A two-stage converter topology and control method

Abstract

The present invention provides a two-stage converter topology structure and control method, comprising a power supply, a DAB circuit, a Boost circuit, an input capacitor, and a load resistor; the power supply voltage, the actual voltage of the second multiplexed capacitor, and the actual output voltage of the DAB circuit are collected and input into a controller; the controller calculates the power supply voltage, the actual voltage of the second multiplexed capacitor, and the actual output voltage of the DAB circuit to obtain a PWM drive signal for each switch tube; the conduction time difference between the switch tube on the primary side and the switch tube on the secondary side in the DAB circuit is controlled by the PWM drive signal of each switch tube to adjust the output power of the two-stage converter; the conduction time of each switch tube in the Boost circuit is controlled by the PWM drive signal of each switch tube to adjust the voltage gain of the two-stage converter; and the power conversion efficiency is improved while having electrical isolation.

Description

Technical Field

[0001] The invention relates to the technical field of power electronic conversion, and in particular to a two-stage converter topology structure and a control method. Background Art

[0002] In recent years, with the development of new energy industry, power electronic converters have encountered higher challenges. More and more researchers have carried out a lot of research to pursue high power, high conversion efficiency and high power density of converters. As an important link in power conversion, DC converters have also become the focus of research.

[0003] In order to improve the power conversion efficiency and voltage regulation capability of the converter, the following solutions have been proposed:

[0004] Solution 1: Combine the boost converter (Boost) and the dual active bridge converter (DAB) in cascade, where the converter operates under the working condition of matching the primary and secondary voltages of the transformer to achieve electrical isolation and high-efficiency power conversion, and uses the Boost converter for voltage boosting; this solution is a two-stage topology structure, which has the advantages of simple structure and flexible control, but the two-stage structure leads to low power conversion efficiency.

[0005] Solution 2: Connect the DAB converter and the Boost converter in series input and parallel output, where the DAB converter works under voltage matching conditions and the Boost circuit adjusts the duty cycle to regulate the voltage. This solution has improved efficiency compared to the two-stage solution, but its topology does not have the function of electrical isolation. Summary of the invention

[0006] The present invention provides a two-stage converter topology structure and a control method, the purpose of which is to improve the power conversion efficiency while having electrical isolation.

[0007] In order to achieve the above object, the present invention provides a two-stage converter topology structure, comprising:

[0008] power supply;

[0009] A DAB circuit consisting of a first multiplexing capacitor, a first switch loop, a second switch loop, an external leakage inductor, a DC blocking capacitor, and a transformer;

[0010] A Boost circuit consisting of a third switch loop, a second multiplexing capacitor, and a first inductor;

[0011] Input capacitance;

[0012] Load resistance;

[0013] The positive electrode of the power supply is respectively connected to the first end of the input capacitor, the first end of the first inductor, and the first end of the first switch loop;

[0014] The negative electrode of the power supply is respectively connected to the second end of the input capacitor, the second end of the third switch loop, the second end of the second multiplexing capacitor, and the second end of the first switch loop;

[0015] The second end of the first inductor is respectively connected to the first end of the third switch loop and the first end of the first multiplexing capacitor;

[0016] The second end of the first multiplexed capacitor is connected to the first end of the external leakage inductor, and the second end of the external leakage inductor is connected to the first end of the transformer;

[0017] The third end of the third switch loop is connected to the first end of the second multiplexing capacitor and the third end of the first switch loop;

[0018] The fourth end of the first switch loop is connected to the second end of the transformer;

[0019] The third end of the transformer is connected to the first end of the second switch loop;

[0020] The fourth end of the transformer is connected to the second end of the second switch loop;

[0021] The third end of the second switch loop is connected to the first end of the DC blocking capacitor and the first end of the load;

[0022] The fourth end of the second switch loop is connected to the second end of the DC blocking capacitor and the second end of the load.

[0023] Specifically, the first switch loop includes:

[0024] A first switch tube, a second switch tube, a third switch tube, and a fourth switch tube;

[0025] The gate of the first switch tube, the gate of the second switch tube, the gate of the third switch tube, and the gate of the fourth switch tube are all connected to the output end of the controller, and the controller is used to control the switching of the switch tubes;

[0026] The drain of the first switch tube is connected to the third end of the third switch loop and the first end of the second multiplexing capacitor respectively, and the source of the first switch tube is connected to the drain of the second switch tube;

[0027] The source of the second switch tube is respectively connected to the second end of the third switch loop, the second end of the input capacitor, the negative electrode of the power supply, and the source of the fourth switch tube;

[0028] The drain of the third switch tube is respectively connected to the positive electrode of the power supply, the first end of the input capacitor, and the first end of the first inductor;

[0029] The source of the third switch tube is connected to the drain of the fourth switch tube and the second end of the transformer respectively.

[0030] Specifically, the second switch circuit includes:

[0031] a fifth switch tube, a sixth switch tube, a seventh switch tube, and an eighth switch tube;

[0032] The gate of the fifth switch tube, the gate of the sixth switch tube, the gate of the seventh switch tube, and the gate of the eighth switch tube are all connected to the output end of the controller;

[0033] The source of the fifth switch tube is connected to the third end of the transformer and the drain of the sixth switch tube respectively;

[0034] The drain of the fifth switch tube is respectively connected to the drain of the seventh switch tube, the first end of the DC blocking capacitor, and the first end of the load;

[0035] The source of the sixth switch tube is connected to the source of the eighth switch tube, the second end of the DC blocking capacitor, and the second end of the load respectively;

[0036] The source of the seventh switch tube is connected to the drain of the eighth switch tube and the fourth end of the transformer respectively.

[0037] Specifically, the third switch circuit includes:

[0038] a ninth switch tube and a tenth switch tube;

[0039] The gate of the ninth switch tube and the gate of the tenth switch tube are both connected to the output end of the controller;

[0040] The source of the ninth switch tube is respectively connected to the second end of the first inductor, the drain of the tenth switch tube, and the first end of the first multiplexing capacitor;

[0041] The drain of the ninth switch tube is connected to the first end of the second multiplexing capacitor and the drain of the first switch tube respectively;

[0042] The source of the tenth switch tube is respectively connected to the second end of the input capacitor, the negative electrode of the power supply, the source of the second switch tube, and the source of the fourth switch tube.

[0043] Furthermore, the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, and the tenth switch tube are all N-type MOS tubes with anti-parallel diodes and parasitic capacitors.

[0044] Further, the middle potential between the ninth switch tube and the tenth switch tube is the first middle potential;

[0045] The middle potential between the third switch tube and the fourth switch tube is a second middle potential;

[0046] The middle potential between the fifth switch tube and the sixth switch tube is a third middle potential;

[0047] The middle potential between the seventh switch tube and the eighth switch tube is a fourth middle potential.

[0048] Further, the gate of the ninth switch tube is used to receive the first adjustment signal sent by the controller, and the first adjustment signal is used to adjust the ratio of the conduction time and the switching period of the ninth switch tube, control the voltage across the second multiplexed capacitor, and change the amplitude of the first voltage to achieve voltage gain adjustment. The first voltage is the voltage between the first intermediate potential and the second intermediate potential.

[0049] Further, the gate of the first switch tube and the gate of the fifth switch tube are used to receive a second adjustment signal sent by the controller, and the second adjustment signal is used to adjust the phase difference between the first voltage and the second voltage by adjusting the ratio of the conduction time difference of the first switch tube and the fifth switch tube to the switching period to achieve output power regulation, and the second voltage is a voltage between the third intermediate potential and the fourth intermediate potential.

[0050] The present invention also provides a control method for a two-stage converter topology structure, which is applied to the two-stage converter topology structure. The control method comprises:

[0051] Step 1, collecting the power supply voltage, the actual voltage of the second multiplexing capacitor and the actual output voltage of the DAB circuit and inputting them into the controller;

[0052] Step 2, the controller calculates the power supply voltage, the actual voltage of the second multiplexing capacitor and the actual output voltage of the DAB circuit to obtain a PWM drive signal for each switch tube;

[0053] Step 3, controlling the conduction time difference between the primary switch tube and the secondary switch tube in the DAB circuit through the PWM drive signal of each switch tube, so as to adjust the output power of the two-stage converter;

[0054] Step 4, controlling the on-time of each switch tube in the Boost circuit through the PWM drive signal of each switch tube, and adjusting the voltage gain of the two-stage converter.

[0055] More specifically, step 2 includes:

[0056] Step 21, based on the formula Calculate the expected voltage of the second multiplexed capacitor ,in, Indicates the power supply voltage, represents the output voltage of a given DAB circuit, Indicates the transformation ratio of the transformer;

[0057] Step 22, obtaining a duty cycle of a ninth switch in the Boost circuit by inputting a first difference between an expected voltage of the second multiplexed capacitor and an actual voltage of the second multiplexed capacitor into a first digital PI regulator for adjustment;

[0058] Step 23, calculating a second difference between the actual output voltage and the expected value of the output voltage, and inputting the second difference into a second digital PI regulator for adjustment, to obtain a shift ratio between the first switch loop and the second switch loop in the DAB circuit;

[0059] Step 24, obtaining a PWM driving signal for each switch tube through a PWM generation unit according to the duty cycle and the shift ratio.

[0060] The above scheme of the present invention has the following beneficial effects:

[0061] The present invention designs a two-stage converter topology structure including a DAB circuit and a Boost circuit. Compared with the prior art, the present invention collects power supply voltage, the actual voltage of the second multiplexed capacitor and the actual output voltage of the DAB circuit and inputs them into a controller; the controller calculates the power supply voltage, the actual voltage of the second multiplexed capacitor and the actual output voltage of the DAB circuit to obtain a PWM drive signal for each switch tube; the conduction time difference between the switch tube on the primary side and the switch tube on the secondary side in the DAB circuit is controlled by the PWM drive signal of each switch tube, the output power of the two-stage converter is adjusted, and efficient electric energy conversion is achieved; the conduction time of each switch tube in the Boost circuit is controlled by the PWM drive signal of each switch tube, and the voltage gain of the two-stage converter is adjusted; it is ensured that within a wide voltage range, the DAB circuit can work in a voltage matching working mode, and efficient gain conversion is achieved, and the electric energy conversion efficiency is improved while having electrical isolation.

[0062] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A schematic diagram of a two-stage converter topology structure in an embodiment of the present invention;

[0064] Figure 2 It is a working waveform diagram of the two-stage converter topology structure in an embodiment of the present invention;

[0065] Figure 3 Schematic diagram of a control method in an embodiment of the present invention;

[0066] Figure 4 The flowchart of generating a PWM driving signal in an embodiment of the present invention is shown in FIG. DETAILED DESCRIPTION

[0067] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0068] In the description of the present invention, it should be noted that the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0069] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0071] In view of the existing problems, the present invention provides a two-stage converter topology structure and a control method.

[0072] like Figure 1 As shown, an embodiment of the present invention provides a two-stage converter topology structure, comprising:

[0073] power supply;

[0074] The first multiplexing capacitor C b , first switch loop, second switch loop, external leakage inductance L k , DC blocking capacitor C out , DAB circuit composed of transformer T;

[0075] The third switch circuit and the second multiplexing capacitor C a , the first inductor L a The Boost circuit composed of

[0076] Input Capacitor C in ;

[0077] Load R L resistance;

[0078] The positive pole of the power supply is connected to the input capacitor C in The first end of the first inductor L a and a first end of a first switch loop;

[0079] The negative pole of the power supply is connected to the input capacitor C in The second end of the third switch loop, the second multiplexing capacitor C a and a second end of the first switch loop;

[0080] The first inductor L a The second end of the third switch loop and the first multiplexing capacitor C b A first end is connected;

[0081] The first multiplexing capacitor C b The second end of the external leakage inductance L k The first end of the external leakage inductor L k The second end of is connected to the first end of the transformer T;

[0082] The third terminal of the third switch loop is connected to the second multiplexing capacitor C a The first end of the first switch loop is connected to the third end of the first switch loop;

[0083] The fourth end of the first switch loop is connected to the second end of the transformer T;

[0084] The third end of the transformer T is connected to the first end of the second switch loop;

[0085] The fourth end of the transformer T is connected to the second end of the second switch loop;

[0086] The third terminal of the second switch loop is connected to the DC blocking capacitor C out The first end of the load R L A first end is connected;

[0087] The fourth end of the second switch loop is connected to the DC blocking capacitor C out The second end of the load R L The second end of the connection.

[0088] In the embodiment of the present invention, the transformer T includes a primary winding and a secondary winding. The ratio of the primary winding to the secondary winding is the transformation ratio of the transformer T, and the transformation ratio = the number of turns of the primary winding / the number of turns of the secondary winding.

[0089] The DAB in the embodiment of the present invention undertakes all energy transmission tasks, and the primary side is composed of two bridge arms: the first switch tube S1 and the second switch tube S2 are directly connected to the output of the BOOST circuit, and the other bridge arm is directly connected to the input power supply. Therefore, from the perspective of energy transmission, the total energy is divided into two parts during transmission, and the BOOST circuit only bears part of the power. Therefore, the Boost circuit has a partial power transmission characteristic and can only transmit part of the system output power, which is beneficial to the improvement of the converter's power conversion efficiency.

[0090] Most preferably, the first switching circuit comprises:

[0091] A first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4;

[0092] The gate of the first switch tube S1, the gate of the second switch tube S2, the gate of the third switch tube S3, and the gate of the fourth switch tube S4 are all connected to the output end of the controller, and the controller is used to control the switching of the switch tubes;

[0093] The drain of the first switch tube S1 is respectively connected to the third end of the third switch loop and the second multiplexing capacitor C a The first end of the first switch tube S1 is connected to the drain of the second switch tube S2;

[0094] The source of the second switch tube S2 is connected to the second end of the third switch loop and the input capacitor C in The second end of the power supply is connected to the negative electrode of the power supply and the source electrode of the fourth switch tube S4;

[0095] The drain of the third switch tube S3 is connected to the positive electrode of the power supply and the input capacitor C in The first end of the first inductor L a A first end is connected;

[0096] The source of the third switch tube S3 is connected to the drain of the fourth switch tube S4 and the second end of the transformer T respectively.

[0097] Most preferably, the second switching circuit comprises:

[0098] a fifth switch tube Q1, a sixth switch tube Q2, a seventh switch tube Q3, and an eighth switch tube Q4;

[0099] The gate of the fifth switch tube Q1, the gate of the sixth switch tube Q2, the gate of the seventh switch tube Q3, and the gate of the eighth switch tube Q4 are all connected to the output end of the controller;

[0100] The source of the fifth switch tube Q1 is connected to the third end of the transformer T and the drain of the sixth switch tube Q2 respectively;

[0101] The drain of the fifth switch tube Q1 is connected to the drain of the seventh switch tube Q3 and the DC blocking capacitor C out The first end of the load R L A first end is connected;

[0102] The source of the sixth switch tube Q2 is connected to the source of the eighth switch tube Q4 and the DC blocking capacitor C out The second end of the load R L The second end of the connection;

[0103] The source of the seventh switch tube Q3 is connected to the drain of the eighth switch tube Q4 and the fourth end of the transformer T respectively.

[0104] Most preferably, the third switching circuit comprises:

[0105] The ninth switch tube S a , the tenth switch tube S b ;

[0106] The ninth switch tube S a The gate of the tenth switch tube S b The gates are all connected to the output terminal of the controller;

[0107] The ninth switch tube S a The source of the first inductor L a The second end of the tenth switch tube S b The drain of the first multiplexing capacitor C b A first end is connected;

[0108] The ninth switch tube S a The drain of a The first end of the first switch tube S1 is connected to the drain of the first switch tube S1;

[0109] The tenth switch tube S b The source of the input capacitor C in The second end of the transistor S2, the negative electrode of the power supply, the source of the second switch tube S2, and the source of the fourth switch tube S4 are connected.

[0110] Most preferably, the first switch tube S1, the second switch tube S2, the third switch tube S3, the fourth switch tube S4, the fifth switch tube Q1, the sixth switch tube Q2, the seventh switch tube Q3, the eighth switch tube Q4, the ninth switch tube S a , the tenth switch tube S b All use N-type MOS tubes with anti-parallel diodes and parasitic capacitance.

[0111] Most preferably, the ninth switch tube S a With the tenth switch tube S b The middle potential of is the first middle potential, and the embodiment of the present invention defines the first middle potential as point a;

[0112] The middle potential between the third switch tube S3 and the fourth switch tube S4 is the second middle potential. The second middle potential is defined as point b in the embodiment of the present invention.

[0113] The middle potential between the fifth switch tube Q1 and the sixth switch tube Q2 is a third middle potential. The third middle potential is defined as point c in the embodiment of the present invention.

[0114] The middle potential between the seventh switch tube Q3 and the eighth switch tube Q4 is a fourth middle potential. The embodiment of the present invention defines the fourth middle potential as point d.

[0115] In the embodiment of the present invention, the ninth switch tube S a The gate of the ninth switch tube S is used to receive the first adjustment signal sent by the controller, and the first adjustment signal is used to adjust the ninth switch tube S a The ratio of the on-time to the switching period controls the voltage across the second multiplexing capacitor and changes the first voltage u ab The amplitude of the first voltage u ab is a voltage between the first intermediate potential and the second intermediate potential.

[0116] In the embodiment of the present invention, the gate of the first switch tube S1 and the gate of the fifth switch tube Q1 are used to receive the second adjustment signal sent by the controller, and the second adjustment signal is used to adjust the first voltage u by adjusting the ratio of the conduction time difference between the first switch tube S1 and the fifth switch tube Q1 to the switching period. ab With the second voltage u cd The phase difference between them is used to adjust the output power, thereby achieving efficient power conversion. The second voltage u cd is a voltage between the third intermediate potential and the fourth intermediate potential.

[0117] Embodiments of the present invention are combined Figure 2 The working process of the two-stage converter topology structure is described as follows:

[0118] At time t0, the first switch tube S1, the fourth switch tube S4, and the ninth switch tube S a Zero voltage turn-on, the first inductor L a The current i La Linearly rising, at the same time, the external leakage inductance L k The current i Lk Linear rise;

[0119] At time t1, the fifth switch tube Q1 and the eighth switch tube Q4 are turned on with zero voltage, and the first inductor L a Current Continue to rise linearly. At the same time, due to the external leakage inductance L k The voltage on both sides is 0, and the external leakage inductance L k Current remains unchanged, it can be seen that at this time, because of the second multiplexing capacitor C a The voltage is adjusted to ensure that the DAB circuit works in a mode where the primary voltage and secondary voltage of the transformer T match, ensuring high efficiency of the system;

[0120] At time t2, the tenth switch tube S b Zero voltage turn-on, the ninth switch tube S a Zero voltage shutdown, the first inductor L a Current Linear decline;

[0121] At time t3, the second switch tube S2 and the third switch tube S3 are turned on with zero voltage, the first switch tube S1 and the fourth switch tube S4 are turned off with zero voltage, and the external leakage inductor L k Current Linear decline;

[0122] At time t4, the sixth switch tube Q2 and the seventh switch tube Q3 are turned on with zero voltage, the fifth switch tube Q1 and the eighth switch tube Q4 are turned off with zero voltage, and the first inductor L a Current Continue to decrease linearly, at the same time, the external leakage inductance L k Current Remain unchanged.

[0123] Among them, Figure 2 The waveform of the current during the working process shown in the figure, the t in the horizontal axis represents the unit time, and the value of t is t0, t1, ..., t4, DT s Indicates the conduction time of the switch tube. represents the first voltage u ab With the second voltage u cd The time difference between Figure 2 S5-S8 correspond to the fifth switch tube Q1 to the eighth switch tube Q4.

[0124] like Figure 3 As shown, the present invention also provides a control method for a two-stage converter topology structure, which is applied to the two-stage converter topology structure as described above, and the control method includes:

[0125] Step 1: Collect the power supply voltage V in , the second multiplexing capacitor C a The actual voltage V ca And the actual output voltage V of the DAB circuit o And enter the controller;

[0126] Step 2: The controller adjusts the power supply voltage V in , the second multiplexing capacitor C a The actual voltage V ca And the actual output voltage V of the DAB circuit o Calculate and obtain the PWM drive signal of each switch tube;

[0127] Step 3, controlling the conduction time difference between the primary switch tube and the secondary switch tube in the DAB circuit through the PWM drive signal of each switch tube, so as to adjust the output power of the two-stage converter;

[0128] Step 4, controlling the on-time of each switch tube in the Boost circuit through the PWM drive signal of each switch tube, and adjusting the voltage gain of the two-stage converter.

[0129] It should be noted that, in the embodiment of the present invention, the power supply voltage V in , the second multiplexing capacitor C a The actual voltage V ca And the actual output voltage V of the DAB circuit o They are all collected through voltage sensors and input into a controller for controlling the two-stage converter, which is a DSP controller.

[0130] Most preferably, Figure 4 As shown, step 2 includes:

[0131] Step 21, based on the formula The second multiplexing capacitor C is calculated a The expected voltage ,in, Indicates the power supply voltage, represents the output voltage of a given DAB circuit, Indicates the transformation ratio of transformer T;

[0132] Step 22, through the second multiplexing capacitor C a The expected voltage With the second multiplexing capacitor C a The actual voltage V ca The first difference is input into the first digital PI regulator (corresponding to Figure 4 PI_1 in the boost circuit is adjusted to obtain the ninth switch S a Duty cycle D;

[0133] Step 23, calculate the actual output voltage V o The expected value of the output voltage V ref The second difference is input into the second digital PI regulator (corresponding to Figure 4 The PI_2 in the DAB circuit is adjusted to obtain the shift ratio between the first switch loop and the second switch loop in the DAB circuit. ;

[0134] Step 24, according to the duty cycle D and the shift ratio , through the PWM generation unit, the PWM driving signal of each switch tube is obtained.

[0135] In the embodiment of the present invention, the controller can directly output the generated PWM drive signal to the gate of the switch tube in the two-stage converter to control the switching of the switch tube.

[0136] In the embodiment of the present invention, the conduction of the two switch tubes in the Boost circuit is a complementary relationship, and the control signals of the primary full-bridge switches S1~S4 and the secondary full-bridge switches Q1~~Q4 of the DAB circuit are square waves with a duty cycle of 0.5; the control signals of S1 and S4 are the same, the control signals of S2 and S3 are the same and complementary to the control signals of the switch devices S1 and S4; the control signals of Q1 and Q4 are the same, the control signals of Q2 and Q3 are the same and complementary to the control signals of Q1 and Q4; It is the phase shift ratio between the primary side switch control signal and the secondary side switch control signal (the phase deviation between the square waves). The phase shift ratio is calculated by the closed-loop controller and input into the control signal to drive the switch tube on and off.

[0137] In the embodiment of the present invention, the calculation expression of the output power of the two-stage converter is:

[0138]

[0139] in, Indicates the output power, Indicates the output voltage, represents the phase shift angle, that is, the ratio of the conduction time difference between the first switch tube S1 and the fifth switch tube Q1 to the switching period, represents the transformation ratio of transformer T, represents the switching frequency of transformer T, Indicates the inductance value.

[0140] In the embodiment of the present invention, the expression of the voltage gain of the two-stage converter is:

[0141] .

[0142] In order to verify the feasibility of the present invention, the following examples are used: Figure 1 The topology shown in the figure is used to build a 1000W two-stage converter prototype with an input voltage of 100V~300V and an output voltage of 400V. The driving signals of the DAB circuit and the Boost circuit are generated by the TI digital signal processor (DSP) TMS320F28377S. Under the experimental conditions, the two-stage converter can work normally in a closed loop under its control method, and realize electrical isolation and efficient power conversion. Moreover, the converter prototype can operate normally under different input voltages and different loads, indicating that the two-stage converter provided in the present application can make up for the shortcomings of the prior art and has the applicability under diverse working conditions.

[0143] The embodiment of the present invention designs a two-stage converter topology structure including a DAB circuit and a Boost circuit so that it has the advantages of both the Boost circuit and the DAB circuit. Compared with the prior art, the embodiment of the present invention collects the power supply voltage, the actual voltage of the second multiplexed capacitor and the actual output voltage of the DAB circuit and inputs them into the controller; the controller calculates the power supply voltage, the actual voltage of the second multiplexed capacitor and the actual output voltage of the DAB circuit to obtain the PWM drive signal of each switch tube; the conduction time difference between the switch tube on the primary side and the switch tube on the secondary side in the DAB circuit is controlled by the PWM drive signal of each switch tube, the output power of the two-stage converter is adjusted, and efficient electric energy conversion is achieved; the conduction time of each switch tube in the Boost circuit is controlled by the PWM drive signal of each switch tube, and the voltage gain of the two-stage converter is adjusted; it is ensured that within a wide voltage range, the DAB circuit can operate in a voltage matching working mode, achieve high-efficiency gain conversion, and improve the electric energy conversion efficiency while having electrical isolation.

[0144] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A two-stage converter topology, characterized in that: include: power supply; A DAB circuit consisting of a first multiplexing capacitor, a first switch loop, a second switch loop, an external leakage inductor, a DC blocking capacitor, and a transformer; A Boost circuit consisting of a third switch loop, a second multiplexing capacitor, and a first inductor; Input capacitance; Load resistance; The positive electrode of the power supply is respectively connected to the first end of the input capacitor, the first end of the first inductor, and the first end of the first switch loop; The negative electrode of the power supply is respectively connected to the second end of the input capacitor, the second end of the third switch loop, the second end of the second multiplexing capacitor, and the second end of the first switch loop; The second end of the first inductor is connected to the first end of the third switch loop and the first end of the first multiplexed capacitor respectively; The second end of the first multiplexed capacitor is connected to the first end of the external leakage inductor, and the second end of the external leakage inductor is connected to the first end of the transformer; The third end of the third switch loop is connected to the first end of the second multiplexing capacitor and the third end of the first switch loop; The fourth end of the first switch loop is connected to the second end of the transformer; The third end of the transformer is connected to the first end of the second switch loop; The fourth end of the transformer is connected to the second end of the second switch loop; The third end of the second switch loop is connected to the first end of the DC blocking capacitor and the first end of the load; The fourth end of the second switch loop is connected to the second end of the DC blocking capacitor and the second end of the load.

2. The two-stage converter topology structure according to claim 1, characterized in that: The first switch loop comprises: A first switch tube, a second switch tube, a third switch tube, and a fourth switch tube; The gate of the first switch tube, the gate of the second switch tube, the gate of the third switch tube, and the gate of the fourth switch tube are all connected to the output end of the controller, and the controller is used to control the switching of the switch tubes; The drain of the first switch tube is connected to the third end of the third switch loop and the first end of the second multiplexing capacitor respectively, and the source of the first switch tube is connected to the drain of the second switch tube; The source of the second switch tube is respectively connected to the second end of the third switch loop, the second end of the input capacitor, the negative electrode of the power supply, and the source of the fourth switch tube; The drain of the third switch tube is respectively connected to the positive electrode of the power supply, the first end of the input capacitor, and the first end of the first inductor; The source of the third switch tube is connected to the drain of the fourth switch tube and the second end of the transformer respectively.

3. The two-stage converter topology structure according to claim 2, characterized in that: The second switch loop comprises: a fifth switch tube, a sixth switch tube, a seventh switch tube, and an eighth switch tube; The gate of the fifth switch tube, the gate of the sixth switch tube, the gate of the seventh switch tube, and the gate of the eighth switch tube are all connected to the output end of the controller; The source of the fifth switch tube is connected to the third end of the transformer and the drain of the sixth switch tube respectively; The drain of the fifth switch tube is respectively connected to the drain of the seventh switch tube, the first end of the DC blocking capacitor, and the first end of the load; The source of the sixth switch tube is respectively connected to the source of the eighth switch tube, the second end of the DC blocking capacitor, and the second end of the load; The source of the seventh switch tube is connected to the drain of the eighth switch tube and the fourth end of the transformer respectively.

4. The two-stage converter topology structure according to claim 3, characterized in that: The third switch loop comprises: a ninth switch tube and a tenth switch tube; The gate of the ninth switch tube and the gate of the tenth switch tube are both connected to the output end of the controller; The source of the ninth switch tube is respectively connected to the second end of the first inductor, the drain of the tenth switch tube, and the first end of the first multiplexing capacitor; The drain of the ninth switch tube is connected to the first end of the second multiplexing capacitor and the drain of the first switch tube respectively; The source of the tenth switch tube is respectively connected to the second end of the input capacitor, the negative electrode of the power supply, the source of the second switch tube, and the source of the fourth switch tube.

5. The two-stage converter topology structure according to claim 4, characterized in that: The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube, the seventh switch tube, the eighth switch tube, the ninth switch tube, and the tenth switch tube are all N-type MOS tubes with anti-parallel diodes and parasitic capacitors.

6. The two-stage converter topology structure according to claim 5, characterized in that: The middle potential between the ninth switch tube and the tenth switch tube is a first middle potential; The middle potential between the third switch tube and the fourth switch tube is a second middle potential; The middle potential between the fifth switch tube and the sixth switch tube is a third middle potential; The middle potential between the seventh switch tube and the eighth switch tube is a fourth middle potential.

7. The two-stage converter topology structure according to claim 6, characterized in that: The gate of the ninth switch tube is used to receive the first adjustment signal sent by the controller, and the first adjustment signal is used to adjust the ratio of the conduction time and the switching period of the ninth switch tube, control the voltage across the second multiplexed capacitor, and change the amplitude of the first voltage to achieve voltage gain adjustment. The first voltage is the voltage between the first intermediate potential and the second intermediate potential.

8. The two-stage converter topology structure according to claim 7, characterized in that: The gate of the first switch tube and the gate of the fifth switch tube are used to receive a second adjustment signal sent by the controller, and the second adjustment signal is used to adjust the phase difference between the first voltage and the second voltage by adjusting the ratio of the conduction time difference of the first switch tube and the fifth switch tube to the switching period to achieve output power regulation, and the second voltage is a voltage between the third intermediate potential and the fourth intermediate potential.

9. A control method for a two-stage converter topology structure, characterized in that: Applied to the two-stage converter topology structure according to any one of claims 1 to 8, the control method comprises: Step 1, collecting the power supply voltage, the actual voltage of the second multiplexing capacitor and the actual output voltage of the DAB circuit and inputting them into the controller; Step 2, the controller calculates the power supply voltage, the actual voltage of the second multiplexing capacitor and the actual output voltage of the DAB circuit to obtain a PWM drive signal for each switch tube; Step 3, controlling the conduction time difference between the primary switch tube and the secondary switch tube in the DAB circuit through the PWM drive signal of each switch tube, so as to adjust the output power of the two-stage converter; Step 4: Control the on-time of each switch tube in the Boost circuit through the PWM drive signal of each switch tube to adjust the voltage gain of the two-stage converter.

10. The control method of the two-stage converter topology structure according to claim 9, characterized in that: The step 2 comprises: Step 21, based on the formula Calculate the expected voltage of the second multiplexed capacitor ,in, Indicates the power supply voltage, represents the output voltage of a given DAB circuit, Indicates the transformation ratio of the transformer; Step 22, obtaining a duty cycle of a third switch loop in the Boost circuit by obtaining a first difference between an expected voltage of the second multiplexed capacitor and an actual voltage of the second multiplexed capacitor and inputting the first difference into a first digital PI regulator for adjustment; Step 23, calculating a second difference between the actual output voltage and the expected value of the output voltage, and inputting the second difference into a second digital PI regulator for adjustment, to obtain a shift ratio between the first switch loop and the second switch loop in the DAB circuit; Step 24: Obtain a PWM driving signal for each switch tube through a PWM generation unit according to the duty cycle and the shift ratio.

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