Charging system, power supply system and dual-mode power conversion circuit therein

Abstract

A charging system, a power supply system and a dual-mode power conversion circuit therein. The power conversion circuit includes an N-stage PWM power converter and a capacitor switching power converter. The N-stage PWM power converter includes a plurality of shared switches shared with the capacitor switching power converter and a plurality of PWM switches. The plurality of shared switches and the plurality of PWM switches periodically switch an inductor and a capacitor in an N-stage PWM mode to convert between a first power source and a second power source in an N-stage PWM manner. The capacitor switching power converter includes a plurality of shared switches and a plurality of auxiliary switches. The plurality of shared switches and the plurality of auxiliary switches periodically switch the capacitor in a capacitor conversion mode to convert between the first power source and the second power source in a capacitor conversion manner. In the capacitor conversion mode, part of the plurality of PWM switches are constantly non-conducting, so that one end of the inductor is floating.

Description

TECHNICAL FIELD

[0001] The present invention relates to a charging system, in particular, to a high efficiency charging system with both N-stage PWM power converter and capacitor switching power converter. The present invention also relates to a power conversion circuit for high efficiency charging system. BACKGROUND

[0002] Figure 1 A prior art charging system 100 is shown, which includes a PWM (Pulse Width Modulation) circuit 120, a capacitor current boost circuit 130, and load switches SP1-SP4. A power supply unit 10 sends a DC power source VDC (which can be a constant voltage or a constant current), and the charging system 100 can determine to select the PWM circuit 120 to switch the inductor L in a pulse width modulation manner to convert the DC power source VDC into an output power source VO to charge the battery 40, or to select the capacitor current boost circuit 130 to switch the capacitor CF in a capacitor voltage division manner (corresponding to current boost) to convert the DC power source VDC into the output power source VO to charge the battery 40, for example, according to the voltage relationship and charging state of the DC power source VDC and the battery 40.

[0003] Figure 1 The prior art charging system 100 has the disadvantage of requiring two independent power conversion circuits (120, 130) and corresponding multiple load switches (SP1-SP4), which is costly, and generally, the PWM circuit 120 is a 2-stage PWM power converter, which is less efficient.

[0004] Figure 2 Another prior art charging system 200 is shown, which switches the inductor L and the capacitor CF through switches S1-S4 to perform power conversion in a 3-stage PWM power conversion manner in a 3-stage PWM mode, and in a capacitor conversion mode, the inductor L is shorted through a bypass switch SB, and the capacitor CF is switched through switches S1-S4 to multiply the input current in a capacitor voltage division manner.

[0005] Figure 2 The prior art charging system 200 has the disadvantage that in the capacitor conversion mode, the conduction loss of the bypass switch SB increases with the increase of the charging current, which reduces the efficiency of power conversion.

[0006] The present application is to solve the above problems of the prior art, and provides a dual-mode power conversion circuit, which has an N-stage PWM power converter and a capacitor switching power converter sharing some switches. The power conversion circuit can adaptively control the N-stage PWM power converter and the capacitor to be combined in an N-stage PWM mode or operated in a capacitor conversion mode according to the relationship between a direct current power source and a charging power source, thereby improving the power conversion efficiency of the overall charging system through a flexible conversion mode. SUMMARY

[0007] In one aspect, the present application provides a power conversion circuit for converting a first power source to a second power source or converting the second power source to the first power source. The power conversion circuit includes an N-stage PWM power converter for switching an inductor and at least one capacitor to perform conversion between the first power source and the second power source in an N-stage PWM mode, and a capacitor switching power converter for switching the capacitor to perform conversion between the first power source and the second power source in a capacitor conversion mode. The N-stage PWM power converter includes shared switches shared with the capacitor switching power converter, and PWM switches. The shared switches and the PWM switches periodically switch the inductor and the capacitor in the N-stage PWM mode to perform conversion between the first power source and the second power source in an N-stage PWM manner, where N is an integer greater than or equal to 3. The capacitor switching power converter includes the shared switches and auxiliary switches. The shared switches and the auxiliary switches periodically switch the capacitor in the capacitor conversion mode to perform conversion between the first power source and the second power source in a capacitor power conversion manner. In the capacitor conversion mode, at least part of the PWM switches are constantly non-conductive, so that one end of the inductor is floating.

[0008] In one embodiment, in the N-stage PWM mode, the auxiliary switches are constantly non-conductive, so that the capacitor is constantly electrically disconnected from one of the first power source or the second power source.

[0009] In one embodiment, the N-order PWM power converter comprises: a plurality of upper bridge switches coupled in series between the first power source and a switching node, wherein the plurality of upper bridge switches are sequentially coupled to corresponding at least one upper bridge intermediate node; and a plurality of lower bridge switches coupled in series between the switching node and a ground potential, wherein the plurality of lower bridge switches are sequentially coupled to corresponding at least one lower bridge intermediate node; wherein the capacitor switching power converter comprises: a portion of the plurality of upper bridge switches; a portion of the plurality of lower bridge switches, wherein the portion of the plurality of upper bridge switches and the portion of the plurality of lower bridge switches correspond to the plurality of shared switches; an upper bridge sub-assist switch having a first end coupled to the second power source and a second end coupled to a corresponding one of the upper bridge intermediate nodes; and a lower bridge sub-assist switch having a first end coupled to the second power source and a second end coupled to a corresponding one of the lower bridge intermediate nodes; wherein the upper bridge sub-assist switch and the lower bridge sub-assist switch correspond to the assist switch; wherein the inductor is coupled between the switching node and the second power source; wherein the capacitor has a first end coupled to a corresponding one of the upper bridge intermediate nodes and a second end coupled to a corresponding one of the lower bridge intermediate nodes; wherein in the N-order PWM mode, the plurality of upper bridge switches and the plurality of lower bridge switches periodically switch the capacitor to generate an N-order voltage at the switching node, thereby causing the inductor to convert between the first power source and the second power source in an N-order PWM manner; and wherein in the capacitor conversion mode, the upper bridge sub-assist switch, the lower bridge sub-assist switch, and the plurality of shared switches periodically switch the capacitor, thereby causing the capacitor to convert the first power source to the second power source in a capacitor voltage division manner or to convert the second power source to the first power source in a charge pump manner.

[0010] In one embodiment, in the N-order PWM mode, the upper bridge sub-assist switch and the lower bridge sub-assist switch are constantly non-conductive, such that the capacitor is constantly electrically disconnected from the second power source.

[0011] In one embodiment, in the capacitor conversion mode, at least one of the plurality of upper bridge switches other than the plurality of shared switches is constantly non-conductive, and at least one of the plurality of lower bridge switches other than the plurality of shared switches is constantly non-conductive, such that one end of the inductor coupled to the switching node is floating.

[0012] In one embodiment, in the N-order PWM mode, a ratio of a first voltage of the first power source to a second voltage of the second power source is related to a duty cycle corresponding to the N-order voltage.

[0013] In one embodiment, in the capacitor conversion mode, a ratio of a first voltage of the first power source to a second voltage of the second power source is M, where M is a real number greater than 1.

[0014] In an embodiment, M is equal to N-1.

[0015] In an embodiment, the power conversion circuit is configured to convert the first power to the second power, wherein in the capacitor conversion mode, a first current of the first power is constant, such that a second current of the second power is constant and M times the first current.

[0016] In an embodiment, in the capacitor conversion mode, an upper bridge switch of the plurality of shared switches comprises a plurality of upper bridge sub-shared switches in parallel to each other, wherein during a soft start period, the plurality of upper bridge sub-shared switches are gradually switched on according to a preset timing; and / or a lower bridge switch of the plurality of shared switches comprises a plurality of lower bridge sub-shared switches in parallel to each other, wherein during the soft start period, the plurality of lower bridge sub-shared switches are gradually switched on according to a preset timing; thereby reducing an inrush current during the soft start period.

[0017] In an embodiment, the plurality of upper bridge switches comprises a first upper bridge switch and a second upper bridge switch, sequentially connected in series between the first power and the switching node, wherein the first upper bridge switch and the second upper bridge switch are coupled to each other at an upper bridge intermediate node; the plurality of lower bridge switches comprises a first lower bridge switch and a second lower bridge switch, sequentially connected in series between the ground potential and the switching node, wherein the first lower bridge switch and the second lower bridge switch are coupled to each other at a lower bridge intermediate node; the first upper bridge switch and the first lower bridge switch correspond to the plurality of shared switches; wherein the upper bridge sub-assist switch is coupled between the second power and the upper bridge intermediate node, the lower bridge sub-assist switch is coupled between the second power and the lower bridge intermediate node; wherein the capacitor is coupled between the upper bridge intermediate node and the lower bridge intermediate node.

[0018] In an embodiment, the power conversion circuit is configured to repeatedly switch in a switching period, wherein N is equal to 3, in a corresponding 3-order PWM mode, in a first time period of the switching period, the first upper bridge switch and the second lower bridge switch are on, the second upper bridge switch and the first lower bridge switch are off, and in a second time period of the switching period, the first lower bridge switch and the second lower bridge switch are on, the first upper bridge switch and the second upper bridge switch are off, and in a third time period of the switching period, the second upper bridge switch and the first lower bridge switch are on, the first upper bridge switch and the second lower bridge switch are off, and in a fourth time period of the switching period, the first upper bridge switch and the second upper bridge switch are on, and the first lower bridge switch and the second lower bridge switch are off, thereby the voltage of the switching node is periodically switched between the first voltage, the ground potential and 1 / 2 of the first voltage; wherein the upper bridge sub-assist switch and the lower bridge sub-assist switch are constantly off, such that the capacitor is constantly off at the second power.

[0019] In one embodiment, the power conversion circuit repeatedly switches with a switching period, where M equals 2, in the capacitor conversion mode, in a first time period of the switching period, the first upper bridge switch and the lower bridge sub auxiliary switch are turned on, the upper bridge sub auxiliary switch and the first lower bridge switch are not turned on, and in a second time period of the switching period, the upper bridge sub auxiliary switch and the first lower bridge switch are turned on, the first upper bridge switch and the lower bridge sub auxiliary switch are not turned on, thereby the first end of the capacitor is periodically switched between the first voltage and the second voltage, and the second end of the capacitor is periodically switched between the second voltage and the ground potential; wherein the second upper bridge switch and the second lower bridge switch are constantly not turned on, so that one end of the inductor is floating.

[0020] In another aspect, the present application provides a charging system, comprising: a power transmitting unit for generating a direct current power according to an input power; and a charging circuit removably connected with the power transmitting unit for converting the direct current power to generate a charging power to charge a battery; wherein the charging circuit corresponds to the power conversion circuit of any one of the above; wherein the first power corresponds to the direct current power, the second power corresponds to the charging power, or wherein the second power corresponds to the direct current power, the first power corresponds to the charging power.

[0021] In another aspect, the present application provides a power supply system, comprising: a battery for providing an electric energy; and a power supply circuit coupled with the battery for converting the electric energy to generate a power supply power to supply power to a load; wherein the power supply circuit corresponds to the power conversion circuit of any one of the above; wherein the first power corresponds to the electric energy, the second power corresponds to the power supply power, or wherein the second power corresponds to the electric energy, the first power corresponds to the power supply power.

[0022] The purposes, technical contents, characteristics and effects of the present application will be more apparent from the following detailed description of specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A circuit block diagram of a prior art charging system is shown.

[0024] Figure 2 A circuit schematic diagram of a prior art charging system is shown.

[0025] Figure 3 A schematic diagram of a specific embodiment of the power conversion circuit of the present application is shown.

[0026] Figures 4A-4C Schematic diagrams of specific embodiments of the charging system of the present application are shown.

[0027] Figure 5 A graph showing a charging profile of an embodiment of the charging system according to the present application.

[0028] Figure 6 A graph showing an efficiency profile of an embodiment of the power conversion circuit according to the present application.

[0029] Figure 7 A schematic diagram showing another specific embodiment of the power conversion circuit of the present application.

[0030] Figure 8 A schematic diagram showing yet another specific embodiment of the power conversion circuit of the present application.

[0031] Figure 9A A block diagram showing an embodiment of the power conversion circuit of the present application.

[0032] Figure 9B A schematic diagram showing a specific embodiment of the charging system of the present application.

[0033] Figure 10 A schematic diagram showing another specific embodiment of the power conversion circuit of the present application.

[0034] Figure 11 A graph showing an operating waveform of an embodiment of the charging system according to the present application.

[0035] Figure 12 A graph showing an efficiency profile of an embodiment of the power conversion circuit according to the present application.

[0036] Legend of Symbols

[0037] 10: power transmitting unit

[0038] 100, 200, 1004A, 1004B, 1010: charging system

[0039] 1004C: power supply system

[0040] 120: PWM circuit

[0041] 130: capacitance boost circuit

[0042] 300, 700, 800, 900, 1000: power conversion circuit

[0043] 320: 3rd order PWM power converter

[0044] 330: capacitance switching power converter

[0045] 40: battery

[0046] 50: load

[0047] 720: 4th order PWM power converter

[0048] 730: capacitor-switched power converter

[0049] 820, 920: Nth order PWM power converter

[0050] 830, 930: capacitor-switched power converter

[0051] CF: capacitor

[0052] CF[1] - CF[N-2]: capacitor

[0053] I1: first current

[0054] I2: second current

[0055] L: inductor

[0056] LX: switching node

[0057] NU[1] - NU[N-2]: upper bridge intermediate node

[0058] NL[1] - NL[N-2]: lower bridge intermediate node

[0059] QA: auxiliary switch

[0060] QC: shared switch

[0061] QP: PWM switch

[0062] QL[1] - QL[N-1]: lower bridge switch

[0063] QL[1,1] - QL[1,k]: lower bridge sub-shared switch

[0064] QLA: lower bridge sub-auxiliary switch

[0065] QU[1] - QU[N-1]: upper bridge switch

[0066] QU[1,1] - QU[1,k]: upper bridge sub-shared switch

[0067] QUA: upper bridge sub-auxiliary switch

[0068] S1 - S4: switch

[0069] SB: bypass switch

[0070] SP1 - SP4: load switch

[0071] T1 - Tk: time period

[0072] V1: first voltage

[0073] V2: second voltage

[0074] VDC: direct current power supply

[0075] VIN: input power supply

[0076] VF: forward voltage

[0077] VO: output power supply

[0078] VT: target voltage DETAILED DESCRIPTION

[0079] The figures in the present disclosure are schematic and mainly intended to represent the coupling relationship between circuits and the relationship between signal waveforms, and the circuits, signal waveforms and frequencies are not drawn in proportion.

[0080] Figure 3 A schematic diagram showing a specific embodiment of the power conversion circuit of the present disclosure (power conversion circuit 300). The power conversion circuit 300 is used to convert a first power supply (corresponding to a first voltage V1, a first current I1) into a second power supply, or to convert a second power supply (corresponding to a second voltage V2, a second current I2) into a first power supply. The power conversion circuit 300 includes a 3-stage PWM power converter 320 and a capacitor switching power converter 330.

[0081] The 3-stage PWM power converter 320 is used to switch the inductor L and at least one capacitor (e.g. CF) to perform conversion between the first power supply and the second power supply in a 3-stage PWM mode. The capacitor switching power converter 330 is used to switch the capacitor CF to perform conversion between the first power supply and the second power supply in a capacitor conversion mode.

[0082] In this embodiment, the 3-stage PWM power converter 320 includes a plurality of upper bridge switches and a plurality of lower bridge switches. The plurality of upper bridge switches includes a first upper bridge switch QU[1] and a second upper bridge switch QU[2], which are sequentially connected between the first power supply and a switching node LX, wherein the first upper bridge switch QU[1] and the second upper bridge switch QU[2] are coupled to each other at an upper bridge intermediate node NU[1]. The plurality of lower bridge switches includes a first lower bridge switch QL[1] and a second lower bridge switch QL[2], which are sequentially connected between a ground potential and the switching node LX, wherein the first lower bridge switch QL[1] and the second lower bridge switch QL[2] are coupled to each other at a lower bridge intermediate node NL[1]. In this embodiment, the inductor L is coupled between the switching node LX and the second power supply.

[0083] On the other hand, the capacitor-switching power converter 330 includes the first upper bridge switch QU[1], the first lower bridge switch QL[1], the upper bridge sub auxiliary switch QUA, and the lower bridge sub auxiliary switch QLA. In other words, the 3-stage PWM power converter 320 and the capacitor-switching power converter 330 share the first upper bridge switch QU[1] and the first lower bridge switch QL[1]. In the present embodiment, the upper bridge sub auxiliary switch QUA is coupled between the second power supply and the upper bridge intermediate node NU[1], the lower bridge sub auxiliary switch QLA is coupled between the second power supply and the lower bridge intermediate node NL[1], and the capacitor CF is coupled between the upper bridge intermediate node NU[1] and the lower bridge intermediate node NL[1]. The above-mentioned upper bridge switches, lower bridge switches, and auxiliary switches are respectively controlled by corresponding control signals SU[1]-SU[2], SL[1]-SL[2], SUA, and SLA.

[0084] Please continue to refer to Figure 3 In the 3-stage PWM mode, the power conversion circuit 300 is controlled by the control signals SU[1]-SU[2] to repeatedly switch in a switching period. In a first time period of the switching period, the first upper bridge switch QU[1] and the second lower bridge switch QL[2] are turned on, the second upper bridge switch QU[2] and the first lower bridge switch QL[1] are not turned on, and in a second time period of the switching period, the first lower bridge switch QL[1] and the second lower bridge switch QL[2] are turned on, the first upper bridge switch QU[1] and the second upper bridge switch QU[2] are not turned on, and in a third time period of the switching period, the second upper bridge switch QU[2] and the first lower bridge switch QL[1] are turned on, the first upper bridge switch QU[1] and the second lower bridge switch QL[2] are not turned on, and in a fourth time period of the switching period, the first upper bridge switch QU[1] and the second upper bridge switch QU[2] are turned on, the first lower bridge switch QL[1] and the second lower bridge switch QL[2] are not turned on, so that the voltage of the switching node LX is periodically switched between three different voltage levels, the first voltage V1, the ground potential, and 1 / 2 of the first voltage V1, to achieve 3-stage PWM power conversion.

[0085] It should be noted that in the 3-stage PWM mode, the ratio of the first voltage V1 of the first power supply to the second voltage V2 of the second power supply is related to the duty cycle corresponding to the above-mentioned 3-stage voltage. In addition, the first time period, the second time period, the third time period, and the fourth time period of the above-mentioned switching period can be arranged according to actual needs, and the above-mentioned switching sequence in the switching period is not used to limit the present application. In addition, it should be noted that in the 3-stage PWM mode, the upper bridge sub auxiliary switch QUA and the lower bridge sub auxiliary switch QLA are always not turned on, so that the capacitor CF is always not electrically connected to the second power supply.

[0086] Please continue to refer to Figure 3In the capacitor conversion mode, the power conversion circuit 300 repeatedly switches in a switching period. In a first time period of the switching period, the first upper bridge switch QU[1] and the lower bridge sub auxiliary switch QLA are turned on, the upper bridge sub auxiliary switch QUA and the first lower bridge switch QL[1] are not turned on. In a second time period of the switching period, the upper bridge sub auxiliary switch QUA and the first lower bridge switch QL[1] are turned on, the first upper bridge switch QU[1] and the lower bridge sub auxiliary switch QLA are not turned on. Thus, the first end of the capacitor CF is periodically switched between the first voltage V1 and the second voltage V2, and the second end of the capacitor CF is periodically switched between the second voltage V2 and the ground potential. The ratio of the first voltage V1 to the second voltage V2 is 2, and the ratio of the second current I2 to the first current I1 is also 2. The switching period in the capacitor conversion mode and the switching period in the 3-order PWM mode can be the same or different.

[0087] It should be noted that in the capacitor conversion mode, the second upper bridge switch QU[2] and the second lower bridge switch QL[2] are always not turned on, so that the switching node LX is open, that is, the end of the inductor L coupled to the switching node LX is floating.

[0088] Figure 4A A schematic diagram (charging system 1004A) of a specific embodiment of the charging system of the present application is shown. The charging system 1004A includes a power transmitting unit 10 and a power conversion circuit 300. The power transmitting unit 10 is used to generate a first power according to an input power (such as VIN). In an embodiment, the first power is a direct current power.

[0089] In an embodiment, the power transmitting unit 10 can be an alternating current-direct current conversion circuit such as a mobile adapter, in which case the input power VIN is an alternating current. In another embodiment, the power transmitting unit 10 can also be a direct current-direct current conversion circuit such as a mobile power supply, in which case the input power VIN can be a direct current provided by another battery, for example. In an embodiment, the power transmitting unit 10 can comply with the USB PD specification, for example, and can output a first power in the form of an adjustable constant voltage or constant current according to requirements.

[0090] The power conversion circuit 300 is removably connected to the power transmitting unit 10, for example, by a connector and a cable, and is used to convert the first power to generate a charging power for charging the battery 40. In the present embodiment, the charging power corresponds to the second power (i.e., the second voltage V2 corresponds to the charging voltage, and the second current I2 corresponds to the charging current). In other words, in the present embodiment, the power conversion circuit 300 performs a step-down operation in the 3-stage PWM mode or a capacitive voltage dividing (corresponding to current boosting) operation in the capacitive conversion mode. In one embodiment, the first current I1 generated by the power transmitting unit 10 is constant, so that the second current I2 is also constant and is twice the first current I1 (i.e., current boosting).

[0091] Figure 4B A schematic diagram showing another embodiment of the charging system of the present application (charging system 1004B) is shown. The charging system 1004B is similar to the charging system 1004A, except that in the charging system 1004B, the second power corresponds to a DC power, and the first power corresponds to a charging power. In other words, in the present embodiment, the power conversion circuit 300 performs a step-up operation in the 3-stage PWM mode or a charge pump (corresponding to current sinking) operation in the capacitive conversion mode to generate the first power for charging the battery 40. In one embodiment, the second current I2 generated by the power transmitting unit 10 is constant, so that the first current I1 is also constant and is half of the second current I2 (i.e., current sinking). In one embodiment, the second voltage V2 generated by the power transmitting unit 10 is constant, so that the first voltage V1 is also constant and is twice the second voltage V2 (i.e., voltage boosting).

[0092] Figure 4C A schematic diagram showing one embodiment of the power supply system of the present application (power supply system 1004C) is shown. The power supply system 1004C is similar to the charging system 1004B, except that in the present embodiment, the battery 40 is used to provide the second power, i.e., the battery voltage corresponds to the second voltage V2, and the battery current corresponds to the second current I2. The power conversion circuit 300 performs a step-up operation in the 3-stage PWM mode or a charge pump (corresponding to current sinking) operation in the capacitive conversion mode to convert the second power provided by the battery 40 to generate the first power for powering the load 50. The power supply system 1004C, for example, corresponds to a battery power supply system according to the USB OTG specification. In one embodiment, the second voltage V2 generated by the battery 40 is constant, so that the first voltage V1 is also constant and is twice the second voltage V2 (i.e., voltage boosting).

[0093] Figure 5A charging profile corresponding to an embodiment of the charging system (e.g. 1004A) is shown, where the solid line is the direct current (corresponding to the first current I1), the dashed line is the charging current (corresponding to the second current I2), and the thick solid line is the battery voltage (corresponding to the second voltage V2). The power conversion circuit (e.g. 300) of the present application can support the requirements of various stages of battery charging, such as Figure 5 As shown, during the pre-charge stage (t1-t2), the power conversion circuit 300 can operate in the 3-step PWM mode to output a lower constant charging current (e.g. less than 3A) to charge the battery 40.

[0094] During the constant current charging stage (t2-t4), the power conversion circuit 300 can operate in the capacitor conversion mode to charge the battery 40 with a larger charging current (e.g. between 3A and 8A). In particular, in this embodiment, the battery 40 is charged with a constant charging current (I2) that is, for example, twice the direct current (I1). It is noted that during this period, in an embodiment, the direct current (I1) provided by the power supply unit 10 can be adaptively reduced gradually as the battery voltage (V2) reaches a target voltage VT.

[0095] During the termination charging stage (t4-t5), the power conversion circuit 300 can operate in the 3-step PWM mode to output a constant charging voltage (V2) that is close to the target voltage VT to charge the battery 40.

[0096] Figure 6 An efficiency profile of an embodiment of the power conversion circuit according to the present application is shown, in particular, the embodiment corresponds to the efficiency comparison between, for example, the embodiment of FIG. 4 (solid line) and Figure 2 the prior art (dashed line), as shown, due to the prior art, the inductor L needs to be shorted by the bypass switch SB to operate in the capacitor conversion mode, however, the conduction loss of the bypass switch SB can increase as the charging current (i.e. load) increases, thus, in the case of high current, the efficiency of the power conversion can be reduced, in comparison, the present application does not need the bypass switch SB in the capacitor conversion mode, but instead controls one end of the inductor L to be floating, thus, especially in the case of high current, the charging system and the power conversion circuit of the present application can have higher efficiency of power conversion. Figure 2

[0097] Figure 7 ​FIG. 7 shows a schematic diagram of another embodiment of the power conversion circuit (power conversion circuit 700) of the present application. The power conversion circuit 700 comprises a 4-step PWM power converter 720 and a capacitor switching power converter 730. The power conversion circuit 700 is similar to the power conversion circuit 300 as previously described, except that the 4-step PWM power converter 720 and the capacitor switching power converter 730 comprise more upper bridge switches and lower bridge switches (i.e., QU[3] and QL[3]) for switching two capacitors CF[1] and CF[2], in one embodiment, 4-step PWM power conversion and 3x voltage or 3x current capacitor switching power conversion operations can be achieved.

[0098] In particular, in this embodiment, the 4-step PWM power converter 720 and the capacitor switching power converter 730 share the upper bridge switches QU[1]-QU[2] and the lower bridge switches QL[1]-QL[2], and the upper auxiliary sub-switch QUA is coupled between the second power source and the upper bridge intermediate node NU[2], and the lower auxiliary sub-switch QLA is coupled between the second power source and the lower bridge intermediate node NL[2], the capacitor CF[1] is coupled between the upper bridge intermediate node NU[1] and the lower bridge intermediate node NL[1], and the capacitor CF[2] is coupled between the upper bridge intermediate node NU[2] and the lower bridge intermediate node NL[2]. The upper bridge switches, the lower bridge switches, and the auxiliary switches are controlled by the corresponding control signals SU[1]-SU[3], SL[1]-SL[3], SUA, and SLA, respectively.

[0099] In one embodiment, in the 4-step PWM mode, the voltage of the switching node LX is periodically switched between the first voltage VI, the ground potential, 2 / 3 of the first voltage VI, and 2 / 3 of the first voltage VI, to achieve 4-step PWM power conversion. In the capacitor conversion mode, the shared switches and the auxiliary sub-switches can be switched by capacitor voltage division or charge pump to achieve 3x voltage or 3x current capacitor switching power conversion operations. In one embodiment, under periodic switching in steady state, the capacitor CF[1] has a voltage across it of 2 / 3 of the first voltage VI, and the capacitor CF[2] has a voltage across it of 1 / 3 of the first voltage VI.

[0100] Similarly to the previous embodiments, in the 4-step PWM mode, the upper auxiliary sub-switch QUA and the lower auxiliary sub-switch QLA are constantly non-conductive, so that the capacitors CF[1] and CF[2] are constantly not electrically connected to the second power source, and in the capacitor conversion mode, the third upper bridge switch QU[3] and the third lower bridge switch QL[3] are constantly non-conductive, so that the switching node LX is open, i.e., the inductor L is coupled to one end of the switching node LX is floating.

[0101] Figure 8Fig. 8 shows a schematic diagram of another embodiment of the power conversion circuit (power conversion circuit 800) of the present application. According to the foregoing embodiments, the present application can be extended to a wider application, the power conversion circuit 800 comprises an N-stage PWM power converter 820 and a capacitor-switching power converter 830. The N-stage PWM power converter 820 comprises a plurality of upper bridge switches QU[1]~QU[N-1] coupled in series with each other between a first power source and a switching node LX, wherein the plurality of upper bridge switches QU[1]~QU[N-1] are sequentially and adjacently coupled to corresponding upper bridge intermediate nodes NU[1]~NU[N-2].

[0102] a plurality of lower bridge switches QL[1]~QL[N-1] coupled in series between the switching node LX and a ground potential, wherein the plurality of lower bridge switches QL[1]~QL[N-1] are sequentially and adjacently coupled to corresponding lower bridge intermediate nodes NL[1]~NL[N-2].

[0103] The capacitor-switching power converter 830 comprises the upper bridge switches QU[1]~QU[N-2] and the lower bridge switches QL[1]~QL[N-2] shared with the N-stage PWM power converter 820, an upper bridge sub- auxiliary switch QUA and a lower bridge sub-auxiliary switch QLA. The first end of the upper bridge sub-auxiliary switch QUA is coupled to a second power source, and the second end thereof is coupled to the corresponding upper bridge intermediate node NU[N-2]. The first end of the lower bridge sub-auxiliary switch QLA is coupled to the second power source, and the second end thereof is coupled to the corresponding lower bridge intermediate node NL[N-2].

[0104] Please refer to Figure 8 , an inductor L is coupled between the switching node LX and the second power source, and capacitors CF[1]~CF[N-2] each have a first end coupled to a corresponding upper bridge intermediate node NU[1]~NU[N-2], respectively, and each have a second end coupled to a corresponding lower bridge intermediate node NL[1]~NL[N-2], respectively.

[0105] In the N-stage PWM mode, the plurality of upper bridge switches QU[1]~QU[N-1] and the plurality of lower bridge switches QL[1]~QL[N-1] periodically switch the capacitors CF to generate an N-stage voltage at the switching node LX, thereby causing the inductor L to convert between the first power source and the second power source in an N-stage PWM manner; wherein the N-stage voltage comprises a first voltage V1 and a ground potential, and N-2 voltages between the first voltage V1 and the ground potential. Wherein N is an integer greater than or equal to 3.

[0106] In the capacitor conversion mode, the upper bridge sub auxiliary switch QUA, the upper bridge switches QU[1]-QU[N-2], the lower bridge sub auxiliary switch QLA and the lower bridge switches QL[1]-QL[N-2] periodically switch the coupling relationship of the capacitors CF[1]-CF[N-2], thereby causing the capacitors CF[1]-CF[N-2] to convert the first power supply into the second power supply in a capacitive voltage division manner, or to convert the second power supply into the first power supply in a charge pump manner.

[0107] In an embodiment, in the capacitor conversion mode, the ratio of the first voltage VI of the first power supply to the second voltage V2 of the second power supply is M, where M is a real number greater than 1. In a preferred embodiment, M is a positive integer greater than 1.

[0108] Similarly to the foregoing embodiments, in an embodiment, in the N-order PWM mode, the upper bridge sub auxiliary switch QUA and the lower bridge sub auxiliary switch QLA are constantly non-conductive, causing the capacitors CF to be constantly electrically disconnected from the second power supply. On the other hand, in the capacitor conversion mode, the upper bridge switch QU[N-1] and the lower bridge switch QL[N-1] are constantly non-conductive, thereby causing the switching node LX to be open-circuited, i.e., causing one end of the inductor L coupled to the switching node LX to be floating.

[0109] It should be noted that in other embodiments, the second end of the upper bridge sub auxiliary switch QUA described above can be coupled to a corresponding other upper bridge intermediate node NU[i], where i is an integer between 1 and N-2. And the second end of the lower bridge sub auxiliary switch QLA can be coupled to a corresponding other lower bridge intermediate node NL[i]. Thus, optionally, in the capacitor conversion mode, capacitive power conversion can be performed with fewer capacitors. In other words, in this case, the number of upper bridge switches and lower bridge switches shared by the N-order PWM power converter 820 and the capacitor switching power converter 830 will correspondingly decrease. In one aspect, in the capacitor conversion mode, at least one of the upper bridge switches other than the foregoing shared upper bridge switches is constantly electrically disconnected, and at least one of the lower bridge switches other than the foregoing shared lower bridge switches is constantly electrically disconnected, causing one end of the inductor L coupled to the switching node LX to be floating.

[0110] Figure 9A A block diagram showing an embodiment of a power conversion circuit of the present application. According to the present application, the foregoing embodiments such as Figure 3 , Figure 7 and Figure 8 can be extended to a more general embodiment of a power conversion circuit as shown in Figure 9A .

[0111] As shown in Figure 9AAs shown, the power conversion circuit 900 is used to convert the first power supply to the second power supply or the second power supply to the first power supply. The power conversion circuit 900 includes an N-order PWM power converter 920 and a capacitor-switched power converter 930.

[0112] The N-order PWM power converter 920 is used in N-order PWM mode to switch inductor L and at least one capacitor (e.g., CF) to switch between a first power supply and a second power supply. The capacitor-switching power converter 930 is used in capacitor-switching mode to switch capacitor CF to switch between a first power supply and a second power supply.

[0113] In one embodiment, the N-order PWM power converter 920 includes a plurality of shared switches QC and a plurality of PWM switches QP shared with the capacitor switching power converter 930. In the N-order PWM mode, the plurality of shared switches QC and the plurality of PWM switches QP periodically switch the inductor L and the capacitor CF to perform the conversion between the first power supply and the second power supply in an N-order PWM manner, where N is an integer greater than or equal to 3.

[0114] In one embodiment, the capacitor switching power converter 930 includes the aforementioned plurality of shared switches QC and plurality of auxiliary switches QA, wherein in capacitor switching mode, the plurality of shared switches QC and the plurality of auxiliary switches QA periodically switch capacitors CF to perform the switching between a first power supply and a second power supply in a capacitor-type power conversion manner.

[0115] Figure 9A The shared switch QC shown can, for example, correspond to Figure 3 The upper bridge switch QU[1] and the lower bridge switch QL[1], or corresponding to Figure 7 The upper bridge switch QU[1]~QU[2] and the lower bridge switch QL[1]~QL[2], or corresponding to Figure 8 The upper bridge switch QU[1]~QU[N-2] and the lower bridge switch QL[1]~QL[N-2]. The upper bridge switch that is used as a shared switch can be referred to as the upper bridge sub-shared switch, and the lower bridge switch that is used as a shared switch can be referred to as the lower bridge sub-shared switch.

[0116] also, Figure 9A The PWM switch QP shown can, for example, correspond to Figure 3 The upper bridge switch QU[2] and the lower bridge switch QL[2], or corresponding to Figure 7 The upper bridge switch QU[3] and the lower bridge switch QL[3], or corresponding to Figure 8 The upper bridge switch QU[N-1] and the lower bridge switch QL[N-1], in other words, the PWM switch QP corresponds to the non-shared switch in the N-order PWM power converter 920.

[0117] Furthermore, Figure 9A The auxiliary switch QA shown can, for example, correspond to Figure 3 , Figure 7 and Figure 8 The upper bridge auxiliary switch QUA and the lower bridge auxiliary switch QLA.

[0118] In one embodiment, in capacitor switching mode, the ratio of the first voltage V1 of the first power supply to the second voltage V2 of the second power supply is M. In one embodiment, through appropriate capacitor and switch configuration, M is a real number greater than 1. In another embodiment, M is an integer greater than 1.

[0119] Figure 9B This diagram illustrates a specific embodiment of the charging system of the present invention. Similar to the embodiment in FIG4, in this embodiment, the power transmitting unit 10 is used to generate a first power source, and the power conversion circuit 900 is used to convert the first power source into a second power source. In one embodiment, the power transmitting unit 10 controls the first current I1 of the first power source to be constant, wherein in the capacitor conversion mode, the second current I2 of the second power source generated by the power conversion circuit 900 is also constant and is M times the first current I1.

[0120] In one embodiment, in capacitor switching mode, at least a portion of the PWM switch QP (see, for example, the corresponding embodiment described above) is never turned on, so that one end of the inductor L is floating.

[0121] In one embodiment, in N-order PWM mode, multiple auxiliary switches QA (e.g., corresponding to...) Figure 3 , Figure 7 and Figure 8 The upper bridge auxiliary switch QUA and the lower bridge auxiliary switch QLA are never turned on, so that the capacitor CF is never electrically connected to the second power supply.

[0122] In one embodiment, in the N-order PWM mode, the ratio of the first voltage V1 of the first power supply to the second voltage V2 of the second power supply is related to the duty cycle corresponding to the N-order voltage. In one embodiment, the N-order voltage includes, for example, the first voltage V1 and the ground potential, and N-2 voltages between the first voltage V1 and the ground potential.

[0123] In one embodiment, M is an integer, and M equals N-1.

[0124] Figure 10 A schematic diagram showing another specific embodiment of the power conversion circuit of the present invention is shown. Figure 11 This diagram shows an operational waveform of an embodiment of the charging system 1010 according to the present invention. Figure 10 The power conversion circuit 1000 in the middle and Figure 3The power conversion circuit 300 is similar to the power conversion circuit 1000, except that in an embodiment, the upper bridge switches QU[1] (upper bridge sub-shared switches) in the power conversion circuit 1000 include a plurality of upper bridge sub-shared switches QU[1,1], QU[1,2]...QU[1,k] connected in parallel to each other, and in an embodiment, the lower bridge switches QL[1] (lower bridge sub-shared switches) in the power conversion circuit 1000 include a plurality of lower bridge sub-shared switches QL[1,1], QL[1,2]...QL[1,k] connected in parallel to each other, where k is an integer greater than 1.

[0125] With the above configuration, in an embodiment, in the capacitor conversion mode, during a soft start period, the plurality of upper bridge sub-shared switches QU[1,1], QU[1,2]...QU[1,k] are gradually switched on according to a predetermined timing, and / or the plurality of lower bridge sub-shared switches QL[1,1], QL[1,2]...QL[1,k] are gradually switched on according to a predetermined timing, thereby reducing the inrush current during the soft start period. The predetermined timing can be, for example, as shown in the soft start timing operation waveform diagram of Figure 11 Fig. 6, which corresponds to converting the second power supply to the first power supply, as shown in Fig. 5, when the voltage across the capacitor CF VF is significantly different from the steady-state voltage, for example, during the soft start period, 3-stage PWM power conversion or capacitor power conversion is performed with a smaller number of upper bridge sub-shared switches turned on and / or a smaller number of lower bridge sub-shared switches switched on, which can effectively reduce the inrush current. Figure 11

[0126] Specifically, taking Figure 11 Fig. 6 as an example, in this embodiment, the power conversion circuit 1000 is used to convert the second power supply to generate the first power supply, that is, the power conversion circuit 1000 performs step-up operation in the 3-stage PWM power conversion mode or performs charge pump operation in the capacitor conversion mode, and in an embodiment, the plurality of upper bridge sub-shared switches QU[1,1], QU[1,2]...QU[1,k] and / or the plurality of lower bridge sub-shared switches QL[1,1], QL[1,2]...QL[1,k] gradually increase the number of switched on according to the time periods T1, T2~Tk in Fig. 6, thereby effectively reducing the inrush current of the input current (corresponding to the second current I2). Specifically, in, for example, time period T1 and at the beginning of time period T2, only the upper bridge sub-shared switch QU[1,1] and / or the plurality of lower bridge sub-shared switches QL[1,1] participate in the switching (i.e., the switched on) of the 3-stage PWM, and the remaining upper bridge sub-shared switches and lower bridge sub-shared switches QU[1,2]...QU[1,k], QL[1,2]...QL[1,k] are always off until the corresponding time period begins, and then participate in the switching of the 3-stage PWM. Figure 11

[0127] ​​In addition, similar soft-start operation can also be applied when the power conversion circuit 1000 is operating in the 3-step PWM mode for step-down operation, or in the capacitor conversion mode for capacitive voltage division (corresponding to current boost) operation. Specifically, in the case where the above-mentioned upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] have the same on-resistance, the inrush current is dVQU[1] / (R_Q[1]*k / j), where dVQU[1] is the voltage across the upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] (e.g. drain-source voltage), R_Q[1] is the equivalent resistance of the upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] (corresponding to QU[1]) when all of them are on, and j is the number of the upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] that are on at the same time.

[0128] Figure 12 The efficiency curve of the embodiment corresponding to Figure 10 As the total conversion energy loss includes both the on-resistance energy loss and the switching energy loss, as shown in Figure 12 , the embodiment can have higher efficiency at low current when operating in the 3-step PWM mode with fewer upper bridge sub-sharing switches on (e.g. only half of the upper bridge sub-sharing switches are on) and / or fewer lower bridge sub-sharing switches on (e.g. only half of the lower bridge sub-sharing switches are on) than the general 3-step PWM mode (dashed line).

[0129] It is noted that the above-mentioned splitting of QU[1] or QL[1] into k sub-sharing switches is only an example, and in other embodiments, any of QU[2] to QU[N-1] or QL[2] to QL[N-1] can be split into k sub-sharing switches according to actual needs.

[0130] In one aspect, the on of the above-mentioned upper bridge switch QU[1] means that at least one of the upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] is on, and the off of the above-mentioned upper bridge switch QU[1] means that all of the upper bridge sub-sharing switches QU[1,1], QU[1,2],... QU[1,k] are off. The same applies to the lower bridge switches. Specifically, Figure 11For example, in the period T1 or the period T2, the upper bridge switches QU[1]~QU[N-1] still switch the capacitor CF and / or the inductor L periodically as in the previous embodiments. However, in the period T1, when the upper bridge switch QU[1] needs to be turned on, only the upper bridge sub-shared switch QU[1, 1] is turned on (corresponding to the switching on in the previous embodiment), and in the period T2, when the upper bridge switch QU[1] needs to be turned on, the upper bridge sub-shared switches QU[1, 1] and QU[1, 2] are turned on, and so on.

[0131] The present application provides a power conversion circuit and a charging system configured by an N-order PWM power converter with shared switches and a capacitor switching power converter. According to the requirements of the power conversion direction, the battery voltage and state, and the like, the combination of the operating modes of the N-order PWM power converter and the capacitor switching power converter can be adaptively selected to perform power conversion in the maximum power or high efficiency mode to charge the battery or convert the power of the battery to supply power externally.

[0132] The above has described the present application with reference to the preferred embodiments, but the above description is only to make the person skilled in the art easily understand the content of the present application, and is not intended to limit the broadest scope of the present application. The described embodiments are not limited to separate applications, but can be combined, for example, two or more embodiments can be combined, and part of the components in an embodiment can also be used to replace the corresponding components in another embodiment. In addition, various equivalent changes and various combinations can be thought of by the person skilled in the art under the same spirit of the present application, for example, the present application refers to "processing or operating or generating an output result according to a signal", which is not limited to the signal itself, but also includes, if necessary, voltage-current conversion, current-voltage conversion, and / or proportional conversion, and then processing or operating to generate an output result according to the converted signal. Therefore, various equivalent changes and various combinations can be thought of by the person skilled in the art under the same spirit of the present application, and the combination methods are various, which are not listed one by one here. Therefore, the scope of the present application should cover all the above and other equivalent changes.

Claims

1. A power conversion circuit for converting a first power source to a second power source or vice versa, the power conversion circuit comprising: A Nth order PWM power converter for switching an inductor and at least one capacitor in a Nth order PWM mode to perform conversion between a first power source and a second power source; a capacitor-switched power converter for switching a capacitor to convert between the first power source and the second power source in a capacitor conversion mode; and a Nth order PWM power converter for converting between the first power source and the second power source in a Nth order PWM mode, wherein N is an integer greater than or equal to 3, by periodically switching the inductor and the capacitor with a Nth order PWM manner. wherein the capacitor-switched power converter comprises: the plurality of shared switches; and a plurality of auxiliary switches, wherein the plurality of shared switches and the plurality of auxiliary switches periodically switch the capacitor to convert between the first power source and the second power source in a capacitor conversion manner in the capacitor conversion mode. wherein at least part of the plurality of PWM switches are constantly non-conducting in the capacitor conversion mode, such that one end of the inductor is floating. in the Nth order PWM mode, the plurality of auxiliary switches are constantly non-conducting, such that the capacitor is constantly non-conducting to one of the first power source or the second power source. the Nth order PWM power converter comprises: a plurality of upper bridge switches coupled in series between the first power source and a switching node, wherein the plurality of upper bridge switches are sequentially and adjacently coupled to corresponding at least one upper bridge intermediate node; and 2. The power conversion circuit of claim 1, wherein, a plurality of lower bridge switches coupled in series between the switching node and a ground potential, wherein the plurality of lower bridge switches are sequentially and adjacently coupled to corresponding at least one lower bridge intermediate node; 3. The power conversion circuit of claim 2, wherein, wherein the capacitor-switched power converter comprises: part of the plurality of upper bridge switches; part of the plurality of lower bridge switches, wherein the part of the plurality of upper bridge switches and the part of the plurality of lower bridge switches correspond to the plurality of shared switches; an upper bridge sub-auxiliary switch having a first end coupled to the second power source and a second end coupled to a corresponding one of the upper bridge intermediate nodes; and a lower bridge sub-auxiliary switch having a first end coupled to the second power source and a second end coupled to a corresponding one of the lower bridge intermediate nodes, wherein the upper bridge sub-auxiliary switch and the lower bridge sub-auxiliary switch correspond to the auxiliary switches; wherein the inductor is coupled between the switching node and the second power source; wherein a first end of the capacitor is coupled to a corresponding one of the upper bridge intermediate nodes and a second end of the capacitor is coupled to a corresponding one of the lower bridge intermediate nodes; wherein in the Nth order PWM mode, the plurality of upper bridge switches and the plurality of lower bridge switches periodically switch the capacitor to generate a Nth order voltage at the switching node, thereby causing the inductor to convert between the first power source and the second power source in a Nth order PWM manner; and wherein in the capacitor conversion mode, at least part of the plurality of upper bridge switches and the plurality of lower bridge switches are constantly non-conducting, such that the capacitor is constantly non-conducting to one of the first power source or the second power source. ​ ​ wherein in the capacitor conversion mode, the upper bridge sub auxiliary switch, the lower bridge sub auxiliary switch and the plurality of shared switches periodically switch the capacitor, thereby causing the capacitor to convert the first power source to the second power source in a capacitor voltage division manner, or to convert the second power source to the first power source in a charge pump manner.

4. The power conversion circuit of claim 3, wherein, In the N-order PWM mode, the upper bridge sub auxiliary switch and the lower bridge sub auxiliary switch are constantly non-conductive, causing the capacitor to be constantly electrically disconnected from the second power source.

5. The power conversion circuit of claim 3, wherein, In the capacitor conversion mode, at least one of the plurality of upper bridge switches other than the plurality of shared switches is constantly non-conductive, and at least one of the plurality of lower bridge switches other than the plurality of shared switches is constantly non-conductive, causing one end of the inductor coupled to the switching node to be floating.

6. The power conversion circuit of claim 3, wherein, In the N-order PWM mode, the ratio of a first voltage of the first power source to a second voltage of the second power source is related to the duty cycle corresponding to the N-order voltage.

7. The power conversion circuit of claim 3, wherein, In the capacitor conversion mode, the ratio of a first voltage of the first power source to a second voltage of the second power source is M, where M is a real number greater than 1.

8. The power conversion circuit of claim 7, wherein, M is equal to N-1.

9. The power conversion circuit of claim 7, used to convert the first power source to the second power source, wherein in the capacitor conversion mode, a first current of the first power source is constant, causing a second current of the second power source to be constant and M times the first current.

10. The power conversion circuit of claim 7, wherein, In the capacitor conversion mode, An upper bridge switch of the plurality of shared switches includes a plurality of upper bridge sub shared switches connected in parallel to each other, wherein during a soft start period, the plurality of upper bridge sub shared switches are gradually switched on according to a preset timing; and / or A lower bridge switch of the plurality of shared switches includes a plurality of lower bridge sub shared switches connected in parallel to each other, wherein during the soft start period, the plurality of lower bridge sub shared switches are gradually switched on according to a preset timing; thereby reducing an inrush current during the soft start period.

11. The power conversion circuit of claim 7, wherein the plurality of upper bridge switches includes a first upper bridge switch and a second upper bridge switch connected in series between the first power source and the switching node in sequence, wherein the first upper bridge switch and the second upper bridge switch are coupled to each other at an upper bridge intermediate node; the plurality of lower bridge switches includes a first lower bridge switch and a second lower bridge switch connected in series between the ground potential and the switching node in sequence, wherein the first lower bridge switch and the second lower bridge switch are coupled to each other at a lower bridge intermediate node; the first upper bridge switch and the first lower bridge switch correspond to the plurality of shared switches; wherein the upper bridge sub auxiliary switch is coupled between the second power source and the upper bridge intermediate node, and the lower bridge sub auxiliary switch is coupled between the second power source and the lower bridge intermediate node; wherein the capacitor is coupled between the upper bridge intermediate node and the lower bridge intermediate node.

12. The power conversion circuit of claim 11, wherein, The power conversion circuit repeats switching in a switching period, where N equals 3, in a corresponding 3rd order PWM mode, in a first time period of the switching period, the first upper bridge switch and the second lower bridge switch are turned on, the second upper bridge switch and the first lower bridge switch are not turned on, and in a second time period of the switching period, the first lower bridge switch and the second lower bridge switch are turned on, the first upper bridge switch and the second upper bridge switch are not turned on, and in a third time period of the switching period, the second upper bridge switch and the first lower bridge switch are turned on, the first upper bridge switch and the second lower bridge switch are not turned on, in a fourth time period of the switching period, the first upper bridge switch and the second upper bridge switch are turned on, and the first lower bridge switch and the second lower bridge switch are not turned on, whereby the voltage of the switching node is periodically switched between the first voltage, the ground potential and 1 / 2 of the first voltage. Wherein the upper bridge sub auxiliary switch and the lower bridge sub auxiliary switch are constantly not turned on, so that the capacitor is constantly not electrically connected to the second power source.

13. The power conversion circuit of claim 11, wherein, The power conversion circuit repeats switching in a switching period, where M equals 2, in the capacitor conversion mode, in a first time period of the switching period, the first upper bridge switch and the lower bridge sub auxiliary switch are turned on, the upper bridge sub auxiliary switch and the first lower bridge switch are not turned on, and in a second time period of the switching period, the upper bridge sub auxiliary switch and the first lower bridge switch are turned on, the first upper bridge switch and the lower bridge sub auxiliary switch are not turned on, whereby the first end of the capacitor is periodically switched between the first voltage and the second voltage, and the second end of the capacitor is periodically switched between the second voltage and the ground potential. Wherein the second upper bridge switch and the second lower bridge switch are constantly not turned on, so that one end of the inductor is floating.

14. A charging system, comprising: a power transmitting unit, for generating a DC power according to an input power; and a charging circuit, removably connected with the power transmitting unit, for converting the DC power to generate a charging power to charge a battery; wherein the charging circuit corresponds to the power conversion circuit of any one of claims 1-13; wherein the first power corresponds to the DC power, the second power corresponds to the charging power, or wherein the second power corresponds to the DC power, the first power corresponds to the charging power.

15. A power supply system, comprising: a battery, for providing an electrical energy; and a power supply circuit, coupled with the battery, for converting the electrical energy to generate a power supply power to supply a load; wherein the power supply circuit corresponds to the power conversion circuit of any one of claims 1-13; wherein the first power corresponds to the electrical energy, the second power corresponds to the power supply power, or wherein the second power corresponds to the electrical energy, the first power corresponds to the power supply power.

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