Converter device and uninterruptible power supply equipped with such a device

1. A converter device for enabling an AC voltage and current to be supplied by filtering pulses on a modulated signal output from three substantially DC voltages available, respectively, on a reference voltage line, and on two DC voltage inputs of opposite signs from two switching units, said device comprising:

a reference voltage line;

a modulated signal output;

two switching units, each of said switching units comprising: an input, a switching output, and a first switch connected between said input and said switching output, said switching unit being in a first switched state when said first switch is closed;

a second switch associated with each switching unit and connected between said associated switching unit and the modulated signal output, for activating said switching unit by closing said second switch;

a third switch associated with each of said switching units and connected between said associated switching unit and the modulated signal output;

the output of each of said switching units for supplying pulses having an amplitude varying between the level of the voltage on the input of that switching unit when that switching unit is in said first state, and the level of a voltage on said reference voltage line when that switching unit is in a second state in which the first switch of that switching unit is open;

wherein when the first switch of that switching unit is switched from said first state to said second state while the third switch of that switching unit remains open, said third switch remaining open during at least a portion of the duration of said first state.

2. The device according to claim 1 , wherein each switching unit further comprises a diode connected between the reference voltage line and the switching output of said switching unit to establish the second switched state when the first switch is open.

3. The device according to claim 1 , wherein each switching unit further comprises a fourth switch connected between the reference voltage line and the switching output of said switching unit to establish the second switched state when the first switch is open.

4. The device according to claim 3 , wherein the fourth switch of each switching unit comprises a transistor and a diode connected in parallel on said transistor and directed to be on when said transistor is reverse-biased.

5. The device according to claim 1 , wherein the second switch associated with each switching unit is between the switching output of said switching unit and the modulated signal output.

6. The device according to claim 1 , wherein the first, second and third switches comprise transistors.

7. The device according to claim 6 , wherein the first, second and third switches comprise diodes connected, respectively, in parallel with each of the transistors of said switches, and directed to be on when said transistor is reverse-biased.

8. The device according to claim 7 , wherein the transistors of the first, second and third switches are insulated gate bipolar transistors.

9. The device according to claim 6 , wherein the transistors of the first switches are silicon carbide field effect transistors, and the second and third switches comprise diodes connected, respectively, in parallel with each of the transistors of said switches and directed to be on when said transistor is reverse-biased.

10. The device according to claim 7 , wherein the transistor of the first switch of each switching unit is a MOS field effect transistor, the second switch associated with said switching unit comprising a plurality of series-connected diodes in parallel with the transistor of said second switch and directed to be on when said transistor is reverse-biased.

11. The device according to claim 7 , comprising a fifth switch connected between the reference voltage line and the modulated signal output.

12. The device according to claim 11 , wherein the fifth switch comprises two MOS field effect transistors connected in series and directed to conduct current in opposite directions, said fifth switch comprising, for each of said two transistors, a diode connected in parallel on each said transistor and directed to be on when said transistor is reverse-biased.

13. The device according to claim 1 , comprising for each switching unit:

first control means acting on the first switch of said switching unit to close or open said first switch to switch from the first switched state to the second switched state, while keeping the third switch open, and

second control means acting on the third switch of said switching unit to close said third switch after switching from the second switched state to the first switched state.

14. A converter device according to claim 1 in combination with additional elements, for outputting a secured AC voltage as an uninterruptible power supply, said additional elements comprising a rectifier having an AC input and a plurality of DC outputs, and two electrically conductive lines connected to said device for supplying DC voltages of opposite signs to said device from outputs of the rectifier having an AC input.