| 摘要 |
PURPOSE:To adapt for the increased threshold value current effectively preventing elements from being deteriorated by a method wherein a DC protective circuit is added with an AC protective circuit to limit the peak value in AC component of a diode current. CONSTITUTION:A capacitor 14 and resistor 15 are parallel connected to the inverse parallel connected diodes 12, 13 and further parallel connected to a series circuit of another diode 1 and resistor 3. When DC current ID of an element 1 attains to specified value, a Zener diode 11 is exerted to be clamped on a current IL. Besides, the limiter diodes 12, 13 act upon the AC component of the element 1 and the resistor 3 in case of voltage fall limiting the absolute value of AC current ID to Vf/R3 in case its forward voltage fall value is Vf due to minor forward AC resistance of the limiter elements 12, 13. Because the frequency characteristics are almost determined by the time constant by the resistor 3 and the capacitor 14, these impedance value are selected to assure the specified characteristics. In such a constitution, any noise arising from a power supply may be limited preventing said diodes from being deteriorated. |
