Energy conversion device and system

Abstract

The application provides an energy conversion device and system, and relates to the technical field of electric power. The energy conversion device comprises a transformer, an LC resonant series half-bridge structure circuit coupled to a high-voltage side winding of the transformer, and a full-bridge rectifier circuit coupled to a low-voltage side winding of the transformer. The energy conversion device and system provided by the application embodiment can realize efficient pre-charging function without an additional active absorption circuit, can not only reduce the cost of the energy conversion device, but also reduce the space and volume occupied by the energy conversion device and improve the integration; and the energy conversion device can reduce the large current impact in the charging process, can improve the stress problem of the switching tube during large current charging, can make the whole charging process more stable, and can improve the reliability of reverse charging.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to an energy conversion device and system. Background Technology

[0002] Figure 1 This is a circuit topology diagram of a commonly used automotive DC / DC converter module. For example... Figure 1 As shown, the bidirectional operation of the DC / DC converter can be used to enable the low-voltage battery of a new energy vehicle to reverse precharge the high-voltage bus capacitor. However, due to the requirement of short precharge time, the reverse working current of the DC / DC converter is relatively large, resulting in a large turn-off current of the low-voltage side MOSFET and high stress in the low-voltage side MOSFET. Current solutions are to add an additional active absorption circuit to improve the stress problem of the MOSFET. Utility Model Content

[0003] In order to solve at least one of the above-mentioned problems in the prior art, this application provides an energy conversion device and system.

[0004] This application provides an energy conversion device, including: a transformer; an LC resonant series half-bridge circuit coupled to the high-voltage side winding of the transformer; and a full-bridge rectifier circuit coupled to the low-voltage side winding of the transformer.

[0005] In some embodiments, the LC resonant series half-bridge structure circuit includes an LC resonant circuit and a series half-bridge structure circuit; wherein, the first end of the LC resonant circuit is coupled to the first end of the series half-bridge structure circuit, and the second end of the LC resonant circuit is coupled to the high-voltage side winding; the second end of the series half-bridge structure circuit is coupled to the first energy storage device.

[0006] In some embodiments, the series half-bridge structure circuit includes: a switching bridge arm, including a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor connected in series; and a capacitor bridge arm, including a first capacitor and a second capacitor connected in series; wherein, the two ends of the capacitor bridge arm are respectively connected to the two ends of the switching bridge arm, and the midpoint between the first capacitor and the second capacitor is coupled to the midpoint between the second switching transistor and the third switching transistor, and the two ends of the capacitor bridge arm are also coupled in parallel to the two ends of the first energy storage device.

[0007] In some embodiments, the LC resonant circuit includes a resonant inductor and a resonant capacitor; wherein, a first end of the resonant capacitor is coupled to the midpoint between the first switch and the second switch, the other end of the resonant capacitor is coupled to the first end of the resonant inductor, and a second end of the resonant capacitor is coupled to the first end of the high-voltage side winding; the midpoint between the third switch and the fourth switch is coupled to the second end of the high-voltage side winding.

[0008] In some embodiments, the input terminal of the full-bridge rectifier circuit is coupled to a second energy storage device, and the output terminal of the full-bridge rectifier circuit is coupled to the low-voltage winding of the transformer.

[0009] In some embodiments, a filter capacitor is further included, which is connected in parallel to the input terminal of the full-bridge rectifier circuit.

[0010] In some embodiments, the first energy storage device includes a capacitor, and the second energy storage device includes a battery.

[0011] This application provides an energy conversion system, including a first energy storage device, a second energy storage device, and the energy conversion device described in any of the above embodiments, wherein the first energy storage device, the energy conversion device, and the second energy storage device are connected in sequence.

[0012] In some embodiments, the device further includes: a data acquisition device coupled to the first energy storage device and the full-bridge rectifier circuit, configured to acquire the input current of the full-bridge rectifier circuit and the voltage of the first energy storage device in real time, and generate a sampled current value and a sampled voltage value based on the input current of the full-bridge rectifier circuit and the voltage of the first energy storage device; a control device coupled to the data acquisition device, the LC resonant series half-bridge structure circuit and the full-bridge rectifier circuit, configured to generate a drive signal for the switching transistors in the LC resonant series half-bridge structure circuit and the full-bridge rectifier circuit based on the sampled current value and the sampled voltage value; and a drive device coupled to the control device, the LC resonant series half-bridge structure circuit and the full-bridge rectifier circuit, configured to drive the switching transistors in the LC resonant series half-bridge structure circuit and the full-bridge rectifier circuit to turn on and off based on the drive signal, so that the second energy storage device charges the first energy storage device with a set current.

[0013] In some embodiments, the control device includes: a voltage control loop module coupled to the acquisition device, configured to generate a first output signal based on the sampled voltage value and a voltage reference value after the voltage of the first energy storage device reaches a target voltage value; a smaller value unit coupled to the voltage control loop module, configured to compare the first output signal and a set current value to obtain the smaller value between the first output signal and the set current value; a current control loop module coupled to the smaller value unit and the acquisition device, configured to generate a second output signal based on the smaller value and the sampled current value; and a control unit coupled to the acquisition device, the current control loop module, the LC resonant series half-bridge structure circuit, the full-bridge rectifier circuit, and the drive... The control unit is configured to: before the voltage of the first energy storage device reaches the target voltage value, generate drive signals for the switching transistors in the LC resonant series half-bridge circuit and the full-bridge rectifier circuit based on the sampled voltage value, so that the drive device drives the switching transistors to turn on and off based on the drive signals, thereby enabling the second energy storage device to charge the first energy storage device with the set current; after the voltage of the first energy storage device reaches the target voltage value, generate drive signals for the switching transistors based on the sampled voltage value and the second output signal, so that the drive device drives the switching transistors to turn on and off based on the drive signals, thereby maintaining the voltage of the first energy storage device at the target voltage value.

[0014] In some embodiments, the driving signal includes a first PWM signal, a second PWM signal, a third PWM signal, and a fourth PWM signal; the driving device includes: a first driving unit, respectively coupled to the control unit and the LC resonant series half-bridge structure circuit, configured to drive the switching on and off of two switches in the LC resonant series half-bridge structure circuit based on the third PWM signal, and to drive the switching on and off of the other two switches in the LC resonant series half-bridge structure circuit based on the fourth PWM signal; and a second driving unit, respectively coupled to the control unit and the full-bridge rectifier circuit, configured to drive the switching on and off of two switches in the full-bridge rectifier circuit based on the first PWM signal, and to drive the switching on and off of the other two switches in the full-bridge rectifier circuit based on the second PWM signal.

[0015] The energy conversion device and system proposed in this application embodiment do not require an additional active absorption circuit and can achieve a highly efficient pre-charge function. This not only reduces the cost of the energy conversion device but also reduces the space and volume occupied by the energy conversion device, thereby improving the integration. Furthermore, the energy conversion device can reduce the impact of large currents during the charging process, improve the stress problem of the switching transistor during high-current charging, make the entire charging process more stable, and thus improve the reliability of reverse charging. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a circuit topology diagram of a commonly used vehicle-mounted DC / DC converter module.

[0018] Figure 2 This is a circuit topology diagram of an energy conversion device provided in an embodiment of this application.

[0019] Figure 3 This is a schematic diagram of the circuit topology of an energy conversion system provided in an embodiment of this application.

[0020] Figure 4 This is a comparative schematic diagram of the voltage control curve of the first energy storage device and the control curve of the low-voltage side current of the energy conversion device during a reverse pre-charging process provided in an embodiment of this application.

[0021] Figure 5 This is a schematic diagram of the driving logic of the switching transistors at each stage of the reverse precharge process provided in an embodiment of this application.

[0022] Figure 6 This is a timing diagram of the electrical parameters of the high-voltage side and low-voltage side of the energy conversion device during the switching cycle of stage 2 provided in the embodiments of this application.

[0023] Figure 7 This is a schematic diagram of the switching process during the switching cycle of stage 2 provided in the embodiments of this application.

[0024] Figure 8 This is a schematic diagram of the ZCS switching state of the low-voltage side switch tube of the stage 3 energy conversion device provided in the embodiment of this application.

[0025] Figure 9 This is a timing diagram of the electrical parameters of the high-voltage side and low-voltage side of the energy conversion device during the switching cycle of stage 3 provided in the embodiments of this application.

[0026] Figure 10 This is a schematic diagram of the switching process during the switching cycle of stage 3 provided in the embodiments of this application.

[0027] Figure 11 This is a schematic diagram of the state of the low-voltage side switching tubes S1 to S4 of the energy conversion device provided in this application embodiment when stress is generated. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] The term "coupled (or connected)" as used throughout the entire specification (including the claims) may refer to any direct or indirect means of connection. For example, if the text describes a first device coupled (or connected) to a second device, it should be interpreted as the first device being directly connected to the second device, or the first device being indirectly coupled to the second device through other devices or some means of connection. The terms "first," "second," etc., used throughout the entire specification (including the claims) are used to name components, and are not intended to limit the upper or lower limit of the number of components, nor to limit the order of components. Furthermore, wherever possible, components / components / steps using the same reference numerals in the drawings and embodiments represent the same or similar parts. Components / components / steps using the same reference numerals or the same terms in different embodiments may be referred to mutually in the relevant descriptions.

[0030] Figure 2 This is a schematic diagram of the circuit topology of an energy conversion device provided in an embodiment of this application. For example... Figure 2 As shown, the energy conversion device 100 provided in this application embodiment includes: a transformer TR; an LC resonant series half-bridge structure circuit 10 coupled to the high-voltage side winding of the transformer TR; and a full-bridge rectifier circuit 20 coupled to the low-voltage side winding of the transformer TR.

[0031] The energy conversion device 100 provided in this application embodiment does not require an additional active absorption circuit, and can achieve a highly efficient pre-charge function. This not only reduces the cost of the energy conversion device, but also reduces the space and volume occupied by the energy conversion device, and improves the integration. Furthermore, the energy conversion device 100 can reduce the impact of large currents during the charging process, improve the stress problem of the switching transistor during high-current charging, make the entire charging process more stable, and thus improve the reliability of reverse charging. For details, please refer to the description below.

[0032] like Figure 2 As shown, in some embodiments, the LC resonant series half-bridge structure circuit 10 includes an LC resonant circuit 11 and a series half-bridge structure circuit 12; wherein, the first end of the LC resonant circuit 11 is coupled to the first end of the series half-bridge structure circuit 12, and the second end of the LC resonant circuit 11 is coupled to the high-voltage side winding of the transformer TR; the second end of the series half-bridge structure circuit 12 is coupled to the first energy storage device (target capacitor C1).

[0033] like Figure 2 As shown, in some embodiments, the series half-bridge structure circuit 12 includes: a switching bridge arm, including a first switching transistor Q1, a second switching transistor Q2, a third switching transistor Q3, and a fourth switching transistor Q4 connected in series; and a capacitor bridge arm, including a first capacitor C2 and a second capacitor C3 connected in series; wherein, the two ends of the capacitor bridge arm are respectively connected to the two ends of the switching bridge arm, and the midpoint between the first capacitor C2 and the second capacitor C3 is coupled to the midpoint between the second switching transistor Q2 and the third switching transistor Q3, and the two ends of the capacitor bridge arm are also coupled in parallel to the two ends of the target capacitor C1.

[0034] like Figure 2 As shown, in some embodiments, the LC resonant circuit 11 includes a resonant inductor Lr and a resonant capacitor Crp; wherein, the first end of the resonant capacitor Crp is coupled to the midpoint a between the first switch Q1 and the second switch Q2, the other end of the resonant capacitor Crp is coupled to the first end of the resonant inductor Lr, and the second end of the resonant capacitor Crp is coupled to the first end of the high-voltage winding of the transformer TR; the midpoint b between the third switch Q3 and the fourth switch Q4 is coupled to the second end of the high-voltage winding.

[0035] like Figure 2 As shown, in some embodiments, the input terminal of the full-bridge rectifier circuit 20 is coupled to the second energy storage device, and the output terminal of the full-bridge rectifier circuit 20 is coupled to the low-voltage side winding of the transformer TR.

[0036] For example, such as Figure 2As shown, in some embodiments, the full-bridge rectifier circuit 20 includes a fifth switch S1, a sixth switch S2, a seventh switch S3, and an eighth switch S4; the midpoint c between the fifth switch S1 and the sixth switch S2 is coupled to the first end of the low-voltage winding of the transformer TR, the midpoint d between the seventh switch S3 and the eighth switch S4 is coupled to the second end of the low-voltage winding of the transformer TR, the midpoint between the fifth switch S1 and the seventh switch S3 is coupled to the first end of the second energy storage device, and the midpoint between the sixth switch S2 and the eighth switch S4 is coupled to the second end of the second energy storage device.

[0037] like Figure 2 As shown, in some embodiments, the energy conversion device 100 further includes: a filter capacitor C O Filter capacitor C O It is connected in parallel to the input terminal of the full-bridge rectifier circuit 20. Filter capacitor C O Used for energy storage and filtering.

[0038] like Figure 2 As shown, in some embodiments, the first energy storage device includes a capacitor (capacitor C1), and the second energy storage device includes a battery. Specifically, the energy conversion device 100 can be applied to new energy vehicles, specifically for pre-charging the bus capacitor on the high-voltage battery side of the new energy vehicle. In this case, the capacitor can be the bus capacitor connected in parallel with the high-voltage battery of the new energy vehicle, and the battery can be the low-voltage battery of the new energy vehicle.

[0039] Figure 3 This is a schematic diagram of the circuit topology of an energy conversion system provided in an embodiment of this application. For example... Figure 3 As shown, the energy conversion system 200 provided in this application embodiment includes: a first energy storage device (target capacitor C1), a second energy storage device (not shown in the figure), and the energy conversion device described in any of the above embodiments, wherein the first energy storage device, the energy conversion device, and the second energy storage device are connected in sequence.

[0040] like Figure 3 As shown, in some embodiments, the energy conversion system 200 further includes:

[0041] The data acquisition device 30, coupled to the target capacitor C1 and the full-bridge rectifier circuit 20, is configured to acquire in real time the input current Iin of the full-bridge rectifier circuit 20 and the voltage V of the target capacitor C1. HV Based on the input current Iin of the full-bridge rectifier circuit 20 and the voltage V of the target capacitor C1, HV This generates the sampled current value Isen_LV and the sampled voltage value Vsen_HV.

[0042] The control device 40, coupled to the acquisition device 30, the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20, is configured to generate drive signals for the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20 based on the sampled current value Isen_LV and the sampled voltage value Vsen_HV.

[0043] The driving device 50, coupled to the control device 40, the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20, is configured to drive the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20 to turn on and off based on the driving signal, so that the second energy storage device charges the target capacitor C1 with a set current.

[0044] like Figure 3 As shown, in some embodiments, the control device 40 includes:

[0045] The voltage control loop module 41, coupled to the acquisition device 30, is configured to generate a first output signal VAO based on the sampled voltage value Vsen_HV and the voltage reference value Vref_HV after the voltage of the target capacitor C1 reaches the target voltage value Vset. The function of the voltage control loop module 41 is to maintain the output voltage of the energy conversion device within the set value, which is usually achieved through proportional-integral control.

[0046] Small unit 42 is coupled to the voltage control loop module 41 and is configured to compare the first output signal VAO and the set current value Iref_set to obtain the smaller value Iref between the first output signal VAO and the set current value Iref_set.

[0047] The current control loop module 43, coupled to the smaller sampling unit 41 and the acquisition device 30, is configured to generate a second output signal CAO based on the smaller value Iref and the sampled current value Isen_LV. The function of the current control loop module 43 is to maintain the input current of the energy conversion device within a set value, which is usually achieved through proportional-integral control.

[0048] Control unit 44, coupled to the acquisition device 30, the current control loop module 43, the LC resonant series half-bridge circuit 10, the full-bridge rectifier circuit 20, and the drive device 50, is configured as follows:

[0049] The voltage V of the target capacitor C1 HVBefore the target voltage value Vset is reached, based on the sampled voltage value Vsen_HV, drive signals are generated for the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20, so that the drive device 50 drives the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20 to turn on and off based on the drive signals, thereby enabling the second energy storage device to charge the target capacitor C1 with the set current;

[0050] The voltage V of the target capacitor C1 HV After reaching the target voltage value Vset, based on the sampled voltage value Vsen_HV and the second output signal CAO, drive signals are generated for the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20. This causes the driving device 50 to drive the switching transistors in the LC resonant series half-bridge circuit 10 and the full-bridge rectifier circuit 20 to turn on and off based on the drive signals, thereby increasing the voltage V of the target capacitor C1. HV Maintain at the target voltage value Vset.

[0051] like Figure 3 As shown, in some embodiments, the acquisition device 30 may specifically include:

[0052] High-voltage side voltage sampling unit 31, coupled to the control unit 44 and the target capacitor C1, is used to acquire the voltage V of the target capacitor C1. HV And based on the voltage V of the target capacitor C1 HV Generate the sampled voltage value Vsen_HV;

[0053] The resonant current sampling unit 32 is coupled to the LC resonant circuit 11 and the control unit 44, and is used to collect the resonant current.

[0054] The low-voltage side current sampling unit 33 is coupled to the full-bridge rectifier circuit 20 and the control unit 44, and is used to collect the input current Iin of the full-bridge rectifier circuit 20 and generate a sampling current value Isen_LV based on the input current Iin;

[0055] The low-voltage side voltage sampling unit 34 is coupled to the full-bridge rectifier circuit 20 and the control unit 44, and is used to acquire the input voltage V on the low-voltage side. LV And based on the input voltage V LV Generate the low-voltage side sampling voltage Vsen_LV.

[0056] like Figure 3As shown, in some embodiments, the driving signal includes a first PWM signal, a second PWM signal, a third PWM signal, and a fourth PWM signal; the driving device 50 includes:

[0057] The first driving unit 51 is coupled to the control unit 44 and the LC resonant series half-bridge structure circuit 10 respectively. It is configured to drive the two switching transistors in the LC resonant series half-bridge structure circuit 10 to turn on and off based on the third PWM signal, and to drive the other two switching transistors in the LC resonant series half-bridge structure circuit 10 to turn on and off based on the fourth PWM signal.

[0058] The second driving unit 52 is coupled to the control unit 44 and the full-bridge rectifier circuit 20 respectively, and is configured to drive the two switching transistors in the full-bridge rectifier circuit 20 to turn on and off based on the first PWM signal, and to drive the other two switching transistors in the full-bridge rectifier circuit 20 to turn on and off based on the second PWM signal.

[0059] like Figure 2 / Figure 3 As shown, when the energy conversion system 200 transmits power in the forward direction, that is, when transmitting power from the high-voltage side to the low-voltage side, the voltage at points a and b can be obtained by modulating the driving of the first switch Q1 to the fourth switch Q4. HV V HV / 2 The energy conversion device transmits power in reverse, that is, from the low-voltage side to the high-voltage side. The first switch Q1 and the fourth switch Q4 on the high-voltage side are driven simultaneously, and the second switch Q2 and the third switch Q3 are driven simultaneously. Points a and b only have voltage V. HV The circuit operates at two voltage levels: 0 and 1. A resonant network composed of resonant inductor Lr and resonant capacitor Crp keeps the circuit in a resonant state. Through isolation and voltage transformation by transformer TR, the target capacitor C1 on the high-voltage side can be the high-voltage bus capacitor on the high-voltage battery side. By modulating the driving of the fifth to eighth switches S1 to S4 on the low-voltage side and the first to fourth switches Q1 to Q4 on the high-voltage side, power can be transferred from the low-voltage side to the high-voltage side, charging the bus capacitor C1 to the set voltage, thus achieving the reverse pre-charge function.

[0060] It should be understood that the above description is merely one embodiment of the energy conversion system provided in this application and is not intended to limit the specific structure of the energy conversion system. For those skilled in the art, the energy conversion system can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made to the energy conversion system within the spirit and principles of this application should be considered as the energy conversion system proposed in this application. For example, the switching transistors on the high-voltage and low-voltage sides can be MOSFETs or other types of switching transistors such as insulated-gate transistors (IGBTs), and the capacitor CRP can be placed on the circuit connecting the transformer TR and point b, etc.

[0061] In some embodiments, the control unit 44 is specifically configured to: in response to a charging start signal, control the input current on the low-voltage side of the energy conversion device to maintain within a first threshold range of a first current value to charge the first energy storage device; when the voltage of the first energy storage device reaches a first voltage, adjust the input current to gradually increase it; when the voltage of the first energy storage device reaches a second voltage, control the input current to maintain within a second threshold range of a target current value; when the voltage of the first energy storage device reaches a third voltage, control the input current to decrease from the target current value to the second current value and maintain it within a third threshold range of the second current value until the voltage of the first energy storage device reaches the first target voltage value.

[0062] Specifically, the control unit 44 controls the power transmission from the low-voltage side to the high-voltage side of the energy conversion device. For example, it controls the on-board DC / DC converter module with bidirectional power transmission function to perform reverse pre-charging. The following describes the function of the control unit 44 provided in this embodiment in detail, taking the reverse pre-charging process of the on-board DC / DC converter module as an example:

[0063] The input current Iin on the low-voltage side of the energy conversion device and the voltage V of the first energy storage device (high-voltage bus capacitor) C1 connected to the high-voltage side are... HV As a control variable for the reverse pre-charge process, the input current Iin on the low-voltage side of the sampled energy conversion device is used. By controlling the magnitude of Iin, the output power during reverse pre-charge can be controlled. Figure 4 This is a comparative schematic diagram of the voltage control curve of the first energy storage device and the control curve of the low-voltage side input current of the energy conversion device during a reverse pre-charging process provided in an embodiment of this application. Figure 4 The black line in the middle represents the voltage V of the first energy storage device. HV The rising curve, Vset is the target voltage for pre-charging, starting from 0 and passing through V1, V2, V3, and finally reaching the first target voltage Vset; the gray curve is the reference curve (also known as the ideal curve) of Iin current, and the control unit 44 controls the actual Iin current to be consistent with the reference during the reverse pre-charging process.

[0064] See Figure 4 The charging process of the first energy storage device can be divided into four stages:

[0065] t0-t1: Stage 1, the low-voltage side input current Iin of the energy conversion device is controlled to be near a very small current value I1 (within the first threshold range of the first current value). During this process, the first energy storage device on the high-voltage side of the energy conversion device is simultaneously charged, and the voltage V of the first energy storage device is... HV It starts from 0 and slowly rises;

[0066] t1-t2: Phase 2, V HV The voltage has risen to V1 (first voltage), and the low-voltage side input current Iin of the control energy conversion device gradually increases. During this process, the first energy storage device continues to charge, and the voltage V... HV It continues to rise slowly from V1;

[0067] t2-t3: Stage 3, V HV The voltage has risen to V2 (second voltage), and the low-voltage side input current Iin of the energy conversion device has increased to near the set value Iref_set (target current value), and continues to operate stably near the set value Iref_set (within the second threshold range of the target current value);

[0068] t3-t4: Phase 4, V HV The voltage has risen to V3 (the third voltage). The current Iin is actively reduced to a smaller current value I2 (the second current value) near the third threshold range of the second current value to prevent the high-voltage output voltage V from the energy conversion device from increasing. HV Overshoot.

[0069] The first threshold range of the first current value refers to the range of current fluctuations caused by control accuracy, measurement errors, noise, etc., when the first current value is used as the control target of the input current Iin in stage 1. This fluctuation is a reasonable range that can be understood by those skilled in the art and does not affect the effect of the invention. For example, the first threshold range of the first current value is within ±1%, ±5%, or ±10% of the first current value. The second threshold range of the target current value and the third threshold range of the second current value are similar and will not be described again here.

[0070] Figure 4 In the diagram, Iin represents the input current on the low-voltage side, V HVIin represents the voltage of the first energy storage device, I1 represents the initial current at the start of charging, which is usually relatively small, and Iref_set is the set target current value, which is relatively large and can speed up the pre-charging speed. The voltage from I1 to Ire_set needs to go through a slow increase phase (t1 to t2). When the voltage of the first energy storage device approaches Vset, that is, after reaching V3, Iin is actively reduced to I2 (in order to prevent the charging current from being too large and causing the output voltage to overshoot). When the voltage of the first energy storage device reaches Vset, it means that the reverse pre-charging is over.

[0071] In some embodiments, the control unit 44 is further configured to: after the voltage of the first energy storage device reaches a first target voltage value, adjust the input current on the low-voltage side of the energy conversion device based on the real-time voltage of the first energy storage device and the second target voltage value, so that the voltage of the first energy storage device reaches the second target voltage value.

[0072] Specifically, the second target voltage value can be the same as or different from the first target voltage value. For example, when the second target voltage value is the same as the first target voltage value... Figure 4 As shown, when the voltage of the first energy storage device reaches Vset, it means that the reverse pre-charge is over. However, in order to keep the voltage of the first energy storage device at Vset, the input current Iin on the low-voltage side of the energy conversion device can be reduced to a very small current value.

[0073] In some embodiments, the input current on the low-voltage side is adjusted by controlling the switching on and off of the switching transistors in the full-bridge rectifier circuit on the low-voltage side of the energy conversion device; and / or the input current on the low-voltage side is adjusted by controlling the switching on and off of the switching transistors in the full-bridge rectifier circuit on the low-voltage side and the switching transistors in the series half-bridge circuit on the high-voltage side.

[0074] Specifically, controlling the on and off of the switching transistors includes controlling parameters such as the switching frequency, duty cycle, phase shift angle, dead time, on-time sequence, modulation method, and / or switching timing of each switching transistor. By controlling the on and off of the switching transistors on the low-voltage side of the energy conversion device, or by controlling the on and off of the switching transistors on both the low-voltage and high-voltage sides of the energy conversion device, the input current on the low-voltage side of the energy conversion device can be adjusted.

[0075] In some embodiments, the control unit 44 is specifically configured to: in response to the charging start signal, generate a first PWM signal and a second PWM signal having a first duty cycle and a first frequency, such that the input current on the low-voltage side of the energy conversion device is maintained within a first threshold range of a first current value to charge the first energy storage device, wherein the first PWM signal and the second PWM signal are used to drive the switching transistor in the full-bridge rectifier circuit.

[0076] For details, see Figure 4 In stage 1 (t0-t1), at time t0, the high-voltage side bus capacitor C1 is de-energized, similar to a short circuit. To reduce the impact at the moment of power-on, only a small current (e.g., 1A) is used for pre-charging at the beginning of the charging phase. During this time, the frequency of the drive signals (first PWM signal and second PWM signal) of the low-voltage side switching transistors S1 to S4 of the energy conversion device is set to a high frequency (first frequency, e.g., 300kHz), and the duty cycle is set to a small duty cycle (first duty cycle, e.g., 10%). This controls the current overshoot at the moment of power-on. The duration of this stage can be set (e.g., 10ms). During this stage, the high-voltage side switching transistors Q1 to Q4 of the energy conversion device are not driven. By time t1, the voltage of the high-voltage side bus capacitor C1 will be charged to the value V1. During this stage, the Iin current is very small, and there is no stress problem on the low-voltage side switching transistors of the energy conversion device.

[0077] In some embodiments, there is a 180-degree phase difference between the first PWM signal and the second PWM signal; wherein, the first PWM signal drives two switches of the full-bridge rectifier circuit to turn on and off; and the second PWM signal drives the other two switches of the full-bridge rectifier circuit to turn on and off.

[0078] For details, see Figure 2 In the full-bridge rectifier circuit on the low-voltage side of the energy conversion device, there are switching transistors S1, S2, S3, and S4; see [link to relevant documentation]. Figure 6 In stage 1, the first PWM signal drives the switching transistors S1 and S4 to turn on and off, and the second PWM signal drives the switching transistors S2 and S3 to turn on and off. Switches S1 and S4 alternately turn on and off with switches S2 and S3.

[0079] In some embodiments, the control unit 44 is further configured to: when the voltage of the first energy storage device reaches the first voltage, control the duty cycle of the first PWM signal and the second PWM signal to gradually increase from the first duty cycle to the second duty cycle, and control the frequency of the first PWM signal and the second PWM signal to gradually decrease from the first frequency to the second frequency.

[0080] It should be understood that the first and second PWM signals used in stage 2 are inherited from stage 1. In other words, the first and second PWM signals used in the initial stage of stage 2 are the same as those used in the final stage of stage 1.

[0081] See Figure 4 In stage 2 (t1-t2), after the high-voltage side bus capacitor C1 has a certain voltage V1 (first voltage, e.g., 5% Vset), it is necessary to gradually increase the input current Iin on the low-voltage side. At this time, the duty cycle of the drive signals (i.e., the first PWM signal and the second PWM signal) of the low-voltage side switching transistors S1 to S4 of the energy conversion device can be gradually increased to the second duty cycle (e.g., 50%). Then, the frequency of the first PWM signal and the second PWM signal is adjusted, gradually decreasing from the first frequency to the second frequency f1, in order to increase the output voltage and power of the high-voltage side of the energy conversion device. At this time, the high-voltage side switching transistors Q1 to Q4 of the energy conversion device are still not driven. The adjusted first PWM signal and second PWM signal in stage 2 are shown in [reference]. Figure 5 The second frequency f1 can be specified, and is usually f1 > fr (fr is the resonant frequency of the resonant network composed of the inductor Lr and capacitor Crp of the energy conversion device, see [reference]). Figure 2 For example, f1 = 1.2fr. At time t2, the voltage V... HV It will be pushed up to the V2 value. During this stage, Iin is controlled to increase slowly, and there are no stress problems with the low-voltage side switching transistors of the energy conversion device. Figure 6 This is a timing diagram of the electrical parameters of the high-voltage and low-voltage sides of the energy conversion device during the switching cycle of stage 2, where I Lr Let I_ represent the current in inductor Lr, Vab represent the voltage between points a and b, and I_ S1 / S4 I_ represents the current of switching transistors S1 / S4. S2 / S3 I_ represents the current in switching transistors S2 / S3. Q1 / Q4 I_ represents the current of switching transistors Q1 / Q4. Q2 / Q3 This indicates the current of switching transistors Q2 / Q3. Figure 7 This is a schematic diagram of the switching process during the second phase of the switching cycle. The dashed lines represent the closed switches, and the solid lines represent the open switches.

[0082] In some embodiments, the control unit 44 is specifically configured to: generate a third PWM signal and a fourth PWM signal when the voltage of the first energy storage device reaches a second voltage, and control the third PWM signal and the fourth PWM signal to drive the switching transistor in the LC resonant series half-bridge circuit so that the input current is maintained within the second threshold range of the target current value.

[0083] It should be understood that the first and second PWM signals used in stage 3 are inherited from stage 2. In other words, the first and second PWM signals used in the initial stage of stage 3 are the same as those used in the final stage of stage 2.

[0084] See Figure 4 In stage 3 (t2-t3), after the voltage of the first energy storage device is detected to have reached the second voltage V2, in order to further increase the high-voltage side output voltage of the energy conversion device, see [reference needed]. Figure 6 At this point, the high-voltage side switching transistors Q1 to Q4 are driven.

[0085] Specifically, the gain can be increased by adjusting the phase angle difference, or phase shift angle DΦ, between the high-voltage side switch drive signal and the low-voltage side switch drive signal of the energy conversion device, thereby increasing the high-voltage side output voltage of the energy conversion device. For example, the phase angle difference between the first PWM signal and the third PWM signal, and the phase angle difference between the second PWM signal and the fourth PWM signal can be adjusted synchronously.

[0086] The formula for calculating the phase shift angle DΦ is ​​as follows:

[0087]

[0088] In the formula, M is the bias constant and K is the modulation coefficient.

[0089] As the high-voltage side voltage of the energy conversion device increases, the required phase shift angle DΦ also needs to increase. Since the low-voltage side of the energy conversion device maintains a constant target current, the low-voltage side voltage is also constant. Therefore, the system maintains a constant power to charge the high-voltage side capacitor. As the high-voltage side voltage of the energy conversion device increases, the high-voltage side charging current decreases, so the system's switching frequency fs also needs to be gradually increased.

[0090] In some embodiments, the third PWM signal and the fourth PWM signal have the same duty cycle and frequency, and there is a 180-degree phase difference between the third PWM signal and the fourth PWM signal; the third PWM signal drives the two switching transistors in the LC series half-bridge structure circuit to turn on and off; the fourth PWM signal drives the other two switching transistors in the LC series half-bridge structure circuit to turn on and off.

[0091] For details, see Figure 3 The LC-type series half-bridge circuit includes switching transistors Q1 to Q4; see [link / reference] Figure 6In stage 3, the third PWM signal drives the switching transistors Q1 and Q4 to turn on and off, and the fourth PWM signal drives the switching transistors Q2 and Q3 to turn on and off. Switches Q1 and Q4 alternately turn on and off with switches Q2 and Q3.

[0092] In some embodiments, during stage 3, the duty cycle and frequency of the third PWM signal and the fourth PWM signal are consistent with the duty cycle and frequency of the first PWM signal / second PWM signal. Specifically, since the duty cycle and frequency of the first PWM signal and the second PWM signal are consistent, the duty cycles and frequencies of the first to fourth PWM signals are all consistent.

[0093] In some embodiments, in stage 3, there is a phase angle difference between the third PWM signal and the sub-PWM signal, and the phase angle difference between the fourth PWM signal and the second PWM signal, so that the switching transistor in the full-bridge rectifier circuit can achieve a zero-current turn-off state when turned off.

[0094] For details, see Figure 4 In stage 3 (t2-t3), since Iin has been modulated to its maximum value during the charging process, stress problems are typically generated in the low-voltage side switching transistors S1 to S4 of the energy conversion device: such as Figure 11 As shown, since lead inductance is common in circuits, when a large current flows through the MOSFET and it is turned off, the energy on the lead inductance will be relatively high. This energy will continue to charge the junction capacitance (Cs1) of the MOSFET after it is turned off, thereby increasing the stress Vds of the MOSFET.

[0095] Therefore, at this stage, see Figure 8 By adjusting the phase shift angle DΦ between the high-voltage and low-voltage side switching transistor drive signals of the energy conversion device, the current flowing through switching transistors S1 / S4 when they are turned off is negative (at time t23), and the current flowing through switching transistors S2 / S3 when they are turned off is negative (at time t26). Moreover, the negative current is small, achieving the ZCS turn-off state (approximately zero current turn-off state). Compared with the voltage stress when the switching transistors are turned off when the current is positive, the voltage stress when the switching transistors are turned off is significantly reduced. Figure 9 This is a timing diagram of the electrical parameters of the high-voltage and low-voltage sides of the energy conversion device during the switching cycle of stage 3. Figure 10 This is a schematic diagram of the switching of the energy conversion device during the switching cycle of stage 3. In this diagram, the switch tubes represented by dashed lines are closed switches, and the switch tubes represented by solid lines are open switches.

[0096] In some embodiments, the control unit 44 is specifically configured to: generate a third PWM signal and a fourth PWM signal when the voltage of the first energy storage device reaches a second voltage, adjust the phase shift angle between the third PWM signal and the first PWM signal and the phase shift angle between the fourth PWM signal and the second PWM signal, so that the input current is maintained within a second threshold range of the target current value, and the third PWM signal and the fourth PWM signal are used to drive the switching transistors in the LC resonant series half-bridge structure circuit.

[0097] For details, see Figure 6 In order to keep the capacitor on the high-voltage side of the energy conversion device charging at a constant power in stage 3, and as the voltage of the first energy storage device increases, the charging current on the high-voltage side of the energy conversion device needs to decrease. Therefore, the phase angle difference between the control signals on the high-voltage side and the low-voltage side of the energy conversion device (the phase shift angle between the third PWM signal and the first PWM signal and the phase shift angle between the fourth PWM signal and the second PWM signal) needs to increase, and the switching frequency of the system needs to increase.

[0098] In some embodiments, the control unit 44 is specifically configured to: when the voltage of the first energy storage device reaches a third voltage, control the first PWM signal and the second PWM signal to drive the switching transistor in the full-bridge rectifier circuit, and control the third PWM signal and the fourth PWM signal to drive the switching transistor in the LC resonant series half-bridge structure circuit on the high-voltage side, so that the input current decreases from the target current value to the second current value and is maintained within the third threshold range of the second current value.

[0099] It should be understood that the first to fourth PWM signals used in stage 4 are inherited from stage 3. In other words, the first to fourth PWM signals used in the beginning stage of stage 4 are the same as the first to fourth PWM signals used in the ending stage of stage 3.

[0100] In some embodiments, in stage 4, the control unit 44 is specifically configured to: when the voltage of the first energy storage device reaches the third voltage, control the frequency of the first PWM signal and the second PWM signal to gradually increase; control the frequency of the third PWM signal and the fourth PWM signal to gradually increase, the phase angle difference between the third PWM signal and the first PWM signal to gradually increase, and the phase angle difference between the fourth PWM signal and the second PWM signal to gradually increase.

[0101] For details, see Figure 4 Stage 4 (t3-t4), at this time the voltage V HVThe voltage is approaching the pre-charge target voltage Vset. To prevent output voltage overshoot, the low-voltage side input current Iin of the energy conversion device is actively reduced to a smaller value I2 at a voltage V3 that still maintains a certain margin from the pre-charge target voltage Vset. This reduces the high-voltage side charging current of the energy conversion device, effectively preventing voltage overshoot. During this stage, the Iin current decreases significantly, and the low-voltage side switching transistor of the energy conversion device experiences no stress issues. Typically, voltage V3 is slightly lower than the pre-charge target voltage Vset (e.g., 50V). For details, see [link to documentation]. Figure 6 In stage 4, the gain can be increased by further adjusting the phase angle difference (i.e., phase shift angle DΦ) between the high-voltage side switch drive signal and the low-voltage side switch drive signal of the energy conversion device, thereby increasing the high-voltage side output voltage of the energy conversion device. For example, the phase angle difference between the first and third PWM signals, and the phase angle difference between the second and fourth PWM signals can be adjusted synchronously. Simultaneously, the system switching frequency fs also needs to be gradually increased to reduce the low-voltage side input current Iin and charging power of the energy conversion device.

[0102] See Figure 4 In some embodiments, after stage 4 (after t4), that is, after the voltage V of the first energy storage device... HV After reaching the first target voltage value Vset, in order to maintain the voltage of the first energy storage device at Vset, the input current Iin on the low-voltage side of the energy conversion device can be reduced to a very small current value. The control logic at this stage can be as follows: See Figure 2 When the voltage V HVAfter reaching the first target voltage value Vset (after t4), the voltage control loop takes over. The high-voltage side HV voltage sampling signal Vsen_HV (a signal reduced from the current voltage of the first energy storage device, which can be regarded as the current voltage of the first energy storage device) and the voltage reference value Vref_HV (a signal reduced from the first target voltage value Vset, which can be regarded as the first target voltage value Vset) enter the voltage control loop to obtain the output signal VAO. Iref_set is the set current value. The smaller of the two signals VAO output by the voltage control loop and the set current value Iref_set is taken. The module (smaller output) receives an output signal Iref (smaller value), which serves as the reference for the current control loop. This signal, along with the low-voltage side input current sampling signal Isen_LV, enters the current control loop, resulting in an output signal CAO. The CAO signal and the high-voltage side sampling signal Vsen_HV serve as the input signals for the PWM control module. The control unit determines the final switching frequency fs and the phase shift angle DΦ between the high-voltage and low-voltage side drive signals of the energy conversion device to reduce the low-voltage side input current Iin of the energy conversion device, thereby maintaining the voltage of the first energy storage device at the first target voltage value Vset. For example, the control unit 44 can lower the phase shift angle DΦ and / or increase the switching frequency fs of the switching transistor.

[0103] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0104] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An energy conversion device, characterized in that, include: transformer; An LC resonant series half-bridge circuit is coupled to the high-voltage winding of the transformer. A full-bridge rectifier circuit is coupled to the low-voltage winding of the transformer.

2. The energy conversion device according to claim 1, characterized in that, The LC resonant series half-bridge structure circuit includes an LC resonant circuit and a series half-bridge structure circuit; wherein... The first end of the LC resonant circuit is coupled to the first end of the series half-bridge structure circuit, and the second end of the LC resonant circuit is coupled to the high-voltage side winding. The second end of the series half-bridge circuit is coupled to the first energy storage device.

3. The energy conversion device according to claim 2, characterized in that, The series half-bridge circuit includes: The switch bridge arm includes a first switch transistor, a second switch transistor, a third switch transistor, and a fourth switch transistor connected in series. The capacitor bridge arm includes a first capacitor and a second capacitor connected in series. The two ends of the capacitor bridge arm are respectively connected to the two ends of the switch bridge arm, and the midpoint between the first capacitor and the second capacitor is coupled to the midpoint between the second switch and the third switch. The two ends of the capacitor bridge arm are also coupled in parallel to the two ends of the first energy storage device.

4. The energy conversion device according to claim 3, characterized in that, The LC resonant circuit includes a resonant inductor and a resonant capacitor; wherein... The first end of the resonant capacitor is coupled to the midpoint between the first switching transistor and the second switching transistor, the other end of the resonant capacitor is coupled to the first end of the resonant inductor, and the second end of the resonant capacitor is coupled to the first end of the high-voltage side winding. The midpoint between the third and fourth switching transistors is coupled to the second end of the high-voltage side winding.

5. The energy conversion device according to claim 2, characterized in that, The input terminal of the full-bridge rectifier circuit is coupled to the second energy storage device, and the output terminal of the full-bridge rectifier circuit is coupled to the low-voltage winding of the transformer.

6. The energy conversion device according to claim 5, characterized in that, It also includes a filter capacitor, which is connected in parallel to the input terminal of the full-bridge rectifier circuit.

7. The energy conversion device according to claim 5, characterized in that, The first energy storage device includes a capacitor, and the second energy storage device includes a battery.

8. An energy conversion system, characterized in that, It includes a first energy storage device, a second energy storage device, and an energy conversion device as described in any one of claims 1 to 7, wherein the first energy storage device, the energy conversion device, and the second energy storage device are connected in sequence.

9. The energy conversion system according to claim 8, characterized in that, Also includes: The acquisition device, coupled to the first energy storage device and the full-bridge rectifier circuit, is configured to acquire the input current of the full-bridge rectifier circuit and the voltage of the first energy storage device in real time, and generate a sampled current value and a sampled voltage value based on the input current of the full-bridge rectifier circuit and the voltage of the first energy storage device. A control device, coupled to the acquisition device, the LC resonant series half-bridge circuit and the full-bridge rectifier circuit, is configured to generate drive signals for the switching transistors in the LC resonant series half-bridge circuit and the full-bridge rectifier circuit based on the sampled current value and the sampled voltage value. The driving device, coupled to the control device, the LC resonant series half-bridge circuit and the full-bridge rectifier circuit, is configured to drive the switching transistors in the LC resonant series half-bridge circuit and the full-bridge rectifier circuit to turn on and off based on the driving signal, so that the second energy storage device charges the first energy storage device with a set current.

10. The energy conversion system according to claim 9, characterized in that, The control device includes: A voltage control loop module, coupled to the acquisition device, is configured to generate a first output signal based on the sampled voltage value and the voltage reference value after the voltage of the first energy storage device reaches the target voltage value. A small unit is taken and coupled to the voltage control loop module, and is configured to compare the first output signal and the set current value to obtain the smaller value between the first output signal and the set current value. A current control loop module, coupled to the smaller value and the acquisition device, is configured to generate a second output signal based on the smaller value and the sampled current value; A control unit, coupled to the acquisition device, the current control loop module, the LC resonant series half-bridge circuit, the full-bridge rectifier circuit, and the driving device, is configured to: before the voltage of the first energy storage device reaches the target voltage value, generate driving signals for the switching transistors in the LC resonant series half-bridge circuit and the full-bridge rectifier circuit based on the sampled voltage value, so that the driving device drives the switching transistors to turn on and off based on the driving signals, thereby enabling the second energy storage device to charge the first energy storage device with the set current; after the voltage of the first energy storage device reaches the target voltage value, generate driving signals for the switching transistors based on the sampled voltage value and the second output signal, so that the driving device drives the switching transistors to turn on and off based on the driving signals, thereby maintaining the voltage of the first energy storage device at the target voltage value.

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