Energy conversion circuit, control method based on energy conversion circuit and vehicle

Abstract

The embodiment of the invention provides an energy conversion circuit, a control method based on the energy conversion circuit and a vehicle. The energy conversion circuit comprises a primary side bridge arm module, a resonance module, a secondary side bridge arm module and a control module. The primary side bridge arm module comprises a first bridge arm and a second bridge arm, and the secondary side bridge arm module comprises a first secondary side switch and a second secondary side switch; the control module controls a driving signal of the first bridge arm, a driving signal of the second bridge arm, a driving signal of the first secondary side switch and a driving signal of the second secondary side switch, so that the voltage between the first direct current positive electrode port and the first direct current negative electrode port is increased to a preset voltage; wherein in the process that the voltage between the first direct current positive electrode port and the first direct current negative electrode port is increased, the zero current of the switch in the secondary side bridge arm module is switched off. According to the embodiment of the invention, the voltage stress of the switch in the energy conversion circuit can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to an energy conversion circuit, a control method based on the energy conversion circuit, and a vehicle. Background Art

[0002] In electric vehicles, a switch and a filter capacitor of a certain capacity are usually placed between the high-voltage battery and the DC bus of the electric drive. When the vehicle starts, the switch is closed, and the high-voltage battery supplies power to the DC bus. Since the voltage of the capacitor is zero in the initial state, if the high-voltage battery directly charges the bus capacitor through the DC bus, surge current will be generated, posing a safety risk. In order to suppress the impact of surge current on the circuit, a pre-charging circuit is usually used to pre-charge the bus capacitor before the vehicle starts.

[0003] The traditional pre-charging method is to charge the bus capacitor by adding a pre-charging resistor. In order to reduce system costs and eliminate pre-charging resistors, a bidirectional direct current / direct current (DC / DC) converter is currently used to convert the power of the low-voltage battery into high-voltage electricity to charge the bus capacitor in advance. However, during the reverse pre-charging process, since the control method of the bidirectional DC / DC converter is usually based on soft switching control, the switch tube on the low-voltage side is hard-off, the shutdown current is large, and an excessively high resonant voltage is generated at both ends of the switch tube, which brings a high voltage stress to the switch tube, thereby causing damage to the switch tube. Summary of the invention

[0004] The embodiments of the present application provide an energy conversion circuit, a control method based on the energy conversion circuit, and a vehicle, which can reduce the voltage stress of switches in the energy conversion circuit.

[0005] A first aspect of an embodiment of the present application provides an energy conversion circuit, including a primary bridge arm module, a resonance module, a secondary bridge arm module and a control module; the primary bridge arm module includes: a first bridge arm and a second bridge arm, and the secondary bridge arm module includes a first secondary switch and a second secondary switch; The midpoint of the second bridge arm is connected to the first end of the resonance module, and the midpoint of the first bridge arm is connected to the second end of the resonance module; the third end of the resonance module is connected to the first end of the second secondary switch, and the fourth end of the resonance module is connected to the first end of the first secondary switch; the first end of the first bridge arm is connected to the first end of the second bridge arm and the first DC positive port, the second end of the first bridge arm is connected to the second end of the second bridge arm and the first DC negative port, the fifth end of the resonance module is connected to the second DC positive port, and the second end of the first secondary switch is connected to the second end of the second secondary switch and the second DC negative port; The control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch to increase the voltage between the first DC positive port and the first DC negative port to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive port and the first DC negative port, the switch in the secondary bridge arm module is turned off with zero current.

[0006] Optionally, the resonance module includes: a resonant inductor, a resonant capacitor and a transformer; the transformer includes a primary winding, a first secondary winding and a second secondary winding; The resonant inductor and the resonant capacitor are respectively connected in series with the primary winding, and the first secondary winding is connected in series with the second secondary winding; the resonant inductor, the resonant capacitor and the primary winding are connected in series between the midpoint of the first bridge arm and the midpoint of the second bridge arm, the first end of the first secondary winding is connected to the second end of the second secondary winding and the second DC positive port, the second end of the first secondary winding is connected to the first end of the first secondary switch, and the first end of the second secondary winding is connected to the first end of the second secondary switch.

[0007] Optionally, the energy conversion circuit also includes a first filter capacitor and a second filter capacitor, wherein two ends of the first filter capacitor are respectively connected between the first DC positive port and the first DC negative port; and two ends of the second filter capacitor are respectively connected between the second DC positive port and the second DC negative port.

[0008] Optionally, the control module controls a drive signal of the first bridge arm, a drive signal of the second bridge arm, a drive signal of the first secondary switch, and a drive signal of the second secondary switch, so that a voltage between the first DC positive port and the first DC negative port increases to a preset voltage, and in a process in which the voltage between the first DC positive port and the first DC negative port increases, a switch in the secondary bridge arm module is turned off with zero current, including: The control module determines the gain of the energy conversion circuit according to a first sampling voltage, a second sampling voltage and the transformer turns ratio; the first sampling voltage is a sampling voltage between the first DC positive port and the first DC negative port, and the second sampling voltage is a sampling voltage between the second DC positive port and the second DC negative port; When the gain of the energy conversion circuit is less than 1, the control module controls the drive signal of the first bridge arm, the drive signal of the second bridge arm, the drive signal of the first secondary switch, and the drive signal of the second secondary switch, so that the switch in the primary bridge arm module operates in a synchronous rectification mode, so that the switch in the secondary bridge arm module is turned off with zero current; When the gain of the energy conversion circuit is greater than or equal to 1, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is a first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is a second phase shift angle, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current, the first phase shift angle is equal to the second phase shift angle, or the first phase shift angle is not equal to the second phase shift angle.

[0009] Optionally, the control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the switch in the primary bridge arm module operates in a synchronous rectification mode, so that the switch in the secondary bridge arm module is turned off with zero current, including: The control module performs loop calculation according to the first sampling voltage to obtain a voltage loop calculation result, and determines the signal frequency according to the voltage loop calculation result; The control module determines that the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the driving signal of the first secondary switch, and the frequency of the driving signal of the second secondary switch are all the signal frequencies, so that the switches in the primary bridge arm module operate in a synchronous rectification mode, so that the switches in the secondary bridge arm module are turned off with zero current.

[0010] Optionally, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is a first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is a second phase shift angle, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current, including: The control module determines the primary-secondary side phase shift angle according to the sampled current and the reference current; When the first phase shift angle is equal to the second phase shift angle, the control module determines that the original secondary side phase shift angle is the first phase shift angle; When the first phase shift angle is not equal to the second phase shift angle, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is the first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is the second phase shift angle according to the primary-secondary side phase shift angle and the gain of the energy conversion circuit, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current; the sampling current is the sampling current between the second end of the first secondary switch to the second DC negative terminal.

[0011] Optionally, the control module includes: a current control loop, a voltage control loop, a voltage-controlled oscillator, a gain judgment and a phase shift / frequency conversion modulation module; The current control loop is used to perform loop calculation on the result of subtracting the sampled current from the reference current, and output the original-secondary side shift phase angle; The voltage control loop is used to perform loop calculation on the result of subtracting the first sampling voltage from the reference voltage, and output the voltage loop calculation result; The voltage controlled oscillator is used to calculate the signal frequency according to the voltage loop calculation result; The gain judgment and phase shift / frequency conversion modulation module is used to calculate the gain of the energy conversion circuit according to the first sampling voltage and the second sampling voltage; The gain judgment and phase shift / frequency conversion modulation module is further used to determine that the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the driving signal of the first secondary switch, and the frequency of the driving signal of the second secondary switch are all the signal frequency when the gain of the energy conversion circuit is less than 1; The gain judgment and phase shift / frequency conversion modulation module is also used to determine that the first phase shift angle and the second phase shift angle are both the original-secondary side phase shift angles when the gain of the energy conversion circuit is greater than or equal to 1, or to calculate the first phase shift angle and the second phase shift angle based on the gain of the energy conversion circuit and the original-secondary side phase shift angles.

[0012] Optionally, when the gain of the energy conversion circuit is greater than or equal to 1, and the first phase shift angle and the second phase shift angle are not equal, the first phase shift angle and the second phase shift angle are determined according to the following formula: D Φ1 =D α -(1-D y1 ); D Φ2 =D α ; D α =(1-D y1 +2DΦ ) / 2; If D Φ <D ΦB , then D y1 = k × (2D Φ +1) / (2-k); If D Φ ≥D ΦB , then D y1 =[2×D Φ ×(1-k)+2k-1] / k; D ΦB = (1-k) / 2, k = 1 / Ge; Ge = V HV_FB / (n×V LV_FB ); Wherein, Ge is the gain of the energy conversion circuit, D Φ The phase shift angle of the original secondary side calculated by the loop, D Φ1 is the first phase shift angle, D Φ2 is the second phase shift angle, n is the turns ratio of the transformer, V HV_FB is the first sampling voltage, V LV_FB is the second sampling voltage.

[0013] Optionally, the signal frequency is positively correlated with the gain of the energy conversion circuit.

[0014] Optionally, the energy conversion circuit operates in a capacitive region.

[0015] A second aspect of the embodiment of the present application provides a control method based on an energy conversion circuit, the control method is applied to the energy conversion circuit of the first aspect of the embodiment of the present application, the control method comprising: The control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the voltage between the first DC positive terminal and the first DC negative terminal increases to a preset voltage; Wherein, during the process of the voltage between the first DC positive port and the first DC negative port increasing, the switch in the secondary bridge arm module is turned off with zero current.

[0016] A third aspect of an embodiment of the present application provides a vehicle, comprising the energy conversion circuit and bus capacitor of the first aspect of the embodiment of the present application, wherein the two ends of the bus capacitor are respectively connected to a first DC positive electrode interface of the energy conversion circuit and a first DC negative electrode interface of the energy conversion circuit, and the energy conversion circuit is used to charge the bus capacitor.

[0017] In the energy conversion circuit of the embodiment of the present application, the control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the voltage between the first DC positive port and the first DC negative port increases to a preset voltage. During the process of increasing the voltage between the first DC positive port and the first DC negative port, the switch in the secondary bridge arm module is turned off with zero current, which can reduce the voltage stress of the switch in the secondary bridge arm module, thereby reducing the voltage stress of the switch in the energy conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 is a structural schematic diagram of a pre-charging circuit in a vehicle provided in an embodiment of the present application; Figure 2 is a structural schematic diagram of another pre-charging circuit in a vehicle provided in an embodiment of the present application; Figure 3 is a schematic diagram of the structure of an energy conversion circuit provided in an embodiment of the present application; Figure 4 is a schematic diagram of a driving signal and a conduction current of a secondary side switch provided in an embodiment of the present application; Figure 5 Schematic diagram of voltage change between the first DC positive terminal DC1+ and the first DC negative terminal DC1- during pre-charging, and the first secondary switch SR 1 The driving signal Vgs_SR1 and the second switch S 2 Schematic diagram of the change of the driving signal Vgs_S2; Figure 6 is a schematic diagram of a specific control structure of an energy conversion circuit provided in an embodiment of the present application; Figure 7 It is a waveform diagram of a driving signal, a resonant current, and a current of a high- and low-voltage side switch of each switch when Ge<1 provided in an embodiment of the present application; Figure 8 It is a waveform diagram of a driving signal, a resonant current, and a current of a high- and low-voltage side switch of each switch when Ge≥1 provided in an embodiment of the present application; Fig. 9It is another waveform diagram of the driving signal, resonant current, and current of the high and low voltage side switches of each switch when Ge≥1 provided in an embodiment of the present application; Fig.10 It is a flow chart of a control method based on an energy conversion circuit provided in an embodiment of the present application; Fig.11 It is a structural schematic diagram of a vehicle provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0021] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, products or devices.

[0022] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0023] See also Figure 1 , Figure 1 Schematic diagram of a pre-charging circuit in a vehicle provided in an embodiment of the present application. Figure 1 As shown in the figure, when the vehicle starts, since the voltage of the bus capacitor Cbus is zero, if K1 and K2 are directly closed to allow the high-voltage battery to charge the bus capacitor Cbus, a surge current will be generated, bringing safety risks. In order to suppress the impact of the surge current on the circuit, a pre-charging circuit (such as Figure 1 The switches K2, K3 and the pre-charge resistor R shown in the figure charge the bus capacitor, wherein the pre-charge resistor R plays a current limiting role. The bus capacitor Cbus can also be called a pre-charge capacitor. Figure 1It also includes an inverter and a motor M. The inverter can convert the voltage of the high-voltage battery into an AC voltage to power the motor M. Figure 1 The working principle is: first close K2 and K3, disconnect K1, and charge the bus capacitor Cbus through the pre-charging circuit. When the voltage of the bus capacitor Cbus reaches or approaches the voltage of the high-voltage battery, close K1 and K2, disconnect K3, start the inverter, and drive the motor M. Figure 1 The high-voltage battery can be the power battery of the vehicle.

[0024] In order to reduce system costs, a bidirectional DC / DC converter is currently used to convert the low-voltage battery power into high-voltage power to charge the bus capacitor Cbus in advance. Figure 2 . Figure 2 Schematic diagram of the structure of another pre-charging circuit in a vehicle provided in an embodiment of the present application. Figure 2 As shown, the bidirectional DC / DC converter can convert the electric energy of the low-voltage battery into high-voltage electricity to charge the bus capacitor Cbus in advance. Figure 2 The high-voltage battery may be the power battery of the vehicle. The voltage of the high-voltage battery is generally above 100V. The high-voltage battery can be used to power the motor on the vehicle. The low-voltage battery may be a battery on the vehicle that powers the low-voltage load, and the low-voltage battery may be the storage battery of the vehicle. The voltage of the low-voltage battery is generally around 12V or 24V or around 48V. The low-voltage load may be an electronic control unit (ECU) on the vehicle, and the ECU may include at least one of a car computer, a music player, a wiper, a steering module, and a brake module.

[0025] The bidirectional DC / DC converter can work in low voltage to high voltage mode or high voltage to low voltage mode. When the bidirectional DC / DC converter works in low voltage to high voltage mode, the bidirectional DC / DC converter can convert the electric energy of the low voltage battery into high voltage electricity to charge the bus capacitor Cbus. When the bidirectional DC / DC converter works in high voltage to low voltage mode, the bidirectional DC / DC converter can convert the electric energy of the high voltage battery into low voltage electricity to charge the low voltage battery.

[0026] See also Figure 3 , Figure 3 Schematic diagram of an energy conversion circuit provided in an embodiment of the present application. Figure 3 As shown, the energy conversion circuit may include a primary bridge arm module 10, a resonance module 20, a secondary bridge arm module 30 and a control module 40; the primary bridge arm module 10 includes: a first bridge arm and a second bridge arm, the secondary bridge arm module 30 includes a first secondary switch SR 1 and the second secondary switch SR2 ; The midpoint of the second bridge arm is connected to the first end of the resonance module 20, and the midpoint of the first bridge arm is connected to the second end of the resonance module 20; the third end of the resonance module 20 is connected to the second secondary switch SR 2 The first end of the resonant module 20 is connected to the first secondary switch SR 1 The first end of the first bridge arm is connected to the first end of the second bridge arm and the first DC positive port DC1+, the second end of the first bridge arm is connected to the second end of the second bridge arm and the first DC negative port DC1-, the fifth end of the resonant module 20 is connected to the second DC positive port DC2+, the first secondary switch SR 1 The second end of the second secondary switch SR 2 The second end and the second DC negative terminal DC2-; The control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the first secondary switch SR 1 The driving signal of the second secondary switch SR 2 A driving signal is sent to increase the voltage between the first DC positive port DC1+ and the first DC negative port DC1- to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive port DC1+ and the first DC negative port DC1-, the switch in the secondary bridge arm module 30 is turned off with zero current.

[0027] like Figure 3 As shown, the first bridge arm includes a first switch S 1 and the second switch S 2 , the first switch S 1 The first end of the first switch S 1 The second end of the second switch S 2 and the midpoint of the first bridge arm, the second switch S 2 The second end of the first bridge arm is connected to the second end of the first bridge arm. The driving signal of the first bridge arm includes a first driving signal and a second driving signal. The control module 40 can control the driving module to drive the first switch S 1 The third end of the first switch S sends a first drive signal, and the first drive signal is used to control the first switch S 1 The control module 40 can control the driving module to the second switch S 2 The third end of the second switch S sends a second drive signal, and the second drive signal is used to control the second switch S 2The frequency of the first drive signal is the same as the frequency of the second drive signal, and the first drive signal and the second drive signal are complementary signals, that is, within one cycle of the first drive signal, the first switch S 1 and the second switch S 2 One is turned on and the other is turned off. Exemplarily, the duty cycle of the first drive signal and the second drive signal are both 50% (ignoring dead time).

[0028] The second bridge arm includes a third switch S 3 and the fourth switch S 4 , the third switch S 3 The first end of the third switch S 3 The second end of the fourth switch S 4 and the middle point of the bridge arm of the second bridge arm, the fourth switch S 4 The second end of the second bridge arm is connected to the second end of the second bridge arm. The driving signal of the second bridge arm includes a third driving signal and a fourth driving signal. The control module 40 can control the driving module to drive the third switch S 3 The third end of the third switch S sends a third drive signal, and the third drive signal is used to control the third switch S 3 The control module 40 can control the drive module to the fourth switch S 4 The third end of the fourth switch S sends a fourth drive signal, and the fourth drive signal is used to control the fourth switch S 4 The frequency of the third drive signal is the same as the frequency of the fourth drive signal, and the third drive signal and the fourth drive signal are complementary signals, that is, within one cycle of the third drive signal, the third switch S 3 and the fourth switch S 4 One is turned on and the other is turned off. Exemplarily, the duty cycle of the third driving signal and the fourth driving signal are both 50% (ignoring the dead time).

[0029] The control module 40 can control the driving module to switch the first secondary side switch SR 1 The third terminal sends the first secondary switch SR 1 The driving signal of the first secondary switch SR 1 The driving signal is used to control the first secondary switch SR 1 The control module 40 can control the drive module to switch the second secondary side switch SR 2 The third terminal sends the second secondary switch SR 2 The driving signal of the second secondary switch SR 2 The driving signal is used to control the second secondary switch SR 2 The first secondary switch SR1 The frequency of the driving signal and the second secondary switch SR 2 The frequency of the driving signal is the same as that of the first secondary switch SR 1 The driving signal and the second secondary switch SR 2 The driving signal is a complementary signal, that is, the first secondary switch SR 1 In one cycle of the driving signal, the first secondary switch SR 1 and the second secondary switch SR 2 One is turned on and the other is turned off. 1 The driving signal and the second secondary switch SR 2 The duty cycle of the driving signal is 50% (ignoring the dead time).

[0030] Among them, the above-mentioned driving module can be Figure 6 The driver module in.

[0031] like Figure 3 As shown, the switches in the primary bridge arm module 10 include: a first switch S 1 , the second switch S 2 , the third switch S 3 and the fourth switch S 4 The switches in the secondary bridge arm module 30 include a first secondary switch SR 1 and the second secondary switch SR 2 Each switch may include a junction capacitor and a body diode. For example, the first secondary switch SR 1 The junction capacitance C 1 and body diode D 1 , the second secondary switch SR 2 The junction capacitance C 2 and body diode D 2 .

[0032] Among them, the first switch S 1 , the second switch S 2 , the third switch S 3 , the fourth switch S 4 、First secondary switch SR 1 and the second secondary switch SR 2 Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or Insulate-Gate Bipolar Transistor (IGBT) can be used. MOSFET can also be called MOS tube or MOS transistor. Figure 3The switches in the embodiment are all N-type MOS transistors as examples, which can be referred to as NMOS transistors for short. MOSFETs can be silicon carbide (SiC) MOSFETs or gallium nitride (GaN) MOSFETs. Silicon carbide MOSFETs are MOSFETs made of silicon carbide materials, and gallium nitride MOSFETs are MOSFETs made of gallium nitride materials. When the switch is a MOS transistor, the third terminal of the switch is the gate of the switch. For example, in the first switch S 1 When it is an NMOS tube, the first switch S 1 The third end of the first switch S 1 of the gate.

[0033] The voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1- is V HV , the voltage between the second DC positive terminal DC2+ and the second DC negative terminal DC2- is V LV The energy conversion circuit can convert the voltage V between the second DC positive terminal DC2+ and the second DC negative terminal DC2- LV Converted into a voltage V between the first DC positive terminal DC1+ and the first DC negative terminal DC1- HV and charges the bus capacitor Cbus.

[0034] Figure 3 The energy conversion circuit can be Figure 2 The bidirectional DC / DC converter shown in FIG. The first DC positive terminal DC1+ and the first DC negative terminal DC1- can be connected to Figure 2 The bus capacitance Cbus is across both ends. V LV is the voltage across the low voltage battery, V HV It can be the voltage across the bus capacitor Cbus.

[0035] The preset voltage may be less than or equal to the rated voltage of the bus capacitor Cbus.

[0036] The traditional control strategy of the energy conversion circuit is to control the output voltage gain and current by adjusting the switching frequency. The energy conversion circuit works in the inductive region, and the first secondary switch SR 1 and the second secondary switch SR 2 Work in the inductive region to achieve the first secondary switch SR 1 and the second secondary switch SR 2 The zero voltage switch (ZVS) is turned on. The first secondary switch SR 1 Before shutting down, the current flows through the first secondary switch SR 1 Circulate and transfer energy to the primary side through the transformer, and switch SR on the first secondary side 1At the moment of shutdown, due to the first secondary switch SR 1 The current direction (the current direction is: DC2+→NS1→SR 1 →DC2-) cannot mutate suddenly, and the current will flow through the first secondary switch SR 1 The junction capacitance C 1 and the second secondary switch SR 2 The body diode D 2 Flow (the current direction at this time is: NS2→NS1→C 1 →D 2 ), generating LC (LC can include parasitic inductance in the line and leakage inductance and junction capacitance of the transformer C 1 ) oscillates. And it will switch SR on the first secondary side 1 The junction capacitance C 1 The high resonant voltage is generated on the first secondary switch SR 1 This results in a higher voltage stress on the first secondary switch SR. 1 damage.

[0037] In the embodiment of the present application, the energy conversion circuit can be controlled to work in the capacitive region to ensure that the first secondary switch SR 1 and the second secondary switch SR 2 Zero Current Switch (ZCS) is realized to turn off, solving the problem of excessive voltage stress on the secondary switch. 1 Before shutting down, the current direction has changed from forward (forward: DC2+→NS1→SR 1 →DC2-) switch to reverse direction (reverse direction: DC2-→D 1 →NS1→DC2+), until the second secondary switch SR 2 Opening and completing the switching (SR 2 The current direction after opening is: DC2+→NS2→SR 2 →DC2-), the first secondary switch SR 1 In this process, the ZCS is turned off, the resonant current keeps flowing, and no LC oscillation occurs (C 1 and line leakage inductance) causing excessive voltage stress on the secondary switch.

[0038] The energy conversion circuit of the embodiment of the present application, the control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the first secondary switch SR 1 The driving signal of the second secondary switch SR 2A driving signal is provided to increase the voltage between the first DC positive port DC1+ and the first DC negative port DC1- to a preset voltage. During the process of increasing the voltage between the first DC positive port DC1+ and the first DC negative port DC1-, the switch in the secondary bridge arm module 30 is turned off with zero current, which can reduce the voltage stress of the switch in the secondary bridge arm module 30, thereby reducing the voltage stress of the switch in the energy conversion circuit.

[0039] Optional, such as Figure 3 As shown, the resonance module 20 includes: a resonance inductor Lr, a resonance capacitor Cr and a transformer Tr; the transformer Tr includes a primary winding NP, a first secondary winding NS1 and a second secondary winding NS2; The resonant inductor Lr and the resonant capacitor Cr are respectively connected in series with the primary winding NP, and the resonant inductor Lr, the resonant capacitor Cr and the primary winding NP are connected in series at the midpoint of the first bridge arm (such as Figure 3 The middle point of the second bridge arm (point B as shown) Figure 3 The first end of the first secondary winding NS1 is connected to the second end of the second secondary winding NS2 and the second DC positive terminal DC2+, and the second end of the first secondary winding NS1 is connected to the first secondary switch SR 1 The first end of the second secondary winding NS2 is connected to the second secondary switch SR 2 The first end.

[0040] The excitation inductance may be integrated into the primary winding of the transformer Tr, or the excitation inductance may be independent of the primary winding of the transformer. Figure 3 The explanation is given assuming that the excitation inductance is integrated in the primary winding.

[0041] like Figure 3 As shown, the first end of the resonant inductor Lr is connected to the middle point of the second bridge arm (such as Figure 3 The second end of the resonant inductor Lr is connected to the first end of the primary winding NP, the second end of the primary winding NP is connected to the first end of the resonant capacitor Cr, and the second end of the resonant capacitor Cr is connected to the midpoint of the first bridge arm (as shown in FIG. Figure 3 point B as shown).

[0042] It should be noted that Figure 3 The connection mode in the resonant module 20 is a possible connection mode. r , the resonant capacitor Cr can be connected in series with the primary winding NP of the transformer Tr at will. For example, the resonant inductor L r With the resonant capacitor C rAfter being connected in series, it is connected between the middle point of the second bridge arm and the first end of the primary winding NP of the transformer Tr; for example, the resonant inductor L r With the resonant capacitor C r After being connected in series, it is connected between the midpoint of the first bridge arm and the second end of the primary winding NP of the transformer Tr; for example, the resonant capacitor C r The resonant inductor L is connected in series between the midpoint of the second bridge arm and the first end of the primary winding NP of the transformer Tr. r It is connected in series between the midpoint of the first bridge arm and the second end of the primary winding NP of the transformer Tr, which is not limited in the embodiment of the present application.

[0043] Optional, such as Figure 3 As shown, the energy conversion circuit also includes a first filter capacitor Cin and a second filter capacitor Co, wherein the two ends of the first filter capacitor are respectively connected between the first DC positive port DC1+ and the first DC negative port DC1-; the two ends of the second filter capacitor are respectively connected between the second DC positive port DC2+ and the second DC negative port DC2-.

[0044] The first filter capacitor Cin is a primary side filter capacitor, and the second filter capacitor Co is a secondary side filter capacitor, which is used to absorb high-frequency ripple.

[0045] When the energy conversion circuit precharges the bus capacitor Cbus, the energy of the energy conversion circuit is transferred from the low voltage (LV) side to the high voltage (HV) side. In order to reduce the problem of excessive stress on the low voltage side device (the switch in the secondary bridge arm module 30) when it is turned off. This embodiment of the application proposes a zero current shutdown control method, please refer to Figure 4 , Figure 4 Schematic diagram of a driving signal and conduction current of a secondary switch provided in an embodiment of the present application. Figure 4 As shown, the horizontal axis is time t, Vgs_SR is the driving signal of the secondary switch, and Ids_SR is the conduction current of the secondary switch. It can be seen that at the moment when the driving signal of the secondary switch is turned off, the conduction current of the secondary switch will be turned on through its body diode, thereby achieving zero current shutdown of the secondary switch. The embodiment of the present application can achieve safe operation of the device without adding additional absorption circuits, reduce system costs, and improve product reliability. The above-mentioned secondary switch can be the above-mentioned first secondary switch SR 1 Or the second secondary switch SR 2 , which will not be elaborated here.

[0046] Optionally, the control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the first secondary switch SR 1The driving signal of the second secondary switch SR 2 The drive signal is used to increase the voltage between the first DC positive port DC1+ and the first DC negative port DC1- to a preset voltage, and in the process of increasing the voltage between the first DC positive port DC1+ and the first DC negative port DC1-, the switch in the secondary bridge arm module 30 is turned off with zero current, including: The control module 40 determines the gain of the energy conversion circuit according to the first sampling voltage, the second sampling voltage and the turns ratio of the transformer Tr; the first sampling voltage is the sampling voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1-, and the second sampling voltage is the sampling voltage between the second DC positive terminal DC2+ and the second DC negative terminal DC2-; When the gain of the energy conversion circuit is less than 1, the control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, and the first secondary switch SR 1 The driving signal of the second secondary switch SR 2 A driving signal is provided to make the switch in the primary bridge arm module 10 work in a synchronous rectification mode, so that the switch in the secondary bridge arm module 30 is turned off with zero current; When the gain of the energy conversion circuit is greater than 1, the control module 40 determines the first bridge arm relative to the first secondary switch SR 1 The phase shift angle of the second bridge arm is the first phase shift angle, and the second bridge arm is relative to the first secondary switch SR 1 The phase shift angle is the second phase shift angle, so that the switch in the primary bridge arm module 10 is turned on with zero voltage, and the switch in the secondary bridge arm module 30 is turned off with zero current, the first phase shift angle is equal to the second phase shift angle, or the first phase shift angle is not equal to the second phase shift angle.

[0047] In the embodiment of the present application, the switch in the primary bridge arm module 10 operates in a synchronous rectification mode, so that the current passes through the switch in the primary bridge arm module 10 that is in the on state, but not through the body diode in the switch, which can improve the rectification efficiency and reduce the ripple. The switch in the secondary bridge arm module 30 is turned off at zero current, and no LC oscillation is generated, which can reduce the voltage stress of the switch in the secondary bridge arm module 30, thereby reducing the voltage stress of the switch in the energy conversion circuit.

[0048] When the energy conversion circuit precharges the bus capacitor Cbus, it transfers the voltage energy on the low voltage side to the high voltage side and charges the bus capacitor Cbus. Since the initial voltage of the high voltage side capacitor is zero, its voltage establishment process must go through two stages: gain < 1 and gain ≥ 1. The expression for gain is defined as follows: Ge=VHV_FB / (n×V LV_FB ); Where Ge is the gain of the energy conversion circuit, n is the turns ratio of the transformer, V HV_FB is the sampling voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1-, V LV_FB is the sampling voltage between the second DC positive terminal DC2+ and the second DC negative terminal DC2-.

[0049] In the embodiment of the present application, the energy conversion circuit can be controlled to work in the capacitive region to achieve the low-voltage side switch (the first secondary side switch SR 1 and the second secondary switch SR 2 ) to reduce the voltage stress on the low-side switch.

[0050] See also Figure 5 , Figure 5 Schematic diagram of voltage change between the first DC positive terminal DC1+ and the first DC negative terminal DC1- during pre-charging, and the first secondary switch SR 1 The driving signal Vgs_SR1 and the second switch S 2 Schematic diagram of the change of the driving signal Vgs_S2. Figure 5 As shown, in the stage where the gain Ge of the energy conversion circuit is less than 1, the switch in the primary bridge arm module 10 operates in the synchronous rectification mode, so that the switch in the secondary bridge arm module 30 is turned off with zero current. At this time, the voltage V between the first DC positive terminal DC1+ and the first DC negative terminal DC1- HV Gradually increase from 0 to V LV (At this time, Ge=1). In the stage where the gain Ge of the energy conversion circuit is ≥1, in order to increase the gain, the primary and secondary sides are introduced into the primary and secondary sides. Φ , and with D Φ Increase, control the switching frequency fs to gradually increase to ensure its gain and the ZCS action of the switch in the secondary bridge arm module 30, at this time, the voltage V between the first DC positive terminal DC1+ and the first DC negative terminal DC1- HV From V LV Gradually rises to the preset voltage (at this time, Ge≥1). As the output voltage V HV The higher the switching frequency fs, the greater the output voltage V HV When the gain Ge=1, the switching frequency fs is equal to the resonant frequency fr ( Figure 5 (not shown in the figure), when the gain Ge>1, the switching frequency fs is greater than the resonance frequency fr. The resonance frequency fr is the resonance frequency of the resonance module 20.

[0051] Optionally, the control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the first secondary switch SR 1 The driving signal of the second secondary switch SR 2 The driving signal is used to make the switch in the primary bridge arm module 10 work in the synchronous rectification mode, so that the switch in the secondary bridge arm module 30 is turned off with zero current, including: The control module 40 performs loop calculation according to the first sampled voltage to obtain a voltage loop calculation result, and determines the signal frequency according to the voltage loop calculation result; The control module 40 determines the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the first secondary switch SR 1 The frequency of the driving signal, the second secondary switch SR 2 The frequencies of the driving signals are all the signal frequency, so that the switches in the primary bridge arm module 10 work in the synchronous rectification mode, so that the switches in the secondary bridge arm module 30 are turned off with zero current.

[0052] In the embodiment of the present application, when the gain Ge of the energy conversion circuit is less than 1, the switch in the primary bridge arm module 10 operates in a synchronous rectification mode, and the switch in the secondary bridge arm module 30 is turned off with zero current.

[0053] When the gain Ge of the energy conversion circuit is less than 1, the real-time gain calculation is performed by sampling the input voltage and output voltage, and then converted into the switching frequency that needs to be controlled through the voltage controlled oscillator (VCO), and finally the driving signal is distributed through the wave generating module.

[0054] Optionally, the control module 40 determines the first bridge arm relative to the first secondary switch SR 1 The phase shift angle of the second bridge arm is the first phase shift angle, and the second bridge arm is relative to the first secondary switch SR 1 The phase shift angle is a second phase shift angle, so that the switch in the primary bridge arm module 10 is turned on with zero voltage, and the switch in the secondary bridge arm module 30 is turned off with zero current, including: The control module 40 determines the primary-secondary side phase shift angle according to the sampled current and the reference current; When the first phase shift angle is equal to the second phase shift angle, the control module determines that the primary-secondary side phase shift angle is the first phase shift angle.

[0055] When the first phase shift angle and the second phase shift angle are not equal, the control module determines the first bridge arm relative to the first secondary switch SR according to the primary-secondary side phase shift angle and the gain of the energy conversion circuit. 1 The phase shift angle of the second bridge arm is the first phase shift angle, and the second bridge arm is relative to the first secondary switch SR 1 The phase shift angle is the second phase shift angle, so that the switch in the primary bridge arm module 10 is turned on with zero voltage, and the switch in the secondary bridge arm module 30 is turned off with zero current; the sampling current is the first secondary switch SR 1 The sampling current between the second end of the DC2 and the second DC negative terminal DC2-.

[0056] In the embodiment of the present application, when the gain Ge of the energy conversion circuit is greater than or equal to 1, in order to limit the current on the low voltage side, the constant current control stage is entered, and the phase angle D of the primary and secondary sides is shifted by the current loop. Φ Closed-loop control is performed, and the switching frequency is adjusted in an open loop through the gain calculated in real time.

[0057] See also Figure 6 , Figure 6 Schematic diagram of a specific control structure of an energy conversion circuit provided in an embodiment of the present application. Figure 6 As shown, the control module 40 includes: a current control loop, a voltage control loop, a VCO, a gain determination and phase shift / frequency conversion modulation module, and a PWM wave generation module. Figure 6 The energy conversion circuit is used to convert the DC power on the low voltage side into the DC power output on the high voltage side.

[0058] The voltage controlled oscillator is used to calculate the signal frequency according to the voltage loop calculation result; The gain judgment and phase shift / frequency conversion modulation module is used to calculate the gain of the energy conversion circuit according to the first sampling voltage and the second sampling voltage; The gain judgment and phase shift / frequency conversion modulation module is further used to determine that the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the driving signal of the first secondary switch, and the frequency of the driving signal of the second secondary switch are all the signal frequency when the gain of the energy conversion circuit is less than 1; The gain judgment and phase shift / frequency conversion modulation module is also used to calculate the first phase shift angle and the second phase shift angle according to the gain of the energy conversion circuit and the primary-secondary side phase shift angle when the gain of the energy conversion circuit is greater than or equal to 1.

[0059] The current control loop is used to control the sampled current (such as Figure 6 I LV_FB ) and reference current (such as Figure 6I LV_Ref ) is subtracted and the result is looped to calculate the original secondary side phase shift angle D Φ Among them, the reference current I LV_Ref is the demand current of the low-voltage side of the energy conversion circuit currently set, and the sampling current I LV_FB is through Figure 6 The low-voltage side current sampling module is used to sample the first secondary side switch SR 1 The first secondary switch SR 1 The current between the second end of the DC2- to the second DC negative terminal DC2- may be a filtered current (for example, the sampling current I LV_FB It is through Figure 6 The current control loop is used for the stage with gain ≥ 1.

[0060] The voltage control loop is used to control the first sampled voltage (such as Figure 6 The V HV_FB ) and reference voltage (such as Figure 6 The V HV_Ref ) is subtracted and the result is loop calculated, and the voltage loop calculation result is output. The first sampling voltage V HV_FB is the sampling voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1-. The first sampling voltage V HV_FB is through Figure 6 The high-voltage side voltage sampling module is used to sample the voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1-. The voltage control loop is used in the stage where the gain is less than 1.

[0061] The VCO is used to calculate the signal frequency based on the voltage loop calculation results; The gain judgment and phase shift / frequency conversion modulation module is used to determine the gain of the first sampling voltage (such as Figure 6 The V HV_FB ) and the second sampling voltage (such as Figure 6 The V LV_FB ) calculate the gain of the energy conversion circuit; The gain judgment and phase shift / frequency conversion modulation module is also used to determine the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, and the frequency of the first secondary switch SR when the gain of the energy conversion circuit is less than 1. 1 The frequency of the driving signal, the second secondary switch SR 2 The frequencies of the driving signals are all the signal frequencies; The gain judgment and phase shift / frequency conversion modulation module is also used to determine that the first phase shift angle and the second phase shift angle are both the primary and secondary side phase shift angles when the gain of the energy conversion circuit is ≥ 1, or to calculate the first phase shift angle and the second phase shift angle according to the gain of the energy conversion circuit and the primary and secondary side phase shift angles. The signal frequency fs may also be referred to as the switching frequency fs.

[0062] The PWM wave transmission module is a pulse width modulation (PWM) module. The PWM wave transmission module can generate a wave transmission signal for each switch according to the gain judgment and the gain of the energy conversion circuit output by the phase shift / frequency conversion modulation module, as well as the signal frequency fs or the phase shift angle; the driving module amplifies and isolates the wave transmission signal of each switch to generate a driving signal for each switch, and the switch driving signal is used to drive the switch to be turned on or off.

[0063] In order to explain the control strategy in two stages (Ge<1 stage and Ge≥1 stage) in more detail, the typical control timing and waveform of Ge<1 and Ge≥1 are given below. Figure 7 , Figure 7 1 is a waveform diagram of the drive signal, resonant current, and current of the high and low voltage side switches of each switch when Ge<1 provided by an embodiment of the present application. Figure 8 , Figure 8 1 is a waveform diagram of the drive signal, resonant current, and current of the high and low voltage side switches of each switch when Ge≥1 provided in an embodiment of the present application. Fig. 9 , Fig. 9 This is another waveform diagram of the drive signal of each switch, the resonant current, and the current of the high and low voltage side switches when Ge≥1 provided in an embodiment of the present application.

[0064] Among them, Vgs_SR1 is the first secondary switch SR 1 The driving signal of Vgs_SR2 is the second secondary switch SR 2 The driving signal of the first switch S 1 The driving signal of the second switch S 2 The driving signal of the third switch S 3 The driving signal of the fourth switch S 4 The driving signal, V AB is the voltage between the middle point of the second bridge arm and the middle point of the first bridge arm, I Lr is the resonant current in the resonant module 20 (eg Figure 6 As shown, I Lr is the current on the resonant inductor Lr). S2 The second switch S2 The current, I S4 The fourth switch S 4 The current, I SR1 For the first secondary switch SR 1 The current, I SR2 For the second secondary switch SR 2 of current.

[0065] When Ge<1, Figure 7 The switch on the high-voltage side operates in synchronous rectification mode, t 2 The moment corresponds to the first secondary switch SR 1 The turn-off time corresponds to I SR1 The current waveform is ZCS shutdown; t 4 The time corresponds to the second secondary switch SR 2 The turn-off time corresponds to I SR2 The current waveform is ZCS shutdown.

[0066] When Ge≥1, there are two control methods. The first one is as follows: Figure 8 As shown, at this time, the first phase shift angle and the second phase shift angle are equal, and the original secondary side phase shift angle D is calculated. Φ After (i.e. the phase shift angle between the primary and secondary side drivers), the first phase shift angle and the second phase shift angle are both equal to the primary and secondary side phase shift angle D Φ .t 0 The moment corresponds to the second secondary switch SR 2 ZCS shutdown, t 1 The moment corresponds to the second switch S 2 ZVS is turned on, t 2 The moment corresponds to the first secondary switch SR 1 ZCS shutdown, t 3 The moment corresponds to the fourth switch S 4 The second type is as follows: Fig. 9 As shown, at this time, the first phase shift angle and the second phase shift angle are not equal, and the phase shift control between the high-voltage side bridge arms (the first bridge arm and the second bridge arm) is introduced by control, as shown in FIG. Fig. 9 D Φ1 and D Φ2 , corresponding to the first phase shift angle and the second phase shift angle mentioned above. 0 The moment corresponds to the second secondary switch SR 2 ZCS shutdown, t 2 The moment corresponds to the second switch S 2 ZVS is turned on, t 3 The moment corresponds to the first secondary switch SR 1 ZCS shutdown, t 4 The moment corresponds to the fourth switch S 4Through the above two control methods, the ZVS opening of the switch in the primary bridge arm module 10 and the ZCS closing of the switch in the secondary bridge arm module 30 can be achieved.

[0067] Optionally, when the gain of the energy conversion circuit is ≥1, and the first phase shift angle and the second phase shift angle are not equal, the first phase shift angle and the second phase shift angle are determined according to the following formula: D Φ1 =D α -(1-D y1 ); D Φ2 =D α ; D α =(1-D y1 +2D Φ ) / 2; If D Φ <D ΦB , then D y1 = k × (2D Φ +1) / (2-k); If D Φ ≥D ΦB , then D y1 =[2×D Φ ×(1-k)+2k-1] / k; D ΦB = (1-k) / 2, k=1 / Ge, Ge=V HV_FB / (n×V LV_FB ); Wherein, Ge is the gain of the energy conversion circuit, D Φ For loops (such as Figure 6 The current control loop shown in the figure calculates the primary-secondary side phase shift angle, D Φ1 is the first phase shift angle, D Φ2 is the second phase shift angle, n is the turns ratio of the transformer, V HV_FB is the first sampling voltage, V LV_FB is the second sampling voltage. The turns ratio of the transformer is the turns ratio of the primary winding and the secondary winding of the transformer.

[0068] Optionally, the signal frequency is positively correlated with the gain of the energy conversion circuit. Figure 5 As shown, as the gain Ge of the energy conversion circuit increases, the signal frequency (ie, the switching frequency fs) also increases.

[0069] in, Figure 3 , Figure 6 The energy conversion circuit shown can operate in the capacitive region.

[0070] based on Figure 3 , Figure 6 The energy conversion circuit shown in the figure, the embodiment of the present application provides a control method based on the energy conversion circuit. Fig.10 , Fig.10 is a flow chart of a control method based on an energy conversion circuit provided in an embodiment of the present application. Fig.10 As shown, the control method based on the energy conversion circuit includes the following steps: Step 1001, the control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the voltage between the first DC positive port and the first DC negative port increases to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive port and the first DC negative port, the switch in the secondary bridge arm module is turned off with zero current.

[0071] Step 1001 can be done by Figure 6 The energy conversion circuit shown in the figure is executed by the current control loop, voltage control loop, VCO, gain determination and phase shift / frequency conversion modulation module in the control module 40.

[0072] The control method based on the energy conversion circuit provided in the embodiment of the present application realizes the adjustment of the pre-charge voltage and the control of the voltage stress of the low-voltage side device without adding additional circuits, and has the characteristics of saving system cost and flexible control.

[0073] See also Fig.11 , Fig.11 Schematic diagram of a vehicle structure provided by an embodiment of the present application. Fig.11 As shown, the vehicle may include an energy conversion circuit 100 and a bus capacitor Cbus. The energy conversion circuit 100 may be used to convert the direct current on the low voltage side into direct current on the high voltage side to charge the bus capacitor Cbus.

[0074] Fig.11 The specific structure and working principle of the energy conversion circuit 100 can be found in the above Figures 1 to 6 The embodiments shown will not be described in detail here.

[0075] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0076] In the several embodiments provided in the present application, it should be understood that the disclosed energy conversion circuit, the control method based on the energy conversion circuit, and the vehicle can be implemented in other ways. For example, the energy conversion circuit embodiments described above are only schematic, for example, the division of the units is only a logical function division, and there may be other division methods in actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

Claims

1. An energy conversion circuit, characterized in that: It includes a primary bridge arm module, a resonance module, a secondary bridge arm module and a control module; the primary bridge arm module includes: a first bridge arm and a second bridge arm, and the secondary bridge arm module includes a first secondary switch and a second secondary switch; The midpoint of the second bridge arm is connected to the first end of the resonance module, and the midpoint of the first bridge arm is connected to the second end of the resonance module; the third end of the resonance module is connected to the first end of the second secondary switch, and the fourth end of the resonance module is connected to the first end of the first secondary switch; the first end of the first bridge arm is connected to the first end of the second bridge arm and the first DC positive port, the second end of the first bridge arm is connected to the second end of the second bridge arm and the first DC negative port, the fifth end of the resonance module is connected to the second DC positive port, and the second end of the first secondary switch is connected to the second end of the second secondary switch and the second DC negative port; The control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch to increase the voltage between the first DC positive port and the first DC negative port to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive port and the first DC negative port, the switch in the secondary bridge arm module is turned off with zero current.

2. The energy conversion circuit according to claim 1, characterized in that: The resonance module includes: a resonant inductor, a resonant capacitor and a transformer; the transformer includes a primary winding, a first secondary winding and a second secondary winding; The resonant inductor and the resonant capacitor are respectively connected in series with the primary winding, and the first secondary winding is connected in series with the second secondary winding; the resonant inductor, the resonant capacitor and the primary winding are connected in series between the midpoint of the first bridge arm and the midpoint of the second bridge arm, the first end of the first secondary winding is connected to the second end of the second secondary winding and the second DC positive port, the second end of the first secondary winding is connected to the first end of the first secondary switch, and the first end of the second secondary winding is connected to the first end of the second secondary switch.

3. The energy conversion circuit according to claim 2, characterized in that: The control module controls a driving signal of the first bridge arm, a driving signal of the second bridge arm, a driving signal of the first secondary switch, and a driving signal of the second secondary switch, so that a voltage between the first DC positive port and the first DC negative port increases to a preset voltage, and in the process of increasing the voltage between the first DC positive port and the first DC negative port, a switch in the secondary bridge arm module is turned off at zero current, including: The control module determines the gain of the energy conversion circuit according to a first sampling voltage, a second sampling voltage and the transformer turns ratio; the first sampling voltage is a sampling voltage between the first DC positive port and the first DC negative port, and the second sampling voltage is a sampling voltage between the second DC positive port and the second DC negative port; When the gain of the energy conversion circuit is less than 1, the control module controls the drive signal of the first bridge arm, the drive signal of the second bridge arm, the drive signal of the first secondary switch, and the drive signal of the second secondary switch, so that the switch in the primary bridge arm module operates in a synchronous rectification mode, so that the switch in the secondary bridge arm module is turned off with zero current; When the gain of the energy conversion circuit is greater than or equal to 1, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is a first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is a second phase shift angle, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current, the first phase shift angle is equal to the second phase shift angle, or the first phase shift angle is not equal to the second phase shift angle.

4. The energy conversion circuit according to claim 3, characterized in that: The control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the switch in the primary bridge arm module operates in a synchronous rectification mode, so that the switch in the secondary bridge arm module is turned off with zero current, including: The control module performs loop calculation according to the first sampling voltage to obtain a voltage loop calculation result, and determines the signal frequency according to the voltage loop calculation result; The control module determines that the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the driving signal of the first secondary switch, and the frequency of the driving signal of the second secondary switch are all the signal frequencies, so that the switches in the primary bridge arm module operate in a synchronous rectification mode, so that the switches in the secondary bridge arm module are turned off with zero current.

5. The energy conversion circuit according to claim 3, characterized in that: The control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is a first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is a second phase shift angle, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current, including: The control module determines the primary-secondary side phase shift angle according to the sampled current and the reference current; When the first phase shift angle is equal to the second phase shift angle, determining the original secondary side phase shift angle to be the first phase shift angle; When the first phase shift angle is not equal to the second phase shift angle, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary switch is the first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch is the second phase shift angle according to the primary-secondary side phase shift angle and the gain of the energy conversion circuit, so that the switch in the primary bridge arm module is turned on with zero voltage, and the switch in the secondary bridge arm module is turned off with zero current; the sampling current is the sampling current between the second end of the first secondary switch to the second DC negative terminal.

6. The energy conversion circuit according to claim 3, characterized in that: The control module includes: a current control loop, a voltage control loop, a voltage-controlled oscillator, a gain judgment and a phase shift / frequency conversion modulation module; The current control loop is used to perform loop calculation on the result of subtracting the sampled current from the reference current, and output the original-secondary side shift phase angle; The voltage control loop is used to perform loop calculation on the result of subtracting the first sampling voltage from the reference voltage, and output the voltage loop calculation result; The voltage controlled oscillator is used to calculate the signal frequency according to the voltage loop calculation result; The gain judgment and phase shift / frequency conversion modulation module is used to calculate the gain of the energy conversion circuit according to the first sampling voltage and the second sampling voltage; The gain judgment and phase shift / frequency conversion modulation module is further used to determine that the frequency of the driving signal of the first bridge arm, the frequency of the driving signal of the second bridge arm, the frequency of the driving signal of the first secondary switch, and the frequency of the driving signal of the second secondary switch are all the signal frequency when the gain of the energy conversion circuit is less than 1; The gain judgment and phase shift / frequency conversion modulation module is also used to determine that the first phase shift angle and the second phase shift angle are both the original-secondary side phase shift angles when the gain of the energy conversion circuit is greater than or equal to 1, or to calculate the first phase shift angle and the second phase shift angle based on the gain of the energy conversion circuit and the original-secondary side phase shift angles.

7. The energy conversion circuit according to claim 5, characterized in that: When the gain of the energy conversion circuit is greater than or equal to 1, and the first phase shift angle and the second phase shift angle are not equal, the first phase shift angle and the second phase shift angle are determined according to the following formula: D Φ1 =D α -(1-D y1 ); D Φ2 =D α ; D α =(1-D y1 +2D Φ ) / 2; If D Φ <D ΦB , then D y1 = k × (2D Φ +1) / (2-k); If D Φ ≥D ΦB , then D y1 =[2×D Φ ×(1-k)+2k-1] / k; Among them, k=1 / Ge;D ΦB = (1-k) / 2; Ge=V HV_FB / (n × V LV_FB ) ; Ge is the gain of the energy conversion circuit, D Φ is the original secondary side shift phase angle calculated by the loop, D Φ1 is the first phase shift angle, D Φ2 is the second phase shift angle, n is the turns ratio of the transformer, V HV_FB is the first sampling voltage, V LV_FB is the second sampling voltage.

8. The energy conversion circuit according to any one of claims 3 to 7, characterized in that: The signal frequency is positively correlated with the gain of the energy conversion circuit.

9. A control method based on an energy conversion circuit, characterized in that: The control method is applied to the energy conversion circuit according to any one of claims 1 to 8, and the control method comprises: The control module controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary switch, and the driving signal of the second secondary switch, so that the voltage between the first DC positive terminal and the first DC negative terminal increases to a preset voltage; Wherein, during the process of the voltage between the first DC positive port and the first DC negative port increasing, the switch in the secondary bridge arm module is turned off with zero current.

10. A vehicle, characterized in that: It comprises an energy conversion circuit and a bus capacitor as described in any one of claims 1 to 8, wherein the two ends of the bus capacitor are respectively connected to a first DC positive electrode interface of the energy conversion circuit and a first DC negative electrode interface of the energy conversion circuit, and the energy conversion circuit is used to charge the bus capacitor.

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