CN111682756A - Hybrid power converter and control method thereof - Google Patents
Hybrid power converter and control method thereof Download PDFInfo
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- CN111682756A CN111682756A CN202010516334.XA CN202010516334A CN111682756A CN 111682756 A CN111682756 A CN 111682756A CN 202010516334 A CN202010516334 A CN 202010516334A CN 111682756 A CN111682756 A CN 111682756A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
Abstract
The application discloses a hybrid power converter and a control method thereof. The hybrid power converter includes: an inductor connected to a first terminal of the hybrid power converter; and a switched capacitor network connected between the inductor and the second terminal of the hybrid power converter, wherein the switched capacitor network includes a plurality of switching elements and a plurality of capacitors, and controls the plurality of switching elements to be turned on and off according to a plurality of control signals, so as to periodically change a connection path of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged, and the hybrid power converter adjusts a duty ratio of the control signals, so as to convert an input voltage into a desired output voltage. The hybrid power converter can improve the output voltage regulation capability of the circuit, realize the miniaturization of the circuit and improve the conversion efficiency of the circuit.
Description
Technical Field
The present invention relates to a power converter, and more particularly, to a hybrid power converter having both an inductor and a capacitor as energy storage elements and a control method thereof.
Background
A power converter is a power module that converts an input voltage waveform to a desired output voltage or output current. The power converter comprises a switching element and an energy storage element, wherein the switching element is periodically switched on and off according to a control signal, and the energy storage element correspondingly stores electric energy and releases the electric energy, so that an output voltage signal is provided at the output end of the power converter.
In a power converter using an inductor as an energy storage element, a feedback loop is used to adjust the duty cycle of a control signal, so that a substantially constant output voltage or output current can be obtained. In a power converter having a capacitor as an energy storage element, the on time and off time of a switching element are larger than a charging time constant and a discharging time constant, and an output voltage in a fixed ratio to an input voltage is obtained in a steady state.
Fig. 1a and 1b show a schematic circuit diagram of a switched capacitor network power converter and an operation waveform diagram of a control signal, respectively, according to the prior art. In the power converter, the switching elements Q1 and Q2 are alternately turned on and off, the capacitor C1 is periodically charged and discharged to transmit electric energy from the input terminal to the output terminal, and the output capacitor Co is connected to the output terminal to filter out ripples to obtain a stable output voltage, for example, 1: 1, fixed ratio output voltage. Compared with a power converter adopting an inductor, the power converter adopting the switched capacitor topology has the advantages of small capacitor size, high circuit conversion efficiency and power density and low voltage stress of a switching element, but has the defects of difficulty in flexibly adjusting output voltage, large number of switching elements and difficulty in designing a control circuit.
Therefore, there is a need to develop a new hybrid power converter circuit that combines the advantages of the conventional inductor and capacitor power converter to provide a power solution with high conversion efficiency and high power density.
Disclosure of Invention
In view of the above, the present invention provides a hybrid power converter, in which an inductor and a capacitor are used as energy storage elements, and a plurality of switching elements are used to periodically change the connection paths of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged to obtain an output voltage adjustable within a predetermined voltage range.
According to a first aspect of the present invention, there is provided a hybrid power converter comprising: an inductor connected to a first terminal of the hybrid power converter; and a switched capacitor network connected between the inductor and the second terminal of the hybrid power converter, wherein the switched capacitor network includes a plurality of switching elements and a plurality of capacitors, and controls the plurality of switching elements to be turned on and off according to a plurality of control signals, so as to periodically change a connection path of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged, and the hybrid power converter adjusts a duty ratio of the control signals, so as to convert an input voltage into a desired output voltage.
Preferably, the plurality of switching elements of the switched capacitor network comprises: a first set of switching elements comprising a first switching element and a second switching element connected in series between a second terminal of the power converter and ground, the first switching element and the second switching element forming a first node; a second set of switching elements comprising a fourth switching element and a third switching element connected in series between a second terminal of the power converter and ground, the fourth and third switching elements forming a second node; and a third set of switching elements connected in series with the inductor between the first and second terminals of the power converter, the third set of switching elements forming a third set of nodes with the inductor and with each other, wherein the first terminals of the plurality of capacitors are sequentially connected to respective nodes of the third set of nodes and the second terminals are alternately connected to one of the first and second nodes.
Preferably, the number of the third group of switching elements is the same as the number of the plurality of capacitors.
Preferably, the plurality of control signals include a first control signal and a second control signal, which are periodic signals including an on time and an off time, respectively, and are complementary to each other.
Preferably, control terminals of odd-numbered ones of the first, fourth and third sets of switching elements receive the first control signal, and control terminals of even-numbered ones of the second, third and third sets of switching elements receive the second control signal.
Preferably, the number of the plurality of capacitors is selected in the switched capacitor network to obtain a predetermined voltage range, and the duty ratio of the first control signal and the second control signal is adjusted to obtain a desired output voltage in the predetermined voltage range.
Preferably, a first terminal of the hybrid power converter is provided as an input terminal to receive the input voltage, a second terminal of the power converter is provided as an output terminal to provide the output voltage, and the hybrid power converter operates as a buck converter.
Preferably, the output voltage in a steady state in consecutive switching cycles of the hybrid power converter is Vo ═ Vi/(N +1-D), where Vo denotes the output voltage, Vi denotes the input voltage, D denotes the first control signal duty cycle, N denotes the number of capacitors, and N is a natural number equal to or greater than 2.
Preferably, the method further comprises the following steps: an output capacitance connected between the second terminal of the power converter and ground.
Preferably, the second terminal of the hybrid power converter is an input terminal for receiving the input voltage, the first terminal of the power converter is an output terminal for providing the output voltage, and the hybrid power converter operates as a boost converter.
Preferably, the output voltage in a steady state in successive switching cycles of the hybrid power converter is Vo ═ Vi (N +1-D), where Vo denotes the output voltage, Vi denotes the input voltage, D denotes the first control signal duty cycle, N denotes the number of capacitors, and N is a natural number equal to or greater than 2.
Preferably, the method further comprises the following steps: an output capacitance connected between the first terminal of the power converter and ground.
According to a second aspect of the present invention, there is provided a method of controlling a hybrid power converter, the power converter comprising an inductor and a switched capacitor network connected between a first terminal and a second terminal, the switched capacitor network comprising a plurality of switching elements and a plurality of capacitors, the method comprising: selecting a number of the plurality of capacitors in the switched capacitor network to obtain a predetermined voltage range; controlling the on and off of the plurality of switching elements with a periodic control signal to change a connection path of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged; and adjusting the duty cycle of the control signal to obtain a desired output voltage within the predetermined voltage range.
Preferably, the plurality of capacitors are sequentially connected to nodes of adjacent ones of the plurality of switching elements, and include a first group of capacitors having an odd ordinal number and a second group of capacitors having an even ordinal number.
Preferably, the step of controlling the on and off of the plurality of switching elements with the periodic control signal includes: connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, first terminals of remaining capacitors of the first set of capacitors to a second terminal of the power converter, the second terminals of the first set of capacitors all being connected to ground, and connecting the first terminal of the first capacitor of the second set of capacitors to the first terminal of the power converter, the first terminals of the remaining capacitors of the second set of capacitors being connected to ground, the second terminals of the second set of capacitors all being connected to the second terminal of the power converter, during a first time period of each switching cycle; and during a second time period of each switching cycle, connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, connecting first terminals of the remaining capacitors of the first set of capacitors to ground, connecting second terminals of the first set of capacitors to second terminals of the power converter, and connecting first terminals of the second set of capacitors to second terminals of the power converter, and connecting second terminals of the second set of capacitors to ground.
Preferably, the first ends of the first set of capacitors are connected to the second end of the power converter or ground via a respective one of the second set of capacitors, and the first ends of the second set of capacitors are connected to the second end of the power converter or ground via a respective one of the first set of capacitors.
According to the hybrid power converter of the above embodiment, the output voltage Vo proportional to the input voltage Vi is supplied, and a desired output voltage within a predetermined voltage range can be obtained by changing the duty ratio of the control signal. Therefore, the hybrid power converter can improve the output voltage regulation capability (regulation) of the circuit and obtain the expected conversion ratio.
According to the hybrid power converter of the above embodiment, an inductor is connected in series between the input terminal of the power converter and the switched capacitor network. Compared with the traditional power converter adopting the inductor, the volt-second product applied to the inductor when the switching element is switched on or switched off in one switching period is greatly reduced. The requirement of high conversion efficiency can be achieved even with small-sized inductors. Therefore, the hybrid power converter can reduce the size of the inductor to achieve miniaturization.
According to the hybrid power converter of the above embodiment, in the switched capacitor network, since the voltage stress of the switching element is smaller than the input voltage, it is allowed to employ the switching element of a low rated voltage. The use of a switching element with a low rated voltage has the advantage of low switching loss and low conduction loss compared to a switching element with a high rated voltage. Therefore, the hybrid power converter can operate at a high switching frequency while improving the conversion efficiency (high efficiency) of the circuit.
According to the hybrid power converter of the above embodiment, the inductor and the capacitor are used together as the energy storage element, and the energy density of the capacitor is much higher than that of the inductor. Compared with the traditional power converter only adopting inductance, the hybrid power converter has higher power density (high density). Compared with a traditional power converter only adopting a capacitor, the hybrid converter can realize output voltage regulation capability (regulation), smooth starting of a circuit (smooth starting) and current sharing among multiple circuits (scalability) by utilizing an inductor.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1a and 1b show a schematic circuit diagram of a switched capacitor network power converter and an operation waveform diagram of a control signal, respectively, according to the prior art.
Fig. 2a and 2b show a schematic circuit diagram of a hybrid power converter according to a first embodiment of the present invention and an operation waveform diagram of a control signal, respectively.
Fig. 3a and 3b show equivalent circuit diagrams of a hybrid power converter according to a first embodiment of the invention in a first phase and a second phase, respectively.
Fig. 4a and 4b show a schematic circuit diagram of a hybrid power converter according to a second embodiment of the present invention and an operation waveform diagram of a control signal, respectively.
Fig. 5a and 5b show equivalent circuit diagrams of a hybrid power converter according to a second embodiment of the present invention in a first phase and a second phase, respectively.
Fig. 6a and 6b show schematic circuit diagrams of a hybrid power converter according to a third embodiment of the present invention when the number of transistors is even and odd, respectively.
Fig. 6c shows a waveform diagram of the operation of the control signal of the hybrid power converter of fig. 6a and 6 b.
Fig. 7a and 7b show schematic circuit diagrams of a hybrid power converter according to a fourth embodiment of the present invention when the number of transistors is even and odd, respectively.
Fig. 7c shows a waveform diagram of the operation of the control signal of the hybrid power converter of fig. 7a and 7 b.
Fig. 8 shows a flowchart of a control method of a hybrid power converter according to a fifth embodiment of the present invention.
Detailed Description
The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale. Meanwhile, it should be understood that, in the following description, a "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to". In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
Fig. 2a and 2b show a schematic circuit diagram of a hybrid power converter according to a first embodiment of the present invention and an operation waveform diagram of a control signal, respectively. The power converter 20 receives an input voltage Vi between an input terminal and ground, and provides an output voltage Vo between an output terminal and ground. The power converter 20 includes an inductor Ls, a switched capacitor network including switching elements Q1 and Q2 and Qa through Qd, and capacitors C1 and C2, and an output capacitor Co.
In the power converter 20, a first terminal of an inductor Ls is connected to an input terminal of the power converter 20, a second terminal is connected to a switching element Q1, switching elements Q1 and Q2 are sequentially connected in series between the second terminal of the inductor Ls and an output terminal of the power converter 20, switching elements Qa and Qb are sequentially connected in series between the output terminal of the power converter 20 and ground, switching elements Qc and Qd are sequentially connected in series between the output terminal of the power converter 20 and ground, and an output capacitor Co is connected between the output terminal of the power converter 20 and ground. An intermediate node of the switching elements Qa and Qb is a first node, and an intermediate node of the switching elements Qc and Qd is a second node. A capacitor C1 is connected between the second terminal of the inductor Ls and the first node, and a capacitor C2 is connected between the intermediate node of the switching elements Q1 and Q2 and the second node.
The switching element includes any one selected from a field effect transistor and a bipolar transistor. In this embodiment, the switching element is, for example, an N-type MOSFET, however, the present invention is not limited thereto. The gates of the switching elements Q1, Qa, and Qd receive the control signal G1, and the gates of the switching elements Q2, Qb, and Qc receive the control signal G2. The control signals G1 and G2 are periodic signals each including an on-time Ton and an off-time Toff in each switching period T, and the control signals G1 and G2 are complementary to each other, i.e., the control signal G2 is inactive when the control signal G1 is active, and vice versa. For the sake of clarity, the control circuits for generating the control signals G1 and G2 are not shown in the figure. As described below, the control circuit may adjust the duty cycle D of the control signal G1, i.e., D ═ Ton/(Ton + Toff), to change the proportional relationship between the output voltage Vo and the input voltage Vi, and thus the desired output voltage Vo.
During the operation of the power converter 20, the control signals G1 and G2 in the power converter 20 periodically change, and the on states of the switching elements Q1 and Q2 and Qa to Qd correspondingly change, so that the connection relationships of the capacitors C1 and C2 are different at different stages of the switching period T, and the charging and discharging states correspondingly change.
As shown in fig. 3a, in the first period of the switching period T, i.e. the period from T0 to T1, the control signal G1 is active and the control signal G2 is inactive, the switching elements Q1, Qa and Qd are turned on, and the switching elements Q2, Qb and Qc are turned off. A capacitor C1 is connected between the second terminal of the inductor Ls and ground, and a capacitor C2 is connected between the second terminal of the inductor Ls and the output terminal of the power converter 20. The input voltage Vi of the power converter 20 charges the inductor Ls and the capacitor C2, while providing power to the output of the power converter 20. The capacitor C1 charges the capacitor C2 while discharging through the capacitor C2.
As shown in fig. 3b, in the second period of the switching period T, i.e., the period from time T1 to time T2, the control signal G1 is inactive and the control signal G2 is active, the switching elements Q1, Qa and Qd are turned off, and the switching elements Q2, Qb and Qc are turned on. The capacitor C1 is connected between the second terminal of the inductor Ls and the output terminal of the power converter 20, and the capacitor C2 is connected between the output terminal of the power converter 20 and ground. The inductor Ls charges the capacitor C1 while discharging through the capacitor C1, and simultaneously provides power to the output of the power converter 20. The capacitor C2 discharges to provide power to the output of the power converter 20.
In continuous switching cycles, according to the charge balance principle of the capacitors in the switched capacitor network, the direct-current voltage Vc1 on the capacitor C1 is equal to 2Vo and the direct-current voltage Vc2 on the capacitor C2 is equal to Vo in a steady state. As shown in fig. 3a, in the first period of the switching period T, i.e. the period from T0 to T1, the voltage at the second end of the inductor Ls is equal to (Vc1 ═ Vc2+ Vo ═ 2 Vo). As shown in fig. 3b, in the second period of the switching period T, i.e. the period from time T1 to T2, the voltage at the second end of the inductor Ls is equal to (Vc1+ Vo — 3 Vo). The voltage at the first terminal of the inductor Ls is equal to Vi during the entire switching period.
From the volt-second balance principle of the inductance, (Vi-2Vo) × Ton + (Vi-3Vo) × Toff ═ 0, it can be deduced that: during successive switching cycles, the output voltage Vo of the power converter 20 in steady state is as follows,
Vo＝Vi/(3-D) (1)，
where Vi denotes the input voltage and D denotes the duty cycle of the control signal G1.
The power converter according to the first embodiment, operating as a buck converter, provides an output voltage Vo proportional to the input voltage Vi. The number of capacitors in the switched capacitor network is 2 to obtain a predetermined voltage range of Vi/2 to Vi/3. Further, within the predetermined voltage range, a desired output voltage may be obtained by adjusting the duty ratio D of the control signal. Therefore, the power converter can improve the output voltage regulation capability (regulation) of the circuit and obtain the expected conversion ratio.
Fig. 4a and 4b show a schematic circuit diagram of a hybrid power converter according to a second embodiment of the present invention and an operation waveform diagram of a control signal, respectively. The power converter 30 receives an input voltage Vi between an input terminal and ground, and provides an output voltage Vo between an output terminal and ground. The power converter 30 includes an inductor Ls, a switched capacitor network including switching elements Q1-Q3 and Qa-Qd, and capacitors C1-C3, and an output capacitor Co.
In the power converter 30, a first terminal of an inductor Ls is connected to an input terminal of the power converter 30, a second terminal is connected to a switching element Q1, switching elements Q1 to Q3 are sequentially connected in series between the second terminal of the inductor Ls and an output terminal of the power converter 30, switching elements Qa and Qb are sequentially connected in series between the output terminal of the power converter 30 and ground, switching elements Qc and Qd are sequentially connected in series between the output terminal of the power converter 30 and ground, and an output capacitor Co is connected between the output terminal of the power converter 30 and ground. An intermediate node of the switching elements Qa and Qb is a first node, and an intermediate node of the switching elements Qc and Qd is a second node. A capacitor C1 is connected between the second terminal of the inductor Ls and the first node, a capacitor C2 is connected between the second node and the intermediate node of the switching elements Q1 and Q2, and a capacitor C3 is connected between the first node and the intermediate node of the switching elements Q2 and Q3.
The switching element includes any one selected from a field effect transistor and a bipolar transistor. In this embodiment, the switching element is, for example, an N-type MOSFET, however, the present invention is not limited thereto. The gates of the switching elements Q1, Q3, Qa, and Qd receive the control signal G1, and the gates of the switching elements Q2, Qb, and Qc receive the control signal G2. The control signals G1 and G2 are periodic signals each including an on-time Ton and an off-time Toff in each switching period T, and the control signals G1 and G2 are complementary to each other, i.e., the control signal G2 is inactive when the control signal G1 is active, and vice versa. For the sake of clarity, the control circuits for generating the control signals G1 and G2 are not shown in the figure. As described below, the control circuit may adjust the duty cycle D of the control signal G1, i.e., D ═ Ton/(Ton + Toff), to change the proportional relationship between the output voltage Vo and the input voltage Vi, and thus the desired output voltage Vo.
During the operation of the power converter 30, the control signals G1 and G2 in the power converter 30 periodically change, and the on states of the switching elements Q1 to Q3 and Qa to Qd correspondingly change, so that the connection relationships of the capacitors C1 to C3 are different at different stages of the switching period T, and the charging and discharging states correspondingly change.
As shown in fig. 5a, in the first period of the switching period T, i.e. the period from T0 to T1, the control signal G1 is active and the control signal G2 is inactive, the switching elements Q1, Q3, Qa and Qd are turned on, and the switching elements Q2, Qb and Qc are turned off. The capacitor C1 is connected between the second terminal of the inductor Ls and ground, the capacitor C2 is connected between the second terminal of the inductor Ls and the output terminal of the power converter 30, and the capacitor C3 is connected between the output terminal of the power converter 30 and ground. The input voltage Vi of the power converter 30 charges the inductor Ls and the capacitor C2, while providing power to the output of the power converter 30. The capacitor C1 charges the capacitor C2 while discharging through the capacitor C2. Capacitor C3 discharges to provide power to the output of power converter 30.
As shown in fig. 5b, in the second period of the switching period T, i.e., the period from time T1 to T2, the control signal G1 is inactive and the control signal G2 is active, the switching elements Q1, Q3, Qa and Qd are turned off, and the switching elements Q2, Qb and Qc are turned on. A capacitor C1 is connected between the second terminal of the inductor Ls and the output of the power converter 30, and capacitors C2 and C3 are connected in series between the output of the power converter 30 and ground. The inductor Ls charges the capacitor C1 while discharging through the capacitor C1, and simultaneously provides power to the output of the power converter 30. The capacitor C2 charges the capacitor C3 while discharging via the capacitor C3 and provides power to the output of the power converter 30.
In continuous switching cycles, according to the charge balance principle of the capacitors in the switched capacitor network, the direct-current voltage Vc1 on the capacitor C1 is equal to 3Vo, the direct-current voltage Vc2 on the capacitor C2 is equal to 2Vo, and the direct-current voltage Vc3 on the capacitor C3 is equal to Vo in a steady state. As shown in fig. 5a, in the first period of the switching period T, i.e. the period from T0 to T1, the voltage at the second end of the inductor Ls is equal to (Vc1 ═ Vc2+ Vo ═ 3 Vo). As shown in fig. 5b, in the second period of the switching period T, i.e. the period from time T1 to T2, the voltage at the second end of the inductor Ls is equal to (Vc1+ Vo is 4 Vo).
From the volt-second balance principle of the inductance, (Vi-3Vo) × Ton + (Vi-4Vo) × Toff ═ 0, it can be deduced that: during successive switching cycles, the output voltage Vo of power converter 30 in steady state is as follows,
Vo＝Vi/(4-D) (2)，
where Vi denotes the input voltage and D denotes the duty cycle of the control signal G1.
The power converter according to the second embodiment, operating as a buck converter, provides an output voltage Vo proportional to the input voltage Vi. The number of capacitors in the switched capacitor network is 3 to obtain a predetermined voltage range of Vi/3 to Vi/4. Further, within the predetermined voltage range, a desired output voltage may be obtained by adjusting the duty ratio D of the control signal. Therefore, the power converter can improve the output voltage regulation capability (regulation) of the circuit and obtain the expected conversion ratio.
Fig. 6a and 6b show schematic circuit diagrams of a hybrid power converter according to a third embodiment of the present invention when the number of transistors is even and odd, respectively, and fig. 6c shows an operation waveform diagram of a control signal of the hybrid power converter in fig. 6a and 6 b. The power converter 40 receives an input voltage Vi between an input terminal and ground, and provides an output voltage Vo between an output terminal and ground. The power converter 40 includes an inductor Ls, a switched capacitor network including switching elements Q1, Q2, Q3 through Q (n-1), Qn and Qa through Qd, capacitors C1, C2, C3 through Cn, and an output capacitor Co.
In the power converter 40, a first terminal of an inductor Ls is connected to an input terminal of the power converter 40, a second terminal is connected to a switching element Q1, and switching elements Q1, Q2, Q3 to Q (n-1), Qn are sequentially connected in series between the second terminal of the inductor Ls and an output terminal of the power converter 40, wherein switching elements Qa and Qb are sequentially connected in series between the output terminal of the power converter 40 and ground, switching elements Qc and Qd are sequentially connected in series between the output terminal of the power converter 40 and ground, and an output capacitor Co is connected between the output terminal of the power converter 40 and ground. An intermediate node of the switching elements Qa and Qb is a first node, and an intermediate node of the switching elements Qc and Qd is a second node. A capacitor C1 is connected between the second terminal of the inductor Ls and the first node, a capacitor C2 is connected between the second node and the intermediate node of the switching elements Q1 and Q2, and a capacitor C3 is connected between the first node and the intermediate node of the switching elements Q2 and Q3. When n is an even number, Q1, Q3, and Q (n-1) are respectively odd-numbered switching elements, and Q2 and Qn are respectively even-numbered switching elements. By analogy, the capacitor Cn is connected between the intermediate node of the switching elements Q (n-1) and Qn and the second node, as shown in fig. 6 a; when n is an odd number, Q1, Q3, and Qn are odd-numbered switching elements, respectively, and Q2 and Q (n-1) are even-numbered switching elements, respectively. By analogy, a capacitor Cn is connected between the intermediate node of the switching elements Q (n-1) and Qn and the first node, as shown in fig. 6 b.
The switching element includes any one selected from a field effect transistor and a bipolar transistor. In this embodiment, the switching element is, for example, an N-type MOSFET, however, the present invention is not limited thereto. The gates of the switching elements Q1, Q3, … …, Qm, Qa, and Qd receive the control signal G1, and the gates of the switching elements Q2, … …, Qn, Qb, and Qc receive the control signal G2. The control signals G1 and G2 are periodic signals each including an on-time Ton and an off-time Toff in each switching period T, and the control signals G1 and G2 are complementary to each other, i.e., the control signal G2 is inactive when the control signal G1 is active, and vice versa. For the sake of clarity, the control circuits for generating the control signals G1 and G2 are not shown in the figure. As described below, the control circuit may adjust the duty cycle D of the control signal G1, i.e., D ═ Ton/(Ton + Toff), to change the proportional relationship between the output voltage Vo and the input voltage Vi, and thus the desired output voltage Vo.
During the operation of the power converter 40, the control signals G1 and G2 in the power converter 40 periodically change, and the on states of the switching elements Q1, Q2, Q3 to Qm, Qn and Qa to Qd correspondingly change, so that the connection relationships of the capacitors C1 to C3 are different at different stages of the switching period T, and the charging and discharging states correspondingly change.
Based on the similar principle of the first and third embodiments described above, in successive switching cycles, the output voltage Vo of the power converter 40 in the steady state is as follows,
Vo＝Vi/(N+1-D) (3)，
where Vi denotes an input voltage, D denotes a duty ratio of the control signal G1, N denotes the number of capacitances, and N is a natural number equal to or greater than 2.
The power converter according to the third embodiment, operating as a buck converter, provides an output voltage Vo proportional to the input voltage Vi. The number of capacitors in the switched-capacitor network is N to obtain a predetermined voltage range of Vi/N to Vi/(N + 1). Further, within the predetermined voltage range, a desired output voltage may be obtained by adjusting the duty ratio D of the control signal. Therefore, the power converter can improve the output voltage regulation capability (regulation) of the circuit and obtain the expected conversion ratio.
Fig. 7a and 7b show schematic circuit diagrams of a hybrid power converter according to a fourth embodiment of the present invention when the number of transistors is even and odd, respectively, and fig. 7c shows an operation waveform diagram of a control signal of the hybrid power converter in fig. 7a and 7 b. The power converter 50 receives an input voltage Vi between an input terminal and ground, and provides an output voltage Vo between an output terminal and ground. The power converter 50 includes an inductor Ls, a switched capacitor network including switching elements Q1, Q2, Q3 to Qm, Qn and Qa to Qd, capacitors C1, C2, C3 to Cn, and an output capacitor Co.
In the power converter 50, a first terminal of an inductor Ls is connected to an output terminal of the power converter 50, a second terminal is connected to a switching element Q1, and the switching elements Q1, Q2, Q3 to Q (n-1), Qn are sequentially connected in series between the second terminal of the inductor Ls and an input terminal of the power converter 50. The switching elements Qa and Qb are sequentially connected in series between the input terminal of the power converter 50 and ground, the switching elements Qc and Qd are sequentially connected in series between the input terminal of the power converter 50 and ground, and the output capacitor Co is connected between the output terminal of the power converter 50 and ground. An intermediate node of the switching elements Qa and Qb is a first node, and an intermediate node of the switching elements Qc and Qd is a second node. A capacitor C1 is connected between the second terminal of the inductor Ls and the first node, a capacitor C2 is connected between the second node and the intermediate node of the switching elements Q1 and Q2, and a capacitor C3 is connected between the first node and the intermediate node of the switching elements Q2 and Q3. When n is an even number, Q1, Q3, and Q (n-1) are respectively odd-numbered switching elements, and Q2 and Qn are respectively even-numbered switching elements. By analogy, the capacitor Cn is connected between the intermediate node of the switching elements Q (n-1) and Qn and the second node, as shown in fig. 7 a; when n is an odd number, Q1, Q3, and Qn are odd-numbered switching elements, respectively, and Q2 and Q (n-1) are even-numbered switching elements, respectively. By analogy, a capacitor Cn is connected between the intermediate node of the switching elements Q (n-1) and Qn and the first node, as shown in fig. 7 b.
The switching element includes any one selected from a field effect transistor and a bipolar transistor. In this embodiment, the switching element is, for example, an N-type MOSFET, however, the present invention is not limited thereto. The gates of the switching elements Q1, Q3, … …, Qm, Qa, and Qd receive the control signal G1, and the gates of the switching elements Q2, … …, Qn, Qb, and Qc receive the control signal G2. The control signals G1 and G2 are periodic signals each including an on-time Ton and an off-time Toff in each switching period T, and the control signals G1 and G2 are complementary to each other, i.e., the control signal G2 is inactive when the control signal G1 is active, and vice versa. For the sake of clarity, the control circuits for generating the control signals G1 and G2 are not shown in the figure. As described below, the control circuit may adjust the duty cycle D of the control signal G1, i.e., D ═ Ton/(Ton + Toff), to change the proportional relationship between the output voltage Vo and the input voltage Vi, and thus the desired output voltage Vo.
During the operation of the power converter 50, the control signals G1 and G2 in the power converter 50 periodically change, and the on states of the switching elements Q1, Q2, Q3 to Qm, Qn and Qa to Qd correspondingly change, so that the connection relationships of the capacitors C1 to C3 are different at different stages of the switching period T, and the charging and discharging states correspondingly change.
Based on the similar principle of the first and fourth embodiments described above, in successive switching cycles, the output voltage Vo of the power converter 50 in the steady state is as follows,
Vo＝Vi*(N+1-D) (4)，
where Vi denotes an input voltage, D denotes a duty ratio of the control signal G1, N denotes the number of capacitances, and N is a natural number equal to or greater than 2.
The power converter according to the fourth embodiment, operating as a boost converter, provides an output voltage Vo proportional to the input voltage Vi. The number of capacitors in the switched capacitor network is N to obtain a predetermined voltage range from Vi x N to Vi (N + 1). Further, within the predetermined voltage range, a desired input voltage may be obtained by adjusting the duty ratio D of the control signal. Therefore, the power converter can improve the output voltage regulation capability (regulation) of the circuit and obtain the expected conversion ratio.
Fig. 8 shows a flowchart of a control method of a hybrid power converter according to a fifth embodiment of the present invention. This control method is applied to the hybrid power converter according to any one of the first to fourth embodiments described above.
The power converter includes an inductor and a switched capacitor network connected between a first terminal and a second terminal, wherein the switched capacitor network includes a plurality of switching elements and a plurality of capacitors. Referring to fig. 6a, capacitors C1, C2, C3 to Cn are connected in series to nodes of adjacent ones of a plurality of switching elements Q1, Q2, Q3 to Q (n-1), Qn, which when n is an even number, include a first group of odd numbered capacitors C1, C3 and a second group of even numbered capacitors C2, Cn. When n is an odd number, the plurality of capacitors includes a first group of capacitors C1, C3, and Cn numbered odd, and a second group of capacitors C2, C (n-1) numbered even.
In step S01, the number of the plurality of capacitors is selected in the switched capacitor network to obtain a predetermined voltage range.
In step S02, the plurality of switching elements are controlled to be turned on and off by a periodic control signal to change a connection path of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged.
In step S03, the duty cycle of the control signal is adjusted to obtain a desired output voltage within the predetermined voltage range.
Further, in the above-described step S02, different connection paths of the plurality of capacitances are formed in the first period and the second period of the switching cycle of the control signal, respectively.
In a first time period of each switching cycle, connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, connecting first terminals of remaining capacitors of the first set of capacitors to a second terminal of the power converter, the second terminals of the first set of capacitors all being connected to ground, and connecting the first terminal of the first capacitor of the second set of capacitors to the first terminal of the power converter, the first terminals of the remaining capacitors of the second set of capacitors being connected to ground, the second terminals of the second set of capacitors all being connected to the second terminal of the power converter.
During a second time period of each switching cycle, connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, connecting first terminals of remaining capacitors of the first set of capacitors to ground, connecting second terminals of the first set of capacitors to second terminals of the power converter, and connecting first terminals of the second set of capacitors to second terminals of the power converter, connecting second terminals of the second set of capacitors to ground.
For example, with continued reference to fig. 6a, a first terminal of a capacitor C3 of the first set of capacitors is connected to the second terminal of the power converter via a respective one of the capacitors C2 of the second set of capacitors or to ground via a respective one of the capacitors C4 of the second set of capacitors, and a first terminal of a second set of capacitors C2 is connected to the second terminal of the power converter via a respective one of the capacitors C3 of the first set of capacitors or to ground via a respective one of the capacitors C1 of the second set of capacitors.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The scope of the invention should be determined from the following claims.
Claims (16)
1. A hybrid power converter, comprising:
an inductor connected to a first terminal of the hybrid power converter;
a switched capacitor network connected between the inductor and the second terminal of the hybrid power converter,
wherein the switched capacitor network includes a plurality of switching elements and a plurality of capacitors, and controls the plurality of switching elements to be turned on and off according to a plurality of control signals, thereby periodically changing connection paths of the plurality of capacitors such that the inductor and the plurality of capacitors are charged and discharged,
the hybrid power converter adjusts the duty cycle of the control signal to convert the input voltage to a desired output voltage.
2. The hybrid power converter of claim 1, wherein the plurality of switching elements of the switched-capacitor network comprise:
a first set of switching elements comprising a first switching element and a second switching element connected in series between a second terminal of the power converter and ground, the first switching element and the second switching element forming a first node;
a second set of switching elements comprising a fourth switching element and a third switching element connected in series between a second terminal of the power converter and ground, the fourth and third switching elements forming a second node; and
a third set of switching elements connected in series with the inductor between the first and second terminals of the power converter, the third set of switching elements forming a third set of nodes with the inductor and with each other,
wherein the first ends of the plurality of capacitors are sequentially connected to respective nodes in the third set of nodes, and the second ends are alternately connected to one of the first nodes and the second nodes.
3. The hybrid power converter of claim 2, wherein the third set of switching elements is equal in number to the plurality of capacitors.
4. The hybrid power converter of claim 2, wherein the plurality of control signals comprises a first control signal and a second control signal, the first control signal and the second control signal being periodic signals comprising an on time and an off time, respectively, and complementary to each other.
5. The hybrid power converter of claim 4, wherein control terminals of odd-numbered ones of the first, fourth, and third sets of switching elements receive the first control signal and control terminals of even-numbered ones of the second, third, and third sets of switching elements receive the second control signal.
6. The hybrid power converter of claim 5, wherein a number of the plurality of capacitors is selected in the switched capacitor network to achieve a predetermined voltage range by adjusting duty cycles of the first and second control signals to achieve a desired output voltage within the predetermined voltage range.
7. The hybrid power converter of claim 5, wherein a first terminal of the hybrid power converter is configured as an input terminal to receive the input voltage, a second terminal of the power converter is configured as an output terminal to provide the output voltage, and the hybrid power converter operates as a buck converter.
8. The hybrid power converter of claim 7, wherein the output voltage at steady state during successive switching cycles of the hybrid power converter is as follows,
Vo＝Vi/(N+1-D)
where Vo represents the output voltage, Vi represents the input voltage, D represents the first control signal duty ratio, N represents the number of capacitors, and N is a natural number equal to or greater than 2.
9. The hybrid power converter of claim 7, further comprising: an output capacitance connected between the second terminal of the power converter and ground.
10. The hybrid power converter of claim 5, wherein the second terminal of the hybrid power converter serves as an input terminal to receive the input voltage, the first terminal of the power converter serves as an output terminal to provide the output voltage, and the hybrid power converter operates as a boost converter.
11. The hybrid power converter of claim 10, wherein the output voltage at steady state during successive switching cycles of the hybrid power converter is as follows,
Vo＝Vi*(N+1-D)
where Vo represents the output voltage, Vi represents the input voltage, D represents the first control signal duty ratio, N represents the number of capacitors, and N is a natural number equal to or greater than 2.
12. The hybrid power converter of claim 10, further comprising: an output capacitance connected between the first terminal of the power converter and ground.
13. A method of controlling a hybrid power converter, the power converter including an inductor and a switched capacitor network connected between a first terminal and a second terminal, the switched capacitor network including a plurality of switching elements and a plurality of capacitors, the method comprising:
selecting a number of the plurality of capacitors in the switched capacitor network to obtain a predetermined voltage range;
controlling the on and off of the plurality of switching elements with a periodic control signal to change a connection path of the plurality of capacitors, so that the inductor and the plurality of capacitors are charged and discharged; and
adjusting a duty cycle of the control signal to obtain a desired output voltage within the predetermined voltage range.
14. The control method of claim 13, wherein the plurality of capacitors are sequentially connected to nodes of adjacent ones of the plurality of switching elements and comprise a first set of odd numbered capacitors and a second set of even numbered capacitors.
15. The control method of claim 14, wherein the step of controlling the turning on and off of the plurality of switching elements with the periodic control signal comprises:
connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, first terminals of remaining capacitors of the first set of capacitors to a second terminal of the power converter, the second terminals of the first set of capacitors all being connected to ground, and connecting the first terminal of the first capacitor of the second set of capacitors to the first terminal of the power converter, the first terminals of the remaining capacitors of the second set of capacitors being connected to ground, the second terminals of the second set of capacitors all being connected to the second terminal of the power converter, during a first time period of each switching cycle; and
during a second time period of each switching cycle, connecting a first terminal of a first capacitor of the first set of capacitors to a first terminal of the power converter, connecting first terminals of remaining capacitors of the first set of capacitors to ground, connecting second terminals of the first set of capacitors to second terminals of the power converter, and connecting first terminals of the second set of capacitors to second terminals of the power converter, connecting second terminals of the second set of capacitors to ground.
16. The control method of claim 15, wherein a first end of the first set of capacitors is connected to a second end of the power converter or ground via a respective one of the second set of capacitors, and a first end of the second set of capacitors is connected to the second end of the power converter or ground via a respective one of the first set of capacitors.
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