WO2022160305A1 - 一种转换电路、电压转换装置及电动汽车 - Google Patents

一种转换电路、电压转换装置及电动汽车 Download PDF

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Publication number
WO2022160305A1
WO2022160305A1 PCT/CN2021/074526 CN2021074526W WO2022160305A1 WO 2022160305 A1 WO2022160305 A1 WO 2022160305A1 CN 2021074526 W CN2021074526 W CN 2021074526W WO 2022160305 A1 WO2022160305 A1 WO 2022160305A1
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Prior art keywords
switch tube
voltage
conversion circuit
potential
buck
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PCT/CN2021/074526
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English (en)
French (fr)
Inventor
李小秋
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华为数字能源技术有限公司
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Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to CN202180002853.7A priority Critical patent/CN113796004B/zh
Priority to EP21921906.0A priority patent/EP4270754A4/en
Priority to PCT/CN2021/074526 priority patent/WO2022160305A1/zh
Publication of WO2022160305A1 publication Critical patent/WO2022160305A1/zh
Priority to US18/361,016 priority patent/US20230369979A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
    • B60L53/20—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by converters located in the vehicle
    • B60L53/22—Constructional details or arrangements of charging converters specially adapted for charging electric vehicles
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0095—Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/083—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the ignition at the zero crossing of the voltage or the current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
    • H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2210/00—Converter types
    • B60L2210/10—DC to DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4837—Flying capacitor converters

Definitions

  • the present application relates to the technical field of new energy vehicles, and in particular, to a conversion circuit, a voltage conversion device and an electric vehicle.
  • Switched capacitor circuit also known as switched capacitor boost topology, has the advantages of high efficiency and small size, so it is widely used in various types of electronic equipment.
  • the switched capacitor circuit mainly includes a plurality of conversion switches and a plurality of conversion capacitors. Through the plurality of conversion switches, the plurality of conversion capacitors can be controlled to be charged and discharged periodically, thereby realizing boost conversion.
  • the ratio between the output voltage of the switched capacitor circuit and the input voltage can be called the transformation ratio of the switched capacitor circuit.
  • the transformation ratios that can be achieved by switched capacitor circuits are mostly integers, although in some current conversion circuits, a buck circuit and a switched capacitor circuit can be integrated at the same time, so that the conversion circuit can achieve continuous transformation ratios.
  • the maximum transformation ratio that this type of conversion circuit can achieve is also limited by the transformation ratio of the switched capacitor circuit.
  • the present application provides a conversion circuit, a voltage conversion device and an electric vehicle.
  • the conversion circuit can support continuous adjustment of the conversion ratio, and compared with the switched capacitor circuit, the conversion circuit can achieve a higher conversion ratio.
  • the present application provides a conversion circuit, which mainly includes a buck-boost buck-boost unit and a switched capacitor unit.
  • the high potential terminal of the buck-boost unit and the high potential terminal of the switched capacitor unit are both connected to the high potential output terminal of the conversion circuit
  • the first intermediate terminal of the buck-boost unit is connected to the second intermediate terminal of the switched capacitor unit
  • the buck Both the low potential terminal of the boost unit and the low potential terminal of the switched capacitor unit are connected to the low potential output terminal of the conversion circuit.
  • the buck-boost unit can receive the first input voltage, perform buck conversion or boost conversion on the first input voltage, use the first input voltage after buck conversion or boost conversion as a forward voltage, and convert the forward voltage through the first intermediate terminal. supplied to the switched capacitor unit.
  • the switched capacitor unit can boost the forward voltage.
  • the high-potential output terminal and the low-potential output terminal of the conversion circuit can output a first output voltage, where the first output voltage is a forward voltage after the boost conversion.
  • the buck-boost unit can perform both buck conversion on the first input voltage and boost conversion on the first input voltage.
  • the forward voltage may be any voltage not less than 1/N of the first input voltage and not greater than the first input voltage.
  • N represents the transformation ratio of the switched capacitor unit, and N is an integer greater than or equal to 1.
  • the switched capacitor unit boosts the forward voltage, so that the boosted forward voltage (that is, the first output voltage) can reach between the first input voltage and N times the first input voltage any voltage.
  • the forward voltage may be any voltage not less than the first input voltage.
  • the switched capacitor unit boosts the forward voltage, so that the boosted forward voltage (ie, the first output voltage) can reach any voltage that is not less than N times the first input voltage.
  • the conversion circuit provided by the present application can not only support continuous adjustment of the conversion ratio, but also the maximum conversion ratio of the conversion circuit is no longer limited by the conversion ratio of the switched capacitor unit, and the first output voltage of the conversion circuit can be not less than the first output voltage. Any voltage of the input voltage is beneficial to improve the universality of the conversion circuit.
  • the buck-boost unit includes a first diode, a second diode, a first switch tube, a second switch tube and a first inductor.
  • One end of the first inductor is connected to the high-potential input end of the conversion circuit, and the other end of the first inductor is connected to the anode of the first diode, the first electrode of the first switch tube, and the first electrode of the second switch tube, respectively. connect.
  • the cathode of the first diode is connected to the high potential output terminal of the conversion circuit
  • the second electrode of the first switch tube is connected to the anode of the second diode
  • the cathode of the second diode is connected to the second middle of the switched capacitor unit. end connection.
  • the second electrode of the second switch tube is respectively connected to the low-potential input terminal and the low-potential output terminal of the conversion circuit, and the high-potential input terminal and the low-potential input terminal of the conversion circuit are used for receiving the first input voltage.
  • the buck-boost unit can buck convert the first input voltage.
  • the first switch tube can be kept off during the cycle time; the second switch tube can be kept on during the first period of the cycle time to charge the first inductor.
  • the second switch is kept off during the second period of the cycle time to discharge the first inductor.
  • the buck-boost unit may perform buck conversion on the first input voltage, and the obtained first output voltage may be any voltage not less than the first input voltage and not greater than N times the first input voltage.
  • the buck-boost unit can boost convert the first input voltage.
  • the second switch tube can be kept on during the cycle time.
  • the first switch tube may remain on during the first period of the cycle time to charge the inductor.
  • the second switch is kept off during the second period of the cycle time to discharge the inductor.
  • the buck-boost unit may perform boost conversion on the first input voltage, and the obtained first output voltage may be any voltage that is not less than N times the first input voltage.
  • the conversion circuit provided by the present application also supports bidirectional voltage conversion, that is, the conversion circuit can not only receive the first input voltage through the high-potential input terminal and the low-potential input terminal, and pass the high-potential input terminal and the low-potential input terminal.
  • the potential output terminal and the low potential output terminal output the first output voltage
  • the high potential output terminal and the low potential output terminal of the conversion circuit can also receive the second input voltage
  • the high potential input terminal and the low potential input terminal of the conversion circuit can also A second output voltage is output.
  • the switched capacitor unit may also perform step-down conversion on the second input voltage, use the step-down converted second input voltage as a reverse voltage, and provide the reverse voltage to the buck-boost unit through the second intermediate terminal.
  • the buck-boost unit can perform buck conversion or boost conversion on the above reverse voltage, and use the reverse voltage after buck conversion or boost conversion as the second output voltage, and output the second output voltage through the high-potential input terminal and the low-potential input terminal of the conversion circuit.
  • the output voltage can be performed by performing buck conversion or boost conversion on the above reverse voltage, and use the reverse voltage after buck conversion or boost conversion as the second output voltage, and output the second output voltage through the high-potential input terminal and the low-potential input terminal of the conversion circuit. The output voltage.
  • the reverse voltage provided by the switched capacitor unit to the buck-boost unit may be 1/N of the second input voltage.
  • the buck-boost unit can perform both buck conversion on the reverse voltage and boost conversion on the reverse voltage.
  • the second output voltage may be any voltage not greater than the reverse voltage, that is, the second output voltage may be any voltage not greater than 1/N of the second input voltage.
  • the second output voltage may be any voltage not less than the reverse voltage and not greater than N times the reverse voltage, that is, the second output voltage may be not less than the second input voltage 1/N of , and not greater than any voltage of the second input voltage.
  • the buck-boost unit may further include a third switch tube and a fourth switch tube, the third switch tube includes the above-mentioned first diode, and the fourth switch tube includes the above-mentioned second diode.
  • the first electrode of the third switch tube is connected to the high-potential output end of the conversion circuit, and the second electrode of the third switch tube is connected to the other end of the first inductor.
  • the first electrode of the fourth switch tube is connected to the second electrode of the second switch tube, and the second electrode of the fourth switch tube is connected to the second middle end of the switched capacitor unit.
  • the first switch tube includes a third diode, and the anode of the third diode It is connected to the first electrode of the fourth switch tube, and the cathode of the third diode is connected to the other end of the first inductor.
  • the second switch tube includes a fourth diode, the anode of the fourth diode is respectively connected to the low-potential input terminal and the low-potential output terminal of the conversion circuit, and the cathode of the fourth diode is connected to the other end of the first inductor.
  • the first switch tube and the second switch tube when the buck-boost unit converts the reverse voltage, the first switch tube and the second switch tube can be turned off, and the diodes in the first switch tube and the second switch tube can keep the first switch tube in the buck-boost unit.
  • the charging loop and the discharging loop of the inductor are turned on, so that the influence of the first switch tube and the second switch tube on the conversion process of the reverse voltage can be reduced.
  • the buck-boost unit can buck convert the reverse voltage.
  • the first switch tube, the second switch tube, and the third switch tube can be kept off during the cycle time.
  • the fourth switch tube can be kept on during the first period of the cycle time to charge the first inductor.
  • the fourth switch tube may be kept off during the second period of the cycle time to discharge the first inductor.
  • the buck-boost unit may perform buck conversion on the reverse voltage, and the obtained second output voltage may be any voltage not greater than 1/N of the second input voltage.
  • the buck-boost unit can boost the reverse voltage.
  • the first switch tube and the second switch tube can be kept off during the cycle time.
  • the fourth switch tube can be kept on during the cycle time.
  • the third switch tube can be kept on during the first period of the cycle time to charge the first inductor.
  • the third switch tube may be kept off during the second period of the cycle time to discharge the first inductor.
  • the buck-boost unit may perform boost conversion on the reverse voltage, and the obtained second output voltage may be no less than 1/N of the second input voltage and no greater than any voltage of the second input voltage.
  • the present application provides a voltage conversion device, which mainly includes a conversion circuit and a control circuit.
  • the conversion circuit may be any of the conversion circuits provided in the first aspect.
  • the conversion circuit may include a buck-boost buck-boost unit and a switched capacitor unit.
  • the high potential terminal of the buck-boost unit and the high potential terminal of the switched capacitor unit are both connected to the high potential output terminal of the conversion circuit
  • the first intermediate terminal of the buck-boost unit is connected to the second intermediate terminal of the switched capacitor unit
  • the buck Both the low potential terminal of the boost unit and the low potential terminal of the switched capacitor unit are connected to the low potential output terminal of the conversion circuit.
  • the control circuit can control the buck-boost unit to perform buck conversion or boost conversion on the first input voltage received, and use the first input voltage after buck conversion or boost conversion as the forward voltage, and the forward voltage is converted through the first intermediate terminal.
  • the control circuit controls the switched capacitor unit to boost and convert the forward voltage, wherein the high-potential output terminal and the low-potential output terminal of the conversion circuit can output a first output voltage, and the first output voltage can be the forward voltage after the boost conversion Voltage.
  • the buck-boost unit may include a first diode, a second diode, a first switch, a second switch, and a first inductor.
  • One end of the first inductor is connected to the high-potential input end of the conversion circuit, and the other end of the first inductor is connected to the anode of the first diode, the first electrode of the first switch tube, and the first electrode of the second switch tube, respectively. connect.
  • the cathode of the first diode is connected to the high potential output terminal of the conversion circuit
  • the second electrode of the first switch tube is connected to the anode of the second diode
  • the cathode of the second diode is connected to the second middle of the switched capacitor unit. end connection.
  • the second electrode of the second switch tube is respectively connected to the low-potential input terminal and the low-potential output terminal of the conversion circuit, and the high-potential input terminal and the low-potential input terminal of the conversion circuit are used for receiving the first input voltage.
  • the control circuit can control the buck-boost unit to buck convert the first input voltage.
  • the control circuit can control the first switch tube to keep off during the cycle time, and control the second switch tube to keep on during the first period of the cycle time, so as to charge the first inductor and control the second switch tube It remains off for the second period of the cycle time to discharge the first inductor.
  • the buck-boost unit may perform buck conversion on the first input voltage, and the obtained first output voltage may be any voltage not less than the first input voltage and not greater than N times the first input voltage.
  • the control circuit can first keep the first switch off, and adjust the duty cycle of the second switch. proportion. When the first output voltage reaches the first target voltage, the control circuit maintains the current duty cycle of the second switch tube. With this implementation, the control circuit can determine the duty cycle of the second switch tube, so that the first output voltage can reach the first target voltage.
  • the control circuit can control the buck-boost unit to perform boost conversion on the first input voltage.
  • the control circuit can control the second switch tube to keep on during the cycle time, and control the first switch tube to keep on during the third period of the cycle time, so as to charge the inductor, and control the first switch tube to keep on during the cycle time. remains off for the fourth period of time to discharge the inductor.
  • the buck-boost unit may perform boost conversion on the first input voltage, and the obtained first output voltage may be any voltage that is not less than N times the first input voltage.
  • the control circuit can first keep the second switch on, and adjust the duty cycle of the first switch. proportion of time. When the first output voltage reaches the first target voltage, the control circuit maintains the current duty cycle of the first switch tube. With this implementation, the control circuit can determine the duty cycle of the first switch tube, so that the first output voltage can reach the first target voltage.
  • the voltage conversion device provided by the present application also supports bidirectional voltage conversion, that is, the high-potential output terminal and the low-potential output terminal of the conversion circuit can also receive the second input voltage, and the The high potential input terminal and the low potential input terminal may also output a second output voltage.
  • the control circuit can also control the switched capacitor unit to perform step-down conversion on the second input voltage, use the step-down converted second input voltage as a reverse voltage, and provide the reverse voltage to the buck-boost unit through the second intermediate terminal; the control circuit
  • the buck-boost unit is controlled to perform buck conversion or boost conversion on the reverse voltage, and the reverse voltage after buck conversion or boost conversion is used as the second output voltage, and the second output voltage is output through the high-potential input terminal and the low-potential input terminal of the conversion circuit .
  • the buck-boost unit may further include a third switch tube and a fourth switch tube, the third switch tube includes a first diode, and the fourth switch tube includes a second diode.
  • the first electrode of the third switch tube is connected to the high-potential output end of the conversion circuit, and the second electrode of the third switch tube is connected to the other end of the first inductor.
  • the first electrode of the fourth switch tube is connected to the second electrode of the second switch tube, and the second electrode of the fourth switch tube is connected to the second middle end of the switched capacitor unit.
  • the first switch tube includes a third diode, and the anode of the third diode It is connected to the first electrode of the fourth switch tube, and the cathode of the third diode is connected to the other end of the first inductor.
  • the second switch tube includes a fourth diode, the anode of the fourth diode is respectively connected to the low-potential input terminal and the low-potential output terminal of the conversion circuit, and the cathode of the fourth diode is connected to the other end of the first inductor.
  • the control circuit can control the buck-boost unit to buck convert the reverse voltage.
  • the control circuit can control the first switch tube, the second switch tube and the third switch tube to keep off during the cycle time, and control the fourth switch tube to keep on during the fifth time period of the cycle time, so as to The first inductor is charged, and the fourth switch tube is controlled to keep off during the sixth period of the cycle time, so as to discharge the first inductor.
  • the buck-boost unit may perform buck conversion on the reverse voltage, and the obtained second output voltage may be any voltage not greater than 1/N of the second input voltage.
  • control circuit can first keep the first switch tube, the second switch tube and the third switch tube turned off within the cycle time, and adjust the duty cycle of the fourth switch tube, and the duty cycle of the fourth switch tube is the ratio of the fifth time period during which the fourth switch tube is turned on in the cycle time; when the second output voltage reaches the second target voltage, the control circuit maintains the current duty cycle of the fourth switch tube.
  • control circuit can determine the duty cycle of the fourth switch tube, so that the second output voltage can reach the second target voltage.
  • the control circuit can control the buck-boost unit to boost the reverse voltage.
  • the control circuit can control the first switch tube and the second switch tube to keep off during the cycle time, control the fourth switch tube to keep on during the cycle time, and control the third switch tube at the seventh time of the cycle time
  • the first inductor is kept on during the period to charge the first inductor
  • the third switch tube is controlled to remain off during the eighth period of the cycle time to discharge the first inductor.
  • the buck-boost unit may perform boost conversion on the reverse voltage, and the obtained second output voltage may be no less than 1/N of the second input voltage and no greater than any voltage of the second input voltage.
  • the control circuit can first keep the first switch tube and the second switch tube off, keep the fourth switch tube turned on, and adjust the duty cycle of the third switch tube, and the duty cycle of the third switch tube is The ratio of the seventh time period when the third switch tube is turned on in the cycle time; when the second output voltage reaches the second target voltage, the control circuit maintains the current duty cycle of the third switch tube.
  • the control circuit can determine the duty cycle of the third switch tube, so that the second output voltage can reach the second target voltage.
  • the present application provides an electric vehicle, which mainly includes a power battery and any voltage conversion device provided in the above-mentioned second aspect, and the voltage conversion device can charge the power battery.
  • 1 is a schematic diagram of an electric vehicle charging system
  • FIG. 3 is a schematic diagram of a control signal
  • 4a and 4b are schematic diagrams of the equivalent circuit structure of the conversion circuit
  • FIG. 6 is a schematic structural diagram of a conversion circuit
  • 7a and 7b are schematic diagrams of the equivalent circuit structure of the conversion circuit
  • FIG. 9 is a schematic structural diagram of a conversion circuit provided by an embodiment of the present application.
  • FIG. 10 is a schematic diagram of a control signal provided by an embodiment of the present application.
  • 11a and 11b are schematic diagrams of equivalent circuit structures of the conversion circuit provided by the embodiments of the present application.
  • FIG. 12 is a schematic diagram of a control signal provided by an embodiment of the present application.
  • FIG. 13a and 13b are schematic diagrams of the equivalent circuit structure of the conversion circuit provided by the embodiment of the present application.
  • FIG. 14 is a schematic structural diagram of a conversion circuit provided by an embodiment of the present application.
  • FIG. 15 is a schematic diagram of a control signal provided by an embodiment of the application.
  • FIG. 16a and FIG. 16b are schematic diagrams of the equivalent circuit structure of the conversion circuit provided by the embodiment of the application.
  • FIG. 17 is a schematic diagram of a control signal provided by an embodiment of the application.
  • FIG. 18a and FIG. 18b are schematic diagrams of the equivalent circuit structure of the conversion circuit provided by the embodiment of the present application.
  • 19 is a schematic flowchart of a method for determining the duty ratio of a switch tube provided by an embodiment of the present application.
  • 20 is a schematic diagram of a traditional boost circuit structure
  • FIG. 21 is one of the effect comparison diagrams provided by the embodiment of the application.
  • FIG. 22 is the second effect comparison diagram provided by the embodiment of the application.
  • FIG. 23 is the third effect comparison diagram provided by the embodiment of the present application.
  • connection may be understood as an electrical connection, and the connection of two electrical elements may be a direct or indirect connection between two electrical elements.
  • connection between A and B can be either a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components, such as the connection between A and B, or the direct connection between A and C, C and B are directly connected, and A and B are connected through C.
  • the switch tube in the embodiment of the present application may be integrated with a diode, and the switch tube in the embodiment of the present application may be a relay, a metal oxide semiconductor field effect transistor (metal oxide semiconductor field effect transistor, MOSFET), a bipolar One or more of various types of switching transistors such as bipolar junction transistor (BJT), insulated gate bipolar transistor (IGBT), silicon carbide (SiC) transistor, etc., implemented in this application
  • BJT bipolar junction transistor
  • IGBT insulated gate bipolar transistor
  • SiC silicon carbide
  • the package form of each switch tube may be a single-tube package or a multi-tube package, which is not limited in this embodiment of the present application.
  • Each switch tube may include a first electrode, a second electrode and a control electrode, wherein the control electrode is used to control the on or off of the switch tube.
  • the control electrode of the switch tube is the gate electrode
  • the first electrode of the switch tube may be the collector electrode of the switch tube
  • the second electrode may be the emitter electrode of the switch tube
  • the first electrode may be the emitter electrode of the switch tube.
  • the second electrode can be the collector of the switch tube.
  • Switched capacitor circuit also known as switched capacitor boost topology, has the advantages of high efficiency and small size, so it is widely used in various types of electronic equipment. For example, in an on-board charger of an electric vehicle, a switched capacitor circuit is often provided, and direct current/direct current (DC/DC) conversion can be realized through the switched capacitor circuit.
  • DC/DC direct current/direct current
  • FIG. 1 exemplarily shows a schematic diagram of an electric vehicle charging system.
  • the charging pile 20 can provide a charging voltage for the electric vehicle 10 , and in some scenarios, the charging voltage can be a DC voltage (not more than 500V in most cases).
  • the electric vehicle 10 can use the charging voltage provided by the charging pile 20 to charge the power battery 12 .
  • the charging voltage required by the power battery 12 is relatively high (mostly not less than 800V), and the charging voltage provided by some charging piles 20 cannot be Directly charge the power battery 12.
  • the electric vehicle 10 may further include a DC-DC booster (DCDC booster) 11, and the DCDC booster 11 can boost and convert the charging voltage, so that the charging voltage after voltage conversion can be adapted to the power battery 12, thereby The power battery 12 can be charged.
  • DCDC booster DC-DC booster
  • the DCDC booster11 includes an interface P1 and an interface P2, and the DCDC booster11 can be connected to the charging pile 20 through the interface P1 respectively, and to the power battery 12 through the interface P2.
  • the DCDC booster 11 may further include fast charging contactors K1 and K2 , a bypass contactor K3 , electromagnetic compatibility (Electromagnetic Compatibility, EMC) filter circuits 111 and 113 , and a conversion circuit 112 .
  • EMC Electromagnetic Compatibility
  • One end of the fast charging contactor K1 is connected to the high potential input end of the interface P1 , and the other end of the fast charging contactor K1 is connected to the high potential input end of the EMC filter circuit 111 .
  • One end of the fast charging contactor K2 is connected to the low potential input end of the interface P1 , and the other end of the fast charging contactor K2 is connected to the low potential input end of the EMC filter circuit 111 .
  • the fast-charging contactors K1 and K2 are turned on, so that a path is formed between the charger 20 and the DCDC booster 11 .
  • the fast charging contactors K1 and K2 are turned off to prevent the interface P1 from being charged, which is beneficial to protect the safety of users.
  • the high-potential output terminal of the EMC filter circuit 111 is connected to the high-potential input terminal of the conversion circuit 112
  • the low-potential output terminal of the EMC filter circuit 111 is connected to the low-potential input terminal of the conversion circuit 112 .
  • the EMC filter circuit 111 can filter the received charging voltage, and provide the filtered charging voltage to the conversion circuit 112 .
  • the conversion circuit 112 may be a DC/DC conversion circuit, and may perform boost conversion for the charging voltage. For example, if the charging voltage provided by the charging pile 20 is 500V, and the charging voltage adapted to the power battery 12 is 800V, the conversion circuit 112 can boost and convert the charging voltage of 500V to 800V.
  • the high-potential output terminal of the conversion circuit 112 is connected to the high-potential input terminal of the EMC filter circuit 113
  • the low-potential output terminal of the conversion circuit 112 is connected to the low-potential input terminal of the EMC filter circuit 113 .
  • the conversion circuit 112 can output the boosted and converted charging voltage to the EMC filter circuit 113 , so that the EMC filter circuit 113 can further filter the boosted and converted charging voltage.
  • the high-potential output terminal of the EMC filter circuit 113 is connected to the high-potential terminal of the interface P2 , and the high-potential terminal of the interface P2 can be connected to the positive electrode of the power battery 12 .
  • the low-potential output terminal of the EMC filter circuit 113 is connected to the low-potential terminal of the interface P2 , and the low-potential terminal of the interface P2 can be connected to the negative pole of the power battery 12 . Therefore, the EMC filter circuit 113 can provide the charging voltage after filtering and boost conversion to the power battery 12 through the interface P2, so that the power battery 12 can be charged.
  • the DCDC booster11 may also include a bypass contactor K3.
  • One end of the bypass contactor K3 is connected to the high potential input end of the conversion circuit 112 , and the other end of the bypass contactor K3 is connected to the low potential input end of the conversion circuit 112 .
  • the bypass contactor K3 can be kept on. In this case, the charging voltage provided by the charging pile 20 can be transmitted to the power battery 12 after being filtered by the EMC filter circuit 111 and the EMC filter circuit 113 , so as to directly charge the power battery 12 .
  • the bypass contactor K3 can be turned off. In this case, the charging voltage provided by the charging pile 20 needs to be converted by the conversion circuit 112 to adapt to the power battery 12 .
  • the DCDC booster 11 may further include a control circuit 114, and the control circuit 114 is connected to the conversion circuit 112, and can control the conversion circuit 112 to perform voltage conversion.
  • the receiving control module 102 may be a control component such as a processor, a microprocessor, and a controller in the electric vehicle 10, for example, a general-purpose central processing unit (CPU), a general-purpose processor, a digital signal processing (DSP) digital signal processing, DSP), application specific integrated circuits (ASIC), field programmable gate array (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof.
  • a control component such as a processor, a microprocessor, and a controller in the electric vehicle 10
  • CPU general-purpose central processing unit
  • DSP digital signal processing
  • ASIC application specific integrated circuits
  • FPGA field programmable gate array
  • the conversion circuit 112 is the basis for realizing the boost conversion function of the DCDC booster 11 .
  • the conversion circuit 112 will be further described.
  • FIG. 2 exemplarily shows a schematic structural diagram of a conversion circuit.
  • the conversion circuit 112 shown in FIG. 2 mainly includes an inductor Lr1 , switching transistors Q1 to Q4 , a capacitor C1 and a capacitor C2 .
  • the first electrode of the switch tube Q1 is used to connect to the high-potential output terminal o+ of the conversion circuit 112, and the second electrode of the switch tube Q1 is connected to the first electrode of the switch tube Q2.
  • the second electrode of the switch tube Q2 is connected to the first electrode of the switch tube Q3, the second electrode of the switch tube Q3 is connected to the first electrode of the switch tube Q4, and the second electrode of the switch tube Q4 is respectively connected to the low potential input of the conversion circuit 112. Terminal i- and low potential output terminal o- are connected.
  • One end of the capacitor C1 is connected to the first electrode of the switch Q2, and the other end of the capacitor C1 is connected to the second electrode of the switch Q3.
  • One end of the capacitor C2 is connected to the high-potential output terminal o+ of the conversion circuit 112 , and the other end of the capacitor C2 is connected to the low-potential output terminal o ⁇ of the conversion circuit 112 .
  • each capacitor in the embodiments of the present application may be capacitor types such as film capacitors, electrolytic capacitors, and ceramic capacitors, which are not limited in the embodiments of the present application.
  • One end of the inductor Lr1 is connected to the high-potential input end i+ of the conversion circuit 112 , and the other end of the inductor Lr1 is connected to the second electrode of the switching transistor Q2 .
  • the voltage between one end of the inductor Lr1 and the second electrode of the switching transistor Q4 can be understood as the input voltage Vin of the conversion circuit 112 .
  • control electrodes of the switching transistors Q1 to Q4 may be connected to the control circuit 114, so that the control circuit 114 can control the switching on and off of the switching transistors Q1 to Q4, respectively. It should be understood that, in order to simplify the illustration, this application This connection relationship is not shown in the drawings of the embodiment.
  • the control circuit 114 can respectively provide the control signals S1 to S4 shown in FIG. 3 for the switch transistors Q1 to the switch transistors Q4 .
  • the control circuit 114 may provide a control signal S1 for the switch Q1, a control signal S2 for the switch Q2, a control signal S3 for the switch Q3, and a control signal S4 for the switch Q4.
  • the control signals S1 to S4 can be as shown in FIG. 3 . It can be seen from FIG. 3 that the control signals S1 to S4 are all periodic signals, and the period is T.
  • the period T includes a time period t1 and a time period t2.
  • the control signals S1 and S3 are at a high level, and the control signals S2 and S4 are at a low level, so the switches Q1 and Q3 are turned on, and the switches Q2 and Q4 are turned off.
  • the equivalent circuit of the conversion circuit 112 may be as shown in FIG. 4a.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 112, and after the inductance Lr1, the switch Q2, the capacitor C1 and the switch Q4 are sequentially transmitted, the current is output from the low-potential input terminal i- of the conversion circuit 112.
  • the input voltage Vin charges the capacitor C1, so that the voltage of the capacitor C1 gradually reaches the input voltage Vin.
  • the equivalent circuit of the conversion circuit 112 may be as shown in FIG. 4b.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 112, and after the inductance Lr1, the switch Q3, the capacitor C1, the switch Q1 and the capacitor C2 are sequentially transmitted, the current is transmitted from the low-potential input terminal i of the conversion circuit 112. - output.
  • the input voltage Vin is connected in series with the capacitor C1 to charge the capacitor C2.
  • the output voltage Vout of the conversion circuit 112, that is, the voltage of the capacitor C2, is the sum of the input voltage Vin and the voltage of the capacitor C1. Since the voltage of the capacitor C1 reaches the input voltage Vin in the time period t1, the output voltage Vout of the conversion circuit 112 can reach 2Vin in the time period t2.
  • the inductor Lr1 can resonate with the capacitor C1.
  • the switching frequency Fsw of the switches Q1 to Q4 satisfies the following formula 1
  • the inductor Lr1 can make the switches Q2 and Q4 conduct to realize zero current switching (zero current switched, ZCS).
  • Lr1 represents the inductance of the inductor Lr
  • C1 represents the capacitance of the capacitor C1.
  • the conversion circuit 112 shown in FIG. 2 controls the charging and discharging of the capacitor through the switch tube, thereby realizing voltage conversion. Therefore, the conversion circuit 112 shown in FIG. 2 can also be called a switched capacitor circuit.
  • the inductance Lr1 is mainly used to make the switches Q2 and Q4 realize ZCS, and the inductance of the inductance Lr1 is small, and its influence on the voltage conversion can be ignored.
  • the transformation ratio of the switched capacitor circuit is mostly an integer, and the output voltage of the switched capacitor circuit cannot be adjusted continuously.
  • the switching frequency Fsw of the switching transistors Q1 to Q4 satisfies the following formula 2:
  • C2 in the formula 2 represents the capacitance of the capacitor C2.
  • the conversion circuit 112 may also be as shown in FIG. 6 .
  • the conversion circuit 112 includes switching transistors Q1 to Q4, a capacitor C2, a capacitor C3, an inductor Lr1 and a capacitor Cr1.
  • the connection relationship between the switching tubes Q1 to Q4 is similar to that in FIG. 2 , and details are not repeated here.
  • One end of the capacitor C2 is connected to the high potential output end o+ of the conversion circuit 112, and the other end of the capacitor C2 is connected to one end of the capacitor C3.
  • One end of the capacitor C3 is respectively connected to the first electrode of the switch tube Q3 and the high potential input terminal i+ of the conversion circuit 112, and the other end of the capacitor C3 is respectively connected to the second electrode of the switch tube Q4 and the low potential input terminal i- of the conversion circuit 112 connect.
  • One end of the inductor Lr1 is connected to the first electrode of the switch Q2, the other end of the inductor Lr1 is connected to one end of the capacitor Cr1, and the other end of the capacitor Cr1 is connected to the second electrode of the switch Q3.
  • the control signals shown in FIG. 3 can still be applied to the switches Q1 to Q4 .
  • the equivalent circuits of the conversion circuit 112 in the time period t1 and the time period t2 are respectively described.
  • the control signals S1 and S3 are at a high level, and the control signals S2 and S4 are at a low level, so the switches Q1 and Q3 are turned on, and the switches Q2 and Q4 are turned off.
  • the equivalent circuit of the conversion circuit 112 may be as shown in FIG. 7a.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 112 , and is transmitted from the low-potential input terminal i- of the conversion circuit 112 after being transmitted through the switch Q2 , the inductor Lr1 , the capacitor Cr1 and the switch Q4 . During this process, the capacitor Cr1 and the inductor Lr1 are charged. It can be considered that the sum of the voltage of the capacitor Cr1 and the voltage of the inductor Lr1 can reach the input voltage Vin.
  • the inductor Lr1 and the capacitor Cr1 resonate within the time period t1. That is to say, when the switching frequency Fsw of the switches Q1 to Q4 satisfies the following formula 3, the switches Q2 and Q4 can realize ZCS:
  • Cr1 represents the capacitance of the capacitor Cr1.
  • the control signals S1 and S3 are at a high level, and the control signals S2 and S4 are at a low level, so the switches Q1 and Q3 are turned on, and the switches Q2 and Q4 are turned off.
  • the equivalent circuit of the conversion circuit 112 may be as shown in FIG. 7b.
  • the current is output from the end of the capacitor Cr1 close to the inductor Lr1, and after being transmitted through the inductor Lr1, the switch Q1, the capacitor C2 and the switch Q3, it flows back to the end of the capacitor Cr1 close to the switch Q3.
  • the capacitor Cr1 and the inductor Lr1 are discharged so that the capacitor C2 can be charged. Since the sum of the voltages of the capacitor Cr1 and the inductor Lr1 can reach the input voltage Vin during the time period t1, the voltage of the capacitor C2 can reach the input voltage Vin during the time period t2.
  • the capacitors C2 and C3 are connected in series between the high-potential output terminal o+ and the low-potential output terminal o- of the conversion circuit 112, so the output voltage Vout is equal to the sum of the voltages of the capacitors C2 and C3.
  • the voltage across the capacitor C3 is the input voltage Vin.
  • the output voltage Vout of the conversion circuit 112 shown in FIG. 6 can reach 2Vin. That is, the conversion ratio of the conversion circuit shown in FIG. 6 is 2.
  • the inductor Lr1, the capacitor Cr1 and the capacitor C2 resonate within the time period t1. That is to say, when the switching frequency Fsw of the switches Q1 to Q4 satisfies the following formula 4, the switches Q1 and Q3 can realize ZCS:
  • the capacitance of the capacitor C2 is much larger than the capacitance of the capacitor Cr1, for example, the capacitance of the capacitor C2 may be 100 times the capacitance of the capacitor Cr1.
  • Fsw can be approximately equal to Approaching the Fsw shown in Equation 3. Therefore, when the switching frequency Fsw shown in Equation 3 is used, all the switches Q1 to Q4 in the switched capacitor shown in FIG. 6 can realize ZCS, which is beneficial to further improve the efficiency of the conversion circuit 112 .
  • the conversion circuit 112 shown in FIG. 2 and FIG. 6 has high efficiency, it is still a switched capacitor circuit in essence, and can only achieve an integer transformation ratio, and the transformation ratio of the transformation circuit 112 cannot be continuously adjusted.
  • a step-down (buck) circuit can also be integrated in the conversion circuit 112, as shown in FIG. 8 .
  • the conversion circuit 112 shown in FIG. 8 mainly includes a buck unit and a switched capacitor unit, wherein the buck unit adopts a buck circuit topology, and the switched capacitor unit adopts a switched capacitor circuit topology.
  • the output voltage of the buck unit is represented by the forward voltage.
  • the buck unit can step down the input voltage Vin to obtain the forward voltage.
  • the buck unit includes a capacitor C1, an inductor L1, a switch tube Q7 and a switch tube Q8.
  • One end of the inductor L1 is connected to the high potential input end i+ of the conversion circuit 112, and the other end of the inductor L1 is connected to the second electrode of the switch Q7 and the first electrode of the switch Q8, respectively.
  • the first electrode of the switch tube Q7 is connected to the high-potential output terminal o+ of the conversion circuit 112 .
  • the second electrode of the switch tube Q8 is connected to one end of the capacitor C3 in the switched capacitor unit.
  • One end of the capacitor C1 is connected to the high-potential input terminal i+ of the conversion circuit 112 , and the other end of the capacitor C1 is connected to the low-potential input terminal i- of the conversion circuit 112 and the low-potential output terminal o- of the conversion circuit 112 respectively.
  • the inductance L1 may be an inductance including a coil and a magnetic core with a strong energy storage capability.
  • the magnetic core of the inductor L1 may be a type of ferrite, an iron powder core, etc.
  • the coil may be a type such as a flat wire, a Litz wire, etc., which are not limited in the embodiments of the present application.
  • the conversion circuit 112 shown in FIG. 8 mainly has two switching states:
  • the current is input from the high-potential input terminal i+ of the conversion circuit 112, and then output from the high-potential output terminal o+ of the conversion circuit 112 after being transmitted through the inductor L1 and the switch Q7.
  • the returning current is input from the low-potential output terminal o- of the conversion circuit 112, and returns to the low-potential input terminal i- of the conversion circuit 112, thereby forming a charging loop of the inductor L1.
  • the inductor L1 is charged, and the output voltage Vout is the difference value obtained by subtracting the voltage of the inductor L1 from the input voltage Vin. That is to say, at this time, the voltage VL1 of the inductor L1 satisfies the following formula 5:
  • VL1 Vin-Vout (formula 5)
  • the voltage of the inductor L1 in the embodiment of the present application is the potential difference of the potential of one end of the inductor L1 connected to the high-potential input terminal i+ minus the potential of the other end of the inductor L1, which will not be repeated in the subsequent embodiments.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 112, transmitted through the inductor L1, the switch Q8 and the capacitor C3, and then returns to the low-potential input terminal i- of the conversion circuit 112, thereby forming a discharge loop of the inductor L1 .
  • the inductor L1 is discharged, and the voltage of the capacitor C3 is the difference value obtained by subtracting the voltage of the inductor L1 from the input voltage Vin.
  • VL1 Vin-Vout/2 (Formula 6)
  • the duty cycle D of the switch tube Q7 can be any value in [0, 1].
  • the output voltage Vout can be continuously changed between Vin and 2Vin.
  • the value of D is 0, that is, the switch Q7 is kept off during the cycle, and the switch Q8 is kept on during the cycle, and the output voltage Vout can reach 2Vin at this time.
  • the value of D is 1, that is, the switch tube Q7 is kept on during the cycle, and the switch tube Q8 is kept off during the cycle. At this time, the output voltage Vout can reach Vin.
  • the output voltage Vout of the conversion circuit 112 shown in FIG. 8 is still limited, and its maximum can only reach 2Vout, that is, the maximum transformation ratio of the conversion circuit 112 can only reach the transformation ratio of the switched capacitor unit.
  • an embodiment of the present application provides a conversion circuit, and the conversion circuit can be used as the conversion circuit 112 shown in FIG. 1 .
  • the maximum transformation ratio of the conversion circuit is not limited by the transformation ratio of the switched capacitor unit, and supports continuous adjustment of the transformation ratio of the transformation circuit.
  • the conversion circuit 90 mainly includes a buck-boost unit 91 and a switched capacitor unit 92 .
  • the high potential terminal of the buck-boost unit 91 and the high potential terminal of the switched capacitor unit 92 are both connected to the high potential output terminal o+ of the conversion circuit 90
  • the first intermediate terminal of the buck-boost unit 91 is connected to the second terminal of the switched capacitor unit 92 .
  • the two middle terminals are connected, and the low-potential terminal of the buck-boost unit 91 and the low-potential terminal of the switched capacitor unit 92 are both connected to the low-potential output terminal o- of the conversion circuit 90 .
  • the buck-boost unit 91 in the embodiment of the present application can perform buck conversion on the first input voltage, in the case where the buck-boost unit 91 performs buck conversion on the first input voltage, it can be seen from the above formula 7 that the first output The voltage Vout1 can reach any voltage between Vin1 and 2Vin1.
  • the buck-boost unit 91 can also perform boost conversion on the first input voltage, when the buck-boost unit 91 performs boost conversion on the first input voltage, the forward voltage can reach a value not less than Vin. After the switched capacitor unit 32 boosts the forward voltage, the first output voltage Vout1 can reach a value not less than 2Vin1.
  • the conversion circuit 90 provided by the embodiment of the present application can not only support continuous adjustment of the conversion ratio, but also the maximum conversion ratio of the conversion circuit 90 is no longer limited by the conversion ratio of the switched capacitor unit 92 . Therefore, the conversion circuit 90 provided by the embodiments of the present application has higher universality.
  • the second middle terminal and the low potential terminal of the switched capacitor unit 92 can be understood as the two ends of the switched capacitor unit 92 for receiving the forward voltage.
  • the circuit topology of the switched capacitor unit 92 may be the switched capacitor circuit topology shown in FIG. 2 and FIG. 6 .
  • the second intermediate terminal of the switched capacitor unit 92 can be understood as any connection point in the electrical connection between the capacitor C2 and the capacitor C3 .
  • the buck-boost unit 91 in the embodiment of the present application is further exemplified by the following embodiments.
  • the buck-boost unit 91 includes an inductor L1 , a diode D1 , a diode D2 , a switch transistor Q8 and a switch transistor Q9 .
  • One end of the inductor L1 is connected to the high potential input end i+ of the conversion circuit 90, and the other end of the inductor L1 is connected to the anode of the diode D1, the first electrode of the switch Q9 and the first electrode of the switch Q8, respectively.
  • the cathode of the diode D1 is connected to the high-potential output terminal o+ of the conversion circuit 90, and the second electrode of the switch Q8 is connected to the low-potential input terminal i- and the low-potential output terminal o- of the conversion circuit 90, respectively.
  • the second electrode of the switch tube Q9 is connected to the anode of the diode D2 , and the cathode of the diode D2 can be used as the first intermediate terminal of the buck-boost unit 91 to be connected to the second intermediate terminal of the switched capacitor unit 92 .
  • the buck-boost unit 91 in Fig. 9 can either perform buck conversion on the first input voltage V1, or perform boost conversion on the first input voltage V1, specifically:
  • the first output voltage Vout1 of the conversion circuit 90 may be any value between Vin1 and 2Vin1.
  • the switch Q8 and the switch Q9 are both turned on at a high level and turned off at a low level. Then, using the control signal shown in FIG. 10 , the buck-boost unit 91 can perform buck conversion on the first input voltage Vin1 .
  • the control signal S8 is used to control the turn-on and turn-off of the switch tube Q8, and the control signal S9 is used to control the turn-on and turn-off of the switch tube Q9.
  • the control signal S8 is at a low level, so the switch Q8 is kept off in the period T.
  • the control signal S9 is at a high level, so the switch tube Q9 is kept on during the period ta.
  • the control signal S9 is at a low level, so the switch Q9 remains off during the period tb.
  • the equivalent circuits of the buck-boost unit 91 in the time period ta and the time period tb are respectively described by taking a scenario where the transformation ratio of the switched capacitor unit 92 is 2 as an example. It should be pointed out that the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92 . Therefore, the following embodiments of the present application do not limit the switching state of the switched capacitor unit 92 .
  • the control signal S8 is at a low level, so the switch tube Q8 is turned off.
  • the control signal S9 is at a high level, so the switch transistor Q9 is turned on, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 11a.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 90, transmitted through the inductor L1, the switch tube Q9, the diode D2 and the capacitor C3, and then returned to the low-potential input terminal i- of the conversion circuit 90, thereby forming the charging loop of the inductor L1.
  • the control signal S8 is at a low level, so the switch tube Q8 is turned off.
  • the control signal S9 is at a low level, so the switch Q9 is turned off, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 11b.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 90 , and is output from the high-potential output terminal o+ of the conversion circuit 90 after being transmitted through the inductor L1 and the diode D1 .
  • the returning current is input from the low-potential output terminal o- of the conversion circuit 90, and returns to the low-potential input terminal i- of the conversion circuit 90, thereby forming a discharge loop of the inductance L1.
  • the duty cycle D1 of the switch tube Q9 can be any value in [0, 1].
  • the duty ratio D1 of the switch Q9 By adjusting the duty ratio D1 of the switch Q9, the first output voltage Vout1 can be continuously changed between Vin1 and 2Vin1.
  • the value of D1 is 0, that is, the switch Q9 is kept off during the period, and the first output voltage Vout1 can reach Vin1 at this time.
  • the value of D1 is 1, that is, the switch Q9 is kept on during the period, and the first output voltage Vout1 can reach 2Vin1 at this time.
  • the first output voltage Vout1 of the conversion circuit 90 may be any value not less than 2Vin1.
  • the switch Q8 and the switch Q9 are both turned on at a high level and turned off at a low level. Then, using the control signal shown in FIG. 12 , the buck-boost unit 91 can perform boost conversion on the first input voltage Vin1 .
  • the control signal S8 is used to control the turn-on and turn-off of the switch tube Q8, and the control signal S9 is used to control the turn-on and turn-off of the switch tube Q9.
  • the control signal S9 is at a high level in the period T, so the switch tube Q9 is kept on during the period T.
  • the control signal S8 is at a high level, so the switch tube Q8 is kept on during the period ta.
  • the control signal S8 is at a low level, so the switch Q8 is kept off during the period tb.
  • the equivalent circuits of the buck-boost unit 91 in the time period ta and the time period tb are respectively described by taking a scenario where the transformation ratio of the switched capacitor unit 92 is 2 as an example. It should be pointed out that the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92 . Therefore, the following embodiments of the present application do not limit the switching state of the switched capacitor unit 92 .
  • the control signal S9 is at a high level, so the switch tube Q9 is turned on.
  • the control signal S8 is at a high level, so the switch Q8 is turned on, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 13a.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 90, transmitted through the inductor L1 and the switch Q8, and returns to the low-potential input terminal i- of the conversion circuit 90, thereby forming a charging loop of the inductor L1.
  • the control signal S8 is at a low level, so the switch tube Q8 is turned off.
  • the control signal S9 is at a high level, so the switch transistor Q9 is turned on, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 13b.
  • the current is input from the high-potential input terminal i+ of the conversion circuit 90, transmitted through the inductor L1, the switch Q9, the diode D2 and the capacitor C3, and then returns to the low-potential input terminal i- of the conversion circuit 90, thereby forming a discharge loop of the inductor L1.
  • Vin1-VL1-VC3 0
  • the duty cycle D2 of the switch Q8 can be any value in [0, 1].
  • the first output voltage Vout1 can be continuously changed in the range of 2Vin ⁇ .
  • the value of D2 is 0, that is, the switch Q8 is kept off during the period, and the first output voltage Vout1 can reach 2Vin1 at this time.
  • the value of D2 is 1, that is, the switch Q8 is kept on during the period, and the first output voltage Vout1 can reach infinity at this time.
  • the first output voltage can reach infinity without considering the limitation of the energy storage capacity of the inductor L1.
  • the actual maximum value of the first output voltage Vout1 is also limited by factors such as the inductance of the inductor L1 .
  • the conversion circuit 90 may also receive the second input voltage Vin2 through the high-potential output terminal o+ and the low-potential output terminal o-.
  • the switched capacitor unit 92 can perform step-down conversion on the second input voltage Vin2 to obtain a reverse voltage. Assuming that the transformation ratio of the switched capacitor unit 92 is N, the reverse voltage can be Vin2/N.
  • the switched capacitor unit 92 can transmit the reverse voltage to the buck-boost unit 91 through the second middle terminal and the low potential terminal.
  • the buck-boost unit 91 performs buck-boost conversion on the reverse voltage, and uses the buck-boost converted reverse voltage as the second output voltage Vout2, which is output through the high-potential input terminal i+ and the low-potential input terminal i- of the conversion circuit 90 The second output voltage Vout2.
  • the buck-boost unit 91 may further include a switch transistor Q7 and a switch transistor Q10.
  • the switch tube Q7 includes the above-mentioned diode D1
  • the switch tube Q10 includes the above-mentioned diode D2.
  • the first electrode of the switch tube Q7 is connected to the high-potential output terminal o+ of the conversion circuit 90, and the second electrode of the switch tube Q7 is connected to the other end of the inductor L1.
  • the first electrode of the switch transistor Q10 is connected to the switched capacitor unit 92 as the first intermediate terminal of the buck-boost unit 91 , and the second electrode of the switch transistor Q10 is connected to the second electrode of the switch transistor Q9 .
  • the switch Q8 includes a diode D3, the anode of the diode D3 is connected to the low potential input terminal i- of the conversion circuit, and the cathode of the diode D3 is connected to the other end of the inductor L1 close to the switch Q9.
  • the switch tube Q9 includes a diode D4, the anode of the diode D4 is connected to the switch tube Q10, and the cathode of the diode D4 is connected to the inductor L1.
  • the switch transistor Q7 in order to prevent the switch transistor Q7 and the switch transistor Q10 from affecting the conversion of the first input voltage Vin1 to the first output voltage Vout1, the switch transistor Q7 can be maintained during the process of the transition from the first input voltage Vin1 to the first output voltage Vout1. And the switch tube Q10 is turned off.
  • the control signal S7 is a control signal for controlling the switch transistor Q7
  • the control signal S10 is a control signal for controlling the switch transistor Q10 .
  • FIG. 10 when the buck-boost unit performs buck conversion on the first input voltage Vin1, the control signals S7 and S10 are both at low level, and the switches Q7 and Q10 are kept off.
  • FIG. 12 when the buck-boost unit performs boost conversion on the first input voltage Vin1 , the control signals S7 and S10 are both at low level, and the switches Q7 and Q10 are kept off.
  • the conversion circuit 90 shown in FIG. 14 can perform step-down conversion of the second input voltage Vin2.
  • the buck-boost unit 91 can perform both buck conversion on the reverse voltage and boost conversion on the reverse voltage. Specifically:
  • the second output voltage Vout2 of the conversion circuit 90 may be any value between 0 and Vin2/2.
  • the switches Q7 to Q10 are all turned on at a high level and turned off at a low level. Then, using the control signal shown in FIG. 15 , the buck-boost unit 91 can perform buck conversion on the reverse voltage.
  • the control signals S7 , S8 and S9 are at low level, so the switches Q7 to Q9 are kept off in the period T.
  • the control signal S10 is at a high level, so the switch tube Q10 is kept on during the period ta.
  • the control signal S10 is at a low level, so the switch Q10 is kept off during the period tb.
  • the equivalent circuits of the buck-boost unit 91 in the time period ta and the time period tb are respectively described by taking a scenario where the transformation ratio of the switched capacitor unit 92 is 2 as an example. It should be pointed out that the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92 . Therefore, the following embodiments of the present application do not limit the switching state of the switched capacitor unit 92 .
  • the current is output from one end of the capacitor C3 close to the switch tube Q10, and is output from the high-potential input terminal i+ of the conversion circuit 90 after being transmitted through the switch tube Q10, the diode D4 in the switch tube Q9, and the inductor L1.
  • the returning current is input from the low-potential input terminal i- of the conversion circuit 90, and returns to the end of the capacitor C3 close to the low-potential input terminal i- of the conversion circuit 90, thereby forming a charging loop of the inductor L1.
  • the control signals S7 to S10 are all low level, so the switches Q7 to Q10 are all turned off, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 16b .
  • the current is output from the high-potential input terminal i+ of the conversion circuit 90, and the returning current is input from the low-potential input terminal i- of the conversion circuit 90, and returns to the end of the inductor L1 close to the switch Q8 through the diode D3, thereby forming the discharge of the inductor L1 loop.
  • the duty cycle D3 of the switch tube Q10 can be any value in [0, 1].
  • the second output voltage Vout2 can be continuously changed between 0 and Vin2/2.
  • the value of D3 is 0, that is, the switch Q10 is kept off during the period, and the second output voltage Vout2 can reach 0 at this time.
  • the value of D3 is 1, that is, the switch Q10 is kept on during the period, and at this time, the second output voltage Vout2 can reach Vin2/2.
  • the second output voltage Vout2 of the conversion circuit 90 may be any value between Vin2/2 and Vin2.
  • the switches Q7 to Q10 are all turned on at a high level and turned off at a low level. Then, using the control signal shown in FIG. 17 , the buck-boost unit 91 can be used to boost the reverse voltage.
  • the control signals S8 and S9 are at low level, so the switches Q8 and Q9 are kept off during the period T.
  • the control signal S10 is at a high level, so the switch tube Q10 remains on during the period T.
  • the control signal S7 is at a high level, so the switch tube Q7 is kept on during the period ta.
  • the control signal S7 is at a low level, so the switch Q7 remains off during the period tb.
  • the equivalent circuits of the buck-boost unit 91 in the time period ta and the time period tb are respectively described by taking a scenario where the transformation ratio of the switched capacitor unit 92 is 2 as an example. It should be pointed out that the switching state of the buck-boost unit 91 is not necessarily related to the switching state of the switched capacitor unit 92 . Therefore, the following embodiments of the present application do not limit the switching state of the switched capacitor unit 92 .
  • the switches Q8 and Q9 are turned off, the switches Q7 and Q10 are turned on, and the equivalent circuit of the conversion circuit 90 can be shown in FIG. 18a.
  • the current is input from the high-potential output terminal o+ of the conversion circuit 90 , and is output from the high-potential input terminal i+ of the conversion circuit 90 after being transmitted through the switch Q7 and the inductor L1 .
  • the returning current is input from the low-potential input terminal i- of the conversion circuit 90, and returns to the low-potential output terminal o- of the conversion circuit 90, thereby forming a charging loop of the inductance L1.
  • the control signals S7 to S9 are all low level, so the switches Q7 to Q9 are all turned off, and the control signal S10 is high level, so the switch transistor Q10 is turned on, and the conversion circuit 90
  • the equivalent circuit of can be shown in Figure 18b.
  • the current is output from one end of the capacitor C3 close to the switch tube Q10, and is output from the high-potential input terminal i+ of the conversion circuit 90 after being transmitted through the inductor L1, and the returning current is input from the low-potential input terminal i- of the conversion circuit 90, and returns to the capacitor C3
  • One end close to the low-potential input terminal i- of the conversion circuit 90 forms a discharge loop of the inductance L1.
  • Vout2-VL1-VC3 0.
  • the duty cycle D4 of the switch tube Q7 can be any value in [0, 1].
  • the duty ratio D4 of the switch Q7 By adjusting the duty ratio D4 of the switch Q7, the second output voltage Vout2 can be continuously changed between Vin2/2 and Vin2.
  • the value of D4 is 0, that is, the switch Q7 is kept off during the period, and at this time, the second output voltage Vout2 can reach Vin2/2.
  • the value of D4 is 1, that is, the switch Q7 is kept on during the period, and the second output voltage Vout2 can reach Vin2 at this time.
  • the conversion circuit 90 provided by the embodiment of the present application can convert the first input voltage Vin1 to Vin1 to infinity.
  • the control circuit 114 can use the method shown in FIG. 19 to determine the duty cycle of the switch transistor Q8 or the switch transistor Q9 so that the first output voltage Vin1 can reach the first target voltage output by the conversion circuit 90 . Specifically, it mainly includes the following steps:
  • the voltage conversion device is powered on.
  • the voltage conversion device may be the DCDC booster 11 shown in FIG. 1 .
  • the high-potential input terminal i+ and the low-potential input terminal i- of the conversion circuit 90 can receive the first input voltage Vin1.
  • the control circuit 114 controls the switching transistors Q1 to Q4 in the switched capacitor unit 92 to be turned on and off, so that the voltages of the capacitors C2 and C3 are balanced, that is, the voltages of the two are equal.
  • the control circuit 114 keeps the switches Q7, Q8 and Q10 off, and adjusts the duty cycle D1 of the switch Q9.
  • the control circuit 114 may adjust the duty cycle D1 of the switch transistor Q9 in a manner that the duty cycle D1 of the switch transistor Q9 gradually increases from 0 to 1.
  • the state of the conversion circuit 90 is incorrect.
  • the control circuit 114 may report the error. For example, if the first target voltage is less than Vin1, the conversion circuit 90 cannot output the first output voltage that meets the first target voltage, and a state error may occur at this time.
  • the control circuit 114 can also keep the switches Q7 to Q9 off first, and adjust the duty cycle D3 of the switch Q10 .
  • the control circuit 114 can maintain the current duty cycle D3 of the switching transistor Q10. If the duty cycle D3 is adjusted within [0, 1] and the second output voltage cannot reach the second target voltage, the control circuit 114 can keep the switches Q8 and Q9 off, keep the switch Q10 on, and adjust the switch Duty cycle D4 of tube Q7.
  • the control circuit 114 can maintain the current duty cycle D4 of the switch transistor Q7. If the duty ratio D4 is adjusted within [0, 1] and the second output voltage cannot reach the second target voltage, it means that the state of the conversion circuit 90 is wrong. The control circuit 114 may report the error.
  • the embodiment of the present application provides a conversion circuit 90 .
  • the conversion circuit 90 includes a buck-boost unit 91 and a switched capacitor unit, and the transformation ratio of the conversion circuit 90 is not limited by the switched capacitor unit.
  • the switched capacitor unit 92 has a boosting function in the embodiment of the present application, the requirement for the boosting capability of the buck-boost unit 91 is lower, and the inductor L1 can be implemented by an inductor with a smaller inductance.
  • the greater the inductance of the inductor the greater the loss and volume. Therefore, compared with the traditional boost circuit, the conversion circuit 90 provided by the embodiment of the present application is beneficial to improve the efficiency and reduce the volume.
  • the traditional boost circuit mainly includes an inductor and two switches.
  • the first input voltage Vin1 of the conversion circuit 90 and the input voltage of the conventional boost circuit are both 300-500V; the first output voltage Vout1 of the conversion circuit 90 and the output voltage of the conventional boost circuit are both 600-850V ;
  • the power of the conversion circuit 90 and the power of the conventional boost circuit are both 12.5kw.
  • Table 1 The design parameters of the conversion circuit 90 and the traditional boost circuit are shown in Table 1 below:
  • each switch tube in the conversion circuit 90 adopts an IGBT with a withstand voltage of 650V and a maximum current of 75A, the inductance of the inductor L1 is 100uH, and the switching frequency is 20kHz.
  • Each switch tube in the traditional boost circuit adopts IGBT with a withstand voltage of 1200V and a maximum current of 75A, the inductance of the inductor is 500uH, and the switching frequency is 15kHz.
  • the volume of the conventional boost circuit is close to that of the conversion circuit 90 provided by the embodiment of the present application.
  • the weight of the conversion circuit 90 provided by the embodiment of the present application is much smaller than that of the conventional boost circuit. This is mainly because the buck-boost unit 91 of the present application can use a smaller inductance, which can reduce the Inductor weight.
  • the efficiency of the conventional boost circuit is about 97.5%, while the efficiency of the conversion circuit 90 provided by the embodiment of the present application can be as high as 98.5%, and the efficiency of the conversion circuit 90 is significantly improved.
  • an embodiment of the present application further provides a voltage conversion device, and the voltage conversion device may include the conversion circuit 90 provided by any of the above embodiments of the present application.
  • the voltage conversion device can be used as the DCDC booster 11 in the electric vehicle 10 .
  • the conversion circuit 90 can be used as the conversion circuit 112 in the DCDC booster 11, and the control circuit 114 is connected to the control electrodes of the respective switch tubes in the buck-boost unit 91 and the switched capacitor unit 92, so that the conversion circuit 90 can be controlled to realize the voltage convert.
  • the embodiments of the present application also provide an electric vehicle, which may be as shown in FIG. 1 .
  • the electric vehicle 10 includes a DCDC booster 11 , and the DCDC booster 11 is connected to the power battery and can charge the power battery 12 .
  • the conversion circuit 112 may be implemented by using the conversion circuit 90 provided by the embodiment of the present application.

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Abstract

本申请公开了一种转换电路、电压转换装置及电动汽车，该转换电路包括buck-boost单元和开关电容单元。buck-boost单元可以对接收到的第一输入电压进行buck转换或boost转换，并将buck转换或boost转换后的第一输入电压作为正向电压提供给开关电容单元。开关电容单元可以对正向电压进行升压转换，并将升压转换后的正向电压作为第一输出电压输出。该转换电路不仅可以支持变比连续可调，且转换电路的最大变比不再受限于开关电容单元的变比，转换电路的第一输出电压可以是不小于第一输入电压的任一电压。

Description

一种转换电路、电压转换装置及电动汽车 技术领域
本申请涉及新能源汽车技术领域，尤其涉及一种转换电路、电压转换装置及电动汽车。
背景技术
开关电容电路，又可以称为开关电容升压拓扑，具有效率高、体积小等优点，因此被广泛应用在多种类型的电子设备中。开关电容电路主要包括多个转换开关管和多个转换电容，通过该多个转换开关管，可以控制该多个转换电容周期性地充电和放电，从而实现升压转换。
其中，开关电容电路的输出电压与输入电压之间的比值，可以称为开关电容电路的变比。一般来说，开关电容电路所能实现的变比多为整数，虽然在目前的一些转换电路中，可以同时集成buck电路和开关电容电路，使转换电路能够实现连续变比。但此类转换电路所能实现的最大变比也多受到开关电容电路的变比限制。
因此，目前集成有开关电容电路的转换电路还有待进一步研究。
发明内容
本申请提供一种转换电路、电压转换装置及电动汽车，该转换电路可以支持连续调节变比，且相较于开关电容电路，该转换电路能够实现更高的变比。
第一方面，本申请提供一种转换电路，其主要包括降压-升压buck-boost单元和开关电容单元。其中，buck-boost单元的高电势端和开关电容单元的高电势端皆与转换电路的高电势输出端连接，buck-boost单元的第一中间端与开关电容单元的第二中间端连接，buck-boost单元的低电势端和开关电容单元的低电势端皆与转换电路的低电势输出端连接。buck-boost单元可以接收第一输入电压，对第一输入电压进行buck转换或boost转换，并将buck转换或boost转换后的第一输入电压作为正向电压，通过第一中间端将正向电压提供给开关电容单元。开关电容单元可以对正向电压进行升压转换。转换电路的高电势输出端和低电势输出端则可以输出第一输出电压，该第一输出电压为升压转换后的正向电压。
具体来说，buck-boost单元既可以对第一输入电压进行buck转换，又可以对第一输入电压进行boost转换。在buck-boost单元对第一输入电压进行buck转换的情况下，正向电压可以是不小于第一输入电压的1/N，且不大于第一输入电压的任一电压。其中，N表示开关电容单元的变比，N为大于或等于1的整数。在此情况下，开关电容单元对正向电压进行升压转换，使得升压转换后的正向电压(也就是第一输出电压)可以达到第一输入电压至N倍的第一输入电压之间的任一电压。
在buck-boost单元对第一输入电压进行boost转换的情况下，正向电压可以是不小于第一输入电压的任一电压。在此情况下，开关电容单元对正向电压进行升压转换，使得升压转换后的正向电压(也就是第一输出电压)可以达到不小于N倍的第一输入电压的任一电压。
因此，本申请所提供的转换电路不仅可以支持变比连续可调，且转换电路的最大变比不再受限于开关电容单元的变比，转换电路的第一输出电压可以是不小于第一输入电压的 任一电压，有利于提高转换电路的普适性。
示例性的，buck-boost单元包括第一二极管、第二二极管、第一开关管、第二开关管和第一电感。其中，第一电感的一端与转换电路的高电势输入端连接，第一电感的另一端分别与第一二极管的阳极、第一开关管的第一电极和第二开关管的第一电极连接。第一二极管的阴极与转换电路的高电势输出端连接，第一开关管的第二电极与第二二极管的阳极连接，第二二极管的阴极与开关电容单元的第二中间端连接。第二开关管的第二电极分别与转换电路的低电势输入端和低电势输出端连接，转换电路的高电势输入端和低电势输入端用于接收第一输入电压。
如前所述，buck-boost单元可以对第一输入电压进行buck转换。具体来说，第一开关管可以在周期时间内保持关断；第二开关管可以在周期时间的第一时间段内保持导通，以使第一电感充电。第二开关管在周期时间的第二时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对第一输入电压进行buck转换，所得到的第一输出电压可以是不小于第一输入电压，且不大于第一输入电压的N倍的任一电压。
如前所述，buck-boost单元可以对第一输入电压进行boost转换。具体来说，第二开关管可以在周期时间内保持导通。第一开关管可以在周期时间的第一时间段内保持导通，以使电感充电。第二开关管在周期时间的第二时间段内保持关断，以使电感放电。在此情况下，buck-boost单元可以对第一输入电压进行boost转换，所得到的第一输出电压可以是不小于第一输入电压的N倍的任一电压。
在一种可能的实现方式中，本申请所提供的转换电路还支持双向电压变换，也就是说，该转换电路不仅可以通过高电势输入端和低电势输入端接收第一输入电压，并通过高电势输出端和低电势输出端输出第一输出电压，该转换电路的高电势输出端和低电势输出端还可以接收第二输入电压，该转换电路的高电势输入端和低电势输入端还可以输出第二输出电压。在此情况下，开关电容单元还可以对第二输入电压进行降压转换，并将降压转换后的第二输入电压作为逆向电压，通过第二中间端将逆向电压提供给buck-boost单元。buck-boost单元则可以对上述逆向电压进行buck转换或boost转换，并将buck转换或boost转换后的逆向电压作为第二输出电压，通过转换电路的高电势输入端和低电势输入端输出第二输出电压。
具体来说，开关电容单元提供给buck-boost单元的逆向电压可以是第二输入电压的1/N。buck-boost单元既可以对逆向电压进行buck转换，又可以对逆向电压进行boost转换。在buck-boost单元对逆向电压进行buck转换时，第二输出电压可以是不大于逆向电压的任一电压，即第二输出电压可以是不大于第二输入电压的1/N的任一电压。在buck-boost单元对逆向电压进行boost转换时，第二输出电压可以是不小于逆向电压，且不大于逆向电压的N倍的任一电压，即第二输出电压可以是不小于第二输入电压的1/N，且不大于第二输入电压的任一电压。
示例性的，buck-boost单元还可以包括第三开关管和第四开关管，该第三开关管包括上述第一二极管，该第四开关管包括上述第二二极管。其中，第三开关管的第一电极与转换电路的高电势输出端连接，第三开关管的第二电极与第一电感的另一端连接。第四开关管的第一电极与第二开关管的第二电极连接，第四开关管的第二电极与开关电容单元的第二中间端连接。
为了使第一开关管和第二开关管不影响buck-boost单元对逆向电压的转换，在一种可 能的实现方式中，第一开关管包括第三二极管，第三二极管的阳极与第四开关管的第一电极连接，第三二极管的阴极与第一电感的另一端连接。第二开关管包括第四二极管，第四二极管的阳极分别与转换电路的低电势输入端和低电势输出端连接，第四二极管的阴极与第一电感的另一端连接。在此情况下，在buck-boost单元对逆向电压进行转换时可以关断第一开关管和第二开关管，第一开关管和第二开关管中的二极管可以保持buck-boost单元中第一电感的充电回路和放电回路导通，从而可以降低第一开关管和第二开关管对逆向电压的转换过程的影响。
如前所述，buck-boost单元可以对逆向电压进行buck转换。具体来说，第一开关管、第二开关管和第三开关管可以在周期时间内保持关断。第四开关管可以在周期时间的第一时间段内保持导通，以使第一电感充电。第四开关管可以在周期时间的第二时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对逆向电压进行buck转换，所得到的第二输出电压可以是不大于第二输入电压的1/N的任一电压。
如前所述，buck-boost单元可以对逆向电压进行boost转换。具体来说，第一开关管和第二开关管可以在周期时间内保持关断。第四开关管可以在周期时间内保持导通。第三开关管可以在周期时间的第一时间段内保持导通，以使第一电感充电。第三开关管可以在周期时间的第二时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对逆向电压进行boost转换，所得到的第二输出电压可以是不小于第二输入电压的1/N，且不大于第二输入电压的任一电压。
第二方面，本申请提供一种电压转换装置，其主要包括转换电路和控制电路。该转换电路可以是上述第一方面中提供的任一种转换电路，第二方面中相应方案的技术效果可以参照第一方面中对应方案可以得到的技术效果，重复之处不予详述。
示例性的，转换电路可以包括降压-升压buck-boost单元和开关电容单元。其中，buck-boost单元的高电势端和开关电容单元的高电势端皆与转换电路的高电势输出端连接，buck-boost单元的第一中间端与开关电容单元的第二中间端连接，buck-boost单元的低电势端和开关电容单元的低电势端皆与转换电路的低电势输出端连接。控制电路可以控制buck-boost单元对接收到的第一输入电压进行buck转换或boost转换，并将buck转换或boost转换后的第一输入电压作为正向电压，通过第一中间端将正向电压提供给开关电容单元。控制电路控制开关电容单元对正向电压进行升压转换，其中，转换电路的高电势输出端和低电势输出端可以输出第一输出电压，该第一输出电压可以是升压转换后的正向电压。
示例性的，buck-boost单元可以包括第一二极管、第二二极管、第一开关管、第二开关管和第一电感。其中，第一电感的一端与转换电路的高电势输入端连接，第一电感的另一端分别与第一二极管的阳极、第一开关管的第一电极和第二开关管的第一电极连接。第一二极管的阴极与转换电路的高电势输出端连接，第一开关管的第二电极与第二二极管的阳极连接，第二二极管的阴极与开关电容单元的第二中间端连接。第二开关管的第二电极分别与转换电路的低电势输入端和低电势输出端连接，转换电路的高电势输入端和低电势输入端用于接收第一输入电压。
如前所述，控制电路可以控制buck-boost单元对第一输入电压进行buck转换。具体来说，控制电路可以控制第一开关管在周期时间内保持关断，控制第二开关管在周期时间的第一时间段内保持导通，以使第一电感充电，控制第二开关管在周期时间的第二时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对第一输入电压进行buck 转换，所得到的第一输出电压可以是不小于第一输入电压，且不大于第一输入电压的N倍的任一电压。
在本申请中，控制电路可以先保持第一开关管关断，调节第二开关管的占空比，第二开关管的占空比为第二开关管导通的第一时间段在周期时间的占比。在第一输出电压达到第一目标电压时，控制电路保持第二开关管当前的占空比。采用该实现方式，控制电路可以确定第二开关管的占空比，使第一输出电压可以达到第一目标电压。
如前所述，控制电路可以控制buck-boost单元对第一输入电压进行boost转换。具体来说，控制电路可以控制第二开关管在周期时间内保持导通，控制第一开关管在周期时间的第三时间段内保持导通，以使电感充电，控制第一开关管在周期时间的第四时间段内保持关断，以使电感放电。在此情况下，buck-boost单元可以对第一输入电压进行boost转换，所得到的第一输出电压可以是不小于第一输入电压的N倍的任一电压。
在本申请中，控制电路可以先保持第二开关管导通，并调节第一开关管的占空比，第一开关管的占空比为第一开关管导通的第三时间段在周期时间的占比。在第一输出电压达到第一目标电压时，控制电路保持第一开关管当前的占空比。采用该实现方式，控制电路可以确定第一开关管的占空比，使第一输出电压可以达到第一目标电压。
在一种可能的实现方式中，本申请所提供的电压转换装置还支持双向电压变换，也就是说，转换电路的高电势输出端和低电势输出端还可以接收第二输入电压，转换电路的高电势输入端和低电势输入端还可以输出第二输出电压。控制电路还可以控制开关电容单元对第二输入电压进行降压转换，并将降压转换后的第二输入电压作为逆向电压，通过第二中间端将逆向电压提供给buck-boost单元；控制电路控制buck-boost单元对逆向电压进行buck转换或boost转换，并将buck转换或boost转换后的逆向电压作为第二输出电压，通过转换电路的高电势输入端和低电势输入端输出第二输出电压。
示例性的，buck-boost单元还可以包括第三开关管和第四开关管，该第三开关管包括第一二极管，第四开关管包括第二二极管。其中，第三开关管的第一电极与转换电路的高电势输出端连接，第三开关管的第二电极与第一电感的另一端连接。第四开关管的第一电极与第二开关管的第二电极连接，第四开关管的第二电极与开关电容单元的第二中间端连接。
为了使第一开关管和第二开关管不影响buck-boost单元对逆向电压的转换，在一种可能的实现方式中，第一开关管包括第三二极管，第三二极管的阳极与第四开关管的第一电极连接，第三二极管的阴极与第一电感的另一端连接。第二开关管包括第四二极管，第四二极管的阳极分别与转换电路的低电势输入端和低电势输出端连接，第四二极管的阴极与第一电感的另一端连接。
如前所述，控制电路可以控制buck-boost单元对逆向电压进行buck转换。具体来说，控制电路可以控制第一开关管、第二开关管和第三开关管用于在周期时间内保持关断，控制第四开关管在周期时间的第五时间段内保持导通，以使第一电感充电，控制第四开关管在周期时间的第六时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对逆向电压进行buck转换，所得到的第二输出电压可以是不大于第二输入电压的1/N的任一电压。
在本申请中，控制电路可以先保持第一开关管、第二开关管和第三开关管在周期时间内关断，并调节第四开关管的占空比，第四开关管的占空比为第四开关管导通的第五时间 段在周期时间的占比；在第二输出电压达到第二目标电压时，控制电路保持第四开关管当前的占空比。采用该实现方式，控制电路可以确定第四开关管的占空比，使第二输出电压可以达到第二目标电压。
如前所述，控制电路可以控制buck-boost单元对逆向电压进行boost转换。具体来说，控制电路可以控制第一开关管和第二开关管在周期时间内保持关断，控制第四开关管在周期时间内保持导通，控制第三开关管在周期时间的第七时间段内保持导通，以使第一电感充电，控制第三开关管在周期时间的第八时间段内保持关断，以使第一电感放电。在此情况下，buck-boost单元可以对逆向电压进行boost转换，所得到的第二输出电压可以是不小于第二输入电压的1/N，且不大于第二输入电压的任一电压。
在本申请中，控制电路可以先保持第一开关管和第二开关管关断，保持第四开关管导通，并调节第三开关管的占空比，第三开关管的占空比为第三开关管导通的第七时间段在周期时间的占比；在第二输出电压达到第二目标电压时，控制电路保持第三开关管当前的占空比。采用该实现方式，控制电路可以确定第三开关管的占空比，使第二输出电压可以达到第二目标电压。
第三方面，本申请提供一种电动汽车，其主要包括动力电池和如上述第二方面提供任一种电压转换装置，该电压转换装置可以为动力电池充电。
本申请的这些方面或其它方面在以下实施例的描述中会更加简明易懂。
附图说明
图1为一种电动汽车充电系统示意图；
图2为一种转换电路结构示意图；
图3为一种控制信号示意图；
图4a和图4b为转换电路的等效电路结构示意图；
图5为一种转换电路结构示意图；
图6为一种转换电路结构示意图；
图7a和图7b为转换电路的等效电路结构示意图；
图8为一种转换电路结构示意图；
图9为本申请实施例提供的一种转换电路结构示意图；
图10为本申请实施例提供的一种控制信号示意图；
图11a和图11b为本申请实施例提供的转换电路的等效电路结构示意图；
图12为本申请实施例提供的一种控制信号示意图；
图13a和图13b为本申请实施例提供的转换电路的等效电路结构示意图；
图14为本申请实施例提供的一种转换电路结构示意图；
图15为本申请实施例提供的一种控制信号示意图；
图16a和图16b为本申请实施例提供的转换电路的等效电路结构示意图；
图17为本申请实施例提供的一种控制信号示意图；
图18a和图18b为本申请实施例提供的转换电路的等效电路结构示意图；
图19为本申请实施例提供的一种确定开关管占空比的方法流程示意图；
图20为一种传统的boost电路结构示意图；
图21为本申请实施例提供的效果对比图之一；
图22为本申请实施例提供的效果对比图之二；
图23为本申请实施例提供的效果对比图之三。
具体实施方式
为了使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请作进一步地详细描述。方法实施例中的具体操作方法也可以应用于装置实施例或系统实施例中。需要说明的是，在本申请的描述中“至少一个”是指一个或多个，其中，多个是指两个或两个以上。鉴于此，本发明实施例中也可以将“多个”理解为“至少两个”。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，字符“/”，如无特殊说明，一般表示前后关联对象是一种“或”的关系。另外，需要理解的是，在本申请的描述中，“第一”、“第二”等词汇，仅用于区分描述的目的，而不能理解为指示或暗示相对重要性，也不能理解为指示或暗示顺序。
需要指出的是，本申请实施例中“连接”可以理解为电连接，两个电学元件连接可以是两个电学元件之间的直接或间接连接。例如，A与B连接，既可以是A与B直接连接，也可以是A与B之间通过一个或多个其它电学元件间接连接，例如A与B连接，也可以是A与C直接连接，C与B直接连接，A与B之间通过C实现了连接。
需要指出的是，本申请实施例中的开关管可以集成有二极管，本申请实施例中的开关管可以是继电器、金属氧化物半导体场效应晶体管(metal oxide semiconductor field effect transistor，MOSFET)，双极结型管(bipolar junction transistor，BJT)，绝缘栅双极型晶体管(insulated gate bipolar transistor，IGBT)、碳化硅(SiC)晶体管等多种类型的开关管中的一种或多种，本申请实施例对此不再一一列举。各个开关管的封装形式可以是单管封装，也可以是多管封装，本申请实施例对此并不多作限制。每个开关管皆可以包括第一电极、第二电极和控制电极，其中，控制电极用于控制开关管的导通或断开。当开关管导通时，开关管的第一电极和第二电极之间可以传输电流，当开关管断开时，开关管的第一电极和第二电极之间无法传输电流。以IGBT为例，开关管的控制电极为门极，开关管的第一电极可以是开关管的集电极，第二电极可以是开关管的发射极，或者，第一电极可以是开关管的发射极，第二电极可以是开关管的集电极。下面将结合附图，对本申请实施例进行详细描述。
开关电容电路，又可以称为开关电容升压拓扑，具有效率高、体积小等优点，因此被广泛应用在多种类型的电子设备中。例如，在电动汽车的车载充电器中，便往往设置有开关电容电路，通过开关电容电路可以实现直流-直流(direct current/direct current，DC/DC)转换。
以电动汽车为例，图1示例性示出了一种电动汽车充电系统示意图。如图1所示，充电桩20可以为电动汽车10提供充电电压，在一些场景下，该充电电压可以为直流电压(多不大于500V)。电动汽车10可以利用充电桩20提供的充电电压为动力电池12充电。
目前，越来越多的电动汽车10采用了高压动力电池包，也就是说，动力电池12所需的充电电压取值较高(多不小于800V)，部分充电桩20所提供的充电电压无法直接为动力电池12充电。
有鉴于此，电动汽车10还可以包括直流直流升压器(DCDC booster)11，DCDC  booster11可以对充电电压进行升压转换，使经过电压转换后的充电电压可以与动力电池12相适配，从而可以为动力电池12充电。
具体来说，DCDC booster11包括接口P1和接口P2，DCDC booster11可以分别通过接口P1与充电桩20连接，通过接口P2与动力电池12连接。DCDC booster11中还可以包括快充接触器K1和K2、旁路接触器(bypass contactor)K3、电磁兼容(Electromagnetic Compatibility，EMC)滤波电路111和113，以及转换电路112。
其中，快充接触器K1的一端与接口P1的高电势输入端连接，快充接触器K1的另一端与EMC滤波电路111的高电势输入端连接。快充接触器K2的一端与接口P1的低电势输入端连接，快充接触器K2的另一端与EMC滤波电路111的低电势输入端连接。
在电动汽车10充电时，快充接触器K1和K2导通，使充电器20与DCDC booster11之间构成通路。在电动汽车10停止充电时，快充接触器K1和K2关断，防止接口P1带电，有利于保护用户安全。
EMC滤波电路111的高电势输出端与转换电路112的高电势输入端连接，EMC滤波电路111的低电势输出端与转换电路112的低电势输入端连接。EMC滤波电路111可以对接收到的充电电压进行滤波，并将滤波后的充电电压提供给转换电路112。
转换电路112可以是DC/DC转换电路，可以对充电电压进行升压转换。例如，充电桩20提供的充电电压为500V，而动力电池12适配的充电电压为800V，则转换电路112可以将500V的充电电压升压转换至800V。
转换电路112的高电势输出端与EMC滤波电路113的高电势输入端连接，转换电路112的低电势输出端与EMC滤波电路113的低电势输入端连接。转换电路112可以将升压转换后的充电电压输出给EMC滤波电路113，使得EMC滤波电路113可以对升压转换后的充电电压作进一步滤波。
在电动汽车10中，EMC滤波电路113的高电势输出端与接口P2的高电势端连接，该接口P2的高电势端可以连接动力电池12的正极。EMC滤波电路113的低电势输出端与接口P2的低电势端连接，该接口P2的低电势端可以连接动力电池12的负极。因此，EMC滤波电路113可以通过接口P2，将经过滤波和升压转换后的充电电压提供给动力电池12，从而可以为动力电池12充电。
如图1所示，DCDC booster11中还可以包括旁路接触器K3。旁路接触器K3的一端与转换电路112的高电势输入端连接，旁路接触器K3的另一端与转换电路112的低电势输入端连接。在充电桩20提供的充电电压可以适配动力电池12时，可以保持旁路接触器K3导通。在此情况下，充电桩20提供的充电电压经EMC滤波电路111和EMC滤波电路113滤波后，便可以传输至动力电池12，从而直接为动力电池12充电。在充电桩20提供的充电电压无法适配动力电池12时，则可以关断旁路接触器K3。此情况下，充电桩20提供的充电电压便需要经过转换电路112进行电压转换，以适配动力电池12。
由图1可见，DCDC booster11还可以包括控制电路114，控制电路114与转换电路112连接，可以控制转换电路112进行电压转换。示例性的，接收控制模块102可以是电动汽车10中处理器、微处理器、控制器等控制组件，例如可以是通用中央处理器(central processing unit，CPU)，通用处理器，数字信号处理(digital signal processing，DSP)，专用集成电路(application specific integrated circuits，ASIC)，现场可编程门阵列(field programmable gate array，FPGA)或者其他可编程逻辑器件、晶体管逻辑器件、硬件部件 或者其任意组合。
由上述内容可见，转换电路112是实现DCDC booster11的升压转换功能的基础。接下来，对转换电路112作进一步说明。
图2示例性示出了一种转换电路结构示意图。图2所示的转换电路112主要包括电感Lr1、开关管Q1至Q4，电容C1和电容C2。其中，开关管Q1的第一电极用于连接转换电路112的高电势输出端o+，开关管Q1的第二电极与开关管Q2的第一电极连接。开关管Q2的第二电极与开关管Q3的第一电极连接，开关管Q3的第二电极与开关管Q4的第一电极连接，开关管Q4的第二电极分别与转换电路112的低电势输入端i-和低电势输出端o-连接。
电容C1的一端与开关管Q2的第一电极连接，电容C1的另一端与开关管Q3的第二电极连接。电容C2的一端与转换电路112的高电势输出端o+连接，电容C2的另一端与转换电路112的低电势输出端o-连接。
示例性的，本申请实施例中的各个电容可以是薄膜电容、电解电容、陶瓷电容等电容类型，本申请实施例对此并不多作限制。
电感Lr1的一端与转换电路112的高电势输入端i+连接，电感Lr1的另一端与开关管Q2的第二电极连接。其中，电感Lr1的一端与开关管Q4的第二电极之间的电压，可以理解为转换电路112的输入电压Vin。
在本申请实施例中，开关管Q1至Q4的控制电极可以与控制电路114连接，使得控制电路114可以分别控制开关管Q1至Q4的导通和关断，应理解，为了简化示意，本申请实施例的附图中未示出该连接关系。
基于图2所示的转换电路112，控制电路114可以分别为开关管Q1至开关管Q4提供如图3所示的控制信号S1至控制信号S4。具体来说，控制电路114可以为开关管Q1提供控制信号S1，为开关管Q2提供控制信号S2，为开关管Q3提供控制信号S3，为开关管Q4提供控制信号S4。
假设开关管Q1至开关管Q4皆为高电平导通，低电平关断的开关管，则控制信号S1至S4可以如图3所示。由图3可见，控制信号S1至S4皆为周期信号，且周期为T。在周期T内包括时间段t1和时间段t2，接下来，对时间段t1和时间段t2内转换电路112的等效电路分别进行说明。
时间段t1
在时间段t1内，控制信号S1和S3为高电平，控制信号S2和S4为低电平，因此开关管Q1和Q3导通，开关管Q2和Q4关断。在此情况下，转换电路112的等效电路可以如图4a所示。
由图4a可见，电流从转换电路112的高电势输入端i+输入，经电感Lr1、开关管Q2、电容C1和开关管Q4依次传输后，电流从转换电路112的低电势输入端i-输出。输入电压Vin对电容C1充电，使电容C1的电压逐渐达到输入电压Vin。
时间段t2
在时间段t1内，控制信号S1和S3为低电平，控制信号S2和S4为高电平，因此开关管Q1和Q3关断，开关管Q2和Q4导通。在此情况下，转换电路112的等效电路可以如图4b所示。
由图4b可见，电流从转换电路112的高电势输入端i+输入，经电感Lr1、开关管Q3、 电容C1、开关管Q1和电容C2依次传输后，电流从转换电路112的低电势输入端i-输出。输入电压Vin和电容C1串联，为电容C2充电。转换电路112的输出电压Vout，也就是电容C2的电压，为输入电压Vin和电容C1的电压之和。由于在时间段t1中，电容C1的电压达到了输入电压Vin，因此在时间段t2转换电路112的输出电压Vout可以达到2Vin。
需要指出的是，电感Lr1可以与电容C1产生谐振。在开关管Q1至Q4的开关频率Fsw满足以下公式一时，电感Lr1可以使开关管Q2和开关管Q4导通时实现零电流开关(zero current switched，ZCS)。
Figure PCTCN2021074526-appb-000001
在公式一中，Lr1表示电感Lr1的电感量，C1表示电容C1的电容量。当开关管Q2和开关管Q4实现零电流开关时，可以有效降低开关管Q2和开关管Q4的导通损耗，有利于提高转换电路112的效率。
可以理解，图2所示的转换电路112的变比为2，即Vout＝2Vin。在图2所示的转换电路112的基础上，通过增加开关管和电容的数量，可以实现更高的变比。例如图5中，通过增加一对开关管(开关管Q5和Q6)和电容C3，可以将转换电路112的变比增大至3，即Vout＝3Vin。
综上所述，图2所示的转换电路112通过开关管控制电容的充电和放电，从而实现电压变换，因此图2所示的转换电路112也可以称为开关电容电路。需要指出的是，电感Lr1主要用于使开关管Q2和Q4实现ZCS，电感Lr1的电感量较小，对电压转换的影响可以忽略。
目前，开关电容电路的变比多为整数，开关电容电路的输出电压无法连续调节。例如图2所示的转换电路112的变比为2，输出电压Vout＝2Vin。又例如，图5所示的转换电路112的变比为3，输出电压Vout＝3Vin，这便限制了开关电容电路在转换电路112中的应用。另外，在时间段t2内，由于电感Lr1与电容C1和电容C2同时谐振，若要实现开关管Q1和开关管Q3的ZCS，则开关管Q1至Q4的开关频率Fsw满足以下公式二：
Figure PCTCN2021074526-appb-000002
其中，公式二中的C2表示电容C2的电容量。
对比公式一和公式二可见，根据公式二计算得到的Fsw大于根据公式一计算得到的Fsw。也就是说，在开关管Q2和开关管Q4实现ZCS的情况下，开关管Q1和开关管Q3无法实现ZCS。相应的，在开关管Q1和开关管Q3实现ZCS的情况下，开关管Q2和开关管Q4无法实现ZCS。因此，图2所示的转换电路的效率还有待进一步提高。
有鉴于此，转换电路112还可以如图6所示。转换电路112包括开关管Q1至Q4、电容C2、电容C3、电感Lr1和电容Cr1。其中，开关管Q1至Q4之间的连接关系与图2类似，具体不再赘述。
电容C2的一端与转换电路112的高电势输出端o+连接，电容C2的另一端与电容C3的一端连接。电容C3的一端分别与开关管Q3的第一电极和转换电路112的高电势输入端i+连接，电容C3的另一端分别与开关管Q4的第二电极和转换电路112的低电势输入端i- 连接。电感Lr1的一端与开关管Q2的第一电极连接，电感Lr1的另一端与电容Cr1的一端连接，电容Cr1的另一端与开关管Q3的第二电极连接。
图6所示的转换电路112中，开关管Q1至Q4依旧可以适用图3所示的控制信号。基于图6所示的转换电路112，接下来，对时间段t1和时间段t2内转换电路112的等效电路分别进行说明。
时间段t1
在时间段t1内，控制信号S1和S3为高电平，控制信号S2和S4为低电平，因此开关管Q1和Q3导通，开关管Q2和Q4关断。在此情况下，转换电路112的等效电路可以如图7a所示。
电流从转换电路112的高电势输入端i+输入，经开关管Q2、电感Lr1、电容Cr1和开关管Q4传输后，从转换电路112的低电势输入端i-输出。在此过程中，电容Cr1和电感Lr1充电。可以认为，电容Cr1的电压和电感Lr1的电压之和可以达到输入电压Vin。
由此可见，在时间段t1内电感Lr1和电容Cr1谐振。也就是说，开关管Q1至Q4的开关频率Fsw满足以下公式三时，可以使开关管Q2和开关管Q4实现ZCS：
Figure PCTCN2021074526-appb-000003
在公式三中，Cr1表示电容Cr1的电容量。
时间段2
在时间段t2内，控制信号S1和S3为高电平，控制信号S2和S4为低电平，因此开关管Q1和Q3导通，开关管Q2和Q4关断。在此情况下，转换电路112的等效电路可以如图7b所示。
电流从电容Cr1靠近电感Lr1的一端输出，经电感Lr1、开关管Q1、电容C2和开关管Q3传输后，回流至电容Cr1靠近开关管Q3的一端。在此过程中，电容Cr1和电感Lr1放电，从而可以为电容C2充电。由于在时间段t1中，电容Cr1和电感Lr1的电压之和可以达到输入电压Vin，因此在时间段t2中，电容C2的电压可以达到输入电压Vin。
由图7b可见，电容C2和电容C3串联于转换电路112的高电势输出端o+和低电势输出端o-之间，因此输出电压Vout等于电容C2和电容C3的电压之和。其中，电容C3两端的电压即为输入电压Vin。在电容C2的电压也为输入电压Vin的情况下，图6所示的转换电路112的输出电压Vout可以达到2Vin。也就是说，图6所示的转换电路的变比为2。
由此可见，在时间段t1内电感Lr1、电容Cr1和电容C2谐振。也就是说，开关管Q1至Q4的开关频率Fsw满足以下公式四时，可以使开关管Q1和开关管Q3实现ZCS：
Figure PCTCN2021074526-appb-000004
一般来说，电容C2的电容量远远大于电容Cr1的电容量，例如，电容C2的电容量可以是电容Cr1的电容量的100倍。则根据公式四Fsw可以约等于
Figure PCTCN2021074526-appb-000005
趋近于公式三所示的Fsw。因此，采用公式三所示的开关频率Fsw时，图6所述的开关电容中开关管Q1至Q4皆可以实现ZCS，从而有利于进一步提高转换电路112的效率。
虽然图2和图6所示的转换电路112具有较高的效率，但本质上仍为开关电容电路，只能实现整数变比，转换电路112的变比无法连续调节。有鉴于此，还可以在转换电路112中集成降压(buck)电路，如图8所示。图8所示的转换电路112主要包括buck单元和开关电容单 元，其中，buck单元采用buck电路拓扑结构，开关电容单元采用开关电容电路拓扑结构。
开关电容单元的具体实现可以参考图6，具体不再赘述。为了便于理解，本申请实施例接下来，以开关电容单元的变比为2的场景进行说明。
为了便于说明，本申请实施例以正向电压表示buck单元的输出电压。buck单元可以对输入电压Vin进行降压转换，从而得到该正向电压。具体来说，如图8所示，buck单元包括电容C1、电感L1、开关管Q7和开关管Q8。其中，电感L1的一端与转换电路112的高电势输入端i+连接，电感L1的另一端分别与开关管Q7的第二电极和开关管Q8的第一电极连接。开关管Q7的第一电极与转换电路112的高电势输出端o+连接。开关管Q8的第二电极与开关电容单元中电容C3的一端连接。电容C1的一端与转换电路112的高电势输入端i+连接，电容C1的另一端分别与转换电路112的低电势输入端i-和转换电路112的低电势输出端o-连接。
示例性的，电感L1可以是包括线圈和磁芯的、具有较强的储能能力的电感。电感L1的磁芯可以是铁氧体、铁粉心等类型，线圈可以是偏平线、利兹线等类型，本申请实施例对此并不多作限制。
在每个周期内，图8所示的转换电路112主要存在两种开关状态：
状态一：开关管Q7导通，开关管Q8关断。
在此情况下，电流从转换电路112的高电势输入端i+输入，经电感L1、开关管Q7传输后从转换电路112的高电势输出端o+输出。回流的电流从转换电路112的低电势输出端o-输入，并回流至转换电路112的低电势输入端i-，从而构成电感L1的充电回路。在此情况下，电感L1充电，输出电压Vout为输入电压Vin减去电感L1的电压后的差值。也就是说，此时电感L1的电压VL1满足以下公式五：
VL1＝Vin-Vout(公式五)
需要指出的是，本申请实施例中电感L1的电压为电感L1中，与高电势输入端i+连接的一端的电势减去电感L1的另一端的电势的电势差，后续实施例不再赘述。
状态二：开关管Q7关断，开关管Q8导通。
在此情况，电流从转换电路112的高电势输入端i+输入，经电感L1、开关管Q8和电容C3传输后，回流至转换电路112的低电势输入端i-，从而构成电感L1的放电回路。在此情况下，电感L1放电，电容C3的电压为输入电压Vin减去电感L1的电压后的差值。即
VC3＝Vin-VL1。又由于开关电容单元的变比为2，也就是说，Vout＝2VC3，因此可以得到以下公式六：
VL1＝Vin-Vout/2(公式六)
假设开关管Q7的占空比为D，表示在每个周期内，开关管Q7导通时间在周期内的比例。则根据伏秒平衡原则可知(Vin-Vout)D+(Vin-Vout/2)(1-D)＝0，进而可得以下公式七：
Figure PCTCN2021074526-appb-000006
在公式七中，开关管Q7的占空比D可以是[0,1]中的任意取值。通过调节开关管Q7的占空比D，便可以使输出电压Vout在Vin至2Vin之间连续变化。其中，在D取值为0，即开关管Q7在周期内保持关断，开关管Q8在周期内保持导通，此时输出电压Vout可以达到2Vin。在D取值为1，即开关管Q7在周期内保持导通，开关管Q8在周期内保持关断，此时输出电压Vout可以达到Vin。
然而，图8所示的转换电路112的输出电压Vout仍存在限制，其最大只能达到2Vout，即转换电路112的最大变比只能达到开关电容单元的变比。有鉴于此，本申请实施例提供一种转换电路，该转换电路可以作为图1所示的转换电路112。该转换电路的最大变比不受开关电容单元的变比的限制，并支持对转换电路的变比进行连续调节。
示例性的，如图9所示，本申请实施例所提供的转换电路90主要包括降压-升压(buck-boost)单元91和开关电容单元92。其中，buck-boost单元91的高电势端和开关电容单元92的高电势端皆与转换电路90的高电势输出端o+连接，buck-boost单元91的第一中间端与开关电容单元92的第二中间端连接，buck-boost单元91的低电势端和开关电容单元92的低电势端皆与转换电路90的低电势输出端o-连接。
buck-boost单元91可以接收第一输入电压Vin1，对第一输入电压Vin1进行buck转换或boost转换后得到正向电压，并将正向电压提供给开关电容单元。具体来说，buck-boost单元91既可以对第一输入电压Vin1进行buck转换，在此情况下，正向电压不小于第一输入电压Vin1的1/N，且不大于第一输入电压Vin1。N为开关电容单元92的变比，N为大于或等于1的整数。buck-boost单元91也可以对第一输入电压Vin1进行boost转换，在此情况下，正向电压不小于第一输入电压Vin1。开关电容单元92可以对正向电压进行升压转换，并将升压转换后的正向电压作为第一输出电压Vout1输出。假设正向电压为V1，则第一输出电压Vout1＝NV1。
由于本申请实施例中的buck-boost单元91可以对第一输入电压进行buck转换，则在buck-boost单元91对第一输入电压进行buck转换的情况下，根据上述公式七可见，第一输出电压Vout1可以达到Vin1至2Vin1之间的任一电压。又由于buck-boost单元91还可以对第一输入电压进行boost转换，则在buck-boost单元91对第一输入电压进行boost转换的情况下，正向电压可以达到不小于Vin的取值。开关电容单元32在对正向电压进行升压转换后，第一输出电压Vout1可以达到不小于2Vin1的取值。
因此，本申请实施例所提供的转换电路90不仅可以支持变比连续可调，且转换电路90的最大变比不再受限于开关电容单元92的变比。因此，本申请实施例所提供的转换电路90具有更高的普适性。
可以理解，本申请实施例对开关电容单元92的具体实现并不多作限制，开关电容单元92的第二中间端和低电势端可以理解为开关电容单元92用于接收正向电压的两端。示例性的，该开关电容单元92的电路拓扑结构可以是图2和图6所示的开关电容电路拓扑结构。在图9所示的转换电路90中，开关电容单元92的第二中间端可以理解为电容C2与电容C3之间的电连接中的任一连接点。
接下来，通过以下实施例对本申请实施例中的buck-boost单元91作进一步的示例性说明。
实施例一
如图9所示，buck-boost单元91包括电感L1、二极管D1、二极管D2、开关管Q8和开关管Q9。其中，电感L1的一端与转换电路90的高电势输入端i+连接，电感L1的另一端分别与二极管D1的阳极、开关管Q9的第一电极和开关管Q8的第一电极连接。二极管D1的阴极与转换电路90的高电势输出端o+连接，开关管Q8的第二电极分别与转换电路90的低电势输入端i-和低电势输出端o-连接。开关管Q9的第二电极与二极管D2的阳极连接，二极管D2的阴极可以作为buck-boost单元91的第一中间端与开关电容单元92的第二中间端连接。
图9中buck-boost单元91既可以对第一输入电压V1进行buck转换，也可以对第一输入电 压V1进行boost转换，具体来说：
1、在buck-boost单元91对第一输入电压Vin1进行buck转换时，转换电路90的第一输出电压Vout1可以是Vin1至2Vin1之间的任一取值。
基于图9所示的转换电路90，假设开关管Q8和开关管Q9皆为高电平导通，低电平关断的开关管。则，采用图10所示的控制信号，可以使buck-boost单元91对第一输入电压Vin1进行buck转换。其中，控制信号S8用于控制开关管Q8的导通和关断，控制信号S9用于控制开关管Q9的导通和关断。
如图10所示，在周期T内控制信号S8为低电平，因此开关管Q8在周期T内保持关断。在周期T的时间段ta内，控制信号S9为高电平，因此在时间段ta内开关管Q9保持导通。在周期T的时间段tb内，控制信号S9为低电平，因此在时间段tb内开关管Q9保持关断。接下来，以开关电容单元92的变比为2的场景为例，分别对时间段ta和时间段tb中buck-boost单元91的等效电路进行说明。需要指出的是，由于buck-boost单元91的开关状态与开关电容单元92的开关状态并没有必然联系。因此，本申请实施例接下来并不限制开关电容单元92的开关状态。
时间段ta
如图10所示，在时间段ta内控制信号S8为低电平，因此开关管Q8关断。控制信号S9为高电平，因此开关管Q9导通，转换电路90的等效电路可以如图11a所示。电流从转换电路90的高电势输入端i+输入，经电感L1、开关管Q9、二极管D2和电容C3传输后，回流至转换电路90的低电势输入端i-，从而构成电感L1的充电回路。
此时，buck-boost单元91提供给开关电容单元92的正向电压，也就是电容C3的电压。由图11a可见，此时的正向电压为第一输入电压Vin1减去电感L1的电压后的差值，即VC3＝Vin1-VL1。又由于第一输出电压Vout1＝2VC3，由此可得，VL1＝Vin1-Vout1/2。
时间段tb
如图10所示，在时间段tb内控制信号S8为低电平，因此开关管Q8关断。控制信号S9为低电平，因此开关管Q9关断，转换电路90的等效电路可以如图11b所示。电流从转换电路90的高电势输入端i+输入，经电感L1和二极管D1传输后，从转换电路90的高电势输出端o+输出。回流的电流从转换电路90的低电势输出端o-输入，并回流至转换电路90的低电势输入端i-，从而构成电感L1的放电回路。此时，Vin1-VL1-Vout1＝0，进而可得，VL1＝Vin1-Vout1。
结合时间段ta和时间段tb中电感L1的电压，根据伏秒平衡原则可得：(Vin1-Vout1/2)ta+(Vin1-Vout1)tb＝0。假设开关管Q9的占空比为D1，即D1＝ta/T＝ta/(ta+tb)，进而可得以下公式八：
Figure PCTCN2021074526-appb-000007
在公式八中，开关管Q9的占空比D1可以是[0,1]中的任意取值。通过调节开关管Q9的占空比D1，便可以使第一输出电压Vout1在Vin1至2Vin1之间连续变化。其中，在D1取值为0，即开关管Q9在周期内保持关断，此时第一输出电压Vout1可以达到Vin1。在D1取值为1，即开关管Q9在周期内保持导通，此时第一输出电压Vout1可以达到2Vin1。
2、在buck-boost单元91对第一输入电压Vin1进行boost转换时，转换电路90的第一输出 电压Vout1可以是不小于2Vin1的任一取值。
基于图9所示的转换电路90，假设开关管Q8和开关管Q9皆为高电平导通，低电平关断的开关管。则，采用图12所示的控制信号，可以使buck-boost单元91对第一输入电压Vin1进行boost转换。其中，控制信号S8用于控制开关管Q8的导通和关断，控制信号S9用于控制开关管Q9的导通和关断。
如图10所示，在周期T内控制信号S9为高电平，因此开关管Q9在周期T内保持导通。在周期T的时间段ta内，控制信号S8为高电平，因此在时间段ta内开关管Q8保持导通。在周期T的时间段tb内，控制信号S8为低电平，因此在时间段tb内开关管Q8保持关断。接下来，以开关电容单元92的变比为2的场景为例，分别对时间段ta和时间段tb中buck-boost单元91的等效电路进行说明。需要指出的是，由于buck-boost单元91的开关状态与开关电容单元92的开关状态并没有必然联系。因此，本申请实施例接下来并不限制开关电容单元92的开关状态。
时间段ta
如图12所示，在时间段ta内控制信号S9为高电平，因此开关管Q9导通。控制信号S8为高电平，因此开关管Q8导通，转换电路90的等效电路可以如图13a所示。电流从转换电路90的高电势输入端i+输入，经电感L1和开关管Q8传输后，回流至转换电路90的低电势输入端i-，从而构成电感L1的充电回路。此时，Vin1-VL1＝0，进而可得，VL1＝Vin1。
时间段tb
如图12所示，在时间段tb内控制信号S8为低电平，因此开关管Q8关断。控制信号S9为高电平，因此开关管Q9导通，转换电路90的等效电路可以如图13b所示。
电流从转换电路90的高电势输入端i+输入，经电感L1、开关管Q9、二极管D2和电容C3传输后，回流至转换电路90的低电势输入端i-，从而构成电感L1的放电回路。此时，Vin1-VL1-VC3＝0，电容C3的电压VC3也就是buck-boost单元91提供给开关电容单元92的正向电压。又由于Vout1＝2VC3，进而可得VL1＝Vin1-Vout1/2。
结合时间段ta和时间段tb中电感L1的电压，根据伏秒平衡原则可得：(Vin1)ta+(Vin1-Vout1/2)tb。假设开关管Q8的占空比为D2，即D2＝ta/T＝ta/(ta+tb)，进而可得以下公式九：
Figure PCTCN2021074526-appb-000008
在公式九中，开关管Q8的占空比D2可以是[0,1]中的任意取值。通过调节开关管Q8的占空比D2，便可以使第一输出电压Vout1在2Vin～∞的范围内连续变化。其中，在D2取值为0，即开关管Q8在周期内保持关断，此时第一输出电压Vout1可以达到2Vin1。在D2取值为1，即开关管Q8在周期内保持导通，此时第一输出电压Vout1可以达到无穷大。
需要指出的是，本申请实施例是在不考虑电感L1储能能力限制的情况下，认为第一输出电压可以达到无穷大。在实际应用时，第一输出电压Vout1实际可以达到的最大值还受电感L1的电感量大小等因素限制。
实施例二
在一种可能的实现方式中，本申请实施例所提供的转换电路90还可以通过高电势输出端o+和低电势输出端o-接收第二输入电压Vin2。开关电容单元92可以对第二输入电压 Vin2进行降压转换，以得到逆向电压。假设开关电容单元92的变比为N，则该逆向电压可以为Vin2/N。
开关电容单元92可以通过第二中间端和低电势端向buck-boost单元91传输该逆向电压。buck-boost单元91对该逆向电压进行buck-boost转换，并将buck-boost转换后的逆向电压作为第二输出电压Vout2，通过转换电路90的高电势输入端i+和低电势输入端i-输出该第二输出电压Vout2。
示例性的，如图14所示，buck-boost单元91还可以包括开关管Q7和开关管Q10。其中，开关管Q7包括上述二极管D1，开关管Q10包括上述二极管D2。开关管Q7的第一电极与转换电路90的高电势输出端o+连接，开关管Q7的第二电极与电感L1的另一端连接。开关管Q10的第一电极作为buck-boost单元91的第一中间端与开关电容单元92连接，开关管Q10的第二电极与开关管Q9的第二电极连接。
以及，开关管Q8包括二极管D3，二极管D3的阳极与转换电路的低电势输入端i-连接，二极管D3的阴极与电感L1靠近开关管Q9的另一端连接。开关管Q9包括二极管D4，二极管D4的阳极与开关管Q10连接，二极管D4的阴极与电感L1连接。
可以理解，为了使开关管Q7和开关管Q10不影响第一输入电压Vin1向第一输出电压Vout1的转换，在第一输入电压Vin1向第一输出电压Vout1的转换的过程中可以保持开关管Q7和开关管Q10关断。
示例性的，如图10所示，控制信号S7为控制开关管Q7的控制信号，控制信号S10为控制开关管Q10的控制信号。由图10可见，在buck-boost单元对第一输入电压Vin1进行buck转换时，控制信号S7和S10皆为低电平，开关管Q7和Q10保持关断。又例如图12所示，在buck-boost单元对第一输入电压Vin1进行boost转换时，控制信号S7和S10皆为低电平，开关管Q7和Q10保持关断。
图14所示的转换电路90可以对第二输入电压Vin2进行降压转换。其中，buck-boost单元91既可以对逆向电压进行buck转换，又可以对逆向电压进行boost转换。具体来说：
1、在buck-boost单元91对逆向电压进行buck转换时，转换电路90的第二输出电压Vout2可以是0至Vin2/2之间的任一取值。
基于图14所示的转换电路90，假设开关管Q7至Q10皆为高电平导通，低电平关断的开关管。则，采用图15所示的控制信号，可以使buck-boost单元91对逆向电压进行buck转换。
如图15所示，在周期T内控制信号S7、S8和S9为低电平，因此开关管Q7至Q9在周期T内保持关断。在周期T的时间段ta内，控制信号S10为高电平，因此在时间段ta内开关管Q10保持导通。在周期T的时间段tb内，控制信号S10为低电平，因此在时间段tb内开关管Q10保持关断。
接下来，以开关电容单元92的变比为2的场景为例，分别对时间段ta和时间段tb中buck-boost单元91的等效电路进行说明。需要指出的是，由于buck-boost单元91的开关状态与开关电容单元92的开关状态并没有必然联系。因此，本申请实施例接下来并不限制开关电容单元92的开关状态。
时间段ta
如图15所示，在时间段ta内开关管Q7、Q8和Q9关断，开关管Q10导通，转换电路90的等效电路可以如图16a所示。
电流从电容C3靠近开关管Q10的一端输出，经开关管Q10、开关管Q9中的二极管 D4、电感L1传输后，从转换电路90的高电势输入端i+输出。回流的电流从转换电路90的低电势输入端i-输入，并回流至电容C3靠近转换电路90的低电势输入端i-的一端，从而构成电感L1的充电回路。
此时，开关电容单元92提供给buck-boost单元91的逆向电压，也就是电容C3的电压。由图16a可见，此时VC3+VL1-Vout2＝0，也就是VL1＝Vout2-VC3＝Vout2-Vin2/2。
时间段tb
如图15所示，在时间段tb内控制信号S7至S10皆为低电平，因此开关管Q7至Q10皆关断，转换电路90的等效电路可以如图16b所示。电流从转换电路90的高电势输入端i+输出，回流的电流从转换电路90的低电势输入端i-输入，并经二极管D3回流至电感L1靠近开关管Q8的一端，从而构成电感L1的放电回路。此时，Vout2-VL1＝0也就是说，VL1＝Vout2。
结合时间段ta和时间段tb中电感L1的电压，根据伏秒平衡原则可得：(Vout2-Vin2/2)ta+(Vout2)tb＝0。假设开关管Q10的占空比为D3，即D3＝ta/T＝ta/(ta+tb)，进而可得以下公式十：
Figure PCTCN2021074526-appb-000009
在公式十中，开关管Q10的占空比D3可以是[0,1]中的任意取值。通过调节开关管Q10的占空比D3，便可以使第二输出电压Vout2在0至Vin2/2之间连续变化。其中，在D3取值为0，即开关管Q10在周期内保持关断，此时第二输出电压Vout2可以达到0。在D3取值为1，即开关管Q10在周期内保持导通，此时第二输出电压Vout2可以达到Vin2/2。
2、在buck-boost单元91对逆向电压进行boost转换时，转换电路90的第二输出电压Vout2可以是Vin2/2至Vin2之间的任一取值。
基于图14所示的转换电路90，假设开关管Q7至Q10皆为高电平导通，低电平关断的开关管。则，采用图17所示的控制信号，可以使buck-boost单元91对逆向电压进行boost转换。
如图17所示，在周期T内控制信号S8和S9为低电平，因此开关管Q8和Q9在周期T内保持关断。在周期T内控制信号S10为高电平，因此开关管Q10在周期T内保持导通。在周期T的时间段ta内，控制信号S7为高电平，因此在时间段ta内开关管Q7保持导通。在周期T的时间段tb内，控制信号S7为低电平，因此在时间段tb内开关管Q7保持关断。
接下来，以开关电容单元92的变比为2的场景为例，分别对时间段ta和时间段tb中buck-boost单元91的等效电路进行说明。需要指出的是，由于buck-boost单元91的开关状态与开关电容单元92的开关状态并没有必然联系。因此，本申请实施例接下来并不限制开关电容单元92的开关状态。
时间段ta
如图17所示，在时间段ta内开关管Q8和Q9关断，开关管Q7和Q10导通，转换电路90的等效电路可以如图18a所示。电流从转换电路90的高电势输出端o+输入，经开关管Q7和电感L1传输后，从转换电路90的高电势输入端i+输出。回流的电流从转换电路90的低电势输入端i-输入，并回流至转换电路90的低电势输出端o-，从而构成电感L1的充电回路。在此情况下，Vin2+VL1-Vout2＝0，即VL1＝Vout2-Vin2。
时间段tb
如图17所示，在时间段tb内控制信号S7至S9皆为低电平，因此开关管Q7至Q9皆关断，控制信号S10为高电平，因此开关管Q10导通，转换电路90的等效电路可以如图18b所示。电流从电容C3靠近开关管Q10的一端输出，经电感L1传输后从转换电路90的高电势输入端i+输出，回流的电流从转换电路90的低电势输入端i-输入，并回流至电容C3靠近转换电路90的低电势输入端i-的一端，从而构成电感L1的放电回路。此时，Vout2-VL1-VC3＝0。电容C3的电压VC3也就是开关电容单元92提供给buck-boost单元91的逆向电压，进而可得，VL1＝Vout2-VC3＝Vout2-Vin2/2。
结合时间段ta和时间段tb中电感L1的电压，根据伏秒平衡原则可得：(Vout2-Vin2)ta+(Vout2-Vin2/2)tb＝0。假设开关管Q7的占空比为D4，即D4＝ta/T＝ta/(ta+tb)，进而可得以下公式十一：
Figure PCTCN2021074526-appb-000010
在公式十一中，开关管Q7的占空比D4可以是[0,1]中的任意取值。通过调节开关管Q7的占空比D4，便可以使第二输出电压Vout2在Vin2/2至Vin2之间连续变化。其中，在D4取值为0，即开关管Q7在周期内保持关断，此时第二输出电压Vout2可以达到Vin2/2。在D4取值为1，即开关管Q7在周期内保持导通，此时第二输出电压Vout2可以达到Vin2。
由上述实施例一可见，本申请实施例所提供的转换电路90可以将第一输入电压Vin1转换至Vin1至无穷大。示例性的，控制电路114可以采用如图19所示的方法确定开关管Q8或开关管Q9的占空比，使第一输出电压Vin1可以达到转换电路90所需输出的第一目标电压。具体来说，主要包括以下步骤：
S1901：电压转换装置上电。示例性，该电压转换装置可以是图1所示的DCDC升压器11。电压转换装置上电后，转换电路90的高电势输入端i+和低电势输入端i-可以接收到第一输入电压Vin1。
S1902：控制电路114控制开关电容单元92中的开关管Q1至Q4导通和关断，使电容C2和电容C3的电压达到平衡，即二者电压相等。
S1903：控制电路114保持开关管Q7、Q8和Q10关断，并调节开关管Q9的占空比D1。示例性的，控制电路114可以按照开关管Q9的占空比D1由0向1逐渐增大的方式调节开关管Q9的占空比D1。
S1904：在[0,1]的范围内调节占空比D1的过程中，若第一输出电压Vout1达到了第一目标电压，则控制电路114继续执行S1905。若在[0,1]的范围内调节占空比D1，无法使第一输出电压Vout1达到第一目标电压，则控制电路114继续执行S1906。
S1905：控制电路114保持开关管Q9当前的占空比D1。
S1906：若在[0,1]的范围内调节占空比D1，无法使第一输出电压Vout1达到第一目标电压，说明第一目标输出电压有可能超过了2Vin1。因此，控制电路114可以保持开关管Q7和Q10关断，开关管Q9导通，并调节开关管Q8的占空比D2。
S1907：在[0,1]的范围内调节占空比D2的过程中，若第一输出电压Vout1达到了第一目标电压，则控制电路114继续执行S1908。若在[0,1]的范围内调节占空比D2，无法使第一输出电压Vout1达到第一目标电压，则控制电路114继续执行S1909。
S1908：控制电路114保持开关管Q8当前的占空比D2。
S1909：转换电路90状态错误。控制电路114可以上报该错误。例如，若第一目标电压小于Vin1，则转换电路90无法输出符合第一目标电压的第一输出电压，此时便可能出现状态错误。
与图19类似，控制电路114也可以先保持开关管Q7至Q9关断，并调节开关管Q10的占空比D3。在此过程中，若第二输出电压Vin2可以达到第二目标电压，则控制电路114可以保持开关管Q10当前的占空比D3。若在[0,1]内调节占空比D3，无法使第二输出电压达到第二目标电压，则控制电路114可以保持开关管Q8和Q9关断，保持开关管Q10导通，并调节开关管Q7的占空比D4。在此过程中，若第二输出电压Vin2可以达到第二目标电压，则控制电路114可以保持开关管Q7当前的占空比D4。若在[0,1]内调节占空比D4，无法使第二输出电压达到第二目标电压，则意味着转换电路90状态错误。控制电路114可以上报该错误。
综上所述，本申请实施例提供了一种转换电路90，该转换电路90中包括buck-boost单元91和开关电容单元，且该转换电路90的变比不受开关电容单元的限制。需要指出的是，由于本申请实施例中开关电容单元92具有升压功能，因此对buck-boost单元91的升压能力要求较低，电感L1可以采用电感量较小的电感实现。一般来说，电感的电感量越大，损耗和体积便越大，因此相较于传统的boost电路，本申请实施例所提供的转换电路90有利于提高效率、缩小体积。
以图20所示的传统的boost电路为例，该传统的boost电路主要包括一个电感和两个开关管。假设转换电路90的第一输入电压Vin1，以及该传统的boost电路的输入电压皆为300-500V；转换电路90的第一输出电压Vout1，以及该传统的boost电路的输出电压皆为600-850V；转换电路90的功率，以及该传统的boost电路的功率皆为12.5kw。转换电路90和该传统的boost电路的设计参数如下表一所示：
表一
项目 转换电路90 传统boost电路
开关管 IGBT 650V/75A IGBT 1200V/75A
电感量 100uH 500uH
开关频率 20kHz 15kHz
具体来说，转换电路90中的各个开关管采用650V耐压、75A最大电流的IGBT，电感L1的电感量为100uH，开关频率为20kHz。传统boost电路中的各个开关管采用1200V耐压、75A最大电流的IGBT，电感的电感量为500uH，开关频率为15kHz。
经过对比，由图21可见，传统boost电路的体积与本申请实施例所提供的转换电路90的体积接近。但由图22可见，本申请实施例所提供的转换电路90的重量远远小于传统boost电路的重量，这主要是由于本申请在buck-boost单元91中可以采用体积更小的电感，可以降低电感的重量。且由图23可见，传统boost电路的效率约为97.5％，而本申请实施例所提供的转换电路90的效率则可以高达98.5％，转换电路90的效率得到了明显提升。
基于相同的技术构思，本申请实施例还提供一种电压转换装置，该电压转换装置可以包括本申请上述任一实施例所提供的转换电路90。示例性的，该电压转换装置可以作为电动汽车10中的DCDC升压器11。其中，转换电路90可以作为DCDC升压器11中的转换 电路112，控制电路114分别与buck-boost单元91和开关电容单元92中各个开关管的控制电极连接，从而可以控制转换电路90实现电压转换。
基于相同的技术构思，本申请实施例还提供一种电动汽车，该电动汽车可以如图1所示。其中，电动汽车10中包括DCDC升压器11，该DCDC升压器11与动力电池连接，可以为动力电池12充电。在DCDC升压器11中，转换电路112可以采用本申请实施例所提供的转换电路90实现。
显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本申请的保护范围。这样，倘若本申请的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (23)

  1. 一种转换电路，其特征在于，包括降压-升压buck-boost单元和开关电容单元，其中：
    所述buck-boost单元的高电势端和所述开关电容单元的高电势端皆与所述转换电路的高电势输出端连接，所述buck-boost单元的第一中间端与所述开关电容单元的第二中间端连接，所述buck-boost单元的低电势端和所述开关电容单元的低电势端皆与所述转换电路的低电势输出端连接；
    所述buck-boost单元用于接收第一输入电压，对所述第一输入电压进行buck-boost转换，并将buck-boost转换后的所述第一输入电压作为正向电压，通过所述第一中间端将所述正向电压提供给所述开关电容单元；
    所述开关电容单元用于对所述正向电压进行升压转换；
    所述转换电路的高电势输出端和低电势输出端用于输出第一输出电压，所述第一输出电压为升压转换后的所述正向电压。
  2. 根据权利要求1所述的转换电路，其特征在于，所述buck-boost单元包括第一二极管、第二二极管、第一开关管、第二开关管和第一电感；
    所述第一电感的一端与所述转换电路的高电势输入端连接，所述第一电感的另一端分别与所述第一二极管的阳极、所述第一开关管的第一电极和所述第二开关管的第一电极连接；
    所述第一二极管的阴极与所述转换电路的高电势输出端连接，所述第一开关管的第二电极与所述第二二极管的阳极连接，所述第二二极管的阴极与所述开关电容单元的第二中间端连接；
    所述第二开关管的第二电极分别与所述转换电路的低电势输入端和低电势输出端连接，所述转换电路的高电势输入端和低电势输入端用于接收所述第一输入电压。
  3. 根据权利要求2所述的转换电路，其特征在于，所述第一输出电压不小于所述第一输入电压，且所述第一输出电压不大于所述第一输入电压的N倍，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述第一开关管用于在周期时间内保持关断；
    所述第二开关管用于：
    在所述周期时间的第一时间段内保持导通，以使所述第一电感充电；
    在所述周期时间的第二时间段内保持关断，以使所述第一电感放电。
  4. 根据权利要求2所述的转换电路，其特征在于，所述第一输出电压不小于所述第一输入电压的N倍，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述第二开关管用于在周期时间内保持导通；
    所述第一开关管用于：
    在所述周期时间的第一时间段内保持导通，以使所述电感充电；
    在所述周期时间的第二时间段内保持关断，以使所述电感放电。
  5. 根据权利要求2至4中任一项所述的转换电路，其特征在于，所述转换电路的高电势输出端和低电势输出端还用于接收第二输入电压，所述转换电路的高电势输入端和低电势输入端还用于输出第二输出电压；
    所述开关电容单元还用于对所述第二输入电压进行降压转换，并将降压转换后的所述第二输入电压作为逆向电压，通过所述第二中间端将所述逆向电压提供给所述buck-boost单元；
    所述buck-boost单元，用于对所述逆向电压进行buck-boost转换，并将buck-boost转换后的所述逆向电压作为第二输出电压，通过所述转换电路的高电势输入端和低电势输入端输出所述第二输出电压。
  6. 根据权利要求5所述的转换电路，其特征在于，所述buck-boost单元还包括第三开关管和第四开关管，所述第三开关管包括所述第一二极管，所述第四开关管包括所述第二二极管；
    所述第三开关管的第一电极与所述转换电路的高电势输出端连接，所述第三开关管的第二电极与所述第一电感的另一端连接；
    所述第四开关管的第一电极与所述第二开关管的第二电极连接，所述第四开关管的第二电极与所述开关电容单元的第二中间端连接。
  7. 根据权利要求6所述的转换电路，其特征在于，所述第一开关管包括第三二极管，所述第三二极管的阳极与所述第四开关管的第一电极连接，所述第三二极管的阴极与所述第一电感的另一端连接；
    所述第二开关管包括第四二极管，所述第四二极管的阳极分别与所述转换电路的低电势输入端和低电势输出端连接，所述第四二极管的阴极与所述第一电感的另一端连接。
  8. 根据权利要求7所述的转换电路，其特征在于，所述第二输出电压不小于0，且所述第二输出电压不大于所述第二输入电压的1/N，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述第一开关管、所述第二开关管和所述第三开关管用于在周期时间内保持关断；
    所述第四开关管用于：
    在所述周期时间的第一时间段内保持导通，以使所述第一电感充电；
    在所述周期时间的第二时间段内保持关断，以使所述第一电感放电。
  9. 根据权利要求7所述的转换电路，其特征在于，所述第二输出电压不小于第二输入电压的1/N，且所述第二输出电压不大于所述第二输入电压，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述第一开关管和所述第二开关管用于在周期时间内保持关断；
    所述第四开关管用于在所述周期时间内保持导通；
    所述第三开关管用于：
    在所述周期时间的第一时间段内保持导通，以使所述第一电感充电；
    在所述周期时间的第二时间段内保持关断，以使所述第一电感放电。
  10. 一种电压转换装置，其特征在于，包括转换电路和控制电路，所述转换电路包括降压-升压buck-boost单元和开关电容单元，其中：
    所述buck-boost单元的高电势端和所述开关电容单元的高电势端皆与所述转换电路的高电势输出端连接，所述buck-boost单元的第一中间端与所述开关电容单元的第二中间端连接，所述buck-boost单元的低电势端和所述开关电容单元的低电势端皆与所述转换电路的低电势输出端连接；
    所述控制电路，用于：
    控制所述buck-boost单元对接收到的第一输入电压进行buck-boost转换，并将buck-boost转换后的所述第一输入电压作为正向电压，通过所述第一中间端将所述正向电压提供给所述开关电容单元；
    控制所述开关电容单元对所述正向电压进行升压转换；
    所述转换电路的高电势输出端和低电势输出端用于输出第一输出电压，所述第一输出电压为升压转换后的所述正向电压。
  11. 根据权利要求10所述的电压转换装置，其特征在于，所述buck-boost单元包括第一二极管、第二二极管、第一开关管、第二开关管和第一电感；
    所述第一电感的一端与所述转换电路的高电势输入端连接，所述第一电感的另一端分别与所述第一二极管的阳极、所述第一开关管的第一电极和所述第二开关管的第一电极连接；
    所述第一二极管的阴极与所述转换电路的高电势输出端连接，所述第一开关管的第二电极与所述第二二极管的阳极连接，所述第二二极管的阴极与所述开关电容单元的第二中间端连接；
    所述第二开关管的第二电极分别与所述转换电路的低电势输入端和低电势输出端连接，所述转换电路的高电势输入端和低电势输入端用于接收所述第一输入电压。
  12. 根据权利要求11所述的电压转换装置，其特征在于，所述第一输出电压不小于所述第一输入电压，且所述第一输出电压不大于所述第一输入电压的N倍，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述控制电路具体用于：
    控制所述第一开关管在周期时间内保持关断；
    控制所述第二开关管在所述周期时间的第一时间段内保持导通，以使所述第一电感充电；
    控制所述第二开关管在所述周期时间的第二时间段内保持关断，以使所述第一电感放电。
  13. 根据权利要求12所述的电压转换装置，其特征在于，所述控制电路还用于：
    保持所述第一开关管关断，调节所述第二开关管的占空比，所述第二开关管的占空比为所述第二开关管导通的第一时间段在所述周期时间的占比；
    在所述第一输出电压达到第一目标电压时，所述控制电路保持所述第二开关管当前的占空比。
  14. 根据权利要求11所述的电压转换装置，其特征在于，所述第一输出电压不小于所述第一输入电压的N倍，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述控制电路具体用于：
    控制所述第二开关管在周期时间内保持导通；
    控制所述第一开关管在所述周期时间的第三时间段内保持导通，以使所述电感充电；
    控制所述第一开关管在所述周期时间的第四时间段内保持关断，以使所述电感放电。
  15. 根据权利要求14所述的电压转换装置，其特征在于，所述控制电路还用于：
    保持所述第二开关管导通，并调节所述第一开关管的占空比，所述第一开关管的占空比为所述第一开关管导通的第三时间段在所述周期时间的占比；
    在所述第一输出电压达到第一目标电压时，所述控制电路保持所述第一开关管当前的 占空比。
  16. 根据权利要求11至15中任一项所述的电压转换装置，其特征在于，所述转换电路的高电势输出端和低电势输出端还用于接收第二输入电压，所述转换电路的高电势输入端和低电势输入端还用于输出第二输出电压；
    所述控制电路还用于：
    控制所述开关电容单元对所述第二输入电压进行降压转换，并将降压转换后的所述第二输入电压作为逆向电压，通过所述第二中间端将所述逆向电压提供给所述buck-boost单元；
    控制所述buck-boost单元对所述逆向电压进行buck-boost转换，并将buck-boost转换后的所述逆向电压作为第二输出电压，通过所述转换电路的高电势输入端和低电势输入端输出所述第二输出电压。
  17. 根据权利要求16所述的电压转换装置，其特征在于，所述buck-boost单元还包括第三开关管和第四开关管，所述第三开关管包括所述第一二极管，所述第四开关管包括所述第二二极管；
    所述第三开关管的第一电极与所述转换电路的高电势输出端连接，所述第三开关管的第二电极与所述第一电感的另一端连接；
    所述第四开关管的第一电极与所述第二开关管的第二电极连接，所述第四开关管的第二电极与所述开关电容单元的第二中间端连接。
  18. 根据权利要求17所述的电压转换装置，其特征在于，所述第一开关管包括第三二极管，所述第三二极管的阳极与所述第四开关管的第一电极连接，所述第三二极管的阴极与所述第一电感的另一端连接；
    所述第二开关管包括第四二极管，所述第四二极管的阳极分别与所述转换电路的低电势输入端和低电势输出端连接，所述第四二极管的阴极与所述第一电感的另一端连接。
  19. 根据权利要求18所述的电压转换装置，其特征在于，所述第二输出电压不小于0，且所述第二输出电压不大于所述第二输入电压的1/N，N为所述开关电容单元的变比，N为大于或等于1的整数；
    所述控制电路具体用于：
    控制所述第一开关管、所述第二开关管和所述第三开关管用于在周期时间内保持关断；
    控制所述第四开关管在所述周期时间的第五时间段内保持导通，以使所述第一电感充电；
    控制所述第四开关管在所述周期时间的第六时间段内保持关断，以使所述第一电感放电。
  20. 根据权利要求19所述的电压转换装置，其特征在于，所述控制电路还用于：
    保持所述第一开关管、所述第二开关管和所述第三开关管在周期时间内关断，并调节所述第四开关管的占空比，所述第四开关管的占空比为所述第四开关管导通的第五时间段在所述周期时间的占比；
    在所述第二输出电压达到第二目标电压时，所述控制电路保持所述第四开关管当前的占空比。
  21. 根据权利要求18所述的电压转换装置，其特征在于，所述第二输出电压不小于第二输入电压的1/N，且所述第二输出电压不大于所述第二输入电压，N为所述开关电容 单元的变比，N为大于或等于1的整数；
    所述控制电路具体用于：
    控制所述第一开关管和所述第二开关管在周期时间内保持关断；
    控制所述第四开关管在所述周期时间内保持导通；
    控制所述第三开关管在所述周期时间的第七时间段内保持导通，以使所述第一电感充电；
    控制所述第三开关管在所述周期时间的第八时间段内保持关断，以使所述第一电感放电。
  22. 根据权利要求21所述的电压转换装置，其特征在于，所述控制电路还用于：
    保持所述第一开关管和所述第二开关管关断，保持所述第四开关管导通，并调节所述第三开关管的占空比，所述第三开关管的占空比为所述第三开关管导通的第七时间段在所述周期时间的占比；
    在所述第二输出电压达到第二目标电压时，所述控制电路保持所述第三开关管当前的占空比。
  23. 一种电动汽车，其特征在于，包括动力电池和如权利要求10至22中任一项所述的电压转换装置，所述电压转换装置用于为所述动力电池充电。
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