Power conversion modules and power converters

Abstract

The present invention discloses a power conversion module and a power converter, wherein the power conversion module comprises an N-level structure, wherein the first N-1-level structure is composed of a basic unit, and the i-th level structure comprises 2 i‑1 The invention provides a balancing unit, and controls the state of the switch tubes in each basic unit and the balancing unit, so that when the power conversion module works in a steady state, the voltage across the capacitor is basically stable, and the output current of each balancing unit is equal. The invention retains the advantages of the three-level Buck DC-DC power converter (such as the reduced withstand voltage of the power tube, the use of a smaller inductor, etc.), solves the problem that the three-level Buck cannot automatically achieve voltage balance across the flying capacitor; no additional control strategy is required to ensure the equalization of the output current of the final structure; and a higher voltage ratio can be provided without changing the duty cycle of the final Buck circuit.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and more specifically, to a power conversion module and a power converter. Background Art

[0002] Figure 1 It is a three-level Buck DC-DC power converter in the prior art. Compared with the traditional Buck circuit, the withstand voltage of each power tube is half of the DC bus voltage (V in / 2), so power tubes with lower withstand voltage levels can be used; the switching of each power tube makes the voltage ripple on the inductor smaller, and a smaller inductor can be used, thereby improving power density. However, the three-level Buck DC-DC power converter cannot automatically realize the jumper capacitor (C F ) voltage balance, that is, it cannot automatically achieve V CF =V in / 2, so it is necessary to sample the voltage across the capacitor (V CF ), the voltage balance across the capacitor is achieved through additional control strategies, which makes the circuit control complicated.

[0003] Therefore, how to provide a converter that has the advantages of a three-level Buck DC-DC power converter and can automatically achieve voltage balance across capacitors has become one of the problems that people in this field need to solve urgently. Summary of the invention

[0004] In view of this, the present invention proposes a three-level Buck DC-DC power converter which has the advantages of the three-level Buck DC-DC power converter and can solve the problem that the three-level Buck DC-DC power converter cannot automatically achieve voltage balance across capacitors.

[0005] In a first aspect, an embodiment of the present invention provides a power conversion module, wherein the power conversion module includes an N-level structure, wherein the i-th level structure is composed of 2i-1 basic units, and the second end of each basic unit in each level structure is respectively connected to the first ends of two basic units in the next level structure; the first end of the first basic unit in the first level structure serves as the first end of the power conversion module, wherein N is a natural number greater than or equal to 2, i is a positive integer, and 1≤i≤N-1;

[0006] The N-th level structure includes 2N-1 balancing units, the second ends of the balancing units are connected as the second end of the power conversion module, and the second ends of the basic units in the N-1-th level structure are respectively connected to the first ends of the two balancing units;

[0007] The basic unit is a switched capacitor circuit; by controlling the states of the switch tubes in each of the basic units and the balancing unit, when the power conversion module operates in a steady state, the voltage across the capacitor in the basic unit is substantially constant, and the current flowing through the second end of each of the balancing units is equal.

[0008] Preferably, the balancing unit includes: an inductor and two first switching tubes and a second switching tube connected in series between a first end of the balancing unit and a reference ground, wherein a common connection end of the first switching tube and the second switching tube is connected to one end of the inductor, and the other end of the inductor is connected to the second end of the balancing unit.

[0009] Preferably, the second switch tube is replaced by a diode.

[0010] Preferably, the first switch tubes in the two balancing units connected to the second end of the same basic unit in the N-1th level structure operate in phase shift, with a phase difference of 180°.

[0011] Preferably, the duty cycles of the first switching tubes in each balancing unit are the same.

[0012] Preferably, the basic unit includes a jumper capacitor and four switch tubes connected in series in sequence between the first end of the basic unit and the reference ground: a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the jumper capacitor is connected between the first connection end and the second connection end; the first connection end is the common connection end of the first switch tube and the second switch tube, and the second connection end is the common connection end of the third switch tube and the fourth switch tube; the common connection end of the second switch tube and the third switch tube is the second end of the basic unit.

[0013] Preferably, the switching states of the first switch tube and the third switch tube in each basic unit are the same, and the switching states of the second switch tube and the fourth switch tube are the same and complementary to the switching state of the first switch tube.

[0014] Preferably, the first switch tubes in the two basic units in the subsequent structure connected to the second end of the same basic unit operate in staggered phases, with a phase difference of 180°.

[0015] Preferably, the duty cycle of each switch tube in each basic unit is 0.5.

[0016] Preferably, when the power conversion module operates in a steady state, the voltage of the jumper capacitor in the j-th structure is stabilized at Vin / 2j, wherein Vin is the voltage of the first end of the power conversion module, j is a natural number, and 1≤j≤N-1.

[0017] Preferably, the switching frequencies of the switches in the basic units in two adjacent stages satisfy: the switching frequency of the previous stage basic unit is k times or 1 / k of the switching frequency of the next stage basic unit, where k is an odd number.

[0018] Preferably, the switching frequency of the switch tube in the balancing unit is an odd multiple of the highest switching frequency in the first to N-1th level structures.

[0019] Preferably, the first switch tube in the basic unit in the previous stage structure and the first switch tube in one of the basic units or the balancing unit in the next stage structure connected to the basic unit in which the two first switch tubes start to conduct at the same time.

[0020] Preferably, the first end of the power conversion module is an input end connected to an external power source, and the second end of the power conversion module is an output end.

[0021] Preferably, the second end of the power conversion module is an input end connected to an external power source, and the first end of the power conversion module is an output end.

[0022] In the second aspect, an embodiment of the present invention also provides a power converter, which includes a control module and a power conversion module as described in any one of claims 1-15, wherein the control module is used to generate a driving signal for each switching tube in the power conversion module to control the state of each switching tube in the power conversion module.

[0023] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0024] 1. Retain the advantages of the three-level Buck DC-DC power converter, such as reducing the voltage requirements of the power tube, using a smaller power inductor, and improving the power density;

[0025] 2. No additional control strategy is required to ensure the equalization of the current of each inductor, which solves the problem that the three-level Buck can not automatically achieve the voltage balance of the flying capacitor;

[0026] 3. A higher voltage ratio can be provided without changing the duty cycle of the balancing unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0028] Figure 1 It is a structural diagram of a three-level Buck circuit in the prior art;

[0029] Figure 2is a schematic structural diagram of a first power conversion module according to an embodiment of the present invention;

[0030] Figure 3 A first working waveform diagram of a first power conversion module according to an embodiment of the present invention;

[0031] Figure 4 A second working waveform diagram of the first power conversion module according to an embodiment of the present invention;

[0032] Figure 5 is a third working waveform diagram of the first power conversion module according to an embodiment of the present invention;

[0033] Figure 6 is a schematic structural diagram of a second power conversion module according to an embodiment of the present invention;

[0034] FIG7 is a first working waveform diagram of the second power conversion module according to an embodiment of the present invention;

[0035] FIG8 is a second working waveform diagram of the second power conversion module according to an embodiment of the present invention;

[0036] Fig. 9 is a schematic structural diagram of a third power conversion module according to an embodiment of the present invention;

[0037] Fig.10 Schematic diagram of the structure of a fourth power conversion module according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, flows, components and circuits are not described in detail.

[0039] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0040] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0041] like Figure 2 As shown, this embodiment first discloses a power conversion module including a two-stage structure, that is, N=2, wherein the first stage structure includes a basic unit 11, and the second stage structure includes two balancing units 1a and 1b, and the second ends of the balancing units are connected as the output end of the power conversion module, and the second end of the first basic unit 11 in the first stage structure is connected to the first ends of the first balancing unit 1a and the second balancing unit 1b in the second stage structure. The first end of the basic unit 11 in the first stage structure is connected to an external power supply as the input end of the power conversion module. In this embodiment, the cth switch tube in the bth basic unit (or the bth balancing unit) in the ath stage structure uses Q abc The corresponding driving signal is represented by G abc Indicates that each switch is turned on at a high level and turned off at a low level. For example, the first switch in the first basic unit (or the first balancing unit) in the second-level structure is Q 211 The corresponding driving signal is represented by G 211 It means that when G 211 When the G 211 When it is low, Q211 is disconnected.

[0042] As an example, Figure 2 As shown, the balancing unit is a Buck circuit, including: an inductor and two switch tubes connected in series between the input end of the balancing unit and the reference ground: a first switch tube and a second switch tube, wherein the common connection end of the first switch tube and the second switch tube is connected to one end of the inductor, and the other end of the inductor serves as the output end of the balancing unit. By switching the state of the switch tube in the balancing unit, the inductor switches between storing magnetic energy and releasing magnetic energy, maintaining the output voltage Vout and the output current of each balancing unit.

[0043] Furthermore, the switching frequencies of the balancing units 1a and 1b are the same, and the first switch tube and the second switch tube in the same balancing unit work complementary to each other, that is, synchronous rectification mode; the second switch tube in each balancing unit can also be replaced by a diode for freewheeling. In addition, the duty cycle of the first switch tube in each balancing unit is the same, and the first switch tubes in the two balancing units connected to the same basic unit work in staggered phases, with a phase difference of 180°. That is, the switch tubes Q221 and Q222 are complementary to each other, the switch tubes Q211 and Q212 are complementary to each other, and the duty cycle of the switch tubes Q221 and Q211 is the same, and the conduction phase difference is 180°.

[0044] As an example, Figure 2As shown, the basic unit 11 includes a cross-over capacitor C1 and four switch tubes connected in series between the first end of the basic unit 11 and the reference ground: the first switch tube Q111, the second switch tube Q112, the third switch tube Q113 and the fourth switch tube Q114; the cross-over capacitor C1 is connected between the first connection end and the second connection end; the first connection end is the connection end of the first switch tube Q111 and the second switch tube Q112, the second connection end is the connection end of the third switch tube Q113 and the fourth switch tube Q114; the connection end of the second switch tube Q112 and the third switch tube Q113 is the output end of the basic unit 11. The switching states of the first switch tube and the third switch tube in each basic unit are the same, and the switching states of the second switch tube and the fourth switch tube are the same and complementary to the switching state of the first switch tube, that is, the states of the first switch tube Q111 and the third switch tube Q113 in the basic unit 11 are the same, and the states of the second switch tube Q112 and the fourth switch tube Q114 are the same and complementary to the state of the first switch tube Q111. The duty cycle of the driving signal of each switch tube in the basic unit 11 is 0.5; by switching the state of the switch tube in the basic unit 11, the jumper capacitor C1 is switched between a charging state and a discharging state, wherein the charging state includes the jumper capacitor C1 being connected in series between the input end and the output end of the basic unit 11 where the jumper capacitor C1 is located, and the discharging state includes the jumper capacitor C1 being connected in series between the output end of the basic unit 11 where the jumper capacitor C1 is located and the reference ground.

[0045] It should be noted that the composition of the basic unit 11 and the composition of the balancing units 1a and 1b, and the relationship between the driving signals of the switching tubes in each stage of the structure are not limited to those listed in this embodiment and are not listed one by one here. Any composition and driving signal that can achieve the voltage balance of the cross-capacitor in the basic unit and the current balance conditions at the output end of each balancing unit satisfies the present invention.

[0046] Figure 3 The first working waveform of the first power converter is given, such as Figure 3 As shown, the driving signals G211 and G221 of the first switch tubes Q211 and Q221 in the basic unit 11 and each balancing unit, and the voltage V swa 、V swb and the current i flowing into the first terminals of the two balancing units a and i b The waveform diagram shows that the switching period (corresponding to the period of the driving signal) of the four switching tubes G111, G112, G113, and G114 in the basic unit is T1, and the switching frequency (corresponding to the frequency of the driving signal) is f1=1 / T1; the switching period of the switching tubes in each balancing unit is the same as Tbuck , frequency is f buck =1 / T buck , the duty cycle of the first switch in each balancing unit is d (in this embodiment, d≤0.5); and the switching frequency of the balancing unit is an odd multiple of the basic unit, that is, f buck =(2p+1)·f1, where p=0,1,2,3….

[0047] like Figure 2 As shown, the voltage at the common input of the two balancing units 1a and 1b is V bus , the output voltage of the power conversion module is V out , the voltage V at the common connection terminal of the first switch tube and the second switch tube in the two balancing units swa and V swb All in V bus and 0V (when the first switch tube Q211 in the first balancing unit is turned on, V swa =V bus ; When the first switch tube Q211 in the first balancing unit is disconnected, V swa =0; Similarly, when the first switch tube Q221 in the second balancing unit is turned on, V swb =V bus ; When the first switch tube Q221 in the second balancing unit is disconnected, V swb =0). When the first switch tube Q111 and the third switch tube Q113 in the basic unit 11 are turned on, the corresponding Figure 3 In the interval [0,T1 / 2], V bus =V in -V C1 ; When Q111 and Q113 are turned off, that is, in the interval [T1 / 2, T1], V bus =V C1 , where V in is the voltage of the external power supply.

[0048] like Figure 3 As shown, the duty cycle of the driving signal of the switch tube in the basic unit is 0.5, and the duty cycles d of the driving signals of the first switch tubes in each balancing unit 1a and 1b are equal; the rising edge of the driving signal G211 of the first switch tube Q211 in the first balancing unit 1a is aligned with the rising edges of the driving signals G111 and G113 of the first switch tube Q111 and the third switch tube Q113 in the basic unit 11, and the driving signal G221 of the first switch tube Q221 in the second balancing unit 1b lags 180° behind the driving signal G211 of the first switch tube Q211 in the first balancing unit 1a, that is, the lag T buck / 2. Thus, in the first half switching cycle [0, T1 / 2] when the driving signal G111 of the first switch tube Q111 and the driving signal G113 of the third switch tube Q113 in the basic unit 11 are turned on, when the duty cycle d of the driving signal of the first switch tube in the balancing unit is ≤0.5, the driving signal G211 of the first switch tube Q211 in the first balancing unit 1a has p+1 high levels and p low levels, and the driving signal G221 of the first switch tube Q221 in the second balancing unit 1b has p high levels and p+1 low levels; in the half switching cycle [T1 / 2, T1] when the first switch tube Q111 and the third switch tube Q113 in the first-stage structure are turned off, the driving signal G211 of the first switch tube Q211 in the first balancing unit 1a has p high levels and p+1 low levels, and the driving signal G221 of the first switch tube Q221 in the second balancing unit 1b has p+1 high levels and p low levels.

[0049] When the circuit works in steady state, according to the volt-second balance of the inductor, in one switching cycle of the basic unit, that is, in the interval [0, T1], the voltage V swa and V swb Satisfies the following equation, where V out is the average value of the output voltage:

[0050]

[0051]

[0052]

[0053]

[0054] In addition, when the power conversion module operates in a steady state, in the interval [0, T1 / 2], the cross-over capacitor C1 is always charged, and in the interval [T1 / 2, T1], the cross-over capacitor C1 is always discharged. The charge and discharge are balanced in the steady state, that is, the ampere-second balance equation for the cross-over capacitor C1 is written as follows:

[0055]

[0056] When the duty cycle d of the driving signal of the first switch tube in the balancing unit is ≤0.5, according to Figure 3 i a and i b , we can get formula (6),

[0057] I La ·d·T buck (p+1)+I Lb ·d·Tbuck p=I La ·d·T buck p+I Lb ·d·T buck ·(p+1)(6)

[0058] Among them I La and I Lb are respectively the first inductors L flowing through the two balancing units a and the second inductor L b The average value of the current.

[0059] Figure 4 The second working waveform of the first power converter is given. Figure 3 The difference is that, in this embodiment, the duty cycle of the first switch tube in each balancing unit is d>0.5. When the duty cycle of the driving signal of the first switch tube in the two balancing units is d>0.5, according to Figure 4 V swa ' and V swb ', expressions (1) and (2) can be transformed into:

[0060]

[0061]

[0062] Combining (3) and (4), (7) and (8), we can get (9), which proves that no matter the duty cycle of the driving signal of the first switch tube of the balancing unit is d≤0.5 or d>0.5, the voltage V across the capacitor C1 is C1 They can all be automatically balanced.

[0063]

[0064] Similarly, when the duty cycle d of the driving signal of the first switch tube in the balancing unit is greater than 0.5, according to Figure 4 i a 'and i b ', formula (5) can be further transformed into formula (10),

[0065] I La ·d·T buck p+I La 0.5 T buck +I Lb ·(d-0.5)·T buck +I Lb ·d·T buck p=I La ·(d-0.5)·T buck +I La ·d·Tbuck p+I Lb ·d·T buck p+I Lb 0.5 T buck (10)

[0066] By simplifying (6) and (10), we can get (11), which proves that no matter the duty cycle of the driving signal of the first switch tube in the balancing unit is d≤0.5 or d>0.5, the output currents of the two balancing units are equal, that is, they are automatically current-balanced.

[0067] I La =I Lb (11)

[0068] It should be noted that when the frequency of the driving signal in the balancing unit is an even multiple of the driving signal in the basic unit, that is, f Buck =2p·f1, equations (3) and (4) are identical, equations (7) and (8) are identical, and equation (9) cannot be derived. Similarly, equations (6) and (10) are identical, and equation (11) cannot be derived. That is, it cannot be concluded that the voltage across the capacitor can be automatically balanced, and it cannot be concluded that the output current of each balancing unit is automatically equalized.

[0069] In addition, when the driving signal frequency of the switch in the basic unit is an odd multiple of the driving signal frequency in the balancing unit, that is, f1 = (2p+1)·f buck , where p = 0, 1, 2, 3 ..., the operating waveform of the power conversion module is as follows Figure 5 As shown. In a balancing unit cycle [0,T buck ], when G111 / G113, G211 or G221 are all high level, V bus =V in -V C1 , when G111 / G113 is low and G211 or G221 is high, V bus =V C1 When the duty cycle of the driving signal of the first switch tube in the balancing unit is d=0.5, the voltage at the common end of the two switch tubes in the two balancing units 1a and 1b is as follows: Figure 5 V swa and V swb As shown, in this interval, in [0,T buck / 2], V swa =V in -V C1 The time is (p+1)·T1 / 2, V swa =V C1 The time is p·T1 / 2; in [T buck / 2,Tbuck ], V swb =V C1 The time is (p+1)·T1 / 2, V swb =V in -V C1 The time is p·T1 / 2, according to the first inductance L a and the second inductor L b The volt-second balance of the two switching tubes in the two balancing units 1a and 1b is obtained by equations (1) and (2), which are the same as equations (3) and (4), and furthermore, equation (9) can be derived, which means that the voltage balance across the capacitor can be achieved automatically. When the duty cycle d of the driving signal of the first switching tube in the balancing unit is less than 0.5, when the voltage at the common end of the two switching tubes in the two balancing units 1a and 1b is as follows Figure 5 V swa1 and V swb1 As shown, in a cycle [0,T buck ] interval, V swa1 and V swb1 Equal to V bus , and within this interval, V swa1 =V in -V C1 The time is p·T1 / 2, V swa1 =V C1 The time is p·T1 / 2, V swb1 =V in -V C1 The time is p·T1 / 2, V swb1 =V C1 The time is p·T1 / 2, so V swa1 and V swb1 Medium V bus =V in -V C1 The time of V is equal, both are p·T1 / 2, swa1 and V swb1 Medium V bus =V C1 The time of is equal, both are p·T1 / 2, that is, there will be a situation where formula (1) and formula (2) are identical, and formula (9) cannot be derived. Similarly, when the duty cycle d of the driving signal of the first switch tube in the balancing unit is greater than 0.5, when the voltage at the common end of the two switch tubes in the two balancing units is Figure 5 V swa2 and V swb2 When V swa2 and V swb2 Medium V bus =V in -V C1 The time of V is equal, both are (p+1)·T1 / 2, V swa2 and Vswb2 V in bus = V C1 The times are equal, both being (p + 1)·T1 / 2, that is, there will be a situation where Formula (1) and Formula (2) are identically equal; that is, when the frequency of the driving signal of the switching tube in the basic unit is an odd multiple of the frequency of the driving signal in the balancing unit, when d ≠ 0.5, the voltage balance of the bridging capacitor cannot be automatically achieved.

[0070] When N = 3, the structural schematic diagram of the power conversion module is as Figure 6 shown, including three-level structures: the first-level structure includes 1 basic unit 11, the second-level structure includes 2 basic units 21 and 22, and the third-level structure includes 4 balancing units 1a, 1b, 2a, and 2b; the second end of the first basic unit 11 in the first-level structure is connected to the first ends of the first basic unit 21 and the second basic unit 22 in the second-level structure; the second end of the first basic unit 21 in the second-level structure is connected to the first ends of the first balancing unit 1a and the second balancing unit 1b in the third-level structure, and the second end of the second basic unit 22 in the second-level structure is connected to the first ends of the third balancing unit 2a and the fourth balancing unit 2b in the third-level structure; the first end of the first basic unit 11 in the first-level structure is used as the input end of the power conversion module and is connected to an external power supply, and the second ends of each balancing unit are connected to each other as the output end of the power conversion module.

[0071] The composition of each basic unit and balancing unit, and the relationship of the driving signals of each switching tube in the same basic unit or balancing unit are the same as those of the power conversion module with N = 2. The duty cycle of each switching tube in each basic unit is 0.5. The first switching tubes in the two basic units in the subsequent-level structure connected to the second end of the same basic unit operate with a phase shift of 180° (that is, the switching states are complementary, that is, the switching states of switching tubes Q211 and Q221 are complementary). The duty cycles of the first switching tubes in each balancing unit are the same, and the first switching tubes in the two balancing units connected to the second end of the same basic unit operate with a phase shift, with a phase difference of 180°.

[0072] The switching period of the switching tube in the first-level structure is T1, and the frequency is f1 = 1 / T1. The switching period of the switching tube in the second-level structure is T2, and the frequency is f2 = 1 / T2, where f2 = (2q + 1)f1, or f1 = (2q + 1)f2, where q = 0, 1, 2, 3…. The switching periods of the balancing units in the third-level structure are the same as T buck , and the switching frequency is f buck = 1 / T buck , and the duty cycles of the driving signals of the first switching tubes in each balancing unit are all d (0 < d < 1). The switching frequency f of the switching tubes in the balancing units in the third-level structure Buckis an odd multiple of the highest switching frequency among all basic units, that is, when f2=(2q+1)f1, f Buck =(2p+1)f2; when f1=(2q+1)f2, f Buck =(2p+1)f1, where p=0,1,2,3….

[0073] It should be noted that if the switching frequency of the switching tube in the second-level structure is an even multiple of that of the first-level structure, that is, f2=2q·f1, where p=0,1,2,3… (or conversely f1=2q·f2), or if the frequency of the driving signal of the switching tube in the balancing unit is an even multiple of the highest switching frequency among all basic units, then the power conversion module will not be able to automatically achieve voltage and current balancing.

[0074] FIG7 shows the first working waveform of the second power converter (N=3) according to the embodiment of the present invention, where f2=(2q+1)f1, where q=0, 1, 2, 3…. Figure 6 The working principle of the power converter is described in detail in FIG. Figure 6 As shown, the voltage at the common input terminal of the first balancing unit 1a and the second balancing unit 1b is V 1bus , the voltage at the common end of the two switch tubes Q311 and Q312 in the first balancing unit is V 1swa , the voltage at the common end of the two switch tubes Q321 and Q322 in the second balancing unit is V 1swb , the average output voltage of the power conversion module is V out As shown in FIG. 7( a ), when the driving signal G311 of the first switch tube Q311 in the first balancing unit in the third-stage structure is at a high level, Q311 is turned on, and V 1swa =V 1bus ; When G311 is low, Q311 is disconnected, V 1swa =0; when the driving signal G321 of the first switch tube Q321 in the second balancing unit in the third-stage structure is high, Q321 is turned on, V 1swb =V 1bus , when G321 is low level, Q321 is disconnected, V 1swb =0. In the interval [0, T1 / 2], when the driving signals G111 and G113 of the first switch tube Q111 and the third switch tube Q113 in the first stage structure are high, and the driving signals G211 and G213 of the first switch tube Q211 and the third switch tube Q213 in the first basic unit in the second stage structure are also high, Q111 and Q113 are turned on, that is, Q211 and Q213 are both turned on. At this time, V 1bus =V in -V C1 -VC21 When the driving signals G111 and G113 of the first switch tube Q111 and the third switch tube Q113 in the first stage structure are low, and the driving signals G211 and G213 of the first switch tube Q211 and the third switch tube Q213 in the first basic unit in the second stage structure are high, Q111 and Q213 are disconnected, Q211 and Q213 are turned on, and V 1bus =V C1 -V C21 When the driving signals G211 and G213 of the first switch tube Q211 and the third switch tube Q213 in the first basic unit of the second-stage structure are low, Q211 and Q213 are disconnected, and V 1bus =V C21 The voltage of the external power supply connected to the first end of the first basic unit 11 in the first level structure is V in .

[0075] Similarly, if Figure 6 As shown, the potential of the common input terminal of the third balancing unit 2a and the fourth balancing unit 2b is V 2bus , the voltage at the common end of the two switch tubes Q331 and Q332 in the third balancing unit is V 2swa , the voltage at the common end of the two switch tubes Q341 and Q342 in the fourth balancing unit is V 2swb As shown in FIG. 7( b ), when the driving signal G331 of the first switch tube Q331 in the third balancing unit in the third stage structure is at a high level, Q331 is turned on, and V 2swa =V 2bus , when G331 is low, Q331 is disconnected, V 2swa =0; when the driving signal G341 of the first switch tube Q341 in the fourth balancing unit in the third-stage structure is high, Q341 is turned on, V 2swb =V 2bus , when G341 is low level, Q341 is disconnected, V 2swb =0; when the driving signals G111 and G113 of the first switch tube Q111 and the third switch tube Q113 in the first stage structure are high, and the driving signals G221 and G223 of the first switch tube Q221 and the third switch tube Q223 in the second basic unit in the second stage structure are high, Q111, Q113, Q221 and Q223 are turned on, and V 2bus =V in -V C1 -V C22When the driving signals G111 and G113 of the first switch tube Q111 and the third switch tube Q113 in the first stage structure are at a low level, and the driving signals G221 and G223 of the first switch tube Q221 and the third switch tube Q223 in the second basic unit in the second stage structure are at a high level, Q111 and Q113 are disconnected, Q221 and Q223 are turned on, and V 2bus =V C1 -V C22 When the driving signals G221 and G223 of the first switch tube Q221 and the third switch tube Q223 in the second basic unit of the second stage structure are low, Q221 and Q223 are disconnected, and V 2bus =V C22 .

[0076] In FIG. 7( a), the rising edges of the driving signal G311 of the first switch tube Q311 of the first balancing unit in the third-stage structure, the driving signal G211 of the first switch tube Q211 in the first basic unit 21 in the second-stage structure, and the driving signal G213 of the third switch tube Q213 are preferably aligned with the rising edges of the driving signal G111 of the first switch tube Q111 and the driving signal G113 of the third switch tube Q113 in the basic unit 11 in the first-stage structure. The driving signals G223 of the first switch tube Q221 and the third switch tube Q223 in the second basic unit 22 in the second-stage structure are 180° out of phase with G111 and G113, i.e., a phase difference of T2 / 2. The first switch tube Q321 of the second balancing unit in the third-stage structure is 180° out of phase with the first switch tube G311 of the first balancing unit.

[0077] When the circuit is working in steady state, the inductors L in the four balancing units are 1a , L 1b , L 2a , L 2b The equation for volt-second balance is written as follows,

[0078]

[0079]

[0080]

[0081]

[0082] Here, the case where the duty cycle d≤0.5 of the driving signal of the first switch tube in each balancing unit is described, when f2=(2q+1)f1, where q=0,1,2,3… As shown in FIG7(a), equations (12) and (13) can be transformed into:

[0083]

[0084]

[0085] Similarly, equations (14) and (15) can be transformed into:

[0086]

[0087]

[0088] Based on the four equations (16), (17), (18), and (19), the voltage balance of the flying capacitor can be proved. Combining (16) with (17), we can get (20). Combining (18) with (19), we can get (21). Combining (17) with (18), we can get (22).

[0089] V in (q+1) = V C1 +V C21 ·(4q+2) (20)

[0090] V in q+V C1 =V C22 ·(4q+2) (21)

[0091] V in (pq) = V C1 ·(2p+1)-(V C21 +V C22 )·(2q+1) (22)

[0092] Combining (20) with (21), we can eliminate V C1 , we get (23). Substituting (23) into (22) we get (24).

[0093] V in =2(V C21 +V C22 ) (twenty three)

[0094] V C1 =V in / 2 (24)

[0095] Substituting (24) into (20) and (21), we can obtain (25) and (26).

[0096] V C21 =V C1 / 2 (25)

[0097] V C22 =V C1 / 2 (26)

[0098] The above proves that when f2=(2q+1)f1, where q=0,1,2,3…, the flying capacitors C1 and C 21 and C 22 Voltage balance can be achieved.

[0099] The following proves that when f2 = (2q + 1)f1, the output current balance problem of each balancing unit is based on the ampere-second balance principle of the flying capacitor. FIG7 (a) is a current diagram of the first balancing unit 1a and the second balancing unit 1b. The input current of the first balancing unit 1a is i 1a , the input current of the second balancing unit 1b is i 1b The average values ​​of the inductor currents output by the first balancing unit 1a and the second balancing unit 1b are I L1a and I L1b Similarly, FIG7(b) is a schematic diagram of the current of the third balancing unit 2a and the fourth balancing unit 2b. The input currents of the third balancing unit 2a and the fourth balancing unit 2b are respectively i 2a and i 2b The average values ​​of the inductor currents output by the third balancing unit 2a and the fourth balancing unit 2b are I L2a and I L2b .

[0100] First, it is proved that when f2 = (2q + 1)f1, where q = 0, 1, 2, 3, ..., the output current of the first balancing unit 1a and the second balancing unit 1b are equal. As shown in FIG7(a), in a switching cycle [0, T2] of the balancing unit, the capacitor C connected across the first half of the switching cycle [0, T2 / 2] 21 Charging, the capacitor C is connected across the second half of the switching cycle [T2 / 2, T2] 21 Discharge, charge and discharge balance in steady state, for the cross-capacitor C 21 The balance equation for the Colean seconds is as follows:

[0101]

[0102] Regardless of whether the duty cycle of the driving signal of the first switch tube in the balancing unit is d>0.5 or d≤0.5, according to the i shown in FIG. 7 1a and i 1b , formula (27) can be converted to:

[0103] I L1a ·d·T Buck (p+1)+I L1b ·d·T Buck p=I L1a ·d·T Buck p+I L1b ·d·TBuck ·(p+1) (28)

[0104] Simplifying (28), we can get (29):

[0105] I L1a =I L1b (29)

[0106] Secondly, it is proved that the output current of the third balancing unit 2a and the fourth balancing unit 2b is equal. As shown in Figure 7(b), in a switching cycle [T2 / 2, T2*3 / 2] of the driving signal of the switch tube of the second-stage structure, C 22 Charging, in the second half of the switching cycle [T2, T2*3 / 2], C 22 Discharge, charge and discharge balance in steady state, for C 22 The balance equation for the Colean seconds is as follows:

[0107]

[0108] Regardless of whether the duty cycle of the driving signal of the first switch tube in the balancing unit is d>0.5 or d≤0.5, i 2a and i 2b Substituting the specific expression of into (30), we can get (31),

[0109] I L2a ·d·T Buck (p+1)+I L2b ·d·T Buck p=I L2a ·d·T Buck p+I L2b ·d·

[0110] T Buck ·(p+1) (31)

[0111] Simplifying (31) we can obtain (32).

[0112] I L2a =I L2b (32)

[0113] In one cycle [0, T1] of the driving signal of the switch tube in the first-stage structure 11, the first capacitor C1 is charged in the first half cycle [0, T1 / 2], and discharged in the second half switching cycle [T1 / 2, T1]. The charge and discharge are balanced in steady state. The ampere-second balance equation for the first capacitor C1 is as follows:

[0114]

[0115] Regardless of whether the duty cycle of the driving signal of the first switch in the balancing unit is d>0.5 or d≤0.5, substituting the specific expressions of i1 and i2 into (33), we can obtain (34):

[0116] [I L1a ·d·T Buck (p+1)+I L1b ·d·T Buck ·p]·(q+1)+[I L2a ·d·T Buck (p+1)+I L2b ·d·T Buck ·p]·q=

[0117] [I L1a ·d·T Buck (p+1)+I L1b ·d·T Buck ·p]·q+[I L2a ·d·T Buck ·(p+1)9I L2b ·d·T Buck ·p]·(q+1) (34)

[0118] Substituting (29) and (32) into (34) yields (35).

[0119] I L1a =I L1b =I L2a =I L2b (35)

[0120] The above proves that when f2=(2q+1)f1, where q=0, 1, 2, 3, ..., the output currents of the balancing units are evenly distributed.

[0121] The following proves that when f1=(2q+1)f2, where q=0,1,2,3…, the voltage of the flying capacitor can be automatically balanced. Figures 8(a) and 8(b) show the second working waveform of the second power converter of the embodiment of the present invention, where f1=(2q+1)f2, q=0,1,2,3…. Figure 6 , Figure 8(a) and Figure 8(b) illustrate the working principle of the power converter. Figure 6 FIG8( b ) is the working waveform of the first balancing unit and the second balancing unit in the power converter shown in FIG8( b ). Figure 6 The working waveforms of the third balancing unit and the fourth balancing unit in the power converter are shown.

[0122] As shown in Figure 8(a), in a cycle [0, T2], for L 1a , L 1bThe volt-second balance equation written separately can be transformed into:

[0123]

[0124]

[0125] Similarly, as shown in Figure 8(b), in a cycle [0, T2], for L 2a , L 2b The volt-second balance equation written separately can be converted to:

[0126]

[0127]

[0128] Combining (36) with (37) yields (40). Combining (38) with (39) yields (41). Combining (37) with (38) yields (42).

[0129] V in (q+1) = V C1 (2q+1)+2V C21 (40)

[0130] V in q+2V C22 =V C1 ·(2q+1) (41)

[0131] V in ·p+V C21 +V C22 =V C1 ·(2p+1) (42)

[0132] Combining (40) with (41), we can eliminate V C1 , we get (43). Substituting (43) into (42) we get (44).

[0133] V in =2(V C21 +V C22 ) (43)

[0134] V C1 =V in / 2 (44)

[0135] Substituting (44) into (40) and (41), we can obtain (25) and (26). Therefore, when f1 = (2q + 1) f2, the flying capacitors C1 and C 21 and C 22 The voltage balance is demonstrated.

[0136] It is proved below that when f1=(2q+1)f2, the output currents of the balancing units are evenly distributed.

[0137] First, it is proved that the output current of the first balancing unit 1a and the second balancing unit 1b are equal. As shown in Figure 8(a), the charge and discharge are balanced in steady state. Regardless of whether the duty cycle of the driving signal of the first switch tube in the balancing unit is d>0.5 or d≤0.5, according to the i shown in Figure 8(a) 1a and i 1b , for the cross-over capacitor C 21 The ampere-second balance equation can be converted to:

[0138] I L1a ·d·T Buck (p+1)+I L1b ·d·T Buck p=I L1a ·d·T Buck p+I L1b ·d·T Buck ·(p+1) (45)

[0139] Simplifying (45), we can get (46):

[0140] I L1a =I L1b (46)

[0141] Secondly, it is proved by the same logic that when the charge and discharge are balanced in the steady state, no matter the duty cycle of the driving signal of the first switch tube in the balancing unit is d>0.5 or d≤0.5, as shown in FIG8(b) 2a and i 2b , the output current of the third balancing unit 2a and the fourth balancing unit 2b is equal, for C 22 The ampere-second balance equation can be obtained as equation (47),

[0142] I L2a ·d·T Buck (p+1)+I L2b ·d·T Buck p=I L2a ·d·T Buck p+I L2b ·d·T Buck ·(p+1) (47)

[0143] Simplifying (47) gives (48).

[0144] I L2a =I L2b (48)

[0145] In one cycle [0, T1] of the driving signal of the switch tube in the first-stage structure, the first capacitor C1 is charged in the first half cycle [0, T1 / 2], and discharged in the second half switching cycle [T1 / 2, T1]. The charging and discharging are balanced in the steady state. For the ampere-second balance equation (33) of the first capacitor C1, no matter the duty cycle d>0.5 or d≤0.5 of the driving signal of the first switch tube in the balancing unit, i 1a ,i 1b ,i 2a and i 2b Substituting the specific expression of into (33), we can get (49),

[0146] I L1a ·d·T Buck (p+1)+I L1b ·d·T Buck p=I L2a ·d·T Buck p+I L2b ·d·T Buck ·(p+1) (49)

[0147] Substituting (46) and (48) into (49) yields equation (35), which proves that when f1 = (2q + 1) f2, the output currents of the balancing units are evenly distributed.

[0148] Fig. 9 FIG. 1 is a schematic diagram of the structure of a third power conversion module according to an embodiment of the present invention. Fig. 9 As shown, in a more general case, the power conversion module includes N-level structures, and the i-th level structure consists of 2 i-1 The first basic unit of the first level structure is composed of a plurality of basic units, and the second end of each basic unit in each level structure is respectively connected to the first end of two basic units in the next level structure, that is, the output end of the mth basic unit in the previous level structure is connected to the input end of the 2mth basic unit and the 2m-1th basic unit in the next level structure; the input end of the first basic unit in the first level structure is connected to an external power supply, wherein N is a natural number greater than or equal to 2, i and m are both positive integers, and 1≤i≤N-1, 1≤m≤2 i-1 ; The Nth level structure includes 2 N-1 The output ends of the balancing units are connected as the output ends of the power conversion module, and the second ends of the basic units in the N-1th level structure are respectively connected to the first ends of the two balancing units, that is, the output end of the nth basic unit in the N-1th level structure is connected to the input ends of the 2nth balancing unit and the 2n-1th balancing unit in the Nth level structure, wherein n is a positive integer, 1≤n≤2 N-2The two first switching tubes in the two basic units or the balancing unit in the next stage structure connected to the second end of the same basic unit in the previous stage structure work in staggered phases, with a phase difference of 180°; the duty cycle d of the driving signal of the first switching tube in each balancing unit is equal; the duty cycle of the driving signal of each switching tube in each basic unit is 0.5; the state of the first switching tube and the third switching tube in each basic unit is the same, and the state of the second switching tube and the fourth switching tube is the same and complementary to the state of the first switching tube; the switching frequency of the previous stage basic unit is an odd multiple or one-half of the odd multiple of the switching frequency of the next stage basic unit; the switching frequency of the balancing unit is an odd multiple of the highest switching frequency among all basic units. The first switch tubes in each basic unit in the previous level structure and the first switch tubes in one of the basic units or the balancing unit in the next level structure connected to the basic unit where the first switch tube is located, the two first switch tubes start to conduct at the same time; that is, the first switch tube in the mth basic unit in the i-th level structure and the first switch tube in the 2m-1th or 2mth basic unit in the i+1th level structure start to conduct at the same time. When the two first switch tubes are both turned on at a high level, the time when the driving signals of the two first switch tubes start at a high level is aligned. The output voltage V out =d·V in / 2 N-1 , output voltage V out The output voltage V out Less than the input voltage V in When the duty cycle d is constant, the voltage transformation ratio can be improved compared with the three-level Buck circuit in the prior art, and the larger the number of stages N, the larger the output voltage V out Compared to input voltage V in The larger the voltage transformation ratio.

[0149] It can be deduced from N=2 and N=3 that the power converter of any number N can automatically achieve voltage balance of the cross-capacitors in each basic unit, and the voltage of the cross-capacitors in the basic unit in the j-th level structure is stable at V in / 2 j , where V in is the voltage input to the first end of the power conversion module, j is a natural number, 1≤j≤N-1; the output current of each balancing unit can achieve current balance; however, as the number of stages N increases, the number of switching tubes increases, and the reliability of the power conversion module will decrease. Therefore, in actual applications, power conversion modules with N=2 and N=3 are more common.

[0150] It should be noted that the switching frequency of the previous basic unit can be an odd multiple or one-half of the odd multiple of the next basic unit; for each level, the higher the switching frequency, the smaller the capacitance required for the jumper capacitor, which can reduce the volume and cost of the jumper capacitor, but at the same time means that the switching loss increases. Conversely, reducing the switching frequency can reduce switching losses, but at the same time requires a flying capacitor with a larger capacitance. Therefore, the choice of switching frequency for each level needs to be considered in a compromise based on actual conditions. At the same time, the more the previous level, the higher the voltage resistance requirements of the switch tube and capacitor, and the switching frequency should not be too high at this time; the more the later level, the lower the voltage resistance requirements of the switch tube and capacitor, and the switching frequency can usually be higher at this time.

[0151] Furthermore, in the above embodiment, the first end of the power conversion module is an input end for receiving an external power source, and the second end is an output end for outputting a signal; Fig.10 As shown, when the second end of the power conversion module is the input end to receive the external power supply, and the first end of the power conversion module is the output end to output the signal, that is, the input end and the output end of the power conversion module in the above embodiment are swapped, the composition of the balancing module and the basic unit in each level structure remains unchanged, and the relationship between the driving signals of the power tubes between each level remains unchanged. The only difference is that the currents of each balancing unit and each basic unit flow in opposite directions, and the input end and the output end of each balancing unit and each basic unit are swapped, that is, the balancing unit is converted from a Buck circuit to a Boost circuit, and the first end of the power conversion module after conversion outputs a voltage V out Greater than the voltage V of the external power supply input at the second terminal in , and satisfy V out =2 N-1 ·V in / (1-d).

[0152] Furthermore, the present embodiment also discloses a power converter, which includes a control module and the power conversion module described in the previous example, wherein the control module is used to generate a driving signal for each switching tube in the power conversion module to control the state of each switching tube in the power conversion module.

[0153] In summary, an embodiment of the present invention provides a power conversion module, wherein the power conversion module includes an N-level structure, wherein the i-th level structure is composed of 2 i-1 The first level structure is composed of two basic units, the second end of each basic unit in each level structure is respectively connected to the first end of two basic units in the next level structure; the first end of the first basic unit in the first level structure serves as the first end of the power conversion module, wherein N is a natural number greater than or equal to 2, i is a positive integer, and 1≤i≤N-1; the Nth level structure includes 2 N-1The invention comprises a balancing unit, the second end of each balancing unit is connected as the second end of the power conversion module, and the second end of each basic unit in the N-1th level structure is respectively connected to the first end of two balancing units; the basic unit is a switch capacitor circuit; by controlling the state of the switch tubes in each of the basic units and the balancing unit, when the power conversion module works in a steady state, the voltage of the cross-connected capacitor in the basic unit is basically stable, and the current flowing through the second end of each of the balancing units is equal. The present invention retains the advantages of the three-level Buck DC-DC power converter in the background technology, such as reducing the withstand voltage requirements of the power tube, using a smaller power inductor, and improving the power density; in addition, the present invention does not require an additional control strategy to ensure the current sharing of each inductor current, which solves the problem that the three-level Buck cannot automatically achieve voltage balance across the flying capacitor; and can provide a higher voltage ratio without changing the duty cycle of the balancing unit.

[0154] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A power conversion module, characterized in that: The power conversion module comprises an N-level structure, wherein the i-th level structure comprises 2 i-1 The power conversion module is composed of a plurality of basic units, wherein the second end of each basic unit in each level structure is respectively connected to the first ends of two basic units in the next level structure; the first end of the first basic unit in the first level structure serves as the first end of the power conversion module, wherein N is a natural number greater than or equal to 2, i is a positive integer, and 1≤i≤N-1; The Nth level structure includes 2 N-1 A balancing unit, the second end of each balancing unit is connected to serve as the second end of the power conversion module, the second end of each basic unit in the N-1th level structure is respectively connected to the first end of the two balancing units, and the balancing unit does not include a cross-over capacitor; The basic unit is a switched capacitor circuit; by controlling the states of the switch tubes in each of the basic units and the balancing unit, when the power conversion module operates in a steady state, the voltages of all the cross-capacitors are substantially constant, and the currents flowing through the second ends of each of the balancing units are equal.

2. The power conversion module according to claim 1, characterized in that: The balancing unit includes: an inductor and two first switching tubes and a second switching tube connected in series between a first end of the balancing unit and a reference ground, wherein a common connection end of the first switching tube and the second switching tube is connected to one end of the inductor, and the other end of the inductor is connected to the second end of the balancing unit.

3. The power conversion module according to claim 2, characterized in that: The second switch tube is replaced by a diode.

4. The power conversion module according to claim 2, characterized in that: The first switch tubes in the two balancing units connected to the second end of the same basic unit in the N-1th level structure operate in phase shift, with a phase difference of 180°.

5. The power conversion module according to claim 2, characterized in that: The duty cycles of the first switching tubes in each balancing unit are the same.

6. The power conversion module according to claim 1, characterized in that: The basic unit includes a jumper capacitor and four switch tubes connected in series between the first end of the basic unit and the reference ground: a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; the jumper capacitor is connected between the first connection end and the second connection end; the first connection end is the common connection end of the first switch tube and the second switch tube, and the second connection end is the common connection end of the third switch tube and the fourth switch tube; the common connection end of the second switch tube and the third switch tube is the second end of the basic unit.

7. The power conversion module according to claim 6, characterized in that: The switching states of the first switch tube and the third switch tube in each basic unit are the same, and the switching states of the second switch tube and the fourth switch tube are the same and complementary to the switching state of the first switch tube.

8. The power conversion module according to claim 6, characterized in that: The first switch tubes in the two basic units in the subsequent structure connected to the second end of the same basic unit operate in phase shift, with a phase difference of 180°.

9. The power conversion module according to claim 6, characterized in that: The duty cycle of each switch tube in each basic unit is 0.

5.

10. The power conversion module according to claim 6, characterized in that: When the power conversion module operates in a steady state, the voltage of the jumper capacitor in the j-th structure is stabilized at V in / 2 j , where V in is the voltage of the first end of the power conversion module, j is a natural number, and 1≤j≤N-1.

11. The power conversion module according to claim 1, characterized in that: The switching frequencies of the switches in the basic units in two adjacent stages satisfy the following condition: the switching frequency of the previous stage basic unit is k times or 1 / k of the switching frequency of the next stage basic unit, where k is an odd number.

12. The power conversion module according to claim 1, characterized in that: The switching frequency of the switch tube in the balancing unit is an odd multiple of the highest switching frequency in the first to N-1th level structures.

13. The power conversion module according to claim 1, characterized in that: The first switch tube in the basic unit in the previous stage structure and the first switch tube in one of the basic units or the balancing unit in the next stage structure connected to the basic unit have the same start-to-conduct time.

14. The power conversion module according to any one of claims 1 to 13, characterized in that: The first end of the power conversion module is an input end connected to an external power source, and the second end of the power conversion module is an output end.

15. The power conversion module according to any one of claims 1 to 13, characterized in that: The second end of the power conversion module is an input end connected to an external power source, and the first end of the power conversion module is an output end.

16. A power converter, comprising a control module and the power conversion module according to any one of claims 1 to 15, wherein the control module is used to generate a drive signal for each switch tube in the power conversion module to control the state of each switch tube in the power conversion module.

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