Patent ID: 6483379
Filing Date: 2002-11-19
Classification: H01H

Abstract:
Input circuit for monitoring alternating current signals, with an input resistance (Re) and a capacitor (C) connected in parallel on the input side, wherein an input current is delivered to the capacitor (C) based on an alternating current supply voltage (L1) to switched off devices (1; 2), characterized in that in addition a discharge circuit (23) is disposed parallel on the input side, wherein the discharge resistance (Rc) of the discharge circuit (23) is small relative to the input resistance (Re), wherein the discharge circuit (23) includes a switching element (S3), wherein the switching element (S3) is blocked while the sign of the momentary supply voltage (L1) and of the threshold voltage (Ustyp) to be recognized is the same, whereas in contrast the switching element (S3) is conducting while the sign of the momentary supply voltage (L1) and of the threshold voltage (Ustyp) to be recognized is opposite and wherein the discharge circuit (23) comprises a series connection of a rectifier (D) directed in the sign direction of the threshold voltage (Ustyp), the discharge resistor (Rc), and the switching element (S3).