LLC resonance boost control circuit and control method

Abstract

The invention discloses an LLC resonance boost control circuit and a control method, and belongs to the technical field of power electronics. The circuit comprises a bidirectional LLC resonant conversion unit and a DSP control unit which are connected in sequence. The bidirectional LLC resonant conversion unit comprises a low-voltage push-pull boost circuit, an LLC resonant circuit and a high-voltage full-bridge rectification circuit which are connected in sequence; the low-voltage push-pull booster circuit and the high-voltage full-bridge rectifier circuit are respectively connected with the DSP control unit; the low-voltage push-pull booster circuit is used for boosting the low-voltage direct current voltage and outputting boosted direct current; the LLC resonance circuit is used for boosting the boosting direct current and outputting boosting alternating current; the high-voltage full-bridge rectifying circuit is used for adjusting the amplitude of the boosted alternating current and outputting direct-current bus voltage; and the DSP control unit is used for controlling a zero-voltage switch of a switching tube in the low-voltage push-pull booster circuit to be switched on and a zero-current switch of a rectifier diode in the high-voltage full-bridge rectifier circuit to be switched off according to the resonant frequency of the bidirectional LLC resonant conversion unit. According to the circuit, ZVS switching-on of a switching tube and ZCS switching-off of a rectifier diode in the LLC resonant conversion unit are realized by adjusting the switching frequency, so that the inverter achieves high-efficiency discharge, the loss is reduced, and the service life of a power device is prolonged.

Description

Technical Field

[0001] The present application belongs to the field of power electronics technology, and in particular, relates to an LLC resonant boost control circuit and a control method. Background Art

[0002] When the inverter is started, if high voltage is directly applied to the load, a large inrush current will be generated, which may cause device damage and control system interference. However, soft start technology can gradually increase the output voltage, charge the capacitor slowly, reduce the inrush current, and protect the power device and the grid.

[0003] The current traditional synchronous full-bridge LCL circuit is the most widely used due to its high cost-effectiveness. During the soft-start process, the synchronous full-bridge LCL circuit uses the virtual current as a feedback signal to perform current closed-loop control, and switches to inductor current control after the control reaches a steady state. However, there is a defect of a large stress impact on the power tube device. Therefore, when this inverter works in a high current environment for a long time, the life of the power device will be greatly reduced. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes an LLC resonant boost control circuit and control method, which realizes ZVS turn-on of the switch tube and ZCS turn-off of the rectifier diode in the LLC resonant conversion unit by adjusting the switching frequency, so that the inverter can achieve high-efficiency discharge, reduce losses, and improve the life of power devices.

[0005] In a first aspect, the present application provides an LLC resonant boost control circuit, the circuit comprising:

[0006] A bidirectional LLC resonant conversion unit and a DSP control unit connected in sequence;

[0007] The bidirectional LLC resonant conversion unit comprises a low voltage push-pull boost circuit, an LLC resonant circuit and a high voltage full-bridge rectifier circuit connected in sequence;

[0008] The low voltage push-pull boost circuit and the high voltage full-bridge rectifier circuit are respectively connected to the DSP control unit;

[0009] The low voltage push-pull boost circuit is used to boost the low voltage DC voltage and output boosted DC power;

[0010] The LLC resonant circuit is used to boost the boosted DC power and output boosted AC power;

[0011] The high-voltage full-bridge rectifier circuit is used to adjust the amplitude of the boosted AC power and output a DC bus voltage;

[0012] The DSP control unit is configured to control the zero-voltage-switching conduction of the switching transistors in the low-voltage push-pull boost circuit and the zero-current-switching turn-off of the rectifying diodes in the high-voltage full-bridge rectifying circuit according to the resonance frequency of the bidirectional LLC resonance conversion unit.

[0013] According to an embodiment of the present application, the switching transistors in the low-voltage push-pull boost circuit include a low-voltage MOSFET switching transistor Q1 and a low-voltage MOSFET switching transistor Q2;

[0014] The LLC resonance circuit includes a boost transformer TX1;

[0015] The source electrodes of the low-voltage MOSFET switching transistor Q1 and the low-voltage MOSFET switching transistor Q2 are both connected to the low-voltage input terminal of the low-voltage push-pull boost circuit;

[0016] The drain electrode of the low-voltage MOSFET switching transistor Q1 is connected to the first end of the primary winding of the boost transformer TX1;

[0017] The second end of the primary winding of the boost transformer TX1 is connected to the high-voltage input terminal of the low-voltage push-pull boost circuit;

[0018] The drain electrode of the low-voltage MOSFET switching transistor Q2 is connected to the third end of the primary winding of the boost transformer TX1;

[0019] The secondary winding of the boost transformer TX1 is connected to the high-voltage full-bridge rectifying circuit.

[0020] According to an embodiment of the present application, the primary winding includes an auxiliary winding and an exciting winding. The opposite-named end of the auxiliary winding is connected to the first end of the primary winding. The same-named end of the auxiliary winding and the opposite-named end of the exciting winding are connected to the second end of the primary winding. The same-named end of the exciting winding is connected to the third end of the primary winding. The LLC resonance circuit further includes a resonance capacitor C1;

[0021] The opposite-named end of the secondary winding is connected to the first input terminal of the high-voltage full-bridge rectifying circuit through the resonance capacitor C1;

[0022] The opposite-named end of the secondary winding is connected to the second input terminal of the high-voltage full-bridge rectifying circuit.

[0023] According to an embodiment of the present application, the rectifying diodes in the high-voltage full-bridge rectifying circuit include a high-voltage IGBT switching transistor Q3, a high-voltage IGBT switching transistor Q4, a high-voltage IGBT switching transistor Q5, and a high-voltage IGBT switching transistor Q6;

[0024] The same-named ends of the secondary winding of the step-up transformer TX1 are respectively connected to the emitter of the high-voltage IGBT switch Q5 and the collector of the high-voltage IGBT switch Q6;

[0025] The collector of the high-voltage IGBT switch Q3 and the collector of the high-voltage IGBT switch Q5 are both connected to the BUS+ terminal of the high-voltage full-bridge rectifier circuit;

[0026] The emitter of the high-voltage IGBT switch Q4 and the emitter of the high-voltage IGBT switch Q6 are both connected to the terminal of the high-voltage full-bridge rectifier circuit.

[0027] According to an embodiment of the present application, the different-named ends of the secondary winding of the step-up transformer TX1 are respectively connected to the emitter of the high-voltage IGBT switch Q3 and the collector of the high-voltage IGBT switch Q4 through the resonance capacitor C1;

[0028] The same-named ends of the secondary winding of the step-up transformer TX1 are respectively connected to the emitter of the high-voltage IGBT switch Q5 and the collector of the high-voltage IGBT switch Q6.

[0029] According to an embodiment of the present application, the DSP control unit is respectively connected to the gates of the low-voltage MOSFET switch Q1, the low-voltage MOSFET switch Q2, the high-voltage IGBT switch Q3, the high-voltage IGBT switch Q4, the high-voltage IGBT switch Q5, and the high-voltage IGBT switch Q6.

[0030] According to an embodiment of the present application, the exciting winding is equivalent to an exciting inductance Lm, and the secondary winding is equivalent to a resonance inductance Lleak;

[0031] When the switching frequency f of the DSP control unit 120 is greater than the first resonance frequency fr of the resonance inductance Lleak and the resonance capacitor C1, the low-voltage MOSFET switches Q1 and Q2 are zero-voltage switches, and the resonance inductance Lleak and the resonance capacitor C1 undergo series resonance.

[0032] According to an embodiment of the present application, when the switching frequency f is equal to the second resonance frequency fm of the exciting inductance Lm, the resonance inductance Lleak, and the resonance capacitor C1, the low-voltage MOSFET switches Q1 and Q2 are zero-voltage switches, and the high-voltage IGBT switches Q3, Q4, Q5, and Q6 operate in the critical current mode and are zero-current switches.

[0033] According to an embodiment of the present application, when the switching frequency f is between the first resonance frequency fr and the second resonance frequency fm, and the resonance network composed of the exciting inductor Lm, the resonance inductor Lleak, and the resonance capacitor C1 operates in the inductive region, the low-voltage MOSFET switch tubes Q1 and Q2 are zero-voltage switches, and the high-voltage IGBT switch tubes Q3, Q4, Q5, and Q6 operate in the discontinuous mode and are zero-current switches.

[0034] In a second aspect, the present application provides an LLC resonant boost control method, which is applied to the LLC resonant boost control circuit as described in the first aspect. The method includes:

[0035] Boost the low-voltage DC voltage through the low-voltage push-pull boost circuit and output a boosted DC voltage.

[0036] Boost the boosted DC voltage through the LLC resonant circuit and output a boosted AC voltage.

[0037] Adjust the amplitude of the boosted AC voltage through the high-voltage full-bridge rectifier circuit and output a DC bus voltage.

[0038] Through the DSP control unit, according to the resonance frequency of the bidirectional LLC resonant conversion unit, control the zero-voltage switch conduction of the switch tubes in the low-voltage push-pull boost circuit and the zero-current switch turn-off of the rectifier diodes in the high-voltage full-bridge rectifier circuit.

[0039] The additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application.

[0040] An LLC resonant boost control circuit and control method provided by the present application have the following beneficial effects compared with the prior art:

[0041] (1) Through the collaborative work of the low-voltage push-pull boost circuit, the LLC resonant circuit, and the high-voltage full-bridge rectifier circuit, the low-voltage DC voltage of the battery is gradually boosted and stabilized to the required DC bus voltage, providing stable power support for the subsequent circuit. The DSP control unit ensures the efficient operation of the circuit and the stability of the output voltage through frequency adjustment and duty cycle control, reduces the switching loss through the soft switching technologies of ZVS and ZCS, improves the overall efficiency, especially performs excellently under light load and full load, realizes the ZVS turn-on of the switch tubes in the LLC resonant conversion unit and the ZCS turn-off of the rectifier diodes by adjusting the switching frequency, enables the inverter to achieve high-efficiency discharge, reduces the loss, and improves the service life of the power devices.

[0042] (2) The LLC resonant boost control circuit can maintain high-efficiency operation within a wide input voltage range, making it suitable for application scenarios with large input voltage fluctuations. The soft-switching technology reduces switching noise, electromagnetic interference, simplifies the low electromagnetic interference (EMI) filter design. High-frequency operation reduces the size of transformers and inductors, improves power density, and makes the design more compact. The LLC resonant boost control circuit can maintain a stable output voltage within a wide load range, has good load regulation ability, and is suitable for occasions with large load variations. High efficiency reduces heat generation, decreases the heat dissipation requirement, and simplifies the heat dissipation design. The soft-switching technology reduces switching stress, improves the reliability and lifespan of the circuit, and can be applied to the design of inverter products. Brief Description of the Drawings

[0043] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0044] Figure 1 is one of the schematic structural diagrams of the LLC resonant boost control circuit provided by an embodiment of the present application;

[0045] Figure 2 is another schematic structural diagram of the LLC resonant boost control circuit provided by an embodiment of the present application;

[0046] Figure 3 is the schematic flowchart of the LLC resonant boost control method provided by an embodiment of the present application;

[0047] Reference Signs:

[0048] Bidirectional LLC resonant conversion unit 110; Low-voltage push-pull boost circuit 111; LLC resonant circuit 112; High-voltage full-bridge rectifier circuit 113; DSP control unit 120. Detailed Description of the Embodiments

[0049] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0050] The terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of this application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the description and claims means at least one of the connected objects, and the character " / ", generally represents an "or" relationship between the associated objects before and after.

[0051] The LLC resonant boost control circuit and the LLC resonant boost control method provided by the embodiments of this application will be described in detail below with reference to the accompanying drawings through specific embodiments and their application scenarios.

[0052] As Figure 1 shown, the LLC resonant boost control circuit includes:

[0053] A bidirectional LLC resonant conversion unit 110 and a DSP control unit 120 connected in sequence;

[0054] The bidirectional LLC resonant conversion unit 110 includes a low-voltage push-pull boost circuit 111, an LLC resonant circuit 112, and a high-voltage full-bridge rectifier circuit 113 connected in sequence;

[0055] The low-voltage push-pull boost circuit 111 and the high-voltage full-bridge rectifier circuit 113 are respectively connected to the DSP control unit 120;

[0056] The low-voltage push-pull boost circuit 111 is used to boost the low-voltage DC voltage and output a boosted DC voltage;

[0057] The LLC resonant circuit 112 is used to boost the boosted DC voltage and output a boosted AC voltage;

[0058] The high-voltage full-bridge rectifier circuit 113 is used to adjust the amplitude of the boosted AC voltage and output a DC bus voltage;

[0059] The DSP control unit 120 is used to control the switch tube in the low-voltage push-pull boost circuit 111 to conduct with zero voltage switching and the rectifier diode in the high-voltage full-bridge rectifier circuit 113 to turn off with zero current switching according to the resonant frequency of the bidirectional LLC resonant conversion unit 110.

[0060] Among them, the low-voltage DC voltage is provided by a low-voltage battery pack, and the output DC bus voltage (BUS voltage) is a stable DC output voltage, which is used to control the inrush current when starting the power supply or load of the inverter, ensure the output voltage rises smoothly, and avoid damage to the power supply and load.

[0061] The high-voltage full-bridge rectifier circuit 113 is an H-bridge circuit.

[0062] During the soft start of the circuit, on the one hand, the duty cycle of the switching device can be gradually increased through the PWM signal to make the output BUS voltage rise slowly, thereby reducing the inrush current during startup. On the other hand, during the startup phase, the charging current of the capacitor can be controlled through the PWM signal to make the BUS voltage rise gradually.

[0063] The low-voltage push-pull boost circuit 111 is used to control the alternating conduction or cut-off of the switching tubes, boost the input low-voltage DC voltage to a predetermined high-voltage DC power, achieve push-pull boosting, and provide a stable input voltage for the subsequent LLC resonant circuit as the boosted DC power.

[0064] For example, in an electric vehicle charging system, the low-voltage push-pull boost circuit can boost the low voltage of the battery to a higher voltage and provide a stable input for the subsequent LLC resonant circuit.

[0065] The LLC resonant circuit 112 is used to further boost the voltage. Utilizing the characteristics of the resonant inductor, resonant capacitor, and excitation inductor, the circuit operates at a specific resonant frequency, and through the resonant characteristics, zero-voltage switching (ZVS) and zero-current switching (ZCS) are carried out, converting the input boosted DC power into a stable boosted AC power and outputting it, reducing the switching loss, improving the efficiency, and achieving efficient energy conversion.

[0066] The LLC resonant circuit 112 is also used to make the output voltage stable by adjusting the operating frequency and changing the voltage division ratio of the resonant network.

[0067] The high-voltage full-bridge rectifier circuit 113 is used to adjust the amplitude of the boosted AC power by controlling the conduction and cut-off of the rectifier diodes to obtain a stable DC bus voltage, that is, the BUS voltage.

[0068] The DSP control unit 120 is used to control the ZVS conduction of the switching tubes in the low-voltage push-pull boost circuit 111 and the ZCS cut-off of the rectifier diodes in the high-voltage full-bridge rectifier circuit according to the resonant frequency of the bidirectional LLC resonant conversion unit 110.

[0069] The DSP control unit 120 is also used to adjust the operating frequency of the bidirectional LLC resonant conversion unit 110 by monitoring the operating state of the bidirectional LLC resonant conversion unit 110, ensuring that the LLC resonant boost control circuit operates near the optimal resonant frequency, achieving efficient energy conversion, and taking timely measures to protect the circuit and load when detecting abnormal situations (such as overvoltage, overcurrent, etc.); controlling the amplitude of the output voltage by adjusting the duty cycle of the switching tubes to ensure the stability of the BUS voltage.

[0070] According to the LLC resonant boost control circuit provided by the embodiments of the present application, through the collaborative operation of the low-voltage push-pull boost circuit, the LLC resonant circuit, and the high-voltage full-bridge rectifier circuit, the low-voltage DC voltage of the battery is gradually boosted and stabilized to the required DC bus voltage, providing stable power support for the subsequent circuit. The DSP control unit ensures the efficient operation of the circuit and the stability of the output voltage through frequency adjustment and duty cycle control, reduces the switching loss through the soft-switching technologies of ZVS and ZCS, improves the overall efficiency, especially performs excellently under light load and full load, realizes the ZVS turn-on of the switching tubes and the ZCS turn-off of the rectifier diodes in the LLC resonant conversion unit by adjusting the switching frequency, enables the inverter to achieve high-efficiency discharge, reduces the loss, and improves the service life of the power devices.

[0071] It should be noted that in the LCL resonant main power circuit in the related art, an inductor, a capacitor C, and an inductor L form an LCL circuit. The cost of the LLC resonant circuit is lower than that of the LCL resonant circuit. In the LLC resonant converter, the switching tubes can be turned on through zero-voltage switching (ZVS), and the output rectifier diodes can also be turned off through zero-current switching (ZCS), thereby minimizing the loss and improving the service life of the power devices. Therefore, high-frequency, high-power-density, and high-efficiency converters become feasible. Therefore, using LLC resonance to achieve soft switching significantly reduces the switching loss, extends the service life of the power devices, reduces a certain cost, and improves the overall efficiency.

[0072] In some embodiments, as Figure 2 shown, the switching tubes in the low-voltage push-pull boost circuit 111 include a low-voltage MOSFET switching tube Q1 and a low-voltage MOSFET switching tube Q2;

[0073] The LLC resonant circuit 112 includes a boost transformer TX1;

[0074] The source electrodes of the low-voltage MOSFET switching tube Q1 and the low-voltage MOSFET switching tube Q2 are both connected to the low-voltage input terminal BAT- of the low-voltage push-pull boost circuit 111;

[0075] The drain electrode of the low-voltage MOSFET switching tube Q1 is connected to the first end of the primary winding of the boost transformer TX1;

[0076] The second end of the primary winding of the boost transformer TX1 is connected to the high-voltage input terminal BAT+ of the low-voltage push-pull boost circuit 111;

[0077] The drain electrode of the low-voltage MOSFET switching tube Q2 is connected to the third end of the primary winding of the boost transformer TX1;

[0078] The secondary winding of the boost transformer TX1 is connected to the high-voltage full-bridge rectifier circuit 113.

[0079] Among them, the model of the step-up transformer TX1 is MAX 90A. The first end of the primary winding of the step-up transformer TX1 is terminal 2, the second end of the primary winding of the step-up transformer TX1 is terminal 5, and the third end of the primary winding of the step-up transformer TX1 is terminal 1.

[0080] The models of the low-voltage MOSFET switching transistors Q1 and Q2 are TK100E10N1.

[0081] Through the alternating conduction of the two low-voltage MOSFET switching transistors in the low-voltage push-pull step-up circuit 111, the input low voltage is stepped up to a predetermined high-voltage direct current. The conduction and cut-off of the MOSFET are controlled by the DSP control unit to achieve push-pull step-up.

[0082] In actual implementation, when Q1 conducts, the current flows from BAT+ through the second end (terminal 5) of the primary winding to the drain of Q1, and then to the first end (terminal 2) of the primary winding, forming a magnetic flux; when Q2 conducts, the current flows from BAT+ through the second end (terminal 5) of the primary winding to the drain of Q2, and then to the third end (terminal 1) of the primary winding, forming a reverse magnetic flux; this alternating conduction method induces a high-voltage alternating current in the secondary winding of the transformer, and a high-voltage direct current is obtained after rectification.

[0083] In this embodiment, through the alternating conduction of the two low-voltage MOSFET switching transistors in the low-voltage push-pull step-up circuit 111, the input low voltage can be efficiently stepped up to a predetermined high-voltage direct current to provide stable power support for the subsequent circuit.

[0084] In some embodiments, the primary winding includes an auxiliary winding and an exciting winding. The opposite-named end of the auxiliary winding is connected to the first end of the primary winding, the same-named end of the auxiliary winding and the opposite-named end of the exciting winding are connected to the second end of the primary winding, the same-named end of the exciting winding is connected to the third end of the primary winding, and the LLC resonant circuit 112 further includes a resonant capacitor C1;

[0085] The opposite-named end of the secondary winding is connected to the first input end of the high-voltage full-bridge rectification circuit 113 through the resonant capacitor C1;

[0086] The opposite-named end of the side winding is connected to the second input end of the high-voltage full-bridge rectification circuit 113.

[0087] Among them, the model of the resonant capacitor C1 is 0.1 μF 630V.

[0088] The opposite ends of the auxiliary winding are connected to terminal 2, the same ends of the auxiliary winding and the opposite ends of the exciting winding are connected to terminal 5, the same ends of the exciting winding are connected to terminal 1, the opposite ends of the secondary winding are connected to terminal 4, and the same ends of the secondary winding are connected to terminal 3.

[0089] The exciting winding is equivalent to an exciting inductance Lm, and the secondary winding is equivalent to a resonant inductance Lleak.

[0090] In actual implementation, the LLC resonant circuit 112 utilizes the characteristics of the exciting inductance Lm, the resonant capacitor C1, and the resonant inductance Lleak to make the circuit operate at a specific frequency, operate near the resonant frequency, achieve zero-voltage switching (ZVS) of the primary switching tube and zero-current switching (ZCS) of the secondary rectifier diode, reduce switching losses, and improve efficiency; it also adjusts the operating frequency to change the voltage division ratio of the resonant network, making the output voltage stable.

[0091] In this embodiment, through the collaborative operation of the low-voltage push-pull boost circuit, the LLC resonant circuit, and the high-voltage full-bridge rectifier circuit, the low voltage of the battery is gradually boosted and stabilized to the required BUS voltage. The DSP control unit ensures the efficient operation of the circuit and the stability of the output voltage through frequency adjustment and duty cycle control, and finally outputs a stable DC bus voltage to provide stable power support for the subsequent circuit.

[0092] In some embodiments, the rectifier diodes in the high-voltage full-bridge rectifier circuit 113 include high-voltage IGBT switching tubes Q3, Q4, Q5, and Q6;

[0093] The same ends of the secondary winding of the boost transformer TX1 are respectively connected to the emitter (E pole) of the high-voltage IGBT switching tube Q5 and the collector (C pole) of the high-voltage IGBT switching tube Q6;

[0094] The collector (C pole) of the high-voltage IGBT switching tube Q3 and the collector (C pole) of the high-voltage IGBT switching tube Q5 are both connected to the BUS+ terminal of the high-voltage full-bridge rectifier circuit 113;

[0095] The emitter (E pole) of the high-voltage IGBT switching tube Q4 and the emitter (E pole) of the high-voltage IGBT switching tube Q6 are both connected to the BUS- terminal of the high-voltage full-bridge rectifier circuit 113.

[0096] In some embodiments, the opposite ends of the secondary winding of the boost transformer TX1 are connected to the emitter (E pole) of the high-voltage IGBT switching tube Q3 and the collector (C pole) of the high-voltage IGBT switching tube Q4 through the resonant capacitor C1 respectively;

[0097] The same - name ends of the secondary winding of the step - up transformer TX1 are respectively connected to the emitter (E - pole) of the high - voltage IGBT switch Q5 and the collector (C - pole) of the high - voltage IGBT switch Q6.

[0098] In some embodiments, the DSP control unit 120 is respectively connected to the gate (G - pole) of the low - voltage MOSFET switch Q1, the gate (G - pole) of the low - voltage MOSFET switch Q2, the gate (G - pole) of the high - voltage IGBT switch Q3, the gate (G - pole) of the high - voltage IGBT switch Q4, the gate (G - pole) of the high - voltage IGBT switch Q5, and the gate (G - pole) of the high - voltage IGBT switch Q6.

[0099] Among them, the models of the high - voltage IGBT switches Q3, Q4, Q5, and Q6 are CRG20T60A93L.

[0100] The high - voltage full - bridge rectifier circuit 113 rectifies the boosted alternating current into a stable DC bus voltage through the alternating conduction and cut - off of four IGBTs.

[0101] In actual execution, the DSP control unit 120 generates a PWM signal according to the working state of the circuit to control the conduction and turn - off of Q3, Q4, Q5, and Q6, realizing full - bridge rectification. By adjusting the duty cycle of the PWM signal, the amplitude of the output voltage is controlled to ensure the stability of the BUS voltage. In the startup stage, by gradually increasing the duty cycle of the PWM signal, the output voltage rises slowly, reducing the inrush current during startup.

[0102] When the high - voltage IGBT switch Q3 and the high - voltage IGBT switch Q6 are conducting, the current flows from the opposite - name end of the secondary winding through the capacitor C1 to the emitter of the high - voltage IGBT switch Q3, then to the collector of Q3, and finally to the BUS + terminal; the current also flows from the BUS - terminal to the emitter of the high - voltage IGBT switch Q6, and then through the collector of the high - voltage IGBT switch Q6 to the same - name end of the secondary winding.

[0103] When the high - voltage IGBT switch Q4 and the high - voltage IGBT switch Q5 are conducting, the current flows from the BUS - terminal to the emitter of Q4, and then through the collector of the high - voltage IGBT switch Q4 through the capacitor C1 to the opposite - name end of the secondary winding; the current also flows from the same - name end of the secondary winding to the emitter of the high - voltage IGBT switch Q5, then to the collector of the high - voltage IGBT switch Q4, and finally to the BUS + terminal.

[0104] This alternating - conduction method induces a high - voltage alternating current in the secondary winding of the step - up transformer TX1, and after rectification, a high - voltage direct current is obtained.

[0105] The DSP control unit 120 can also monitor the working state of the circuit in real time. When abnormal conditions such as overvoltage and overcurrent are detected, it takes timely measures to protect the circuit and the load.

[0106] For example, the DSP control unit 120 monitors the current in the LLC resonant boost control circuit through a current sensor. When the current exceeds the set threshold, the DSP control unit 120 immediately turns off the IGBT to protect the circuit; it monitors the output voltage through a voltage sensor. When the voltage exceeds the set threshold, the DSP control unit 120 immediately adjusts the duty cycle of the PWM signal to reduce the output voltage; when a short - circuit situation is detected, the DSP control unit 120 immediately turns off the IGBT to cut off the circuit and protect the load and the circuit.

[0107] In some embodiments, the exciting winding is equivalent to an exciting inductance Lm, and the secondary winding is equivalent to a resonant inductance Lleak;

[0108] When the switching frequency f of the DSP control unit 120 is greater than the first resonant frequency fr of the resonant inductance Lleak and the resonant capacitor C1, the low - voltage MOSFET switches Q1 and Q2 are zero - voltage switches, and the resonant inductance Lleak and the resonant capacitor C1 have a series resonance.

[0109] In some embodiments, when the switching frequency f is equal to the second resonant frequency fm of the exciting inductance Lm, the resonant inductance Lleak and the resonant capacitor C1, the low - voltage MOSFET switches Q1 and Q2 are zero - voltage switches, and the high - voltage IGBT switches Q3, Q4, Q5, and Q6 operate in the critical - current mode and are zero - current switches.

[0110] In some embodiments, when the switching frequency f is between the first resonant frequency fr and the second resonant frequency fm, and the resonant network composed of the exciting inductance Lm, the resonant inductance Lleak, and the resonant capacitor C1 operates in the inductive region, the low - voltage MOSFET switches Q1 and Q2 are zero - voltage switches, and the high - voltage IGBT switches Q3, Q4, Q5, and Q6 operate in the discontinuous mode and are zero - current switches.

[0111] It can be understood that the LLC resonant circuit 112 can ensure that the startup current of the G poles of the high-voltage IGBT switching tubes Q3, Q4, Q5, and Q6 in the high-voltage full-bridge rectifier circuit 113 can slowly change from 0 A to the current within the specified range, so that the current of the entire loop of the high-voltage full-bridge rectifier circuit 113 is within the controllable current range. When the high-voltage DC bus voltage reaches the control target, the switching frequency remains unchanged, and the duty cycle of the two-level signal control is 50% in a complementary form and then works normally.

[0112] The DSP control unit 120 is used to output control signals (PWM1 / PWM2), and the control signals gradually increase the frequency conversion modulation of the low-voltage push-pull boost circuit 111 according to the voltage grading of the DC bus;

[0113] The low-voltage MOSFET switching tubes Q1 and Q2 are the main power switching tubes, the boost transformer TX1 is the main power transformer, the excitation inductor Lm, the resonant capacitor C1, and the resonant inductor Lleak form the resonant network of the LLC resonant converter, and the high-voltage IGBT switching tubes Q3, Q4, Q5, and Q6 act as rectifier diodes;

[0114] The boost transformer TX1 in the LLC resonant circuit 112 includes two inductors, the resonant inductor Lleak and the excitation inductor Lm, corresponding to two resonant frequencies respectively. One is the first resonant frequency fr of the resonant inductor Lleak and the resonant capacitor C1, and the other is the second resonant frequency fm formed by the excitation inductor Lm, the resonant inductor Lleak, and the resonant capacitor C1.

[0115] When the switching frequency f of the DSP control unit 120 is greater than fr, the switching tubes Q1 and Q2 on the primary winding side of the LLC resonant converter can achieve zero voltage switching (ZVS) under any load. However, since the transformer excitation inductor is always clamped by the output voltage, only Lleak and the resonant capacitor C1 have a series resonance, and the diode cannot achieve zero current switching (ZCS), resulting in reverse recovery losses.

[0116] When the switching frequency f = fm, the LLC resonant converter operates in a full-resonance state. The switching tubes Q1 and Q2 on the primary winding side can achieve ZVS, and the rectifier diode operates in the critical current mode. At this time, the ZCS of the rectifier diode can be achieved, eliminating the losses caused by the reverse recovery of the diode;

[0117] When the resonant frequency fm < f < fr and the resonant network operates in the inductive region, zero-voltage switching (ZVS) is achieved on the primary winding side of the LLC converter, and the current flowing through the output rectifier diode operates in the discontinuous mode, achieving zero-current switching (ZCS) for the rectifier diode, eliminating the losses caused by diode reverse recovery.

[0118] When Q1 conducts, PWM1 sends a high-level signal, and PWM2 is a complementary signal. At this time, the low-voltage side voltage is boosted by the transformer TX1, and the LLC resonant circuit 112 starts to resonate. The resonant current Is flowing through the resonant capacitor C1 starts to rise from 0 A and flows through the freewheeling diodes of the power transistors Q3 / Q6 in the high-voltage full-bridge rectifier circuit 113. Since the generated resonant current starts from 0 A, the freewheeling diodes of Q3 / Q6 have zero-loss ZCS; when Q1 turns off, due to the inertia of the magnetizing inductor Lm, the current does not stop immediately. At this time, the current of the magnetizing inductor Lm charges or discharges the capacitor through the resonant capacitor C1 (including the parasitic capacitance of the switching transistors). Resonance is formed between the inductor and the capacitor, and the resonant current Is gradually reduces the voltage on the resonant capacitor C1. As the resonant capacitor C1 discharges, the voltage across the low-voltage MOSFET switching transistors Q1 / Q2 gradually decreases until it approaches zero. When the voltage on the resonant capacitor C1 approaches zero, the voltage across the switch becomes extremely small, and at this time, the switching transistor on the primary winding can achieve ZVS conduction. Since the voltage is close to zero, the loss of the switch during conduction is very low.

[0119] In this embodiment, the LLC resonant boost control circuit can maintain high efficiency within a wide input voltage range, making it suitable for application scenarios with large input voltage fluctuations. The soft-switching technology reduces switching noise, decreases electromagnetic interference, simplifies the low-electromagnetic-interference (EMI) filter design. High-frequency operation reduces the size of the transformer and inductor, improves the power density, making the design more compact. The LLC resonant boost control circuit can maintain a stable output voltage within a wide load range, has good load regulation ability, and is suitable for occasions with large load changes. High efficiency reduces heat generation, decreases the heat dissipation requirement, and simplifies the heat dissipation design. The soft-switching technology reduces switching stress, improves the reliability and lifespan of the circuit, and can be applied to the design of inverter products.

[0120] In some embodiments, the present application further provides an LLC resonant boost control method, which is applied to the LLC resonant boost control circuit provided in any of the above embodiments.

[0121] As Figure 3 shown, the LLC resonant boost control method includes:

[0122] Step 310, boost the low-voltage DC voltage through the low-voltage push-pull boost circuit to output boosted direct current.

[0123] Step 320: Boost the boosted direct current through the LLC resonant circuit and output boosted alternating current.

[0124] Step 330: Adjust the amplitude of the boosted alternating current through the high-voltage full-bridge rectifier circuit and output the DC bus voltage.

[0125] Step 340: Through the DSP control unit, according to the resonant frequency of the bidirectional LLC resonant conversion unit, control the zero-voltage-switching conduction of the switching tube in the low-voltage push-pull boost circuit and the zero-current-switching turn-off of the rectifier diode in the high-voltage full-bridge rectifier circuit.

[0126] According to the LLC resonant boost control method provided by the embodiments of the present application, through the collaborative work of the low-voltage push-pull boost circuit, the LLC resonant circuit, and the high-voltage full-bridge rectifier circuit, the low-voltage DC voltage of the battery is gradually boosted and stabilized to the required DC bus voltage, providing stable power support for the subsequent circuit. The DSP control unit ensures the efficient operation of the circuit and the stability of the output voltage through frequency adjustment and duty cycle control, reduces the switching loss through the soft switching technologies of ZVS and ZCS, improves the overall efficiency, especially performs excellently under light load and full load, realizes the ZVS turn-on of the switching tube and the ZCS turn-off of the rectifier diode in the LLC resonant conversion unit by adjusting the switching frequency, enables the inverter to achieve high-efficiency discharge, reduces the loss, and prolongs the service life of the power devices.

[0127] The inverter provided by the embodiments of the present application can implement each process realized by the LLC resonant boost control circuit embodiment in the above embodiments. To avoid repetition, it will not be elaborated here.

[0128] In the description of the present application, the "first feature" and "second feature" may include one or more of such features.

[0129] In the description of the present application, the meaning of "a plurality" is two or more.

[0130] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all of them belong to the protection scope of the present application.

[0131] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0132] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. An LLC resonant boost control circuit, characterized in that: include: A bidirectional LLC resonant conversion unit and a DSP control unit connected in sequence; The bidirectional LLC resonant conversion unit comprises a low voltage push-pull boost circuit, an LLC resonant circuit and a high voltage full-bridge rectifier circuit connected in sequence; The low voltage push-pull boost circuit and the high voltage full-bridge rectifier circuit are respectively connected to the DSP control unit; The low voltage push-pull boost circuit is used to boost the low voltage DC voltage and output boosted DC power; The LLC resonant circuit is used to boost the boosted DC power and output boosted AC power; The high-voltage full-bridge rectifier circuit is used to adjust the amplitude of the boosted AC power and output a DC bus voltage; The DSP control unit is used to control the zero-voltage switch conduction of the switch tube in the low-voltage push-pull boost circuit and the zero-current switch turn-off of the rectifier diode in the high-voltage full-bridge rectifier circuit according to the resonant frequency of the bidirectional LLC resonant conversion unit.

2. The LLC resonant boost control circuit according to claim 1, characterized in that: The switch tubes in the low-voltage push-pull boost circuit include a low-voltage MOSFET switch tube Q1 and a low-voltage MOSFET switch tube Q2; The LLC resonant circuit includes a step-up transformer TX1; The source of the low-voltage MOSFET switch tube Q1 and the source of the low-voltage MOSFET switch tube Q2 are both connected to the low-voltage input end of the low-voltage push-pull boost circuit; The drain of the low voltage MOSFET switch tube Q1 is connected to the first end of the primary winding of the boost transformer TX1; The second end of the primary winding of the boost transformer TX1 is connected to the high voltage input end of the low voltage push-pull boost circuit; The drain of the low voltage MOSFET switch tube Q2 is connected to the third end of the primary winding of the boost transformer TX1; The secondary winding of the step-up transformer TX1 is connected to the high-voltage full-bridge rectifier circuit.

3. The LLC resonant boost control circuit according to claim 2, characterized in that: The primary winding includes an auxiliary winding and an excitation winding, the opposite-name end of the auxiliary winding is connected to the first end of the primary winding, the same-name end of the auxiliary winding and the opposite-name end of the excitation winding are connected to the second end of the primary winding, and the same-name end of the excitation winding is connected to the third end of the primary winding. The LLC resonant circuit also includes a resonant capacitor C1; The opposite-signal end of the secondary winding is connected to the first input end of the high-voltage full-bridge rectifier circuit through the resonant capacitor C1; The opposite-name end of the side winding is connected to the second input end of the high-voltage full-bridge rectifier circuit.

4. The LLC resonant boost control circuit according to claim 3, characterized in that: The rectifier diodes in the high-voltage full-bridge rectifier circuit include a high-voltage IGBT switch tube Q3, a high-voltage IGBT switch tube Q4, a high-voltage IGBT switch tube Q5 and a high-voltage IGBT switch tube Q6; The same-name ends of the secondary winding of the step-up transformer TX1 are respectively connected to the emitter of the high-voltage IGBT switch tube Q5 and the collector of the high-voltage IGBT switch tube Q6; The collector of the high-voltage IGBT switch tube Q3 and the collector of the high-voltage IGBT switch tube Q5 are both connected to the BUS+ terminal of the high-voltage full-bridge rectifier circuit; The emitter of the high-voltage IGBT switch tube Q4 and the emitter of the high-voltage IGBT switch tube Q6 are both connected to the end of the high-voltage full-bridge rectifier circuit.

5. The LLC resonant boost control circuit according to claim 4, characterized in that: The opposite-end resonant capacitor C1 of the secondary winding of the step-up transformer TX1 is connected to the emitter of the high-voltage IGBT switch tube Q3 and the collector of the high-voltage IGBT switch tube Q4 respectively; The same-name ends of the secondary winding of the step-up transformer TX1 are respectively connected to the emitter of the high-voltage IGBT switch tube Q5 and the collector of the high-voltage IGBT switch tube Q6.

6. The LLC resonant boost control circuit according to claim 5, characterized in that: The DSP control unit is respectively connected to the gate of the low-voltage MOSFET switch tube Q1, the gate of the low-voltage MOSFET switch tube Q2, the gate of the high-voltage IGBT switch tube Q3, the gate of the high-voltage IGBT switch tube Q4, the gate of the high-voltage IGBT switch tube Q5 and the gate of the high-voltage IGBT switch tube Q6.

7. The LLC resonant boost control circuit according to claim 5, characterized in that: The excitation winding is equivalent to the excitation inductance Lm, and the secondary winding is equivalent to the resonant inductance Lleak; When the switching frequency f of the DSP control unit 120 is greater than the first resonant frequency fr of the resonant inductor Lleak and the resonant capacitor C1, the low-voltage MOSFET switch tube Q1 and the low-voltage MOSFET switch tube Q2 are zero-voltage switches, and the resonant inductor Lleak and the resonant capacitor C1 resonate in series.

8. The LLC resonant boost control circuit according to claim 7, characterized in that: When the switching frequency f is equal to the second resonant frequency fm of the excitation inductance Lm, the resonant inductance Lleak and the resonant capacitor C1, the low-voltage MOSFET switch tube Q1 and the low-voltage MOSFET switch tube Q2 are zero-voltage switches, and the high-voltage IGBT switch tube Q3, the high-voltage IGBT switch tube Q4, the high-voltage IGBT switch tube Q5 and the high-voltage IGBT switch tube Q6 operate in the critical current mode and are zero-current switches.

9. The LLC resonant boost control circuit according to claim 8, characterized in that: When the switching frequency f is between the first resonant frequency fr and the second resonant frequency fm, and the resonant network composed of the excitation inductance Lm, the resonant inductance Lleak and the resonant capacitor C1 operates in the inductive region, the low-voltage MOSFET switch tube Q1 and the low-voltage MOSFET switch tube Q2 are zero-voltage switches, and the high-voltage IGBT switch tube Q3, the high-voltage IGBT switch tube Q4, the high-voltage IGBT switch tube Q5 and the high-voltage IGBT switch tube Q6 operate in discontinuous mode and are zero-current switches.

10. An LLC resonant boost control method, characterized in that: Applied to the LLC resonant boost control circuit according to any one of claims 1 to 9, the method comprising: The low voltage DC voltage is boosted by the low voltage push-pull boost circuit to output boosted DC power; The boosted direct current is boosted by the LLC resonant circuit to output boosted alternating current; The boosted AC power is amplitude-regulated by the high-voltage full-bridge rectifier circuit to output a DC bus voltage; Through the DSP control unit, according to the resonant frequency of the bidirectional LLC resonant conversion unit, the zero voltage switch of the switch tube in the low-voltage push-pull boost circuit is controlled to be turned on and the zero current switch of the rectifier diode in the high-voltage full-bridge rectifier circuit is controlled to be turned off.

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