Low-frequency ripple current suppression circuit, and power supply system having low-frequency ripple current suppression functionality

Abstract

A low-frequency ripple current suppression circuit, and a power supply system having low-frequency ripple current suppression functionality. The low-frequency ripple current suppression circuit comprises a first boost circuit and a second boost circuit. The first boost circuit comprises a first inductor, a first switch group and a first capacitor, the first switch group comprising a first switch and a second switch. The second boost circuit comprises a second inductor, a second switch group, and a second capacitor, the second switch group comprising a third switch and a fourth switch. The low-frequency ripple current suppression circuit receives a direct current having a ripple component, and suppresses the ripple component by means of the first boost circuit and the second boost circuit.

Description

Low-frequency ripple current suppression circuit and power supply system with low-frequency ripple current suppression function TECHNICAL FIELD

[0001] The present application relates to a current suppression circuit and a power supply system with current suppression function, in particular to a low-frequency ripple current suppression circuit and a power supply system with low-frequency ripple current suppression function. BACKGROUND

[0002] With the rise of environmental awareness, the trend of electric vehicle sales has doubled, and the demand for charging station installation has increased. It is the common goal of those skilled in the art to provide overall power efficiency and charging quality in response to the charging needs of electric vehicles.

[0003] Therefore, how to design a low-frequency ripple current suppression circuit and a power supply system with low-frequency ripple current suppression function to solve the problems and technical bottlenecks existing in the prior art is an important research topic for the present inventors.

[0004] SUMMARY

[0005] One object of the present application is to provide a low-frequency ripple current suppression circuit. The low-frequency ripple current suppression circuit includes a first boost circuit and a second boost circuit. The first boost circuit includes a first inductor, a first switch group, and a first capacitor. The first inductor has a first end and a second end, and the first end of the first inductor is connected to a first DC side. The first switch group includes a first switch and a second switch; the first switch has a first end and a second end, and the first end of the first switch is connected to the second end of the first inductor, and the second end of the first switch is connected to a virtual ground node; the second switch has a first end and a second end, and the first end of the second switch is connected to the second end of the first inductor. The first capacitor has a first end and a second end, and the first end of the first capacitor is connected to the second end of the second switch, and the second end of the first capacitor is connected to the virtual ground node. The second boost circuit includes a second inductor, a second switch group, and a second capacitor. The second inductor has a first end and a second end, and the first end of the second inductor is connected to a second DC side. The second switch group includes a third switch and a fourth switch; the third switch has a first end and a second end, and the first end of the third switch is connected to the second end of the second inductor, and the second end of the third switch is connected to the virtual ground node; the fourth switch has a first end and a second end, and the first end of the fourth switch is connected to the second end of the second inductor. The second capacitor has a first end and a second end, and the first end of the second capacitor is connected to the second end of the fourth switch, and the second end of the second capacitor is connected to the virtual ground node. The low-frequency ripple current suppression circuit receives a DC current with ripple components, and absorbs the ripple components through the first boost circuit and the second boost circuit.

[0006] Another object of the present application is to provide a power supply system with low-frequency ripple current suppression function. The power supply system with low-frequency ripple current suppression function comprises three single-phase AC-to-DC conversion circuits and a low-frequency ripple current suppression circuit. Each single-phase AC-to-DC conversion circuit is coupled to each phase of a three-phase AC power source, and the output side of the single-phase AC-to-DC conversion circuits is connected to an output node and outputs a DC current. The low-frequency ripple current suppression circuit is connected to the output node. The low-frequency ripple current suppression circuit comprises a first boost circuit and a second boost circuit. The first boost circuit comprises a first inductor, a first switch group, and a first capacitor. The first switch group comprises a first switch and a second switch. The first inductor is connected to the first switch at a first common node, and is connected between a first DC side and a potential equalization node. The second switch is connected in series with the first capacitor, and is connected between the first common node and the potential equalization node. The second boost circuit comprises a second inductor, a second switch group, and a second capacitor. The second switch group comprises a third switch and a fourth switch. The second inductor is connected to the third switch at a second common node, and is connected between a second DC side and the potential equalization node. The fourth switch is connected in series with the second capacitor, and is connected between the second common node and the potential equalization node.

[0007] Thus, the low-frequency ripple current suppression circuit and the power supply system with low-frequency ripple current suppression function have the following characteristics and advantages: 1. By using the low-frequency ripple current suppression circuit, the system efficiency can be maintained when the load demand is light, and the ripple component of the DC current is eliminated, so that the output current flowing to the load is a DC current without ripple component. 2. The low-frequency ripple current suppression circuit can be realized by simple circuit design and control.

[0008] In order to further understand the technology, means, and effects adopted by the present application to achieve the predetermined purposes, please refer to the following detailed description and drawings of the present application. It is believed that the purposes, features, and characteristics of the present application can be thoroughly and specifically understood from the above description, however, the drawings provided for reference and illustration only, and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a circuit block diagram of a first embodiment of a plurality of single-phase AC-to-DC conversion circuits according to the present application;

[0010] FIG. 2 is a circuit block diagram of a second embodiment of a plurality of single-phase AC-to-DC conversion circuits according to the present application;

[0011] FIG. 3 is a circuit block diagram of a three-group single-phase AC-to-DC conversion circuit power supply according to the present application;

[0012] FIG. 4 is a circuit block diagram of a two-group single-phase AC-to-DC conversion circuit power supply according to the present application;

[0013] Fig. 5 is a circuit block diagram of a power supply circuit of a single-phase AC-to-DC conversion circuit according to the present application;

[0014] Fig. 6 is a circuit diagram of a low-frequency ripple current suppression circuit according to the present application;

[0015] Fig. 7 is a circuit block diagram of a power supply system with a low-frequency ripple current suppression function according to the present application;

[0016] Fig. 8 is a circuit block diagram of the operation of a power supply system with a low-frequency ripple current suppression function according to the present application.

[0017] Explanation of Reference Numerals

[0018] 10: low-frequency ripple current suppression circuit

[0019] 100-1, 100-2, 100-3: single-phase AC-to-DC conversion circuit

[0020] 101-1, 101-2, 101-3: rectifier circuit

[0021] 102-1, 102-2, 102-3: single-phase isolated power factor correction circuit

[0022] Vin_R, Vin_S, Vin_T: three-phase AC power

[0023] 11: first voltage booster circuit

[0024] L1: first inductor

[0025] S1: first switch group

[0026] S11: first switch

[0027] S12: second switch

[0028] C1: first capacitor

[0029] 12: second voltage booster circuit

[0030] L2: second inductor

[0031] S2: second switch group

[0032] S21: third switch

[0033] S22: fourth switch

[0034] C2: second capacitor

[0035] Cf1: first filter capacitor

[0036] Cf2: second filter capacitor

[0037] O: equipotential node

[0038] 13: filter circuit

[0039] 20: load

[0040] 30: power supply controller

[0041] idc: direct current

[0042] Irip: ripple component

[0043] Idc: output current

[0044] NO: output node

[0045] DC1: first direct current side

[0046] DC2: second direct current side

[0047] VBAT: battery

[0048] SLD: load information signal

[0049] SCAD1, SCAD2, SCAD3: switching circuit control signal

[0050] SCRC: switch control signal DETAILED DESCRIPTION

[0051] The technical contents and detailed descriptions of the present application are described below in conjunction with the accompanying drawings.

[0052] The following is a description of the embodiments of the present application by specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in the present specification. The present application can also be implemented or applied by other different specific examples, and each detail in the present specification can be modified and changed based on different viewpoints and applications without departing from the spirit of the present application.

[0053] It should be understood that the structures, proportions, sizes, and numbers of elements shown in the accompanying drawings of the present specification are only used to understand and read the contents disclosed in the present specification, and do not define the limiting conditions for implementing the present application, and therefore do not have technical substantial significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by the present application, should fall within the scope of the technical contents disclosed in the present application.

[0054] Referring to FIG. 1, a circuit block diagram of a first embodiment of a multi-set single-phase AC-to-DC conversion circuit is shown. As shown in FIG. 1, a three-set single-phase AC-to-DC conversion circuit 100-1, 100-2, 100-3 is used in a three-phase power charging system. The three-set single-phase AC-to-DC conversion circuit 100-1, 100-2, 100-3 is coupled to two phases of a three-phase AC power source, for example, the first single-phase AC-to-DC conversion circuit 100-1 is coupled to the R phase and the S phase of the three-phase AC power source; the second single-phase AC-to-DC conversion circuit 100-2 is coupled to the S phase and the T phase of the three-phase AC power source; and the third single-phase AC-to-DC conversion circuit 100-3 is coupled to the T phase and the R phase of the three-phase AC power source. In the embodiment of FIG. 1, the three-set single-phase AC-to-DC conversion circuit is in a delta connection configuration. Each single-phase AC-to-DC conversion circuit includes a rectifier circuit 101-1, 101-2, 101-3 and a single-phase isolated power factor correction circuit 102-1, 102-2, 102-3. Specifically, the first single-phase AC-to-DC conversion circuit 100-1 includes a first rectifier circuit 101-1 and a first single-phase isolated power factor correction circuit 102-1; the second single-phase AC-to-DC conversion circuit 100-2 includes a second rectifier circuit 101-2 and a second single-phase isolated power factor correction circuit 102-2; and the third single-phase AC-to-DC conversion circuit 100-3 includes a third rectifier circuit 101-3 and a third single-phase isolated power factor correction circuit 102-3.

[0055] Referring to FIG. 2, a circuit block diagram of a second embodiment of a multi-set single-phase AC-to-DC conversion circuit is shown. In the embodiment of FIG. 2, the three-set single-phase AC-to-DC conversion circuit is in a star connection configuration. Either the delta connection configuration or the star connection configuration can sufficiently provide the required power under full load or heavy load. Thus, as shown in FIG. 3, a circuit block diagram of a three-set single-phase AC-to-DC conversion circuit is shown. Under a three-phase balanced power supply, the three-set single-phase AC-to-DC conversion circuit can provide a load (e.g., a battery V BAT a ripple-free DC (output) current i dc a charging current.

[0056] However, as the charging load is reduced (e.g. reduced to 2 / 3 load output), in order to maintain system efficiency, a set of single-phase isolated AC-to-DC conversion circuits are usually turned off to charge the load with lower output power, resulting in phase shedding power supply. However, under this operating condition, due to the unbalanced three-phase power supply, the DC output contains AC components above the second harmonic of line frequency (e.g. 50Hz or 60Hz), as shown in Fig. 4, the DC (output) current i dc Ripple components are generated, which affect the quality of power supply to the load, and even the service life of the load. If the charging load is further reduced (e.g. reduced to 1 / 3 load output) or charging a light load, a second set of single-phase isolated AC-to-DC conversion circuits are turned off, as shown in Fig. 5, however, the DC (output) current i dc The generated ripple components will be even larger.

[0057] It is noted that each single-phase AC-to-DC conversion circuit shown in Figs. 1 and 2 further comprises a first filter capacitor 103-1, 103-2, 103-3 and a second filter capacitor 104-1, 104-2, 104-3. Taking the first single-phase AC-to-DC conversion circuit 100-1 as an example: the first single-phase AC-to-DC conversion circuit 100-1 comprises a first filter capacitor 103-1 and a second filter capacitor 104-1, which are respectively coupled to the input side and the output side of the first single-phase isolated power factor correction circuit 102-1. Unlike the electrolytic capacitor used in general PFC circuits, the purpose is to filter out the AC components above the second harmonic of line frequency of its output, so its capacitance value is high, and the size is large.

[0058] In contrast, since the three sets of single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 of the present application respectively receive two-phase phase-shifted AC power of three-phase AC power, there is no need to process the second harmonic of line frequency. Specifically, the first filter capacitor 103-1 and the second filter capacitor 104-1 of the first single-phase AC-to-DC conversion circuit 100-1 are high-frequency filter capacitors, whose main purpose is to filter out high-frequency noise generated by high-frequency switching of power electronic high-frequency switching elements in the first single-phase AC-to-DC conversion circuit 100-1. Therefore, the first filter capacitor 103-1 and the second filter capacitor 104-1 can be realized by low-capacitance and small-size capacitor elements. The filter capacitors of the second single-phase AC-to-DC conversion circuit 100-2 and the third single-phase AC-to-DC conversion circuit 100-3 also have the same characteristics, so they are not described in more detail.

[0059] Therefore, based on the above-mentioned closing one or two groups of single-phase isolated converters under light load charging condition to improve system efficiency, the influence of the ripple component of the DC (output) current on the load, the present application proposes a low-frequency ripple current suppression circuit and a power supply system with low-frequency ripple current suppression function, which are described in detail as follows.

[0060] Please refer to FIG. 6, which is a circuit diagram of the low-frequency ripple current suppression circuit of the present application. As shown in FIG. 6, the low-frequency ripple current suppression circuit 10 includes a first boost circuit 11 and a second boost circuit 12. The first boost circuit 11 includes a first inductor L1, a first switch group S1 and a first capacitor C1. The second boost circuit 12 includes a second inductor L2, a second switch group S2 and a second capacitor C2.

[0061] The first inductor L1 has a first end and a second end, and the first end of the first inductor L1 is connected to the first DC side DC1. The first switch group S1 includes a first switch S 11 and a second switch S 12 . The first switch S 11 has a first end and a second end, and the first end of the first switch S 11 is connected to the second end of the first inductor L1, and the second end of the first switch S 11 is connected to the equipotential node O. The second switch S 12 has a first end and a second end, and the first end of the second switch S 12 is connected to the second end of the first inductor L1. The first capacitor C1 has a first end and a second end, and the first end of the first capacitor C1 is connected to the second end of the second switch S 12 , and the second end of the first capacitor C1 is connected to the equipotential node O.

[0062] The second inductor L2 has a first end and a second end, and the first end of the second inductor L2 is connected to the second DC side DC2. The second switch group S2 includes a third switch S 21 and a fourth switch S 22 . The third switch S 21 has a first end and a second end, and the first end of the third switch S 21 is connected to the second end of the second inductor L2, and the second end of the third switch S 21 is connected to the equipotential node O. The fourth switch S 22 has a first end and a second end, and the first end of the fourth switch S 22 is connected to the second end of the second inductor L2. The second capacitor C2 has a first end and a second end, and the first end of the second capacitor C2 is connected to the second end of the fourth switch S 22 , and the second end of the second capacitor C2 is connected to the equipotential node O.

[0063] The low-frequency ripple current suppression circuit 10 receives a DC input current I ripthe direct current i dc , and the ripple component I rip is absorbed by the first boost circuit 11 and the second boost circuit 12. dc Therefore, by the circuit architecture design of the low-frequency ripple current suppression circuit 10, the elimination of the ripple component I rip of the direct current i f1 is achieved.

[0064] It is noted that, since the low-frequency ripple current suppression circuit 10 is composed of two groups of boost circuits (i.e. the first boost circuit 11 and the second boost circuit 12), and the first capacitor C1 and the second capacitor C2 respectively bear the energy of the entire low-frequency ripple, therefore, in terms of voltage withstand or capacitance value, the specifications of the first capacitor C1 and the second capacitor C2 can be selected in a wider range and more flexibility, for example, low-voltage capacitor elements or capacitor elements with a wider capacitance value range can be selected.

[0065] Further, the low-frequency ripple current suppression circuit 10 further includes a filter circuit 13. The filter circuit 13 includes a first filter capacitor C f1 and a second filter capacitor C f2 . The first filter capacitor C f1 has a first end and a second end, the first end of the first filter capacitor C f1 is connected to the first direct current side DC1, and the second end of the first filter capacitor C f1 is connected to the equipotential node O. The second filter capacitor C f2 has a first end and a second end, the first end of the second filter capacitor C f2 is connected to the second direct current side DC2, and the second end of the second filter capacitor C f2 is connected to the equipotential node O.

[0066] It is noted that the first filter capacitor C f1 and the second filter capacitor C f2 are high-frequency filter capacitors, which are used to filter the high-frequency switching signals generated by the first switch S 11 and the second switch S 12 of the first switch group S1, and the high-frequency switching signals generated by the third switch S 21 and the fourth switch S 22 of the second switch group S2, and therefore the first filter capacitor C f1 and the second filter capacitor C f2 can be realized by capacitor elements with low capacitance value and small size.

[0067] As mentioned above, in order to achieve the elimination of the ripple component I dc of the direct current i ripThe elimination of [something] is achieved through the following control methods for the first switch group S1 of the first boost circuit 11 and the second switch group S2 of the second boost circuit 12. Incidentally, regarding the first switch group S1, the first switch S... 11 With the second switch S 12 and the third switch S of the second switch group S2 21 With the fourth switch S 22 The control can be achieved through the control signals generated by the controller or control unit. Therefore, the controller or control unit will not be drawn separately in the attached drawings, but will be described in advance.

[0068] The control signal generated by the controller affects the first switch S1 of the first switch group S1. 11 With the second switch S 12 To achieve synchronous and complementary switching on and off. That is, when the first switch S... 11 The second switch S is turned on. 12 Turn off; conversely, when the first switch S is turned on... 11 Turn off, second switch S 12 The circuit is turned on. Furthermore, the control signal generated by the controller affects the third switch S of the second switch group S2. 21 With the fourth switch S 22 To achieve synchronous and complementary switching on and off. That is, when the third switch S... 21 The fourth switch S is turned on. 22 Turn off; conversely, when the third switch S is turned off. 21 Off, fourth switch S 22 Conduction.

[0069] In one embodiment, the first switch S of the first switch group S1 11 The third switch S of the second switch group S2 21 To ensure synchronous switching on and off. In other words, when the first switch S... 11 The second switch S is turned on. 12 When turned off, the third switch S 21 The fourth switch S is turned on. 22 Turn off; conversely, when the first switch S is turned on... 11 Turn off, second switch S 12 When the circuit is turned on, the third switch S 21 Off, fourth switch S 22 Conduction.

[0070] In another embodiment, the first switch S of the first switch group S1 11 The third switch S of the second switch group S2 21 This allows for asynchronous switching on and off. Compared to the first switch S in the previous embodiment... 11 With the third switch S 21 To ensure synchronous switching on and off, in this embodiment, the first switch S 11with the third switch S 21 Instead of synchronous control, there is a time difference (phase difference) between the two for control. For example, when the first switch S 11 is turned on, the second switch S 12 is turned off, after a time interval, the third switch S 21 is turned on, and the fourth switch S 22 is turned off; conversely, when the first switch S 11 is turned off, the second switch S 12 is turned on, after a time interval, the third switch S 21 is turned off, and the fourth switch S 22 is turned on. In this way, the ripple component I dc of the direct current i rip can also be eliminated.

[0071] In addition, for the selection of the first switch group S1 and the second switch group S2, there are different embodiments. In one embodiment, as shown in Fig. 6, the first switch S 11 and the second switch S 12 of the first switch group S1 and the third switch S 21 and the fourth switch S 22 of the second switch group S2 are transistors. Therefore, the corresponding on and off control of all switches can be realized by the control signals generated by the controller, so as to achieve the effect of synchronous rectification.

[0072] In another embodiment, not shown, the first switch S 11 of the first switch group S1 and the third switch S 21 of the second switch group S2 are transistors, the second switch S 12 of the first switch group S1 and the fourth switch S 22 of the second switch group S2 are diodes. Therefore, the corresponding on and off control of the first switch S 11 of the first switch group S1 and the third switch S 21 of the second switch group S2 can be realized by the control signals generated by the controller.

[0073] Please refer to Fig. 7, which is a circuit block diagram of the power supply system with low-frequency ripple current suppression function. The power supply system with low-frequency ripple current suppression function (hereinafter referred to as the power supply system) includes three single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 (see Fig. 3 for details), namely, a first single-phase AC-to-DC conversion circuit 100-1, a second single-phase AC-to-DC conversion circuit 100-2, and a third single-phase AC-to-DC conversion circuit 100-3. Each single-phase AC-to-DC conversion circuit 100-1, 100-2, 100-3 is coupled to each phase of the three-phase AC power source, i.e., Vin_R, Vin_S, and Vin_T (not limited to the delta connection architecture of Fig. 1 or the star connection architecture of Fig. 2), and the output sides of the three single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 are connected to an output node N O , and output a DC current i dc .

[0074] Furthermore, the power supply system further includes a low-frequency ripple current suppression circuit 10. Since the low-frequency ripple current suppression circuit 10 has been described in detail in the foregoing disclosure, it will not be described again here. The input side of the low-frequency ripple current suppression circuit 10, i.e., a first DC side DC1, is connected to the output node N O , and thus receives the output DC current i dc from the three single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3.

[0075] As shown in Fig. 7, taking the example of closing two groups of single-phase isolated AC-to-DC conversion circuits (i.e., closing the second single-phase AC-to-DC conversion circuit 100-2 and the third single-phase AC-to-DC conversion circuit 100-3), the action of the low-frequency ripple current suppression circuit 10 to eliminate the ripple component I dc of the DC current i rip is explained. According to the content described in Fig. 5, it can be known that under the operation of Fig. 7, the ripple component I dc of the DC current i rip is large.

[0076] The output DC current i O from the output node N dc (i.e., the combined output current of the three groups of single-phase AC-to-DC conversion circuits) flows into the first DC side DC1, and is high-frequency filtered by the filter circuit 13, so that the filtered output DC current i dc flows into the first boost circuit 11 and the second boost circuit 12. As previously described, the DC current i dc flowing into the first boost circuit 11 and the second boost circuit 12 is conducted through the first switch S 11 of the first switch group S1 and turned off through the second switch S 12the ripple component I rip through the first switch S 11 stores energy in the first inductor L1, and then discharges the energy stored in the first inductor L1 through the first switch S 11 of the first switch set S1, and turns on the second switch S 12 so that the energy stored in the first inductor L1 is discharged through the second switch S 12 to the first capacitor C1.

[0077] Likewise, by turning on the third switch S 21 of the second switch set S2, and turning off the fourth switch S 22 the ripple component I rip stores energy in the second inductor L2 through the third switch S 21 , and then discharges the energy stored in the second inductor L2 through the third switch S 21 of the second switch set S2, and turns on the fourth switch S 22 so that the energy stored in the second inductor L2 is discharged through the fourth switch S 22 to the second capacitor C2. In this way, the ripple component I dc of the direct current i rip is absorbed by the first boost circuit 11 and the second boost circuit 12, and thus the output current I dc flowing to the load is a direct current without the ripple component I rip .

[0078] Please refer to FIG. 8, which is a circuit block diagram of the operation of the power supply system with low-frequency ripple current suppression function. The power supply system is used to charge a load 20, which can be, for example but not limited to, an electric vehicle (EV), and thus the low-frequency ripple current suppression circuit 10 is electrically connected between the single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 and the load 20, to eliminate (absorb) the ripple component I dc of the direct current i rip , and thus the output current I dc flowing to the load 20 is a direct current without the ripple component I rip .

[0079] In addition, according to the power supply requirements of the load 20, the number of single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 that are turned off can be determined to improve the power supply efficiency of the system. Therefore, the power supply system includes a power supply controller 30 to receive information of the load 20. Taking an electric vehicle as the load 20, the power supply controller 30 can receive the charging information required by the electric vehicle, which is represented by a load information signal S LD . Therefore, when the power supply controller 30 determines the number of single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3 to be turned off according to the load information signal S LDKnowing the charging information required by the load 20, the power supply controller 30 can provide a plurality of conversion circuit control signals S CAD1 CAD2 CAD3 , respectively, to control the closing or enabling of the single-phase AC-to-DC conversion circuits 100-1, 100-2, 100-3. If the charging information is for light load, as shown in Fig. 8, the power supply controller 30 closes the second single-phase AC-to-DC conversion circuit 100-2 and the third single-phase AC-to-DC conversion circuit 100-3, and only the first single-phase AC-to-DC conversion circuit 100-1 is required to provide power.

[0080] Furthermore, the power supply controller 30 can also provide switch control signals S CRC to control the first switch group S1 of the first boost circuit 11 and the second switch group S2 of the second boost circuit 12, so that the first boost circuit 11 and the second boost circuit 12 can eliminate the ripple component I dc of the DC current i rip , and the output current I dc flowing to the load 20 is a DC current without the ripple component I rip .

[0081] In summary, the present application has the following features and advantages:

[0082] 1. By using the low-frequency ripple current suppression circuit, when light load is required, the system efficiency can be maintained, and the ripple component of the DC current can be eliminated, so that the output current flowing to the load is a DC current without the ripple component.

[0083] 2. By simple circuit design and control, the low-frequency ripple current suppression circuit can be implemented.

[0084] The above description is only a detailed description of the preferred embodiments of the present application and the accompanying drawings, and the features of the present application are not limited thereto, and are not intended to limit the present application. The scope of the present application should be subject to the following claims, and any embodiments similar to the claims of the present application and their similar changes should be included in the scope of the present application. Any changes or modifications easily thought of by those skilled in the art in the field of the present application can be covered by the following claims.​​

Claims

1. A low-frequency ripple current suppression circuit, comprising: a first boost circuit, comprising: a first inductor having a first end and a second end, the first end of the first inductor connected to a first DC side; a first switch group comprising a first switch and a second switch, the first switch having a first end and a second end, the first end of the first switch connected to the second end of the first inductor, the second end of the first switch connected to a virtual ground node, the second switch having a first end and a second end, the first end of the second switch connected to the second end of the first inductor; and a first capacitor having a first end and a second end, the first end of the first capacitor connected to the second end of the second switch, the second end of the first capacitor connected to the virtual ground node; and a second boost circuit, comprising: a second inductor having a first end and a second end, the first end of the second inductor connected to a second DC side; a second switch group comprising a third switch and a fourth switch, the third switch having a first end and a second end, the first end of the third switch connected to the second end of the second inductor, the second end of the third switch connected to the virtual ground node, the fourth switch having a first end and a second end, the first end of the fourth switch connected to the second end of the second inductor; and a second capacitor having a first end and a second end, the first end of the second capacitor connected to the second end of the fourth switch, the second end of the second capacitor connected to the virtual ground node; wherein the low-frequency ripple current suppression circuit receives a DC current having a ripple component, and absorbs the ripple component by the first boost circuit and the second boost circuit. 2.The low-frequency ripple current suppression circuit of claim 1, further comprising: a filter circuit, comprising: a first filter capacitor having a first end and a second end, the first end of the first filter capacitor connected to the first DC side, the second end of the first filter capacitor connected to the virtual ground node; and a second filter capacitor having a first end and a second end, the first end of the second filter capacitor connected to the second DC side, the second end of the second filter capacitor connected to the virtual ground node. 3.The low-frequency ripple current suppression circuit of claim 1, wherein the first switch and the second switch of the first switch group are synchronously complementary on and off, and the third switch and the fourth switch of the second switch group are synchronously complementary on and off. 4.The low-frequency ripple current suppression circuit of claim 1, wherein the first switch and the second switch of the first switch group and the third switch and the fourth switch of the second switch group are transistors. 5.The low-frequency ripple current suppression circuit of claim 1, wherein the first switch of the first switch group and the third switch of the second switch group are transistors, and the second switch of the first switch group and the fourth switch of the second switch group are diodes.

6. The low frequency ripple current suppression circuit of claim 1, wherein the first switch of the first switch set and the third switch of the second switch set are synchronously turned on and turned off.

7. The low frequency ripple current suppression circuit of claim 1, wherein the first switch of the first switch set and the third switch of the second switch set are non-synchronously turned on and turned off.

8. A power system with low frequency ripple current suppression function, comprising: three single-phase AC-to-DC conversion circuits, each of the single-phase AC-to-DC conversion circuits correspondingly coupled to each phase of a three-phase AC power source, and the outputs of the three single-phase AC-to-DC conversion circuits connected to an output node and output DC current; and a low frequency ripple current suppression circuit connected to the output node, comprising: a first boost circuit comprising a first inductor, a first switch set, and a first capacitor; the first switch set comprising a first switch and a second switch; the first inductor connected to the first switch at a first common node, and connected between a first DC side and an equal potential node; the second switch connected in series with the first capacitor, and connected between the first common node and the equal potential node; and a second boost circuit comprising a second inductor, a second switch set, and a second capacitor; the second switch set comprising a third switch and a fourth switch; the second inductor connected to the third switch at a second common node, and connected between a second DC side and the equal potential node; the fourth switch connected in series with the second capacitor, and connected between the second common node and the equal potential node.

9. The power system with low frequency ripple current suppression function of claim 8, wherein the first inductor has a first end and a second end, the first end of the first inductor connected to the first DC side; the first switch has a first end and a second end, the first end of the first switch connected to the second end of the first inductor, the second end of the first switch connected to the equal potential node; the second switch has a first end and a second end, the first end of the second switch connected to the second end of the first inductor; the first capacitor has a first end and a second end, the first end of the first capacitor connected to the second end of the second switch, the second end of the first capacitor connected to the equal potential node; the second inductor has a first end and a second end, the first end of the second inductor connected to the second DC side; the third switch has a first end and a second end, the first end of the third switch connected to the second end of the second inductor, the second end of the third switch connected to the equal potential node; the fourth switch has a first end and a second end, the first end of the fourth switch connected to the second end of the second inductor; the second capacitor has a first end and a second end, the first end of the second capacitor connected to the second end of the fourth switch, the second end of the second capacitor connected to the equal potential node. ​ 10. The power system with low frequency ripple current suppression function of claim 8, wherein as the load supplied by the three single-phase AC to DC conversion circuits decreases, portions of the three single-phase AC to DC conversion circuits are turned off.

11. The power system with low frequency ripple current suppression function of claim 10, further comprising: a power controller receiving information of the load; wherein based on the decrease of the load, the power controller is configured to turn off portions of the three single-phase AC to DC conversion circuits and to activate the low frequency ripple current suppression circuit.

12. The power system with low frequency ripple current suppression function of claim 8, wherein the three single-phase AC to DC conversion circuits are configured to charge a battery of an electric vehicle.

13. The power system with low frequency ripple current suppression function of claim 8, wherein the three single-phase AC to DC conversion circuits are configured in a delta connection configuration or the three single-phase AC to DC conversion circuits are configured in a star connection configuration.

14. The power system with low frequency ripple current suppression function of claim 8, wherein the first switch and the second switch of the first switch set are synchronously complementary on and off; and the third switch and the fourth switch of the second switch set are synchronously complementary on and off.

15. The power system with low frequency ripple current suppression function of claim 8, wherein the first switch of the first switch set and the third switch of the second switch set are synchronously on and off. ​ ​

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