| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve a size reduction and a cost reduction by lowering a withstand voltage of an element. <P>SOLUTION: When a state that a current flows in a path to clamp diodes Du4 to Du3 to Du2 as shown by a dotted line in Fig.1(b) is changed to a state in Fig.1(c), the path between Du2 to Du4 is reversely restored at a voltage of Ed (P1). Since the diodes Du2, Du3 and Du4 are connected in series, a voltage of Ed(P1)/3 is applied to each diode, and a surge voltage ΔVsp generated at the reverse restoration is lowered to 1/3, too. After that, the voltage is changed to Ed(P1+N1) in Fig.1 (d) from Fig.1(c), and in Fig.1 (e) from Fig.1(d), the voltage is changed to Ed(P1+N1+N2), but the diodes do not perform reverse restoration operations since they have been already turned off eve in the states are changed, and the surge voltage is not generated. Therefore, an element withstand voltage having an allowance by an mount of the surge voltage generated at the reverse restoration is not necessary for the Du2, Du3 and Du4, and the withstand voltage of the element can be made lower than that of the other element, thus achieving the size reduction and the cost reduction. <P>COPYRIGHT: (C)2007,JPO&INPIT |
