Patent Publication Number: US-2023146408-A1

Title: Direct current-to-direct current conversion system

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to converting power required by electronic systems from one voltage level to another. In particular, the present disclosure relates to a dual function direct current (DC)-to-DC switched capacitor conversion systems having two separate voltage outputs. 
     BACKGROUND 
     The amount of time a cellular handset can operate on a fully charged battery conflicts with the increasing consumer demand for more features and smaller handsets. To keep up with the power requirements brought about by these consumer demands, the cellular handset industry has turned to advanced higher capacity battery technology. However, a trade-off exists in that an advanced battery can be discharged to a lower operating voltage than typical batteries. The lower operating voltage is incompatible with existing power amplifier (PA) technology that is used in some of the basic building blocks of cellular handset circuitry. To solve this lower voltage incompatibility issue, the cellular handset industry has turned to direct current (DC)-to-DC conversion technology to boost the voltage of advanced batteries to a level that is compatible with existing PA technology. Moreover, it is widely recognized that DC-DC conversion technology is generally much more efficient at regulating output voltage than typical linear voltage regulator technology. Thus, DC-DC conversion technology offers increased efficiency that can provide longer handset operation time or smaller handsets while stepping up the voltage for compatibility with existing PA technology. However, traditional DC-DC conversion technology employed in dual function DC-DC conversion systems with two separate voltage outputs have relatively high component counts. Therefore, there is a need reduce component count in dual function DC-DC conversion systems. 
     SUMMARY 
     A direct current-to-direct current conversion system is disclosed having a switch network configured to respond to control signals to selectably couple a first capacitor and a second capacitor between an input, a first output, and a second output. Also included is a switch controller configured to signal the switch network to couple the first capacitor and the second capacitor in series between the first output and a fixed voltage node and signal the switch network to couple the first capacitor and the second capacitor in series between the first output and the input. The switch controller is further configured to signal the switch network to couple the first capacitor and the second capacitor in parallel between the first output and the second output and signal the switch network to couple the first capacitor and the second capacitor between the second output and the fixed voltage node. 
     In another aspect, any of the foregoing aspects individually or together, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein. 
     Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG.  1    depicts a related-art dual function direct current-to-direct current (DC-DC) conversion system that has two series coupled switched capacitor DC-DC converters that each have a pair of flying capacitors. 
         FIG.  2    depicts an exemplary embodiment of a dual function DC-DC conversion system that in accordance with the present disclosure reduces the number of flying capacitors while providing the same function as the related-art dual function conversion system depicted in  FIG.  1   . 
         FIG.  3    depicts an exemplary embodiment of a switch network and controller that can comprise the exemplary embodiment dual function DC-DC conversion system depicted in  FIG.  2   . 
         FIG.  4    is a switching phase diagram showing a first phase, a second phase, a third phase, and a fourth phase for the switch network depicted in  FIG.  3   . 
         FIG.  5    is a diagram depicting the coupling of flying capacitors with the switching network in the first phase. 
         FIG.  6    is a diagram depicting the coupling of the flying capacitors with the switching network in the second phase. 
         FIG.  7    is a diagram depicting the coupling of the flying capacitors with the switching network in the third phase. 
         FIG.  8    is a diagram depicting the coupling of the flying capacitors with the switching network in the fourth phase. 
         FIG.  9    is a diagram of an exemplary embodiment of the DC-DC conversion system that includes loop control elements. 
         FIG.  10    is a diagram of an exemplary embodiment of the DC-DC conversion system that provides a multilevel buck function. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description considering the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Embodiments are described herein with reference to schematic illustrations of embodiments of the disclosure. As such, the actual dimensions of the layers and elements can be different, and variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are expected. For example, a region illustrated or described as square or rectangular can have rounded or curved features, and regions shown as straight lines may have some irregularity. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the disclosure. Additionally, sizes of structures or regions may be exaggerated relative to other structures or regions for illustrative purposes and, thus, are provided to illustrate the general structures of the present subject matter and may or may not be drawn to scale. Common elements between figures may be shown herein with common element numbers and may not be subsequently re-described. 
       FIG.  1    depicts a related-art DC-DC conversion system  10  that has a first switched capacitor DC-DC converter  12  and a second switched capacitor DC-DC converter  14  that are coupled in series. The first switched capacitor DC-DC converter  12  receives an input voltage VIN and is configured to alternately charge and discharge both a first flying capacitor C 1  and a second flying capacitor C 2  to output a first output voltage VOUT 1 . The second DC-DC converter  14  receives the first output voltage VOUT 1  and is configured to alternately charge and discharge both a third flying capacitor C 3  and a fourth flying capacitor C 4  to output a second output voltage VOUT 2 . The first switched capacitor DC-DC converter  12  performs a function of a battery fast charging circuit that, for example, takes the input VIN of ˜20 V and downconverts VIN to VOUT 1  10 V to charge a stacked two-cell lithium-ion battery depicted as VBAT 1  and VBAT 2 . The first switched capacitor DC-DC converter  12  is based on operating with a ratio of 2:1, that is, VOUT 1 =½*VIN. The second switched capacitor DC-DC converter  14  performs a DC-DC conversion to downconvert the voltage VOUT 1  of the stacked two-cell lithium-ion battery VBAT 1  and VBAT 2  from 10 V to 5 V to supply the electronic circuitry of, for example, a mobile phone. 
       FIG.  2    depicts an exemplary embodiment of a DC-DC conversion system  16  that in accordance with the present disclosure reduces the number of flying capacitors to C 1  and C 2  and provides the first output voltage VOUT 1  and the second output voltage VOUT 2 . The DC-DC conversion system  16  generates simultaneously VOUT 1 =½ VIN and VOUT 2 =¼*VIN and re-uses the same flying capacitors C 1  and C 2 , where four phases are used to simultaneously generate both outputs VOUT 1  and VOUT 2 . The DC-DC conversion system  16  has a first DC-DC converter section  18  that is configured to provide a first function that converts the input voltage VIN from either a wireless receiver charger and/or from a USB type C charger such as a 20 V or higher charger to the first voltage VOUT 1  that is usable, for example, to charge a stacked two-cell lithium-ion battery VBAT 1  and VBAT 2  to 10 V. The DC-DC conversion system  16  has a second DC-DC converter section  20  that is configured to simultaneously provide a second function that performs a DC-DC buck conversion to generate the output voltage VOUT 2  of 5 V that is usable, for example, to supply mobile phone electronics and other power management circuitries. At least one advantage of the DC-DC conversion system  16  is a smaller volumetric size than the related-art DC-DC conversion  10  ( FIG.  1   ) due to a reduction of in number of switching elements by retaining only the first flying capacitor C 1  and the second flying capacitor C 2 . In other words, the DC-DC conversion system  16  eliminates the third flying capacitor C 3  and the fourth flying capacitor C 4 , which in turn eliminates associated switching elements and control complexity of the associated switching elements. 
       FIG.  3    depicts an exemplary embodiment of a switch network  22  and a switch controller  24  that can comprise the exemplary embodiment of the DC-DC conversion system  16  depicted in  FIG.  2   . The switch network  22  has a first switch S 1  coupled between an input IN 1  and a first node N 1 , and a second switch S 2  coupled between a fixed voltage node, such as GND and a second node N 2 . The switch network  22  also includes a third switch S 3  coupled between the fixed voltage node GND and a third node N 3  and a fourth switch S 4  coupled between the second node N 2  and the third node N 3 . A fifth switch S 5  is coupled between the second node N 2  and a fourth node N 4 , and a sixth switch S 6  is coupled between the first node N 1  and a fifth node N 5 . A seventh switch S 7  is coupled between the fourth node N 4  and the fifth node N 5 , and an eighth switch S 8  is coupled between the third node N 3  and a first output OUT 1 . A ninth switch S 9  is coupled between the fifth node N 5  and the first output OUT 1 , and a tenth switch S 10  is coupled between the fifth node N 5  and a second output OUT 2 . The switches S 1 -S 10  are electronic switches and may be field-effect transistors. 
     An exemplary embodiment of the switch controller  24  is configured to generate switch control signals that drive the switches S 1 -S 10  between a conductive state ON and a non-conductive state OFF. In the exemplary embodiment, a first switch control signal O 1  drives the first switch S 1 , while a second switch control signal O 2  drives the second switch S 2 , and a third control signal O 3  drives the third switch S 3 . A fourth switch control signal O 4  drives the fourth switch S 4 , a fifth switch control signal O 5  drives the fifth switch S 5 , and a sixth control signal O 6  drives the sixth switch S 6 . A seventh switch control signal O 7  drives the seventh switch S 7 , and an eighth switch control signal O 8  drives the eighth switch S 8 . A ninth switch control signal O 9  drives the ninth switch S 9 , and a tenth control signal O 10  drives the tenth switch S 10 . It is to be understood that ten control lines carrying the ten switch control signals may be replaced by one control line if each of the switches S 1 -S 10  has address decoder logic and that each of the switch control signals O 1 -O 10  are transmitted serially with an individual logic address value for each one of switches S 1 -S 10 . 
       FIG.  4    is a switching phase diagram showing a first phase, a second phase, a third phase, and a fourth phase for the switch network  22  depicted in  FIG.  3   . The switch controller  24  is configured to drive each of the switches S 1 -S 10  between the conductive state ON and the non-conductive state OFF for each of the first phase, the second phase, the third phase, and the fourth phase. 
       FIG.  5    is a diagram depicting the coupling of the first flying capacitor C 1  and the second flying capacitor C 2  with the switch network  22  in the first phase. In the first phase, the first flying capacitor C 1  and the second flying capacitor C 2  are coupled in series between the fixed voltage node GND and the first output voltage OUT 1 . 
       FIG.  6    is a diagram depicting the coupling of the first flying capacitor C 1  and the second flying capacitor C 2  with the switch network  22  in the second phase. In the second phase, the first flying capacitor C 1  and the second flying capacitor C 2  are coupled in series between the input voltage VIN and the first output voltage OUT 1 . 
       FIG.  7    is a diagram depicting the coupling of the first flying capacitor C 1  and the second flying capacitor C 2  with the switch network  22  in the third phase. In the third phase, the first flying capacitor C 1  and the second flying capacitor C 2  are coupled in parallel between the first output voltage OUT 1  and the second output voltage VOUT 2 . 
       FIG.  8    is a diagram depicting the coupling of the first flying capacitor C 1  and the second flying capacitor C 2  with the switch network  22  in the fourth phase. In the fourth phase, the first flying capacitor C 1  and the second flying capacitor C 2  are coupled in parallel between the fixed voltage node GND and the second output OUT 2 . 
       FIG.  9    is a diagram of an exemplary embodiment of the DC-DC conversion system  16  that includes loop control elements  26 . In this exemplary embodiment, a first loop controller  28  is configured to adjust a voltage level of an input voltage at the input voltage VIN to achieve a desired output voltage level of a first output voltage at the first voltage output OUT 1 . A second loop controller  30  is configured to adjust a voltage level of an input voltage at the input voltage VIN to achieve a desired output voltage level of a second output voltage at the second voltage output OUT 2 . A multiplexer  32  is configured to combine adjusting signals from the first loop controller  28  into a common adjusting signal. 
     Operation of the DC-DC conversion system  16  is substantially efficient, given that the input voltage VIN is normally adjusted to keep a VIN/VOUT 1  or VIN/VOUT 2  ratio constant. The loop control elements  26  that adjust the input voltage VIN are used to maintain the VIN/VOUT 1  ratio and/or the VIN/VOUT 2  ratio constant. This is required given, for example, that the stacked two-cell lithium-ion battery VBAT 1  and VBAT 2  voltage can be discharged to, for example, 2*3 V=6 V. Thus, the input voltage Vin is adjusted to 2:1*6 V=12 V instead of 20 V. The loop control elements  26  can be either set relative to voltage at the first output voltage VOUT 1  or can be set relative to the second output voltage VOUT 2 , depending on the application requirements, as shown in the embodiment of  FIG.  9   . 
     The embodiment in accordance with the present disclosure can be generalized to other switch capacitor ratios such that a single switch capacitor with multiple outputs of different ratios such as {x, 2x, 1−x, 1} for buck, and {1+x, 2−x, 2} for boost is possible, with x being the programmed ratio x=VOUT/VIN. 
     The exemplary embodiments in accordance with the present disclosure also can be generalized such that the second output voltage VOUT 2  can be based on a buck inductor-based converter function in which an LX node is driven by multi-level inputs such as VOUT 1 A and VOUT 1  B, for example, and generates multiple outputs, one for a battery fast charger for VBAT 1  and VBAT 2  and one for the LX level, as shown in  FIG.  10   . An inductor L 1  is coupled between the second voltage output OUT 2  (i.e., the LX node) and a third capacitor C 3  coupled to the fixed voltage node. 
     It is contemplated that any of the foregoing aspects, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various embodiments as disclosed herein may be combined with one or more other disclosed embodiments unless indicated to the contrary herein. 
     Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.