Control method and device of vehicle-mounted charger, vehicle-mounted charging system and vehicle

Abstract

The application discloses a control method and device of a vehicle-mounted charger, a vehicle-mounted charging system and a vehicle, and relates to the technical field of vehicle-mounted charging. The control method comprises the following steps: through controlling the action of the secondary side power switch tube of the isolation type DC / DC circuit in the vehicle-mounted charger, the pre-charging process of the DC bus capacitor is realized by using the electric energy of the power battery to charge the DC bus capacitor; the soft start of the isolation type DC / DC circuit is realized by gradually increasing the duty cycle at the start time, the oscillation of the resonance current is avoided, and the smoothness of the charging voltage output to the DC bus capacitor is improved; meanwhile, the loss in the isolation type DC / DC circuit is reduced by reducing the switching frequency after the duty cycle is stable, so that the gain of the output charging voltage is improved, and the fast charging of the DC bus capacitor is realized. The whole pre-charging process is realized by reusing the isolation type DC / DC circuit in the vehicle-mounted charger, no additional hardware is needed, and the application cost of the vehicle-mounted charger is effectively saved.

Description

Technical Field

[0001] This invention relates to the field of on-board charging technology, and in particular to a control method, device, on-board charging system, and vehicle for an on-board charger. Background Technology

[0002] The On-Board Charger (OBC) is the core power conversion component of the AC charging system in new energy vehicles. As a key device for vehicle energy replenishment, it is a crucial factor determining the charging power and efficiency of new energy vehicles. Therefore, the safe and reliable operation of the OBC is fundamental to the normal operation of new energy vehicles. The OBC includes a front-end PFC (Power Factor Correction Circuit) and a back-end isolated DC / DC (Direct Current to Direct Current Conversion Circuit). To ensure the safe and reliable operation of the OBC, a DC bus capacitor is connected in parallel on the DC bus between the output of the PFC circuit and the input of the isolated DC / DC circuit. Before the OBC is powered on and operating normally, this DC bus capacitor needs to be pre-charged to avoid physical damage to the components within the OBC caused by the surge current at power-on. Therefore, designing a pre-charge control strategy for the DC bus capacitor is one of the important technological development directions for OBCs. Summary of the Invention

[0003] The purpose of this invention is to provide a control method, device, on-board charging system, and vehicle for an on-board charger, and to provide a pre-charge control strategy for DC bus capacitors that achieves lower costs.

[0004] To solve the above technical problems, the present invention provides a control method for an on-board charger. The on-board charger includes a PFC circuit, a DC bus capacitor, and an isolated DC / DC circuit. The DC side of the PFC circuit and the first DC side of the isolated DC / DC circuit are both connected in parallel with the DC bus capacitor. The second DC side of the isolated DC / DC circuit is connected to a power battery. The control method for the on-board charger includes: The secondary power switches in the isolated DC / DC circuit are controlled to operate according to a preset initial duty cycle; wherein, the two secondary power switches in the same bridge arm are complementary in conduction. The duty cycle of the secondary power switch is controlled to increase from the preset initial duty cycle to the duty cycle threshold. After the duty cycle of the secondary power switch reaches the duty cycle threshold, the switching frequency of the secondary power switch is reduced to charge the DC bus capacitor based on the power battery's electrical energy. If the charging process reaches the preset end condition, the secondary power switch is controlled to stop operating, so as to complete the pre-charging of the DC bus capacitor.

[0005] Optional, also includes: With the resonant current of the resonant cavity in the isolated DC / DC circuit being less than or equal to a preset current threshold as a constraint, the rise time required for the duty cycle of the secondary power switch to linearly increase from the preset initial duty cycle to the duty cycle threshold is determined. Controlling the duty cycle of the secondary power switch to increase from the preset initial duty cycle to the duty cycle threshold includes: The duty cycle of the secondary power switch is controlled to linearly increase from the preset initial duty cycle to the duty cycle threshold within the rise time.

[0006] Optionally, controlling the switching frequency of the secondary-side power switch to decrease includes: Determine the real-time switching frequency of the secondary power switch; Based on the relationship between the real-time switching frequency and the preset frequency range, the switching frequency of the secondary power switch is controlled to decrease according to the preset step size corresponding to the preset frequency range. The preset step size is positively correlated with the frequency corresponding to the preset frequency range; the correspondence between the preset frequency range and the preset step size is determined in advance based on the gain curve of the isolated DC / DC circuit.

[0007] Optional, also includes: Determine the bus voltage across the DC bus capacitor; Based on the relationship between the bus voltage across the DC bus capacitor and the preset pre-charge voltage, it is determined whether the charging process has reached the preset termination condition.

[0008] Optionally, based on the relationship between the bus voltage across the DC bus capacitor and the preset pre-charge voltage, it is determined whether the charging process has reached the preset termination condition, including: Determine whether the bus voltage across the DC bus capacitor is continuously greater than the preset pre-charge voltage within a preset time period; If so, the charging process is determined to have reached the preset termination condition; If not, it is determined that the charging process has not reached the preset termination condition.

[0009] Optional, also includes: Detect the resonant current of the resonant cavity in the isolated DC / DC circuit; If the resonant current exceeds the current protection threshold, the secondary power switch will be controlled to stop operating.

[0010] Optional, also includes: Detect the bus voltage across the DC bus capacitor; If the bus voltage across the DC bus capacitor exceeds the voltage protection threshold, the secondary power switch will be controlled to stop operating.

[0011] To address the aforementioned technical problems, the present invention also provides an electronic device, comprising: Memory, used to store computer programs; A processor for implementing the steps of the control method for the on-board charger as described above.

[0012] To address the aforementioned technical problems, the present invention also provides an on-board charging system, including an on-board charger and an electronic device as described above, wherein the electronic device is connected to the on-board charger.

[0013] To address the aforementioned technical problems, the present invention also provides a vehicle, including a power battery and an on-board charging system as described above, wherein the on-board charging system is connected to the power battery.

[0014] This invention provides a control method for an on-board charger. Before the on-board charger is powered on and begins normal forward operation, the secondary power switch of the isolated DC / DC circuit in the on-board charger is controlled to pre-charge the DC bus capacitor using the power battery's electrical energy. During startup, a gradual increase in the duty cycle achieves soft-start of the isolated DC / DC circuit, avoiding resonant current oscillations and improving the smoothness of the charging voltage output to the DC bus capacitor. Simultaneously, after the duty cycle stabilizes, the switching frequency is reduced to decrease switching losses in the isolated DC / DC circuit, thereby increasing the output charging voltage gain and achieving rapid charging of the DC bus capacitor. The entire pre-charging process reuses the isolated DC / DC circuit in the on-board charger, eliminating the need for additional hardware and effectively saving on-board charger application costs.

[0015] The present invention also provides an electronic device, an on-board charging system, and a vehicle, which have the same beneficial effects as the control method of the on-board charger described above. Attached Figure Description

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

[0017] Figure 1 A flowchart illustrating a control method for an on-board charger provided by the present invention; Figure 2 This invention provides a structural schematic diagram of an on-board charger; Figure 3 This invention provides a schematic diagram of the specific circuit structure of an on-board charger; Figure 4 A schematic diagram of the specific control flow of a control method for an on-board charger provided by the present invention; Figure 5 This is a schematic diagram of the structure of an electronic device provided by the present invention. Detailed Implementation

[0018] The core of this invention is to provide a control method, device, on-board charging system, and vehicle for an on-board charger. The entire pre-charging process reuses the isolated DC / DC circuit in the on-board charger, eliminating the need for additional hardware and effectively saving on the application cost of the on-board charger.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] See Figure 1 As shown, Figure 1 A flowchart illustrating a control method for an on-board charger provided by the present invention; see also Figure 2 As shown, Figure 2 This invention provides a schematic diagram of the structure of an on-board charger. To solve the above-mentioned technical problems, this invention provides a control method for an on-board charger. The on-board charger includes a PFC circuit 1, a DC bus capacitor Cbus, and an isolated DC / DC circuit 2. The DC side of the PFC circuit 1 and the first DC side of the isolated DC / DC circuit 2 are both connected in parallel with the DC bus capacitor Cbus. The second DC side of the isolated DC / DC circuit 2 is connected to the power battery. The control method for the on-board charger includes: S11: Control the operation of the secondary power switch in the isolated DC / DC circuit 2 according to the preset initial duty cycle; wherein, the two secondary power switches in the same bridge arm are complementary in conduction; It is easy to understand that, considering the pre-charging of the DC bus capacitor Cbus needs to be completed before the OBC is powered on and begins normal forward operation, the vehicle's power battery connected to the OBC output side will contain stored electrical energy at this time. Furthermore, the DC bus capacitor Cbus is connected to the power battery through the isolated DC / DC circuit 2 in the OBC. Therefore, this application provides a new method for pre-charging the DC bus capacitor Cbus. This method utilizes the operation of the isolated DC / DC circuit 2 downstream of the OBC to reverse-transfer the battery energy from the power battery connected to the OBC output side to the DC bus, thereby completing the pre-charging of the DC bus capacitor Cbus. Therefore, before the OBC is powered on and begins normal forward operation, this application pre-enables the secondary power switch in the isolated DC / DC circuit 2. By controlling the operation of the secondary power switch in the isolated DC / DC circuit 2, a discharge circuit for battery energy is constructed, enabling the battery energy to be effectively reverse-transferred to the DC bus capacitor Cbus for pre-charging.

[0021] It should be noted that since the isolated DC / DC circuit 2 in the OBC is implemented using a bridge circuit topology, it includes symmetrical bridge arm structures (for example, a bridge arm structure includes two vertically symmetrical branches: an upper bridge arm and a lower bridge arm). Each symmetrical bridge arm structure includes at least two symmetrical branches, and at least one power switch is configured on any one of these branches. To prevent shoot-through short circuits in one bridge arm structure, it is necessary to control the complementary conduction of the two secondary power switches corresponding to the two branches within the same bridge arm. Simultaneously, a specific preset initial duty cycle is set as a control command to control the secondary power switches to start smoothly with a low conduction rate. When the isolated DC / DC circuit 2 is implemented using three-phase bridge arms, the secondary power switches can be driven and controlled by staggering the bridge arms by 120 degrees. The preset initial duty cycle is a relatively small duty cycle value. This application does not make any special restrictions on the specific value and implementation method of the preset initial duty cycle. As long as it is a duty cycle value greater than 0 and less than 50%, it is acceptable. A preferred embodiment is to use a duty cycle value that is relatively small compared to the duty cycle threshold, such as about 10% or less than 10%.

[0022] S12: Controls the duty cycle of the secondary power switch to increase from the preset initial duty cycle to the duty cycle threshold. Understandably, to reduce the inrush current during startup of the isolated DC / DC circuit 2 and prevent overshoot in the charging voltage output to the DC bus capacitor Cbus, this application employs a soft-start strategy by designing a relatively small preset initial duty cycle and gradually increasing the duty cycle of the secondary power switch. The gradual increase in the duty cycle of the secondary power switch limits the rate of increase of the resonant current in the resonant cavity and causes the charging voltage output to the DC bus capacitor Cbus to rise slowly and gradually, effectively avoiding overcurrent and overvoltage. This achieves a soft-start for the isolated DC / DC circuit 2, preventing significant oscillations in the resonant current during startup and ensuring a smooth rise in the charging voltage output to the DC bus capacitor Cbus, thus guaranteeing safety.

[0023] It should be noted that, to avoid shoot-through short circuits in the bridge arms, the two secondary power switches in the same bridge arm must conduct complementaryly. For any secondary power switch, its duty cycle can only reach or be close to 50%. Therefore, when controlling the gradual increase of the duty cycle of the secondary power switch, a duty cycle threshold needs to be designed to ensure that the duty cycle can only rise to this threshold, thus preventing bridge arm shoot-through caused by the duty cycle exceeding 50%. This application does not impose specific limitations on the specific value and implementation method of the duty cycle threshold; the duty cycle threshold only needs to be greater than the preset initial duty cycle and be a duty cycle value less than or equal to 50%. A preferred embodiment is to configure the duty cycle threshold to 50%, or a value less than 50% but close to 50%, to provide sufficient time for the soft start of the isolated DC / DC circuit 2. The specific strategy for increasing the duty cycle of the secondary power switch can be set and adjusted according to actual conditions, and this application does not impose specific limitations here.

[0024] S13: After the duty cycle of the secondary power switch reaches the duty cycle threshold, the switching frequency of the secondary power switch is reduced to charge the DC bus capacitor Cbus based on the power battery's electrical energy. It's easy to understand that, in order to reduce current and voltage ripple and achieve smooth startup of the isolated DC / DC circuit 2, a very high initial switching frequency is used to control the operation of the secondary power switch during soft-start. A higher initial switching frequency results in smaller and more continuous resonant current ripple during startup, and a smoother rise in the output charging voltage. However, once the duty cycle of the secondary power switch reaches the duty cycle threshold, the isolated DC / DC circuit 2 continues to operate stably according to this threshold. The battery discharges stably to charge the DC bus capacitor Cbus. At this point, the high switching frequency causes significant switching losses in the operation of the secondary power switch. When the battery power is low, these switching losses severely affect the pre-charging effect of the DC bus capacitor Cbus.

[0025] Therefore, after the duty cycle of the secondary power switch reaches the duty cycle threshold, the duty cycle of the secondary power switch will remain at the duty cycle threshold. At this time, further control of the switching frequency of the secondary power switch is introduced. By controlling the switching frequency of the secondary power switch to gradually decrease from a higher initial switching frequency, the switching losses in the circuit are gradually reduced, the energy output to the DC bus capacitor Cbus through the isolated DC / DC circuit 2 is increased, and the voltage gain of the charging voltage output to the DC bus capacitor Cbus by the isolated DC / DC circuit 2 is improved.

[0026] It should be noted that battery energy is transferred to the resonant cavity of the isolated DC / DC circuit 2 through the alternately conducting secondary power switches, and then sequentially through the resonant cavity and the parasitic diodes of the primary power switches to the two ends of the DC bus capacitor Cbus, thereby charging the DC bus capacitor Cbus. During the soft-start process of the isolated DC / DC circuit 2 in steps S11 and S12, battery energy also charges the DC bus capacitor Cbus. However, compared to the primary charging process in step S13, the process in step S13 is the main charging process for the DC bus capacitor Cbus. At this time, by reducing the switching frequency, sufficient energy can be provided to charge the DC bus capacitor Cbus, achieving rapid charging of the DC bus capacitor Cbus. This application does not impose any special limitations on the initial switching frequency and the specific strategy for reducing the switching frequency.

[0027] S14: If the charging process reaches the preset end condition, the secondary power switch is controlled to stop operating to complete the pre-charging of the DC bus capacitor Cbus.

[0028] It is understandable that after the charging process of the DC bus capacitor Cbus reaches the preset end condition, the reverse transfer of battery energy to the DC bus capacitor Cbus can be stopped by controlling the secondary power switch to stop operating, thus completing the pre-charging of the DC bus capacitor Cbus. The preset end condition is a pre-set pre-charging end flag. This application does not specifically limit the specific implementation method of the preset end condition. It can be set according to the pre-charging requirements of the OBC for the DC bus capacitor Cbus in actual applications, such as voltage requirements or pre-charging time requirements. Specifically, the bus voltage across the DC bus capacitor Cbus, the duration of the charging process, or the duration after the switching frequency begins to decrease can be used as the basis for setting the preset end condition. The preset end condition needs to be set in conjunction with the initial switching frequency and the switching frequency reduction strategy. Before the switching frequency of the secondary power switch decreases to 0, the charging process of the DC bus capacitor Cbus will definitely reach the set preset end condition first.

[0029] It should be noted that the pre-charging process of the DC bus capacitor Cbus, implemented by the control method of the on-board charger provided in this application (including steps S11 to S14), is performed before the OBC is powered on and begins normal forward operation. During the entire pre-charging process, the isolated DC / DC circuit 2 operates in an open-loop control mode, only working according to the duty cycle and / or switching frequency configured in the software. The control method for the secondary power switch and the corresponding adjustment methods for the duty cycle and switching frequency can be selected according to the actual application. This can be achieved directly through software configuration of the registers of the driver chip for the secondary power switch; this application does not impose any special limitations on this. Controlling the operation of the secondary power switch can be achieved directly by controlling the driver chip of the secondary power switch to output the corresponding drive signal; this application does not impose any special limitations on this. Controlling the secondary power switch to stop operation can be achieved directly by controlling the driver chip of the secondary power switch to stop outputting the drive signal; this application does not impose any special limitations on this.

[0030] It should be further noted that this application does not impose any special limitations on the specific structure and implementation method of the OBC, including but not limited to the PFC circuit 1, DC bus capacitor Cbus, and isolated DC / DC circuit 2 of this embodiment. Other circuit modules such as AC input ports, control units, low-voltage auxiliary units, and DC output ports can be set according to actual needs. This application does not impose any special limitations on the specific types and implementation methods of the PFC circuit 1, DC bus capacitor Cbus, and isolated DC / DC circuit 2. The control method of the on-board charger provided in this application can directly reuse the control unit configured in the OBC itself, or it can be implemented by setting up a separate control unit. Specifically, it can be implemented using various methods such as processors and controllers, and this application does not impose any special limitations on these methods.

[0031] It should be further explained that after the on-board charger control method provided in this application completes the pre-charging of the DC bus capacitor Cbus, the OBC can enter the normal forward charging mode. The AC power output is rectified by the PFC circuit 1, then converted to DC by the isolated DC / DC circuit 2, and finally output to the power battery to achieve normal charging of the vehicle's power battery. This application does not specifically limit the specific control strategy for the OBC during normal operation.

[0032] As one specific embodiment, see Figure 3 As shown, Figure 3 This invention provides a schematic diagram of the specific circuit structure of an on-board charger; Figure 3An isolated DC / DC circuit based on a three-phase CLLC topology and the circuit structure of the entire OBC are provided. The AC power output from the AC power supply (corresponding to live wires LINE1, LINE2, LINE3, and neutral wire N1) is connected to the input side of the OBC. The OBC includes a PFC circuit 1, a DC bus capacitor Cbus, and an isolated DC / DC circuit 2. The output side of the OBC is connected to the two ends of the power battery (positive terminal HV+ and negative terminal HV-). The OBC also includes relays K1, K2, K3, and K4 on the input side, and relays K5 and K6 and inductor L0 positioned between the PFC circuit 1 and the isolated DC / DC circuit 2. Capacitors C1, C2, and C3 are also provided for filtering on the OBC input side. The AC side of the PFC circuit 1 uses an LC structure composed of capacitors C4, C5, C6, C7, C8, C9, inductors La, Lb, and Lc for further filtering. PFC circuit 1 uses power switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 to achieve rectification. The DC bus capacitor Cbus specifically includes capacitors CBup and CBdn. Isolated DC / DC circuit 2 includes primary-side power switches S1, S2, S3, S4, S5, and S6, a resonant cavity, and secondary-side power switches S7, S8, S9, S10, S11, and S12. The resonant cavity specifically includes capacitors Crp1, Crp2, and Crp3; inductors Lrp1, Lrp2, and Lrp3; transformers Tr1, Tr2, and Tr3; inductors Lrs1, Lrs2, and Lrs3; and capacitors Crs1, Crs2, and Crs3. The isolated DC / DC circuit 2 also includes a parallel capacitor C0 located on the output side.

[0033] based on Figure 3 The OBC topology shown executes the control method of the on-board charger provided in this application. See [link to relevant documentation]. Figure 4 As shown, Figure 4This is a schematic diagram of the control flow of a vehicle-mounted charger control method provided by the present invention; taking a preset initial duty cycle of 10% and a duty cycle threshold of 50% as an example. After the OBC receives the charging start command, it first controls the subsequent isolated DC / DC circuit 2 to operate in open loop to pre-charge the DC bus capacitor Cbus (including the series capacitors CBup and CBdn). Specifically, the drive signal of the secondary power switch in the isolated DC / DC circuit 2 is first initialized and configured, and the duty cycle of the drive signal is configured to a preset initial duty cycle (e.g., 10%). Then, the drive signal of the secondary power switch in the isolated DC / DC circuit 2 is enabled, driving the secondary power switches S7, S8, S9, S10, S11 and S12 in the isolated DC / DC circuit 2. S12 operates with a small duty cycle of 10%, where secondary power switches S7 and S8 conduct complementaryly, S9 and S10 conduct complementaryly, and S11 and S12 conduct complementaryly. Furthermore, secondary power switches S7, S9, and S11 are alternately conducted at 120-degree intervals. The duty cycle of each secondary power switch is then gradually increased to 50%. Subsequently, the switching frequency of each secondary power switch is slowly reduced from a high frequency until the voltage across the DC bus capacitor Cbus (between B+ and B- terminals), i.e., the DC bus voltage (BUS voltage), reaches the preset pre-charge voltage, at which point the driving of the secondary power switches is stopped, completing the entire pre-charge process.

[0034] After pre-charging is completed, the OBC will enter the forward charging mode. At this time, the front-end PFC works normally to rectify. The primary-side power switches S1, S2, S3, S4, S5 and S6 in the rear-end drive isolated DC / DC circuit 2 constitute the primary circuit of the isolated DC / DC circuit 2. The secondary-side power switches S7, S8, S9, S10, S11 and S12 constitute the secondary circuit of the isolated DC / DC circuit 2. The primary and secondary sides rectify synchronously.

[0035] The control method for the on-board charger provided in this application can precharge the DC bus capacitor Cbus using the secondary circuit of the isolated DC / DC circuit 2 when the OBC is working normally. The precharging of the DC bus capacitor Cbus can be achieved simply by reusing the battery energy in the power battery and the secondary circuit of the isolated DC / DC circuit 2 of the OBC itself. The precharging of the DC bus capacitor Cbus can be achieved without the need for AC side input energy, thereby effectively avoiding the need to add a PTC (Positive Temperature Coefficient) circuit or other methods to the AC side of the OBC to achieve the precharging of the DC bus capacitor Cbus, simplifying the design of the OBC and its peripheral circuits, and saving the design and implementation costs of the OBC.

[0036] As an optional embodiment, it also includes: With the resonant current of the resonant cavity in the isolated DC / DC circuit 2 being less than or equal to a preset current threshold as a constraint, the rise time required for the duty cycle of the secondary power switch to linearly rise from the preset initial duty cycle to the duty cycle threshold is determined. Controlling the duty cycle of the secondary power switch to increase from a preset initial duty cycle to a duty cycle threshold includes: The duty cycle of the secondary power switch is controlled to rise linearly from the preset initial duty cycle to the duty cycle threshold during the rise time.

[0037] Understandably, to achieve a smooth soft start for the isolated DC / DC circuit 2 and minimize inrush current, the duty cycle of the secondary power switch can be gradually and uniformly controlled in a linear rise manner. Linear rise means controlling the duty cycle of the secondary power switch to rise from a preset initial duty cycle to a duty cycle threshold at a fixed slope. Simultaneously, to ensure safety, the rise time of the entire linear rise process can be determined in advance by using a constraint that the resonant current of the resonant cavity is less than or equal to a preset current threshold. This limits the rise rate of the duty cycle, allowing the resonant current to build up smoothly and linearly, effectively avoiding overcurrent during startup. Therefore, ultimately, it is only necessary to control the duty cycle of the secondary power switch to gradually update it in a linear rise manner within the determined rise time, causing it to gradually rise to the duty cycle threshold.

[0038] It should be noted that this application does not impose any special limitations on the specific method for determining the rise time. It can be determined through experimental testing or theoretical calculation based on the actual topology of the isolated DC / DC circuit 2. Similarly, this application does not impose any special limitations on the specific value of the preset current threshold. It can be set according to the actual circuit topology. The resonant current of the resonant cavity in the isolated DC / DC circuit 2 refers to the current flowing through the series resonant branch (e.g., the resonant inductor) in the resonant cavity. This application does not impose any special limitations on the specific method for determining the resonant current of the resonant cavity in the isolated DC / DC circuit 2. It can be achieved by sampling using a current sensor, or by sampling the resonant current of the primary side and / or the secondary side of the resonant cavity. A preferred embodiment is to sample the resonant current of the primary side of the resonant cavity. Figure 3 Taking the OBC topology shown as an example, the resonant cavity includes a three-phase CLLC topology. In this case, the resonant current of each of the three phases can be sampled separately, for example, as shown in the figure. Figure 3 As shown, the inductor currents flowing through inductors Lrp1, Lrp2, and Lrp3 are sampled respectively, and the maximum value among the three inductor currents is taken as the final resonant current sampling result.

[0039] Specifically, by pre-determining the rise time of the duty cycle rise process under the constraint that the resonant current of the resonant cavity in the isolated DC / DC circuit 2 is less than or equal to a preset current threshold, the rise slope of the duty cycle is effectively limited to ensure safety. At the same time, based on the determined rise time, the duty cycle is controlled to rise gradually in a linear manner, effectively realizing the smooth start-up of the isolated DC / DC circuit 2.

[0040] As an optional embodiment, controlling the switching frequency of the secondary power switch to decrease includes: Determine the real-time switching frequency of the secondary power switch; Based on the relationship between the real-time switching frequency and the preset frequency range, the switching frequency of the secondary power switch is controlled to decrease according to the preset step size corresponding to the preset frequency range. The preset step size is positively correlated with the frequency corresponding to the preset frequency range; the correspondence between the preset frequency range and the preset step size is determined in advance based on the gain curve of the isolated DC / DC circuit 2.

[0041] It is easy to understand that the specific step size for reducing the switching frequency can be determined in advance based on the gain curve of the isolated DC / DC circuit 2. The gain curve of the isolated DC / DC circuit 2 characterizes the relationship between the voltage gain of the isolated DC / DC circuit 2 and the switching frequency of the secondary power switch. Therefore, based on the gain curve of the isolated DC / DC circuit 2, combined with its specific topology, component parameters, and design constraints, a suitable step size for reducing the switching frequency can be determined. Specifically, the design constraint can be to keep the voltage gain of the isolated DC / DC circuit 2 within a suitable range; that is, to determine the preset step size based on keeping the voltage gain of the isolated DC / DC circuit 2 within a suitable range. Considering that the range of switching frequency variation is also limited at different frequency levels, several preset frequency ranges can be set in advance. Then, for each preset frequency range, a corresponding preset step size can be determined based on the gain curve of the isolated DC / DC circuit 2. The switching frequency is reduced according to the adjustment speed corresponding to the gain range at different frequency levels.

[0042] It should be noted that the preset frequency range refers to a pre-set upper and lower limit range for the normal operation of the switching frequency. This application does not specifically limit the specific division method of the preset frequency range or the corresponding upper and lower limit values; similarly, this application does not specifically limit the specific implementation method of the preset step size. Generally speaking, the size of the preset step size is positively correlated with the frequency size corresponding to the preset frequency range. The frequency size corresponding to the preset frequency range refers to the upper or lower limit frequency size of the preset frequency range. That is, as the real-time switching frequency of the secondary power switch decreases, its corresponding decreasing rate and the specific decreasing step size will also decrease. For example, for three preset frequency ranges (f1,f2), (f2,f3), and (f3,f4), where f1 < f2 < f3 < f4, the step size corresponding to the preset frequency range (f1,f2) is A, the step size corresponding to the preset frequency range (f2,f3) is B, and the step size corresponding to the preset frequency range (f3,f4) is C, then A < B < C.

[0043] Specifically, by configuring different preset frequency ranges and corresponding preset step sizes, when the control switching frequency decreases, the specific step size and speed of its reduction can be adjusted according to the real-time magnitude of the switching frequency, so that the voltage gain of the isolated DC / DC circuit 2 can always be kept at a suitable level, ensuring the charging speed of the DC bus capacitor Cbus.

[0044] As an optional embodiment, it also includes: Determine the bus voltage across the DC bus capacitor Cbus; Based on the relationship between the bus voltage across the DC bus capacitor Cbus and the preset pre-charge voltage, it is determined whether the charging process has reached the preset termination condition.

[0045] It is understandable that the bus voltage across the DC bus capacitor Cbus will gradually increase as the charging process progresses. Furthermore, in practical applications, OBCs typically have specific requirements for the bus voltage across the DC bus capacitor Cbus. Therefore, the bus voltage across the DC bus capacitor Cbus can be used as the basis for determining whether the charging process can end. Specifically, a preset pre-charge voltage can be set as a reference. The voltage relationship between the bus voltage across the DC bus capacitor Cbus and the preset pre-charge voltage is used as the preset termination condition. The comparison of the two voltages determines whether the preset termination condition has been met, i.e., whether the pre-charging process can be terminated. This application does not specifically limit the specific value and implementation method of the preset pre-charge voltage. It can be set by issuing commands, etc., and the specific value can be determined according to the actual usage requirements of the OBC or the actual circuit design of the OBC. For example, the value of the preset pre-charge voltage can be determined based on the relationship between the bus voltage required for the forward charging condition of the OBC during normal operation and the voltage across the power battery, including but not limited to the loss requirements, efficiency requirements, and gain requirements during the forward charging condition.

[0046] Specifically, the pre-charging can be terminated based on the bus voltage across the DC bus capacitor Cbus, ensuring that the bus voltage across the DC bus capacitor Cbus meets the bus voltage requirements for normal OBC operation, thus guaranteeing the normal operation of OBC.

[0047] As an optional embodiment, the determination of whether the charging process has reached the preset termination condition is based on the relationship between the bus voltage across the DC bus capacitor Cbus and the preset pre-charge voltage, including: Determine whether the bus voltage across the DC bus capacitor Cbus is continuously greater than the preset pre-charge voltage within a preset time period; If so, the charging process is determined to have reached the preset termination condition; If not, it is determined that the charging process has not reached the preset termination condition.

[0048] It is easy to understand that, in order to ensure that the bus voltage across the DC bus capacitor Cbus stably reaches the preset pre-charge voltage before ending the charging process, the charging process will only be considered to have reached the preset termination condition if the bus voltage across the DC bus capacitor Cbus is continuously greater than the preset pre-charge voltage for a preset time period. Charging will not end if the bus voltage across the DC bus capacitor Cbus does not reach the preset pre-charge voltage or only briefly reaches it. The specific value of the preset time period can be set and adjusted according to the actual application, and this application does not impose any special limitations on it; it can be 1ms, etc. The specific method for determining the bus voltage across the DC bus capacitor Cbus is not particularly limited here; it can be obtained using hardware circuits such as voltage sensors. The detection frequency of the bus voltage across the DC bus capacitor Cbus is not particularly limited here; it can be detected and judged in real time, or it can be detected and judged periodically according to a specific cycle.

[0049] Specifically, the bus voltage across the DC bus capacitor Cbus is determined to be stable at the preset pre-charge voltage by continuously exceeding this judgment condition within a preset time period. This determines whether the charging process has reached the preset end condition, avoiding misjudgments caused by momentary and brief attainment, and improving the accuracy of the judgment. The bus voltage of the DC bus capacitor Cbus at the end of charging is in a steady state that has effectively reached the preset pre-charge voltage, effectively ensuring the normal operation of the OBC.

[0050] As an optional embodiment, it also includes: Detect the resonant current of the resonant cavity in the isolated DC / DC circuit 2; If the resonant current exceeds the current protection threshold, the secondary power switch will be controlled to stop operating.

[0051] It is understandable that, in order to improve the safety of the pre-charging process, corresponding protection strategies can be further set for the pre-charging process. This embodiment provides a specific overcurrent protection strategy for potential overcurrent during the pre-charging process. Throughout the pre-charging process, the overcurrent protection strategy provided in this embodiment is run. By detecting the resonant current of the resonant cavity in the isolated DC / DC circuit 2 and comparing the detected resonant current with a preset current protection threshold, the secondary power switch is promptly controlled to stop operating when the resonant current exceeds the current protection threshold to protect the safety of the OBC and the power battery. This ensures that no overcurrent occurs during the pre-charging process and avoids damage to the power switch and DC bus capacitor Cbus in the isolated DC / DC circuit 2 due to circuit faults or other reasons.

[0052] It should be noted that this application does not impose any special limitations on the specific value and implementation method of the current protection threshold, which can be set and adjusted according to the actual situation. Similarly, this application does not impose any special limitations on the specific determination method and detection frequency of the resonant current of the resonant cavity in the isolated DC / DC circuit 2. The resonant current of the resonant cavity in the isolated DC / DC circuit 2 can be detected and judged in real time, or it can be detected and judged periodically according to a specific cycle. Other methods can also be used to implement protection, not limited to the protection method of controlling the secondary power switch to stop operating; this application does not impose any special limitations on these methods.

[0053] Specifically, by adding an overcurrent protection strategy, overcurrent protection during the pre-charging process is effectively achieved, ensuring that the current output from the power battery, flowing through the isolated DC / DC circuit 2, and output to the DC bus capacitor Cbus will not be too high, thus ensuring the safety and reliability of the pre-charging process.

[0054] As an optional embodiment, it also includes: Detect the bus voltage across the DC bus capacitor Cbus; If the bus voltage across the DC bus capacitor Cbus exceeds the voltage protection threshold, the secondary power switch will be stopped.

[0055] It is easy to understand that this embodiment provides a specific overvoltage protection strategy for potential overvoltage during the pre-charging process. Throughout the pre-charging process, the overvoltage protection strategy provided in this embodiment is run. By detecting the bus voltage across the DC bus capacitor Cbus and comparing the detected bus voltage with a preset voltage protection threshold, the secondary power switch is promptly controlled to stop operating when the bus voltage exceeds the voltage protection threshold to protect the safety of the OBC and the power battery. This ensures that no overvoltage occurs during the pre-charging process and avoids damage to the power switch and DC bus capacitor Cbus in the isolated DC / DC circuit 2 due to circuit faults or other reasons.

[0056] It should be noted that this application does not impose any special limitations on the specific value and implementation method of the voltage protection threshold, which can be set and adjusted according to the actual situation. Similarly, this application does not impose any special limitations on the specific determination method and detection frequency of the bus voltage across the DC bus capacitor Cbus. The bus voltage across the DC bus capacitor Cbus can be detected and judged in real time, or it can be detected and judged periodically according to a specific cycle. Other methods can also be used to implement protection, not limited to the protection method of controlling the secondary power switch to stop operating; this application does not impose any special limitations on this. The overvoltage protection strategy of this embodiment can operate simultaneously with the overcurrent protection strategy of the above embodiments, or it can operate selectively according to application requirements; this application does not impose any special limitations on this.

[0057] Specifically, by adding an overvoltage protection strategy, overvoltage protection during the pre-charging process is effectively achieved, ensuring that the charging voltage at both ends of the power battery, the input and output ends of the isolated DC / DC circuit 2, and the output to the DC bus capacitor Cbus will not be too high, thus ensuring the safety and reliability of the pre-charging process.

[0058] See Figure 5 As shown, Figure 5 This is a schematic diagram of the structure of an electronic device provided by the present invention. To solve the above-mentioned technical problems, the present invention also provides an electronic device, comprising: Memory 21 is used to store computer program 212; The processor 22 is used to implement the steps of the control method for the on-board charger as described above.

[0059] The processor 22 may include one or more processing cores, such as a quad-core processor or an octa-core processor. The processor 22 may be implemented using at least one of the following hardware forms: DSP (Digital Signal Processor), FPGA (Field-Programmable Gate Array), or PLA (Programmable Logic Array). The processor may also include a main processor and a coprocessor. The main processor, also known as the central processing unit, is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state.

[0060] The memory 21 may include one or more computer-readable storage media, which may be non-transitory. The memory 21 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In this embodiment, the memory 21 is used to store at least the following computer program 212, which, after being loaded and executed by the processor 22, can implement the relevant steps of the on-board charger control method disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 21 may also include an operating system 211 and data, and the storage method may be temporary or permanent storage. The operating system 211 may include Windows, Unix, Linux, etc. The data may include, but is not limited to, the data in the on-board charger control method.

[0061] In some embodiments, the electronic device may further include a display screen, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. Those skilled in the art will understand that... Figure 5 The illustration does not constitute a limitation on the electronic device and may include more or fewer components than shown.

[0062] For an introduction to the electronic device provided by the present invention, please refer to the embodiment of the control method for the on-board charger described above; the present invention will not be repeated here.

[0063] To address the aforementioned technical problems, the present invention also provides an on-board charging system, including an on-board charger and an electronic device as described above, wherein the electronic device is connected to the on-board charger.

[0064] It is easy to understand that electronic devices can be connected to an on-board charger to form an on-board charging system. The electronic devices execute the control method of the on-board charger to pre-charge the DC bus capacitor in the on-board charger before the on-board charger is powered on and begins normal forward operation, and then the on-board charger is officially powered on and begins normal forward operation. This application does not make any special limitations on the specific type of on-board charger or its implementation method.

[0065] For an introduction to the on-board charging system provided by this invention, please refer to the embodiments of the control method for the on-board charger described above. This invention will not be repeated here.

[0066] To address the aforementioned technical problems, the present invention also provides a vehicle, including a power battery and an on-board charging system as described above, wherein the on-board charging system is connected to the power battery.

[0067] It is understood that on-board charging systems can be applied to vehicles, especially new energy vehicles (such as electric vehicles). The on-board charging system is connected to the power battery. Once the on-board charger in the on-board charging system is powered on and working normally, it can charge the vehicle's power battery through the AC power source connected to the on-board charger. This application does not impose any special limitations on the specific types of power batteries and vehicles, or on the implementation methods. In addition to the on-board charging system, the vehicle can also be further equipped with on-board DC / DC converters, PDUs (Power Distribution Units), such as high-voltage distribution boxes, etc., which are not specifically limited here.

[0068] For an introduction to the vehicle provided by this invention, please refer to the embodiment of the control method for the on-board charger described above; the invention will not be repeated here.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section. It should also be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for an on-board charger, the on-board charger comprising a PFC circuit, a DC bus capacitor, and an isolated DC / DC circuit, wherein the DC side of the PFC circuit and the first DC side of the isolated DC / DC circuit are both connected in parallel with the DC bus capacitor, and the second DC side of the isolated DC / DC circuit is connected to a power battery; characterized in that, The control method for the on-board charger includes: The secondary power switches in the isolated DC / DC circuit are controlled to operate according to a preset initial duty cycle; wherein, the two secondary power switches in the same bridge arm are complementary in conduction. The duty cycle of the secondary power switch is controlled to increase from the preset initial duty cycle to the duty cycle threshold. After the duty cycle of the secondary power switch reaches the duty cycle threshold, the switching frequency of the secondary power switch is reduced to charge the DC bus capacitor based on the power battery's electrical energy. If the charging process reaches the preset end condition, the secondary power switch is controlled to stop operating to complete the pre-charging of the DC bus capacitor.

2. The control method for the on-board charger according to claim 1, characterized in that, Also includes: With the resonant current of the resonant cavity in the isolated DC / DC circuit being less than or equal to a preset current threshold as a constraint, the rise time required for the duty cycle of the secondary power switch to linearly increase from the preset initial duty cycle to the duty cycle threshold is determined. Controlling the duty cycle of the secondary power switch to increase from the preset initial duty cycle to the duty cycle threshold includes: The duty cycle of the secondary power switch is controlled to linearly increase from the preset initial duty cycle to the duty cycle threshold within the rise time.

3. The control method for the on-board charger according to claim 1, characterized in that, Controlling the reduction of the switching frequency of the secondary-side power switch includes: Determine the real-time switching frequency of the secondary power switch; Based on the relationship between the real-time switching frequency and the preset frequency range, the switching frequency of the secondary power switch is controlled to decrease according to the preset step size corresponding to the preset frequency range. The preset step size is positively correlated with the frequency corresponding to the preset frequency range; the correspondence between the preset frequency range and the preset step size is determined in advance based on the gain curve of the isolated DC / DC circuit.

4. The control method for the on-board charger according to claim 1, characterized in that, Also includes: Determine the bus voltage across the DC bus capacitor; Based on the relationship between the bus voltage across the DC bus capacitor and the preset pre-charge voltage, it is determined whether the charging process has reached the preset termination condition.

5. The control method for the on-board charger according to claim 4, characterized in that, Based on the relationship between the bus voltage across the DC bus capacitor and the preset pre-charge voltage, determine whether the charging process has reached the preset termination condition, including: Determine whether the bus voltage across the DC bus capacitor is continuously greater than the preset pre-charge voltage within a preset time period; If so, the charging process is determined to have reached the preset termination condition; If not, it is determined that the charging process has not reached the preset termination condition.

6. The control method for an on-board charger according to any one of claims 1 to 5, characterized in that, Also includes: Detect the resonant current of the resonant cavity in the isolated DC / DC circuit; If the resonant current exceeds the current protection threshold, the secondary power switch will be controlled to stop operating.

7. The control method for an on-board charger according to any one of claims 1 to 5, characterized in that, Also includes: Detect the bus voltage across the DC bus capacitor; If the bus voltage across the DC bus capacitor exceeds the voltage protection threshold, the secondary power switch will be controlled to stop operating.

8. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor for implementing the steps of the control method for an on-board charger as described in any one of claims 1 to 7.

9. An on-board charging system, characterized in that, It includes an on-board charger and an electronic device as described in claim 8, wherein the electronic device is connected to the on-board charger.

10. A vehicle, characterized in that, It includes a power battery and an on-board charging system as described in claim 9, wherein the on-board charging system is connected to the power battery.

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