PATENT DOCUMENT

Publication Number: US-11888406-B2
Application Number: US-202117457379-A
Country: US
Kind Code: B2

Title: Hybrid charger and inverter system

Abstract:
An AC-AC converter can include a stack of four switches. An input of the converter can be coupled across the stack of four switches, and an output of the converter can be taken from first terminal coupled to a connection point of first and second switches of the stack and a second terminal coupled to a connection point of third and fourth switches of the stack. The converter can further include a controller that operates the switches such that during a positive half cycle of an AC input voltage, the first and second switches are operated with an alternating 50% duty cycle and the third and fourth switches are constantly on, and during the negative half cycle of the AC input voltage, the third and fourth switches are operated with an alternating 50% duty cycle and the first and second switches are constantly on.

Claims:
The invention claimed is: 
     
       1. An AC-AC converter comprising:
 a stack of four switching devices, wherein an input of the AC-AC converter is coupled across the stack of four switching devices and an output of the AC-AC converter is taken from first terminal coupled to a connection point of first and second switching devices of the stack and a second terminal coupled to a connection point of third and fourth switching devices of the stack; and 
 a controller that operates the switching devices such that:
 during a positive half cycle of an AC input voltage, first and second switching devices of the stack are operated with an alternating 50% duty cycle and third and fourth switching devices of the stack are constantly on; and 
 during the negative half cycle of the AC input voltage, the third and fourth switching devices of the stack are operated with an alternating 50% duty cycle and the first and second switching devices of the stack are constantly on; 
 
 wherein:
 during the positive half cycle, the duration of the on-times of the first and second switching devices determine the magnitude of the AC voltage between the first and second terminals; and 
 during the negative half cycle, the duration of the on times of the third and fourth switching devices determine the magnitude of the AC voltage between the first and second terminals. 
 
 
     
     
       2. The AC-AC converter of  claim 1  further comprising first and second series-connected input capacitors coupled across the input of the AC-AC converter, with a connection point of the series-connected input capacitors coupled to a connection point of the second and third switching devices. 
     
     
       3. The AC-AC converter of  claim 1  further comprising at least one output filter inductor and at least one output filter capacitor coupled to the output of the AC-AC converter. 
     
     
       4. The AC-AC converter of  claim 3  wherein the at least one filter inductor comprises a first filter inductor coupled between the first terminal and a load. 
     
     
       5. The AC-AC converter of  claim 4  wherein the at least one filter inductor comprises a second inductor coupled between the second terminal and the load. 
     
     
       6. The AC-AC converter of  claim 1  further comprising a resonant tank made up of at least one resonant capacitor and at least one resonant inductor, wherein the resonant tank facilitates zero voltage switching of the switching devices. 
     
     
       7. The AC-AC converter of  claim 6  wherein the resonant tank is a series resonant circuit coupled between the first terminal and the second terminal. 
     
     
       8. The AC-AC converter of  claim 6  wherein the resonant tank is a series resonant circuit coupled in parallel with the at least one output filter inductor. 
     
     
       9. A method performed by a controller of an AC-AC converter having a stack of four switching devices, wherein an input of the AC-AC converter is coupled across the stack of four switching devices and an output of the AC-AC converter is taken from first terminal coupled to a connection point of first and second switching devices of the stack and a second terminal coupled to a connection point of third and fourth switching devices of the stack, the method comprising:
 during a positive half cycle of an AC input voltage:
 operating first and second switching devices of the stack with an alternating 50% duty cycle; and 
 turning on and leaving on third and fourth switching devices of the stack; and 
 
 during a negative half cycle of the AC input voltage:
 operating the third and fourth switching devices of the stack with an alternating 50% duty cycle; and 
 turning on and leaving on the first and second switching devices of the stack; 
 
 wherein:
 during the positive half cycle, the duration of the on-times of the first and second switching devices determine the magnitude of the AC voltage between the first and second terminals; and 
 during the negative half cycle, the duration of the on times of the third and fourth switching devices determine the magnitude of the AC voltage between the first and second terminals. 
 
 
     
     
       10. The method of  claim 9  wherein the switching devices are operated with zero voltage switching.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 63/261,544, filed Sep. 23, 2021, entitled “Hybrid Charger and Inverter System”, and U.S. Provisional Application No. 63/261,545, filed Sep. 23, 2021, entitled “Hybrid Charger and Inverter System,” and U.S. Provisional Application No. 63/261,548, filed Sep. 23, 2021, entitled “Hybrid Charger and Inverter System,” the disclosures of which are incorporated by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     In many applications it may be desirable to provide one or more alternating current (AC) convenience outlets from battery-based direct current (DC) power system. These AC convenience outlets may be employed by a user for powering any of a variety of AC loads, ranging from laptop power supplies to household appliances and the like. Exemplary battery-based DC power systems may include electric vehicles, grid-battery-storage systems, portable power banks, and other systems. Battery-based DC systems may have an AC grid connection for charging the battery and an associated charger (i.e., AC-DC converter) for converting the AC grid power to DC power suitable for charging the battery. In some applications, inclusion of an additional converter to generate the AC voltage needed for the convenience outlet(s) may not be desirable. 
     SUMMARY 
     In some cases, it may be desirable to repurpose this converter to generate the AC voltage needed for the convenience outlet. For example, this can reduce power device component count, cost, and weight of the battery-based DC power system. Exemplary arrangements along these lines are described herein. 
     An electrical system can include a first bidirectional AC-DC converter having an AC input couplable to an AC grid connection and a DC output couplable to a battery, and a second bidirectional AC-DC converter having an AC input selectively couplable to the AC grid connection or a convenience outlet and a DC output couplable to the battery. 
     The second bidirectional AC-DC converter AC input may be selectively couplable to the AC grid connection or the convenience outlet by first and second switches. The first switch can be coupled between the AC input of the first bidirectional AC-DC converter and the AC input of the second bidirectional AC-DC converter, and the second switch can be coupled between the AC input of the second bidirectional AC-DC converter and the convenience outlet. The second switch can be further coupled between the first switch and the convenience outlet. The first and second switches can be single pole switches. 
     The electrical system can further include a controller configured to toggle the first and second switches and control operation of the first and second bidirectional converters to operate in one of a plurality of modes including a two-stage charging mode in which the controller operates both the first and second bidirectional converters in a forward direction to charge the battery, a single-stage charging mode in which the controller operates the first bidirectional converter in a forward direction to charge the battery and operates the second bidirectional converter in a reverse direction to power the convenience outlet, and a non-charging mode in which the controller idles the first bidirectional converter and operates the second bidirectional converter in a reverse direction to power the convenience outlet. In the two-stage charging mode the controller can close the first switch and open the second switch, and in the single-stage charging mode and the non-charging mode the controller can open the first switch and close the second switch. 
     The electrical system can further include a controller configured to control operation of the first and second bidirectional converters to operate in one of a plurality of modes including a two-stage charging mode in which the controller operates both the first and second bidirectional converters in a forward direction to charge the battery, a single-stage charging mode in which the controller operates the first bidirectional converter in a forward direction to charge the battery and operates the second bidirectional converter in a reverse direction to power the convenience outlet, and a non-charging mode in which the controller idles the first bidirectional converter and operates the second bidirectional converter in a reverse direction to power the convenience outlet. 
     A method performed by a controller of an electrical system having an AC grid connection, a DC battery connection, an AC convenience outlet connection, two bidirectional AC-DC converters, and a controller can include determining whether operation of the convenience outlet is required, and, if not, coupling AC inputs of the two bidirectional AC-DC converters to the AC grid connection and operating the two bidirectional AC-DC converters in a forward direction to charge a DC battery coupled to the DC battery connection. If operation of the convenience outlet is required, the method can further include determining at least one of whether an AC grid is connected to the AC grid connection and whether battery charging is required, and, if either an AC grid is not connected or battery charging is not required, idling a first of the two bidirectional AC-DC converters, coupling an AC input of a second of the two-bidirectional AC-DC converters to the convenience outlet, and operating the second bidirectional AC-DC converter in a reverse direction to power the convenience outlet. 
     If an AC grid is connected and battery charging is required, the method can further include determining if the connected AC grid voltage is suitable for the convenience outlet. If the AC grid voltage is suitable for the convenience outlet the method can further include coupling AC inputs of the two bidirectional AC-DC converters to the AC grid connection and operating the two bidirectional AC-DC converters in a forward direction to charge a DC battery coupled to the DC battery connection and coupling the AC grid to the convenience outlet. If the AC grid voltage is not suitable for the convenience outlet, the method can further include coupling an AC input of a first of the two bidirectional AC-DC converters to the AC grid connection, operating the first bidirectional AC-DC converter in a forward direction to charge a DC battery coupled to the DC battery connection, coupling an AC input of a second of the two-bidirectional AC-DC converters to the convenience outlet, and operating the second bidirectional AC-DC converter in a reverse direction to power the convenience outlet. 
     A method performed by a controller of an electrical system having an AC grid connection, a DC battery connection, an AC convenience outlet connection, two bidirectional AC-DC converters, a plurality of switches, and a controller, can include determining whether operation of the convenience outlet is required and, if not, toggling the plurality of switches to couple AC inputs of the two bidirectional AC-DC converters to the AC grid connection and operating the two bidirectional AC-DC converters in a forward direction to charge a DC battery coupled to the DC battery connection. If operation of the convenience outlet is required, the method can further include determining at least one of whether an AC grid is connected to the AC grid connection and whether battery charging is required, and, if either an AC grid is not connected or battery charging is not required, idling a first of the two bidirectional AC-DC converters, toggling the plurality of switches to couple an AC input of a second of the two-bidirectional AC-DC converters to the convenience outlet, and operating the second bidirectional AC-DC converter in a reverse direction to power the convenience outlet. 
     If an AC grid is connected and battery charging is required, the method can further include determining if the connected AC grid voltage is suitable for the convenience outlet. If the AC grid voltage is suitable for the convenience outlet the method can further include toggling the plurality of switches to couple AC inputs of the two bidirectional AC-DC converters to the AC grid connection and operating the two bidirectional AC-DC converters in a forward direction to charge a DC battery coupled to the DC battery connection and coupling the AC grid to the convenience outlet. If the AC grid voltage is not suitable for the convenience outlet, the method can further include toggling the plurality of switches to couple an AC input of a first of the two bidirectional AC-DC converters to the AC grid connection and to couple an AC input of a second of the two-bidirectional AC-DC converters to the convenience outlet, operating the first bidirectional AC-DC converter in a forward direction to charge a DC battery coupled to the DC battery connection, and operating the second bidirectional AC-DC converter in a reverse direction to power the convenience outlet. 
     An electrical system can include an isolated bidirectional converter having an input couplable to an AC grid connection and an output couplable to a battery and a non-isolated converter having an input coupled to the input of the isolated bidirectional converter and selectively couplable to the AC grid connection and an AC output coupled to a convenience outlet. The input of the isolated bidirectional converter and the input of the non-isolated converter can be selectively couplable to the AC grid connection by a switch. The switch can be a single pole switch. The electrical system can further include a controller configured to toggle the switch and control operation of the isolated bidirectional converter and the non-isolated converter to operate in one of a plurality of modes, including a charging mode in which the isolated bidirectional converter operates in a forward direction to charge the battery and the non-isolated converter powers the convenience outlet from the grid connection and a non-charging mode in which the isolated bidirectional converter operates in a reverse direction to power the non-isolated converter from the battery and the non-isolated converter powers the convenience outlet. In the charging mode the controller can close the switch, and in the discharging mode the controller can open the switch. 
     The charging mode can include at least one of a power factor correction mode and a harmonics compensation mode. In the power factor correction mode the isolated bidirectional converter can be operated to correct the power factor of a load coupled to the convenience outlet such that the grid connection sees a unity power factor. In the harmonics compensation mode the isolated bidirectional converter can be operated to compensate for harmonics introduced by the load coupled to the convenience outlet. The discharging mode can include at least one of: a first discharging mode in which the isolated bidirectional converter is operated in the reverse direction to produce an output voltage having a magnitude tracking the battery voltage; a second discharging mode in which the isolated bidirectional converter is operated in the reverse direction to produce an output voltage having a magnitude suitable for the convenience outlet; and a third discharging mode in which the isolated bidirectional converter is operated in the reverse direction to produce an output voltage having a magnitude corresponding to a voltage of the AC grid. In the first discharging mode the isolated bidirectional converter can perform regulation of the output voltage for the convenience outlet. In the second discharging mode the isolated bidirectional converter can operate as a pass-through. In the third discharging mode the isolated bidirectional converter can operate as a fixed ratio converter. In each discharging mode the output voltage can be an AC or a DC voltage. 
     The AC-AC converter can include a stack of four switching devices. An input of the AC-AC converter can be coupled across the stack of four switching devices, and an output of the AC-AC converter can be taken from a connection point of first and second switching devices of the stack and a junction of third and fourth switching devices of the stack. The converter can further include input capacitors coupled in series across the input of the AC-AC converter, with a connection point of the input capacitors coupled to a connection point of the second and third switching devices. The converter can further include at least one output filter inductor and at least one output filter capacitor coupled to the output of the AC-AC converter. The AC-AC converter can further include a resonant tank made up of at least one resonant capacitor and at least one resonant inductor, wherein the resonant tank facilitates zero voltage switching of the switching devices. Alternatively, the AC-AC converter can include a plurality of bidirectional switching devices, wherein an input of the AC-AC converter is coupled across the bidirectional switching devices and an output of the AC-AC converter is taken from a connection point of the bidirectional switching devices. Such a converter can further include at least one input capacitor coupled across the input of the AC-AC converter and at least one output filter inductor and at least one output filter capacitor coupled to the output of the AC-AC converter. The bidirectional switches can be configured as a full bridge converter or as a half bridge converter. 
     A method can be performed by a controller of an electrical system having an AC grid connection, a DC battery connection, an AC convenience outlet connection, an isolated bidirectional converter, a non-isolated converter, and a controller. The method can include determining whether an AC power source is coupled to the AC grid connection and, if not, operating the isolated bidirectional converter in a reverse direction to provide power to the non-isolated converter from the battery and operating the non-isolated converter to power the convenience outlet. If an AC power source is coupled to the AC grid connection, the method can further include operating the isolated bidirectional converter in a forward direction to charge the battery from the AC grid and operating the non-isolated converter to power the convenience outlet from the AC grid. Operating the isolated bidirectional converter in a forward direction to charge the battery from the grid and operating the non-isolated converter to power the convenience outlet from the AC grid can further include comprises at least one of a power factor correction mode and a harmonics compensation mode. In the power factor correction mode, operating the isolated bidirectional converter can include correcting the power factor of a load coupled to the convenience outlet such that the grid connection sees a unity power factor. In the harmonics compensation mode, operating the isolated bidirectional converter can include compensating for harmonics introduced by the load coupled to the convenience outlet. 
     Operating the isolated bidirectional converter in the reverse direction to provide power to the non-isolated converter from the battery and operating the non-isolated converter to power the convenience outlet can include at least one of three discharging modes. In a first discharging mode, operating the isolated bidirectional converter in the reverse direction can include producing an output voltage having a magnitude tracking the battery voltage. In a second discharging mode, operating the isolated bidirectional converter in the reverse direction can include producing an AC output voltage having a magnitude suitable for the convenience outlet. In a third discharging mode, operating the isolated bidirectional converter in the reverse direction can include producing an AC output voltage having a magnitude corresponding to a voltage of the AC grid. In the first discharging mode operating the non-isolated converter can include regulating the output voltage for the convenience outlet. In the second discharging mode, operating the non-isolated converter can include operating as a pass-through. In the third discharging mode, operating the non-isolated converter comprises operating as a fixed ratio converter. In each discharging modes the output voltage can be an AC or a DC voltage. 
     An AC-AC converter can include a stack of four switching devices. An input of the AC-AC converter can be coupled across the stack of four switching devices, and an output of the AC-AC converter can be taken from first terminal coupled to a connection point of first and second switching devices of the stack and a second terminal coupled to a connection point of third and fourth switching devices of the stack. The AC-AC converter can further include first and second series-connected input capacitors coupled across the input of the AC-AC converter, with a connection point of the series-connected input capacitors coupled to a connection point of the second and third switching devices. The AC-AC converter can further include at least one output filter inductor and at least one output filter capacitor coupled to the output of the AC-AC converter. The at least one filter inductor can include a first filter inductor coupled between the first terminal and a load. The at least one filter inductor can include a second inductor coupled between the second terminal and the load. 
     The AC-AC converter can further include a resonant tank made up of at least one resonant capacitor and at least one resonant inductor. The resonant tank can facilitate zero voltage switching of the switching devices. The resonant tank can be a series resonant circuit coupled between the first terminal and the second terminal. The resonant tank can be a series resonant circuit coupled in parallel with the at least one output filter inductor. 
     The AC-AC converter can further include a controller that operates the switching devices such that during a positive half cycle of an AC input voltage, first and second switching devices of the stack are operated with an alternating 50% duty cycle and third and fourth switching devices of the stack are constantly on, and during the negative half cycle of the AC input voltage, the third and fourth switching devices of the stack are operated with an alternating 50% duty cycle and the first and second switching devices of the stack are constantly on. During the positive half cycle, the duration of the on-times of the first and second switching devices determine the magnitude of the AC voltage between the first and second terminals. During the negative half cycle, the duration of the on times of the third and fourth switching devices determine the magnitude of the AC voltage between the first and second terminals. 
     A method performed by a controller of an AC-AC converter having a stack of four switching devices, wherein an input of the AC-AC converter is coupled across the stack of four switching devices and an output of the AC-AC converter is taken from first terminal coupled to a connection point of first and second switching devices of the stack and a second terminal coupled to a connection point of third and fourth switching devices of the stack, can include, during a positive half cycle of an AC input voltage, operating first and second switching devices of the stack with an alternating 50% duty cycle and turning on and leaving on third and fourth switching devices of the stack; and during a negative half cycle of the AC input voltage, operating the third and fourth switching devices of the stack with an alternating 50% duty cycle, and turning on and leaving on the first and second switching devices of the stack. During the positive half cycle, the duration of the on-times of the first and second switching devices can determine the magnitude of the AC voltage between the first and second terminals, and, during the negative half cycle, the duration of the on times of the third and fourth switching devices determine the magnitude of the AC voltage between the first and second terminals. The switching devices can be operated with zero voltage switching. 
     An AC-AC converter can include a plurality of bidirectional switching devices. An input of the AC-AC converter can be coupled across the bidirectional switching devices, and an output of the AC-AC converter is taken from a connection point of the bidirectional switching devices. The converter can further include at least one input capacitor coupled across the input of the AC-AC converter and at least one output filter inductor and at least one output filter capacitor coupled to the output of the AC-AC converter. The bidirectional switches can be configured as a full bridge converter or as a half bridge converter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a block diagram of an exemplary battery-based DC power system. 
         FIG.  2    illustrates prior art configurations for generating an AC voltage. 
         FIG.  3 A  illustrates a two-stage charger circuit in which one phase may be reused as an inverter to provide an AC voltage. 
         FIG.  3 B  illustrates a flow chart of operating modes of the two-stage charger circuit of  FIG.  3 A . 
         FIG.  3 C  illustrates alternative switch configurations of the charger circuit in  FIG.  3 A . 
         FIG.  4 A  illustrates a single-stage charger and non-isolated AC-AC converter circuit that may be used to provide an AC voltage. 
         FIG.  4 B  illustrates alternative switch configurations of the charger circuit in  FIG.  4 A . 
         FIG.  5    illustrates power factor correction operating modes of a single-stage charger and non-isolated AC-AC converter circuit. 
         FIG.  6 A  illustrates certain operating modes of a single-stage charger and non-isolated AC-AC converter circuit. 
         FIG.  6 B  illustrates additional operating modes of a single-stage charger and non-isolated AC-AC converter circuit. 
         FIG.  7    illustrates a flow chart of operating modes of a single-stage charger and non-isolated AC-AC converter circuit. 
         FIG.  8    illustrates exemplary topologies for a non-isolated AC-AC converter. 
         FIG.  9    illustrates further exemplary topologies for a non-isolated AC-AC converter. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosed concepts. As part of this description, some of this disclosure&#39;s drawings represent structures and devices in block diagram form for sake of simplicity. In the interest of clarity, not all features of an actual implementation are described in this disclosure. Moreover, the language used in this disclosure has been selected for readability and instructional purposes, has not been selected to delineate or circumscribe the disclosed subject matter. Rather the appended claims are intended for such purpose. 
     Various embodiments of the disclosed concepts are illustrated by way of example and not by way of limitation in the accompanying drawings in which like references indicate similar elements. For simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the implementations described herein. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant function being described. References to “an,” “one,” or “another” embodiment in this disclosure are not necessarily to the same or different embodiment, and they mean at least one. A given figure may be used to illustrate the features of more than one embodiment, or more than one species of the disclosure, and not all elements in the figure may be required for a given embodiment or species. A reference number, when provided in a given drawing, refers to the same element throughout the several drawings, though it may not be repeated in every drawing. The drawings are not to scale unless otherwise indicated, and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
       FIG.  1    illustrates a high level block diagram of an arrangement  100  including a DC electrical system  101 . Electrical system  101  may be coupled to one or more of multiple power sources, including a high voltage battery  102 , a low voltage battery  103 , and an AC grid  105 . In the illustrated example, high voltage battery  102  may have a voltage ranging from 400-800V DC, although other voltage ranges may be used if appropriate for a given application. As used herein, “high voltage” generally means a voltage higher than the nominal utility supply voltage for plug-in devices in residential or commercial service, e.g., 120V in the U.S. or 230V in Europe. Similarly, low voltage battery  103  may have a voltage ranging from 30-50V DC, although other voltage ranges may be used if appropriate for a given application. As used herein, “low voltage” generally means a voltage lower than the nominal utility supply voltage for typical residential or commercial service as described above. The charging grid may be any standardized voltage available in the United States or other regions of the world. In the United States, typical AC grid voltages for residential or commercial service include 120V, 208V, and/or 240V AC, including single phase, spilt phase, and three phase configurations. In various applications, electrical system  101  may also be operable to deliver power to one or more of these power “sources,” as well as to its own internal loads (e.g., the traction motor(s) of an electric vehicle). 
     To that end, electrical system  101  may include various power conversion circuitry, described in greater detail below, for converting electrical energy received from one or more of the “sources” to a level suitable for another of the “sources.” For example, electrical system  101  may include circuitry for converting the voltage from AC grid  105  into a suitable voltage for charging high voltage battery  102  and/or low voltage battery  103 . This arrangement may be included in applications such as electric vehicles, uninterruptible power supplies, grid battery storage systems, etc. Additionally or alternatively, electrical system  101  may include circuitry for converting the voltage from high voltage battery  102  and/or low voltage battery  103  to the grid voltage. Such applications may include UPSs and grid battery storage systems. In many applications, including each of the foregoing as well as others, it may also be desirable to provide power to an AC “convenience outlet”  104  that may be used to power any of a variety of typical AC loads, such as laptop chargers, small appliances, etc. There could be any number of reasons that it may be desirable to use some of the above-described power conversion circuitry as an inverter (i.e., DC to AC converter) produce the AC voltage for convenience outlet  104 . Some such reasons include cost reduction, weight reduction, size reduction, and the like. 
       FIG.  2    illustrates two prior art approaches for powering AC convenience outlets from battery-based DC power systems. Approach  210  employs an isolated AC-DC charger  216  to convert voltage from the AC grid  215  to a level suitable for high voltage battery  212 . Because of the high battery voltage, an isolated inverter  217  is provided to generate the low voltage AC (e.g., 120V AC) that powers convenience outlet  226 . Approach  220  employs an isolated AC-DC charger  226  to convert voltage from the AC grid  225  to a level suitable for high voltage battery  222 . However, because convenience outlet is powered from low voltage battery  223 , a non-isolated inverter  227  may be used. (Not shown in approach  220  is a mechanism for charging low voltage battery, which may be done from the high voltage DC bus corresponding to high voltage. battery  222  and/or from the AC bus corresponding to AC grid  225 .) A disadvantage of either arrangement is the requirement of additional converter hardware, i.e., isolated inverter  217  or non-isolated inverter  227 , which adds cost, complexity, weight, and volume to a given device. Further disadvantages of approach  220  include the requirement for two conversion stages (a DC-DC boost stage to increase the voltage from the low voltage battery and an inverter stage to generate the AC voltage) and the potential for high current draw from the low voltage battery (depending on the load on the convenience outlet). 
       FIG.  3 A  illustrates a battery based electrical system  300  using a high voltage battery  302 . Electrical system  300  includes dual isolated AC-DC charger stages  306  and  307 . Charger stages  306  and  307  may be bidirectional chargers, allowing for power delivery in either direction, i.e., either as AC-DC converters in the forward direction or DC-AC converters in the reverse direction. Various examples of such converters are known to those ordinarily skilled in the art, and thus the details of their construction, control, and operation are omitted for brevity. Charger stages  306  and  307  may be operated in parallel in the forward direction to charge high voltage battery  302  from AC grid  305 , allowing for the combined power rating of the two stages to be delivered to the battery for more rapid charging. Additionally, charger stage  307  may be operated in the reverse direction as an isolated DC-AC converter (i.e., inverter) allowing for convenience outlet  304  to be powered from high voltage battery  305 . Switches S 1  and S 2  may be provided to allow for directly powering convenience outlet  304  from AC grid  305  if connected to a suitable voltage and/or for isolating the AC side of charger stage  307  from the AC grid when used as an inverter to power convenience outlet  304 . This can result in various operating modes  310 ,  320 , and  330 , illustrated on the right side of  FIG.  3 A . 
     Operating mode  310  corresponds to the dual stage charging operation described above. In this mode, isolated charger  306  is operated in the forward direction  318  to deliver power from AC grid  305  to high voltage battery  302 . Switch S 1  is closed, and switch S 2  is opened. Thus, power is not provided to convenience outlet  304 , but the AC side of isolated charger  307  is connected to AC grid  305 . Isolated charger  307  is also operated in the forward direction  319  to deliver power from AC grid  305  to high voltage battery  302 . In this mode, the amount of power delivered to high voltage battery  302  is increased, e.g., doubled as compared to mode  320 , but convenience outlet may not be available. (In some applications, if a suitable voltage is supplied by grid  305 , switch S 2  could also be closed, coupling AC grid  305  to convenience outlet  304 . Additional overcurrent protection (not shown) for convenience outlet  304  may be necessary in this configuration. 
     Operating mode  320  corresponds to one stage charging, one stage inverting operation as described above. In this mode, isolated charger  306  is operated in the forward direction  328  to deliver power from AC grid  305  to high voltage battery  302 . Switch S 1  is open, and switch S 2  is closed. Thus, power from AC grid  305  is not provided to the AC side of isolated converter  307 , which may now be operated in reverse direction  329  as an inverter to power convenience outlet  304 . In this mode, the amount of power delivered to high voltage battery  302  is decreased, e.g., halved as compared to mode  310 , but convenience outlet is available for use. 
     Operating mode  330  corresponds to no charging, with one stage inverting operation. In this mode, isolated charger  306  is not operated, e.g., because grid  305  is not available. (Mode  330  could also be used when AC grid  305  is available but high voltage battery  302  is fully charged. Switch S 1  is open, and switch S 2  is closed. Thus, the AC sides of converters  306  and  307  are decoupled/disconnected. Converter  307  may be operated in reverse direction  329  as an isolated inverter to power convenience outlet  304 . In the foregoing description, of operating modes  310 ,  320 , and  330 , switches S 1  and S 2  are illustrated as single pole switches; however, double pole switches could be provided to disconnect the line and/or neutral legs if desired in a given application. Such configurations are illustrated in  FIG.  3 C  in which additional switch poles S 1 ′ and S 2 ′ are illustrated with switch poles S 1  and S 1 ′ having the same switching state and switches S 2  and S 2 ′ having the same switching state. 
       FIG.  3 B  illustrates a flow chart of an operating method  380  of the converter and operating modes of  FIG.  3 A . The flow chart may be implemented by any suitable controller circuitry, including a programmable controller (such as a microcontroller or microprocessor), a field programmable gate array, discrete logic control circuits, application specific integrated circuits, etc. Beginning at block  381 , the controller can determine whether the convenience outlet is required. If not, in block  382 , the electrical system can be placed in Mode  1  (discussed above) including two stage charging. In this mode, switch S 1  is closed and switch S 2  is open, and both isolated charger stages are operated in the forward direction to charge the high voltage battery from the AC grid. 
     In block  381 , if the controller determines that the convenience outlet is required, then the controller can determine whether the AC grid is available and if charging the high voltage battery is required (block  383 ). If either the AC grid is not available or if HV charging is not required, the controller can enter Mode  3  (block  384 ) in which one converter is idled and one stage is operated as an inverter. In this mode, switch S 1  is open and switch S 2  is closed. Otherwise, in block  383 , if the controller determines that the AC grid is available and HV charging is required, then in block  385  the controller can determine whether the grid voltage is suitable for direct connection to the convenience outlet. If so, the controller can enter mode  4  (block  387 ) in which one stage is charging, one stage is operating as an inverter, and both switches S 1  and S 2  are closed. Otherwise, the controller can enter mode  2  (block  386 ) in which one stage is charging one stage is operating as an inverter, and switch S 1  is open and switch S 2  is closed. 
       FIG.  4 A  illustrates a battery based electrical system  400  using a high voltage battery  402 . Electrical system  400  includes a single isolated AC-DC charger stage  406 . Charger stage  406  may be a bidirectional charger, allowing for power delivery in either direction, i.e., either as an AC-DC converter in the forward direction or DC-AC converter in the reverse direction. In some embodiments, isolated charger stage  406  may also be operated as a DC-DC converter, as described in greater detail below. Additionally, a non-isolated AC-AC converter  407  may be provided, which can convert the voltage appearing at the AC side of converter  406  to a suitable level for convenience outlet  404 . In some embodiments, non-isolated converter  407  can be operated as a DC-AC converter (i.e., inverter), as described in greater detail below. Various examples of both converter types are known to those ordinarily skilled in the art, and thus the details of their construction, control, and operation are omitted here for brevity, although exemplary AC-AC converters are described below with reference to  FIGS.  8  and  9   . Charger stage  406  may be operated in the forward direction to charge high voltage battery  402  from AC grid  405  and also powering AC-AC converter  407 , which, in turn, powers convenience outlet  404 . Alternatively, charger stage  406  may be operated in the reverse direction as an isolated DC-AC converter (i.e., inverter) allowing for convenience outlet  404  to be powered from high voltage battery  402 . Switch S may be provided for isolating the AC side of charger stage  307  from the AC grid when used as an inverter to power convenience outlet  304 . This can result in charging operating mode  410  and non-charging operating mode  420  illustrated in the lower portion of  FIG.  4 A . 
     Operating mode  410  corresponds to the charging operation described above. In this mode, isolated charger  406  is operated in the forward direction  418  to deliver power from AC grid  405  to high voltage battery  402 . Switch S is closed. Thus, power  429  is provided to convenience outlet  304  via AC-AC converter  407 . Operating mode  420  corresponds to the not charging operation described above. In this mode, isolated charger  406  is operated in the reverse direction  428  to deliver power from high voltage battery  402  to AC-AC converter  407 . Switch S is open, thereby isolating the AC grid  405  connection from converters  406  and  407 . In some embodiments, switch S could be a two pole switch with additional switch pole S′ serving to disconnect the grid neutral connection as illustrated in  FIG.  4 B . In such configurations, switch poles S and S′ have the same switching state. 
     Charging mode  410  of electrical system  400  can allow for different HV battery charging modes to address power factor and harmonics, which are illustrated in  FIG.  5   . In a first power factor/harmonics corrected charging mode  530 , a load imposed on convenience outlet  404  may exhibit a leading power factor, as illustrated in current/voltage plot  534 . Such a load may also include relatively high harmonic content, which is not shown. As a result, the input side of AC-AC converter  407  may also exhibit a leading power factor, as illustrated in current voltage plot  537  (and also high harmonic distortion, not shown). To compensate for this, isolated AC-DC converter  506 , operating in the charging mode, may be operated to exhibit a lagging power factor, as illustrated in current/voltage plot  536 . More specifically, switching devices of DC-AC converter  406  may be adjusted so that a phase relationship between the input current and voltage of converter  406  (as shown in plot  536 ) corresponds to but is opposite in sense (lagging vs. leading) from a phase relationship between the input current and voltage of converter  407  (as shown in plot  537 ). Additionally, the switching devices of converter  406  may be operated to compensate for the harmonic content. As a result, AC grid  405  sees unity power factor operation, i.e., the input current and voltage are in phase, and a relatively harmonic free load. In this power factor and/or harmonic corrected mode, the power and reactive power needed to mitigate the harmonics and power factor are sourced from battery  402 , which may result in some voltage variation of the high voltage battery, as illustrated by high voltage battery plot  532  (which also illustrates the overall charging operation). In some cases, convenience outlet  404  may exhibit a lagging power factor, in which case converter  406  could be operated to exhibit a leading power factor, thereby providing unity power factor operation as seen by grid  405 . 
     In a second power factor/harmonics un-corrected charging mode  540 , a load imposed on convenience outlet  404  may exhibit a leading power factor, as illustrated in current/voltage plot  544 . Such a load may also include relatively high harmonic content, which is not shown. As a result, the input side of AC-AC converter  407  may also exhibit a leading power factor, as illustrated in current voltage plot  547  (and also high harmonic distortion, not shown). However, instead of compensating for this, isolated AC-DC converter  506 , operating in the charging mode, may be operated to exhibit a unity power factor, as illustrated in current/voltage plot  546 . As a result, AC grid  405  will not see unity power factor operation, i.e., the input current and voltage will be out of in phase, and will see the harmonic distortion associated with the load on convenience outlet for. An advantage of un-corrected mode  540  is that fewer voltage and current measurements are required and the control of AC-DC converter  406  may be simplified, as it need not adapt to the load presented via convenience outlet  404 . The corresponding disadvantage is that the non-unity power factor and/or harmonic distortion introduced by the load on convenience outlet  404  will be seen by AC grid  405 . Also, while it is in principle possible to separate power factor correction from harmonic compensation, the additional sensor and control capabilities required for either are essentially the same as required for both. Thus, as a practical matter, power factor correction and harmonic compensation are likely to be provided together (as in mode  530 ) or not provided (as in mode  540 ). 
     Discharging mode  420  of Electrical system  400  can also allow for different HV battery discharging modes to enhance overall system efficiency. These different discharging modes  650 ,  660 , and  670  are illustrated in  FIG.  6 A . In each of the discharging modes, energy flows from high voltage battery  402  to charger/converter  406  via path  602 . Converter  406  converts this into an AC voltage delivered to AC-AC converter  407  via path  606 . AC-AC converter  407  then converts this to a voltage suitable for convenience outlet  404 , which is delivered via path  607 . 
     In a first discharging mode  650 , converter  406  may be operated at its maximum possible efficiency, meaning it will generate an AC output voltage with a magnitude that tracks the battery voltage  652  as illustrated in plot  657 . In other words, the magnitude of this voltage will decrease as the battery discharges. In this mode, AC-AC converter  407  will perform the regulation necessary to produce the desired voltage  654  (e.g., 120V AC) for convenience outlet  404 . As a result, converter  407  may exhibit relatively lower efficiency. 
     In second discharging mode  660 , converter  406  may be operated to generate an AC output voltage suitable for convenience outlet  404 , as illustrated in plot  667  (and  664 ), regardless of battery voltage  662 . As a result, converter  406  may operate with relatively lower efficiency. However, in this mode, AC-AC converter  407  need not perform any further regulation, and, as a result, may exhibit very high efficiency. 
     In a third discharging mode  670 , converter  406  may be operated to generate an AC output voltage  677  corresponding to the normally supplied grid voltage (e.g., 240V or 208V AC), without regard to battery voltage  672 . As a result, converter  406  will operate with an intermediate efficiency between the two previously discussed modes  650  and  660 . In mode  670 , AC-AC converter  407  will perform a step-down as in one of the charging modes discussed above with reference to  FIG.  5   , and, as a result, converter  407  will exhibit an intermediate efficiency between the two previously discussed modes  650  and  660 . 
     Depending on the specifics of a particular implementation, one of the foregoing modes  650 ,  660 , or  670  may be more efficient. Thus, the mode providing optimal efficiency may be selected. 
     A second set of discharging modes may also be available for at least some topologies of converters  406  and  407 , illustrated in  FIG.  6 B . In these discharging mode, isolated bidirectional converter  406   a  may be operated as a DC-DC converter to generate a DC output voltage that may be passed via path  606  to non-isolated converter  407   a , which may be operated as an inverter to generate the AC voltage required by convenience outlet  404 . For some converter topologies this may provide an overall system efficiency greater than any of the DC-AC modes  650 ,  660 ,  670  discussed above. In discharging mode  651 , converter  406   a  may be operated at its maximum possible efficiency, meaning it will generate an output voltage with a magnitude that tracks the battery voltage  652  as illustrated in plot  657   a . In other words, the magnitude of this voltage will decrease as the battery discharges. In this mode, DC-AC converter  407   a  will perform the regulation necessary to produce the desired voltage  654  (e.g., 120V AC) for convenience outlet  404 . As a result, converter  407   a  may exhibit relatively lower efficiency. 
     In discharging mode  661 , converter  406   a  may be operated to generate an output voltage with a magnitude suitable for convenience outlet  404 , as illustrated in plot  667   a  (and  664 ), regardless of battery voltage  662 . As a result, converter  406   a  may operate with relatively lower efficiency. However, in this mode, DC-AC converter  407   a  need not perform any further regulation, instead being used in, for example, an open loop  1 ;  1  inverter mode. As a result, converter  407   a  may exhibit very high efficiency. 
     In discharging mode  671 , converter  406   a  may be operated to generate an output voltage  677   a  corresponding to the normally supplied grid voltage (e.g., 240V or 208V AC), without regard to battery voltage  672 . As a result, converter  406   a  will operate with an intermediate efficiency between the two previously discussed modes  650  and  660 . In mode  671 , DC-AC converter  407   a  will perform a step-down as in one of the charging modes discussed above with reference to  FIG.  5   . For example, converter  407   a  can operate in an open loop  2 : 1  step down inverter mode. As result, converter  407   a  will exhibit an intermediate efficiency between the two previously discussed modes  651  and  661 . Depending on the specifics of a particular implementation, one of the foregoing modes  650 ,  660 , or  670  may be more efficient. Thus, the mode providing optimal efficiency may be selected. 
       FIG.  7    illustrates a flow chart of an operating method  780  of the converter and operating modes of  FIGS.  4 - 6   . The flow chart may be implemented by any suitable controller circuitry, including a programmable controller (such as a microcontroller or microprocessor), a field programmable gate array, discrete logic control circuits, application specific integrated circuits, etc. Beginning at block  781 , the controller can determine whether the AC grid is connected. If not, in block  782 , the electrical system can be placed in the discharging mode  410 , which can be selected from discharging modes  650 ,  660 ,  670 , or the DC mode discussed above with reference to  FIG.  6 A . In this mode, switch S is open and isolated converter/charger  406  operates to provide power to converter  407  (and thus convenience outlet  404 ). 
     In block  381 , if the controller determines that the AC grid is connected, then the controller can enter charging mode  420  (block  783 ), which can be selected from power factor correction and harmonics compensation charging modes  530  or  540  discussed above with reference to  FIG.  5   . In this mode, switch S is closed and isolated converter/charger  406  operates to provide power to the high voltage battery while the grid powers converter  407  (and thus convenience outlet  404 ). 
       FIG.  8    illustrates exemplary AC-AC converter topologies  891 , 892 , and  893  that may be used for converter  407  in the arrangements of  FIGS.  4 - 7   . Each converter topology  891 - 893  includes a stacked switching arrangement made up of switches SaP, SaN, SbN, and SbQ. An input AC voltage  856  may be input across the full switch stack at terminals P and Q. (In the DC embodiment discussed above, this input voltage may also be a DC input voltage.) An output AC voltage may be taken from the intermediate nodes a (located at the connection point of switches SaP and SaN) and b (located at the connection point of switches SbN and SbQ). In the illustrated embodiments, switches SaP and SaN are illustrated as n-channel MOSFETs, and switches SbQ and SbN are illustrated as p-channel MOSFETs; however, any suitable switching devices could be used as appropriate for a given implementation. Input capacitors may be coupled across the input, with their junction point being coupled to the neutral leg switches SaN and SbN. in each of the topologies  891 , 892 , and  893 , output terminals a and b may be coupled to convenience outlet  804  by different inductor/capacitor networks further described below. 
     For operation as an AC-AC converter, each topology  891 - 893  may be operated using pulse width modulation to generate the desired output voltage for convenience outlet  804 . During the positive half cycle of AC input voltage  856 , switches SaP and SaN may be operated with an alternating 50% duty cycle, while switches SbN/SbQ are constantly on. The width of the on-time pulses (i.e., the duration of the on times) of switches SaP and SaN will determine the magnitude of the AC voltage between terminals a and b (and thus presented to convenience outlet  804 ). During the negative half cycle of AC input voltage  856 , switches SbQ and SbN may be operated with an alternating 50% duty cycle, while switches SaP/SaN are constantly on. The width of the on-time pulses (i.e., the duration of the on times) of switches SbQ and SbN will determine the magnitude of the AC voltage between terminals b and a (and thus presented to convenience outlet  804 ). This PWM mode of operation is applicable to all of the operating modes described above with reference to  FIGS.  4 - 7    in which converter  407  provides AC voltage regulation for convenience outlet  404 / 804 . Alternatively, converter topologies may also operate in a pass-through mode, in which the input voltage appearing across terminals P/Q is passed directly to output terminals a/b. In this mode, switches SaP an SaQ are turned on and switches SbQ and SbN are turned off. This passthrough mode of operation is applicable to all of the operating modes described above with reference to  FIGS.  4 - 7    in which converter  407  does not provide AC voltage regulation for convenience outlet  404 / 804 . 
     In topology  891 , output filter inductors Lo and output filter capacitor Co are provided to smooth the output voltage delivered to convenience outlet  804 . In topologies  892  and  893 , resonant capacitor Cr and resonant inductor Lr may also be provided to form a resonant tank that allows for zero voltage switching (ZVS) of the switching devices. More specifically, when alternating from the positive half cycle to the negative half cycle, or vice versa, resonance of the tank circuit provides a current reversal to force the filter inductor current negative allowing for zero voltage switching. 
       FIG.  9    illustrates additional AC-AC topology configurations that incorporate bidirectional switches. Topology  894  illustrates a full bridge AC-AC converter using bidirectional switches SaP, SbP, SaN, and SbN. Topology  895  illustrates a half bridge AC-AC converter with switches SaP and SaN. In each configuration, an input AC voltage  856  may be input at terminals P and Q. In the full bridge configuration  894 , an output AC voltage may be taken from the intermediate nodes a (located at the connection point of switches SaP and SaN) and b (located at the connection point of switches SbP and SbN). In the half bridge configuration  895 , an output AC voltage may be taken from intermediate nodes a (located at the connection point of switches SaP and SaN) and b (located at the connection point of input capacitors C 1  and C 2 ). 
     For operation as an AC-AC converter, each topology  894 - 895  may be operated using pulse width modulation to generate the desired output voltage for convenience outlet  804 . Such PWM modes of operation are broadly similar to those discussed above, accounting for the bidirectionality of the switching devices. These PWM modes of operation are applicable to all of the operating modes described above with reference to  FIGS.  4 - 7    in which converter  407  provides AC voltage regulation for convenience outlet  404 / 804 . Alternatively, converter topologies may also operate in a pass-through mode, in which the input voltage appearing across terminals P/Q is passed directly to output terminals a/b. This passthrough mode of operation is applicable to all of the operating modes described above with reference to  FIGS.  4 - 7    in which converter  407  does not provide AC voltage regulation for convenience outlet  404 / 804 . Additionally, converter topologies  894 - 895  can include output filter and zero voltage switching circuits as described above with respect to  FIG.  8   . 
     The foregoing describes exemplary embodiments of battery-based DC power systems that may repurpose charger circuitry to provide an AC voltage for convenience outlets or other AC loads. Such systems may be used in a variety of applications but may be particularly advantageous when in conjunction with electric and hybrid electric vehicles, grid battery storage systems, portable power banks, and the like. Although numerous specific features and various embodiments have been described, it is to be understood that, unless otherwise noted as being mutually exclusive, the various features and embodiments may be combined in various permutations in a particular implementation. Thus, the various embodiments described above are provided by way of illustration only and should not be constructed to limit the scope of the disclosure. Various modifications and changes can be made to the principles and embodiments herein without departing from the scope of the disclosure and without departing from the scope of the claims. 
     Additionally, it is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users.

Metadata:
Filing Date: 20211202
Publication Date: 20240130
Grant Date: 20240130
Priority Date: 20210923
Inventors: Sahoo, Ashish K.
LU, JIE
PIERQUET, BRANDON
PRASAI, ANISH
Assignee: APPLE INC
CPC Classifications: [{"code": "H02M5/2932", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J9/062", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/083", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33584", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/797", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J3/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M5/225", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M5/2932", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/0067", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/23", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/4807", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J3/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J9/062", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/083", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J3/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J9/062", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33584", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/797", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 85573446