| 摘要 |
PURPOSE: To prevent overvoltages by permitting the first current path of an electronic circuit to contain a first diode, permitting a current to flow, when trunk voltage is negative, permitting a second current path to contain a second diode and a thyristor, turning on the thyristor by means of a delay time, when it is charged by positive voltage. CONSTITUTION: Pins I/01, 02... are the starting points of a current path 1 and are connected to an electronic circuit 5 and include a grounded diode VIN of an anode is contained and current flows, when trunk voltage VAC is negative. The anode of the second diode VIP is connected to the current path 1 and current flows from a pin 3 to a circuit 4 through a current path 2. The circuit 4 is shared by all input/output circuits. Current flows to parallel capacitors C1 and C2, and the thyristor T1 is connected to C1 in parallel. Voltage obtained by dividing a voltage +Vs by a Zener diode Z1 and a resistance R1 is applied to the gate through a resistance R2. The capacitor C1 and the thyristor T form a time delay circuit, and the turning on of T is delayed, thus, preventing overvoltage. |
