Bidirectional flyback converter using full bridge circuit

Abstract

A bidirectional flyback converter using a full bridge circuit is disclosed. The flyback converter includes: a transformer; a primary-side circuit located on a primary side of the transformer and having a first switching unit; and a secondary-side circuit located on a secondary side of the transformer and having a second switching unit. Here, each of the first switching unit and the second switching unit is implemented with two bridge circuits and a capacitor between the bridge circuits.

Description

Bidirectional flyback converter using full bridge circuit

[0001] The present invention relates to a bidirectional flyback converter using a full bridge circuit.

[0002] Onboard chargers (OBCs) require high power density, efficiency, and miniaturization, and active research is being conducted to increase the capacity of OBCs to increase charging speed.

[0003] In general, the DC / DC converter used in the above OBC uses a resonant converter such as a PWM resonant converter, but there are problems such as a complex design procedure and a disadvantage in bidirectional gain design.

[0004] The present invention provides a bidirectional flyback converter using a full bridge circuit, characterized in that the switching sections of the primary and secondary sides of a transformer are each implemented with two bridge circuits and a capacitor between the bridge circuits.

[0005] In order to achieve the above-described object, a flyback converter according to one embodiment of the present invention includes: a transformer; a primary circuit located on the primary side of the transformer and having a first switching section; and a secondary circuit located on the secondary side of the transformer and having a second switching section. Here, the first switching section and the second switching section are each implemented as two bridge circuits and a capacitor between the bridge circuits.

[0006] According to another embodiment of the present invention, a flyback converter comprises: a transformer; a primary circuit located on a primary side of the transformer and having a first switching unit; and a secondary circuit located on a secondary side of the transformer and having a second switching unit. Here, the first switching unit includes a first switch and a second switch connected in series to a first node; and a third switch and a fourth switch connected in series to the first node, wherein the first switch and the second switch are connected in parallel with the third switch and the fourth switch based on the first node, and the first switch and the fourth switch are main switches, and the second switch and the third switch are clamp switches.

[0007] According to another embodiment of the present invention, a flyback converter comprises: a transformer; a primary circuit located on a primary side of the transformer and having a first switching unit; and a secondary circuit located on a secondary side of the transformer and having a second switching unit. Here, the second switching unit includes a fifth switch and a sixth switch connected in parallel to one end of the secondary side of the transformer; and a seventh switch and an eighth switch connected in parallel to the other end of the secondary side of the transformer, wherein the fifth switch and the eighth switch are main switches, and the sixth switch and the seventh switch are clamp switches.

[0008]

[0009] The flyback converter according to the present invention is implemented as a full bridge circuit in which the switching sections of the primary and secondary sides of the transformer each include two bridge circuits and a capacitor between the bridge circuits, thereby securing high capacity and implementing bidirectional operation.

[0010] Additionally, the flyback converter can utilize an active clamp circuit. Consequently, all switches can operate in zero-voltage switching (ZVS), achieving high efficiency and power density.

[0011] FIG. 1 is a circuit diagram illustrating a flyback converter according to one embodiment of the present invention.

[0012] FIG. 2 is a timing diagram illustrating the operation of a flyback converter according to one embodiment of the present invention.

[0013] FIGS. 3 to 8 are drawings illustrating the operation process of a flyback converter according to one embodiment of the present invention.

[0014] FIG. 9 is a graph showing the operating efficiency of a flyback converter according to one embodiment of the present invention.

[0015] As used herein, singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "consist of" or "include" should not be construed to necessarily include all components or steps described in the specification, and should be construed to mean that some of the components or steps may not be included, or that additional components or steps may be included. In addition, terms such as "part" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software, or by a combination of hardware and software.

[0016]

[0017] The present invention relates to a flyback converter, wherein both the primary and secondary circuits are implemented as full-bridge circuits and an active clamp circuit can be used. Consequently, the flyback converter can secure high capacity while realizing a wide output voltage range.

[0018] In addition, the flyback converter can be designed with a symmetrical structure for the primary circuit and the secondary circuit, thereby enabling bidirectional operation and realizing isolation and bidirectional equal gain between the circuits.

[0019]

[0020] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings.

[0021] FIG. 1 is a circuit diagram illustrating a flyback converter according to one embodiment of the present invention.

[0022] Referring to FIG. 1, the flyback converter of the present embodiment may be a DC / DC converter used, for example, in a charger of an onboard terminal (OBC).

[0023] This flyback converter is a bidirectional converter and may include a primary circuit (100), a transformer (102), and a secondary circuit (104).

[0024] The primary circuit (100) is powered by a power source (V in ) connected to the first switching unit (110), the first capacitor (C C 1), first inductor (L k ) and a second inductor (L m ) may be included.

[0025] According to one embodiment, the first switching unit (110) may be implemented as a full-bridge circuit. Specifically, the power supply (V in ) connected to a node (n1) and a power source (V in ) are connected in series with each other between the other ends of the first switch (M) 1a ) and the second switch (M 2b ) and power (V in ) connected to a node (n1) and a power source (V in ) connected in series with each other between the other ends of the third switch (M 2a ) and the 4th switch (M 1b ) may be included. Here, the first switch (M1a ) and the second switch (M 2b ) and the third switch (M 2a ) and the 4th switch (M 1b ) can be connected in parallel with each other based on node (n1).

[0026] Also, the first switch (M 1a ) / 4th switch (M 1b ) and the second switch (M 2b ) / 3rd switch (M 2a ) can perform complementary switching operations. At this time, the first switch (M 1a ) and the 4th switch (M 1b ) acts as the main switch and the second switch (M 2b ) and the third switch (M 2a ) can operate as a clamp switch. That is, the flyback converter may have an active clamp structure. This active clamp structure can recycle the energy stored in the leakage inductance by absorbing it with the clamp switch and capacitor, and can implement ZVS in all switches by enabling the discharge of the parasitic capacitor of the main switch. As a result, high efficiency and power density can be secured.

[0027] According to one embodiment, each switch (M 1a , M 2b , M 2a ,M 1b ) is a MOSFET and may include a body diode and parasitic capacitors. Consequently, the switch (M 1a , M 2b , M 2a ,M 1b ) may still flow through the internal diode even when it is turned off.

[0028] First capacitor (C C 1) is the first switch (M 1a ) and the third switch (M 2a ) can be connected between these first capacitors (C C1) is to replenish the required energy, switch (M 1a , M 2b , M 2a ,M 1b ) helps in implementing ZVS.

[0029] First inductor (L k ) is the first switch (M 1a ) and the second switch (M 2b ) is connected between the node (n2) and one end of the transformer (102) and can store energy.

[0030] Second inductor (L m ) is the first inductor (L k ) or can be connected between the node (n4) corresponding to one end of the transformer (102) and the other end of the transformer (102). That is, the second inductor (L m ) can be connected in parallel to the transformer (102), and the first inductor (L) is connected based on the node (n4). k ) can be connected in parallel.

[0031] Also, the third switch (M 2a ) and the 4th switch (M 1b ) can be connected to the other end of the transformer (102).

[0032] In this structure, the first inductor (L) at node (n2) k ) to the transformer (102) through the current (i) p ) can be transmitted to the secondary circuit (104) through the transformer (102).

[0033] From an overall perspective, the first switching unit (110) includes two bridge circuits and a first capacitor (C) between the bridge circuits. C 1) can be implemented.

[0034] The secondary circuit (104) is connected to a transformer (102), a second switching unit (112), and a second capacitor (C C 2) and a resonance unit (114).

[0035] The second switching unit (112) can be implemented as a full-bridge circuit, and the fifth switch (M) is connected in parallel to one end of the secondary side of the transformer (102), i.e., the node (n5). 3a ) and the 6th switch (M 4b ), the 7th switch (M) connected in parallel to the other end of the secondary side of the transformer (102), i.e., the node (n6) 4a ) and the 8th switch (M 3b ) may be included. Here, the fifth switch (M 3a ) / 6th switch (M 4b ) and the 7th switch (M 4a ) / 8th switch (M 3b ) is the second capacitor (C C 2) are connected in parallel with each other based on the second capacitor (C C 2) is the 5th switch (M 3a ) and the 7th switch (M 4a ) can be connected between them.

[0036] From an overall perspective, the second switching unit (112) includes two bridge circuits and a second capacitor (C) between the bridge circuits. C 2) can be implemented.

[0037] According to one embodiment, both switching units (110 and 112) have a full bridge circuit structure and may have a structure that is symmetrical with respect to the transformer (102). As a result, the primary circuit (100) and the secondary circuit (104) can realize bidirectional equal gain.

[0038] At this time, the 5th switch (M 3a ) / 8th switch (M 3b ) and the 6th switch (M 4b ) / 7th Switch (M 4a ) perform complementary switching operations. At this time, the fifth switch (M 3a ) and the 8th switch (M 3b ) acts as the main switch, and the 6th switch (M 4b) and the 7th switch (M 4a ) can operate as a clamp switch. This active clamp structure enables the discharge of the parasitic capacitor of the main switch, so that all switches can implement ZVS.

[0039] According to one embodiment, each switch (M 3a , M 3b , M 4a ,M 4b ) is a MOSFET and may include a body diode and parasitic capacitors. Consequently, the switch (M 3a , M 3b , M 4a ,M 4b ) may still flow through the internal diode even when it is turned off.

[0040] The resonant section (114) performs a resonant function and is connected to the node (n7) between the second switching section (112) and the battery, and the inductor (L) is connected between the node (n7) and one end of the battery. f ) and a capacitor (C) connected between the node (n7) and the other end of the battery f ) may be included. That is, based on the node (n7), the inductor (L f ) and capacitor (C f ) can be connected in parallel.

[0041] Of course, the structure of the resonance unit (114) is not limited to the structure of Fig. 1, and can be modified in various ways as long as it performs the resonance function.

[0042] In summary, the flyback converter of this embodiment is implemented with a primary circuit (100) and a secondary circuit (104) as full bridge circuits, and the full bridge circuits can be arranged symmetrically with respect to the transformer (102).

[0043]

[0044] The operation of a flyback converter having this structure will be described in detail with reference to the attached drawings.

[0045] FIG. 2 is a timing diagram illustrating the operation of a flyback converter according to an embodiment of the present invention, FIGS. 3 to 8 are drawings illustrating the operation process of a flyback converter according to an embodiment of the present invention, and FIG. 9 is a drawing illustrating a graph showing the operating efficiency of a flyback converter according to an embodiment of the present invention.

[0046] The flyback converter of the present invention operates in six modes and can be controlled by PWM.

[0047] In the first mode, the first switch (M) as shown in FIGS. 2 and 3 1a ) and the 4th switch (M 1b ) is turned on first, but the fifth switch (M 3a ) and the 8th switch (M 3b ) is completely off. Of course, the second switch (M 2b ), 3rd switch (M 2a ), 6th switch (M 4b ) and the 7th switch (M 4a ) is also off. Therefore, a predetermined current flows through the first switch (M 1a ), first inductor (L k ), the primary side and the second inductor (L) of the transformer (102) m ) and the 4th switch (M 1b ) flows through the first inductor (L k ) and a second inductor (L m ) energy is stored in.

[0048] Then, after a certain amount of time, the 6th switch (M 4b ) and the 7th switch (M 4a ) is also turned on. As a result, a predetermined current flows through the seventh switch (M 4a ), second capacitor (C C 2), capacitor (C f ) and the 6th switch (M 4b ) and can flow through the secondary side of the transformer (102).

[0049] In the second mode, the first switch (M) as shown in FIG. 2 and FIG. 4 1a ), 4th switch (M 1b ), 6th switch (M 4b ) and the 7th switch (M 4a ) is turned off. In this case, the first switch (M 1a ) / 4th switch (M 1b ) and the second switch (M 2b ) / 3rd switch (M 2a ) and a potential exchange occurs between the fifth switch (M 3a ) / 8th switch (M 3b ) and the 6th switch (M 4b ) / 7th Switch (M 4a ) can cause potential exchange between them.

[0050] In the third mode, the fifth switch (M) as shown in FIG. 2 and FIG. 5 3a ) and the 8th switch (M 3b ) is turned on, and after a predetermined period of time, the second switch (M 2b ) and the third switch (M 2a ) can be turned on.

[0051] 5th switch (M 3a ) and the 8th switch (M 3b ) is turned on, a predetermined current flows through the secondary side of the transformer (102), the fifth switch (M 3a ), capacitor (C f ) and the 8th switch (M 3b ) flows through the primary side of the transformer (102). At this time, a predetermined current flows through the second switch (M 2b ) body diode, first inductor (L k ), primary coil of transformer (102), third switch (M 2a ) body diode, first capacitor (C C 1) and can flow through the power.

[0052] Then, after a certain amount of time, the second switch (M 2b ) and the third switch (M 2a ) is turned on, the first capacitor (C C 1), 3rd switch (M 2a ), the primary side of the transformer (102), the first inductor (L k ), second switch (M 2b ) and flows through the power supply. At this time, the reverse current of the primary current of the transformer (102) flows through the second switch (M 2b ) and the third switch (M 2a ) becomes the same as the clamp current.

[0053] In the fourth mode, the fifth switch (M) is turned on as shown in FIG. 2 and FIG. 6. 3a ), 8th switch (M 3b ), second switch (M 2b ) and the third switch (M 2a ) is turned off. In this case, the first switch (M 1a ) and the 4th switch (M 1b ) and the second switch (M 2b ) and the third switch (M 2a ) potential exchange occurs between the secondary circuit (104). On the other hand, in the secondary circuit (104), the fifth switch (M 3a ) and the 8th switch (M 3b ) current flows in the source-drain direction through the body diode, and continues to conduct until the secondary current of the transformer (102) becomes 0.

[0054] In the fifth mode, the first switch (M) as shown in FIG. 2 and FIG. 7 1a ) / 4th switch (M 1b ) and the second switch (M 2b ) / 3rd switch (M 2a ) is completed, the second switch (M 2b ) and the third switch (M 2a ) is completely off and the first switch (M 1a) and the 4th switch (M 1b ) The primary current of the transformer (102) flows through the body diode, causing the primary current to increase.

[0055] In the 6th mode, the 5th switch (M) as shown in FIG. 2 and FIG. 8 3a ) and the 8th switch (M 3b ) when the current flowing through the body diode becomes 0, the fifth switch (M 3a ) and the 8th switch (M 3b ) begins to charge, and the 6th switch (M 4b ) and the 7th switch (M 4a ) parasitic capacitance begins to discharge.

[0056] It can be confirmed that the flyback converter operating as described above achieves a maximum efficiency of 97% in both forward and reverse directions, as shown in Fig. 9. That is, it can be confirmed that the flyback converter operates with high efficiency while reducing the voltage stress on the switch by using a full-bridge circuit structure.

[0057]

[0058] Meanwhile, the components of the aforementioned embodiments can be easily understood from a process perspective. That is, each component can be understood as a separate process. Furthermore, the processes of the aforementioned embodiments can be easily understood from the perspective of the device components.

[0059] In addition, the technical contents described above may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiments or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands, such as ROMs, RAMs, and flash memories. Examples of program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

[0060] The above-described embodiments of the present invention are disclosed for the purpose of illustration, and those skilled in the art with common knowledge of the present invention will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following patent claims.

Claims

1. Transformer; A primary circuit located on the primary side of the transformer and having a first switching section; and A secondary circuit located on the secondary side of the above transformer and having a second switching section, A flyback converter characterized in that the first switching unit and the second switching unit are each implemented as two bridge circuits and a capacitor between the bridge circuits.

2. A flyback converter according to claim 1, characterized in that the flyback converter is used in an onboard charger (OBC) and is a bidirectional DC / DC converter.

3. In the first paragraph, the first switching unit, A first switch and a second switch connected in series with each other to a first node connected to a power source; A third switch and a fourth switch connected in series to the first node; and Including a first capacitor connected between the first switch and the third switch, A flyback converter characterized in that the first switch and the second switch are connected in parallel with the third switch and the fourth switch based on the first node, the first switch and the fourth switch are main switches, the second switch and the third switch are clamp switches, and the first switch and the fourth switch and the second switch and the third switch operate complementarily.

4. In the third paragraph, the primary circuit, A first inductor connected to a second node between the first switch and the second switch and one end of the primary side of the transformer; and Further comprising a second inductor connected between a node between the first inductor and one end of the primary side of the transformer and the other end of the transformer, A flyback converter, characterized in that the other end of the second inductor is connected to a third node between the third switch and the fourth switch.

5. In the third paragraph, the second switching unit, A fifth switch and a sixth switch connected in parallel to one end of the secondary side of the above transformer; A seventh switch and an eighth switch connected in parallel to each other at the other end of the secondary side of the transformer; and Including a second capacitor connected between the fifth switch and the seventh switch, A flyback converter characterized in that the fifth switch and the seventh switch are connected in parallel with each other based on the second capacitor, the fifth switch and the eighth switch are main switches, the sixth switch and the seventh switch are clamp switches, and the fifth switch and the eighth switch and the sixth switch and the seventh switch operate complementarily.

6. In the fifth paragraph, after the first switch and the fourth switch are turned on in the first mode, the sixth switch and the seventh switch are turned on after a predetermined time has elapsed. A flyback switch, characterized in that the second switch, the third switch, the fifth switch and the eighth switch are in an off state.

7. In the 6th paragraph, a second mode is performed in which all switches are in an off state after the first mode, In the third mode performed after the second mode, the second switch and the third switch are turned on after a predetermined time after the fifth switch and the eighth switch are turned on. A flyback switch, characterized in that in the third mode, the first switch, the fourth switch, the sixth switch and the seventh switch are in an off state.

8. In the first paragraph, the secondary circuit, A flyback converter further comprising a resonant section connected between the second switching section and the battery.

9. A flyback converter according to claim 1, characterized in that the first switching unit and the second switching unit have a symmetrical circuit structure with respect to the transformer.

10. Transformer; A primary circuit located on the primary side of the transformer and having a first switching section; and A secondary circuit located on the secondary side of the above transformer and having a second switching section, The above first switching unit, A first switch and a second switch connected in series to the first node; and Including a third switch and a fourth switch connected in series to the first node, A flyback converter characterized in that the first switch and the second switch are connected in parallel with the third switch and the fourth switch based on the first node, the first switch and the fourth switch are main switches, and the second switch and the third switch are clamp switches.

11. A flyback converter according to claim 10, wherein the first switch and the fourth switch and the second switch and the third switch operate complementarily.

12. A flyback converter according to claim 10, characterized in that the first switching unit and the second switching unit have a symmetrical circuit structure with respect to the transformer.

13. Transformer; A primary circuit located on the primary side of the transformer and having a first switching section; and A secondary circuit located on the secondary side of the above transformer and having a second switching section, The above second switching unit, A fifth switch and a sixth switch connected in parallel to one end of the secondary side of the transformer; and Including a 7th switch and an 8th switch connected in parallel to each other at the other end of the secondary side of the above transformer, A flyback converter characterized in that the fifth switch and the eighth switch are main switches, and the sixth switch and the seventh switch are clamp switches.

14. A flyback converter according to claim 13, wherein the fifth switch and the eighth switch and the sixth switch and the seventh switch operate complementarily.

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