DC-DC converter

{
  "publication_number": "US11121631B2",
  "country": "US",
  "kind": "B2",
  "title": "DC-DC converter",
  "abstract": "ADC-to-DC converter which is configured to provide a main DC supply and an auxiliary DC supply from a single energy source such as a fuel cell. The main supply voltage may be greater than the voltage provided by the energy source, and the auxiliary supply voltage may be less than the voltage provided by the energy source. In some embodiments boost and buck conversion are provided by a single switching bridge, such as an inverter. Such an inverter may comprise three-legs connected between a main output voltage and a reference or ground voltage. Each leg of such an inverter may comprise two switches connected in series. These legs may share a common DC voltage link, for example a common ground and positive rail.",
  "claims": [
    "1. A DC-to-DC converter apparatus comprising: an input for connection to a DC power supply to be converted; an input inductive energy store, a capacitive energy store, a reference voltage connection, and an inverter suitable for providing AC electrical power for controlling an electric traction motor, wherein the inverter comprises a plurality of switching legs wherein each switching leg of the inverter is arranged for switching a DC voltage to provide an electrical signal of the AC electrical power, wherein at least one switching leg of the inverter is arranged to provide a boost stage switch comprising: a first coupling connected to the reference voltage connection, a second coupling connected to an output of the inductive energy store, and a third coupling, and wherein the capacitive energy store is connected between the third coupling and the reference voltage connection and the input inductive energy store is connected between the input and the second coupling; the DC-to-DC converter further comprising a controller, configured to operate the switch based on a boost voltage difference between: (i) the voltage, V b, between the third coupling and the reference voltage connection; and (ii) a boost target voltage, V b Ref.",
    "2. The apparatus of claim 1 wherein the at least one switching leg of the boost stage switch comprises a first switching leg and a second switching leg arranged in parallel with each other between the first coupling and the third coupling.",
    "3. The apparatus of claim 2 wherein the second coupling comprises: a first connection between two switches of the first switching leg, the two switches of the first switching leg being connected in series by said first coupling, and a second connection between two switches of the second switching leg, the two switches of the second switching leg being connected in series by said second coupling.",
    "4. The apparatus of claim 3 wherein the input inductive energy store comprises a first inductor connected between the input and the first connection, and a second inductor connected between the input and the second connection.",
    "5. The apparatus of claim 4 wherein the first inductor and the second inductor are in parallel between the input and the second coupling.",
    "6. The apparatus of claim 2, wherein the controller is configured to operate the first switching leg to provide a first current from the input inductive energy store, and to operate the second switching leg to provide a second current from the input inductive energy store, and to control the first current and the second current based on the boost voltage difference.",
    "7. The apparatus of claim 1 comprising, a buck stage switch comprising a first coupling connected to the reference voltage connection, a second coupling connected to an output inductive energy store, and a third coupling, wherein the capacitive energy store is connected between the third coupling of the buck stage switch and the reference voltage connection.",
    "8. A method of controlling an electric motor inverter, the inverter suitable for providing AC electrical power for controlling an electric traction motor, wherein the inverter comprises a plurality of switching legs wherein each switching leg of the inverter is arranged for switching a DC voltage to provide an electrical signal of the AC electrical power, wherein the electric motor inverter is adapted to provide a DC-to-DC converter, the method comprising: obtaining a first difference signal indicating a boost voltage difference between a target boost voltage and a DC voltage across the inverter; determining a target current to be provided to a capacitor connected across the inverter to reduce the first voltage difference; obtaining a second difference signal indicating a first current difference between: (i) the target current; and (ii) current flowing between a first input inductor and a mid-connection of a first boost leg of the inverter; and, operating the first boost leg of the inverter to reduce the first current difference.",
    "9. The method of claim 8 in which the first input inductor is coupled between a DC supply input and the mid-connection of the first boost leg, and a second input inductor is coupled between a mid-connection of a second boost leg of the inverter and the DC supply input, the method comprising: determining a second target current I 2 Ref to be provided from the second boost leg of the inverter to the capacitor to reduce the first voltage difference; and operating the second boost leg of the inverter to reduce the difference between: (i) the target current I 2 Ref; and (ii) current I 2 flowing between the second input inductor and a mid-connection of a second boost leg of the inverter.",
    "10. The method of claim 8 comprising, obtaining a third difference signal indicating a buck voltage difference between a target buck voltage and a voltage at a buck output of the converter, wherein the buck output is coupled to a mid-connection of a buck leg of the inverter by a first output inductor; and operating the buck leg of the inverter to reduce the buck voltage difference, wherein operating the buck leg comprises determining a target buck current to be provided in the first output inductor to reduce the buck voltage difference, and wherein operating the buck leg comprises determining a second current difference between: (i) the target buck current; and (ii) current flowing between the first output inductor and the mid-connection of the buck leg of the inverter; and, operating the buck leg to reduce the second current difference.",
    "11. A computer program product comprising program instructions configured to program a programmable controller to perform the method of claim 9.",
    "12. A controller for controlling an inverter, wherein the controller is configured to perform the method of claim 9.",
    "13. An analogue control circuit configured to perform the method of claim 9.",
    "14. A DC power supply system for a materials handling vehicle such as a lift truck, the system comprising: a main power supply circuit; and an auxiliary power supply circuit arranged to provide DC power at lower voltage than the main power supply circuit; an inverter, and a controller configured to operate the inverter, and to: obtain a first difference signal indicating a boost voltage difference between a target boost voltage and a DC voltage across the inverter, wherein the DC voltage across the inverter is connected to a boost output to provide DC electrical power to the main power supply circuit; determine a target current to be provided to a capacitor connected across the inverter to reduce the first voltage difference; operate a first boost leg of the inverter to reduce a first current difference between: (i) the target current I 1 Ref; and (ii) current, I 1, flowing between a first input inductor and a mid-connection of a first boost leg of the inverter; and, to operate a buck leg of the inverter to reduce a buck voltage difference between: (i) a target buck voltage; and (ii) a voltage at a buck output of the converter, wherein the buck output is arranged to provide DC electrical power to the auxiliary power circuit and is coupled to a mid-connection of a buck leg of the inverter by a first output inductor.",
    "15. The system of claim 14 wherein the controller is configured to determine a target buck current to be provided in the first output inductor to reduce the buck voltage difference, and wherein operating the buck leg comprises operating the buck leg to reduce the difference between: (i) the target buck current I 3 Ref; and (ii) current, I 3, flowing between the first output inductor and the mid-connection of the buck leg of the inverter.",
    "16. The system of claim 14 in which the first input inductor is coupled between a DC supply input and the mid-connection of the first boost leg, and a second input inductor is coupled between a mid-connection of a second boost leg of the inverter and the DC supply input, and the controller is configured to: determine a second target current I 2 Ref to be provided from the second boost leg of the inverter to the capacitor to reduce the first voltage difference; and operate the second boost leg of the inverter to reduce the difference between: (i) the target current I 2 Ref; and (ii) current I 2 flowing between the second input inductor and a mid-connection of a second boost leg of the inverter.",
    "17. A method of controlling an inverter to provide a buck-boost DC-to-DC converter for a materials handling vehicle, the method comprising: obtaining a first difference signal indicating a boost voltage difference between a target boost voltage and a DC voltage across the inverter; determining a target current to be provided to a capacitor connected across the inverter to reduce the first voltage difference; operating a first boost leg of the inverter to reduce a first current difference between: (i) the target current I 1 Ref; and (ii) current, I 1, flowing between a first input inductor and a mid-connection of a first boost leg of the inverter; and, operating a buck leg of the inverter to reduce a buck voltage difference between: (i) a target buck voltage; and (ii) a voltage at a buck output of the converter, wherein the buck output is coupled to a mid-connection of a buck leg of the inverter by a first output inductor.",
    "18. The method of claim 17 wherein operating the buck leg comprises determining a target buck current to be provided in the first output inductor to reduce the buck voltage difference.",
    "19. The method of claim 18 wherein operating the buck leg comprises operating the buck leg to reduce the difference between: (i) the target buck current; and (ii) current flowing between the first output inductor and the mid-connection of the buck leg of the inverter.",
    "20. The method of claim 17 in which the first input inductor is coupled between a DC supply input and the mid-connection of the first boost leg, and a second input inductor is coupled between a mid-connection of a second boost leg of the inverter and the DC supply input, the method comprising: determining a second target current I 2 Ref to be provided from the second boost leg of the inverter to the capacitor to reduce the first voltage difference; and operating the second boost leg of the inverter to reduce the difference between: (i) the target current I 2 Ref; and (ii) current I 2 flowing between the second input inductor and a mid-connection of a second boost leg of the inverter."
  ],
  "description_excerpt": "The present invention relates to apparatus and methods, and more particularly to apparatus and methods for direct current (DC) to DC conversion, for example for providing electrical power supplies.\n\nA DC-to-DC converter converts a source of DC electrical energy from one voltage level to another. Typically, so called boost converters provide an output voltage which is greater than the voltage of the source. On the other hand, so called buck converters provide an output voltage which is less than the voltage of the source.\n\nElectrical and electronic devices often contain several sub-circuits, each with its own voltage level requirement different from that supplied by the source. As energy is drained from the source, or it is recharged, the voltage it provides may vary. Typically, electrical and electronic circuits may require power supply voltages within a selected range.\n\nHybrid and electrical vehicles are increasingly prevalent. Both on-highway and off-highway vehicles may make complex demands of an electrical power supply.\n\nAspects and examples of the present disclosure are set out in the claims and are otherwise described herein. The present disclosure aims to address at least a part of the above technical problem.\n\nEmbodiments aim to reduce the number and weight of electrical and/or electronic components required to provide DC-DC power conversion. Some embodiments are of particular utility in systems which use a fuel cell as their DC energy source.\n\nSome embodiments employ an electric motor inverter adapted to provide the switching phases of a DC-to-DC converter.",
  "cpc": [
    "H02M 3/1582",
    "B60L 53/24",
    "H02M 1/008",
    "H02M 1/009",
    "H02M 3/155",
    "H02M 3/1552",
    "H02M 7/48",
    "H02P 27/06",
    "Y02T 10/70",
    "Y02T 10/7072",
    "Y02T 90/14"
  ],
  "ipc": [
    "H02M 3/158",
    "B60L 15/00"
  ],
  "assignees": [
    "Sevcon Ltd"
  ],
  "inventors": [
    "Peter Barrass"
  ],
  "filing_date": "2018-04-19",
  "publication_date": "2021-09-14",
  "grant_date": "2021-09-14",
  "priority_date": "2017-04-19",
  "application_number": "US-201816605930-A",
  "family_id": "58744523",
  "cited_by_count": 1,
  "citations": [
    "US4920475A",
    "US20120163035A1",
    "US20150191133A1",
    "EP2765022A2",
    "US20160236579A1",
    "EP3238979A1",
    "DE102016209905A1"
  ]
}