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

Abstract

An embodiment of the present application provides an energy conversion circuit, a control method based on the energy conversion circuit, and a vehicle. The energy conversion circuit includes a primary bridge arm module, a resonant 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. The secondary bridge arm module includes a first secondary switch and a second secondary switch. The control module controls the driving signals of the first bridge arm, the second bridge arm, the first secondary switch, and the second secondary switch to increase the voltage between the first DC positive terminal port and the first DC negative terminal port to a preset voltage. Wherein, during the process of increasing the voltage between the first DC positive terminal port and the first DC negative terminal port, the switches in the secondary bridge arm module are turned off with zero current. The embodiment of the present application can reduce the voltage stress of the switches in the energy conversion circuit.

Description

Technical Field

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

[0002] In an electric vehicle, a switching switch and a filter capacitor with a certain capacity are usually placed between a high-voltage battery and a DC bus of an 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, a surge current will be generated, bringing a safety risk. To suppress the impact of the surge current on the circuit, a pre-charge circuit is usually used to pre-charge the bus capacitor before the vehicle starts.

[0003] The traditional pre-charge method is to charge the bus capacitor by adding a pre-charge resistor. To reduce the system cost and eliminate the pre-charge resistor, currently, a bidirectional direct current / direct current (DC / DC) converter is usually used to convert the electrical energy of a low-voltage battery into high voltage to pre-charge the bus capacitor in advance. However, during the reverse pre-charge process, since the control method of the bidirectional DC / DC converter is usually based on soft-switching control, the switching tube on the low-voltage side is hard turned off, the turn-off current is large, and an excessive resonant voltage is generated across the switching tube, bringing a high voltage stress to the switching tube, thereby causing damage to the switching tube. Summary of the Invention

[0004] 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 embodiments of the present application provides an energy conversion circuit, including a primary bridge arm module, a resonant 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;

[0006] The midpoint of the second bridge arm is connected to the first end of the resonant module, and the midpoint of the first bridge arm is connected to the second end of the resonant module; the third end of the resonant module is connected to the first end of the second secondary switch, and the fourth end of the resonant 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 terminal 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 terminal port, the fifth end of the resonant module is connected to the second DC positive terminal 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 terminal port;

[0007] The control module controls the driving signals of the first arm, the driving signals of the second arm, the driving signals of the first secondary switch, and the driving signals of the second secondary switch, so as to increase the voltage between the first DC positive terminal and the first DC negative terminal to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive terminal and the first DC negative terminal, the switches in the secondary arm module are turned off with zero current.

[0008] Optionally, the resonance module includes: a resonance inductor, a resonance capacitor, and a transformer; the transformer includes a primary winding, a first secondary winding, and a second secondary winding;

[0009] The resonance inductor and the resonance 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 resonance inductor, the resonance capacitor, and the primary winding are connected in series between the midpoints of the first arm and the second 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 terminal, 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.

[0010] Optionally, the energy conversion circuit further includes a first filter capacitor and a second filter capacitor. The two ends of the first filter capacitor are respectively connected between the first DC positive terminal and the first DC negative terminal; the two ends of the second filter capacitor are respectively connected between the second DC positive terminal and the second DC negative terminal.

[0011] Optionally, the control module controls the driving signals of the first arm, the driving signals of the second arm, the driving signals of the first secondary switch, and the driving signals of the second secondary switch, so as to increase the voltage between the first DC positive terminal and the first DC negative terminal to a preset voltage. During the process of increasing the voltage between the first DC positive terminal and the first DC negative terminal, the switches in the secondary arm module are turned off with zero current, including:

[0012] The control module determines the gain of the energy conversion circuit according to the first sampling voltage, the second sampling voltage, and the transformer turns ratio; the first sampling voltage is the sampling voltage between the first DC positive terminal and the first DC negative terminal, and the second sampling voltage is the sampling voltage between the second DC positive terminal and the second DC negative terminal;

[0013] When the gain of the energy conversion circuit is less than 1, the control module controls the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary side switch, and the driving signals of the second secondary side switch, so that the switches in the primary side bridge arm module operate in the synchronous rectification mode, and the switches in the secondary side bridge arm module turn off with zero current;

[0014] 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 side switch is the first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary side switch is the second phase shift angle, so that the switches in the primary side bridge arm module turn on with zero voltage, the switches in the secondary side bridge arm module turn off with zero current, the first phase shift angle and the second phase shift angle are equal, or the first phase shift angle and the second phase shift angle are not equal.

[0015] Optionally, the control module controls the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary side switch, and the driving signals of the second secondary side switch, so that the switches in the primary side bridge arm module operate in the synchronous rectification mode, and the switches in the secondary side bridge arm module turn off with zero current, including:

[0016] The control module performs loop calculation according to the first sampling voltage to obtain a voltage loop calculation result, and determines a signal frequency according to the voltage loop calculation result;

[0017] The control module determines that the frequencies of the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary side switch, and the driving signals of the second secondary side switch are all the signal frequencies, so that the switches in the primary side bridge arm module operate in the synchronous rectification mode, and the switches in the secondary side bridge arm module turn off with zero current.

[0018] Optionally, the control module determines that the phase shift angle of the first bridge arm relative to the first secondary side switch is the first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary side switch is the second phase shift angle, so that the switches in the primary side bridge arm module turn on with zero voltage, and the switches in the secondary side bridge arm module turn off with zero current, including:

[0019] The control module determines the phase shift angle between the primary and secondary sides according to the sampled current and the reference current;

[0020] When the first phase shift angle and the second phase shift angle are equal, the control module determines that the phase shift angle between the primary and secondary sides is the first phase shift angle;

[0021] When the first phase shift angle and the second phase shift angle are not equal, the control module determines, according to the primary-secondary side phase shift angle and the gain of the energy conversion circuit, 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, so that the switches in the primary bridge arm module are turned on with zero voltage, and the switches in the secondary bridge arm module are turned off with zero current; the sampled current is the sampled current between the second terminal of the first secondary switch and the second DC negative terminal port.

[0022] Optionally, the control module includes: a current control loop, a voltage control loop, a voltage-controlled oscillator, a gain judgment and phase shift / frequency conversion modulation module;

[0023] 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 primary-secondary side phase shift angle;

[0024] The voltage control loop is used to perform loop calculation on the result of subtracting the first sampled voltage from the reference voltage, and output the voltage loop calculation result;

[0025] The voltage-controlled oscillator is used to calculate the signal frequency according to the voltage loop calculation result;

[0026] 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 sampled voltage and the second sampled voltage;

[0027] The gain judgment and phase shift / frequency conversion modulation module is further used to determine that the frequencies of the drive signals of the first bridge arm, the second bridge arm, the first secondary switch, and the second secondary switch are all the signal frequency when the gain of the energy conversion circuit is less than 1;

[0028] The gain judgment and phase shift / frequency conversion modulation module is further used to determine that both the first phase shift angle and the second phase shift angle are the primary-secondary side phase shift angle when the gain of the energy conversion circuit is greater than or equal to 1, or 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.

[0029] 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:

[0030] D Φ1 =D α -(1 - D y1 )

[0031] D Φ2 = D α ;

[0032] D α = (1 - D y1 + 2D Φ ) / 2;

[0033] If D Φ < D ΦB , then D y1 = k × (2D Φ + 1) / (2 - k);

[0034] If D Φ ≥ D ΦB , then D y1 = [2 × D Φ × (1 - k) + 2k - 1] / k;

[0035] D ΦB = (1 - k) / 2, k = 1 / Ge; Ge = V HV_FB / (n × V LV_FB );

[0036] Among them, Ge is the gain of the energy conversion circuit, D Φ is the phase shift angle between the primary and secondary sides calculated by the loop, D Φ1 is the first phase shift angle, D Φ2 is the second phase shift angle, n is the turn ratio of the transformer, V HV_FB is the first sampled voltage, V LV_FB is the second sampled voltage.

[0037] Optionally, the signal frequency is positively correlated with the gain of the energy conversion circuit.

[0038] Optionally, the energy conversion circuit operates in a capacitive region.

[0039] The second aspect of the embodiments of the present application provides a control method based on an energy conversion circuit. This control method is applied to the energy conversion circuit in the first aspect of the embodiments of the present application. The control method includes:

[0040] The control module controls the drive signals of the first bridge arm, the second bridge arm, the first secondary switch, and the second secondary switch to increase the voltage between the first DC positive terminal and the first DC negative terminal to a preset voltage;

[0041] Among them, during the process of increasing the voltage between the first DC positive terminal and the first DC negative terminal, the switches in the secondary bridge arm module turn off with zero current.

[0042] In the third aspect of the embodiments of the present application, a vehicle is provided, including the energy conversion circuit and the bus capacitor in the first aspect of the embodiments of the present application. Two ends of the bus capacitor are respectively connected to the first DC positive interface and the first DC negative interface of the energy conversion circuit, and the energy conversion circuit is used to charge the bus capacitor.

[0043] For the energy conversion circuit in the embodiments of the present application, the control module controls the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary switch, and the driving signals 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. During the process of the voltage between the first DC positive terminal and the first DC negative terminal increasing, the switches in the secondary bridge arm module turn off with zero current, which can reduce the voltage stress of the switches in the secondary bridge arm module, thereby reducing the voltage stress of the switches in the energy conversion circuit. Description of the Drawings

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0045] Figure 1 It is a schematic structural diagram of a pre-charge circuit in a vehicle provided by the embodiments of the present application;

[0046] Figure 2 It is a schematic structural diagram of a pre-charge circuit in another vehicle provided by the embodiments of the present application;

[0047] Figure 3 It is a schematic structural diagram of an energy conversion circuit provided by the embodiments of the present application;

[0048] Figure 4 It is a schematic diagram of the driving signals and conduction currents of a secondary switch provided by the embodiments of the present application;

[0049] Figure 5 It is a schematic diagram of the voltage change between the first DC positive terminal DC1+ and the first DC negative terminal DC1- during pre-charging, and the change diagrams of the driving signal Vgs_SR1 of the first secondary switch SR1 and the driving signal Vgs_S2 of the second switch S2 provided by the embodiments of the present application;

[0050] Figure 6 It is a schematic diagram of the specific control structure of an energy conversion circuit provided by the embodiments of the present application;

[0051] Figure 7 It is a waveform schematic diagram of the driving signals of each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge < 1 provided by an embodiment of the present application;

[0052] Figure 8 It is a waveform schematic diagram of the driving signals of each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge ≥ 1 provided by an embodiment of the present application;

[0053] Figure 9 It is another waveform schematic diagram of the driving signals of each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge ≥ 1 provided by an embodiment of the present application;

[0054] Figure 10 It is a flow schematic diagram of a control method based on an energy conversion circuit provided by an embodiment of the present application;

[0055] Figure 11 It is a structural schematic diagram of a vehicle provided by an embodiment of the present application. Detailed implementation manners

[0056] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0057] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. 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 further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, products, or devices.

[0058] Referring to "embodiment" in the present application means that a specific feature, structure, or characteristic described in combination with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments.

[0059] Please refer to Figure 1 , Figure 1 It is a structural schematic diagram of a precharge circuit in a vehicle provided by an embodiment of the present application. AsFigure 1 As shown, when the vehicle starts, since the voltage of the bus capacitor Cbus is zero, if K1 and K2 are directly closed to charge the bus capacitor Cbus with the high-voltage battery, a surge current will be generated, posing a safety risk. To suppress the impact of the surge current on the circuit, a pre-charge circuit (such as Figure 1 the switch K2, K3 and the pre-charge resistor R shown) is usually used to charge the bus capacitor, and the pre-charge resistor R plays a current-limiting role. The bus capacitor Cbus can also be called the pre-charge capacitor. Figure 1 It also includes an inverter and a motor M. The inverter can convert the voltage of the high-voltage battery into an alternating voltage to supply power to the motor M. Figure 1 The working principle is as follows: First, close K2 and K3, and open K1. Charge the bus capacitor Cbus through the pre-charge circuit. When the voltage of the bus capacitor Cbus reaches or approaches the voltage of the high-voltage battery, close K1 and K2, and open K3 to start the inverter to work, thereby driving the motor M. Figure 1 The high-voltage battery can be the power battery of the vehicle.

[0060] To reduce the system cost, currently, a bidirectional direct current / direct current (DC / DC) converter is used to convert the electrical energy of the low-voltage battery into high voltage to charge the bus capacitor Cbus in advance. Please refer to Figure 2 . Figure 2 This is a schematic structural diagram of another pre-charge circuit in a vehicle provided by an embodiment of the present application. As Figure 2 shown, the bidirectional DC / DC converter can convert the electrical energy of the low-voltage battery into high voltage to charge the bus capacitor Cbus in advance. Among them, Figure 2 the high-voltage battery can 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 supply power to the motor on the vehicle. The low-voltage battery can be the battery that supplies power to the low-voltage load on the vehicle, and the low-voltage battery can be the storage battery of the vehicle. The voltage of the low-voltage battery is generally about 12V or 24V or about 48V. The low-voltage load can be an electronic control unit (ECU) on the vehicle, and the ECU can include at least one of a car machine, a music player, a windshield wiper, a steering module, and a brake module.

[0061] The bidirectional DC / DC converter can work in a low-voltage to high-voltage mode or a high-voltage to low-voltage mode. When the bidirectional DC / DC converter works in the low-voltage to high-voltage mode, the bidirectional DC / DC converter can convert the electrical energy of the low-voltage battery into high voltage to charge the bus capacitor Cbus. When the bidirectional DC / DC converter works in the high-voltage to low-voltage mode, the bidirectional DC / DC converter can convert the electrical energy of the high-voltage battery into low voltage to charge the low-voltage battery.

[0062] Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of an energy conversion circuit provided by an embodiment of the present application. As Figure 3 shown, the energy conversion circuit may include a primary bridge arm module 10, a resonant 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, and the secondary bridge arm module 30 includes a first secondary switch SR1 and a second secondary switch SR2;

[0063] The midpoint of the second bridge arm is connected to the first end of the resonant module 20, and the midpoint of the first bridge arm is connected to the second end of the resonant module 20; the third end of the resonant module 20 is connected to the first end of the second secondary switch SR2, and the fourth end of the resonant module 20 is connected to the first end of the first secondary switch SR1; the first end of the first bridge arm is connected to the first end of the second bridge arm and the first DC positive terminal 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 terminal port DC1-, the fifth end of the resonant module 20 is connected to the second DC positive terminal port DC2+, and the second end of the first secondary switch SR1 is connected to the second end of the second secondary switch SR2 and the second DC negative terminal port DC2-;

[0064] The control module 40 controls the driving signals of the first bridge arm, the second bridge arm, the first secondary switch SR1, and the second secondary switch SR2, so that the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- increases to a preset voltage; wherein, during the process of increasing the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-, the switches in the secondary bridge arm module 30 are turned off with zero current.

[0065] As Figure 3As shown, the first bridge arm includes a first switch S1 and a second switch S2. The first end of the first switch S1 is connected to the first end of the first bridge arm. The second end of the first switch S1 is connected to the first end of the second switch S2 and the midpoint of the first bridge arm. The second end of the second switch S2 is connected to the second end of the first bridge arm. The driving signals of the first bridge arm include a first driving signal and a second driving signal. The control module 40 can control the driving module to send the first driving signal to the third end of the first switch S1, and the first driving signal is used to control the conduction or cutoff of the first switch S1. The control module 40 can control the driving module to send the second driving signal to the third end of the second switch S2, and the second driving signal is used to control the conduction or cutoff of the second switch S2. The frequencies of the first driving signal and the second driving signal are the same, and the first driving signal and the second driving signal are complementary signals, that is, within one cycle of the first driving signal, one of the first switch S1 and the second switch S2 is conducting and the other is cutoff. Exemplarily, the duty cycles of the first driving signal and the second driving signal are both 50% (ignoring the dead time).

[0066] The second bridge arm includes a third switch S3 and a fourth switch S4. The first end of the third switch S3 is connected to the first end of the second bridge arm. The second end of the third switch S3 is connected to the first end of the fourth switch S4 and the midpoint of the second bridge arm. The second end of the fourth switch S4 is connected to the second end of the second bridge arm. The driving signals of the second bridge arm include a third driving signal and a fourth driving signal. The control module 40 can control the driving module to send the third driving signal to the third end of the third switch S3, and the third driving signal is used to control the conduction or cutoff of the third switch S3. The control module 40 can control the driving module to send the fourth driving signal to the third end of the fourth switch S4, and the fourth driving signal is used to control the conduction or cutoff of the fourth switch S4. The frequencies of the third driving signal and the fourth driving signal are the same, and the third driving signal and the fourth driving signal are complementary signals, that is, within one cycle of the third driving signal, one of the third switch S3 and the fourth switch S4 is conducting and the other is cutoff. Exemplarily, the duty cycles of the third driving signal and the fourth driving signal are both 50% (ignoring the dead time).

[0067] The control module 40 can control the driving module to send the driving signal of the first secondary switch SR1 to the third terminal of the first secondary switch SR1, and the driving signal of the first secondary switch SR1 is used to control the conduction or turn-off of the first secondary switch SR1; the control module 40 can control the driving module to send the driving signal of the second secondary switch SR2 to the third terminal of the second secondary switch SR2, and the driving signal of the second secondary switch SR2 is used to control the conduction or turn-off of the second secondary switch SR2. The frequency of the driving signal of the first secondary switch SR1 is the same as that of the driving signal of the second secondary switch SR2, and the driving signal of the first secondary switch SR1 and the driving signal of the second secondary switch SR2 are complementary signals, that is, within one period of the driving signal of the first secondary switch SR1, one of the first secondary switch SR1 and the second secondary switch SR2 is conducting and the other is turned off. Exemplarily, the duty cycles of the driving signal of the first secondary switch SR1 and the driving signal of the second secondary switch SR2 are both 50% (ignoring the dead time).

[0068] Among them, the above driving module can be Figure 6 the driving module in

[0069] As Figure 3 shown, the switches in the primary bridge arm module 10 include: a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. The switches in the secondary bridge arm module 30 include a first secondary switch SR1 and a second secondary switch SR2. Each switch can include a junction capacitance and a body diode. For example, the junction capacitance C1 and the body diode D1 of the first secondary switch SR1, and the junction capacitance C2 and the body diode D2 of the second secondary switch SR2.

[0070] Among them, the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the first secondary switch SR1, and the second secondary switch SR2 can adopt Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or Insulate-Gate Bipolar Transistor (IGBT). MOSFET can also be called MOS tube or MOS transistor. Figure 3The switches are all exemplified by N-type MOS transistors, which can be abbreviated as NOMS transistors. The MOSFET can be a silicon carbide (SiC) MOSFET or a gallium nitride (GaN) MOSFET. The silicon carbide MOSFET is a MOSFET using silicon carbide material, and the gallium nitride MOSFET is a MOSFET using gallium nitride material. Among them, when the switch is a MOS transistor, the third terminal of the switch is the gate of the switch. Exemplarily, when the first switch S1 is an NMOS transistor, the third terminal of the first switch S1 is the gate of the first switch S1.

[0071] The voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- is V HV , and the voltage between the second DC positive terminal port DC2+ and the second DC negative terminal port DC2- is V LV . The energy conversion circuit can convert the voltage V LV between the second DC positive terminal port DC2+ and the second DC negative terminal port DC2- into the voltage V HV between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- and charge the bus capacitor Cbus.

[0072] Figure 3 The energy conversion circuit can be Figure 2 the bidirectional DC / DC converter shown in the figure. The first DC positive terminal port DC1+ and the first DC negative terminal port DC1- can be respectively connected to Figure 2 both ends of the bus capacitor Cbus. V LV is the voltage across the low-voltage battery, and V HV can be the voltage across the bus capacitor Cbus.

[0073] The preset voltage can be less than or equal to the rated voltage of the bus capacitor Cbus.

[0074] The traditional control strategy of the energy conversion circuit is to control the gain and current of the output voltage by adjusting the switching frequency. The energy conversion circuit operates in the inductive region, and the first secondary switch SR1 and the second secondary switch SR2 operate in the inductive region to achieve the zero-voltage switching (ZVS) turn-on of the first secondary switch SR1 and the second secondary switch SR2. Before the first secondary switch SR1 turns off, the current flows through the first secondary switch SR1 and transfers energy to the primary side through the transformer. At the moment when the first secondary switch SR1 turns off, since the current direction of the first secondary switch SR1 (this current direction is: DC2+→NS1→SR1→DC2-) cannot change suddenly, at this time, the current will flow through the junction capacitance C1 of the first secondary switch SR1 and the body diode D2 of the second secondary switch SR2 (the current direction at this time is: NS2→NS1→C1→D2), generating LC (LC can include the parasitic inductance in the circuit, the leakage inductance of the transformer, and the junction capacitance C1) oscillation. And a too high resonant voltage will be generated on the junction capacitance C1 of the first secondary switch SR1, bringing a high voltage stress to the first secondary switch SR1, thereby causing damage to the first secondary switch SR1.

[0075] In the embodiment of the present application, it is possible to control the energy conversion circuit to operate in the capacitive region to ensure that the first secondary switch SR1 and the second secondary switch SR2 achieve zero-current switching (ZCS) turn-off, solving the problem of too high voltage stress of the secondary switch. Since the current in the resonance module 20 is in advance, before the first secondary switch SR1 turns off, the current direction has switched from the forward direction (the forward direction is: DC2+→NS1→SR1→DC2-) to the reverse direction (the reverse direction is: DC2-→D1→NS1→DC2+), until the second secondary switch SR2 turns on to complete commutation (the current direction after SR2 turns on is: DC2+→NS2→SR2→DC2-). The first secondary switch SR1 is ZCS turned off during this process, and the resonant current always remains in the conducting state, and no LC oscillation (oscillation generated by C1 and the line leakage inductance) will occur to cause the situation of too high voltage stress of the secondary switch.

[0076] For the energy conversion circuit in the embodiment of the present application, the control module 40 controls the drive signals of the first bridge arm, the drive signals of the second bridge arm, the drive signal of the first secondary switch SR1, and the drive signal of the second secondary switch SR2, so that the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- increases to a preset voltage. During the process of increasing the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-, the switches in the secondary bridge arm module 30 turn off with zero current, which can reduce the voltage stress of the switches in the secondary bridge arm module 30, thereby reducing the voltage stress of the switches in the energy conversion circuit.

[0077] Optionally, as Figure 3 shown, the resonant module 20 includes: a resonant inductor Lr, a resonant 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;

[0078] 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 between the midpoint of the first arm (such as point B shown in Figure 3 ) and the midpoint of the second arm (such as point A shown in 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 port DC2+, the second end of the first secondary winding NS1 is connected to the first end of the first secondary switch SR1, and the first end of the second secondary winding NS2 is connected to the first end of the second secondary switch SR2.

[0079] An exciting inductor may be integrated in the primary winding of the transformer Tr, or the exciting inductor may be independent of the primary winding of the transformer. Figure 3 Taking the case where the exciting inductor is integrated in the primary winding as an example for explanation.

[0080] As Figure 3 shown, the first end of the resonant inductor Lr is connected to the midpoint of the second arm (such as point A shown in 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 arm (such as point B shown in Figure 3 ).

[0081] It should be noted that Figure 3 the connection method in the resonant module 20 is a possible connection method. The resonant inductor L r , the resonant capacitor Cr can be arbitrarily connected in series with the primary winding NP of the transformer Tr. For example, after the resonant inductor L r and the resonant capacitor C r are connected in series, they are connected between the midpoint of the second arm and the first end of the primary winding NP of the transformer Tr; or for another example, after the resonant inductor L r and the resonant capacitor C r are connected in series, they are connected between the midpoint of the first arm and the second end of the primary winding NP of the transformer Tr; or for another example, the resonant capacitor C r is connected in series between the midpoint of the second arm and the first end of the primary winding NP of the transformer Tr, and the resonant inductor L rIt is not limited in the embodiments of the present application to be connected in series between the midpoint of the first bridge arm and the second end of the primary winding NP of the transformer Tr.

[0082] Optionally, as Figure 3 shown, the energy conversion circuit further includes a first filter capacitor Cin and a second filter capacitor Co. The two ends of the first filter capacitor are respectively connected between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-; the two ends of the second filter capacitor are respectively connected between the second DC positive terminal port DC2+ and the second DC negative terminal port DC2-.

[0083] 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 ripples.

[0084] When the energy conversion circuit pre-charges 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 devices (switches in the secondary bridge arm module 30) when they are turned off. The embodiments of the present application propose a zero-current turn-off control method. Please refer to Figure 4 , Figure 4 which is a schematic diagram of the driving signal and conduction current of a secondary-side switch provided by the embodiments of the present application. As Figure 4 shown, the abscissa is time t, Vgs_SR is the driving signal of the secondary-side switch, and Ids_SR is the conduction current of the secondary-side switch. It can be seen that at the turn-off moment of the driving signal of the secondary-side switch, the conduction current of the secondary-side switch will conduct through its body diode, so as to realize the zero-current turn-off of the secondary-side switch. The embodiments of the present application can realize the safe operation of the device without adding an additional absorption circuit, reduce the system cost, and improve the product reliability. The above-mentioned secondary-side switch can be the above-mentioned first secondary-side switch SR1 or the above-mentioned second secondary-side switch SR2, which will not be elaborated here.

[0085] Optionally, the control module 40 controls the driving signal of the first bridge arm, the driving signal of the second bridge arm, the driving signal of the first secondary-side switch SR1, and the driving signal of the second secondary-side switch SR2, so that the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- increases to a preset voltage. During the process of increasing the voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-, the switches in the secondary bridge arm module 30 are turned off with zero current, including:

[0086] The control module 40 determines the gain of the energy conversion circuit according to the first sampling voltage, the second sampling voltage, and the turn ratio of the transformer Tr; the first sampling voltage is the sampling voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-, and the second sampling voltage is the sampling voltage between the second DC positive terminal port DC2+ and the second DC negative terminal port DC2-.

[0087] When the gain of the energy conversion circuit < 1, the control module 40 controls the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary switch SR1, and the driving signals of the second secondary switch SR2, so that the switches in the primary bridge arm module 10 work in the synchronous rectification mode, and the switches in the secondary bridge arm module 30 are turned off with zero current.

[0088] When the gain of the energy conversion circuit > 1, the control module 40 determines that the phase shift angle of the first bridge arm relative to the first secondary switch SR1 is the first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary switch SR1 is the second phase shift angle, so that the switches in the primary bridge arm module 10 are turned on with zero voltage, and the switches in the secondary bridge arm module 30 are turned off with zero current. The first phase shift angle and the second phase shift angle are equal, or the first phase shift angle and the second phase shift angle are not equal.

[0089] In the embodiment of the present application, the switches in the primary bridge arm module 10 work in the synchronous rectification mode, so that the current passes through the switches in the conducting state in the primary bridge arm module 10, rather than through the body diodes in the switches, which can improve the rectification efficiency and reduce the ripple. The switches in the secondary bridge arm module 30 are turned off with zero current, and no LC oscillation will occur, which can reduce the voltage stress of the switches in the secondary bridge arm module 30, thereby reducing the voltage stress of the switches in the energy conversion circuit.

[0090] When the energy conversion circuit pre-charges 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 capacitor on the high-voltage side is zero, its voltage establishment process must go through two stages: gain < 1 and gain ≥ 1. The expression of the gain is defined as follows:

[0091] Ge = V HV_FB / (n × V LV_FB ) ;

[0092] where Ge is the gain of the energy conversion circuit, n is the turn ratio of the transformer, V HV_FB is the sampling voltage between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1-, and V LV_FBis the sampled voltage between the second DC positive terminal port DC2+ and the second DC negative terminal port DC2-.

[0093] In the embodiments of the present application, the energy conversion circuit can be controlled to operate in the capacitive region to achieve zero-current switching (ZCS) turn-off of the low-voltage side switches (the first secondary side switch SR1 and the second secondary side switch SR2), thereby reducing the voltage stress of the low-voltage side switches.

[0094] Please refer to Figure 5 , Figure 5 is a schematic diagram of the voltage change between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- during the pre-charging process, and a schematic diagram of the change of the driving signal Vgs_SR1 of the first secondary side switch SR1 and the driving signal Vgs_S2 of the second switch S2 provided by the embodiments of the present application. As Figure 5 shown, in the stage where the gain Ge of the energy conversion circuit is less than 1, the switches in the primary side bridge arm module 10 operate in the synchronous rectification mode to turn off the switches in the secondary side bridge arm module 30 with zero current. At this time, the voltage V HV between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- gradually rises from 0 to V LV (at this time, Ge = 1). In the stage where the gain Ge of the energy conversion circuit is greater than or equal to 1, in order to increase the gain, a primary-secondary side phase shift angle D Φ is introduced on the primary and secondary sides. And as D Φ increases, the switching frequency fs is gradually increased to ensure its gain and the ZCS operation of the switches in the secondary side bridge arm module 30. At this time, the voltage V HV between the first DC positive terminal port DC1+ and the first DC negative terminal port DC1- gradually rises from V LV to a preset voltage (at this time, Ge ≥ 1). As the output voltage V HV of the energy conversion circuit is higher, the switching frequency fs is larger, until the output voltage V HV reaches the preset voltage. Among them, when the gain Ge = 1, the switching frequency fs is equal to the resonance frequency fr ( Figure 5 not shown in the figure), and 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.

[0095] Optionally, the control module 40 controls the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signal of the first secondary side switch SR1, and the driving signal of the second secondary side switch SR2, so that the switches in the primary side bridge arm module 10 operate in the synchronous rectification mode to turn off the switches in the secondary side bridge arm module 30 with zero current, including:

[0096] The control module 40 performs a loop calculation based on the first sampled voltage to obtain a voltage loop calculation result, and determines a signal frequency according to the voltage loop calculation result;

[0097] The control module 40 determines that the frequencies of the driving signals of the first bridge arm, the driving signals of the second bridge arm, the driving signals of the first secondary side switch SR1, and the driving signals of the second secondary side switch SR2 are all the signal frequencies, so that the switches in the primary side bridge arm module 10 operate in the synchronous rectification mode, and the switches in the secondary side bridge arm module 30 turn off with zero current.

[0098] In the embodiment of the present application, in the stage where the gain Ge of the energy conversion circuit is less than 1, the switches in the primary side bridge arm module 10 operate in the synchronous rectification mode, and the switches in the secondary side bridge arm module 30 turn off with zero current.

[0099] In the stage where the gain Ge of the energy conversion circuit is less than 1, the input voltage and the output voltage are sampled for real-time gain calculation, and then converted into the switching frequency to be controlled through a Voltage Controlled Oscillator (VCO), and finally the driving signals are allocated through a wave generating module.

[0100] Optionally, the control module 40 determines that the phase shift angle of the first bridge arm relative to the first secondary side switch SR1 is a first phase shift angle, and the phase shift angle of the second bridge arm relative to the first secondary side switch SR1 is a second phase shift angle, so that the switches in the primary side bridge arm module 10 turn on with zero voltage, and the switches in the secondary side bridge arm module 30 turn off with zero current, including:

[0101] The control module 40 determines the primary and secondary side phase shift angles according to the sampled current and the reference current;

[0102] When the first phase shift angle and the second phase shift angle are equal, the control module determines that the primary and secondary side phase shift angles are the first phase shift angle.

[0103] When the first phase shift angle and the second phase shift angle are not equal, the control module determines the phase shift angle of the first bridge arm relative to the first secondary side switch SR1 as the first phase shift angle and the phase shift angle of the second bridge arm relative to the first secondary side switch SR1 as the second phase shift angle according to the primary and secondary side phase shift angles and the gain of the energy conversion circuit, so that the switches in the primary side bridge arm module 10 turn on with zero voltage, and the switches in the secondary side bridge arm module 30 turn off with zero current; the sampled current is the sampled current between the second terminal of the first secondary side switch SR1 and the second DC negative terminal port DC2-.

[0104] In the embodiment of the present application, during the stage where the gain Ge of the energy conversion circuit is ≥ 1, in order to limit the current on the low-voltage side and enter the constant-current control stage, the phase shift angle D between the primary and secondary sides is controlled in a closed loop through the current loop, and at the same time, the switching frequency is adjusted in an open loop through the gain calculated in real time. Φ For closed-loop control, and the switching frequency is adjusted in an open loop through the gain calculated in real time.

[0105] Please refer to Figure 6 , Figure 6 which is a schematic diagram of the specific control structure of an energy conversion circuit provided by an embodiment of the present application. As Figure 6 shown, the control module 40 includes: a current control loop, a voltage control loop, a VCO, a gain judgment and phase shift / frequency conversion modulation module, and a PWM wave generation module. Figure 6 The energy conversion circuit is used to convert the direct current on the low-voltage side into a direct current output on the high-voltage side.

[0106] The voltage-controlled oscillator is used to calculate the signal frequency according to the calculation result of the voltage loop;

[0107] 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 sampled voltage and the second sampled voltage;

[0108] The gain judgment and phase shift / frequency conversion modulation module is further used to determine that the frequencies of the drive signals of the first bridge arm, the second bridge arm, the first secondary switch, and the second secondary switch are all the signal frequencies when the gain of the energy conversion circuit is less than 1;

[0109] The gain judgment and phase shift / frequency conversion modulation module is further 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 phase shift angle between the primary and secondary sides when the gain of the energy conversion circuit is greater than or equal to 1.

[0110] The current control loop is used to perform loop calculation on the result of subtracting the sampled current (such as I Figure 6 shown in LV_FB ) and the reference current (such as I Figure 6 shown in LV_Ref ) and output the phase shift angle D between the primary and secondary sides Φ . Among them, the reference current I LV_Ref is the required current of the low-voltage side currently set by the energy conversion circuit, and the sampled current I LV_FB is obtained through Figure 6It is obtained by sampling through the low-voltage side current sampling module. The low-voltage side current sampling module is used to sample the current between the second end of the first secondary switch SR1 and the second DC negative terminal DC2-. The current between the second end of the first secondary switch SR1 and the second DC negative terminal DC2- can be the filtered current (for example, the sampled current I LV_FB is the current filtered by Figure 6 the second filter capacitor Co in). The current control loop is used for the stage where the gain ≥ 1.

[0111] The voltage control loop is used to perform loop calculation on the result of subtracting the reference voltage (such as Figure 6 the V shown HV_FB ) from the first sampled voltage (such as Figure 6 the V shown HV_Ref ), and output the voltage loop calculation result. The first sampled voltage V HV_FB is the sampled voltage between the first DC positive terminal DC1+ and the first DC negative terminal DC1-. The first sampled voltage V HV_FB is obtained by sampling through Figure 6 the high-voltage side voltage sampling module in. 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 for the stage where the gain < 1.

[0112] The VCO is used to calculate the signal frequency according to the voltage loop calculation result;

[0113] 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 sampled voltage (such as Figure 6 the V shown HV_FB ) and the second sampled voltage (such as Figure 6 the V shown LV_FB );

[0114] The gain judgment and phase shift / frequency conversion modulation module is also used to determine that the frequencies of the drive signals of the first bridge arm, the second bridge arm, the first secondary switch SR1, and the second secondary switch SR2 are all the signal frequency when the gain of the energy conversion circuit < 1;

[0115] 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-secondary side phase shift angle when the gain of the energy conversion circuit ≥ 1, or 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. Among them, the signal frequency fs can also be called the switching frequency fs.

[0116] The PWM wave generation module is a Pulse Width Modulation (PWM) module. The PWM wave generation module can generate the wave signals 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 drive module amplifies and isolates the wave signals for each switch to generate the drive signals for each switch, and the drive signals for the switch are used to drive the conduction or turn-off of the switch.

[0117] To illustrate the control strategies in two stages (the stage where Ge < 1 and the stage where Ge ≥ 1) in more detail, the typical control timings and waveforms for Ge < 1 and Ge ≥ 1 will be given separately below. Please refer to Figure 7 , Figure 7 is a schematic diagram of the waveforms of the drive signals for each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge < 1 provided by an embodiment of the present application. Please refer to Figure 8 , Figure 8 is a schematic diagram of the waveforms of the drive signals for each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge ≥ 1 provided by an embodiment of the present application. Please refer to Figure 9 , Figure 9 is another schematic diagram of the waveforms of the drive signals for each switch, the resonant current, and the currents of the high- and low-voltage side switches when Ge ≥ 1 provided by an embodiment of the present application.

[0118] Among them, Vgs_SR1 is the drive signal of the first secondary side switch SR1, Vgs_SR2 is the drive signal of the second secondary side switch SR2, Vgs_S1 is the drive signal of the first switch S1, Vgs_S2 is the drive signal of the second switch S2, Vgs_S3 is the drive signal of the third switch S3, Vgs_S4 is the drive signal of the fourth switch S4, V AB is the voltage between the midpoint of the second bridge arm and the midpoint of the first bridge arm, I Lr is the resonant current in the resonant module 20 (as Figure 6 shown, I Lr is the current on the resonant inductor Lr). I S2 is the current of the second switch S2, I S4 is the current of the fourth switch S4, I SR1 is the current of the first secondary side switch SR1, I SR2 is the current of the second secondary side switch SR2.

[0119] When Ge < 1, as Figure 7 shown. The switches on the high-voltage side operate in the synchronous rectification mode. The t2 moment corresponds to the turn-off moment of the first secondary side switch SR1, and the corresponding current waveform of I SR1 is ZCS turn-off; the t4 moment corresponds to the turn-off moment of the second secondary side switch SR2, corresponding to ISR2 The current waveform of

[0120] When Ge ≥ 1, there are two control methods. The first is as Figure 8 shown. At this time, the first phase-shift angle and the second phase-shift angle are equal. After calculating the phase-shift angle D Φ between the primary and secondary sides (i.e., the phase-shift angle between the primary and secondary drives), both the first phase-shift angle and the second phase-shift angle are equal to the phase-shift angle D Φ between the primary and secondary sides. At time t0, it corresponds to the ZCS turn-off of the second secondary switch SR2. At time t1, it corresponds to the ZVS turn-on of the second switch S2. At time t2, it corresponds to the ZCS turn-off of the first secondary switch SR1. At time t3, it corresponds to the ZVS turn-on of the fourth switch S4. The second is as Figure 9 shown. At this time, the first phase-shift angle and the second phase-shift angle are not equal. By controlling the phase-shift control introduced between the high-voltage side bridge arms (the first bridge arm and the second bridge arm), as Figure 9 shown as D Φ1 and D Φ2 , they respectively correspond to the above-mentioned first phase-shift angle and the second phase-shift angle. At time t0, it corresponds to the ZCS turn-off of the second secondary switch SR2. At time t2, it corresponds to the ZVS turn-on of the second switch S2. At time t3, it corresponds to the ZCS turn-off of the first secondary switch SR1. At time t4, it corresponds to the ZVS turn-on of the fourth switch S4. Through the above two control methods, the ZVS turn-on of the switches in the primary side bridge arm module 10 and the ZCS turn-off of the switches in the secondary side bridge arm module 30 can be achieved.

[0121] Optionally, when the gain of the energy conversion circuit ≥ 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:

[0122] D Φ1 = D α - (1 - D y1 );

[0123] D Φ2 = D α ;

[0124] D α = (1 - D y1 + 2D Φ ) / 2;

[0125] If D Φ < D ΦB , then D y1 = k × (2D Φ + 1) / (2 - k);

[0126] If D Φ ≥ D ΦB , then Dy1 = [2×D Φ × (1 - k) + 2k - 1] / k;

[0127] D ΦB = (1 - k) / 2, k = 1 / Ge, Ge = V HV_FB / (n×V LV_FB );

[0128] Wherein, Ge is the gain of the energy conversion circuit, and D Φ is the primary-secondary side phase shift angle calculated by the loop (such as Figure 6 the current control loop shown), D Φ1 is the first phase shift angle, D Φ2 is the second phase shift angle, n is the turn ratio of the transformer, V HV_FB is the first sampled voltage, and V LV_FB is the second sampled voltage. The turn ratio of the transformer is the turn ratio of the primary winding and the secondary winding of the transformer.

[0129] Optionally, the signal frequency is positively correlated with the gain of the energy conversion circuit. As Figure 5 shown, as the gain Ge of the energy conversion circuit increases, the signal frequency (i.e., the switching frequency fs) also increases.

[0130] Wherein, Figure 3 , Figure 6 the energy conversion circuit shown can operate in the capacitive region.

[0131] Based on Figure 3 , Figure 6 the energy conversion circuit shown, an embodiment of the present application provides a control method based on the energy conversion circuit. Please refer to Figure 10 , Figure 10 which is a schematic flow chart of a control method based on the energy conversion circuit provided by an embodiment of the present application. As Figure 10 shown, the control method based on the energy conversion circuit includes the following steps:

[0132] Step 1001, the control module controls the driving signals of the first bridge arm, the second bridge arm, the first secondary switch, and 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 increasing the voltage between the first DC positive terminal and the first DC negative terminal, the switches in the secondary bridge arm module turn off with zero current.

[0133] Step 1001 can be executed by the current control loop, voltage control loop, VCO, gain judgment, and phase shift / frequency conversion modulation module in the control module 40 of the energy conversion circuit shown in Figure 6 .

[0134] The control method based on the energy conversion circuit provided by the embodiment of the present application realizes the regulation of the pre-charge voltage and the control of the voltage stress of the low-voltage side devices without adding extra circuits, and has the characteristics of saving system cost and flexible control.

[0135] Please refer to Figure 11 , Figure 11 which is a schematic structural diagram of a vehicle provided by the embodiment of the present application. As Figure 11 shown, the vehicle may include an energy conversion circuit 100 and a bus capacitor Cbus. The energy conversion circuit 100 can 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.

[0136] Figure 11 For the specific structure and working principle of the energy conversion circuit 100 in Figures 1 to 6 shown, reference may be made to the above-mentioned

[0137] embodiment shown, which will not be elaborated here.

[0138] In several embodiments provided by 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 merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. 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, 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; 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 electrode 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; 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.

2. The energy conversion circuit according to claim 1, 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.

3. The energy conversion circuit according to claim 1, 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.

4. The energy conversion circuit according to claim 1, 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.

5. The energy conversion circuit according to claim 1, 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.

6. The energy conversion circuit according to any one of claims 1 to 5, characterized in that: The signal frequency is positively correlated with the gain of the energy conversion circuit.

7. 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 6, 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.

8. A vehicle, characterized in that: It comprises an energy conversion circuit and a bus capacitor as described in any one of claims 1 to 6, 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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