourth diode (D4) are connected with a second terminal (R or T); the anode of a fifth diode (D5) and the cathode of a sixth diode (D6) are connected with a third terminal (E); cathodes of the first, third and fifth diodes (D1, D3 and D5) are connected with the anode of the thyristor (T1) and one of said metallic plates (20 or 21); and anodes of the second, fourth and sixth diodes (D2,D4 and D6) are connected with the cathode of the thyristor (T1) and the other one of said metallic plates (21 or 20), and wherein: the thyristor (T1) is located between the metallic plates (20,21); the first and second diodes (D1,D2) are arranged as a pair and located between the metallic plates (20,21), with the first terminal (T or R) located between the first and second diodes (D1,D2); and the third and fourth diodes (D3,D4) are arranged as a pair and located between the metallic plates (20,21), with the second terminal (R or T) located between the third and fourth diodes (D3,D4); characterised in that the fifth and sixth diodes (D5,D6) are arranged as a pair and located between the metal plates (20,21), with the third terminal (E) located between the fifth and sixth diodes (D5,D6) and the terminals (R,T,E) comprise leads (22,23,24). A semiconductor arrester according to claim 1, wherein each diode (D1 - D6) is naked and is directly connected between its associated plate (20,21) and lead (23,24,25). A semiconductor arrester according to claim 1 or 2, wherein the thyristor (T1) is naked and is directly connected between the metal plates (20,21). A semiconductor arrester according to any one of the preceding claims, wherein there is provided a resin layer filling the space between the plates (20,21). A semiconductor arrester according to any one of the preceding claims, wherein the plates (20,21) are entirely embedded within a moulded resin body (A). A semiconductor arrester according to any one of the preceding claims, wherein the plates (20,21) are formed, into a T-shape, a Y-shape or an arrow shape.

Inventors: HAMADA ITSUNARI, KIM MIN-SU, HAMADA, ITSUNARI, KIM, MIN-SU, HAMADA, ITSUNARI, C/O SHINKO ELECTRIC IND. CO. LTD
Applicants: SHINKO ELECTRIC IND CO, SHINKO ELECTRIC INDUSTRIES CO. LTD.
Application year: 1995
Main classification: H02H9
IPC codes: H01B17, H02H9, H01C8