Bidirectional dc-dc power converter with lift and control method thereof

Abstract

A bidirectional DC-DC power converter capable of both step-up and step-down conversion and a control method thereof. The converter comprises a bidirectional DC-DC resonant converter and a control unit. The control unit generates a plurality of control signals for controlling the resonant converter, such that the resonant converter can operate in a plurality of different conversion modes according to the control signals to achieve bidirectional step-up and step-down conversion between the two sides of the resonant converter. In particular, when the resonant converter converts the input voltage received by a second full-bridge chopper circuit to the output of a first full-bridge chopper circuit via an LLC resonant circuit while the control frequency of the second full-bridge chopper circuit is lower than the resonant frequency on the input side, the control of the first full-bridge chopper circuit is increased when the LLC resonant circuit reaches resonance, so that the output side can output a higher output voltage.

Description

Technical Field

[0001] This invention relates to a DC-DC resonant converter, and more particularly to a bidirectional DC-DC power conversion device with step-up / step-down capability and its control method. Background Technology

[0002] Existing DC-DC LLC power conversion circuits typically include a first full-bridge chopper circuit connected across a first side, a second full-bridge chopper circuit connected across a second side, and an LLC resonant circuit coupled between the first and second full-bridge chopper circuits. The first full-bridge chopper circuit typically consists of four power-type switching components, the second full-bridge chopper circuit typically consists of four power-type switching components, and the LLC resonant circuit consists of a resonant capacitor, a resonant inductor, and a transformer.

[0003] However, under existing control methods, while the first and second full-bridge chopper circuits can achieve boost or buck power conversion from the first side to the second side, they can only achieve buck conversion from the second side to the first side. Therefore, how to control this LLC power conversion circuit to achieve bidirectional boost / buck power conversion between the first and second sides has become one of the issues that the relevant technical field seeks to solve. Summary of the Invention

[0004] One object of the present invention is to provide a bidirectional DC-DC resonant converter that overcomes at least one drawback of the prior art.

[0005] The present invention provides a bidirectional DC-DC power conversion device, comprising a bidirectional DC-DC resonant converter and a control unit.

[0006] The bidirectional DC-DC resonant converter has a first side and a second side that can be used as the input side and output side or the output side and input side, respectively, and includes a first full-bridge chopper circuit, a second full-bridge chopper circuit, and an LLC resonant circuit. The first full-bridge chopper circuit includes first and second switching components and third and fourth switching components connected in series across the first side, wherein the first and third switching components and the second and fourth switching components are electrically connected to the positive and negative terminals of the first side, respectively, and the first to fourth switching components are turned on or off in response to first to fourth control signals, respectively. The second full-bridge chopper circuit includes fifth and sixth switching components and seventh and eighth switching components connected in series across the second side, wherein the fifth and seventh switching components and the sixth and eighth switching components are electrically connected to the positive and negative terminals of the second side, respectively, and the fifth to eighth switching components are turned on or off in response to fifth to eighth control signals, respectively. The LLC resonant circuit is coupled between the first full-bridge chopper circuit and the second full-bridge chopper circuit, and includes a resonant capacitor, a resonant inductor, and a transformer. The primary windings of the resonant capacitor, the resonant inductor, and the transformer, which are connected in series, are coupled between a first common node between the first and second switching assemblies and a second common node between the third and fourth switching assemblies. The secondary winding of the transformer is coupled between a third common node between the fifth and sixth switching assemblies and a fourth common node between the seventh and eighth switching assemblies.

[0007] The control unit is electrically connected to the first and second full-bridge chopper circuits and is configured to generate and provide the first to eighth control signals for controlling the first to eighth switching components, so that the bidirectional DC-DC resonant converter can operate in one of the first to third conversion modes.

[0008] When the first side is used as the input side for receiving the input voltage and the second side is used as the output side for outputting the output voltage, the bidirectional DC-DC resonant converter operates in the first conversion mode, wherein the control unit, in each control cycle of the first full-bridge chopper circuit: makes the first and fourth control signals identical to each other, so that the first and fourth switching components operate synchronously; makes the second and third control signals identical to each other and complementary to the first and fourth control signals, so that the second and third switching components operate synchronously; makes a first dead time, related to the switching speed of the first to fourth switching components, exist between the rising edge of one of the first / fourth control signals and the falling edge of the other, so that during the first dead time, both the first and second switching components are turned off to avoid shoot-through of the first and second switching components or both the third and fourth switching components are turned off to avoid shoot-through of the third and fourth switching components; and makes the fifth to eighth switching components all turned off, so that the second full-bridge chopper circuit functions as a full-wave rectifier circuit.

[0009] When the second side serves as the input side for receiving the input voltage and the first side serves as the output side for outputting the output voltage, and the control frequency of the fifth to eighth switching components is higher than the resonant frequency relative to the second side and related to the resonant capacitor and the resonant inductor, the bidirectional DC-DC resonant converter operates in the second conversion mode, wherein the control unit, in each control cycle of the second full-bridge chopper circuit: makes the fifth and eighth control signals identical to each other, so that the fifth and eighth switching components operate synchronously; makes the sixth and seventh control signals identical to each other and complementary to the fifth and eighth control signals, so that the sixth and seventh switching components operate synchronously; there is a second dead time between the rising edge of one of the fifth / eighth control signals and the falling edge of the other, which is related to the switching speed of the fifth to eighth switching components, so that during the second dead time, both the fifth and sixth switching components are turned off to avoid the fifth and sixth switching components shoot-through or both the seventh and eighth switching components are turned off to avoid the seventh and eighth switching components shoot-through; and turns off the first to fourth switching components, so that the first full-bridge chopper circuit is used as a full-wave rectifier circuit.

[0010] When the second side is used as the input side for receiving the input voltage and the first side is used as the output side for outputting the output voltage, and the control frequency of the fifth to eighth switching components is lower than the resonant frequency, the bidirectional DC-DC resonant converter operates in the third conversion mode, wherein the control unit, in each control cycle of the second full-bridge chopper circuit: makes the fifth and eighth control signals identical to each other, so that the fifth and eighth switching components operate synchronously; makes the sixth and seventh control signals identical to each other and complementary to the fifth and eighth control signals, so that the sixth and seventh switching components operate synchronously; and makes a second dead time exist between the rising edge of one of the fifth / eighth control signals and the falling edge of the other of the sixth / seventh control signal, so that the fifth and sixth switching components are both turned off during the second dead time to avoid the fifth and sixth switching components... The following actions are taken: 1. The first and third switching components are turned off; 2. The second switching component is turned on in response to the second control signal during the conduction period of the fifth and eighth switching components and when the resonant capacitor and the resonant inductor reach resonance, and is simultaneously turned off with the fifth and eighth switching components, so that the resonant capacitor is charged by the induced current of the primary winding during the conduction period of the second switching component; 3. The fourth switching component is turned on in response to the fourth control signal during the conduction period of the sixth and seventh switching components and when the resonant capacitor and the resonant inductor reach resonance, and is simultaneously turned off with the sixth and seventh switching components, so that the resonant capacitor is charged by the induced current of the primary winding during the conduction period of the fourth switching component.

[0011] In one embodiment of the present invention, the first to fourth switching components are identical to each other, and each of them comprises a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

[0012] In one embodiment of the present invention, the fifth to eighth switching components are identical to each other, and each of them comprises a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

[0013] In one embodiment of the present invention, the bidirectional DC-DC resonant converter further includes a first filter capacitor and a second filter capacitor respectively connected across the first side and the second side.

[0014] Another object of the present invention is to provide a bidirectional DC-DC resonant converter as described above, which overcomes at least one disadvantage of the prior art.

[0015] The control method of the bidirectional DC-DC power conversion device provided by the present invention includes the following steps: When the input power is converted from the first side to the output voltage output from the second side, in each control cycle of the first full-bridge chopper circuit: the first and fourth control signals are made the same; the second and third control signals are made the same and complementary to the first and fourth control signals; and a first dead time related to the switching speed of the first to fourth switching components is inserted between the rising edge of one of the first / fourth control signals and the falling edge of the second / third control signal and the other; when the input voltage is converted from the second side to the output voltage output from the first side and the control frequency of the fifth to eighth switching components is higher than the resonant frequency relative to the second side and related to the resonant capacitor and the resonant inductor, in each control cycle of the second full-bridge chopper circuit: the fifth and eighth control signals are made the same; the sixth and seventh control signals are made the same and complementary to the fifth and eighth control signals; and a cutting time related to the switching speed of the fifth to eighth switching components is inserted between the rising edge of one of the fifth / eighth control signals and the falling edge of the sixth / seventh control signal and the other. A second dead time related to the switching speed; and when the input voltage is switched from the second side to the output voltage of the first side and the control frequency of the fifth to eighth switching components is lower than the resonant frequency, in each control cycle of the second full-bridge chopper circuit: the fifth and eighth control signals are made the same as each other; the sixth and seventh control signals are made the same as each other and complementary to the fifth and eighth control signals; a second dead time related to the switching speed of the fifth to eighth switching components is inserted between the rising edge of one of the fifth / eighth control signals and the falling edge of the other of the sixth / seventh control signals; the second switching component is turned on during the conduction period of the fifth and eighth switching components and when the resonant capacitor and the resonant inductor reach resonance, and is turned off synchronously with the fifth and eighth switching components, so that the resonant capacitor is charged by the induced current of the primary winding during the conduction period of the second switching component; and the fourth switching component is turned on during the conduction period of the sixth and seventh switching components and when the resonant capacitor and the resonant inductor reach resonance, and is turned off synchronously with the sixth and seventh switching components.

[0016] The beneficial effect of the present invention is that, in the third conversion mode, the control unit can use additional control over the second and fourth switching components to enable the resonant capacitor in the resonant circuit to be additionally charged, thereby realizing the boost voltage of the bidirectional DC-DC resonant circuit from the second side to the first side. Attached Figure Description

[0017] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, wherein:

[0018] Figure 1 This is a circuit block diagram illustrating an embodiment of the present invention: a bidirectional DC-DC power conversion device.

[0019] Figure 2 This is a circuit diagram illustrating, by way of example, the bidirectional DC-DC resonant converter of the described embodiment;

[0020] Figure 3 This is a timing diagram, exemplarily illustrating the operation of the embodiment during the first switching mode, generating the first to fourth control signals of the control unit;

[0021] Figure 4 This is a timing diagram illustrating, exemplarily, the fifth to eighth control signals generated by the control unit during the operation of the embodiment in the second switching mode; and

[0022] Figure 5 This is a timing diagram illustrating, exemplarily, the second, fourth, fifth to eighth control signals generated by the control unit when the embodiment is operating in the third switching mode. Detailed Implementation

[0023] Before describing the invention in more detail, it should be noted that, where deemed appropriate, reference numerals are repeatedly used in the drawings to indicate corresponding or similar components, which may have similar characteristics.

[0024] See Figure 1 The illustration exemplarily depicts a bidirectional DC-DC power conversion device according to an embodiment of the present invention. The bidirectional DC-DC power conversion device includes, for example, a bidirectional DC-DC resonant converter 10 and a control unit 20 for controlling the bidirectional DC-DC resonant converter 10.

[0025] In this embodiment, the bidirectional DC-DC resonant converter 10 has a first side DC1 and a second side DC2, which can be used as the input side and output side or the output side and input side, respectively. The first side DC1 has a positive terminal DC1+ and a negative terminal DC1-, and the second side DC2 has a positive terminal DC2+ and a negative terminal DC2-. More specifically, when the first side DC1 is used as an input side, the first side DC1 is adapted to apply a DC input voltage; and when the second side DC2 is used as an input side, the second side DC2 is adapted to apply a DC input voltage. The bidirectional DC-DC resonant converter 10 includes, for example, a first filter capacitor C1, a second filter capacitor C2, a first full-bridge chopper circuit 1, a second full-bridge chopper circuit 2, and an LLC resonant circuit 3.

[0026] The following will be referred to Figure 2 The circuit structure of the bidirectional DC-DC resonant converter 10 is described in further detail.

[0027] The first filter capacitor C1 is connected across the first side DC1, and the second filter capacitor C2 is connected across the second side DC2.

[0028] The first full-bridge chopper circuit 1 includes first to fourth switching components K1 to K4. The first and second switching components K1 and K2 are connected in series and across the first-side DC1, and are electrically connected to the positive terminal DC1+ and the negative terminal DC1- of the first-side DC1, respectively. The third and fourth switching components K3 and K4 are connected in series and across the first-side DC1, and are electrically connected to the positive terminal DC1+ and the negative terminal DC1- of the first-side DC1, respectively. The first to fourth switching components K1 to K4 are turned on or off in response to first to fourth control signals S1 to S4. In this embodiment, each of the first to fourth switching components includes, for example, a metal-oxide-semiconductor field-effect transistor (hereinafter referred to as a MOSFET), such as an n-channel MOSFET, and a body diode connected in anti-parallel to the MOSFET, and the gate of the MOSFET is used to receive the corresponding control signals S1 / S2 / S3 / S4. However, in other embodiments, each of the first to fourth switching components K1 to K4 may also include an insulated gate bipolar transistor (hereinafter referred to as IGBT). It is worth noting that when the MOSFETs of the first to fourth switching components K1 to K4 are all turned off in response to the first to fourth control signals S1 to S4, the first full-bridge chopper circuit 1 can be used as a full-wave rectifier circuit.

[0029] The second full-bridge chopper circuit 2 includes fifth to eighth switching components K5 to K8. The fifth and sixth switching components K5 and K6 are connected in series and bridging the second-side DC2, and are electrically connected to the positive terminal DC2+ and the negative terminal DC2- of the second-side DC2, respectively. The seventh and eighth switching components K7 and K8 are connected in series and bridging the second-side DC2, and are electrically connected to the positive terminal DC2+ and the negative terminal DC2- of the second-side DC2, respectively. The fifth to eighth switching components K5 to K8 are turned on or off in response to fifth to eighth control signals S5 to S8, respectively. In this embodiment, each of the fifth to eighth switching components includes, for example, a MOSFET (such as an n-channel MOSFET) and a body diode connected in anti-parallel to the MOSFET, wherein the gate of the MOSFET is used to receive the corresponding control signals S5 / S6 / S7 / S8. However, in other embodiments, each of the fifth to eighth switching components K5 to K8 may also include an IGBT. Similar to the first full-bridge chopper circuit 1, when the MOSFETs of the fifth to eighth switching components K5 to K8 are all turned off in response to the fifth to eighth control signals S5 to S8, the second full-bridge chopper circuit 2 can be used as a full-wave rectifier circuit.

[0030] The LLC resonant circuit 3 is coupled between the first full-bridge chopper circuit 1 and the second full-bridge chopper circuit 2, and includes, for example, a resonant capacitor Cr, a resonant inductor Lr, and a transformer T. The transformer T includes a primary winding L1 and a secondary winding L2. The resonant capacitor Cr, the resonant inductor Lr, and the primary winding L1 are connected in series and coupled between a first common node n1 and a second common node n2 (one end of the resonant capacitor Cr is coupled to the first common node n1, and the dotted and non-dotted ends of the primary winding are respectively coupled to one end of the resonant inductor Lr and the second common node n2). The dotted and non-dotted ends of the secondary winding L2 are respectively coupled to a third common node n3 and a fourth common node n4.

[0031] The control unit 20 is electrically connected to the first and second full-bridge chopper circuits (see...). Figure 1 The first to eighth control signals S1 to S8 are configured to generate and provide control signals S1 to S8 for controlling the MOSFETs of the first to eighth switching components K1 to K8, so that the bidirectional DC-DC resonant converter 10 can operate in one of the first to third conversion modes.

[0032] When the first side DC1 and the second side DC2 serve as the input side for receiving an input voltage and the output side for outputting an output voltage, respectively, the bidirectional DC-DC resonant converter 10 operates in the first conversion mode according to the first to fourth control signals S1 to S4 (or the first to eighth control signals S1 to S8) from the control unit 20. (See also...) Figure 3 In the first switching mode, within each control cycle T of the first full-bridge chopper circuit 1, the control unit 20: makes the first and fourth control signals S1 and S4 identical to each other so that the first and fourth switching components K1 and K4 operate synchronously; makes the second and third control signals S2 and S3 identical to each other and complementary to the first and fourth control signals S1 and S4 so that the second and third switching components K2 and K3 operate synchronously; and makes a first dead time, related to the switching speed of the first to fourth switching components K1 to K4, exist between the rising edge of one of the first / fourth control signals S1 / S4 and the falling edge of the second / third control signal S2 / S3. (e.g., t0~t1 and t2~t3) such that during the first dead time, the first and second switching components K1, K2 are both turned off to avoid the first and second switching components K1, K2 being directly connected during the switching process, or the third and fourth switching components K3, K4 are both turned off to avoid the third and fourth switching components K3, K4 being directly connected during the switching process; and the fifth to eighth switching components K5~K8 are all turned off (for example, the control unit 20 stops outputting the fifth to eighth control signals S5~S8, or outputs a signal (not shown) held at the logic -0 level as the fifth to eighth control signals S5~S8) such that the second full-bridge chopper circuit 2 can be used as a full-wave rectifier circuit. Please note that since the first dead time is related to the switching speed of the first to fourth switching components K1 to K4, in this embodiment, the MOSFETs contained in the first to fourth switching components K1 to K4 have a relatively fast switching speed, so the first dead time can be, but is not limited to, a time in the range of 0.3μs to 0.5μs. In other embodiments, if the first to fourth switching components K1 to K4 contain IGBTs with a relatively slow switching speed, the first dead time can be, for example, a time in the range of 0.5μs to 1μs.

[0033] The following will be coordinated Figure 2 and Figure 3 The bidirectional DC-DC resonant converter 10 operates in four working states in each control cycle T under the first conversion mode.

[0034] After the previous control cycle T ends, firstly, in the first operating state corresponding to the first dead time t0~t1, the first to eighth switching components K1~K8 are all turned off to prevent the first and second switching components K1, K2 or the third and fourth switching components K3, K4 from being turned on during the switching process; then, in the second operating state corresponding to time t1~t2, the second and third switching components K2, K3 are turned on in response to the second and third control signals S2, S3, and the other switching components K1, K2, K5~K8 are all turned off, so the input current flow corresponding to the input voltage received by the first side DC1 (input side) is... The input voltage flows through the non-spotted end of the primary winding L1 via the activated third switching assembly K3, then through the resonant inductor Lr and the resonant capacitor Cr (for (reverse) resonant charging), and finally through the activated second switching assembly K2. Simultaneously, the induced current generated in the secondary winding L2 flows out from the non-spotted end of the secondary winding L2, through the body diodes of the seventh and sixth switching assemblies K7 and K6, and finally flows back into the secondary winding L2 via the spotted end, charging the second-side DC2 (output side), thereby converting the input voltage into a voltage that is applied to the second-side DC2. 2. Output voltage; then, in the third operating state corresponding to the first dead time t2~t3, similar to the first operating state described above, the first to eighth switching components K1~K8 are all turned off to prevent the first and second switching components K1, K2 from being turned on or the third and fourth switching components K3, K4 from being turned on during the switching process; finally, in the fourth operating state corresponding to time t3~t4, the first and fourth switching components K1, K4 are turned on in response to the first and fourth control signals S1, S4, and the other switching components K2, K3, K5~K8 are all turned off, thus the input voltage corresponding to the input voltage received by the first side DC1 is... Current flows through the first conducting switch assembly K1, the resonant capacitor Cr, and the resonant inductor Lr, then flows into the primary winding L1 from the dotted end (for resonant charging), and finally flows through the fourth conducting switch assembly K4. Simultaneously, the induced current generated in the secondary winding L2 flows out from the dotted end of the secondary winding L2 and through the body diodes of the fifth and eighth switch assemblies K5 and K8, finally flowing into the secondary winding L2 through the non-dotted end to charge the second-side DC2, thereby converting the input voltage into an output voltage output on the second-side DC2. After this control cycle T ends, the system enters the first operating state of the next control cycle T, which corresponds to the dead time t4 to t5.

[0035] When the second side DC2 serves as the input side for receiving an input voltage and the first side DC1 serves as the output side for outputting an output voltage, and the control frequency of the fifth to eighth switching components K5 to K8 is higher than a resonant frequency relative to the second side DC2 and related to the resonant capacitor Cr and the resonant inductor Lr, the bidirectional DC-DC resonant converter 10 operates in the second conversion mode according to the fifth to eighth control signals S5 to S8 (or the first to eighth control signals S1 to S8) from the control unit 20. It is worth noting that the resonant frequency can be represented as follows: Where L r1 The equivalent inductance value (which can be obtained by actual measurement) represents the combined effect of the stray inductance parasitic on the second full-bridge chopper circuit 2 and the inductance of the resonant inductor Lr, and C r1 The representative value is the equivalent capacitance of the parasitic stray capacitance in the second full-bridge chopper circuit 2 combined with the resonant capacitor Cr (which can be obtained through actual measurement). See also Figure 4 In the second switching mode, within each control cycle T' of the second full-bridge chopper circuit 2, the control unit 20: makes the fifth and eighth control signals S5 and S8 identical to each other, so that the fifth and eighth switching components K5 and K8 operate synchronously; makes the sixth and seventh control signals S6 and S7 identical to each other and complementary to the fifth and eighth control signals S5 and S8, so that the sixth and seventh switching components K6 and K7 operate synchronously; and makes a second dead time, related to the switching speed of the fifth to eighth switching components K5 to K8, exist between the rising edge of one of the fifth / eighth control signals S5 / S8 and the falling edge of the sixth / seventh control signal S6 / S7. For example, t'0~t'1 and t'2~t'3) so that during the second dead time, the fifth and sixth switching components K5 and K6 are both turned off to avoid the fifth and sixth switching components K5 and K6 being shot-through during the switching process, or the seventh and eighth switching components K7 and K8 are both turned off to avoid the seventh and eighth switching components K7 and K8 being shot-through during the switching process; and the first to fourth switching components K1~K4 are all turned off (for example, the control unit 20 stops outputting the first to fourth control signals S1~S4, or outputs signals held at logic -0 level (not shown) as the first to fourth control signals S1~S4), so that the first full-bridge chopper circuit 1 is used as a full-wave rectifier circuit. In this embodiment, since the fifth to eighth switching components K5~K8 are similar to the first to fourth switching components K1~K4 (i.e., containing n-channel MOSFETs), the control period T' can be similar to the control period T in the first switching mode, and the second dead time can be similar to the first dead time in the first switching mode.

[0036] For example, the control period of the second full-bridge chopper circuit 2 is, for example, 6μs (e.g., Figure 4 As shown), the resonant frequency is, for example, approximately 142 kHz (i.e., the resonant period is approximately 7 μs). In this case, since the control frequency of the fifth to eighth switching components K5 to K8 is higher than the resonant frequency, the bidirectional DC-DC resonant converter 10 will operate in the second conversion mode. The following will be discussed in conjunction with... Figure 2 and Figure 4 The bidirectional DC-DC resonant converter 10 operates in the second conversion mode in four operating states during each control cycle T'.

[0037] After the previous control cycle T' ends, firstly, in the first operating state corresponding to the second dead time t'0~t'1, the first to eighth switch components K1~K8 are all turned off to prevent the fifth and sixth switch components K5, K6 or the seventh and eighth switch components K7, K8 from being turned on during the switching process; then, in the second operating state corresponding to time t'1~t'2, the fifth and eighth switch components K5, K8 are turned on in response to the fifth and eighth control signals S5, S8, and the other switch components K1~K4, K6, K7 are all turned off, thus corresponding to the second side DC2 (input side) connected to The input current of the received input voltage flows through the conducting fifth switching component K5, then flows into the secondary winding L2 from the dotted end, and finally flows through the conducting eighth switching component K8. Simultaneously, the induced current generated in the primary winding L1 flows out from the dotted end of the primary winding L1 and passes through the resonant inductor Lr and the resonant capacitor Cr (for resonant charging), finally flowing through the body diodes of the first and fourth switching components K1 and K4 to charge the first-side DC1 (output side), thereby converting the input voltage into an output voltage output on the first-side DC1. Then, in the... In the third operating state corresponding to the second dead time t'2 to t'3, similar to the first operating state described above, the first to eighth switching components K1 to K8 are all turned off to prevent the fifth and sixth switching components K5 and K6 or the seventh and eighth switching components K7 and K8 from being turned on during the switching process. Finally, in the fourth operating state corresponding to time t'3 to t'4, the sixth and seventh switching components K6 and K7 are turned on in response to the sixth and seventh control signals S6 and S7, and the other switching components K1 to K4, K5, and K8 are all turned off. Thus, the input current corresponding to the input voltage received by the second side DC2 is... The current flows through the conducting seventh switching component K7, then flows into the secondary winding L2 from the non-pointed end, and finally flows through the conducting sixth switching component K6. Simultaneously, the induced current generated in the primary winding L1 flows out from the non-pointed end of the primary winding L1 and passes through the body diodes of the third and second switching components K3 and K2, the resonant capacitor Cr, and the resonant inductor Lr. Finally, it returns to the primary winding L1 via the pointed end to charge the first-side DC1, thereby converting the input voltage into an output voltage at the first-side DC1. After this control cycle T' ends, the system enters the first operating state of the next control cycle T', which corresponds to the dead time t'4~t'5.

[0038] When the second side DC2 serves as the input side for receiving an input voltage and the first side DC1 serves as the output side for outputting an output voltage, and the control frequency of the fifth to eighth switching components is lower than the resonant frequency, the bidirectional DC-DC resonant converter 10 operates in the third conversion mode according to the second and fourth control signals and the fifth to eighth control signals S5 to S8 (or the first to eighth control signals S1 to S8) from the control unit 20. See also Figure 5 In the third conversion mode, within each control cycle T” of the second full-bridge chopper circuit 2, the control unit 20: makes the fifth and eighth control signals S5 and S8 identical to each other, so that the fifth and eighth switching components K5 and K8 operate synchronously; the sixth and seventh control signals S6 and S7 are identical to each other and complementary to the fifth and eighth control signals S5 and S8, so that the sixth and seventh switching components K6 and K7 operate synchronously; a second dead time exists between the rising edge of one of the fifth / eighth control signals S5 / S8 and the falling edge of the sixth / seventh control signals S6 / S7, so that during the second dead time, both the fifth and sixth switching components are turned off to avoid the fifth and sixth switching components from being shot-through during the switching process, or both the seventh and eighth switching components are turned off to avoid the seventh and eighth switching components from being shot-through during the switching process; and the first and third switching components are turned off (for example, the control unit 20 stops outputting the first and third control signals S1). S3, or output a signal held at logic -0 level (not shown) as the first and third control signals S1, S3); cause the second switching component K2 to respond to the second control signal S2 and begin to conduct during the conduction period of the fifth and eighth switching components K5, K8 and when the resonant capacitor Cr and the resonant inductor Lr reach resonance, and to turn off synchronously with the fifth and eighth switching components K5, K8, so that the resonant capacitor Cr is charged by the induced current of the primary winding L1 during the conduction period of the second switching component K2; and cause the fourth switching component K4 to respond to the fourth control signal S4 and begin to conduct during the conduction period of the sixth and seventh switching components K6, K7 and when the resonant capacitor Cr and the resonant inductor Lr reach resonance, and to turn off synchronously with the sixth and seventh switching components K6, K7, so that the resonant capacitor Cr is charged by the induced current of the primary winding L1 during the conduction period of the fourth switching component K4.

[0039] For example, the control period of the second full-bridge chopper circuit 2 is, for example, 10 μs (e.g., Figure 5As shown), the resonant frequency is, for example, approximately 142 kHz (i.e., the resonant period is approximately 7 μs). In this case, since the control frequency of the fifth to eighth switching components K5 to K8 is lower than the resonant frequency, the bidirectional DC-DC resonant converter 10 will operate in the third conversion mode. The following will be discussed in conjunction with... Figure 2 and Figure 5 The bidirectional DC-DC resonant converter 10 operates in the third conversion mode in six working states during each control cycle T”.

[0040] After the previous control cycle T” ends, firstly, in the first operating state corresponding to the second dead time t”0~t”1, the first to eighth switch components K1~K8 are all turned off to prevent the fifth and sixth switch components K5, K6 or the seventh and eighth switch components K7, K8 from being turned on during the switching process; then, in the second operating state corresponding to time t”1~t”2, the fifth and eighth switch components K5, K8 are turned on in response to the fifth and eighth control signals S5, S8, and the other switch groups When components K1-K4, K6, and K7 are all turned off, the input current corresponding to the input voltage received by the second side DC2 (input side) flows through the conducting fifth switch component K5, then flows into the secondary winding L2 from the dotted end, and finally flows through the conducting eighth switch component K8. Simultaneously, the induced current generated in the primary winding L1 flows out from the dotted end of the primary winding L1 and passes through the resonant inductor Lr and the resonant capacitor Cr (for resonant charging), finally flowing through... The body diodes of the first and fourth switching components K1 and K4 charge the first-side DC1 (output side), especially at time point t”2, when the LLC resonant circuit 3 completes resonance; then, in order to achieve voltage boost, in the third operating state corresponding to time t”2 to t”3, the fifth and eighth switching components K5 and K8 are continuously turned on in response to the fifth and eighth control signals S5 and S8, and the second switching component K2 is turned on in response to the second control signal S2. Thus, the electrical energy corresponding to the input voltage continues to be transferred to the first-side DC1. Since the second switching component K2 is turned on, the induced current generated by the primary winding L1 continues to flow through the resonant inductor Lr, the resonant capacitor Cr, the body diodes of the second switching component K2 and the fourth switching component K4, and finally returns to the primary winding L1. In this way, the resonant capacitor Cr can continue to be resonantly charged (until the charging ends at time point t”3) so that the resonant capacitor Cr is coupled to one end of the resonant inductor Lr (i.e., at time point t”3). Figure 2The potential of the right end of the circuit is charged high to prepare for the commutation charging in the subsequent second half of the control cycle; then, in the fourth operating state corresponding to the second dead time t”3~t”4, similar to the first operating state described above, the first to eighth switch components K1~K8 are all turned off to prevent the fifth and sixth switch components K5, K6 or the seventh and eighth switch components K7, K8 from being turned on during the switching process; then, in the fifth operating state corresponding to time t”4~t”5, the sixth and seventh switch components K6, K7 respond to the With the sixth and seventh control signals S6 and S7 turned on, and all other switching components K1-K4, K5, and K8 turned off, the input current corresponding to the input voltage received by the second-side DC2 flows through the turned-on seventh switching component K7, then flows into the secondary winding L2 from the non-pointed end, and finally flows through the turned-on sixth switching component K6. Simultaneously, the induced current generated in the primary winding L1 flows out from the non-pointed end of the primary winding L1 and passes through the body diodes of the second and third switching components K2 and K3. The resonant capacitor Cr and the resonant inductor Lr eventually return to the primary winding L1 via the dotted terminal to charge the first-side DC1, specifically at time t”5 when the resonant circuit 3 completes resonance. Then, to achieve a voltage boost, in the sixth operating state corresponding to times t”5 to t”6, the sixth and seventh switching components K6 and K7 remain on in response to the sixth and seventh control signals S6 and S7, and the fourth switching component K4 is on in response to the fourth control signal S4. Thus, the electrical energy corresponding to the input voltage continues to be transferred to the first-side DC1. Since the fourth switching component K4 is on, the induced current generated by the primary winding L1 continues to flow through the fourth switching component K4, the body diode of the second switching component K2, the resonant capacitor Cr, and the resonant inductor Lr, finally returning to the primary winding L1. This allows the resonant capacitor Cr to continue resonant charging (until charging ends at time t”6) so that the resonant capacitor Cr is coupled to one end of the first common node n1 (i.e., at…). Figure 2 The potential at the left end of the circuit is charged high to prepare for the commutation charging in the first half of the next control cycle T”. After the end of this control cycle T”, the first working state of the next control cycle T” will be entered, which corresponds to the working state of the dead time t”6 to t”7.

[0041] In summary, because the control unit 20, in the third conversion mode, utilizes additional control over the second and fourth switch components K2 and K4, it can additionally charge the resonant capacitor Cr of the LLC resonant circuit 3, thereby enabling the bidirectional DC-DC resonant converter 10 to boost the voltage from the second side DC2 to the first side DC1. Therefore, the objective of the present invention is indeed achieved.

[0042] The above description is merely an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A bidirectional DC-DC power conversion apparatus comprising a bidirectional DC-DC resonant converter and a control unit, characterized in that: the bidirectional DC-DC resonant converter has a first side and a second side which can be used as an input side and an output side or an output side and an input side respectively, and comprises: a first full-bridge chopper circuit comprising first and second switching components and third and fourth switching components connected in series to each other and across the first side, wherein the first and third switching components and the second and fourth switching components are electrically connected to a positive terminal and a negative terminal of the first side respectively, and the first to fourth switching components are turned on or turned off in response to first to fourth control signals respectively; a second full-bridge chopper circuit comprising fifth and sixth switching components and seventh and eighth switching components connected in series to each other and across the second side, wherein the fifth and seventh switching components and the sixth and eighth switching components are electrically connected to a positive terminal and a negative terminal of the second side respectively, and the fifth to eighth switching components are turned on or turned off in response to fifth to eighth control signals respectively; and an LLC resonant circuit coupled between the first and second full-bridge chopper circuits and comprising a resonant capacitor, a resonant inductor and a transformer, a primary side winding of the resonant capacitor, the resonant inductor and the transformer connected in series to each other is coupled between a first common node between the first and second switching components and a second common node between the third and fourth switching components, and a secondary side winding of the transformer is coupled between a third common node between the fifth and sixth switching components and a fourth common node between the seventh and eighth switching components; the control unit is electrically connected to the first and second full-bridge chopper circuits and configured to generate and provide the first to eighth control signals for controlling the first to eighth switching components, so that the bidirectional DC-DC resonant converter is operable in one of first to third conversion modes; when the first side is used as the input side for receiving an input voltage and the second side is used as the output side for outputting an output voltage, the bidirectional DC-DC resonant converter operates in the first conversion mode, wherein in each control period of the first full-bridge chopper circuit, the control unit: makes the first and fourth control signals identical to each other, so that the first and fourth switching components are synchronously operated; makes the second and third control signals identical to each other and complementary to the first and fourth control signals, so that the second and third switching components are synchronously operated; makes a first dead time related to switching speed of the first to fourth switching components exist between a rising edge of one of the first / fourth control signals and a falling edge of the other of the second / third control signals, so that during the first dead time, the first and second switching components are both turned off to avoid shoot-through of the first and second switching components or the third and fourth switching components are both turned off to avoid shoot-through of the third and fourth switching components; and turns off the fifth to eighth switching components, so that the second full-bridge chopper circuit is used as a full-wave rectifier circuit. When the second side is as an input side for receiving an input voltage, the first side is as an output side for outputting an output voltage, and the control frequency of the fifth to eighth switching assemblies is higher than a resonance frequency relative to the second side and related to the resonance capacitor and the resonance inductor, the bidirectional DC-DC resonant converter operates in the second conversion mode, wherein the control unit, in each control period of the second full-bridge chopper circuit, makes the fifth and eighth control signals identical to each other so that the fifth and eighth switching assemblies operate synchronously; makes the sixth and seventh control signals identical to each other and complementary to the fifth and eighth control signals so that the sixth and seventh switching assemblies operate synchronously; there is a second dead time related to the switching speed of the fifth to eighth switching assemblies between the rising edge of one of the fifth / eighth control signals and the falling edge of the other one so that the fifth and sixth switching assemblies are both turned off in the second dead time to avoid the fifth and sixth switching assemblies shoot-through or the seventh and eighth switching assemblies are both turned off in the second dead time to avoid the seventh and eighth switching assemblies shoot-through; and makes the first to fourth switching assemblies all turned off so that the first full-bridge chopper circuit functions as a full-wave rectifier circuit; and When the second side is as an input side for receiving an input voltage, the first side is as an output side for outputting an output voltage, and the control frequency of the fifth to eighth switching assemblies is lower than the resonance frequency, the bidirectional DC-DC resonant converter operates in the third conversion mode, wherein the control unit, in each control period of the second full-bridge chopper circuit, makes the fifth and eighth control signals identical to each other so that the fifth and eighth switching assemblies operate synchronously; makes the sixth and seventh control signals identical to each other and complementary to the fifth and eighth control signals so that the sixth and seventh switching assemblies operate synchronously; makes there be the second dead time between the rising edge of one of the fifth / eighth control signals and the falling edge of the other one so that the fifth and sixth switching assemblies are both turned off in the second dead time to avoid the fifth and sixth switching assemblies shoot-through or the seventh and eighth switching assemblies are both turned off in the second dead time to avoid the seventh and eighth switching assemblies shoot-through; makes the first and third switching assemblies turned off; makes the second switching assembly turned on during the turn-on period of the fifth and eighth switching assemblies and starts to be turned on when the resonance capacitor and the resonance inductor reach resonance and is synchronously turned off with the fifth and eighth switching assemblies in response to the second control signal so as to charge the resonance capacitor by the induced current of the primary side winding during the turn-on period of the second switching assembly; and makes the fourth switching assembly turned on during the turn-on period of the sixth and seventh switching assemblies and starts to be turned on when the resonance capacitor and the resonance inductor reach resonance and is synchronously turned off with the sixth and seventh switching assemblies in response to the fourth control signal so as to charge the resonance capacitor by the induced current of the primary side winding during the turn-on period of the fourth switching assembly.

2. The bidirectional DC-DC power converter device according to claim 1, characterized in that The first to fourth switching assemblies are identical to each other, and each comprises a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

3. The bidirectional DC-DC converter as claimed in claim 1, characterized in that The fifth to eighth switching assemblies are identical to each other, and each comprises a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

4. The bidirectional DC-DC converter of claim 1, wherein The bidirectional DC-DC resonant converter further comprises a first filter capacitor and a second filter capacitor respectively connected across the first side and the second side.

5. A control method of a bidirectional DC-DC power conversion device as claimed in claim 1, characterized by, comprising the steps of: When the input voltage is converted from the first side to the output voltage outputted from the second side, in each control cycle of the first full-bridge chopper circuit: the first and fourth control signals are identical to each other; the second and third control signals are identical to each other and complementary to the first and fourth control signals; and a first dead time related to the switching speed of the first to fourth switching assemblies is inserted between the rising edge of one of the first / fourth control signals and the falling edge of the other one of the first / fourth control signals; When the input voltage is converted from the second side to the output voltage outputted from the first side and the control frequency of the fifth to eighth switching assemblies is higher than a resonant frequency related to the resonant capacitor and the resonant inductor with respect to the second side, in each control cycle of the second full-bridge chopper circuit: the fifth and eighth control signals are identical to each other; the sixth and seventh control signals are identical to each other and complementary to the fifth and eighth control signals; a second dead time related to the switching speed of the fifth to eighth switching assemblies is inserted between the rising edge of one of the fifth / eighth control signals and the falling edge of the other one of the fifth / eighth control signals; the second switching assembly is turned on according to the second control signal during the conduction period of the fifth and eighth switching assemblies and starts to conduct when the resonant capacitor and the resonant inductor reach resonance and is synchronously turned off with the fifth and eighth switching assemblies, so as to charge the resonant capacitor by the induced current of the primary side winding during the conduction period of the second switching assembly; and the fourth switching assembly is turned on according to the fourth control signal during the conduction period of the sixth and seventh switching assemblies and starts to conduct when the resonant capacitor and the resonant inductor reach resonance and is synchronously turned off with the sixth and seventh switching assemblies. When the input voltage is converted from the second side to the output voltage outputted from the first side and the control frequency of the fifth to eighth switching assemblies is lower than the resonant frequency, in each control cycle of the second full-bridge chopper circuit: the fifth and eighth control signals are identical to each other; the sixth and seventh control signals are identical to each other and complementary to the fifth and eighth control signals; a second dead time related to the switching speed of the fifth to eighth switching assemblies is inserted between the rising edge of one of the fifth / eighth control signals and the falling edge of the other one of the fifth / eighth control signals; the second switching assembly is turned on according to the second control signal during the conduction period of the fifth and eighth switching assemblies and starts to conduct when the resonant capacitor and the resonant inductor reach resonance and is synchronously turned off with the fifth and eighth switching assemblies, so as to charge the resonant capacitor by the induced current of the primary side winding during the conduction period of the second switching assembly; and the fourth switching assembly is turned on according to the fourth control signal during the conduction period of the sixth and seventh switching assemblies and starts to conduct when the resonant capacitor and the resonant inductor reach resonance and is synchronously turned off with the sixth and seventh switching assemblies. ​

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