Patent ID: 6268990
Filing Date: 2001-07-31
Classification: H03K

Abstract:
A semiconductor protection device for suppressing an application voltage containing a surge voltage to a preset value or less, the surge voltage occurring at a turn-OFF phase of a main semiconductor switch having first and second main electrodes and a control electrode, said protection device comprising:a switching element configured to form a bypass which is connected in parallel with said main semiconductor switch and opened/closed depending on said preset value, said switching element having first and second terminals arranged to be respectively connected to said first and second main electrodes and a control terminal configured to control conduction of a path between said first and second terminals; anda voltage setting element connected to said control terminal and configured to set said preset value,wherein said voltage setting element sets said preset value to 100% to 150% of a circuit voltage applied between said first and second main electrodes, and applies a voltage caused by energy of the application voltage to said control terminal when the application voltage exceeds said preset value, to make said path between said first and second terminals conductive so as to open said bypass parallel with said main semiconductor switch, andwherein said voltage setting element includes an electric field sensing element connected between said first main electrode and said control terminal, said electric field sensing element including a first semiconductor region, an input electrode connected to said first semiconductor region and said first main electrode, and an output electrode disposed on said first semiconductor region through an insulating film and connected to said control terminal, such that said first semiconductor region is depleted by use of an electric field generated by the application voltage and applied through said input electrode, and thus said output electrode forms a capacitive coupling with said input electrode to apply a voltage caused by energy of the application voltage to said control terminal, when the application voltage exceeds said preset value.