PRIORITY CLAIM

This application claims the priority benefit of French Application for Patent No. 1905816, filed on May 31, 2019, the content of which is hereby incorporated by reference in its entirety to the maximum extent allowable by law.

TECHNICAL FIELD

The present disclosure generally concerns electronic circuits and more particularly circuits configured to be coupled to an AC voltage source, such as the electric power distribution mains. The present disclosure more particularly applies to circuits comprising an AC capacitor.

BACKGROUND

In many applications, the power received from the electric power distribution network by devices connected thereto is filtered by an AC capacitor upstream of a voltage conversion and/or power factor correction circuit. The capacitor is generally directly connected to the line and neutral conductors (or between two phases) of the AC power supply.

The presence of the capacitor requires discharging it when the device is disconnected from the network. Indeed, the charge that it contains at the time when the device is disconnected should be discharged or dissipated for electric security reasons. This need is all the greater as the power is high.

Although many solutions exist for this problem, they are often complex and/or expensive.

There is a need in the art for a simple and inexpensive AC capacitor discharge circuit.

SUMMARY

An embodiment overcomes all or part of the disadvantages of AC capacitor discharge circuits.

In an embodiment, a circuit comprises two thyristors in anti-series and an AC capacitor having its two electrodes respectively coupled to two different electrodes of the thyristors. The circuit includes a control circuit configured to implement a process for operation wherein same gate currents are simultaneously applied to the two thyristors when the circuit detects that there is no AC voltage across the AC capacitor.

According to an embodiment, one of the thyristors conducts in the reverse direction in response to application of said gate currents.

According to an embodiment, said gate currents are applied to discharge the AC capacitor when said AC voltage stops being applied to the electrodes of the capacitor for a time period longer than a first threshold by at least one half period of the AC voltage.

According to an embodiment, said gate currents stop being applied if the circuit does not detect that an input voltage becomes smaller than a second threshold for a time period longer than a third threshold, said third threshold being greater than the first one.

According to an embodiment, said gate currents are applied for a time period longer than that of a half-period of the AC voltage configured to be applied to the two electrodes of the capacitor.

According to an embodiment, said gate currents are applied for a time period from a few tens of milliseconds to a few hundreds of milliseconds.

According to an embodiment, said gate currents are applied continuously.

According to an embodiment, said gate currents are applied in pulses.

According to an embodiment, said thyristors are controlled by a circuit which operates to detect the absence of a voltage between terminals of application of the AC voltage.

According to an embodiment, the thyristors form part of a bridge for rectifying the AC voltage.

According to an embodiment, in the presence of the AC voltage, the thyristors are controlled with pulses to rectify the AC voltage.

According to an embodiment, the thyristors receive a simultaneous control pulse for each halfwave of the AC voltage.

According to an embodiment, the thyristors each receive a control pulse one halfwave out of two of the AC voltage.

According to an embodiment, an output of the bridge powers a switched-mode power supply, said gate currents being generated under control of a circuit for controlling the switched-mode power supply.

According to an embodiment, the thyristors are cathode-gate thyristors.

According to an embodiment, the thyristors are anode gate thyristors.

