System for balancing the voltage of series-connected semiconductor elements

1. An electronic device comprising:

a plurality of series-connected diodes; and

a respective circuit coupled in parallel with each of said plurality of series-connected diodes, each circuit comprising

a comparator configured to compare data representative of a voltage across a respective diode with a reference voltage representative of a voltage applied to the plurality of series-connected diodes divided by a number of the plurality of series-connected diodes, and

a resistive element having an adjustable value coupled to said comparator and configured to be controlled by said comparator.

2. The electronic circuit of claim 1 , wherein each circuit further comprises a first resistive dividing bridge coupled across a respective diode so that the data representative of the voltage across the respective diode is available from midpoint of the first resistive divider.

3. The electronic circuit of claim 1 , wherein said resistive element comprises a metal oxide semiconductor (MOS) transistor.

4. The electronic circuit of claim 1 , wherein said comparator comprises a first amplifier having a first input receiving the data representative of the voltage across a respective diode and having a second input receiving the reference voltage.

5. The electronic circuit of claim 4 , wherein the first amplifier comprises a first operational amplifier.

6. The electronic circuit of claim 4 , further comprising a second amplifier coupled to the first amplifier and configured as a subtractor and to generate the reference voltage.

7. The electronic circuit of claim 6 , wherein the first amplifier comprises a first operational amplifier, and the second amplifier comprises a second operational amplifier.

8. The electronic circuit of claim 7 , further comprising:

first terminals configured to be coupled between the terminals of a respective diode;

second terminals configured to be respectively coupled to a previous circuit and to a next circuit;

a second resistive element;

a third resistive element; and

a second resistive bridge coupled to said second terminals and having a midpoint, wherein said second operational amplifier has first and second inputs, and wherein the midpoint of the second resistive bridge is coupled to the first input of said second operational amplifier, wherein said second input of said second operational amplifier is coupled, by said second resistive element, to one of said second terminals, and, by said third resistive element, to one of said first terminals.

9. The electronic circuit of claim 1 , further comprising:

first terminals configured to be coupled between terminals of a respective diode; and

second terminals configured to be respectively coupled to a previous circuit and to a next circuit.

10. An electronic device comprising:

a plurality of series-connected diodes; and

a respective circuit coupled in parallel with each of said plurality of series-connected diodes, each circuit comprising

a comparator configured to compare data representative of a voltage across a respective diode with a reference voltage representative of a voltage applied to the plurality of series-connected diodes divided by a number of the plurality of series-connected diodes, and

a MOS transistor having an adjustable resistance configured to be controlled by said comparator.

11. The electronic circuit of claim 10 , wherein each circuit further comprises a first resistive dividing bridge coupled across a respective diode so that the data representative of the voltage across the respective diode is available from midpoint of the first resistive divider.

12. The electronic circuit of claim 10 , wherein said comparator comprises a first amplifier having a first input receiving the data representative of the voltage across a respective diode and having a second input receiving the reference voltage.

13. The electronic circuit of claim 12 , wherein the first amplifier comprises a first operational amplifier.

14. The electronic circuit of claim 12 , further comprising a second amplifier coupled to the first amplifier and configured as a subtractor and to generate the reference voltage.

15. The electronic circuit of claim 14 , wherein the first amplifier comprises a first operational amplifier, and the second amplifier comprises a second operational amplifier.

16. The electronic circuit of claim 15 , further comprising:

first terminals configured to be coupled between the terminals of a respective diode;

second terminals configured to be respectively coupled to a previous circuit and to a next circuit;

a second resistive element;

a third resistive element; and

a second resistive bridge coupled to said second terminals and having a midpoint, wherein said second operational amplifier has first and second inputs, and wherein the midpoint of the second resistive bridge is coupled to the first input of said second operational amplifier, wherein said second input of said second operational amplifier is coupled, by said second resistive element, to one of said second terminals, and, by said third resistive element, to one of said first terminals.

17. The electronic circuit of claim 10 , further comprising:

first terminals configured to be coupled between terminals of a respective diode; and

second terminals configured to be respectively coupled to a previous circuit and to a next circuit.

18. A method of balancing a voltage across a plurality of series-connected diodes, the method comprising:

operating a respective circuit coupled in parallel with each of the plurality of series-connected diodes, each circuit comprising

a comparator configured to compare data representative of a voltage across a respective diode with a reference voltage representative of a voltage applied to the plurality of series-connected diodes divided by a number of the plurality of series-connected diodes, and

a resistive element having an adjustable value coupled to said comparator and configured to be controlled by said comparator.

19. The method of claim 18 , wherein each circuit further comprises a first resistive dividing bridge coupled across a respective diode so that the data representative of the voltage across the respective diode is available from midpoint of the first resistive divider.

20. The method of claim 18 , wherein said comparator comprises a first amplifier having a first input receiving the data representative of the voltage across a respective diode and having a second input receiving the reference voltage.

21. The method of claim 20 , wherein each circuit further comprises a second amplifier coupled to the first amplifier and configured as a subtractor and to generate the reference voltage.