Capacitive DC Power Transformer

• US 20150015088A1
• Filed: 06/25/2014
• Published: 01/15/2015
• Est. Priority Date: 07/11/2013
• Status: Active Grant

• Current Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Petersen, Holger
• Granted Patent: US 9,997,999 B2
• Time in Patent Office: Days
• US Class Current: 307/110
• CPC Class Codes: H02M 1/15 using active elements
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/071 adapted to generate a negative voltage output from a positive voltage source
• CPC Class Codes: H02M 3/072 adapted to generate an output voltage whose value is lower than the input voltage

Abstract

The present document relates to power transformers for electronic computing devices. In particular, a power converter configured to convert electrical power at a DC input voltage Vin into electrical power at a DC output voltage is described. The power converter comprises a plurality of flying capacitors, and a plurality of switches which are configured to arrange the plurality of flying capacitors in accordance to a sequence of operation phases. The power converter comprises a control unit configured to control the plurality of switches to repeat the sequence of operation phases at a duty cycle frequency. The plurality of flying capacitors is arranged in series during the operation phases of the sequence of operation phases. The sequence of operation phases comprises at least two operation phases during which the plurality of flying capacitors is arranged in a different order.

Claims

1. A power converter configured to convert electrical power at a DC input voltage Vin into electrical power at a DC output voltage Vout, the power converter comprising

a plurality of flying capacitors;

a plurality of switches configured to arrange the plurality of flying capacitors in accordance to a sequence of operation phases;

a control unit configured to control the plurality of switches to repeat the sequence of operation phases at a duty cycle frequency;

wherein the plurality of flying capacitors is arranged in series during the operation phases of the sequence of operation phases; and

wherein the sequence of operation phases comprises at least two operation phases during which the plurality of flying capacitors is arranged in a different order.

2. The power converter of claim 1, wherein

in case of a voltage down-conversion, the serial arrangement of flying capacitors is arranged in parallel to the input voltage Vin during the operation phases of the sequence of operation phases;

and the sequence of operation phases comprises at least two operation phases during which different subsets of the plurality of flying capacitors are arranged in parallel to the output voltage Vout; and

/or

in case of a voltage up-conversion, the serial arrangement of flying capacitors is arranged in parallel to the output voltage Vout during the operation phases of the sequence of operation phases; and

the sequence of operation phases comprises at least two operation phases during which different subsets of the plurality of flying capacitors are arranged in parallel to the input voltage Vin; and

/or

in case of inversion, only a subset of the serial arrangement of flying capacitors is arranged in parallel to the input voltage Vin or the output voltage Vout during the operation phases of the sequence of operation phases.

3. The power converter of claim 1, wherein within each of the sequence of operation phases at least one of the plurality of flying capacitors is charged and at least one of the plurality of flying capacitors is discharged.

4. The power converter of claim 1, wherein within each of the sequence of operation phases, a first subset of the plurality of flying capacitors forms a charging network which is being charged, and a second subset of the plurality of flying capacitors, which is complementary to the first subset, forms a discharge network which is being discharged.

5. The power converter of claim 4, wherein the sequence of operation phases are such that each of the plurality of flying capacitors is part of the charging network at least during one of the sequence of operation phases and is part of the discharge network at least during another one of the sequence of operation phases.

6. The power converter of claim 4, further comprising

a first reservoir capacitor arranged in parallel to the charging network;

and/or

a second reservoir capacitor arranged in parallel to the discharge network;

wherein the arrangement of the first and/or second reservoir capacitor remains unchanged during the

sequence of operation phases.

7. The power converter of claim 6, wherein if the power converter comprises the first and second reservoir capacitors, the first reservoir capacitor is arranged to connect the input voltage Vin with the output voltage Vout and the second reservoir capacitor is arranged to connect the output voltage Vout with a reference potential of the input voltage Vin.

8. The power converter of claim 4, wherein

the control unit is configured to control the plurality of switches to arrange the plurality of flying capacitors in accordance to at least one intermediate phase between a first and a succeeding second operation phase of the sequence of operation phases;

and

during the intermediate phase a first flying capacitor which is part of the discharge network during the first operation phase and which is part of the charging network during the second operation phase is arranged in parallel to a second flying capacitor which is part of the charging network during the first operation phase and which is part of the discharge network during the second operation phase operation phase.

9. The power converter of claim 4, wherein a mid-point between charging network and discharge network is coupled to a reference potential of the input voltage Vin.

10. The power converter of claim 4, wherein

the plurality of flying capacitors comprise N_T flying capacitors;

the charging network comprises N_C flying capacitors;

the discharge network comprises N_D flying capacitors, with N_T=N_C+N_D;

the sequence of operation phases comprises at least N_T operation phases;

the operation phases are such that each of the plurality of flying capacitors is part of the charging network for at least N_C phases and part of the discharge network for at least N_D phases.

11. The power converter of claim 10, wherein a target ratio of the input voltage Vin and the output voltage Vout corresponds to

N_D/N_T for voltage down-conversion;

and/or

N_T/N_D for voltage up-conversion; and

/or

N_C/N_D for voltage inversion.

12. The power converter of claim 1, wherein

the power converter further comprises one or more short cut switches (Sa, Sb, Sc) configured to short cut one or more of the plurality of flying capacitors;

and

the control unit is configured to control the one or more short cut switches (Sa, Sb, Sc) in accordance to a conversion ratio between the input voltage and the output voltage to be provided by the power converter.

13. The power converter of claim 1, wherein

the control unit is configured to control the plurality of switches to arrange the plurality of flying capacitors in accordance to at least one transition phase for transiting from a first to a succeeding second operation phase of the sequence of operation phases;

during at least one transition phase, at least one of the plurality of flying capacitors is decoupled from the input voltage Vin and from the output voltage Vout.

14. The power converter of claim 1, wherein the control unit is configured to adapt the duty cycle frequency as a function of the amount of electrical power provided at the DC output voltage.

15. A differential power converter configured to convert electrical power at a DC input voltage Vin into electrical power at a differential output voltage, the differential power converter comprising

a first power converter, configured to convert the electrical power at the DC input voltage Vin into electrical power at a first DC output voltage;

and

a second power converter, configured to convert the electrical power from a second DC output voltage back into the DC input voltage Vin;

wherein the differential output voltage corresponds to a difference of the first and second DC output voltages.

16. The differential power converter of claim 15 wherein said first power converter is a voltage divider and wherein said second power converter is a voltage multiplier.

17. The differential power converter of claim 15 wherein said first power converter and said second power converter are comprised of flying capacitors.

18. A method for converting electrical power at a DC input voltage into electrical power at a DC output voltage comprising the steps of:

providing flying capacitors, a discharge network and a charging network, and

controlling permutations of said flying capacitors between said discharge network and said charging network.

19. A method of providing a power converter which converts electrical power at a DC input voltage Vin into electrical power at a DC output voltage Vout, the power converter comprising the steps of:

providing a plurality of flying capacitors;

providing a plurality of switches which arrange said plurality of flying capacitors in accordance to a sequence of operation phases;

providing a control unit which controls said plurality of switches to repeat said sequence of operation phases at a duty cycle frequency;

wherein said plurality of flying capacitors is arranged in series during said operation phases of said sequence of operation phases; and

wherein said sequence of operation phases comprises at least two operation phases during which the plurality of flying capacitors is arranged in a different order.

20. The method of providing a power converter of claim 19, wherein

in case of a voltage down-conversion, said serial arrangement of flying capacitors is arranged in parallel to said input voltage Vin during said operation phases of said sequence of operation phases;

and said sequence of operation phases comprises at least two operation phases during which different subsets of said plurality of flying capacitors are arranged in parallel to said output voltage Vout; and

/or

in case of a voltage up-conversion, said serial arrangement of flying capacitors is arranged in parallel to said output voltage Vout during the operation phases of said sequence of operation phases; and

said sequence of operation phases comprises at least two operation phases during which different subsets of said plurality of flying capacitors are arranged in parallel to said input voltage Vin; and

/or

in case of inversion, only a subset of said serial arrangement of flying capacitors is arranged in parallel to said input voltage Vin or said output voltage Vout during the operation phases of said sequence of operation phases.

21. The method of providing a power converter of claim 19, wherein within each of said sequence of operation phases at least one of said plurality of flying capacitors is charged and at least one of said plurality of flying capacitors is discharged.

22. The method of providing a power converter of claim 19, wherein within each of said sequence of operation phases, a first subset of said plurality of flying capacitors forms a charging network which is being charged, and a second subset of said plurality of flying capacitors, which is complementary to said first subset, forms a discharge network which is being discharged.

23. The method of providing a power converter of claim 22, wherein said sequence of operation phases are such that each of said plurality of flying capacitors is part of said charging network at least during one of said sequence of operation phases and is part of said discharge network at least during another one of said sequence of operation phases.

24. The method of providing a power converter of claim 22, further comprising

a first reservoir capacitor arranged in parallel to said charging network;

and/or

a second reservoir capacitor arranged in parallel to said discharge network;

wherein said arrangement of said first and/or second reservoir capacitor remains unchanged during said

sequence of operation phases.

25. The method of providing a power converter of claim 24, wherein if said power converter comprises said first and second reservoir capacitors, said first reservoir capacitor connects said input voltage Vin with said output voltage Vout and said second reservoir capacitor connects said output voltage Vout with a reference potential of said input voltage Vin.

26. The method of providing a power converter of claim 22, wherein

said control unit controls

said plurality of switches to arrange said plurality of flying capacitors in accordance to at least one intermediate phase between a first and a succeeding second operation phase of said sequence of operation phases;

and

during said intermediate phase a first flying capacitor which is part of said discharge network during said first operation phase and which is part of said charging network during said second operation phase is arranged in parallel to a second flying capacitor which is part of said charging network during said first operation phase and which is part of said discharge network during said second operation phase operation phase.

27. The method of providing a power converter of claim 22, wherein a mid-point between charging network and discharge network is coupled to a reference potential of said input voltage Vin.

28. The method of providing a power converter of claim 22, wherein

said plurality of flying capacitors comprise N_T flying capacitors;

said charging network comprises N_C flying capacitors;

said discharge network comprises N_D flying capacitors, with N_T=N_C+N_D;

said sequence of operation phases comprises at least N_T operation phases;

said operation phases are such that each of said plurality of flying capacitors is part of said charging network for at least N_C phases and part of said discharge network for at least N_D phases.

29. The method of providing a power converter of claim 28, wherein a target ratio of the input voltage Vin and the output voltage Vout corresponds to

N_D/N_T for voltage down-conversion;

and/or

N_T/N_D for voltage up-conversion; and

/or

N_C/N_D for voltage inversion.

30. The method of providing a power converter of claim 19, wherein

said power converter further comprises one or more short cut switches (Sa, Sb, Sc) short cuts one or more of said plurality of flying capacitors;

and

said control unit controls said one or more short cut switches (Sa, Sb, Sc) in accordance to a conversion ratio between said input voltage and said output voltage to be provided by said power converter.

31. The method of providing a power converter of claim 19, wherein

said control unit controls said plurality of switches to arrange said plurality of flying capacitors in accordance to at least one transition phase for transiting from a first to a succeeding second operation phase of said sequence of operation phases;

during said the at least one transition phase, at least one of said plurality of flying capacitors is decoupled from said input voltage Vin and from said output voltage Vout.

32. The method of providing a power converter of claim 19, wherein said control unit adapts said duty cycle frequency as a function of said amount of electrical power provided at said DC output voltage.

33. A method of providing a differential power converter which converts electrical power at a DC input voltage Vin into electrical power at a differential output voltage, the differential power converter comprising the steps of:

providing a first power converter, which converts said electrical power at said DC input voltage Vin into electrical power at a first DC output voltage; and

providing a second power converter, which converts said electrical power from a second DC output voltage back into said DC input voltage Vin;

wherein said differential output voltage corresponds to a difference of said first and second DC output voltages.

34. The method of providing a differential power converter of claim 33 wherein said first power converter is a voltage divider and wherein said second power converter is a voltage multiplier.

35. The method of providing a differential power converter of claim 33 wherein said first power converter and said second power converter are comprised of flying capacitors.