Patent Publication Number: US-2020303939-A1

Title: Mutliple output charging system and controller

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Under 35 U.S.C. § 119, this application claims priority to, and the benefit of, U.S. provisional patent application No. 62/820,171, entitled “Multiple Output Power Delivery Scheme Using Single Output DC/DC Converter Device” filed on Mar. 18, 2019, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     Charging systems are useful in a variety of applications to provide convenient charging for personal devices, such as smart phones, tablets, laptop computers, etc. Due to the proliferation of battery-operated personal devices, it is desirable to provide charging systems able to charge multiple devices concurrently, for example, in automotive or home applications. Universal serial bus (USB) technology allows DC charging. USB devices are typically designed to operate at a default charging condition with 5 V and 0.5 A. Fast charging implementations, such as USB power delivery (USB-PD) allow power supplies (e.g., sources) and loads (e.g., sinks) to negotiate higher charging voltages and/or charging current levels, such as 3-21 V and 0-5 A. Multiple output or multi-port chargers provide charger ports and corresponding DC voltage supplies (e.g., AC to DC or DC to DC converters) that may adapt voltage and/or current of a given charger port to accommodate sink devices or loads that can operate at different voltages and/or currents, in order to facilitate fast charging. 
     However, such multi-port solutions for concurrently charging n sink devices require one converter per charger port, and each converter must have a sufficient power rating to provide desirable fast charging. This adds to charging system cost, particularly where fewer than n sink devices are typically connected at a given time and/or common charging conditions do not utilize the full power budget of the converter. In addition to cost considerations, certain applications (e.g., portable battery-operated USB chargers, automotive vehicle USB chargers, etc.) have power and size design limitations, where small low-power charging systems are needed. However, multi-port charging systems with n DC to DC converters often have a system power budget below the maximum power of the combined converters, where the total system power budget Ptot&lt;Σ [DC to DC_(1)+DC to DC_(2)+DC to DC_(n)], resulting in poor power and system space utilization. 
     SUMMARY 
     A controller includes a power input terminal, an integer number N power output terminals coupled to the power input terminal, a communications input terminal, and a control output terminal having an integer number M states, where N is greater than 1 and M is greater than 1. The respective power output terminals are adapted to be coupled to respective charging power lines of N charger ports, and the communications input terminal is adapted to be coupled to communications lines of the respective charger ports. The power input terminal is adapted to be coupled to a power output of a converter, and the control output terminal adapted to be coupled to a control input of the converter. 
     In one example, the controller is an integrated circuit. In one example, the controller includes a logic circuit, such as a processor or a state machine, having a communications interface coupled to the communications input terminal, and a voltage select output coupled to the control output terminal. In one example, the controller includes a switch circuit having N switches coupled between the power input terminal and a respective one of the power output terminals, and the logic circuit includes N switch control outputs coupled to control terminals of respective ones of the switches. In one example, the logic circuit is configured to control the state of the control output terminal responsive to a highest common compatible voltage of one or more sink devices coupled to one or more respective ones of the power output terminals. In one implementation, the logic circuit is configured to select the highest common compatible voltage of the one or more sink devices responsive to sink device parameters received in communications signals of the communications input terminal, and a power budget of a converter coupled to the power input terminal. 
     In accordance with further aspects, a controller includes a power input terminal, N power output terminals coupled to the power input terminal, where N is an integer greater than 1, as well as a communications input terminal, a control output terminal, and a logic circuit. The control output terminal has M states, where M is an integer greater than 1. The logic circuit is configured to receive communications signals of the communications input terminal, where the communications signals have sink device parameters of one or more sink devices coupled to one or more respective ones of the power output terminals. The logic circuit is further configured to select a highest common compatible voltage of the sink device parameters according to a power budget of a converter coupled to the power input terminal. The logic circuit is also configured to control the state of the control output terminal according to the selected highest common compatible voltage of the sink device parameters to cause the converter to deliver the selected highest common compatible voltage at the power input terminal. 
     In one example, the logic circuit is configured to control the state of the control output terminal by generating a voltage select signal at the control output terminal, where a state of the generated voltage select signal represents the selected highest common compatible voltage of the sink device parameters. In one implementation, the logic circuit is configured to generate the voltage select signal as a digital signal having a selected one of M states. 
     In one example, the logic circuit includes a processor coupled to a memory, the memory configured to store the sink device parameters and the power budget. In one example, the logic circuit includes a state machine. 
     In one example, the logic circuit is configured to select an updated highest common compatible voltage of the sink device parameters according to the power budget responsive to connection and/or disconnection of one or more sink devices to or from one or more respective ones of the power output terminals. 
     In one example, the controller includes a switch circuit having N switches coupled between the power input terminal and a respective one of the power output terminals, and the logic circuit includes N switch control outputs coupled to control terminals of respective ones of the switches. In one implementation, the logic circuit is configured to generate switching control signals at the switch control outputs to selectively couple the power input terminal to selected ones of the power output terminals to which a sink device is connected. 
     In accordance with another aspect, a charging system includes a converter, a controller, and N charger ports, where N is an integer greater than 1. The converter has a power output, and a control input. The controller has a power input terminal, N power output terminals, a communications input terminal, and a control output terminal. The power input terminal is coupled to the power output of the converter, and the respective power output terminals are coupled to the power input terminal. The control output terminal is adapted to be coupled to a converter, and the control output terminal has M states, where M is an integer greater than 1. The respective charger ports have a charging power line coupled to a respective one of the power output terminals, and a communications line coupled to the communications input terminal. The controller is configured to control the state of the control output terminal to set a voltage of the converter power output according to a selected highest common compatible voltage of one or more sink devices coupled to one or more respective ones of the charger ports. 
     In one example, the controller is configured to receive communications signals of the communications input terminal, where the communications signals have sink device parameters of the sink device or devices. The controller is configured to select the highest common compatible voltage of the sink device parameters according to a power budget of the converter, and generate a voltage select signal at the control output terminal, where a state of the generated voltage select signal represents the selected highest common compatible voltage of the sink device parameters. 
     In one example, the charging system includes a switch circuit having N switches coupled between the power input terminal and a respective one of the power output terminals. In one implementation, the controller includes switch control outputs coupled to the control terminals of respective ones of the switches, and the controller is configured to generate switching control signals at the switch control outputs to selectively couple the power input terminal to selected ones of the power output terminals to which a sink device is connected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a multi-port charging system with a single adjustable converter according to one embodiment. 
         FIG. 2  is a flow diagram of a method to charge one or more sink devices using a single converter according to another embodiment. 
         FIG. 3  is a signal diagram of example signals in the charging system of  FIG. 1 . 
         FIG. 4  is a schematic diagram of a multi-port USB-PD charger with a single adjustable converter according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. Also, the term “couple” or “couples” includes indirect or direct electrical or mechanical connection or combinations thereof. For example, if a first device couples to or is coupled with a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via one or more intervening devices and connections. One or more operational characteristics of various circuits, systems and/or components are hereinafter described in the context of functions which in some cases result from configuration and/or interconnection of various structures when circuitry is powered and operating. 
     Described examples include charging systems and charging controllers that provide a solution in which multiple ports are available for intelligent charging of connected sink devices using a single converter with a DC power output, and the controller sets the DC voltage of the converter according to a highest common compatible voltage of device parameters of the connected sink device parameters, and according to a power budget of the converter. Example solutions can be useful in USB-PD or other charger applications to leverage the functionality of a single output DC to DC, while reducing the size, cost and complexity of multi-port charges that have two or more converters. Moreover, the described solutions facilitate economical choice of converter size and power budget according to expected usage, while accommodating charging when most or all ports are being used. 
       FIG. 1  shows a multi-port charging system  100  (e.g., labeled CHARGER in  FIG. 1 ) for charging one or more battery operated devices. In one example, the charging system  100  is a stand-alone product, such as a portable battery-operated charger for charging one or more USB compatible devices (e.g., referred to as sink devices). In another example, the charging system  100  is integrated into a host device, such as a laptop or desktop computer, an automotive vehicle, an industrial system (not shown). 
     The charging system  100  includes a single converter  101  having a power input  102  adapted to be coupled to a supply  103 . In one example, the converter  101  is an AC to DC converter having a single or multiphase AC input  102  coupled to receive an AC input voltage signal VIN from an AC supply  103 . In another example, the converter  101  is a DC to DC converter having a DC input to receive to receive a DC input voltage signal VIN from the supply  103 . In one implementation, the charging system is a portable multi-port USB charger and the supply  103  is a battery or other DC voltage supply with features for charging the on-board battery from an AC source (not shown). In another example, the charging system  100  is an automotive accessory with multiple USB charging ports accessible from a passenger compartment, and the supply  103  is a 12 V battery. In another example, the charging system  100  is part of an industrial system, and the supply  103  is a 24 V DC source. In one example, the charging system  100  operates from a variety of connectable DC supplies  103 , with output voltages that vary widely (e.g., 3-30 V) and the converter  101  has a wide input voltage range to accommodate coupling the power input  102  to different supplies  103  with different DC output voltages. 
     The converter  101  also includes a power output  104  that provides a DC output voltage signal VO. The converter  101  further includes a control input  105  configured to receive a voltage select signal VSEL. In one example, the control input  105  is adapted to receive an analog voltage or current signal VSEL. In another example, the control input  105  is adapted to receive a single or multi-bit digital signal VSEL. The received voltage select signal VSEL in one example has an integer number of M states, where M is greater than 1. The converter  101  responds to the state of the voltage select signal VSEL to set the voltage VO of the power output  104 . In one example, the converter  101  is configured to provide selectable DC output voltages VO of 0, 5, 9, 12, 15, and 20 V according to the state of the received voltage select signal VSEL (e.g., M=6). 
     The example charging system  100  includes a transformer or inductor circuit  106  coupled to the power output  104  of the converter  101 , as well as a filter circuit  107  coupled to an output of the inductor or transformer circuit  106 . In other examples, one or both of the inductor or transformer circuit  106  and the filter circuit  107  can be omitted. 
     The charging system  100  includes a controller  108 . In one example, the controller  108  is an integrated circuit (IC). The controller  108  includes a power input terminal  109 . The power input terminal  109  is adapted to be coupled to a power output  104  of a converter  101  to receive a DC voltage signal PPHV. In one example, the charging system  100  is or includes a printed circuit board, and the controller  108  includes a conductive IC terminal (e.g., pin, pad, etc.) soldered to a conductive pad of the printed circuit board. In one implementation, the converter  101  is also an integrated circuit with output terminals  104  soldered to the circuit board to form an electrical connection, direct or indirect, to the power input terminal  109  of the controller  108 . The power input terminal  109 , in this regard, can be directly or indirectly coupled to the converter power output  104 , with one or more intervening devices or circuits (e.g., inductor or transformer circuit  106 , filter circuit  107 ) connected therebetween. 
     The controller  108  also includes an integer number of N power output terminals  110 , where N is greater than 1. The respective power output terminals  110  are coupled, directly or indirectly to the power input terminal  109 . The controller  108  has a ground or reference voltage connection terminal  111  coupled to the negative DC output of the converter  101 , directly or through the circuits  106  and  107 . The controller  108  also includes a communications input terminal  112  and a control output terminal  113 . The control output terminal  113  is adapted to be coupled to the control input  105  of the converter  101 , for example, by circuit board connections of a printed circuit board. The control output terminal  113  has M states. 
     The controller  108  also includes a logic circuit  114  with a communications interface coupled to the communications input terminal  112 , and a voltage select output coupled to the control output terminal  113 . In one example, logic circuit  114  includes a processor (e.g., a microprocessor, microcontroller, FPGA, programmable circuit, etc.) coupled to a memory  115 . The memory  115  in one example stores processor-executable program instructions to implement the various charging functions and features detailed herein as well as other functions associated with operating the converter  101 , selectively coupling connected sink devices to the power input terminal  109 , communicating with connected sink devices, etc. In addition, the logic circuit  114  in one example communicates with other external devices, such as a host processor (not shown). The charging system  100  in certain examples includes user interface features, such as a user interface with a display and keyboard or touchscreen features to provide indications to users and to receive user inputs (not shown). In addition, the memory  115  stores parameters associated with charging capabilities of connected sink devices, as well as a power budget associated with the converter  101 . In another example, the logic circuit  114  includes a state machine. The logic circuit  114  communicates with connected sink devices via the communications input terminal  112 . 
     In one example, the controller  108  includes a switch circuit  116  having an integer number of N switches S 1 , S 2 , . . . , SN, where N is greater than 1. The respective switches S 1 , S 2 , . . . , SN include a first terminal coupled to the power input terminal  109 , a second terminal coupled to a respective one of the power output terminals  110 , and a control terminal. The switches in one example are transistors, such as bipolar transistors, field effect transistors (FETs). In other examples, the switches are relays, such as solid-state relays, etc. In this example, the logic circuit  114  includes N switch control outputs  117  coupled to the control terminals of respective ones of the switches S 1 , S 2 , . . . , SN. The logic circuit  114  generates switching control signals SC at the switch control outputs  117  to selectively couple the power input terminal  109  to selected ones of the power output terminals  110 . 
     The charging system  100  includes N charger ports. Only three charger ports  120 ,  130 , and  140  are illustrated in  FIG. 1 . The charger ports  120 ,  130 , and  140  include respective charging power lines  122 ,  132 , and  142  coupled to a respective one of the power output terminals  110 . In one example, the ports  120 ,  130 , and  140  are USB ports with USB compatible connectors that include corresponding charging power lines  122 ,  132 , and  142  to convey respective bus voltage signals VBUS 1 , VBUS 2 , and VBUSN from the corresponding power output terminals  110  of the controller to charge a connected sink device. In addition, the charger ports  120 ,  130 , and  140  include respective communications lines  124 ,  134 , and  144  coupled to the communications input terminal  112 .  FIG. 1  shows one example, in which a first sink device  126  (e.g., smart phone) is connected via a USB cable  128  to the first port  120 , a second sink device  136  is connected via a USB cable  138  to the second port  130 , and a another sink device  146  is connected via a cable  148  to the N th  port  140 . The USB connectors in one example also include a corresponding ground pin (labeled GND in  FIG. 1 ), which are connected to the reference voltage connection terminal  111 . In addition, the example USB connectors of the charging ports  120 ,  130 , and  140  are Type-C plugs that include two configuration channel lines CC 1  and CC 2 , one or both of which are connected to the respective communications lines  124 ,  134 , and  144  (labeled CC in  FIG. 1 ). In one example, the logic circuit  114  includes N communications input terminals  112  as shown in  FIG. 1 . In another implementation, the communications lines  124 ,  134 , and  144  are connected in a single communications line  112 , which is coupled to a communications interface of the logic circuit  114 . 
     In one example, the logic circuit  114  communicates with connected sink devices  126 ,  136 , and  146  as these are coupled to respective ones of the charger ports  120 ,  130 , and  140 . The connected sink devices  126 ,  136 , and  146  report their corresponding sink device parameters  121 ,  131 , and  141 , which are received by the logic circuit  114  in communications signals of the communications input terminal  112 . The logic circuit  114  in one example stores the sink device parameters  121 ,  131 , and  141  in the memory  115 . The memory  115  in one example stores a power budget  150  of the converter  101  that is coupled to the power input terminal  109 . In operation, the logic circuit  114  controls the state of the control output terminal  113  responsive to a highest common compatible voltage of one or more sink devices  126 ,  136 ,  146  coupled to one or more respective ones of the power output terminals  110 . The sink device parameters  121 ,  131 , and  141  specify one or more compatible charging voltages and corresponding compatible current levels at which the corresponding sink devices  126 ,  136 , and  146  can be charged. 
     In the example of  FIG. 1 , the first sink device  126  has parameters  121  stored in the memory  115  that inform the logic circuit  114  that the sink device  126  can be charged at a first voltage V 1  and corresponding first current I 1 , as well as at a second voltage/current pair V 2 /I 2 , etc. The parameters  121  indicate an integer number “i” voltage current pairs including a final i th  pair Vi, Ii) for the sink device  126  coupled to the first charger port  120 . The second connected sink device  136  has parameters  131  stored in the memory  115 , including an integer number “j” voltage/current value pairs V 1 /I 1 , V 2 /I 2 , . . . , Vj/Ij. The final connected sink device  146  has parameters  141  stored in the memory  115 , including an integer number “k” voltage/current value pairs V 1 /I 1 , V 2 /I 2 , . . . , Vk/Ik. The power budget  150  in one example stores M selectable DC output voltage values for the voltage VO of the power output  104  of the converter  101 . In one example, with M=6, the power budget  150  stores values corresponding to selectable DC output voltage values VO=0, 5, 9, 12, 15, and 20 V, as well as corresponding current values or corresponding power values from which the logic circuit  114  determines a maximum charging current available for the M selectable voltages. 
     In operation, the logic circuit  114  controls the state of the control output terminal  113  to set the DC output voltage VO of the power output  104  according to a selected highest common compatible voltage of one or more sink devices  126 ,  136 , and  146  coupled to one or more respective ones of the charger ports  120 ,  130 , and  140 . The converter  101  operates at a selected DC output voltage according to the state of the received voltage select signal VSEL. In one example, the logic circuit  114  selects the highest common compatible voltage of the one or more sink devices  126 ,  136 ,  146  responsive to the sink device parameters  121 ,  131 , and  141  received in communications signals of the communications input terminal  112 , and the power budget  150  of a converter  101 . The logic circuit  114  controls the state of the control output terminal  113  by generating the voltage select signal VSEL having a state that represents the selected highest common compatible voltage of the sink device parameters  121 ,  131 , and  141 . In one example, the logic circuit  114  selects an updated highest common compatible voltage of the sink device parameters  121 ,  131 , and  141  according to the power budget  150  in response to connection of one or more sink devices to one or more respective ones of the power output terminals  110 , or disconnection of one or more sink devices from one or more respective ones of the power output terminals  110 . In this manner, the logic circuit adapts the operation to provide a best charging condition for the currently coupled sink devices. 
     Referring also to  FIGS. 2 and 3 ,  FIG. 2  shows a method  200  for charging one or more sink devices  126 ,  136 ,  146  using a single converter  101 , and  FIG. 3  shows a signal diagram of example signals in the charging system of  FIG. 1  during operation of the logic circuit  114  according to the method  200 . In one implementation, the logic circuit  114  executes program instructions from the memory  115  in order to perform the acts or events of the method  200 . In another implementation, the logic circuit  114  includes a state machine that implements the method  200 . The method  200  as described hereinafter in association with the charging system  100  of  FIG. 1 . The method  200  begins at  202  with power up of the multiport charging system  100 . In one example, the logic circuit  114  monitors the communications input terminal  112  for communications signals from any connected sink device. The logic circuit  114  determines at  204  whether one or more sink devices are coupled to the charger ports. If not (NO at  204 ), the logic circuit  114  continues to monitor the communications input terminal  112  for communications signals indicating coupling of one or more sink devices. 
     Once one or more sink devices are coupled to respective ones of the charger ports (YES at  204 ), the logic circuit  114  adjusts the converter output voltage VO to a default value (e.g., 5 V) at  205 , and the logic circuit  114  determines at  206  whether multiple sink devices are coupled to respective charger ports. If only a single sink device is coupled (NO at  206 ), the logic circuit  114  receives voltage and current capabilities from the connected sink device at  208 , and stores the received sink device parameters (e.g.,  121 ) in the memory  115 . At  210 , the logic circuit  114  of the charging system  100  selects (e.g., evaluates) the highest compatible voltage within the converter power budget  115 . Where only a single sink device is connected, the logic circuit  114  in one example selects the highest compatible voltage from the corresponding connected sink device parameters  121 , and determines whether the corresponding voltage is possible according to the list of M selectable DC output voltages of the power budget  150 . If not, the logic circuit  114  evaluates the next highest voltage, and determines whether that voltage is possible using the converter  101 . Once the logic circuit  114  determines an available charging voltage of the sink device parameters  121 , the logic circuit  114  determines whether the associated charging current of the sink device parameters  121  is within the power budget  150 . If so, the logic circuit  114  selects this as the highest compatible voltage within the converter our budget  150  at  210 . 
     At  212 , logic circuit  114  negotiates with the connected sink device to cause the connected sink device to operate at the selected charging voltage, for example, using communications via the communications input terminal  112 . At  214 , the logic circuit  114  adjusts the converter  101  to the selected voltage. In one example, the logic circuit  114  controls the state of the control output terminal  113  by generating the voltage select signal VSEL having a state that represents the selected highest common compatible voltage at  214  in order to adjust the output voltage VO at the power output  104  of the converter  101 . In one example, at  216  in  FIG. 2 , the logic circuit  114  generates an associated one of the switching control signals SC at the switch control output  117  to selectively couple the power input terminal  109  to a selected one of the power output terminals  110  to which the sink device (e.g.,  126 ) is coupled. 
     The method  200  in this example continues at  218 , where the logic circuit  114  monitors the communications input terminal  112  for communications signals indicating coupling of one or more sink devices to other charger ports, and/or for loss of communications signaling indicating that the currently coupled sink device has been disconnected from the associated charger port. In response to new connection and/or disconnection (YES at  218 ), the method  200  returns to  204  and  206  as described above, where the logic circuit  114  determines whether any sink devices are coupled to the charging system  100  (YES at  204 ), and whether more than one sink devices are coupled to the charging system  100  (YES at  206 ). 
     In response to detection of more than one sink devices being coupled to the charging system  100  (YES at  206 ), the logic circuit  114  receives voltage and current capabilities (e.g., sink device parameters) from all currently coupled sink devices at  220 , and selects (e.g., evaluates) a highest common compatible voltage within the converter power budget  150  at  222 . In one example, the logic circuit  114  determines the highest voltage at  222  that is selectable for operation by the converter  101 , and that is common to all the stored sink device parameters (e.g.,  121 ,  131 , and  141  in the case where three sink devices  126 ,  136 , and  146  are coupled as shown in  FIG. 1 ). In addition, the logic circuit  114  determines at  222  whether the sum of the associated charging current from the sink device parameters at that DC output voltage are within the power budget  150  of the converter  101 . If not, the logic circuit  114  likewise evaluates the next lowest voltage that is selectable for operation of the converter  101  and that is common to all the sink device parameters for currently coupled sink devices. 
     In one example, the converter  101  is selected such that its power budget  150  allows charging of all coupled sink devices (e.g.,  126 ,  136 , . . . ,  146 ) when all the charger ports  120 ,  130 , . . . ,  140  are in use, for example, at the default USB charging voltage of 5 V at 0.5 A. In another example, a smaller converter  101  is used, and the logic circuit  114  selectively implements a priority algorithm to selectively charge less than all coupled sink devices when all the charger ports are used. In one implementation, the logic circuit  114  implements a first in, first out priority algorithm, for example, where one or more most recently connected sink devices is/are temporarily denied charging service (e.g., by the logic circuit  114  opening the associated switch of the switch circuit  116 ) while the earliest connected devices are charged. 
     At  223 , the logic circuit  114  determines whether there is a match that exceeds 5 V. If so (YES at  223 ), the process  200  proceeds to  224 . At  224  in  FIG. 2 , the logic circuit  114  negotiates with the connected sink device to cause the connected sink devices to operate as the selected highest common compatible charging voltage using communications via the communications input terminal  112 . At  226 , the logic circuit  114  adjusts the converter  101  to the selected voltage by generating the voltage select signal VSEL having a state that represents the selected highest common compatible voltage to cause the converter  101  to adjust the output voltage VO at the power output  104 . If there is no match that exceeds 5 V (e.g., NO at  223 ), the charger maintains the default 5 V output voltage VO at the power output  104 . In one example, the logic circuit  114  generates associated ones of the switching control signals SC at the switch control output  117  at  228  to selectively couple the power input terminal  109  to a selected one of the power output terminals  110  to which the sink device (e.g.,  126 ) is coupled. Thereafter, the multi-port charging continues at  218 , and the logic circuit  114  monitors the communications input terminal  112  for communications signals indicating coupling of one or more sink devices to other charger ports, and/or for loss of communications signaling indicating disconnection of one or more currently coupled sink devices from the associated charger ports. 
     In one implementation, the logic circuit  114  generates the voltage select signal VSEL to cause the converter  101  to output a predetermined voltage (e.g., 5 V) during negotiation and evaluation to select and implement the highest common compatible voltage, and the logic circuit  115  activates the associated switch is of the switch circuit  116  by generating the corresponding switching control signals SC at the switch control output  117  to couple the respective charging power lines (e.g.,  122 ,  132 , and/or  142 ) and the corresponding power output terminals  110  to the power input terminal  109  during the negotiation and evaluation operations. 
     In another implementation, the logic circuit  114  generates the switching control signals SC to disconnect all the respective charging power lines and the power output terminals  110  from the power input terminal  109  during negotiation and adjustment of the converter  101  according to the voltage select signal VSEL, and changes the switching control signals SC to selectively couple selected ones of the power output terminals  110  to the power input terminal  109  once the selected charging voltage has been established by the converter  101 . 
       FIG. 3  shows a signal diagram  300  with example curves  310 - 313 ,  321 - 323 , and  331 - 333  that show example signals in the charging system  100  as a function of time during operation of the logic circuit  114  according to the method  200 . The curved  310  shows the DC output voltage VO at the power output  104  of the converter  101 , and the curve  311  shows the bus voltage signal VBUS 1  at the charging power line  122  of the charger port  120 . The curve  312  shows communications signals (CC 1 ) of the communications line  124  of the first charger port  120 , and the curve  313  shows the state (e.g., ON or OFF) of the first switch S 1 . The signal diagram  300  also includes curves  321 - 323  corresponding to the second charger port  130 , including the curve  321  that shows the second bus voltage signal VBUS 2  at the charging power line  132 , the curve  322  that shows communications signals (CC 2 ) of the second communications line  134 , and the curve  323  that shows the on/off state of the second switch S 2 . The curves  331 - 333  correspond to the final charger port  140 , where the curve  331  shows the bus voltage signal VBUSN at the charging power line  142 , the curve  332  shows communications signals (CC 3 ) of the communications line  144 , and the curve  333  shows the on/off state of the switch SN. 
     In the example of  FIG. 3 , no sink devices are coupled to the charging system  100  at time T 0 , and the first sink device  126  is coupled via the cable  128  to the first charger port  120  at a time prior to T 1 . The logic circuit  114  generates the voltage select signal VSEL from T 0  through T 1  to cause the converter  101  to output 0 V from T 0  through T 1 . The logic circuit  114  receives communications from the first sink device  126  (curve  312 ) prior to T 1 . The logic circuit  114  responds by setting the converter voltage (curve  310 ) to 5 V at time T 1 . In this example, the logic circuit  114  also closes the first switch S 1  (curve  313 ) at time T 1 , and the connected sink device  126  begins charging at the default voltage value of 5 V. From T 1  to time T 2  in this example, the logic circuit  114  receives the sink device parameters  121  from the sink device  126 , evaluates the parameters  121  to determine the highest compatible voltage for charging the sink device  126 , referred to as negotiation operation (e.g.,  208 - 216  in  FIG. 2 ). In the illustrated example, the first sink device  126  is capable of charging at 15 V, and the logic circuit  114  determines that this is an available voltage within the capabilities of the converter  101 . At time T 2 , the logic circuit  114  generates the voltage select signal VSEL with a state that causes the converter  101  to output 15 V (curve  310 ), and the switch circuit  116  couples this charging voltage to the charging power line  122  of the charger port  120  (VBUS 1 , curve  311 ). The device  126  charges at 15 V from T 2  to T 3 . 
     After T 2  and before T 3 , the second sink device  136  is coupled via the cable  138  to the second charger port  130 , and the logic circuit  114  receives communications from the sink device  136  (curve  322 ) prior to T 3 . The logic circuit  114  responds by resetting the converter voltage (curve  310 ) to the default 5 V value at time T 3 , and the logic circuit  114  closes the second switch S 2  (curve  323 ) at time T 3  such that the newly connected sink device  136  and the previously coupled sink device  126  charge at the default voltage value of 5 V. Between times T 3  to T 4 , the logic circuit  114  receives the sink device parameters  131  from the newly connected sink device  126 , and evaluates the parameters  121  and  131  to determine the highest common compatible voltage for charging the sink devices  126  and  136  (e.g., negotiation operation at  220 - 228  in  FIG. 2 ). In this example, the second sink device  136  is not capable of 15 V charging, but both devices  126  and  136  can be charged at 12 V, with charging current requirements within the power budget  150  of the converter  101 . By evaluating the sink device parameters  121  and  131 , along with the power budget  150 , the logic circuit  114  selects the highest common compatible voltage of 12 V ( 222  in  FIG. 2 ). At T 4 , the logic circuit  114  negotiates with the connected sink device to cause the coupled devices  126  and  136  to this selected voltage ( 224  in  FIG. 2 ), and generates the voltage select signal VSEL ( 226 ) with a state that causes the converter  101  to output 12 V (curve  310 ). In this configuration, the sink devices  126  and  136  charged at 12 V from T 4  to T 5  in  FIG. 3 . 
     The example continues with the logic circuit  114  receiving communications prior to T 5  from a newly coupled sink device  146 , which has been coupled via the cable  148  to the charger port  140  in  FIG. 1 . At time T 5 , the logic circuit  114  generates the voltage select signal VSEL to reset the converter voltage (curve  310 ) to the default 5 V value, and closes the switch SN (curve  333 ) such that the sink devices  126 ,  136 , and  146  charge at the default voltage value of 5 V from T 5  to T 6 . Between T 5  and T 6 , the logic circuit  114  receives the sink device parameters  141  from the newly connected sink device  146 , and evaluates the parameters  121 ,  131 , and  141  to determine the highest common compatible voltage for concurrently charging the three coupled sink devices  126 ,  136 , and  146  (e.g., negotiation operation at  220 - 228  in  FIG. 2 ). In this example, the sink device  146 , although capable of charging at 12 V, would add excessive charging current requirements that would exceed the power budget  150  of the converter  101 . However, the sink device parameters  121 ,  131 , and  141  indicate that the coupled sink devices  126 ,  136 , and  146  can each accommodate charging at 9 V within the power budget  150  of the converter  101 . 
     The logic circuit  114  selects this voltage as the highest common compatible voltage (e.g.,  222  in  FIG. 2 ). At T 6 , the logic circuit  114  negotiates with the connected sink devices to cause the coupled devices  126 ,  136 , and  146  to the 9 V selected voltage ( 224  in  FIG. 2 ), and generates the voltage select signal VSEL ( 226 ) with a state that causes the converter  101  to output 9 V (curve  310 ). In this configuration, the sink devices  126 ,  136 , and  146  are charged at 9 V from T 6  to T 7  in  FIG. 3 . 
     At T 7  in  FIG. 3 , the logic circuit  114  detects that the first sink device  126  has been disconnected (e.g., decoupled) from the first charger port  120  (e.g., YES at  218  in  FIG. 2 ). In response, the logic circuit  114  turns the first switch S 1  off (curve  313 ) at T 7 , and resets the converter voltage VO to the default value of 5 V. Between T 7  and time T 8 , the logic circuit  114  reevaluates the charger voltage in view of the sink device parameters  131  and  141  of the respective remaining sink devices  136  and  146 . In this example, both the remaining sink devices  136  and  146  can operate at a charger voltage of 15 V within the power budget  150  of the converter  101 , and the logic circuit  114  selects 15 V as the highest common compatible voltage ( 222  in  FIG. 2 ). The logic circuit negotiates with the connected sink devices to cause the connected devices  136  and  146  to charge at this voltage ( 224 ), and generates the voltage select signal VSEL ( 226 ) to adjust the DC output voltage VO of the converter  101  to 15 V at T 8 . The coupled sink devices  136  and  146  charge at 15 V from T 8  to T 9 . 
     Prior to time T 9 , the logic circuit  114  in this example receives communications (curve  312 ) from another sink device (not shown in  FIG. 1 ) that has been coupled to the first charger port  120  between T 8  and T 9 . At T 8 , the logic circuit  114  generates the voltage select signal VSEL to reset the converter voltage (curve  310 ) to the default 5 V value, and closes the switch S 1  (curve  313 ) such that the three coupled sink devices charge at 5 V from T 9  to T 10 . Between T 9  and T 10 , the logic circuit  114  receives the sink device parameters from the newly connected sink device coupled to charger port  120 , and evaluates the sink device parameters of all three coupled sink devices in order to determine the highest common compatible voltage (e.g., negotiation operation at  220 - 228  in  FIG. 2 ). In this example, the newly coupled sink device is not capable of fast charging, and can only charge at 5 V. The logic circuit  114  accordingly selects 5 V ( 222  in  FIG. 2 ) is the highest common compatible voltage. At T 10 , the logic circuit  114  negotiates with the connected sink devices to cause the coupled devices to the 5 V selected voltage ( 224  in  FIG. 2 ), and generates the voltage select signal VSEL ( 226 ) with a state that causes the converter  101  to output 5 V (curve  310 ). In this configuration, the sink devices continue charging at 5 V after T 10  in  FIG. 3 . 
       FIG. 4  shows a multi-port USB-PD implementation of the charging system  100  with a single adjustable converter  101  according to another embodiment. In this example, the charging system  100  includes USB Type C socket connectors  100  that individually have bus voltage (VBUS) terminals, positive and negative data terminals D+ and D−, configuration channel lines CC 1  and CC 2 , and a ground terminal (GND). The converter  101  in this example includes a switching converter circuit  402  that converts AC input power to DC output power, or converts DC input power to DC output power, including the power output terminals  104  as described above. The converter  101  includes a feedback circuit  404  that provides a feedback voltage signal FB to the switching converter circuit  402 . In operation, the switching converter circuit  402  regulates the DC output voltage VO at the power output  104  by comparing the feedback voltage signal FB to an internal reference signal (not shown). The feedback circuit  404  includes a resistive voltage divider circuit formed by an upper feedback resistor and an integer number M lower feedback resistors. The lower feedback resistors in this example are coupled between the upper feedback resistor and the reference voltage connection terminal  111  coupled to the negative DC output of the converter  101 , including switches between the lower feedback resistors and the reference voltage connection terminal  111 . In operation, the logic circuit  114  provides a multi-bit digital voltage select signal VSEL having M control signals to operate individual switches of the feedback circuit  404 . The lower feedback resistors have different values corresponding to feedback voltage signal amplitudes that drive the regulated DC output voltage VO to the designated M values for controlled selection by the logic circuit  114 . 
     The described examples can be applied to portable and integrated USB chargers for home use or integration into automotive or industrial systems, as well as in other charging applications to charge multiple sink devices using a single adjustable AC to DC or DC to DC converter. The described controller sets the DC output voltage of the converter according to the highest common compatible voltage of device parameters of the connected sink device parameters, and according to a power budget of the converter. Example solutions can be useful in USB-PD or other charger applications to leverage the functionality of a single output DC to DC, while reducing the size, cost and complexity of multi-port charges that have two or more converters. In a dual port USB-PD implementation example with a DC to DC converter  101  capable of 3-21 V at 0-6 A, a first sink device connects to Port A and reports its sink capabilities (e.g., 5 V at 3 A; 9 V at 2.3 A; and 20 V at 1 A). The logic circuit  115  and the sink device negotiate a power delivery contract of 20 V at 1 A. Thereafter, a second sink device connects to Port B. The logic circuit  114  communicates using the USB Power Delivery protocol and negotiates with the connected sink device to cause the sink device attached to Port A to 5 V at 3 A. The logic circuit  114  then establishes a connection with the Port B sink device at 5 V at 3 A, and requests the sink device parameters from the sink device coupled to Port B. The second sink device reports capabilities of 5 V at 1.5 A; 9 V at 1.8 A; and 15 V at 1.2 A. The 9 V option is available for both devices. The logic circuit  114  then negotiates ports A and B to 9 V, resulting in the first sink device of Port A establishing a 9 V at 2 A contract and the second device of Port B establishing a 9 V at 1 A contract. Both sink devices are charged from the common DC to DC converter  101  that operates with a DC output voltage VO of 9 V and the total current for port A and port B is below the maximum rating of the source (e.g., 2.3 A+1.8 A=4.1 A&lt;6 A capability of the power budget  150 ). In certain examples, the logic circuit  114  operates within the boundaries of the USB-PD specifications to interrogate multiple USB sink connections and map a voltage and current profile common to all connected sink devices. In accordance with the USB-PD specifications, all sink devices are presumed to be operable for charging at the default value of 5 V. Described examples of the controllers  108  and systems  100  use the USB-PD controller  108  to use a single DC to DC or other converter  101  and establish contracts with all connected USB sink devices without exceeding either the individual capabilities of each sink device or the total power available from the DC to DC converter  101 . 
     Modifications are possible in the described examples, and other implementations are possible, within the scope of the claims.