CN104011986B - LLC two-way resonance changer and control method - Google Patents

Abstract

An LLC bidirectional resonant converter includes: a resonant tank, a first switching circuit connected to the resonant tank via a first power conduit, a second switching circuit connected to the resonant tank via a second power conduit, a switching element, and at least one a switchable inductive element, the at least one switchable inductive element being arranged in parallel across the second power conduit by a switching element when operating in the first mode of operation, the at least one switchable inductive element being arranged in parallel across the second power conduit when operating in the second mode of operation Elements are arranged in parallel across the first power conduit by switching elements.

Description

LLC bidirectional resonant converter and control method

technical field

The invention relates to an LLC bidirectional resonant converter and a method of controlling a bidirectional resonant converter. In particular, the invention relates to an LLC bidirectional resonant converter with inductive elements arranged across a first or second power conduit depending on the mode of operation, and a method of controlling said LLC bidirectional resonant converter.

Background technique

In the history of the development of switched-mode power systems (SMPS) or resonant converters, the complexity of the rectifier circuit side of the converter has increased.

In a conventional resonant SMPS, the rectification circuit portion of the SMPS includes conventional semiconductor diode rectification components that rectify the voltage signal generated by the resonant tank portion of the converter. In order to control the output voltage of the converter, the switching frequency of the resonant tank is constantly changed.

To make this form of converter more efficient, synchronous rectification is introduced. Synchronous rectification involves placing a semiconductor switch in parallel with (or replacing) a conventional rectifier diode. Typically the semiconductor switches are MOSFET (Metal Oxide Semiconductor Field Effect Transistor) devices. However, the MOSFET device can be replaced by an IGBT (Insulated Gate Bipolar Transistor) device or a number of alternatives.

For example, Figure 1 shows a typical SR circuit. The resonant tank 101 composed of a capacitive element and an inductive element connected in series receives power from a power source 103 via a switch circuit 105 . A shunt inductor 106 is placed in parallel across the primary winding of an isolation transformer 107 . The output of the isolation transformer 107 includes a synchronous rectification switching device 109 which provides output power to a load 113 via a smoothing capacitor 111 .

Such LLC circuits are able to provide output voltage control by operating in the buck or boost region. Further, the recent move to such output synchronous rectification in industry standard practice has resulted in the ability to provide bi-directional power conversion. It has been found that conventional LLC series resonant circuits have an asymmetric transfer function, where the input-output transfer function (ie, forward transfer function) is different from the output-input transfer function (ie, reverse transfer function).

However, it has been found that the reverse transfer function does not facilitate practical reverse power flow control. For example, an inductive loading provided across a source does not provide any useful function if the power flow is reversed.

It is an object of the present invention to provide an LLC bidirectional resonant converter with improved forward and reverse power flow control, or at least to provide the public with a useful choice.

The present invention aims to overcome, or at least alleviate some or all of the above problems.

Further objects and advantages of the present invention will be provided in the following part of the description, wherein the detailed description is for the purpose of fully disclosing the preferred embodiments of the present invention and not imposing any limitation thereon.

The background discussion (including any potential prior art) is not to be taken as an admission of common general knowledge in the art in any country. Any references discussed state what the author asserts about those references, and do not assert what the applicant has asserted about the present application. Applicants therefore reserve the right to question the accuracy and pertinence of the discussions presented.

Contents of the invention

It is generally recognized that the terms "comprises", "comprises" and "containing" are assigned an exclusive or inclusive meaning in different jurisdictions. For purposes of this specification, unless otherwise indicated, these terms are intended to have an inclusive meaning—that is, they are considered to include the listed components to which the direct use references, but may also optionally mean the inclusion of other unspecified components. or components. It will be understood that this literal meaning also applies analogously to terms mentioned when used to define method or process steps.

It will be understood that when describing various integers (eg, modules, components, elements, etc.), any integer may consist of a single integer or a plurality of integers.

According to one aspect, the present invention provides an LLC bidirectional resonant converter, which includes: a resonant tank, a first switching circuit connected to the resonant tank via a first power conduit, and a second switching circuit connected to the resonant tank via a second power conduit. a resonant tank, a switching element, and at least one switchable inductive element arranged by the switching element in parallel across a second power conduit when operating in a first mode of operation, and when operating in a second mode mode, the at least one switchable inductive element is arranged by the switching element in parallel across the first power conduit.

According to a second aspect, the present invention provides a method of controlling an LLC bidirectional resonant converter, comprising the steps of: switching the bidirectional resonant converter between a first mode of operation and a second mode of operation, in the first mode of operation, bidirectional The resonant converter is arranged to operate in a forward power transfer mode, and in a second operation mode, the bidirectional resonant converter is arranged to operate in a reverse power transfer mode, and the switching element is controlled based on the operation mode when the bidirectional resonant converter operates , wherein the switching element is arranged to span the first power conduit between the first switching circuit and the resonant tank or the second power conduit between the resonant tank and the second switching circuit depending on the mode of operation in which the bidirectional resonant converter operates Connect at least one inductive element in parallel.

Description of drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a known resonant converter circuit;

2A shows a conceptual diagram of a bidirectional resonant converter operating in a first mode of operation according to an embodiment of the present invention;

2B shows a conceptual diagram of a bidirectional resonant converter operating in a second mode of operation according to an embodiment of the present invention;

3 shows a block circuit diagram of a bidirectional resonant converter operating in a first mode of operation according to an embodiment of the present invention;

4 shows a block circuit diagram of a bidirectional resonant converter operating in a second mode of operation according to an embodiment of the present invention;

5 shows a circuit diagram of a bidirectional resonant converter according to an embodiment of the present invention;

6 shows a circuit diagram of a bidirectional resonant converter according to an embodiment of the present invention;

FIG. 7A shows a configuration diagram of a bidirectional resonant converter according to an embodiment of the present invention;

FIG. 7B shows a configuration diagram of a bidirectional resonant converter according to an embodiment of the present invention;

FIG. 7C shows a configuration diagram of a bidirectional resonant converter according to an embodiment of the present invention;

Figure 7D shows a configuration diagram of a bidirectional resonant converter according to an embodiment of the present invention; and

FIG. 7E shows a configuration diagram of a bidirectional resonant converter according to an embodiment of the present invention.

detailed description

first embodiment

FIG. 2A shows a conceptual diagram of a bidirectional resonant converter operating in a first mode of operation according to this embodiment.

The resonant tank 201 is connected to a first switching arrangement 203 via a first set of power conduits 205 . The resonance tank 201 is also connected to a second switching arrangement 207 via a second set of power conduits 209 .

In a first mode of operation, the bidirectional resonant converter is set to operate in a forward power transfer mode, where power is transferred in the direction of the arrows indicated in Figure 2A, i.e. from the second switch arrangement 203 to the resonant tank 201, and then to the second switching arrangement 207 . When the resonant converter is operating in the first mode, the first switching arrangement 203 controls the power supplied to the resonant tank and the second switching arrangement 207 operates as a synchronous rectifier.

FIG. 2B shows a conceptual diagram of a bidirectional resonant converter operating in a second mode of operation.

The resonant tank 201 is still connected to the first switching arrangement 203 via the first set of power conduits 205 . The resonant tank 201 is further still connected to a second switching arrangement 207 via a second set of power conduits 209 . However, in this second mode of operation, the bidirectional resonant converter is arranged to operate in a reverse power transfer mode, where power is transferred in the direction of the arrow indicated in Figure 2B, i.e. from the second switching arrangement 207 to the resonant tank 207 , and then transmitted to the first switch arrangement 203 . When the converter is placed in this second mode, the second switching arrangement 207 controls the power supplied to the resonant tank and the first switching arrangement 203 operates as a synchronous rectifier.

Fig. 3 shows a block circuit diagram of a bidirectional resonant converter operating in a first mode of operation.

The resonant tank 201 is shown connected to a first switching arrangement 203 . A resonant shunt inductor 301 is arranged in parallel across the second set of power conduits. That is, the resonant shunt inductor 301 is effectively arranged in parallel across the second switch arrangement 207 . Power from the power supply 303 is switched to drive the resonant tank 201 through the first switching arrangement 203 .

According to this embodiment, an isolation transformer 305 is provided to transfer power from the resonant tank to the second switching arrangement. An isolation transformer isolates the resonant tank and the first switch arrangement from the second switch arrangement 207 and the load 307 . It will be understood, however, that as an alternative, the isolation transformer may be an autotransformer if primary to secondary voltage/current conversion is required, but isolation is not required. As a further alternative, the second switching arrangement may be connected directly to the resonant circuit if no primary to secondary voltage/current conversion is required.

Forward power transfer is indicated by arrow 309 .

Fig. 4 shows a block circuit diagram of a bidirectional resonant converter operating in a second mode of operation.

In this second mode of operation, the bidirectional resonant converter operates in reverse power transfer mode. Therefore, the original power source 303 becomes the load 311 , and the original load 307 becomes the new power source 313 . A resonant shunt inductor 314 is arranged in parallel across the first set of power conduits. That is, the resonant shunt inductor 314 is effectively arranged in parallel across the first switch arrangement 203 . Power from the new power supply 313 is switched via the second switching arrangement 207 to drive the resonant tank 201 .

Reverse power transfer is indicated by arrow 315 .

As shown in Figure 3, in the first mode of operation the first switch arrangement 203 is controlled using a first switching sequence. Further, in this first mode of operation, the second switch arrangement 207 is controlled using a second switching sequence.

As shown in Figure 4, in the second mode of operation, the first switch arrangement 203 is controlled using a third switching sequence. Further, in this second mode of operation, the second switch arrangement 207 is controlled using a fourth switching sequence.

It will be appreciated that the first and fourth switching sequences are used to control the amount of power applied to the resonant tank 201 and the second and third switching sequences are used to synchronize the output of the rectification circuit.

Fig. 5 shows a circuit diagram of a bidirectional resonant converter according to this embodiment of the present invention.

The resonance tank 501 includes an inductance element and a capacitance element arranged in series. A power supply 503 provides power to the resonant tank 501 via a first switching arrangement 505 .

According to this embodiment, the first switch arrangement 505 may be a half bridge arrangement comprising two MOSFET (Metal Oxide Semiconductor Field Effect Transistor) devices.

It will be appreciated that alternative devices such as IGBT (Insulated Gate Bipolar Transistor) devices or alternative devices may be used for synchronous rectification.

It will also be understood that the first switch arrangement may be modified to take the form of a full bridge drive circuit. Further, the drive circuit may be configured to switch using zero voltage transition (ZVT).

The primary winding on isolation transformer 507 receives the output from the resonant tank. An isolation transformer 507 enables power to be transferred from the resonant tank 501 to the output side of the circuit. On the secondary winding side of the isolation transformer 507 there is a half bridge switch arrangement 509 for rectifying the signal output from the isolation transformer. The signal output from the isolation transformer is smoothed by a smoothing capacitor 511 and then supplied to a load 513 . It will be appreciated that, as an alternative, the half-bridge switching arrangement may be replaced by a full-bridge switching arrangement.

According to this embodiment, a single switchable inductive element 515 in the form of a resonant shunt inductor is provided. A single pole single throw relay switch 517 is provided and controlled such that the inductive element 515 can be placed across the primary winding of the isolation transformer 507, i.e. in parallel across the output of the resonant tank, when the resonant converter is in the first mode of operation Inductive element 515 . That is, a resonant shunt inductor is placed in the circuit so that it is connected in parallel across the second set of power conduits 209 .

It will be appreciated that the inductive element may consist of one or more inductive elements.

In the second mode of operation, the single pole single throw relay switch 517 is controlled to enable the placement of the inductive element 515 across the input of the resonant tank 501 . Referring to FIGS. 2A and 2B , a shunt inductor is placed in the circuit so that it is connected in parallel across the first set of power conduits 205 .

Thus, in the first mode of operation, the resonant converter is set to operate in a forward power transfer mode. The switchable inductive element 515 affects the power transferred through the resonant tank by providing a low loss inductive load on the output of the converter which is the second set of power conduits 209 .

In the second mode of operation, the resonant converter is arranged to operate in a reverse power transfer mode. The switchable inductive element 515 affects the power transferred through the resonant tank by providing a low loss inductive load on the output of the converter which is the first set of power conduits 205 .

It will be appreciated that typical values for the switchable inductive element may be selected based on the desired forward and reverse transfer characteristics of the resonant converter.

Further, it will be appreciated that, alternatively, the one or more inductive elements switched across the first set of power conduits may be different components that may be different from the one or more inductive elements switched across the second set of power conduits. have the same or different values. In this manner, component values can be selected to provide independent control of desired forward and reverse transfer characteristics.

further embodiment

Fig. 6 shows a circuit diagram of a bidirectional resonant converter according to a further embodiment of the present invention.

According to this further embodiment, a similar arrangement is provided with respect to the resonant tank 601 , the power supply 603 , the first switch arrangement 605 , the isolation transformer 607 and the second switch arrangement 609 . However, according to this embodiment, the first and second switching arrangements are arranged as full bridge switching circuits.

7A-7E illustrate various LC arrangements of resonant tanks of bidirectional resonant converters according to further embodiments of the present invention. For example, depending on practical considerations, it may be preferable from a design point of view to choose to place the inductor and capacitor components of the resonant tank on a particular side of the transformer.

From Fig. 7A, it can be seen that the LC part of the resonant tank 701 is located on the primary side of the transformer, as described above in the first embodiment. The switchable inductive element 703 is arranged to be placed across the first power conduit or across the second power conduit, as shown in Figures 2A and 2B.

According to FIG. 7B , the two LC components of the resonant tank 701 and the switchable inductive element 703 are located on the secondary side of the transformer.

According to Fig. 7C, a non-isolated version of the converter is shown, in which no transformer is provided to separate the input side from the output side.

According to Fig. 7D, the inductive part 705 of the resonant tank is located on the primary side of the transformer 711 and the capacitive part 707 of the resonant tank is located on the secondary side of the transformer. The switchable inductive element 709 comprises a double pole double throw relay configured to place the switchable inductive element across a second set of power conduits located on the secondary side of the transformer, or across a first set of power conduits The first set of power conduits is located on the primary side of the transformer. That is, both ends of the switchable inductive element are switched across both sides of the transformer boundary. According to this example, the transformer has a winding turns ratio of 1:1. It will be appreciated that alternative inductance values may be required if the turns ratio is changed from 1:1.

According to Fig. 7E, the capacitive part 707 of the resonant tank is located on the primary side of the transformer 711 and the inductive part 705 of the resonant tank is located on the secondary side of the transformer. The switchable inductive element 709 comprises a double pole double throw relay such that the switchable inductive element is placed across a second set of power conduits on the secondary side of the transformer or across a first set of power conduits. The first set of power conduits is located on the primary side of the transformer. That is, both ends of the switchable inductive element are switched across both sides of the transformer boundary. According to this example, the transformer has a winding turns ratio of 1:1. It will be appreciated that alternative inductance values may be required if the turns ratio is changed from 1:1.

It will be understood that the embodiments of the invention described herein are by way of example only, and that various changes and modifications may be made without departing from the scope of the invention.

Claims (22)

1. A LLC bidirectional resonant converter, comprising: resonance tank, a first switching circuit connected to the resonant tank via a first power conduit, a second switching circuit connected to the resonant tank via a second power conduit, switching elements, and at least one switchable inductive element arranged by said switching element in parallel across said second power conduit when operating in a first mode of operation, and when operating in a second mode of operation , the at least one switchable inductive element is arranged in parallel across the first power conduit via the switching element. 2. The bidirectional resonant converter of claim 1 , wherein when operating the bidirectional resonant converter in the first mode of operation, power is transferred from the first switching circuit via the first power conduit transmits power to the resonant tank, and transmits power from the resonant tank to the second switching circuit via the second power conduit, and When operating the bidirectional resonant converter in the second mode of operation, power is transferred from the second switching circuit to the resonant tank via the second power conduit, and to the resonant tank via the first power conduit Power is transferred from the resonant tank to the first switching circuit. 3. The bidirectional resonant converter according to claim 1, wherein, When operating the bidirectional resonant converter in the first mode of operation, the first switching circuit is arranged to switch according to a first switching sequence, and the second switching circuit is arranged to switch according to a second switching sequence , When operating the bidirectional resonant converter in the second operating mode, the first switching circuit is arranged to switch according to a third switching sequence and the second switching circuit is arranged to switch according to a fourth switching sequence. 4. The bidirectional resonant converter according to claim 1, wherein the resonant tank comprises a resonant capacitive element in series with a resonant inductive element. 5. The bidirectional resonant converter according to claim 1, wherein, in a first mode of operation, the bidirectional resonant converter operates in a forward power transfer mode, and in a second mode of operation, the bidirectional resonant converter The converter operates in reverse power transfer mode. 6. The bidirectional resonant converter of claim 1, wherein the second switching circuit is arranged as a first rectifier circuit during the first mode of operation. 7. The bidirectional resonant converter of claim 6, wherein the first rectifier circuit is a first synchronous rectifier circuit switched according to the second switching sequence. 8. The bidirectional resonant converter of claim 1, wherein the first switching circuit is arranged as a second rectifier circuit during the second mode of operation. 9. The bidirectional resonant converter of claim 8, wherein the second rectifier circuit is a second synchronous rectifier circuit switched according to a fourth switching sequence. 10. The bidirectional resonant converter according to claim 1, further comprising a transformer disposed between the resonant tank and the second switching circuit. 11. The bidirectional resonant converter according to claim 1, further comprising a transformer disposed between the first switching circuit and the resonant tank. 12. The bidirectional resonant converter according to claim 10 or 11, wherein the transformer is one of an isolation transformer and an autotransformer. 13. A bidirectional resonant converter according to claim 10 or 11, wherein the resonant tank comprises a resonant capacitive element connected in series with a resonant inductive element. 14. The bidirectional resonant converter according to claim 13, wherein the resonant capacitive element and the resonant inductive element are connected in series on the primary side of the transformer. 15. The bidirectional resonant converter according to claim 13, wherein the resonant capacitive element and the resonant inductive element are connected in series on the secondary side of the transformer. 16. The bidirectional resonant converter of claim 13, wherein the resonant inductive element is located on the primary side of the transformer, and the resonant capacitive element is located in series on the secondary side of the transformer. 17. The bidirectional resonant converter of claim 13, wherein the resonant inductive element is located on the secondary side of the transformer, and the resonant capacitive element is located in series on the primary side of the transformer. 18. The bidirectional resonant converter according to claim 1, wherein the first and/or second switching circuit is configured as a half-bridge driving circuit. 19. The bidirectional resonant converter according to claim 1, wherein the first and/or second switching circuit is configured as a full bridge driving circuit. 20. The bidirectional resonant converter according to claim 1, wherein the first and/or second switching circuits are configured as push-pull driving circuits. 21. The bidirectional resonant converter according to claim 1, wherein the first and/or second switching circuits employ ZVT switching. 22. A method for controlling an LLC bidirectional resonant converter, the method comprising the steps of: switching the bidirectional resonant converter between a first mode of operation in which the bidirectional resonant converter is set to operate in a forward power transfer mode and a second mode of operation in which In the second mode of operation, the bidirectional resonant converter is configured to operate in a reverse power transfer mode, and the switching element is controlled based on the operating mode in which the bidirectional resonant converter is operating, wherein the switching element is configured to depend on the In the operation mode when the bidirectional resonant converter operates, at least one inductor is connected in parallel across the first power conduit between the first switching circuit and the resonant tank or the second power conduit between the resonant tank and the second switching circuit element.