HYBRID DC-DC VARIABLE SWITCHED CAPACITOR CONVERTER AND METHOD OF OPERATION

Abstract

The present disclosure provides for a hybrid DC-DC, Hybrid Variable Switched Capacitor (HVSC) power converter. The converter may include one or more power switching networks supporting a plurality of power conversion modes and characterised in that: an input terminal connected to an input power source and an associated input capacitance, an output terminal connected to a load and an associated output capacitance to obtain a desired output voltage or output load current regulation; and at least six switches, one or more inductors and one or more flying capacitors. The converter addresses the problems faced by inductor-based and inductor-less DC-DC power converters while providing higher power conversion efficiencies alike the inductor-less switched capacitor converters and voltage/current regulation alike the inductor-based power converters in a single power conversion unit and enable a duty cycle-based output voltage/current regulation.

Claims

1. A hybrid variable switched capacitor DC-DC power converter, said converter comprising: at least one power switching network supporting a plurality of power conversion modes and characterised in that: an input terminal connected to an input power source and an associated input capacitor; an output terminal connected to a load and an associated output capacitor to obtain a desired output voltage or output load current regulation; at least six switches; at least one inductor; and one or more flying capacitor.

2. The converter as claimed in claim 1, wherein the at least one power switching network comprises: a first switch, a second switch, a third switch and a fourth switch of the at least six switches, wherein the first switch, the second switch, the third switch and the fourth switch are connected in series between the input terminal and ground; a fifth switch of the at least six switches configured in the at least one power switching network such that a first terminal of the fifth switch is connected to a shared node of the first switch and the second switch and a second terminal of the fifth switch is connected to a sixth switch of the at least six switches; the sixth switch is configured such that a first terminal of the sixth switch is connected to the fifth switch and a second terminal of the sixth switch is connected to the ground; the at least one inductor connected between a shared node of the fifth switch and the sixth switch and the output terminal; the one or more flying capacitors connected between a shared node of the first switch and the second switch and the shared node of the third switch and fourth switch.

3. The converter as claimed in claim 1, wherein the plurality of power conversion modes includes a Variable Switched Capacitor (VSC) Mode, 2:1 Halving Switched Capacitor (HSC) Mode, a Synchronous Buck Mode, and a Direct Connection Mode, wherein the converter is operated in any of a switching or non-switching mode to obtain a set of step-down power conversion schemes, wherein each power conversion scheme is selected for a predefined range of step-down ratios to maximize efficiency of power conversion, and wherein each power conversion scheme is selected at a time based on a load type and input power source type.

4. The converter as claimed in claim 3, wherein a first power switching network of the at least one power switching network for enabling the VSC Mode for power conversion is configured for the desired output voltage that is less than half of input voltage level, wherein the VSC Mode comprises at least two switching phases, and total time of the two switching phases equal to switching time-period.

5. The converter as claimed in claim 4, wherein the at least two switching phases comprises a first switching phase for a first predefined first time duration, wherein the first switch and the third switch of the first power switching network are turned on to charge the one or more flying capacitor in series with the output load from the input power source and wherein, the sixth switch of the first power switching network is turned on to allow the at least one inductor to transfer the stored energy to the load.

6. The converter as claimed in claim 5, wherein the at least two switching phases comprises a second switching phase for a second predefined second time duration, wherein the fourth and the fifth switches of the first power switching network are turned on to transfer the energy stored in the one or more flying capacitor in the first switching phase to be transferred to the at least one inductor and the load, wherein a small dead time is introduced between the two switching phases between turning off a set of switches and turning on of another set of switches, wherein the second switch is turned off for an entire operation, and wherein a ratio of the desired output voltage to the input voltage level can be represented as a ratio of a second switching phase time to a sum of total switching time and the second switching phase time.

7. The converter as claimed in claim 2, wherein a first power switching network of the at least one power switching network for enabling the 2:1 HSC Mode for power conversion is configured for the desired output voltage to be equal to half of input voltage level and an output current is approximately double of an input current, wherein, in a first switching phase for a predefined first time duration, the first and the third switches are turned on to charge the one or more flying capacitor in series with output load, wherein, in a second switching phase for a predefined second time duration, the second and the fourth switches are turned on to transfer energy stored in the one or more flying capacitor to the load, and wherein the fifth and the sixth switches are turned off for an entire operation.

8. The converter as claimed in claim 2, wherein a first power switching network of the at least one power switching network for enabling the Synchronous Buck Mode for power conversion is configured for a desired output voltage that is greater than half of input voltage level, wherein the first switch is turned on for an entire operation, wherein, in a first switching phase for a predefined first time duration, the fifth switch is turned on to charge the at least one inductor in series with output load, wherein, in a second switching phase for a predefined second time duration, the sixth switch is turned on to transfer energy stored in the at least one inductor to the load, and wherein the second, the third and the fourth switches are turned off for the entire operation.

9. The converter as claimed in claim 4, wherein a second power switching network of the at least one power switching network for enabling the Direct Connection Mode for power conversion is configured for a desired output voltage that is equal to the input voltage level, wherein an output current is equal to an input current, wherein the first and the second switches are turned on for an entire operation to directly connect the input power source to the load, and wherein the third, the fourth, the fifth and the sixth switches are turned off for the entire operation.

10. A method of operation of the converter as claimed in claim 1, said method working in the Variable Switched Capacitor mode, said method comprising: operating the converter in at least two switching phases, wherein total time of the at least two switching phases equal to a switching time-period, wherein, in a first switching phase, the first and the third switches are turned on to charge the one or more flying capacitor in series with the output load from the input power source and the sixth switch is turned on to allow the at least one inductor to transfer a stored energy in the at least one inductor to the load, wherein, in a second switching phase, the fourth and the fifth switches are turned on to transfer a stored energy in the one or more flying capacitor to the at least one inductor and the load, wherein a small dead time is introduced between the at least two switching phases between turning off a first set of switches and turning on of a second set of switches, wherein the second switch is turned off for an entire operation, and wherein a ratio of the desired output voltage to an input voltage is represented as a ratio of a second switching phase time to a sum of total switching time and the second switching phase time.

11. The method as claimed in claim 10, said method working in the Direct Connection mode, said method comprising: turning on the first and the second switches for the entire operation to directly connect the input power source to the load; and turning off the third, the fourth, the fifth and the sixth switches for the entire operation, wherein the desired output voltage is same as the input voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0036] FIG. 1 illustrates an exemplary schematic diagram of the proposed hybrid power converter, in accordance with an embodiment of the present disclosure.

[0037] FIG. 2 illustrates an exemplary schematic diagram of the proposed hybrid power converter in a Variable Switched Capacitor (VSC) Mode, in accordance with an embodiment of the present disclosure.

[0038] FIG. 3 illustrates an exemplary schematic diagram of the proposed hybrid power converter in 2:1 Halving Switched Capacitor (HSC) Mode, in accordance with an embodiment of the present disclosure.

[0039] FIG. 4 illustrates an exemplary schematic diagram of the proposed hybrid power converter in a Synchronous Buck Mode, in accordance with an embodiment of the present disclosure.

[0040] FIG. 5 illustrates an exemplary schematic diagram of the proposed hybrid power converter in a Direct Connection Mode, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0041] The present disclosure relates to a power converter, and, in particular embodiments, to a bi-directional hybrid variable switched capacitor power converter for step-down power conversion operations and the like.

[0042] The present disclosure relates to a Hybrid, DC-DC, Variable, Switched Capacitor (HVSC) Converter. More particularly, it relates to a converter that addresses the problems faced by inductor-based and inductor-less DC-DC power converters while providing higher power conversion efficiencies alike the inductor-less switched capacitor converters and voltage/current regulation alike the inductor-based power converters in a single power conversion unit. The proposed converter incorporates one or more inductors and flying capacitor to enable a duty cycle-based output voltage/current regulation.

[0043] FIG. 1 illustrates an exemplary schematic diagram of the proposed hybrid power converter, in accordance with an embodiment of the present disclosure.

[0044] As illustrated, in an aspect a hybrid power converter 100 (also referred to as a DC-DC Hybrid Variable Switched Capacitor Converter 100 (HVSC 100)) is provided that may include an input circuit that may include an input power supply (120), one or more input capacitors (124), and plurality of switches (101-106) (interchangeably referred to as M1, M2 . . . M6 respectively herein) connected across the input power supply (120).

[0045] In an embodiment, the switches can be physically implemented as power MOSFETs. The output circuit consists of an output terminal connected to a load (134) and an associated output capacitance (132). The power converter network comprises an inductor (128) and one or more flying capacitors (CFLY) (126).

[0046] In an embodiment, a first (101), a second (102), a third (103) and a fourth switch (104) may be connected in series between the input terminal and the ground. A fifth switch (105) may be configured in the switching network such that a first terminal of the fifth switch (105) is connected to a shared node of the first switch (101) and the second switch (102) and a second terminal of the fifth switch (105) is connected to a sixth switch (106). The sixth switch (106) may be configured such that a first terminal of the sixth switch (106) may be connected to the fifth switch (105) and a second terminal of the sixth switch (106) may be connected to the ground.

[0047] In an embodiment, the inductor may be connected between the shared node of the fifth switch (105) and sixth switch (106) and the output terminal, and the one or more flying capacitors (126) may be connected between the shared node of the first switch (101) and the second switch (102) and the shared node of the third (103) and the fourth switch (104).

[0048] In an aspect, the HVSC converter may support at least four power conversion modes such as a Variable Switched Capacitor (VSC) Mode, 2:1 Halving Switched Capacitor (HSC) Mode, Synchronous Buck Mode, Direct Connection Mode and the like. The VSC mode may further include at least two phases such as a Switching Phase 1 for first predefined time duration T1, a Switching Phase 2 for a second predefined time duration T2 and the like.

[0049] FIG. 2 illustrates an exemplary schematic diagram of the proposed hybrid power converter in Variable Switched Capacitor (VSC) Mode, in accordance with an embodiment of the present disclosure. As illustrated, the power converter operation in VSC mode may require the switches 101, 103, 104, 105, and 106 to be switching between ON and OFF states across the two switching phases and the switch 102 to be always off.

[0050] In an embodiment, in the Variable Switched Capacitor (VSC) Mode for power conversion, the desired output voltage is less than half of the input voltage level (VOUT<½ VIN, or, in other words, a duty cycle of <50%). The VSC mode may be composed of at least two phases: a first Switching Phase (interchangeably referred to as the Switching Phase 1) for the first predefined time duration T1 where the switches 101 and 103 may be turned on to charge flying capacitor C.sub.FLY (126) in series with the output load and switch 106 may also be turned on to allow inductor to transfer the stored energy to the load. Below equations represent the state of the flying capacitor C.sub.FLY (126) and the inductor L (128) during switching cycle 1:

VIN−VFLY=VOUT; 0−VOUT=LΔI1/T1

[0051] In an embodiment, in the second Switching Phase (interchangeably referred to as the Switching Phase 2) for the second predefined time duration T2 may include the switches 104 and 105 to be turned on to transfer the energy stored in flying capacitor C.sub.FLY (126) in phase 1 to the inductor and the load. Below equations represent the state of the flying capacitor C.sub.FLY and the inductor L during switching phase 2:

VFLY−VOUT=LΔI2/T2.

[0052] Assume T1+T2=T, the total switching time-period of both the switching phases. The decrease in inductor current −ΔI1 in switching phase 1 should be the same as increase in inductor current −ΔI2 in switching phase 2, hence:

−ΔI1=ΔI2,VOUT×T1/L=(VFLY−VOUT)×T2/L,

Substituting VFLY=VIN−VOUT from the equation for switching phase 1,

VOUT×T1=(VIN−2×VOUT)×T2,

VOUT=VIN×T2/(T1+2T2),

VOUT=VIN/(2+T1/T2)=VIN×D

[0053] In an embodiment, the switching cycles times T1 and T2 may be adjusted to obtain the various values for the ratio T1/T2 as per the VOUT voltage equation above, hence obtaining the various levels of output voltage V.sub.OUT (130). It can be noted that since the denominator 2+T1/T2 is always greater than 2, for any given input voltage V.sub.IN (122), an output voltage V.sub.OUT (130) less than V.sub.IN/2 can only be obtained, effectively giving a duty cycle, D, less than 50% for all values of the switching phase time durations, T1 and T2.

[0054] FIG. 3 illustrates an exemplary schematic diagram of the proposed hybrid power converter in 2:1 Halving Switched Capacitor (HSC) Mode, in accordance with an embodiment of the present disclosure. As illustrated, the power converter in HSC mode may include the switches 101, 102, 103, and 104 to be switching between ON and OFF states across the two switching phases and switches 105 and 106 to be always off.

[0055] In an embodiment, in the 2:1 Halving Switched Capacitor (HSC) Mode for power conversion, the desired output voltage is equal to half of the input voltage level This implies V.sub.OUT=½ V.sub.IN, or, in other words, a duty cycle of 50%. The HSC mode operates in open loop, that is, the duty cycle is not regulated via a feedback and may be composed of two phases, timing of each phase being equal:

[0056] Switching Phase 1 (for time duration T): The switches 101 and 103 (M1 and M3) are turned on to charge the flying capacitor C.sub.FLY (126) in series with the load (134). Below equations represent the state of the flying capacitor C.sub.FLY during switching phase 1:

V.sub.IN−V.sub.FLY=V.sub.OUT

[0057] Switching Phase 2 (for time duration T): The switches 102 and 104 (M2 and M4) are turned on to transfer the energy stored in the flying capacitor C.sub.FLY (126) to the load (134). Below equations represent the state of the flying capacitor C.sub.FLY (126) during switching phase 2:

V.sub.FLY−V.sub.OUT=0

[0058] Assuming, T+T=2T, the total switching time-period of both the switching phases and substituting V.sub.FLY=V.sub.OUT from the equation of switching phase 2 to the equation of switching phase 1,

V.sub.IN−V.sub.OUT=V.sub.OUT

V.sub.OUT=V.sub.IN/2

[0059] FIG. 4 illustrates an exemplary schematic diagram of the proposed hybrid power converter in Synchronous Buck Mode, in accordance with an embodiment of the present disclosure. As illustrated, the power converter in the Synchronous Buck Mode may include the switch 101 to be always on, switches 105 and 106 to be switching between ON and OFF states across the two switching phases and switches 102, 103 and 104 to be always off

[0060] In an embodiment, a Synchronous Buck Mode may be used for power conversion where the desired output voltage is greater than half of the input voltage level. This implies V.sub.OUT>½ V.sub.IN and V.sub.OUT<V.sub.IN, or, in other words, a duty cycle greater than 50%. The Synchronous Buck mode operates in the standard two phases.

[0061] Switching Phase 1 (for time duration T.sub.1): Switch 105 (M5) is turned on to charge inductor in series with output load. Below equations represent the state of the inductor L during switching phase 1:

V.sub.IN−V.sub.OUT=LΔI.sub.1/T.sub.1

[0062] Switching Phase 2 (for time duration T.sub.1): Switch 106 (M6) is turned on to transfer the energy stored in the inductor to the load. Below equations represent the state of the inductor L during switching phase 2:

V.sub.OUT=LΔI.sub.2/T.sub.2.

[0063] Assume T1+T2=T, the total switching time-period of both the switching phases. The decrease in inductor current −ΔI.sub.1 in switching phase 1 should be the same as increase in inductor current ΔI.sub.2 in switching phase 2, hence:

−ΔI.sub.1=ΔI.sub.2

(V.sub.IN−V.sub.OUT)×T.sub.1/L=(0−V.sub.OUT)×T.sub.2/L

V.sub.OUT=V.sub.IN×T.sub.1/(T.sub.1+T.sub.2)=V.sub.IN×D

The switching cycles times T.sub.1 and T.sub.2 are adjusted to obtain the various values for the duty cycle ratio, D=T.sub.1/(T.sub.1+T.sub.2), hence obtaining the various levels of output voltage VOUT, as per the voltage equation above.

[0064] FIG. 5 illustrates an exemplary schematic diagram of the proposed hybrid power converter in Direct connection Mode, in accordance with an embodiment of the present disclosure. As illustrated, the power converter in the Direct Connection Mode may include the switches 101 and 102 to be always on and switches 103, 104, 105 and 106 to be always off

[0065] In an embodiment, the Direct Connection Mode may be used for power conversion where the desired output voltage is equal to the input voltage level. This implies V.sub.OUT=V.sub.IN, or, in other words, a duty cycle of 100%. For Direct Connection mode, the switches 101 and 102 (M1 and M2) may be turned on continuously to directly connect the output terminal to the input voltage.

[0066] The proposed DC-DC Hybrid Variable Switched Capacitor Converter (HVSC) addresses the problems faced by inductor-based and inductor-less DC-DC power converters, by providing a higher power conversion efficiency like the inductor-less switched capacitor converters, and voltage/current regulation like the inductor-based power converters in a single power conversion unit. HVSC converter uses inductor as well as flying capacitor in the switching topology, enabling a duty cycle-based output voltage/current regulation. [0067] Compared to inductor-based converters, HVSC converter enables VSC power conversion mode with a switching scheme that does not lead to entire load current flowing through the inductor, hence providing higher efficiency. Lower switching losses also improve the efficiency compared to standard inductor-based converters. Though VSC Mode provides power conversion with duty cycles less than 50% only (output voltage less than half of input voltage), the VSC Mode is optimized to work with greater efficiency at higher input voltages for the same output voltage and higher output load current, the desired DC-DC conversion for applications such as fast battery charging. In case duty cycle more than 50% is desired, the HVSC can work as a standard inductor-based buck converter as well. [0068] Compared to inductor-less switched capacitor converters, HVSC converter provides a very small drop in efficiency, by adding the voltage/current regulation feature which is not feasible with open-loop switched capacitor converters. In addition, the HVSC converter topology also supports the open-loop standard 2:1 switched capacitor converter, thus not losing behind the high 2:1 direct conversion efficiency of switched capacitor conversion. [0069] Compared to multiple power converters present as standalone units in present day portable device systems, HVSC converter provides a single power conversion unit, while enabling the desired higher efficiency and voltage/current regulation features. Thus, the HVSC converter reduces the overall cost and PCB footprint of the power conversion system. [0070] Compatibility to all varieties of input supplies, HVSC power conversion can be targeted for a varieties of input supplies, including the latest power supplies available for fast charging technologies. HVSC supports various power conversion modes, any one of which can be selected based on the type of input supply. For example, consider the case of charging a 1s battery in a smartphone from a power adapter that may support USB Power Delivery charging protocol:

TABLE-US-00001 HVSC Operation Mode (For charging Power Adapter Type/Features 1 S battery) 5 V Legacy (Type-C/Type-A) Synchronous Buck USB Power Delivery (5 V/9 V Fixed Supplies) Synchronous Buck USB Power Delivery (15 V/20 V Fixed Supplies) Variable Switched Capacitor USB Power Delivery (5 V Programmable Power Direct Connection Supply) USB Power Delivery (9 V Programmable Power 2:1 Halving Switched Supply) Capacitor USB Power Delivery (20 V Programmable Power Variable Switched Supply) Capacitor USB Power Delivery (28 V Extended Power Variable Switched Range Fixed Supply) Capacitor

[0071] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

Advantages of the Present Disclosure

[0072] The present disclosure provides for a DC-DC Hybrid Variable Switched Capacitor Converter (HVSC) that provides a higher power conversion efficiency like the inductor-less switched capacitor converters, and voltage/current regulation like the inductor-based power converters in a single power conversion unit.

[0073] The present disclosure provides for a DC-DC HVSC converter that uses inductor as well as flying capacitor in the switching topology, enabling a duty cycle-based output voltage/current regulation.

[0074] The present disclosure provides for a DC-DC HVSC converter that enables power conversion with a switching scheme that does not lead to entire load current flowing through the inductor, hence providing higher efficiency.

[0075] The present disclosure provides for a DC-DC HVSC converter that enables lower switching losses to improve the efficiency compared to standard inductor-based converters.

[0076] The present disclosure provides for a DC-DC HVSC converter HVSC converter that is optimized to work with greater efficiency at higher input voltages for the same output voltage and higher output load current, the desired DC-DC conversion for applications such as fast battery charging. In case duty cycle more than 50% is desired, the HVSC can work as a standard inductor-based buck converter as well.

[0077] The present disclosure provides for a DC-DC HVSC converter that contributes a very small drop in efficiency, by adding the voltage/current regulation feature which is not feasible with open-loop switched capacitor converters.

[0078] The present disclosure provides for a DC-DC HVSC converter that supports the open-loop standard 2:1 switched capacitor converter, thus not losing behind the high 2:1 direct conversion efficiency of switched capacitor conversion.

[0079] The present disclosure provides for a DC-DC HVSC converter that can present as standalone units in present day portable device systems, HVSC converter provides a single power conversion unit, while enabling the desired higher efficiency and voltage/current regulation features.

[0080] The present disclosure provides for a DC-DC HVSC converter that reduces the overall cost and PCB footprint of the power conversion system.