DK0545926T3 - Current Monitoring Circuit - Google Patents

Abstract

A circuit relay circuit to switch off the power supply to electrical equipment by operating a power switch, especially to disconnect the transformer of a low-voltage halogen lamp cable system from the mains if the current consumed by the electrical equipment to be monitored is outside a permissible current range, in order to improve operational safety, especially with respect to fire hazards, comprises, according to the invention, a first capacitor (29) which can be charged via a first control circuit (30) to a first capacitor voltage dependent upon the peak of the current to be monitored, a switch-on signal generating circuit (31) to generate a switch-on signal for a set period after the mains power to the electrical equipment (4) has been switched on, a second capacitor (32), a second control circuit (33) which responds to the switch-on signal and charges the second capacitor (32) to a second capacitor voltage dependent upon the first capacitor voltage when the switch-on signal is present, a third control circuit (35) to regulate the charge of the second capacitor (32), which is connected to the first (29) and second (32) capacitors and responds to the first and second capacitor voltage in such a way that it discharges the second capacitor (32) if the second capacitor voltage exceeds the first by more than a preset voltage difference, and that it charges the second capacitor (32) with a high time constant in the other case, and a first comparator circuit (34) which is connected on the input side to the first and second capacitors (29, 32) and on the output side is in operative connection with the power switch (41, S) and breaks the power switch (41, S) if the first capacitor voltage exceeds a value dependent upon the second capacitor voltage.