An AC/DC converter, converting an alternating current voltage provided between a first phase and a second phase of an alternating current voltage source connected to the input of the AC/DC converter into a direct-current voltage applied to a load connected to the output of the AC/DC converter, said AC/DC converter comprising a switched-mode power supply connected at its output to the load and supplying a direct-current voltage thereto, the AC/DC converter further comprising a rectifier, down-converter, chopper stage connected upstream from the switched-mode power supply, said rectifier, down-converter, chopper stage being connected at its input to the alternating current voltage source and at its output to the input of the switched-mode power supply, said rectifier, down-converter, chopper stage providing the switched-mode power supply with a rectified, down-converted and chopped voltage with respect to the input alternating current voltage, the rectifier, down-converter, chopper stage comprising a first MOS transistor, thyristor or bipolar transistor-type switching element for chopping the input alternating current voltage provided by the input alternating current voltage source, a first diode connected to the first phase of the input alternating current voltage source for rectifying, by blocking the negative alternation, the input alternating current voltage provided by the input alternating current voltage source, a capacitor being connected between the output of the first switching element in the rectifier, down-converter, chopper stage and the second phase of the input alternating current voltage source to smooth the voltage at the output of the rectifier, down-converter, chopper stage, a second diode being connected between the output of the first switching element and the capacitor connected to the output of the first switching element, said second diode being conducting during a positive alternation of the voltage provided by the input alternating current voltage source and non-conducting during a negative alternation of the voltage provided by the input alternating current voltage source, characterised in that: - one or several resistances (Rdrain1, Rdrain2, Rdrain3, Rdrain4) are connected between the first diode and the input of the first switching element; and - a Zener diode is connected between the output of the first switching element and the base of a bipolar transistor whose collector is connected to the control terminal of the first switching element and whose emitter is connected to the second phase of the input alternating current voltage source, such that, when the voltage accross the capacitor connected to the output of the first switching element is higher than the Zener voltage of said Zener diode plus the base-emitter voltage of the bipolar transistor, the bipolar transistor is saturated and switches off the first switching element. - one or several resistances (Rdrain1, Rdrain2, Rdrain3, Rdrain4) are connected between the first diode and the input of the first switching element; and - a Zener diode is connected between the output of the first switching element and the base of a bipolar transistor whose collector is connected to the control terminal of the first switching element and whose emitter is connected to the second phase of the input alternating current voltage source, such that, when the voltage accross the capacitor connected to the output of the first switching element is higher than the Zener voltage of said Zener diode plus the base-emitter voltage of the bipolar transistor, the bipolar transistor is saturated and switches off the first switching element.