Multi-mode DC-DC converter topological structure and control method thereof

Abstract

The invention provides a multi-mode DC-DC converter topological structure and a control method thereof, and the structure comprises a first switching power supply circuit which is connected to a high-voltage platform, and achieves the conversion between a DC voltage and an AC square wave voltage through a plurality of switching tubes which are in complementary conduction; the LLC resonant circuit realizes high-low voltage conversion through a resonant capacitor C1, a resonant inductor L1 and an excitation inductor; the BUCK circuit is used for outputting a first low voltage; and the second switching power supply circuit is connected to the tap of the secondary winding of the LLC resonant circuit and is used for outputting or inputting a second low voltage. According to the DC-DC converter topological structure, multiple working modes of conversion between high voltage and first low voltage and between high voltage and second low voltage can be achieved, a new energy automobile adopts the DC-DC converter with the topological structure, 800 V voltage can be converted into 12 V voltage to supply power to a small storage battery, meanwhile, reverse working can be achieved, pre-charging is conducted on the high-voltage side, and the power consumption of the new energy automobile is reduced. And 800V voltage can be converted into 48V voltage to supply power to the PDCC, so that the device is convenient and efficient, and has good economical efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle circuit design, and in particular relates to a multi-mode DC-DC converter topology structure and a control method thereof. Background Art

[0002] At present, the development of 800V platform models has gained wide favor. The high voltage side of this model is 800V, and the low voltage needs 12V output to power the small battery and 48V output to power the dynamic chassis PDCC. At the same time, the small battery needs to be reversely discharged to pre-charge the high voltage side. The design of its converter topology has a profound impact on the stability and reliability of high and low voltage conversion, and efficient, simple and low-cost circuit design is of great significance to the development of new energy vehicles.

[0003] Invention patent content

[0004] In view of the above problems, the present invention provides a multi-mode DC-DC converter topology structure and a control method thereof, which can realize multiple working modes of conversion between high voltage and first low voltage and second low voltage by setting a first switching power supply circuit, LLC resonant circuit, first rectifier circuit, and BUCK circuit and second switching power supply circuit on the high voltage side. New energy vehicles adopt a DC-DC converter with this topology structure, which can convert 800V voltage into 12V to power a small battery. At the same time, it can work in reverse to pre-charge the high voltage side, and can also convert 800V voltage into 48V to power the PDCC, which is convenient, efficient and economical. The purpose of the present invention is achieved through the following technical solutions:

[0005] The present invention first provides a multi-mode DC-DC converter topology structure, which includes:

[0006] The first switch power supply circuit is connected to the high-voltage platform, and realizes the conversion between the DC voltage and the AC square wave voltage through the circuit in which the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are complementary and turned on; that is, when the high voltage input is low voltage output, the high voltage DC voltage is converted into a square wave voltage; when the low voltage input is high voltage output, the high voltage square wave voltage is converted into a DC voltage;

[0007] LLC resonant circuit, which realizes high-low voltage conversion through resonant capacitor C1, resonant inductor L1 and the original excitation inductance of the transformer, and its primary winding is connected to the first switching power supply circuit side;

[0008] A BUCK circuit, used for outputting a first low voltage, connected to the secondary winding of the LLC resonant circuit, having a fifth switch tube S5, a sixth switch tube S6 and a first output capacitor, wherein the fifth switch tube S5 is connected in parallel with the first output capacitor, the sixth switch tube is connected in series with the first output capacitor, and the first output capacitor is connected to the first low voltage power demand end;

[0009] The second switching power supply circuit is connected to a tap of the secondary winding of the LLC resonant circuit and is used for outputting or inputting a second low voltage.

[0010] Furthermore, a filter capacitor C and an uncontrolled rectifier circuit are connected to the BUCK circuit.

[0011] Furthermore, the uncontrolled rectifier circuit adopts a full-bridge uncontrolled rectifier circuit, and the full-bridge uncontrolled rectifier circuit is provided with a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4.

[0012] Furthermore, the full-bridge uncontrolled rectifier circuit adopts a single-phase bridge circuit.

[0013] Furthermore, the second switching power supply circuit adopts a controllable full-bridge rectifier circuit, in which a seventh switch tube S7, an eighth switch tube S8, a ninth switch tube S9 and a tenth switch tube S10 are provided.

[0014] Furthermore, the LLC resonant circuit realizes a soft switching function by controlling a PWM wave with a variable input duty cycle.

[0015] Furthermore, the high voltage is 400V to 800V, the first low voltage is 48V, the second low voltage is 12V, and the second rectifier circuit is connected to a 1 / 4 tap of the secondary winding of the LLC resonant circuit to meet the needs of charging new energy vehicles, powering the dynamic chassis and a small battery, and reverse charging the high voltage platform through a small battery.

[0016] The working principle of the DC-DC converter with the topological structure of the present invention is: the high-voltage side is connected to a high-voltage (e.g., 800V) voltage platform, and the switch tubes S1, S4 and S2, S3 are alternately and complementary turned on, and the (e.g., 800V) high-voltage DC voltage is inverted into an (e.g., 800V) AC square wave voltage, and the square wave voltage acts on the LLC resonant circuit behind, so that the current periodically passes through the zero point, realizing the soft switching function of S1, S2, S3, S3, and reducing the loss of the switch tube. The two ends of the secondary transformer are connected with diodes D1, D2, D3, and D4 for full-bridge uncontrolled rectification, and a tap is added at 1 / 4 of the secondary transformer coil, and the switch tubes S7, S8, S9, and S10 are connected for controlled full-bridge rectification. When the high voltage (e.g., 800V) outputs the second low voltage (e.g., 12V) and the first low voltage (e.g., 48V) at the same time, the original switch tubes S1, S2, S3, and S4 mainly control the output voltage of the second low voltage (e.g., 12V). At this time, the BUCK converter composed of S5 and S6 controls the voltage output of the first voltage (e.g., 48V).

[0017] The present invention further provides a control method for a multi-mode DC-DC converter, comprising:

[0018] The first working mode, in which high voltage (e.g., 800V) is input and the first low voltage (e.g., 48V) is output, is specifically implemented as follows: the second switch power supply circuit is set in a non-working state, that is, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 are kept disconnected. At the same time, the first switch tube S1 of the first switch power supply circuit is started, and the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 are operated, and the LLC resonant circuit composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer is used to realize the soft switching function of the switch tubes S1 to S4. The four diodes of the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 form a full-bridge rectifier circuit, which is filtered by the capacitor C, and then the BUCK circuit is formed by S5 and S6 to adjust the voltage to the first low voltage (e.g., 48V) output. In this mode, the primary switches S1, S2, S3, S4 and the secondary switches S5, S6 can all control the first low voltage output to ensure that the input and output voltages can achieve stable output within a wide range.

[0019] The second working mode, in which high voltage (e.g., 800V) is input and the second low voltage (e.g., 12V) is output; the specific implementation method is: in this mode, the BUCK circuit is set in a non-working state, that is, the fifth switch tube S5 and the sixth switch tube S6 are disconnected. The first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 of the first switching power supply circuit are started to work, and the LLC resonant circuit is composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer to realize the soft switching function of the switch tubes S1 to S4. The 1 / 4 winding of the secondary transformer enters the circuit, and synchronous rectification is performed through the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 of the second switching power supply circuit. In this mode, the output of the second low voltage can be controlled by controlling the duty cycle of the switch tubes S1, S2, S3, and S4 in the first switching power supply circuit.

[0020] The third working mode, in this working mode, a high voltage (such as 800V) is input, and a first low voltage (such as 48V) and a second low voltage (such as 12V) are output simultaneously. The specific implementation of this mode is as follows: the switch tubes S1, S2, S3, and S4 are working, and the LLC resonant circuit is composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer to realize the soft switching function of the switch tubes S1 to S4. The stable output of the second low voltage can be controlled by controlling the duty cycle of the switch tubes S1, S2, S3, and S4 of the first switching power supply circuit. At the same time, the stable output of the first low voltage is controlled by the duty cycle of the switch tubes S5 and S6.

[0021] Further, the method also includes a fourth working mode, in which a second low voltage (e.g., 12V) is input and a first high voltage (e.g., 800V) is output. The specific implementation of this working mode is: in this mode, the BUCK circuit is set in a non-working state, that is, the fifth switch tube S5 and the sixth switch tube S6 are disconnected. The seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 in the second switching power supply circuit start working, and a square wave voltage is generated at both ends of the 1 / 4 winding of the secondary side of the transformer, and a square wave voltage is generated at the primary winding of the transformer. This voltage acts on the LLC resonant circuit to ensure the realization of the soft switching function of the switch tubes S7, S8, S9, and S10. The switch tubes S1, S2, S2, and S4 perform synchronous rectification to convert AC power into high-voltage DC power to achieve high-voltage DC output.

[0022] The beneficial effects of the present invention are:

[0023] (1) The transformer of the present invention adopts a tapping form in the LLC resonant circuit to achieve simultaneous output of two low voltages, which can save the cost of a transformer;

[0024] (2) In the present invention, in multiple modes of high voltage input, two low voltage outputs, and low voltage input and high voltage output, the four switch tubes S1, S2, S3, and S4 in the first switch power supply circuit can be reused, thereby saving costs;

[0025] (3) The present invention can realize two-way project conversion from low pressure to high pressure and from high pressure to low pressure, which is more flexible;

[0026] (4) The circuit design of the present invention can also achieve stable output control of the first low voltage through the BUCK converter when the second low voltage is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a schematic diagram of a multi-mode DC-DC converter topology structure in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The technical scheme of the preferred embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] This embodiment provides a multi-mode DC-DC converter topology structure, such as Figure 1 As shown, the high voltage is 400V to 800V, the first low voltage is 48V, and the second low voltage is 12V. The DC-DC converter includes:

[0031] The first switch power supply circuit is connected to the 800V high voltage platform, and realizes the conversion of 800V DC voltage and AC square wave voltage through the circuit of complementary conduction of the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4; that is, when the high voltage input is low voltage output, the high voltage DC voltage is converted into a square wave voltage; when the low voltage input is high voltage output, the high voltage square wave voltage is converted into a DC voltage;

[0032] LLC resonant circuit, which realizes high-low voltage conversion through resonant capacitor C1, resonant inductor L1 and the original excitation inductance of the transformer, and its primary winding is connected to the first switching power supply circuit side. The LLC resonant circuit realizes the soft switching function of the switch tube by controlling the input PWM wave with variable duty cycle;

[0033] A BUCK circuit is used to output a first low voltage, which is connected to the secondary winding of the LLC resonant circuit, and has a fifth switch tube S5, a sixth switch tube S6 and a first output capacitor, the fifth switch tube S5 is connected in parallel with the first output capacitor, the sixth switch tube is connected in series with the first output capacitor, and the first output capacitor is connected to the first low-voltage power demand end; in the illustrated embodiment, a filter capacitor C and an uncontrolled rectifier circuit are connected to the BUCK circuit, wherein the rectifier circuit adopts a full-bridge uncontrolled rectifier circuit, and the full-bridge uncontrolled rectifier circuit is provided with a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4 to form a single-phase bridge rectifier circuit.

[0034] The second switching power supply circuit is connected to the tap of the secondary winding of the LLC resonant circuit, and is used to output or input the second low voltage. In the illustrated embodiment, the second switching power supply circuit adopts a controllable full-bridge rectifier circuit composed of the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10; in the illustrated embodiment, in order to meet the power demand of the 48V low voltage of the dynamic chassis PDCC of the new energy vehicle and the 12V low voltage of the small battery, the second rectifier circuit is connected to the 1 / 4 tap of the secondary winding of the LLC resonant circuit to meet the needs of charging new energy vehicles, powering the dynamic chassis and the small battery, and reverse charging the high voltage platform through the small battery.

[0035] Embodiment 2:

[0036] This embodiment provides a control method for a multi-mode DC-DC converter, which is implemented by a DC-DC converter having the topological structure of Embodiment 1. The method includes:

[0037] The first working mode, in which high voltage (e.g., 800V) is input and the first low voltage (e.g., 48V) is output, is specifically implemented as follows: the second switch power supply circuit is set in a non-working state, that is, the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 are kept disconnected. At the same time, the first switch tube S1 of the first switch power supply circuit is started, and the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 are operated, and the LLC resonant circuit composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer is used to realize the soft switching function of the switch tubes S1 to S4. The four diodes of the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 form a full-bridge rectifier circuit, which is filtered by the capacitor C, and then the BUCK circuit is formed by S5 and S6 to adjust the voltage to the first low voltage (e.g., 48V) output. In this mode, the primary switches S1, S2, S3, S4 and the secondary switches S5, S6 can all control the first low voltage output to ensure that the input and output voltages can achieve stable output within a wide range.

[0038] The second working mode, in which high voltage (e.g., 800V) is input and the second low voltage (e.g., 12V) is output; the specific implementation method is: in this mode, the BUCK circuit is set in a non-working state, that is, the fifth switch tube S5 and the sixth switch tube S6 are disconnected. The first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 of the first switching power supply circuit are started to work, and the LLC resonant circuit is composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer to realize the soft switching function of the switch tubes S1 to S4. The 1 / 4 winding of the secondary transformer enters the circuit, and synchronous rectification is performed through the seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 of the second switching power supply circuit. In this mode, the output of the second low voltage can be controlled by controlling the duty cycle of the switch tubes S1, S2, S3, and S4 in the first switching power supply circuit.

[0039] The third working mode, in this working mode, a high voltage (such as 800V) is input, and a first low voltage (such as 48V) and a second low voltage (such as 12V) are output simultaneously. The specific implementation of this mode is as follows: the switch tubes S1, S2, S3, and S4 are working, and the LLC resonant circuit is composed of the resonant inductor L1, the resonant capacitor C1 and the original excitation inductance of the transformer to realize the soft switching function of the switch tubes S1 to S4. The stable output of the second low voltage can be controlled by controlling the duty cycle of the switch tubes S1, S2, S3, and S4 of the first switching power supply circuit. At the same time, the stable output of the first low voltage is controlled by the duty cycle of the switch tubes S5 and S6.

[0040] The fourth working mode, in this working mode, the second low voltage (such as 12V) is input and the first high voltage (such as 800V) is output. The specific implementation method of this working mode is: in this mode, the BUCK circuit is set in a non-working state, that is, the fifth switch tube S5 and the sixth switch tube S6 are disconnected. The seventh switch tube S7, the eighth switch tube S8, the ninth switch tube S9 and the tenth switch tube S10 in the second switching power supply circuit start working, and a square wave voltage is generated at both ends of the 1 / 4 winding of the secondary side of the transformer, and the primary winding of the transformer generates a square wave voltage. This voltage acts on the LLC resonant circuit to ensure the realization of the soft switching function of the switch tubes S7, S8, S9, and S10. The switch tubes S1, S2, S2, and S4 perform synchronous rectification to convert AC power into high-voltage DC power to achieve high-voltage DC output.

[0041] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention. The dimensions described in the drawings and embodiments are not related to the specific objects and are not used to limit the protection scope of the present invention. The dimensions of the objects can be selected and changed according to actual needs.

Claims

1. A multi-mode DC-DC converter topology, comprising: A first switch power supply circuit, which is connected to the high voltage platform, realizes the conversion between the DC voltage and the AC square wave voltage through the circuit in which the first switch tube S1, the second switch tube S2, the third switch tube S3, and the fourth switch tube S4 are complementary turned on; LLC resonant circuit, which realizes high-low voltage conversion through resonant capacitor C1, resonant inductor L1 and excitation inductor, and its primary winding is connected to the first switching power supply circuit side; a BUCK circuit, for outputting a first low voltage, connected to the secondary winding of the LLC resonant circuit, comprising a fifth switch tube S5, a sixth switch tube S6 and a first output capacitor, wherein the fifth switch tube S5 is connected in parallel with the first output capacitor, and the sixth switch tube is connected in series with the first output capacitor; The second switching power supply circuit is connected to a tap of the secondary winding of the LLC resonant circuit and is used for outputting or inputting a second low voltage.

2. A multi-mode DC-DC converter topology structure according to claim 1, characterized in that: The BUCK circuit is connected with a filter capacitor C and an uncontrolled rectifier circuit.

3. A multi-mode DC-DC converter topology structure according to claim 3, characterized in that: The uncontrolled rectifier circuit adopts a full-bridge uncontrolled rectifier circuit, and the full-bridge uncontrolled rectifier circuit is provided with a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4.

4. A multi-mode DC-DC converter topology structure according to claim 3, characterized in that: The full-bridge uncontrolled rectifier circuit adopts a single-phase bridge circuit.

5. A multi-mode DC-DC converter topology structure according to any one of claims 1 to 4, characterized in that: The second switch power supply circuit adopts a controllable full-bridge rectifier circuit, in which a seventh switch tube S7, an eighth switch tube S8, a ninth switch tube S9 and a tenth switch tube S10 are provided.

6. A multi-mode DC-DC converter topology structure according to any one of claims 1 to 5, characterized in that: The LLC resonant circuit realizes the soft switching function of the switch tube by controlling the input PWM wave with a variable duty cycle.

7. A multi-mode DC-DC converter topology structure according to any one of claims 1 to 6, characterized in that: The high voltage is 400V to 800V, the first low voltage is 48V, the second low voltage is 12V, and the second rectifier circuit is connected to a 1 / 4 tap of the secondary winding of the LLC resonant circuit.

8. A control method for a multi-mode DC-DC converter, comprising: A first working mode, in which a high voltage is input and a first low voltage is output; a second operating mode, in which a high voltage is input and a second low voltage is output; The third working mode is a working mode in which a high voltage is input and a first low voltage and a second low voltage are output simultaneously.

9. The control method of a multi-mode DC-DC converter according to claim 8, characterized in that: It also includes a fourth working mode, in which the second low voltage is input and the first high voltage is output.

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