Detection circuit for an active discharge circuit of an X-capacitor, associated active discharge circuit, integrated circuit and detection method

摘要

A detection circuit (40) for an active discharge circuit is provided. Such active discharge circuits are often used to discharge an X-capacitor (304). For this purpose, the detection circuit (40) generates a discharge enable signal (EN) which signals the presence or absence of AC oscillation applied to the X-capacitor (304). More specifically, the detection circuit (40) includes a sensor circuit (402; 404) for connection to the X-capacitor (304), wherein the sensor circuit (402; 404) generates a sensor signal (S) indicative of the voltage across the X-capacitor (304). Furthermore, the detection circuit (40) has a processing unit (406) which has a comparator circuit, a timer circuit, an evaluation circuit and a dynamic threshold generator circuit. More specifically, the comparator circuit generates at least one comparison signal by comparing the sensor signal (S) with at least one threshold value. The timer circuit provides the discharge enable signal (EN) at a first logic level when the timer circuit has been reset via a reset signal. Next, the timer circuit determines the elapsed time since the last reset and checks if the elapsed time exceeds a certain timeout value. If the elapsed time exceeds the predetermined timeout value, the timer circuit presets the discharge enable signal (EN) at a second logic level. The evaluation circuit generates the reset signal for the timer circuit as a function of the at least one comparison signal. Finally, the dynamic threshold generator circuit varies the at least one threshold of the comparator circuit as a function of the sensor signal (S).