Method of operating an electronic converter, corresponding control circuit and electronic converter

A control circuit for controlling a switching activity of a switching stage including an inductance of an electronic converter having input terminals configured to be coupled to an energy source to receive an AC input signal therefrom and output terminals configured to be coupled to a user circuit to provide a DC output signal thereto, said switching stage switchable between an active state and an inactive state based on a status signal, said control circuit comprising:

• a first input node configured to be coupled to the input terminals of the electronic converter to sense therefrom an input sensing signal indicative of said AC input signal;
• a second input node configured to be coupled to an auxiliary power supply source to receive an auxiliary power supply signal therefrom;
• a first output node configured to be coupled to said switching stage of the electronic converter to control said switching activity thereof;
• and
• processing circuitry configured to:
• operate said electronic converter in a mode selected from a first mode and a second mode, wherein:
• a. in case the electronic converter is in the first mode and said status signal is asserted to set said switching stage to said active state, the processing circuitry is configured to:
• provide a first reference threshold value and a first time value;
• and
• de-assert said status signal in response to an amplitude of said input sensing signal failing to reach said first reference threshold value for a time length equal to said first time value, and
• b. in case the electronic converter is in the second mode and said status signal is de-asserted to set said switching stage to said inactive state, the processing circuitry is configured to:
• periodically vary the auxiliary power supply signal with a variation period such that the auxiliary power supply signal alternates between a negative slope from an upper value to a lower value and a positive slope from the lower value to the upper value in the variation period;
• provide a second reference threshold value and a second time value;
• assert, after lapse of a time interval equal to said variation period, a comparison signal in response to the amplitude of said input sensing signal reaching said second reference threshold value;
• perform a first check that said comparison signal is asserted for a time length equal to said second time value;
• perform a second check that said periodically varying auxiliary power supply signal is varying with the negative slope at the time said comparison signal is asserted;
• and
• based on a positive result of said first check and said second check, discontinue periodically varying said auxiliary power supply signal and asserting said status signal.

An electronic converter, comprising:

• a switching stage having an inductance;
• input terminals coupled to an energy source and configured to receive an AC input signal therefrom;
• output terminals configured to be coupled to a user circuit to provide a DC output signal thereto, a switching activity of said switching stage being in an active state or an inactive state based on a status signal;
• and
• a control circuit configured to control the switching activity of the switching stage, the control circuit including:
• a first input node configured to be coupled to the input terminals of the electronic converter to sense therefrom an input sensing signal indicative of said AC input signal;
• a second input node configured to be coupled to an auxiliary power supply source to receive an auxiliary power supply signal therefrom;
• a first output node configured to be coupled to said switching stage of the electronic converter to control said switching activity thereof;
• and
• processing circuitry configured to:
• operate said electronic converter in a mode selected from a first mode and a second mode, wherein:
• a. in case the electronic converter is in the first mode and said status signal is asserted to set said switching stage to said active state, the processing circuitry is configured to:
• provide a first reference threshold value and a first time value;
• and
• de-assert said status signal in response to an amplitude of said input sensing signal failing to reach said first reference threshold value for a time length equal to said first time value, and
• b. in case the electronic converter is in the second mode and said status signal is initially de-asserted to set said switching stage to said inactive state, the processing circuitry is configured to:
• periodically vary the auxiliary power supply signal with a variation period such that the auxiliary power supply signal alternates between a negative slope from an upper value to a lower value and a positive slope from the lower value to the upper value in the variation period;
• provide a second reference threshold value and a second time value;
• assert, after lapse of a time interval equal to said variation period, a comparison signal in response to the amplitude of said input sensing signal reaching said second reference threshold value;
• perform a first check that said comparison signal is asserted for a time length equal to said second time value;
• perform a second check that said periodically varying auxiliary power supply signal is varying with the negative slope at the time said comparison signal is asserted;
• and
• based on a positive result of said first check and said second check, discontinue periodically varying said auxiliary power supply signal and asserting said status signal.