CN109196768B - AC-DC power converter and method for the same - Google Patents
AC-DC power converter and method for the same Download PDFInfo
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- CN109196768B CN109196768B CN201680086262.1A CN201680086262A CN109196768B CN 109196768 B CN109196768 B CN 109196768B CN 201680086262 A CN201680086262 A CN 201680086262A CN 109196768 B CN109196768 B CN 109196768B
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal 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
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal 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
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal 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 in a bridge configuration
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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
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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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
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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
- H02M1/0077—Plural converter units whose outputs are connected in series
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention provides an AC-DC power converter and a method for operating the same. The AC-DC power converter includes: an AC-DC conversion circuit having a first controllable power switch configured to receive a first AC power and output a first DC power generated from the first AC power; a plurality of DC-DC conversion circuits, each of the plurality of DC-DC conversion circuits having an intermediate conversion to a second AC power source, the plurality of DC-DC conversion circuits configured to receive a first DC power source and combine a second DC power source output, wherein each of the plurality of DC-DC conversion circuits comprises a full-bridge DC-AC conversion circuit having a second controllable power switch, a DC side thereof coupled across the output of the AC-DC conversion circuit, a capacitive element interposed between both ends of an AC side thereof; and a controller configured to: generating a first control signal for turning on and off a first controllable power switch of the AC-DC conversion circuit such that a DC voltage of the first DC power source is adjustable within a DC voltage range; and generating a plurality of second control signals, each of the plurality of second control signals for turning on and off a second controllable power switch of a corresponding full-bridge DC-AC conversion circuit of the plurality of DC-DC conversion circuits in a full-bridge mode and a half-bridge mode, such that the plurality of DC-DC conversion circuits exhibit multi-stage voltage gains; wherein: the DC voltage range of the AC-DC conversion circuit is set to cover the voltage increase of two consecutive stages of voltage gain.
Description
Technical Field
The present invention relates to converting an AC power input into a DC power output using direct DC-DC power conversion, and more particularly to a direct DC-DC conversion apparatus for parallel operation.
Background
In many applications, the power converter needs to operate over a wide input or output voltage range. There is a trade-off between input or output voltage range and conversion efficiency. Power converters operating over a wide input voltage range or output voltage range exhibit greater efficiency degradation than their narrow range counterparts. Most conventional power converters are only able to ensure high efficiency over a narrow output voltage range for a given input voltage. This is because the design of the power converter is often referred to as a single operating point or narrowed operating region. Thus, when operating the converter and components away from the design point or region, losses and stresses across the converter and components will increase. This problem is particularly acute in applications with a wide voltage range, such as the present DC fast charger for electric vehicles, for example, with an output voltage range of 200V to 550V or even 750V in china.
For example, U.S. patent No. 8,300,438 discloses an AC-DC power converter having three-phase boost and buck converters connected in parallel with respective three-phase inputs and in series with respective three-phase outputs. The power converter has a first control circuit and a second control circuit that operate the three-phase boost converter at a duty ratio of 0% and the three-phase buck converter at a duty ratio of 100%, respectively, such that the phase A, B and the C boost duty ratio and the phase A, B and the C buck duty ratio are approximately defined by a predetermined equation in which the phase angle of the three-phase sine wave voltage is used as a variable. This helps to provide higher efficiency because the duty cycle of each phase is limited to being continuous in one third of the AC cycle. However, when both the 0% boost converter and the 100% buck converter operate, the output voltage is not regulated but is linearly proportional to the magnitude of the input voltage. As a result, the power converter suffers from a relatively narrow output voltage range at a given input voltage due to its linear voltage gain. Therefore, such a power converter is not suitable for applications having a relatively wide output voltage range.
Disclosure of Invention
According to an aspect of the present invention, there is provided an AC-DC power converter including: an AC-DC conversion circuit having a first controllable power switch, the AC-DC conversion circuit configured to receive a first AC power and output a first DC power generated from the first AC power; a plurality of DC-DC conversion circuits, each of the plurality of DC-DC conversion circuits having an intermediate conversion to a second AC power source, the plurality of DC-DC conversion circuits configured to receive a first DC power source and combine a second DC power source output. Wherein each of the plurality of DC-DC conversion circuits comprises a full-bridge DC-AC conversion circuit having a second controllable power switch with its DC side coupled across the output of the AC-DC conversion circuit and with a capacitive element interposed between the two ends of its AC side; and a controller configured to: generating a first control signal for turning on and off a first controllable power switch of the AC-DC conversion circuit such that a DC voltage of the first DC power source is adjustable within a DC voltage range; and generating a plurality of second control signals, each of the plurality of second control signals for turning on and off a second controllable power switch of a corresponding full-bridge DC-AC conversion circuit of the plurality of DC-DC conversion circuits in a full-bridge mode and a half-bridge mode, such that the plurality of DC-DC conversion circuits exhibit multi-stage voltage gains; wherein: the DC voltage range of the AC-DC conversion circuit is set to cover the voltage increase of two consecutive stages of voltage gain.
According to another aspect of the present invention, there is provided a method for operating an AC-DC power converter, the method comprising: generating a first DC power source having an adjustable DC voltage range from a first AC power source; and combining a plurality of outputs from the DC-DC power conversion of the first DC power source to produce a second DC power source, wherein each of the plurality of DC-DC power conversions has an intermediate power conversion to the second AC power source through a capacitive element and is implemented in a full-bridge mode or a half-bridge mode such that the plurality of DC-DC power conversions exhibit a multi-level voltage gain; wherein: the DC voltage range is adjusted to cover the voltage increase of two consecutive stages of voltage gain.
For applications requiring a relatively wide voltage range such as the DC fast charger of the electric vehicle of today, in order to maintain high power efficiency over a wide voltage range, a plurality of DC-DC conversion circuits are linked in parallel at their input terminals, and any one of the DC-DC conversion circuits needs to take responsibility for partial voltage regulation while all the DC-DC conversion circuits operate at their design points to ensure high efficiency. The AC-DC conversion circuit may be regulated by the controller (e.g., by varying the duty cycle of its switches) to supply a DC output voltage that continuously increases from a lower endpoint to a higher endpoint. Thus, the voltage gaps between two adjacent discrete levels (e.g., between HO and HH, HH and FH, FO and FH, and FH and FF) can continuously bridge-tune the DC output voltage of the AC-DC conversion circuit.
Preferably, in the full-bridge mode, each of the second controllable power switches in the first and second branches of the full-bridge DC-AC conversion circuit operates at substantially the same duty cycle and substantially the same switching frequency; and in the half-bridge mode, each of the second controllable power switches in the first branch is operated with substantially the same duty cycle and substantially the same switching frequency, and one of the second controllable power switches in the second branch is continuously on and the other second controllable power switch in the second branch is continuously off.
Preferably, the outputs of the DC-DC conversion circuits are coupled in series. A plurality of possible level voltage gains can be obtained, thereby exhibiting multi-level voltage gains of the DC-DC conversion circuit. Since the DC-DC conversion circuit has a plurality of fixed-stage voltage gains, its DC output voltage is adjusted by changing the DC input voltage, which is the output voltage of the AC-DC conversion circuit.
Preferably, the resonant inductive element is coupled in series with the capacitive element such that the full bridge DC-AC conversion circuit operates at ZVS in both the full bridge mode and the half bridge mode. It does not require complex controls, which helps to reduce costs and is easy to implement. When the DC-DC conversion circuit is operated away from the design point, the efficiency of the DC-DC conversion circuit may degrade, particularly for those circuits that employ soft switching techniques. Such a soft-switched DC-DC conversion circuit for example comprises a resonant inductive element L coupled in series with a capacitive element C, such that the full-bridge DC-AC conversion circuit operates in ZVS in both full-bridge and half-bridge mode. The switching frequency of each LLC converter is a function of the input voltage, the output voltage, and the output current. In general, the switching frequency increases both with increasing input voltage and with decreasing output voltage and output current. The result is that more heat will be generated and a stronger/larger cooling system is required, which results in higher costs. The DC-DC converter circuit according to the invention always operates at a design point with a fixed switching frequency and a constant duty cycle in order to ensure relatively low losses and to ensure relatively easy implementation between different output voltages and currents. By changing the converter from the full-bridge configuration mode to the half-bridge configuration mode, the voltage gain of the converter can be reduced by half and vice versa. Thus, the need for a cooling system may be reduced. In summary, the proposed solution can achieve lower costs and higher efficiency than prior art solutions.
Drawings
The subject matter of the invention will be explained in more detail hereinafter with reference to preferred exemplary embodiments shown in the drawings, in which:
FIG. 1 illustrates an AC-DC power converter according to an embodiment of the present invention, as shown; and
fig. 2A, 2B and 2C illustrate transitions between a full-bridge mode and a half-bridge mode of a full-bridge DC-AC conversion circuit according to an embodiment of the present invention.
The reference symbols used in the drawings and their meanings are listed in the list of reference symbols in summary form. In principle, identical components have the same reference numerals in the figures.
Detailed Description
Fig. 1 shows an AC-DC power converter according to an embodiment of the present invention. As shown in fig. 1, the AC-DC power converter 1 includes an AC-DC conversion circuit 10, a plurality of DC-DC conversion circuits 11, and a controller 12.
The AC-DC conversion circuit 10 is configured to receive a first AC power source FA and output a first DC power FD generated from the first AC power source FA. The first AC power FA may be supplied from an external AC power at the AC voltage Vin. In this embodiment, the AC-DC conversion circuit 10 may be a single-phase or three-phase controllable rectifier with a first controllable power switch. For example, the AC-DC conversion circuit 10 may be a three-phase bridge rectifier, such as a thyristor, with a first controllable power switch S11, S12, S13, S14 for each of the six arms of the bridge. The extinction angle can be adjusted by adjusting a control signal from the controller 12. Accordingly, the AC-DC conversion circuit 10 may provide the first DC power FD at the variable DC output voltage Vdc. The DC side of the AC-DC converter circuits 10 is coupled in parallel across the DC sides of the plurality of DC-DC converter circuits 11. In this embodiment, the number of the DC-DC conversion circuits 11 is two, and it will be understood by those skilled in the art that more than two DC-DC conversion circuits 11 may be applied.
Each of the DC-DC conversion circuits 11 has an intermediate conversion to the second AC power supply SA. Specifically, the DC-DC conversion circuit 11 has a DC-AC stage, a transformer, and an AC-DC stage, and the second AC power SA is output from the DC-AC stage as a power flow within the DC-DC conversion circuit 11. The DC-DC conversion circuit 11 is configured to receive the first DC power FD and combine the second DC power SD output at a DC output voltage Udc, which will be described in detail later. Each of the DC-DC conversion circuits 11 comprises a full bridge DC-AC conversion circuit 110(DC-AC stage) with second controllable power switches S21, S22, S23, S24, and the DC side of the full bridge DC-AC conversion circuit 110 is coupled across the outputs of the AC-DC conversion circuit 10. The DC-AC conversion circuit 110 includes a capacitive element C interposed between both ends of the AC side thereof. In this embodiment, the capacitive element C is coupled in series to the primary winding PW of the transformer 111 of the DC-DC conversion circuit 11, and the AC side of the DC-AC conversion circuit 110 is coupled across the series-linked capacitive element C and the primary winding PW of the transformer 111. Configured to generate a second DC power source from a plurality of outputs of a DC-DC power conversion from a first DC power source, wherein each of the plurality of DC-DC power conversions has an intermediate power conversion to the second AC power source through a capacitive element and is implemented in a full-bridge mode or a half-bridge mode such that the plurality of DC-DC power conversions exhibit multi-level voltage gain.
The controller 12 is configured to generate a first control signal for switching on and off the first controllable power switch of the AC-DC converter circuit 10 and to generate a plurality of second control signals, each of which is used to switch on and off the second controllable power switch of a corresponding full bridge DC-AC converter circuit 110 of the DC-DC converter circuit 11. As a result, the DC output voltage of the AC-DC conversion circuit 10 can be adjusted by changing the first control signal, and the AC output voltage of the full-bridge DC-AC conversion circuit 110 can be adjusted by changing the second control signal, and the DC output voltage Udc of the DC-DC conversion circuit 11 can also be adjusted because the rectifier 112 can be adjusted.
Fig. 2A, 2B and 2C illustrate transitions between a full-bridge mode and a half-bridge mode of a full-bridge DC-AC conversion circuit according to an embodiment of the present invention. Fig. 2A shows a circuit diagram of a full-bridge DC-AC conversion circuit operating in full-bridge mode.
As shown in fig. 2A, in the full-bridge mode, the controller 12 may send a second control signal to simultaneously switch the second controllable power switches S21 and S23 and the second controllable power switches S22 and S24 in a complementary manner. As a result, each of the second controllable power switches S21, S23, S22, and S24 may operate at a duty cycle of 50% and a switching frequency of 20kHz, as shown in fig. 2C. In full bridge mode, the second controllable power switches S21 to S24 may be operated at a fixed switching frequency of 20kHz and a duty cycle of 50%. During the transition, the second controllable power switches S21 and S22 continue to operate at a fixed switching frequency and 50% duty cycle to maintain the output value at the desired level, while the PWM modulation monotonically increases the duty cycle of switch S23 from 50% to 100% and decreases the duty cycle of switch S24 from 50% to 0% in a complementary manner. The current I flowing in the switch is indicated by an arrow. Because switch S23 is permanently on and switch S24 is permanently off, the full bridge DC-AC conversion circuit 110 continues to operate in hall-bridge mode with fixed frequency control of switch S21 and switch S22 during the transition.
As shown in fig. 2B, in the half-bridge mode, the controller 12 may send a second control signal to switch the second controllable power switches S21 and S22 of the first branch in a complementary manner. Further, each of them may operate at a 50% duty cycle and a 20kHz switching frequency, as shown in fig. 2C. One of the second controllable power switches S24 in the second branch is continuously on, while the other second controllable power switch S23 in the second branch is continuously off. However, other synchronization methods are possible. For example, the second controllable power switches S22 and S24 may be synchronized for turn-on, the second controllable power switches S21 and S23 may be synchronized in the middle of a turn-on time, or the second controllable power switches S22 and S24 may be synchronized in the middle of a turn-off time.
Further, the full bridge DC-AC conversion circuit 110 may operate in an OFF (OFF) mode, in which control is achieved by turning OFF all of its second controllable power switches S21-S24, each switch operating at a 0% duty cycle.
The second controllable power switches S21-S24 of the circuits of fig. 2A and 2B block voltage in one direction and conduct current in two directions. Typically, each of the switches S21-S24 is implemented by a second switch which is a controllable unidirectional power semiconductor switch with an anti-parallel uncontrolled unidirectional current carrying semiconductor, such as an IGBT and a MOSFET, whose structure includes an anti-parallel body diode that allows bidirectional current flow. Accordingly, the full-bridge DC-AC conversion circuit 110 may operate in a full-bridge mode or a half-bridge mode depending on the second control signal provided by the controller 12. For the transition from half-bridge mode to full-bridge mode, switches S23 and S24 are modulated in a direction substantially opposite to the direction of the transition from full-bridge mode to half-bridge mode, i.e., the duty cycle of switch S23 is monotonically decreased from 100% (i.e., continuously on) to 50%, while the duty cycle of switch S24 is increased from 0% (i.e., continuously off) in a complementary manner.
From the static analysis, the average voltage of the capacitive element C is zero in the full-bridge mode. Correspondingly, in the half-bridge mode, the average voltage of the capacitive element is Vdc/2. In this embodiment, when two DC-DC conversion circuits 11 are used in one system, five different operation modes can be obtained. The five different operating modes are full mode, full half mode, half mode, full off mode and half off mode. When the two DC-DC conversion circuits 11 are operated in full bridge mode with a fixed switching frequency and duty cycle, the converters have a joint voltage gain, M ═ 1. Similarly, for the half-bridge mode with fixed switching frequency and duty cycle, the voltage gain is 0.5. When it is in the off mode, the voltage gain is 0. Therefore, when the input of the DC-DC conversion circuit 11 is coupled in parallel across the output DC voltage Vdc of the AC-DC conversion circuit 10 and the output of the DC-DC conversion circuit 11 is coupled in series, 4 possible stage voltage gains 2, 1.5, 1, and 0.5 may be obtained, exhibiting a multi-stage voltage gain of the DC-DC conversion circuit 11. Since the DC-DC converter circuit 11 has 4 fixed-stage voltage gains, its DC output voltage is adjusted by changing the DC input voltage, which is the output voltage of the AC-DC converter circuit 10.
In this embodiment, the controller 12 may regulate the DC voltage Vdc of the first DC power FD output from the AC-DC conversion circuit 10 within a DC voltage range by simultaneously switching the first controllable power switches S11 and S13 and the first controllable power switches S12 and S14 in a complementary manner, each switch operating at a duty cycle ranging from 0% to 100%. Alternatively, assuming that the AC-DC conversion circuit 10 employs a half-bridge topology, it will be appreciated by those skilled in the art that its output DC voltage Vdc may be regulated by appropriately controlling the duty cycle of its switches.
The DC voltage range of the AC-DC conversion circuit 10 is set to cover the voltage increase of two consecutive stages of voltage gain. Under the control of the controller 12, the power conversion is regulated by the AC-DC conversion circuit 10, tuning its DC output voltage Vdc, which thus varies within a relatively small range. The output from the AC-DC converter circuit 10 is fed in parallel to the input of the DC-DC converter circuit 11, converted by them respectively at a fixed switching frequency and duty operation and output at their series-linked output terminals. The voltage gain of each DC-DC conversion circuit 11 is variable according to a full bridge mode, a half bridge mode, or an off mode, so that the output voltage of the DC-DC conversion circuit 11 can be varied in discrete levels with relatively large intervals therebetween, exhibiting various voltage gains of 0.5, 1, 1.5, and 2. Assuming that the DC output voltage Vdc of the AC-DC conversion circuit 10 input to the DC-DC conversion circuit 11 remains substantially constant, the gap between two consecutive voltage gains is 0.5, which makes the output DC voltage Vo of the AC-DC converter 1 discrete. As in the above method, the DC output voltage Vdc of the AC-DC converter circuit 10 can be adjusted by changing its duty ratio, and thus it is variable within the DC voltage range [ Vdc _1, Vdc _2], and the distribution of the output DC voltage Vo of the AC-DC converter 1 for both end points is as shown in table I:
TABLE I
Those skilled in the art will appreciate that the AC-DC conversion circuit 10 may be regulated by the controller 12, for example, by varying the duty cycle of its switches, so as to supply a DC output voltage Vdc that continuously increases from a lower endpoint Vdc _1 to a higher endpoint Vdc _ 2. Thus, two adjacent discrete levels, e.g., voltage gaps between HO and HH, HH and FH, FO and FH, and FH and FF, can bridge the DC output voltage Vdc of AC-DC conversion circuit 10 continuously from Vdc _1 to Vdc _2 as long as Vdc _2-Vdc _1 is greater than or equal to 0.5 Vdc _ 1.
By having an AC-DC converter according to the invention, no complex control is required, which contributes to cost reduction and ease of implementation. When a DC-DC converter circuit is operated away from the design point, its efficiency degrades, especially for those circuits that use soft switching techniques. Such soft-switched DC-DC conversion circuits comprise, for example, a resonant inductive element L coupled in series with a capacitive element C, such that the full-bridge DC-AC conversion circuit operates in ZVS in both full-bridge and half-bridge mode. The switching frequency of each LLC converter is a function of the input voltage Vin, the output voltage Vo, and the output current. In general, the switching frequency increases both with increasing input voltage and with decreasing output voltage and output current. As a result, more heat will be generated and a stronger/larger cooling system is required, which results in higher costs. The DC-DC converter circuit according to the invention always operates at a design point with a fixed switching frequency and a constant duty cycle in order to ensure relatively low losses and to ensure relatively easy implementation between different output voltages and currents. For example, when the DC-DC conversion circuit is an LLC resonant topology, the DC-DC conversion circuit will always switch around its resonant frequency, enabling the switching losses to be minimized over a wide output range. By changing the converter from the full-bridge configuration mode to the half-bridge configuration mode, the voltage gain of the converter can be reduced by half and vice versa.
Thus, the need for a cooling system may be reduced. In summary, the proposed solution may achieve lower costs and higher efficiency than prior art solutions. For applications requiring a relatively wide voltage range such as the DC fast charger of the electric vehicle of today, in order to maintain high power efficiency over a wide voltage range, a plurality of DC-DC conversion circuits are linked in parallel at their input terminals, and any one of the DC-DC conversion circuits needs to take part of the responsibility for voltage regulation, while both DC-DC conversion circuits operate at their design points to ensure high efficiency.
Further, when the two DC-DC conversion circuits are switched with a 90-degree phase shift, the high-frequency output voltage ripple at the output terminal can be significantly reduced. Since the size of the high frequency component is small, the size and cost of the output filter can be reduced.
Although the present invention has been described based on some preferred embodiments, those skilled in the art will appreciate that those embodiments should in no way limit the scope of the present invention. Any variations and modifications of the embodiments herein described should be understood by those having ordinary skill in the art without departing from the spirit and concepts of the present invention, and therefore fall within the scope of the present invention as defined by the appended claims.
Claims (8)
1. An AC-DC power converter comprising:
an AC-DC conversion circuit having a first controllable power switch, the AC-DC conversion circuit configured to receive a first AC power source and output a first DC power source generated from the first AC power source;
a plurality of DC-DC conversion circuits, each of the plurality of DC-DC conversion circuits having an intermediate conversion to a second AC power source, the plurality of DC-DC conversion circuits configured to receive the first DC power source and combine the second DC power source outputs in a series coupling, wherein each of the plurality of DC-DC conversion circuits comprises a full bridge DC-AC conversion circuit having a second controllable power switch, a DC side thereof coupled across an output of the AC-DC conversion circuit, and a capacitive element interposed between both ends of an AC side thereof; and
a controller configured to:
generating a first control signal for turning on and off the first controllable power switch of the AC-DC conversion circuit such that a DC voltage of the first DC power source is adjustable within a DC voltage range; and is
Generating a plurality of second control signals, each of the plurality of second control signals for turning on and off the second controllable power switch of a corresponding one of the plurality of DC-DC conversion circuits in a full-bridge mode and a half-bridge mode at a fixed switching frequency and duty cycle such that the plurality of DC-DC conversion circuits exhibit multiple levels of voltage gain;
wherein:
the DC voltage range of the AC-DC conversion circuit is set to cover voltage increases from two consecutive stages of the voltage gain.
2. The AC-DC power converter of claim 1, wherein:
in the full-bridge mode, each of the second controllable power switches in the first and second legs of the full-bridge DC-AC conversion circuit operates at substantially the same duty cycle and substantially the same switching frequency; and is
In the half-bridge mode, each of the second controllable power switches in the first branch operates at substantially the same duty cycle and substantially the same switching frequency, and one of the second controllable power switches in the second branch is continuously on and the other of the second branch is continuously off.
3. An AC-DC power converter according to any of the preceding claims 1-2, wherein:
the second controllable power switch is a controllable unidirectional power semiconductor switch having an anti-parallel uncontrolled unidirectional current carrying semiconductor.
4. An AC-DC power converter according to any of the preceding claims 1-2, further comprising:
a resonant inductive element coupled in series with the capacitive element such that the full-bridge DC-AC conversion circuit operates in ZVS in both the full-bridge mode and the half-bridge mode.
5. An AC-DC power converter according to claim 3, further comprising:
a resonant inductive element coupled in series with the capacitive element such that the full-bridge DC-AC conversion circuit operates in ZVS in both the full-bridge mode and the half-bridge mode.
6. A method for operating an AC-DC power converter, the method comprising:
generating a first DC power source having an adjustable DC voltage range from a first AC power source; and
combining in a series-coupled manner a plurality of outputs of a plurality of DC-DC power conversions from the first DC power source to produce a second DC power source, wherein each of the plurality of DC-DC power conversions has an intermediate power conversion to a second AC power source through a capacitive element and is implemented in a full-bridge mode or a half-bridge mode at a fixed switching frequency and duty cycle such that the plurality of DC-DC power conversions exhibits a multi-level voltage gain;
wherein:
the DC voltage range is adjusted to cover the voltage increase of two consecutive stages of the voltage gain.
7. The method of claim 6, wherein:
in the full-bridge mode, each of the plurality of DC-DC power conversions operates at substantially the same duty cycle and substantially the same switching frequency; and is
In the half-bridge mode, each of the plurality of DC-DC power conversions operates at the substantially same duty cycle and the substantially same switching frequency.
8. The method of any of the preceding claims 6-7, wherein:
a resonant inductive element is coupled in series with the capacitive element such that the intermediate power source converted full bridge DC-AC conversion circuit operates at ZVS in both the full bridge mode and the half bridge mode.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/CN2016/083883 WO2017206011A1 (en) | 2016-05-30 | 2016-05-30 | Ac-dc power converter and method therefor |
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| CN109196768A CN109196768A (en) | 2019-01-11 |
| CN109196768B true CN109196768B (en) | 2021-01-15 |
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|---|---|---|---|---|
| US10224827B1 (en) | 2018-02-15 | 2019-03-05 | Futurewei Technologies, Inc. | Power converter with wide DC voltage range |
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| CN104734520A (en) * | 2015-03-23 | 2015-06-24 | 深圳市皓文电子有限公司 | DC/DC converter |
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| CN203775072U (en) * | 2014-02-14 | 2014-08-13 | 福州开发区星云电子自动化有限公司 | Multichannel energy-bidirectional cell tester |
| CN203967994U (en) * | 2014-05-30 | 2014-11-26 | 山东大学 | Unity power factor single-stage AC-DC converter |
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