Charging circuit for battery module of electric vehicle

Abstract

The present invention relates to a charging circuit of a battery module applied to an electric vehicle, and to a power conversion device. By adopting a buck-boost DC conversion module after an isolation conversion module, and controlling the buck-boost DC conversion module to sequentially operate in a Buck operating mode including a first operating stage and a second operating stage located thereafter, and a Boost operating mode including a third operating stage and a fourth operating stage located thereafter, and correspondingly controlling the output first bus voltage Vbus1, the rated output voltage Vbus2 greater than the first bus voltage Vbus1, the first bus voltage Vbus1, and the rated output voltage Vbus2 greater than the first bus voltage Vbus1 of the isolation conversion module, high-precision output of the buck-boost DC conversion module within the full voltage range is achieved, and an isolation conversion module with a lower rated output voltage can be selected, thereby increasing the market selection space for devices in the isolation conversion module, and making it easier to select devices with both excellent performance and price.

Description

Technical Field

[0001] The present invention relates to a power conversion device, and in particular to a charging circuit for a battery module applied to an electric vehicle. Background Art

[0002] Electric vehicles, with their remarkable features of high efficiency, energy saving, low noise and zero emission, have incomparable advantages in energy saving and environmental protection. In recent years, major progress has been made in the core key technologies of electric vehicle power batteries, motors, control systems, on-board chargers, etc., and product safety, reliability and life have been significantly improved. The cost has also been controlled to a certain extent. Hybrid vehicles and pure electric vehicles are gradually entering the stage of practical application and small industrialization. Electric vehicles will become the strategic direction of the development of the world's automobile industry.

[0003] Electric vehicles have built-in high-voltage batteries, which are one of the key components of electric vehicles as a stable energy source for providing power. The built-in high-voltage battery is usually formed by multiple battery modules connected in series and parallel. In this way, when any battery module fails or needs later maintenance, the battery module that needs maintenance can be taken out at will for maintenance, and after it is charged by the charging and discharging circuit, it is connected in series and parallel with other battery modules in the electric vehicle. In order to avoid the voltage difference between it and other battery modules causing the capacity of the high-voltage battery to be affected after the series and parallel connection, the voltage accuracy of the battery module being maintained is required to be high, at least within 50mV. Therefore, the DC side output voltage of the charging and discharging circuit for charging and discharging the battery module is also required to have the same high accuracy, and it is hoped that the charging circuit of the battery module has high efficiency, good compatibility and low cost.

[0004] See also Figure 1 , Figure 1 The block diagram of the charging circuit of the existing battery module used in electric vehicles is shown in FIG. Figure 1 As shown, the charging circuit of the battery module applied to the electric vehicle includes an isolation conversion module 110, whose input end is connected to the AC power source 120 (such as the AC power grid), receives an AC input voltage Vac, converts the AC input voltage Vac into a bus voltage Vbus at its output end, and provides isolation between its input end and output end; a step-down DC module 130, whose input end is connected to the output end of the isolation conversion module 110, receives the bus voltage Vbus, converts the bus voltage Vbus into a DC output voltage Vdc to charge the battery module 140. In addition, the charging circuit of the battery module applied to the electric vehicle also includes an AC protection control circuit 150 connected between the AC power source 120 and the isolation conversion module 110, and a protection / pre-charging circuit 160 connected between the step-down DC module 130 and the battery module 140.

[0005] In the prior art, the step-down DC module 130 is usually implemented by a buck step-down circuit, which converts a stable bus voltage Vbus into a DC output voltage Vdc. Figure 2 , Figure 2 FIG. 1 is a schematic diagram of a duty cycle variation curve of a step-down DC module in the prior art. Figure 2 As shown, under the stable input bus voltage Vbus, the DC output voltage Vdc of the step-down DC module 130 increases with the duty cycle Duty. The voltage level range of the battery module is relatively wide, and the current electric vehicle manufacturers have continuously increased the voltage level requirements of the battery module, from 20V, 40V to 60V, 80V, 100V, and are currently developing towards 150V, 160V or even 170V or higher. Therefore, the DC output voltage Vdc of the charging circuit for charging it is also required to have a wide range.

[0006] In order to meet the voltage range of the DC output voltage Vdc of the step-down DC module 130, the bus voltage Vbus is required to be higher than the maximum value of the DC output voltage Vdc, that is, the voltage level of the bus voltage Vbus is required to be higher. For example, if the voltage range of the DC output voltage Vdc is 0V to 120V, the output bus voltage Vbus of the isolation conversion module 110 is required to be 140V. First, for the isolation conversion module 110 with a higher output voltage level, the market selection space of its internal components is limited and the cost is also high. For example, the switch elements with a withstand voltage of 200V are more in the market and the price is cheap, while the market selection space of the switch elements with a withstand voltage of 300V or above is greatly reduced and the price is more expensive. In addition, the isolation conversion module 110 is a front-stage isolation module connected to the power grid, and its requirements for safety regulations, EMC, etc. are very strict. Therefore, its design or modification difficulty and cycle are relatively large compared to the subsequent step-down DC module 130. In order to meet the battery module with a wide voltage range, redesigning the isolation conversion module 110 brings great pressure to the designer.

[0007] Furthermore, for battery modules with a larger voltage range, a higher voltage level of the bus voltage Vbus is required, and the duty cycle of the step-down DC module 130 varies greatly, which makes it difficult to achieve high precision within the full voltage range, and the range of poor precision is also larger. For example, if an isolation conversion module 110 with an output bus voltage Vbus of 140V is used to power a step-down DC module 130 with a DC output voltage Vdc in the range of 0V to 120V, then the precision is poor in the range of, for example, the DC output voltage Vdc from 0V to 20V; and in the area where the duty cycle is generally less than, for example, 10%, it is a small duty cycle low efficiency area, that is, in the area where the DC output voltage Vdc is 0V to 14V, it is a low efficiency area, and the range of the low efficiency area is relatively wide.

[0008] Therefore, designing a charging circuit for the battery module of an electric vehicle that can meet the needs of the battery module with a wide voltage range, be simple in design and low in cost, and can also meet the high-precision requirements of the battery module, and can increase the high-precision voltage range of its output voltage and improve efficiency has become a research direction in the industry. Summary of the invention

[0009] The charging circuit of the battery module of the electric vehicle provided by the present invention comprises: an isolation conversion module, whose input end is connected to an AC power supply, receives an AC input voltage, converts the AC input voltage Vac into a bus voltage Vbus at its output end, and provides isolation between its output end and input end, wherein the bus voltage Vbus comprises a rated output voltage value Vbus2 of the isolation conversion module and a first bus voltage value Vbus1 which is smaller than the rated output voltage value Vbus2; a buck-boost DC module, comprising at least one switch element, whose input end is connected to the output end of the isolation conversion module, receives the bus voltage Vbus, and converts the bus voltage Vbus into a DC output voltage Vdc; a battery module, connected to The control circuit receives a detection signal Ssense, and outputs a first control signal Cctr1 to the buck-boost DC module and a second control signal Cctr2 to the isolation conversion module according to the detection signal Ssense, wherein the first control signal Cctr1 controls the buck-boost DC module to first operate in the Buck operating mode and then switch to the Boost operating mode, and in the Buck operating mode, first operates in the first operating stage and then switches to the second operating stage, and in the Boost operating mode, first operates in the third operating stage and then switches to the fourth operating stage, and the second control signal Cctr2 controls the buck-boost DC module to first operate in the Buck operating mode and then switches to the second operating stage. The signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1 or the rated output voltage value Vbus2, wherein, in the first working stage, the second control signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1, the first control signal Cctr1 controls the duty cycle of the buck-boost DC module to gradually increase, and the DC output voltage Vdc of the buck-boost DC module gradually increases, and in the second working stage, the second control signal Cctr2 controls the isolation conversion module to output the rated output voltage value Vbus2, the first control signal Cctr1 controls the duty cycle of the buck-boost DC module to decrease and then gradually increase, The DC output voltage Vdc of the buck-boost DC module gradually increases. In the third working stage, the second control signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1, and the first control signal Cctr1 controls the duty cycle of the buck-boost DC module to decrease, and the DC output voltage Vdc of the buck-boost DC module gradually increases. In the fourth working stage, the second control signal Cctr2 controls the isolation conversion module to output the rated output voltage value Vbus2, and the first control signal Cctr1 controls the duty cycle of the buck-boost DC module to increase and then gradually decrease, and the DC output voltage Vdc of the buck-boost DC module gradually increases.

[0010] Furthermore, a difference between the rated output voltage Vbus2 and the first bus voltage Vbus1 is less than or equal to 5% of the rated output voltage Vbus2.

[0011] Furthermore, the detection signal Ssense is a signal reflecting the working state of the buck-boost DC module, and the control circuit outputs the first control signal Cctr1 and the second control signal Cctr2 according to the detection signal Ssense.

[0012] Furthermore, the detection signal Ssense is a signal reflecting the DC output voltage Vdc of the buck-boost DC module.

[0013] Furthermore, when the power is turned on, the buck-boost DC module operates in the first working stage, when the DC output voltage Vdc reaches the first voltage value V1, the buck-boost DC module switches to the second working stage, when the DC output voltage Vdc reaches the second voltage value V2, the buck-boost DC module switches to the third working stage, and when the DC output voltage Vdc reaches the third voltage value V3, the buck-boost DC module switches to the fourth working stage, wherein the second voltage value V2 is greater than the first bus voltage Vbus1 and less than the rated output voltage Vbus2 of the isolation conversion module, the first voltage value V1 is less than the second voltage value V2, and the second voltage value V2 is less than the third voltage value V3.

[0014] Furthermore, the first voltage value V1, the second voltage value V2 and the third voltage value V3 are selected so that the buck-boost DC module does not enter a non-working region with a very large duty cycle.

[0015] Furthermore, the detection signal Ssense is a signal reflecting the duty cycle of the switch element of the buck-boost DC module.

[0016] Furthermore, when the power is turned on, the buck-boost DC module operates in the first working stage. When the duty cycle of the buck-boost DC module increases to the first predetermined value Dduty1, the buck-boost DC module switches to the second working stage of the Buck working mode. When the duty cycle of the buck-boost DC module further increases to the second predetermined value Dduty2, the buck-boost DC module switches to the third working stage of the Boost working mode. When the duty cycle of the buck-boost DC module decreases to the third predetermined value Dduty3, the buck-boost DC module switches to the fourth working stage of the Boost working mode.

[0017] Furthermore, the first predetermined value Dduty1, the second predetermined value Dduty2 and the third predetermined value Dduty3 are selected so that the buck-boost DC module 230 does not enter a non-working region with a very large duty cycle.

[0018] Furthermore, the first predetermined value Dduty1 is equal to the second predetermined value Dduty2.

[0019] Furthermore, the step-up / step-down DC module is a Buck / Boost converter.

[0020] Furthermore, the buck-boost DC module is a buck-boost DC module connected in staggered parallel.

[0021] Furthermore, the first control signal Cctr1 is a switch control signal, which is used to control the on or off of the switch element in the buck-boost DC module.

[0022] Furthermore, the second control signal Cctr2 is connected to the reference voltage circuit of the control circuit of the isolation conversion module, so that the reference voltage of the control circuit of the isolation conversion module changes according to the second control signal Cctr2, thereby controlling the bus voltage Vbus of the isolation conversion module to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2.

[0023] Furthermore, the isolation conversion module includes multiple isolation converters connected in parallel, and includes a current-sharing bus and a current-sharing control circuit connected to the current-sharing bus. The second control signal Cctr2 is output to the current-sharing control circuit, so that the current-sharing control circuit controls the bus voltage Vbus of the current-sharing bus to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2 according to the second control signal Cctr2.

[0024] Furthermore, the voltage range of the DC output voltage Vdc of the buck-boost DC module is 0V to a voltage greater than 48V.

[0025] Furthermore, it also includes an AC protection control circuit connected between the AC power supply and the isolation conversion module, and a protection / pre-charging circuit connected between the buck-boost DC module and the battery module.

[0026] Furthermore, the isolation conversion module and the buck-boost DC module are bidirectional conversion modules.

[0027] Furthermore, the control circuit includes an error amplifier, a PWM wave generator and a signal conversion unit, one input end of the error amplifier receives a detection signal Ssense, the other input end of the error amplifier receives a reference signal, and outputs an error signal, the PWM wave generator receives the error signal and generates the first control signal Cctr1 according to the error signal, and the signal conversion unit receives the error signal and generates the second control signal Cctr2 according to the error signal.

[0028] The charging circuit of the battery module of the electric vehicle of the present invention adopts a buck-boost DC conversion module after the isolation conversion module, and controls the buck-boost DC conversion module to work in sequence in a Buck working mode including a first working stage and a second working stage located thereafter, and a Boost working mode including a third working stage and a fourth working stage located thereafter, and correspondingly controls the output first bus voltage Vbus1, the rated output voltage Vbus2 greater than the first bus voltage Vbus1, the first bus voltage Vbus1, and the rated output voltage Vbus2 greater than the first bus voltage Vbus1 of the isolation conversion module, thereby realizing high-precision output of the buck-boost DC conversion module within the full voltage range, and being able to select an isolation conversion module with a lower rated output voltage, thereby increasing the market selection space for devices in the isolation conversion module, and making it easier to select devices with both excellent performance and price. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a block diagram of a charging circuit of a battery module currently used in electric vehicles.

[0030] Figure 2 The figure is a schematic diagram of a duty cycle variation curve of a step-down DC module in the prior art.

[0031] Figure 3 The figure is a block diagram of a charging circuit for a battery module of an electric vehicle according to an embodiment of the present invention.

[0032] Figure 4 It is a schematic diagram of a duty cycle variation curve of the buck-boost DC module of the present invention and a bus voltage Vbus variation curve output by the isolation conversion module.

[0033] Figure 5 FIG. 4 is a circuit diagram of a buck / boost converter according to an embodiment of the present invention.

[0034] Figure 6 FIG. 4 is a circuit diagram of an interleaved parallel buck / boost converter according to an embodiment of the present invention.

[0035] Figure 7 FIG. 4 is a block diagram of a control circuit according to an embodiment of the present invention.

[0036] The main components in the figure are described as follows:

[0037] 220, AC power supply; 250, AC protection control circuit; 210, isolation conversion module; 230, buck-boost DC module; 260, protection / pre-charge circuit; 240, battery module; 270, control circuit. DETAILED DESCRIPTION

[0038] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] In one embodiment of the present invention, a charging circuit for a battery module of an electric vehicle is provided. Figure 3 and Figure 4 , Figure 3 FIG. 1 is a block diagram of a charging circuit for a battery module of an electric vehicle according to an embodiment of the present invention. Figure 4 Schematic diagram of the duty cycle variation curve of the buck-boost DC module and the bus voltage Vbus variation curve output by the isolation conversion module of the present invention, as shown in FIG. Figure 3 and Figure 4As shown, a charging circuit for a battery module of an electric vehicle according to an embodiment of the present invention includes: an isolation conversion module 210, whose input end is connected to an AC power source 220 (such as an AC power grid), receives an AC input voltage Vac, converts the AC input voltage Vac into a bus voltage Vbus at its output end, and provides isolation between its output end and input end, wherein the bus voltage Vbus includes a rated output voltage value Vbus2 of the isolation conversion module 210 and a first bus voltage value Vbus1 that is smaller than the rated output voltage value Vbus2; a buck-boost DC module 230, including at least one switch element, whose input end is connected to the output end of the isolation conversion module 210, receives the bus voltage Vbus, and converts the bus voltage Vbus The battery module 240 is connected to the buck-boost DC module 230, and receives the DC output voltage Vdc to charge the battery module 240; the control circuit 270 receives a detection signal Ssense, and outputs a first control signal Cctr1 to the buck-boost DC module 230 and a second control signal Cctr2 to the isolation conversion module 210 according to the detection signal Ssense, wherein the first control signal Cctr1 controls the buck-boost DC module 230 to first work in the Buck working mode, and then switch to the Boost working mode, and in the Buck working mode, first work in the first working stage, and then switch to the second working stage, and in the Boost working mode, first work in the first working stage. The third working stage, and then switch to the fourth working stage, the second control signal Cctr2 controls the isolation conversion module 210 to output the first bus voltage value Vbus1 or the rated output voltage value Vbus2, wherein, in the first working stage, the second control signal Cctr2 controls the isolation conversion module 210 to output the first bus voltage value Vbus1, the first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to gradually increase, and the DC output voltage Vdc of the buck-boost DC module 230 gradually increases, and in the second working stage, the second control signal Cctr2 controls the isolation conversion module 210 to output the rated output voltage value Vbus2, and the first control signal Cctr1 controls the buck-boost DC module 230 The duty cycle of the buck-boost DC module 230 decreases and then gradually increases, and the DC output voltage Vdc of the buck-boost DC module 230 gradually increases. In the third working stage, the second control signal Cctr2 controls the isolation conversion module 210 to output the first bus voltage value Vbus1, and the first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to decrease, and the DC output voltage Vdc of the buck-boost DC module 230 gradually increases. In the fourth working stage, the second control signal Cctr2 controls the isolation conversion module 210 to output the rated output voltage value Vbus2, and the first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to increase and then gradually decrease, and the DC output voltage Vdc of the buck-boost DC module 230 gradually increases.

[0040] Specifically, Figure 4 As shown, after the buck-boost DC module 230 is turned on, the first control signal Cctr1 controls the buck-boost DC module 230 to work in the Buck working mode, and first works in the first working stage of the Buck working mode. At this time, the second control signal Cctr2 controls the isolation conversion module 210 to output the first bus voltage Vbus1. The first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to gradually increase, and the DC output voltage Vdc gradually increases with the duty cycle; when the DC output voltage Vdc reaches the first voltage value V1 or the duty cycle of the buck-boost DC module 230 When the duty cycle increases to the first predetermined value Dduty1, the second control signal Cctr2 controls the bus voltage Vbus output by the isolation conversion module 210 to increase from the first bus voltage Vbus1 to the rated output voltage Vbus2, then the duty cycle of the buck-boost DC module 230 decreases, and then the first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to gradually increase, then the DC output voltage Vdc gradually increases with the duty cycle, that is, it works in the second working stage of the Buck working mode; when the DC output voltage Vdc reaches the second voltage value V2 or the buck-boost DC module When the duty cycle of the step-up / down DC module 230 increases to the second predetermined value Dduty2, the first control signal Cctr1 controls the step-up / down DC module 230 to switch to the Boost working mode, and the second control signal Cctr2 controls the bus voltage Vbus output by the isolation conversion module 210 to decrease from the rated output voltage Vbus2 to the first bus voltage Vbus1, and then the first control signal Cctr1 controls the step-up / down DC module 230 to decrease its duty cycle, and the DC output voltage Vdc gradually increases with the duty cycle, that is, it works in the third working stage of the Boost working mode; when the DC When the output voltage Vdc reaches the third voltage value V3 or the duty cycle of the buck-boost DC module 230 reaches the third predetermined value Dduty3, the second control signal Cctr2 controls the bus voltage Vbus output by the isolation conversion module 210 to increase from the first bus voltage Vbus1 to the rated output voltage Vbus2, and the duty cycle of the buck-boost DC module 230 increases. Then, the first control signal Cctr1 controls the duty cycle of the buck-boost DC module 230 to gradually decrease, and the DC output voltage Vdc gradually increases, that is, it works in the fourth working stage of the Boost working mode.

[0041] In this way, by selecting the buck-boost DC module 230 as the post-stage DC / DC conversion circuit of the charging and discharging circuit of the battery module for the electric vehicle, and controlling the buck-boost DC module 230 to work in the first and second working stages of the Buck working mode and the third and fourth working stages of the Boost working mode in sequence, when the DC output voltage Vdc is low, the buck-boost DC module 230 works in the Buck working mode, and when the DC output voltage Vdc is high, the buck-boost DC module 230 works in the Boost working mode, thereby reducing the voltage level requirement for the bus voltage Vbus and widening the voltage range of the DC output voltage Vdc. Using the isolation conversion module 210 with a lower bus voltage Vbus can meet the wider voltage range of the DC output voltage Vdc, and the isolation conversion module with a lower bus voltage Vbus level can increase the market selection space of the components in the isolation conversion module 210, making it easier to select components with both excellent performance and price. In addition, since the use of an isolation conversion module 210 with a lower bus voltage Vbus can meet a wider voltage range of the DC output voltage Vdc, it is possible to use the existing cost-effective isolation conversion module 210 with a lower output bus voltage Vbus in the charging and discharging circuit to meet the market demand for battery modules with increasingly wider voltage levels. Designers only need to modify the subsequent step-up and step-down DC module 230 without having to modify the previous isolation module that has strict requirements on safety regulations, EMC, etc., thereby greatly reducing the design difficulty, cycle and cost of designers.

[0042] Furthermore, when the DC output voltage Vdc is approximately less than the rated output voltage Vbus2 of the isolation conversion module 210, the first control signal Cctr1 controls the buck-boost DC module 230 to operate in the Buck operating mode. When the DC output voltage Vdc is approximately greater than the rated output voltage Vbus2 of the isolation conversion module 210, the first control signal Cctr1 controls the buck-boost DC module 230 to operate in the Boost operating mode. For example, the isolation conversion module 210 with a 48V bus voltage Vbus satisfies the requirement that the voltage range of the DC output voltage Vdc is 0V to 120V. When the DC output voltage Vdc is approximately less than 48V, the buck-boost DC module 230 is controlled to operate in the Buck operating mode. The voltage Vdc is approximately greater than 48V, and the buck-boost DC module 230 is controlled to work in the Boost working mode. Compared with the isolation conversion module 210 of the prior art that uses a 140V bus voltage Vbus to meet the voltage range of the DC output voltage Vdc of 0V to 120V, the present invention can improve the accuracy within the full voltage range, and the range of poor accuracy is also greatly reduced, such as from 0V to 20V to 0V to 5V; and reduce the range of low-efficiency areas, such as the area with a duty cycle less than, for example, 10% is a small duty cycle low-efficiency area, that is, the area in which the DC output voltage Vdc is 0V to 4.8V is a low-efficiency area, and the range of the low-efficiency area becomes smaller, thereby increasing the high-precision voltage range of its output voltage and improving efficiency.

[0043] Further analysis shows that in the process of switching from Buck working mode to Boost working mode, in order to avoid entering the non-working area with a large duty cycle and affecting the control accuracy of the buck-boost DC module 230, the present invention controls the bus voltage Vbus of the isolation conversion module 210 to switch between the rated output voltage value Vbus2 and the first bus voltage value Vbus1, and correspondingly controls the buck-boost DC module 230 to switch from the first working stage to the second working stage, and then to the third working stage, thereby avoiding entering the non-working area with a large duty cycle, and improving the control accuracy of the buck-boost DC module 230, especially when the full charge voltage of the battery module is close to the rated output voltage Vbus2 of the isolation conversion module 210, the effect of the present invention on improving the voltage accuracy of the battery module is more obvious. And by including the third working stage and the fourth working stage in the Boost working mode, the Boost working mode is made to work more in the high duty cycle high efficiency area and the normal working area, thereby improving the overall efficiency of the buck-boost DC module 230.

[0044] like Figure 3As shown, the control circuit 270 receives the detection signal Ssense reflecting the working state of the buck-boost DC module 230, and outputs the first control signal Cctr1 and the second control signal Cctr2 according to the detection signal Ssense, controls the buck-boost DC module 230 to work in the first working stage, the second working stage, the third working stage or the fourth working stage according to the first control signal Cctr1, and controls the isolation conversion module 210 to output the first bus voltage value Vbus1 or the rated output voltage value Vbus2 according to the second control signal Cctr2. In the first working stage of the buck-boost DC module 230, the isolation conversion module 210 outputs the first bus voltage Vbus1, in the second working stage of the buck-boost DC module 230, the isolation conversion module 210 outputs the rated output voltage Vbus2, in the third working stage of the buck-boost DC module 230, the isolation conversion module 210 outputs the first bus voltage Vbus1, and in the fourth working stage of the buck-boost DC module 230, the isolation conversion module 210 outputs the rated output voltage Vbus2.

[0045] In one embodiment, the detection signal Ssense is a signal reflecting the DC output voltage Vdc of the buck-boost DC module 230. As described above, the buck-boost DC module 230 operates in the first working stage when the power is turned on. When the DC output voltage Vdc reaches the first voltage value V1, the buck-boost DC module 230 switches to the second working stage. When the DC output voltage Vdc reaches the second voltage value V2, the buck-boost DC module 230 switches to the third working stage. When the DC output voltage Vdc reaches the third voltage value V3, the buck-boost DC module 230 switches to the fourth working stage, wherein the second voltage value V2 is greater than the first bus voltage Vbus1 and less than the rated output voltage Vbus2 of the isolation conversion module 210, the first voltage value V1 is less than the second voltage value V2, and the second voltage value V2 is less than the third voltage value V3. By way of example, in one embodiment of the present invention, the buck-boost DC module 230 is a buck / boost converter. For details, please refer to Figure 5 , Figure 5 FIG. 1 is a circuit diagram of a buck / boost converter according to an embodiment of the present invention. Figure 5As shown, the Buck / Boost converter includes a first capacitor C1, a second capacitor C2, an inductor L1, a first switch element Q1, a second switch element Q2, a third switch element Q3 and a fourth switch element Q4; the positive end of the bus voltage Vbus is connected to one end of the first capacitor C1 and the drain of the first switch element Q1, the source of the first switch element Q1 is connected to the drain of the second switch element Q2, the other end of the first capacitor C1 and the source of the second switch element Q2 are connected to the negative end of the bus voltage Vbus, one end of the inductor L1 is connected to the source of the first switch element Q1 and the drain of the second switch element Q2, the other end of the inductor L1 is connected to the drain of the third switch element Q3 and the source of the fourth switch element Q4, the drain of the fourth switch element Q4 is connected to one end of the second capacitor C2 and the positive end of the DC output voltage Vdc, the source of the third switch element Q3 is connected to the other end of the second capacitor C2 and the negative end of the DC output voltage Vdc, and is connected to the source of the second switch element Q2. It can control the first switch element Q1 and the second switch element Q2 to be turned on alternately, the fourth switch element Q4 to be turned on all the time, and the third switch element Q3 to be turned off all the time according to the first control signal Cctr1 to work in the Buck working mode, or control the fourth switch element Q4 and the third switch element Q3 to be turned on alternately, the first switch element Q1 to be turned on all the time, and the second switch element Q2 to be turned off all the time according to the first control signal Cctr1 to work in the Boost working mode, and control the duty cycle of the first switch element Q1 to work in the first working stage or the second working stage of the Buck working mode, or control the duty cycle of the fourth switch element Q4 to work in the third working stage or the fourth working stage of the Boost working mode. Figure 4As mentioned above, in the Buck working mode, the duty cycle of the buck-boost DC module 230 is the duty cycle of the first switch element Q1, and in the Boost working mode, the duty cycle of the buck-boost DC module 230 is the duty cycle of the fourth switch element Q4. That is, the buck-boost DC module 230 may include at least two switches, and the duty cycle of the buck-boost DC module 230 corresponds to the duty cycle of different switch elements in the Buck working mode and in the Boost working mode. If the DC output voltage Vdc of the buck-boost DC module 230 is required to range from 0V to 120V, a standard isolation converter with a rated output voltage of 48V can be selected as the isolation conversion module 210, and the first bus voltage Vbus1 of the bus voltage Vbus output by the isolation conversion module 210 is set to 45V, then the second voltage value V2 can be set to 47V, and the first voltage value V1 can be set to 44V, and the third voltage value V3 can be set to 50V. After the power is turned on, the duty cycle increases, and the DC output voltage Vdc increases. When the DC output voltage Vdc increases to the first voltage value V1 (i.e. 44V), the duty cycle increases to about 97.8%, and the first working stage is switched to the second working stage, so that the duty cycle is reduced to about 91.7%; the duty cycle increases, the DC output voltage Vdc increases, and when the DC output voltage Vdc increases to the second voltage value V2 (i.e. 47V), the duty cycle increases to about 97.9%, and the second working stage of the Buck working mode is switched to the second working stage. to the third working stage of the Boost working mode; the duty cycle decreases, the DC output voltage Vdc increases, and when the DC output voltage Vdc increases to the third voltage value V3 (i.e. 50V), the duty cycle decreases to about 90.0%, and then the third working stage is switched to the fourth working stage, so that the duty cycle increases to about 96.04%, and then the duty cycle gradually decreases, the DC output voltage Vdc; when the DC output voltage Vdc reaches the maximum value of 120V, the duty cycle of the buck-boost DC module 230 is about 40.0%. In this way, by selecting a standard isolation converter with a rated output voltage of 48V as the isolation conversion module 210, the DC output voltage Vdc range of the buck-boost DC module 230 can be realized from 0V to 120V, and the buck-boost DC module 230 is prevented from entering the extremely large duty cycle non-working area, the extremely small duty cycle non-working area and the small duty cycle low efficiency area become smaller, and the high duty cycle high efficiency area is increased. If the buck DC module 130 is used as in the prior art, a standard isolation converter with a rated output voltage greater than 120V needs to be selected as the isolation conversion module 210, which will cause the problems described in the prior art. In one embodiment, the first voltage value V1, the second voltage value V2 and the third voltage value V3 are selected so that the buck-boost DC module 230 does not enter the non-working region with a large duty cycle, especially in the process of switching from the first working stage to the second working stage, switching from the second working stage to the third working stage and switching from the third working stage to the fourth working stage.

[0046] In one embodiment, the detection signal Ssense is a signal reflecting the duty cycle of the switch of the buck-boost DC module 230. For example, when the buck-boost DC module 230 is turned on, it works in the first working stage. When the duty cycle of the buck-boost DC module 230 increases to the first predetermined value Dduty1, the buck-boost DC module 230 switches to the second working stage of the Buck working mode. When the duty cycle of the buck-boost DC module 230 increases to the second predetermined value Dduty2, the buck-boost DC module 230 switches to the third working stage of the Boost working mode. When the duty cycle of the buck-boost DC module 230 gradually decreases to the third predetermined value Dduty3, the buck-boost DC module 230 switches to the fourth working stage of the Boost working mode. In one embodiment, the first predetermined value Dduty1, the second predetermined value Dduty2 and the third predetermined value Dduty3 are selected so that the buck-boost DC module 230 does not enter the extremely large duty cycle non-working region, especially in the processes of switching from the first working stage to the second working stage, switching from the second working stage to the third working stage, and switching from the third working stage to the fourth working stage.

[0047] In one embodiment, the third predetermined value Dduty3 or the third voltage value V3 is selected, that is, the point for switching from the third working stage to the fourth working stage of the Boost working mode is selected, so that after switching from the third working stage to the fourth working stage causes the duty cycle to increase, it will not cause the buck-boost DC module 230 to enter the extremely large duty cycle non-working area, that is, the fourth predetermined value Dduty4 does not increase to the extremely large duty cycle area (corresponding to the extremely large duty cycle non-working area).

[0048] In one embodiment, the first predetermined value Dduty1 and the second predetermined value Dduty2 are less than the lower limit of the extremely large duty cycle region. In one embodiment, the first predetermined value Dduty1 is equal to the second predetermined value Dduty2.

[0049] Specifically, in one embodiment, the buck-boost DC module 230 is an interlaced parallel buck-boost DC module, such as an interlaced parallel buck / boost converter. Figure 6 , Figure 6 FIG. 1 is a circuit diagram of an interleaved parallel buck / boost converter according to an embodiment of the present invention. Figure 6 As shown, in Figure 5 The interleaved parallel Buck / Boost converter based on the Buck / Boost converter shown in FIG. 1 further includes a switch module composed of a fifth switch element Q5 to an eighth switch element Q8, and the connection relationship between them is the same as Figure 5The connection relationship between the first switch element Q1 to the fourth switch element Q4 is the same, which will not be repeated here, and the drain of the fifth switch element Q5 is connected to the positive end of the bus voltage Vbus, the source of the sixth switch element Q6 is connected to the negative end of the bus voltage Vbus, the drain of the eighth switch element Q8 is connected to the positive end of the DC output voltage Vdc, and the source of the seventh switch element Q7 is connected to the negative end of the DC output voltage Vdc. It can control the conduction and shutdown of the first switch element Q1 to the eighth switch element Q8 and their duty cycle according to the first control signal Cctr1 to control the staggered parallel Buck / Boost converter to work in the Buck working mode or the Boost working mode, and work in the first working stage or the second working stage of the Buck working mode, or the third working stage or the fourth working stage of the Boost working mode, and the staggered parallel Buck / Boost converter can reduce ripples and further improve the output voltage accuracy of the buck-boost DC module 230.

[0050] In one embodiment, the first control signal Cctr1 is a PWM switch control signal, which is used to control the on or off of the switch element in the buck-boost DC module 230. Figure 5 When the buck-boost DC module 230 is controlled to operate in the buck mode, the first control signal Cctr1 controls the first switch element Q1 and the second switch element Q2 to be alternately turned on, the fourth switch element Q4 to be always turned on, and the third switch element Q3 to be always turned off, so as to operate in the Buck mode, wherein the duty cycle of the buck-boost DC module 230 is the duty cycle of the first switch element Q1, or the first control signal Cctr1 controls the fourth switch element Q4 and the third switch element Q3 to be alternately turned on, the first switch element Q1 to be always turned on, and the second switch element Q2 to be always turned off, so as to operate in the Boost mode, wherein the duty cycle of the buck-boost DC module 230 is the duty cycle of the third switch element Q3, and controls the duty cycle of the first switch element Q1 to operate in the first working stage or the second working stage of the Buck mode, or controls the duty cycle of the third switch element Q3 to operate in the third working stage or the fourth working stage of the Boost mode.

[0051] In an embodiment of the present invention, the first switching element Q1 to the eighth switching element Q8 are any devices that can be turned on or off according to the control of the PWM switch control signal.

[0052] The isolation conversion module 210 is usually a standard module, which can be an isolation full-bridge converter, an isolation half-bridge converter or an LLC resonant converter. The present invention does not limit it, as long as it can achieve isolation between the output end and the input end, and the output voltage at its output end can be switched between the first bus voltage Vbus1 and the rated output voltage Vbus2 according to the second control signal Cctr2. Specifically, in one embodiment of the present invention, the second control signal Cctr2 is connected to the reference voltage circuit of the control circuit of the isolation conversion module 210, so that the reference voltage of the control circuit of the isolation conversion module 210 changes according to the second control signal Cctr2, thereby controlling the bus voltage Vbus of the isolation conversion module 210 to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2. Specifically, in one embodiment of the present invention, the isolation conversion module 210 is a standard module including multiple isolation converters connected in parallel, and the isolation conversion module 210 also includes a current sharing bus and a current sharing control circuit connected to the current sharing bus to achieve current sharing between multiple isolation converters connected in parallel. Usually, the current sharing bus has a smaller voltage adjustment range, such as about 5%. Furthermore, the second control signal Cctr2 is output to the current sharing control circuit, so that the current sharing control circuit controls the bus voltage Vbus of the current sharing bus to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2 according to the second control signal Cctr2. In this way, the smaller voltage adjustment range of the current sharing bus is used to control the bus voltage Vbus to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2. As described above, without changing the internal structure of the isolation conversion module 210 of the inherent standard module, the output voltage of the isolation conversion module 210 can be switched between the first bus voltage Vbus1 and the rated output voltage Vbus2 by outputting the second control signal Cctr2 to the reference voltage circuit or the current sharing control circuit of the isolation conversion module 210, which is simple in design and low in cost. In order to realize the function of the present invention, it is only necessary for the bus voltage Vbus to change within a smaller voltage range (such as 5%), so the design, control accuracy and efficiency of the isolation conversion module 210 are not affected. In one embodiment, the difference between the rated output voltage Vbus2 and the first bus voltage Vbus1 is less than or equal to 5% of the rated output voltage Vbus2.

[0053] See also Figure 7 , Figure 7 FIG. 1 is a block diagram of a control circuit according to an embodiment of the present invention. In an embodiment of the present invention, Figure 7As shown, the control circuit 270 includes an error amplifier, a PWM wave generator and a signal conversion unit. One input end of the error amplifier receives the detection signal Ssense, and the other input end of the error amplifier receives a reference signal (such as a signal related to the first voltage value V1, the second voltage value V2 and the third voltage value V3, or the first predetermined value, the second predetermined value and the third predetermined value of the duty cycle), and outputs an error signal. The PWM wave generator receives the error signal and generates a first control signal Cctr1 according to the error signal. The signal conversion unit receives the error signal and generates a second control signal Cctr2 according to the error signal, so that the second control signal Cctr2 controls the reference voltage or current sharing control circuit of the control circuit of the isolation conversion module 210.

[0054] In one embodiment of the present invention, the rated output voltage of the isolation conversion module 210 is 48V, and the voltage range of the DC output voltage Vdc of the buck-boost DC module 230 is 0V to a voltage greater than 48V, such as 0V to 120V or 0V to 160V.

[0055] In addition, the charging circuit of the battery module used in the electric vehicle also includes an AC protection control circuit 250 connected between the AC power supply 220 and the isolation conversion module 210, and a protection / pre-charging circuit 260 connected between the buck-boost DC module 230 and the battery module 240. The specific structures of the AC protection control circuit 250 and the protection / pre-charging circuit 260 are not limited by the present invention. For the AC protection control circuit 250, it only needs to be connected between the AC power supply 220 and the isolation conversion module 210 and realize the function of AC protection; for the protection / pre-charging circuit 260, it only needs to be connected between the buck-boost DC module 230 and the battery module 240 and realize the functions of protection and pre-charging.

[0056] In one embodiment of the present invention, the isolation conversion module 210 and the buck-boost DC module 230 are bidirectional conversion modules, and the charging circuit of the battery module applied to the electric vehicle of the present invention can also be a charging and discharging circuit. When energy flows in the forward direction, the AC input voltage Vac is converted into a DC bus voltage Vbus by the isolation conversion module 210, and the bus voltage Vbus is input to the buck-boost DC module 230, and converted into a DC output voltage Vdc by the buck-boost DC module 230 to charge the battery module 240; when energy flows in the reverse direction, the buck-boost DC module 230 receives the DC output voltage Vdc of the battery module 240 and converts it into a bus voltage Vbus, and the isolation conversion module 210 receives the bus voltage Vbus and inverts it into an AC input voltage Vac to the AC power supply 220, so as to recover the energy of the battery module 240 to the AC power supply 220, thereby realizing the bidirectional flow of energy.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A charging circuit for a battery module of an electric vehicle, characterized in that: include: An isolation conversion module, whose input end is connected to an AC power supply, receives an AC input voltage, converts the AC input voltage Vac into a bus voltage Vbus at its output end, and provides isolation between its output end and input end, wherein the bus voltage Vbus includes a rated output voltage value Vbus2 of the isolation conversion module and a first bus voltage value Vbus1 which is smaller than the rated output voltage value Vbus2; A buck-boost DC module, comprising at least one switch element, an input end of which is connected to the output end of the isolation conversion module, receives the bus voltage Vbus, and converts the bus voltage Vbus into a DC output voltage Vdc; A battery module, connected to the buck-boost DC module, receiving the DC output voltage Vdc to charge the battery module; A control circuit receives a detection signal Ssense, and outputs a first control signal Cctr1 to the buck-boost DC module and a second control signal Cctr2 to the isolation conversion module according to the detection signal Ssense, wherein the first control signal Cctr1 controls the buck-boost DC module to first work in the Buck working mode and then switch to the Boost working mode, and in the Buck working mode, first work in the first working stage and then switch to the second working stage, and in the Boost working mode, first work in the third working stage and then switch to the fourth working stage, and the second control signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1 or the rated output voltage value Vbus2, wherein in the first working stage, the second control signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1, and the first control signal Cctr1 controls the duty cycle of the buck-boost DC module to gradually increase, and the buck-boost DC The DC output voltage Vdc of the module gradually increases. In the second working stage, the second control signal Cctr2 controls the isolation conversion module to output the rated output voltage value Vbus2. The first control signal Cctr1 controls the duty cycle of the buck-boost DC module to decrease and then gradually increase, and the DC output voltage Vdc of the buck-boost DC module gradually increases. In the third working stage, the second control signal Cctr2 controls the isolation conversion module to output the first bus voltage value Vbus1. The first control signal Cctr1 controls the duty cycle of the buck-boost DC module to decrease, and the DC output voltage Vdc of the buck-boost DC module gradually increases. In the fourth working stage, the second control signal Cctr2 controls the isolation conversion module to output the rated output voltage value Vbus2. The first control signal Cctr1 controls the duty cycle of the buck-boost DC module to increase and then gradually decrease, and the DC output voltage Vdc of the buck-boost DC module gradually increases. The difference between the rated output voltage Vbus2 and the first bus voltage Vbus1 is less than or equal to 5% of the rated output voltage Vbus2; The detection signal Ssense is a signal reflecting the working state of the buck-boost DC module, and the control circuit outputs the first control signal Cctr1 and the second control signal Cctr2 according to the detection signal Ssense.

2. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The detection signal Ssense is a signal reflecting the DC output voltage Vdc of the buck-boost DC module.

3. The charging circuit of the battery module used in an electric vehicle according to claim 2, characterized in that: When powered on, the buck-boost DC module operates in the first working stage; when the DC output voltage Vdc reaches the first voltage value V1, the buck-boost DC module switches to the second working stage; when the DC output voltage Vdc reaches the second voltage value V2, the buck-boost DC module switches to the third working stage; when the DC output voltage Vdc reaches the third voltage value V3, the buck-boost DC module switches to the fourth working stage, wherein the second voltage value V2 is greater than the first bus voltage Vbus1 and less than the rated output voltage Vbus2 of the isolation conversion module, the first voltage value V1 is less than the second voltage value V2, and the second voltage value V2 is less than the third voltage value V3.

4. The charging circuit of the battery module used in an electric vehicle according to claim 3, characterized in that: The first voltage value V1, the second voltage value V2 and the third voltage value V3 are selected so that the buck-boost DC module does not enter a non-working region with a very large duty cycle.

5. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The detection signal Ssense is a signal reflecting the duty cycle of the switch element of the buck-boost DC module.

6. The charging circuit of the battery module used in the electric vehicle according to claim 5, characterized in that: When the power is turned on, the buck-boost DC module works in the first working stage. When the duty cycle of the buck-boost DC module increases to the first predetermined value Dduty1, the buck-boost DC module switches to the second working stage of the Buck working mode. When the duty cycle of the buck-boost DC module increases to the second predetermined value Dduty2, the buck-boost DC module switches to the third working stage of the Boost working mode. When the duty cycle of the buck-boost DC module decreases to the third predetermined value Dduty3, the buck-boost DC module switches to the fourth working stage of the Boost working mode.

7. The charging circuit of the battery module used in the electric vehicle according to claim 6, characterized in that: The first predetermined value Dduty1, the second predetermined value Dduty2 and the third predetermined value Dduty3 are selected so that the buck-boost DC module does not enter a non-working region with a very large duty cycle.

8. The charging circuit of the battery module used in the electric vehicle according to claim 7, characterized in that: The first predetermined value Dduty1 is equal to the second predetermined value Dduty2.

9. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The step-up / step-down DC module is a Buck / Boost converter.

10. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The buck-boost DC module is a buck-boost DC module connected in parallel.

11. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The first control signal Cctr1 is a switch control signal, which is used to control the on or off of the switch element in the buck-boost DC module.

12. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The second control signal Cctr2 is connected to the reference voltage circuit of the control circuit of the isolation conversion module, so that the reference voltage of the control circuit of the isolation conversion module changes according to the second control signal Cctr2, thereby controlling the bus voltage Vbus of the isolation conversion module to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2.

13. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The isolation conversion module includes multiple isolation converters connected in parallel, and includes a current sharing bus and a current sharing control circuit connected to the current sharing bus. The second control signal Cctr2 is output to the current sharing control circuit, so that the current sharing control circuit controls the bus voltage Vbus of the current sharing bus to switch between the first bus voltage Vbus1 and the rated output voltage Vbus2 according to the second control signal Cctr2.

14. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The voltage range of the DC output voltage Vdc of the buck-boost DC module is 0V to a voltage greater than 48V.

15. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: It also includes an AC protection control circuit connected between the AC power supply and the isolation conversion module, and a protection / pre-charging circuit connected between the buck-boost DC module and the battery module.

16. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The isolation conversion module and the buck-boost DC module are bidirectional conversion modules.

17. The charging circuit of the battery module used in an electric vehicle according to claim 1, characterized in that: The control circuit includes an error amplifier, a PWM wave generator and a signal conversion unit. One input end of the error amplifier receives a detection signal Ssense, the other input end of the error amplifier receives a reference signal, and outputs an error signal. The PWM wave generator receives the error signal and generates the first control signal Cctr1 according to the error signal. The signal conversion unit receives the error signal and generates the second control signal Cctr2 according to the error signal.

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