Patent ID: 12237764

DETAILED DESCRIPTION

Disclosed herein are various embodiments of methods related to switching methods for regulating resonant switched-capacitor converters (RSCCs). RSCCs have improved voltage regulation capability compared to SCCs. However, full-range voltage regulation for all load levels has been difficult to achieve. Reference will now be made in detail to the description of the embodiments as illustrated in the drawings, wherein like reference numbers indicate like parts throughout the several views.

FIGS.1and2show examples of timing diagrams for RSCC switching methods. Under the switching method illustrated inFIG.1, the waveform of the inductor current is half of the sinusoid during states 2 and 4 respectively, while the duration of idle state 5 is adjusted to regulate the voltage. Under the switching method illustrated inFIG.2, the waveform of the inductor current consists of four symmetric partial sinusoidal waveforms in operation states 1-4 without any idle state.

InFIG.2, when RSCCs operate in step-down voltage conversion, the switching sequence in each switching cycle is in a pattern of states 2, 1, 4 and 3. When RSCCs operate in step-up voltage conversion, the switching sequence in each switching cycle is in a pattern of states 4, 1, 2 and 3. The duration of each switching cycle can be denoted as Ts, which could be constant or variable. The duration of state 1 is equal to the duration of state 3. The duration of state 2 is equal to the duration of state 4. The duty cycle D is defined as the duration of the on-states (state 2 or state 4) divided by the duration of switching cycle. The current flow through the transistors is inverted during freewheeling state 1 and state 3. However, while RSCCs have improved voltage regulation capability compared to SCCs, full-range voltage regulation for all load levels has not been possible.

In the present disclosure, a general solution is provided for all RSCCs to achieve full-range voltage regulation for RSCCs with one or more resonant inductors. This can be achieved by controlling the switching sequence (or timing diagram) of the converters. Furthermore, this general solution can bring soft switching to all switching devices as an added benefit. Although, the disclosed switching method is applicable to a large number of converters, this disclosure will present examples that cover a subset of RSCCs that have the greatest potential for engineering applications.

The disclosed switching scheme is presented with respect to 14 switching methods (A-N) that use the combination of the states shown inFIGS.3A-3G. For example, switching methods G and N will use all the states shown inFIG.3G, while the others A and H (FIG.3A), B and I (FIG.3B), C and J (FIG.3C), D and K (FIG.3D), E and L (FIG.3E), and F and M (FIG.3F) will use a combination of part of the states. Therefore, the inductor current waveform can be half of the sinusoid or a part of the sinusoid during on-state 2 as well as on-state 4, while the freewheeling states 1 and 3 can be eliminated or minimized. Furthermore, the idle state 5 can also be eliminated. In some embodiments, the combination of states is arranged asymmetrically with respect to durations within one repetitive cycle, while others are symmetrical. The repetitive cycle can be variable or constant.

InFIGS.3A-3G, since the duration of state 2 and state 4 may not be equal for the 14 switching methods, the duty cycle D can be defined as the lesser of the two on-states (state 2 or state 4) divide by the duration of the switching cycle. The duration of each switching cycle can be denoted as TS.

Examples of RSCCs that can be controlled using these switching methods include, but are not limited to, the basic RSCC, inverse polarity RSCC, ladder RSCC, resonant two-switch boosting switched-capacitor converter (RTBSC), Dickson RSCC, series-parallel RSCC and Fibonacci RSCC. Fourteen switching sequences were applied to these circuits. Among these examples, the RSCCs without idle states are of particular interest due to their benefits of zero voltage switching (ZVS) turn-on of switches, ZCS turn-off of diodes, complementary driving signals without zero-current detection, simple half-bridge gate driver with bootstrap circuit, and soft switching commutation in spite of inductance and capacitance variations, in addition to full-range regulation.

FIGS.4and6-10show a set of RSCC examples, where the high dc voltage port is denoted as VHVand the low dc voltage port is denoted as VLV. The filter capacitors are labeled as Co1and Co2, which is connected across the two dc ports respectively. The value of these filter capacitors can be minimized or zero depending on the application. When any of the converters operates in step-down conversion, the voltage source is applied to the port denoted as VHVand the load is applied to the port denoted as VLV. When any of the converters operates in step-up conversion, the voltage source is applied to the port denoted as VLVwhile the load is applied to the port denoted as VHV.

The circuit shown inFIG.4is known as the basic RSCC. The switches Q1, Q2, Q3and Q4can be either transistors or diodes. The resonant capacitor Crand the resonant inductor Lrare connected in series.

FIG.5shows an example of the circuit of an inverse polarity RSCC. The switches Q1, Q2, Q3and Q4can be either transistors or diodes. The resonant capacitor Crand the resonant inductor Lris series connected. The dc voltage ports are denoted as V1and V2. There are two types of ports polarity definition. The first type defines the common negative polarity of V1and V2while second type defines the common positive polarity of V1and V2by swapping the ports polarity.

FIG.6shows an example of the circuit of a ladder RSCC. The switches Qi(i=1, 2, 3, . . . , 2n) can be transistors or diodes, while the capacitors are Ci(i=1, 2, 3, . . . , 2n−2). The C1represents the resonant capacitor (Cr=C1), while the Lrrepresents the resonant inductor. There are n (n=1, 2, 3, 4 . . . ) stages in the ladder RSCC with one base stage and n−1 extension stages. The base stage comprises two switches Q1, Q2and one inductor Lr, while each extension stage comprises two switches and two capacitors. There are overall 2n switches and 2n−2 capacitors, while the capacitor C2n-2in the last stage can be eliminated due to the clamped dc voltage VHV.

FIG.7shows an example of the circuit of a resonant two-switch boosting switched-capacitor converter (RTBSC). The switches in the positive leg and negative leg are QPiand QNi, correspondingly, (i=1, 2, 3, . . . , n). The switches QPiand QNican be either transistors or diodes. The capacitors in the positive leg and negative leg are CPjand CNj, respectively, (j=1, 2, 3, . . . , n−1). The combination of CP1and CN1, forms resonant capacitors.
Cr=CP1+CN1(1)

The resonant inductors in the RTBSC are L0, L1and L2. The resonant inductors L1is series connected to CP1and L2is series connected to CN1, respectively. In most applications, L1and L2can be zero.

Lr=L0+L1⁢L2L1+L2(2)
There are n (n=3, 5, 7, . . . ) stages in the RTBSC with one base stage and n−1 extension stages. The base stage comprises two switches QP1, QN1and the inductors L0, L1and L2, while each extension stage comprises two switches and two capacitors. There are overall n switches QPiin the positive leg and n switches QNiin the negative leg. There are overall n−1 capacitors CPiin the positive leg and n−1 capacitors CNiin the negative leg.

FIG.8shows an example of the circuit of a Dickson RSCC. The switches Q1(i=1, 2, 3, . . . , 2n) can be either transistors or diodes. The capacitors are Ci(i=1, 2, 3, . . . , 2n−2) and the inductors are Lk(k=0, 1, 3, 5, . . . , 2n−3) represents capacitors and inductors respectively.

Cr=C1+C3+…+C2⁢n-2(3)Lr=L0+11L1+1L3+…+1L2⁢n-3(4)
The inductance of L0can be minimized or zero when all of the rest inductors have non-zero inductance. Vice versa, the inductance of L0is non-zero when all of the rest inductors have minimized or zero inductance. There are n (n=2, 3, 4, . . . ) stages in the Dickson RSCC with one base stage and n−1 extension stages. The base stage comprises two switches Q1, Q2and one inductor L0, while each extension stage comprises two switches, two capacitors and one inductor. There are overall 2n switches and 2n−2 capacitors, while the capacitor C2n-2in the last stage can be eliminated due to the clamped dc voltage VHV.

FIG.9shows an example of the circuit of a series-parallel RSCC. The switches Qi(i=1, 2, 3, . . . , 3n−2) can be either transistors or diodes, while Ciand Li(i=1, 2, 3, . . . , n−1) represent capacitors and inductors respectively.
Cr=C1=C2= . . . =Cn-1(5)
Lr=L1=L2= . . . =Ln-1whenL0=0  (6)
Lr=L0whenL1=L2= . . . =Ln-1=0  (7)
The inductance of L0can be zero when all of the rest inductors have non-zero inductance. Vice versa, the inductance of L0is non-zero when all of the rest inductors have zero inductance. However, the resonant frequency in the charge process is different from the resonant frequency in the discharge process when the inductance of L0is non-zero. There are n (n=2, 3, 4, . . . ) stages in the series-parallel RSCC with one base stage and n−1 extension stages. The base stage comprises one inductor L0and one switch Q1, while each extension stage comprises three switches, one capacitor and one inductor. There are overall 3n−2 switches and n−1 capacitors.

FIG.10shows an example of the circuit of a Fibonacci RSCC. The switches QAi(i=1, 2, 3, . . . , n), QBj, and QCj(j=1, 2, 3, . . . , n−1) can be transistors or diodes, while Cjand Ljrepresents capacitors and inductors respectively.
Cr=C1=C2= . . . =Cn-1(8)
Lr=L1=L2= . . . =Ln-1(9)
There are n (n=2, 3, 4, . . . ) stages in the Fibonacci RSCC. Each stage comprises three switches, one capacitor and one inductor, while the last stage has only one switch QAn, There are overall 3n−2 switches and n−1 capacitors. The function of Fibonacci sequence is tabulated in table inFIG.11A.

InFIGS.6and8-10, all the circuits can be simplified into the basic RSCC as shown inFIG.4when n=2. InFIGS.4-10, the capacitors C and inductors L that series connected are resonant capacitors and resonant inductors. The table ofFIG.11Ashows the function of the Fibonacci sequence. The operation states for all the above mentioned RSCC circuits (FIGS.4-10) is defined in the table ofFIG.11B. The conducting switches are shown in the table for each of the operation states of the corresponding RSCC circuit. The other switches not given in the table ofFIG.11Bare non-conducting. The switches can be either transistors or diodes. When the switch Q is a transistor in the RSCC circuits, both positive and negative current flowing through the transistor can be regarded as conducting as shown in the table ofFIG.11B.

InFIG.11C, the table shows the switching sequences for the RSCC circuits shown inFIGS.4,5and8-10(to achieve full-range regulation) using the proposed switching methods A, B, C, D, E, F and G for step-down conversion. Methods A and B do not use the idle state, while methods C, D, E, F and G allow the idle state 5 with adjustable durations. Following the switching sequences of the above seven switching methods, the RSCCs inFIGS.4and8-10can achieve full-range regulation for all loads when stepping-down the voltage from VHVto VLV, while the RSCC inFIG.5can obtain inverse polarity step-down voltage conversion from V1to V2. The switching frequency is variable for switching methods A and B, while the switching frequency may be fixed or variable for switching methods C, D, E, F and G depending on the duration of idle state 5.

The table ofFIG.11Dshows the switching sequences for all the above mentioned RSCC circuits ofFIGS.4-10(to achieve full-range regulation) using the proposed switching methods H, I, J, K, L, M and N. There is no idle state 5 in methods H and I, while the duration of idle state 5 is adjustable in methods J, K, L, M and N. Following the switching sequences of these seven switching methods, RSCCs inFIGS.4and6-10can achieve step-up voltage conversion from VLVto VHV, while the RSCC inFIG.5can perform inverse polarity step-down voltage conversion from V2to V1. The switching frequency is variable for switching methods H and I, while the switching frequency can be fixed or variable for switching methods J, K, L, M and N depending on the duration of the idle state 5.

In the tables ofFIGS.11C and11D, the number 1, 2, 3, 4 and 5 represents the operation state 1, 2, 3, 4 and 5, respectively. Here, the symbols (1) or (3) represent that the freewheeling state 1 or freewheeling state 3 is eliminated or minimized. In addition, the symbol [5] represents that the duration of idle state 5 can be adjusted to vary the switching frequency. Moreover, one of the idle states may be eliminated for method G and N.

In order to display full-range regulation capability of RSCCs by proposed switching methods, the circuit parameters are defined as follows:
Frequency Ratio:

F=fsfr,where⁢fr=12⁢π⁢Lr⁢Cr(10)
Characteristic impedance:Zr=√{square root over (Lr/Cr)}  (11)
Quality Factor:

Q=ZrRL(12)
Where fsand frare switching frequency and resonant frequency. Lris the resonant inductance and Cris the resonant capacitance. and RLis the load resistance.

The inverse polarity step-down voltage conversion ratio M1for the RSCC inFIG.5is defined as:

M1=V2V1,when⁢V1⁢is⁢input⁢voltage,and(13)M1=V1V2,when⁢V2⁢is⁢input⁢voltage,(14)
where the range of M1is 0 to −1.

The step-down voltage conversion ratio M2for Dickson RSCCs, series-parallel RSCCs and Fibonacci RSCCs inFIGS.8-10is defined as:

M2=VLVVHV(15)
where the range of M2is 0 to the maximum voltage conversion ratio M2_max.

M2⁢_⁢max={1n1f⁡(n)Fibonacci⁢RSCCs(16)

The step-up voltage conversion ratio M3for ladder RSCCs, RTBSCs, Dickson RSCCs, series-parallel RSCCs and Fibonacci RSCCs inFIGS.6-10is defined as:

M3=VHVVLV(17)
where, the range of M3is 1 to the maximum voltage conversion ratio M3_max.

M3⁢_⁢max={nf⁡(n)Fibonacci⁢RSCCs(18)

FIG.12shows the voltage gain curves M1and M2for RSCCs inFIGS.4,5and8-10by switching methods A and B. Full-range voltage regulation of M1from 0 to −1 is achieved for inverse polarity RSCC inFIG.5regardless of load level. Full-range voltage regulation of M2from 0 to M2_maxis achieved for RSCCs inFIGS.4and8-10regardless of load level. Meanwhile,FIG.12shows the voltage gain curves M1and M3for RSCCs for all the above mentioned RSCC circuits by switching methods H and I. Full-range voltage regulation of M1from 0 to −1 is achieved for inverse polarity RSCC inFIG.5regardless of load level. Full-range voltage regulation of M3from 1 to M3_maxis achieved for RSCCs inFIGS.4and6-10regardless of load level.

For illustration purpose, three Q levels inFIG.12are listed representing three different loads, respectively, where Q is related to the load. In reality, Q level can be from 0 to infinity. According to equation (12), the greater Q represents the heavier load condition. As an example, the switching frequency is variable and the range of frequency ratio F is 1 to 2. The duty cycle D is adjusted according to the variation of frequency ratio F. Correspondingly, the full-range duty cycle adjustment can be achieved for all loads with D varied from 0 to 0.5.

FIG.13shows the voltage gain curves M1and M2for RSCCs inFIGS.4,5and8-10by switching methods C, D, E, F and G. Meanwhile,FIG.13shows the voltage gain curves M1and M3for RSCCs for all the above mentioned RSCC circuits by switching methods J, K, L, M and N. There are three Q levels inFIG.13for three different loads, respectively. According to equation (12), the greater Q represents the heavier load condition.

InFIG.13, the switching frequency is fixed at the resonant frequency (F=1) as an example. The proposed switching methods C, D, E, F, G, J, K, L, M and N allow RSCCs to operate above, equal and below the resonant frequency (F>1, F=1 and F<1) by adjusting the duration of idle state 5. As shown, the duty cycle is adjusted from 0 to 0.5 regardless of load level. Correspondingly, full-range voltage regulation can be achieved for all above mentioned RSCCs regardless of load level.

FIG.14shows the experiment result of a 3X ladder RSCC prototype using the proposed switching method H, when the RSCC operates at F=1.6 and D=0.2. The waveforms from top to bottom are the driving signal for switch Q1, input voltage, output voltage and the inductor current, respectively. As shown, the input voltage VLV=49.69V and the output voltage VHV=108.8V. The experimental voltage conversion ratio is 2.19 compared to the M3_max=3.

FIG.15shows the experiment result of a 3X ladder RSCC prototype by the proposed switching method J, when the RSCC operates at F=1, D=0.2. The waveforms from top to bottom are the driving signal for switch Q1, input voltage, output voltage and the inductor current. As shown, the input voltage VLV=49.65V and the output voltage VHV=120.2V. The experimental voltage conversion ratio is 2.42 compared to the M3_max=3.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 1, state 4 and state 3, where state 3 can be eliminated or minimized by the proposed switching method A. The conducting switches during the state 2, state 1, state 4 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 1, state 4 and state 3, where state 1 can be eliminated or minimized by the proposed switching method B. The conducting switches during the state 2, state 1, state 4 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 1, state 4 and state 5, where the duration of state 5 can be adjusted by the proposed switching method C. The conducting switches during the state 2, state 1, state 4 and state 5 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 5, state 4 and state 3, where the duration of state 5 can be adjusted by the proposed switching method D. The conducting switches during the state 2, state 5, state 4 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 1, state 5 and state 4, where the duration of state 5 can be adjusted by the proposed switching method E. The conducting switches during the state 2, state 1, state 5 and state 4 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 4, state 3 and state 5, where the duration of state 5 can be adjusted by the proposed switching method F. The conducting switches during the state 2, state 4, state 3 and state 5 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 2, state 1, state 5, state 4, state 3 and state 5, where the duration of state 5 can be adjusted by the proposed switching method G. In addition, one of the idle states 5 can be eliminated by the method G. The conducting switches during the state 2, state 1, state 5, state 4 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 1, state 2 and state 3, where state 3 can be eliminated or minimized by the proposed switching method H. The conducting switches during the state 4, state 1, state 2 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 1, state 2 and state 3, where state 1 can be eliminated or minimized by the proposed switching method I. The conducting switches during the state 4, state 1, state 2 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 1, state 2 and state 5, where the duration of state 5 can be adjusted by the proposed switching method J. The conducting switches during the state 4, state 1, state 2 and state 5 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 5, state 2 and state 3, where the duration of state 5 can be adjusted by the proposed switching method K. The conducting switches during the state 4, state 5, state 2 and state 3 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 1, state 5 and state 2, where the duration of state 5 can be adjusted by the proposed switching method L. The conducting switches during the state 4, state 1, state 5 and state 2 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 2, state 3 and state 5, where the duration of state 5 can be adjusted by the proposed switching method M. The conducting switches during the state 4, state 2, state 3 and state 5 are defined in the table ofFIG.11B.

In various aspects, a switching method to achieve full-range regulation for RSCCs can comprise a switching sequence where each switching cycle is formed by a switching sequence of state 4, state 1, state 5, state 2, state 3 and state 5, where the duration of state 5 can be adjusted by the proposed switching method N. In addition, one of the idle states 5 can be eliminated by the method N. The conducting switches during the state 4, state 1, state 5, state 2 and state 3 are defined in the table ofFIG.11B.

It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

The term “substantially” is meant to permit deviations from the descriptive term that don't negatively impact the intended purpose. Descriptive terms are implicitly understood to be modified by the word substantially, even if the term is not explicitly modified by the word substantially.

It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt % to about 5 wt %, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. The term “about” can include traditional rounding according to significant figures of numerical values. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about ‘y’”.