Patent Publication Number: US-2021167608-A1

Title: Hybrid battery system and method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of the filing date of U.S. Provisional Application No. 62/942,955, filed Dec. 3, 2019, the disclosure of which is incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The utilization of high current density batteries has increased in recent years to support the rising demand for portable smart devices (phones, tablets, laptop computers, etc.), and electric vehicles (both plug-in and hybrid combustion engine). All of these applications presently rely primarily upon Lithium-Ion (“Li-Ion”) battery technology. Li-Ion batteries provide a high current density, but require rather long periods of time to be charged to full capacity. These typical charging times may range from close to an hour (for batteries charged at 1 C rate) to multiple hours (for larger capacity batteries where  1 C charge rate can&#39;t easily be accommodated). 
     Supercapacitors (“SCs”), which are also known as ultracapacitors, offer an alternative to Li-Ion batteries. Typically, SCs offer current densities of only about 25% that of the current densities of a Li-Ion batteries. In other words, an SC would have to occupy approximately four times the volume of a Li-Ion battery to store a given amount of energy. This low-density characteristic makes SCs unsuitable for use as a primary power source in devices having high-current demands (i.e., smart phones, tablets, laptops, electric vehicles, etc.). Rather, SCs are typically utilized in devices that are used sporadically and draw lower peak currents. A portable UPC scanner would be an example of such a device. However, SCs do offer the advantage of very fast recharging in comparison to Li-Ion batteries. This ability to be charged to full, or almost full, capacity in a matter of seconds or a few minutes makes SCs ideal for applications requiring fast energy capture and storage, such as recouping energy from vehicle braking. 
     Known technologies offer hybrid power systems employing both Li-Ion batteries and SCs in a tandem arrangement. These include hybrid Li-Ion/SC energy storage devices that are used as controllers adapted to govern the charging of and power supplied from a combination of Li-Ion batteries and SCs. However, these technologies are ill-suited to meet the needs of compact portable high-current systems that require the ability to attain a stored energy level suitable for device/system operation in a short period of time (seconds or a very few minutes). 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a switching-mode power system and method utilizing a rechargeable primary higher-current density energy cell and a rechargeable secondary lower-current density cell. The system and method employ a collection of switches that are dynamically actuated so as to selectively interconnect and repurpose a minimal arrangement of components. This facilitates the selective provision of power to a portable device or system from a rechargeable primary high-current density energy cell or a rechargeable secondary lower-current density cell. In addition, by selectively actuating the switches, the switching-mode power supply is enabled to a) permit the secondary lower-current density cell to quickly attain a charge level suitable for device/system operation when connected to a charging station/power source, b) charge the primary high-current density energy cell, and c) employ the charged secondary lower-current density cell to charge the primary high-current density energy cell when disconnected from the charging station/power source. This minimizes the period of time a portable device/system must be tethered to a charging station/power source in order to achieve a charge level sufficient for supporting portable operation, and it enables the charging of the primary high-current density cell after the device/system has been disconnected from a charging station/power source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings in which: 
         FIG. 1A  is a schematic diagram illustrating the buck functionality of a switch mode power system. 
         FIG. 1B  is a schematic diagram illustrating the boost functionality of a switch mode power system. 
         FIG. 2A  is a schematic diagram of a preferred embodiment of a hybrid battery system. 
         FIG. 2B  is a schematic diagram illustrating a configuration of the switch-mode power system of  FIG. 1  that enables the charging of the Li-ion battery. 
         FIG. 2C  is a schematic diagram illustrating the configuration of the switch-mode power system of  FIG. 1  that enables the charging of the SC. 
         FIG. 2D  is a schematic diagram illustrating the configuration of the switch-mode power system of  FIG. 1  that enables the discharging of the SC. 
         FIG. 2E  is a schematic diagram illustrating the configuration of the switch-mode power system of  FIG. 1  that enables the discharging of the Li-ion battery. 
         FIG. 2F  is a schematic diagram illustrating the configuration of the switch-mode power system of  FIG. 1A  that enables the enhanced charging of the Li-ion battery. 
     
    
    
     SWITCH MODE POWER SYSTEM OVERVIEW 
     The operation of switch mode power systems, including the modulation of high (buck) and low (boost) switches so as to provide a regulated supply of power, is well-known in the art (see, for example, Switching Power Supply Design, 3rd Edition by Abraham Pressman, Keith Billings and Taylor Morey, Copyright 2009, McGraw-Hill). However, so as to establish a common lexicography, a brief overview of the buck and the boost modes of operation is provided below. 
       FIG. 1A  provides a schematic diagram of a circuit illustrating the buck functionality of a switch mode power system. The circuit consists of high switch (HS)  102 , diode  104 , inductor  106 , capacitor  108  and buck controller  110 . The buck controller  110  has two operating states; one where HS  102  is “on” (and is in a conducting state), and one where HS  102  is “off” (and is in a non-conductive state). The state of the HS  102  is controlled by buck controller  110 , which modulates the state of HS  102  as illustrated by waveform  112 . When the HS  102  is “on”, diode  104  is reverse biased and voltage V SUPPLY  causes current to flow through inductor  106  to a load. This also charges capacitor  108 . The current flow through inductor  106  induces a voltage having an opposite polarity to V SUPPLY , which inhibits the flow of current to the load, until HS  102  is switched off or a steady state is attained. As buck controller  110  causes HS  102  to be placed in an “off” state, V SUPPLY  is disconnected from the circuit, which causes the magnetic field about inductor  106  to collapse thereby inducing a reverse voltage which serves to forward bias diode  104 , and cause energy that had been stored in inductor  106  to dissipate as current through the load. This current flow continues until the energy is fully dissipated or HS  102  is placed back in an “on” state. The output voltage, V LOAD  is therefore determined as a function of the t ON /t OFF  ratio as shown below: 
     
       
         
           
             
               V 
               LOAD 
             
             = 
             
               
                 V 
                 SUPPLY 
               
                
               
                 [ 
                 
                   
                     t 
                     ON 
                   
                   
                     
                       t 
                       ON 
                     
                     + 
                     
                       t 
                       OFF 
                     
                   
                 
                 ] 
               
             
           
         
       
     
     Regulation of V LOAD  is achieved by varying the t ON :t OFF  ratio, with V LOAD  always being less than or equal to V SUPPLY . 
       FIG. 1B  is a schematic of a circuit illustrating the boost functionality of a switch mode power system. The circuit consists of low switch (LS)  114 , diode  116 , inductor  118 , capacitor  120  and boost controller  122 . As shown, LS  114  is situated so as to provide a path to ground when in an “on” state. The state of LS  114  is modulated by boost controller  122  in accordance with waveform  124 . When the LS  114  is “on,” current induced by V SUPPLY  passes through inductor  118  to ground. This also effectively connects the anode of diode  116  to ground, placing the device in a reverse bias state, and allows capacitor  120  to dissipate through the load. If LS  114  is placed in an “off” state, V SUPPLY  is connected to the load via diode  116  (now forward-biased). The current flow through inductor  118  decreases (the path to ground via LS  114  having been removed). As the associated magnetic field about the inductor collapses, the stored energy of inductor  118  is transferred to the load via diode  116 . This effectively adds to V SUPPLY  thereby boosting the V LOAD  to a value greater than V SUPPLY . The value of V LOAD  being a function of: 
     
       
         
           
             
               V 
               LOAD 
             
             = 
             
               
                 V 
                 SUPPLY 
               
               [ 
               
                 1 
                 / 
                 
                   ( 
                   
                     1 
                     - 
                     
                       ( 
                       
                         
                           t 
                           ON 
                         
                         
                           
                             t 
                             ON 
                           
                           + 
                           
                             t 
                             OFF 
                           
                         
                       
                       ) 
                     
                   
                   ] 
                 
               
             
           
         
       
     
     Regulation of V LOAD  is achieved by varying the t ON :t OFF  ratio, with V LOAD  always being greater than or equal to V SUPPLY . 
     DETAILED DESCRIPTION 
       FIG. 2A  is a schematic of a switch-mode power system  200  employing a collection of switches ( 202 ,  204 ,  206 ,  208 ,  210 ,  212 ,  214 , and  216 ) that are dynamically-actuated so as to selectively interconnect and repurpose a minimal arrangement of components. These components include inductors  218  and  220 , resistors  222 ,  224  and  226 , diode  228 , capacitors  230 ,  232  and  234 , field effect transistors  236 ,  238  and  240 , lithium-ion (“Li-ion”) battery  242 , SC  244 , and comparator  246 . In addition, the power system also includes current sensors  248 ,  250  and  252 , voltage sensors  254 ,  256  and  258 , controllers  260 ,  262 ,  264 ,  266 ,  268  and  270 , and temperature sensor  272 . The controllers are subsystems, controlled by one or more processors or dedicated logic systems, and adapted to manage the charging, discharging and regulation of switch mode power systems. The dynamically-actuated switches are labeled as “high” switches (HSx) or “low” switches (LSx). The low switches are configured to selectively connect a voltage to ground, a functionality associated with the boost mode of switch mode power systems. The high switches are configured to selectively connect a voltage to ground, a state functionality associated with the buck mode of switch mode power systems. As is known in the art, regulation within a switch mode power system is achieved through the controlled modulation of the high and low switches. 
       FIG. 2B  shows a configuration of switch-mode power system  200  wherein a path to enable the charging of Li-ion battery  242  is established. Li-ion charge buck controller  260  instructs supply voltage controller  270  to connect V BUS  to the input of switch HS1 ( 204 ). Switches HS1 ( 204 ) and LS1 ( 206 ) are then modulated by Li-ion charge buck controller  260  to regulate the voltage evident at inductor  218  and the current allowed to flow through inductor  218  to the source of p-channel FET  238 . Capacitor  230  serves to smooth the regulated voltage at the source of p-channel FET  238 . Charging controller  268  operates to switch n-channel FET  240  OFF so as to allow V LOAD  voltage to be presented at the negative terminal of comparator  246 . The V LOAD  voltage, when compared to a minimum load voltage, results in a voltage at the output of comparator  246  which drives the gate of p-channel FET  238 . This places p-channel FET  238  in a conductive state, thereby permitting current flow through current-sense resistor  224  and into the positive terminal of Li-ion battery  242 . Throughout the charging process switches HS1 ( 204 ) and LS1 ( 206 ) are controlled by Li-ion charging buck controller in accordance with known switch mode power system conventions so as to maintain an acceptable charging voltage level. The current passing through current sensing resistor  224  is monitored by charging controller  268  during the charging of Li-ion battery  242 . This serves to enable charging controller  268  to monitor and modulate the current flowing through p-channel FET  238  via comparator  246 . The current level is a function of the properties and capacity of Li-ion battery  242 . Charging controller  268  may also receive information from a thermistor or other temperature sensing device  272  positioned to monitor the temperature of Li-ion battery  242 , enabling the power delivered to battery  242  to be modulated as a function of battery temperature. 
       FIG. 2C  illustrates a configuration of switch-mode power system  200  for charging SC  244 . SC charge buck controller  264  instructs supply voltage controller  270  to connect V SC  to the input of HS3 ( 212 ) and instructs SC-Li-ion Charge Boost Controller  262  to place switch HS4 ( 216 ) and FET  236  in an “off” state. Switch  202  is closed and switches HS3 ( 212 ) and LS3/4 ( 214 ) are modulated by SC charge buck controller  264  to regulate the voltage evident at inductor  220  and the current allowed to flow through inductor  220  and switch  202  to positive terminal SC  244 . Capacitor  234  serves to smooth the voltage at the positive terminal of SC  244 . Throughout the charging process switches HS3 ( 212 ) and LS3/4 ( 214 ) are modulated by SC charge buck controller  264  in accordance with known switch mode power system conventions so as to maintain an acceptable charging voltage level. The current flowing from V SC  is monitored by SC charging controller  264  via  270  sensing circuitry during the charging of SC  244 , and the voltage evident at the positive terminal of SC  244  is monitored by SC charge buck controller  264  via voltage sensor  256 . This enables charging controller  264  to monitor and modulate the power flowing into SC  244 . Charging controller  264  may also receive information from a thermistor or other temperature sensing device (connection not illustrated) positioned to monitor the temperature of Li-ion battery  242 , enabling the power delivered to battery  242  to be modulated as a function of that sensed temperature. 
     It is significant that the disclosed invention can simultaneously enable the charging paths depicted in  FIGS. 2B and 2C . This enables the simultaneous charging of both Li-ion battery  242  and SC  244 . Utilizing this dual charging system can simultaneously enable SC  244  to quickly attain a charge level that could be utilized for further charging the Li-ion battery  242  when V BUS  and V SC  are no longer available (such as when a portable device is disconnected from a charging power source). 
       FIG. 2D  shows a configuration of switch-mode power system  200  wherein a path to enable the discharging of SC  244  so as to charge Li-ion battery  242 . Switch  202  is closed, and switch LS3/4 ( 214 ) and HS4 ( 216 ) operate in boost mode, and p-channel FET  236  is placed in a conductive state by SC to Li-ion charge controller  262 . This permits current to flow from SC  244  through inductor  220  and P-channel FET  236 . Charging controller  268  operates to place n-channel FET  240  in a non-conductive state, this enables pull-up resistor  226  as to present a pull-up voltage at the negative terminal of comparator  246 . pull-down the voltage evident at the negative terminal of comparator  246 . This pull-up voltage, when compared to a minimum load voltage, results in a low state at the output of comparator  246  and the gate of p-channel FET  238 . This places p-channel FET  238  in a conductive state, thereby keeping the V LOAD  terminal  274  powered from SC  244  while charging the battery  242 . Throughout the discharge process the voltage at battery  242  and the current flowing through resistor  224  are monitored by charging controller  268 . This enables charging controller  268  to monitor the depletion of SC  244 , and if needed, limit the flow of current to a level appropriate for battery  242 . Charging controller  268  may also receive information from a thermistor or other temperature sensing device  272  positioned to monitor the temperature of Li-ion battery  242 , enabling the power delivered to Li-ion battery  242  from SC  244  to be modulated as a function of that temperature. 
       FIG. 2E  shows a configuration of switch-mode power system  200  wherein a path to enable the discharging of Li-ion battery  242  to a load is established. Switch  202  is closed and switches HS4 ( 216 ) and LS3/4 ( 214 ) are modulated by SC to Li-ion Charge Boost Controller  262  to regulate the voltage evident at inductor  220  and the current allowed to flow through inductor  220 . SC Charge Buck Controller  264  places p-channel FET  236  in a non-conductive state so as to prohibit the flow of current therethrough. Charging controller  268  operates so to keep the n-channel FET  240  in a non-conductive state and to pull-up the voltage evident at the negative terminal of comparator  246 . This pull-up voltage, when compared to a minimum load voltage, results in a low voltage at the output of comparator  246  and the gate of p-channel FET  238 . This places p-channel FET  238  in a conductive state, thereby permitting current flow from the positive terminal of battery  242 , through current-sense resistor  224  and p-channel FET  238  to the V LOAD  output terminal  274 . Throughout the discharge process the voltage at battery  242  and the current flowing through resistor  224  are monitored by charging controller  268 . This enables charging controller  268  to monitor the depletion of battery  242 , and if needed, limit the flow of current to a level appropriate for both battery  242  and the load connected to terminal  274 . 
     The disclosed system is also capable of enabling a configuration that provides for enhanced charging of Li-ion battery  242  (see  FIG. 2F ). This enhanced charging mode utilizes power from both V BUS  and V SC . The path from V SC  to Li-ion battery  242  is highlighted by a dotted line, and the controllers utilized are highlighted with diagonal lines. The path from V BUS  to Li-ion battery  242  is highlighted by a solid line, and the controllers utilized are highlighted with solid shading. 
     To create the charging path fed by V SC , Companion Charge Buck Controller  266  instructs SC charge buck controller  264 , which in turn instructs supply voltage controller  270  to connect V SC  to the input of HS2 ( 208 ). SC charge buck controller  264  opens switch  202 , places p-channel FET  236  into a conductive state and switch HS3 ( 212 ) in an “off” state. Companion Charge Buck Controller  266  then modulates switches HS2 ( 208 ) and LS2 ( 210 ) to regulate the voltage evident at the source of p-channel FET  236  as well as the current allowed to flow through that FET. Capacitor  232  serves to smooth the voltage evident at the source of FET  236 . Current flows through FET  236 , through current-sense resistors  222  and  224  and into the positive terminal of Li-ion battery  242 . The current flowing from V SC  to Li-ion battery  242  is monitored by current sense resistor  222  and current sensor  250 , thereby providing information that is utilized by companion charge buck controller  266  to modulate the power flowing into battery  242 . Companion charge buck controller  266  may also receive information from a thermistor or other temperature sensing device (connection not illustrated) positioned to monitor the temperature of SC  244 , enabling the power delivered to Li-ion battery  242  to be modulated as a function of that sensed temperature. 
     The charging path fed by V BUS  is established by Li-ion charge buck controller  260  instructing supply voltage controller  270  to connect V BUS  to the input of HS1 ( 204 ). Switches HS1 ( 204 ) and LS1 ( 206 ) are then modulated by Li-ion charge buck controller  260  to regulate the voltage evident at inductor  218  and the current allowed to flow through inductor  218  to the source of p-channel FET  238 . Capacitor  230  serves to smooth the regulated voltage at the source of p-channel FET  238 . In case of battery  242  being in the state of requiring application of a pre-charge state (a condition that is typically associate with a battery voltage below 2.8V-3V), charging controller  268  operates to switch n-channel FET  240  so as to pull-down the voltage evident at the negative terminal of comparator  246 . This pull-down voltage, when compared to a minimum load voltage, results in a low voltage at the output of comparator  246  and the gate of p-channel FET  238 . This places p-channel FET  238  is a non-conductive state, thereby isolating the battery  242  from the V LOAD  and charge path from Li-ion Buck Controller  260 . This enables the system to operate as being supplied by the Li-Ion Buck controller  260  charging path while at the same time battery being preconditioned by much smaller current via Companion Charge Buck Controller  266 . Otherwise, if battery  242  is above the ‘pre-charge-state’, controller  268  operates to switch n-channel FET  240  in the OFF state which in turn enables the comparator  246  to operate in either switch or throttling mode permitting current flow through current-sense resistor  224  and into the positive terminal of Li-ion battery  242 . Throughout the charging process switches HS1 ( 204 ) and LS1 ( 206 ) are controlled by Li-ion charging buck controller in accordance with known switch mode power system conventions so as to maintain an acceptable charging voltage level. The current passing through current sensing resistor  224  is monitored by charging controller  268  during the charging of Li-ion battery  242 . This serves to enable charging controller  268  to monitor and modulate the current flowing through p-channel FET  238  via comparator  246 . The current level being a function of the properties and capacity of Li-ion battery  242 . As previously sated, charging controller  268  may also receive information from a thermistor or other temperature sensing device  272  positioned to monitor the temperature of Li-ion battery  242 . This enables the power delivered to Li-ion battery  242  from V BUS  to be modulated as a function of that temperature. 
     The disclosed invention offers many advantages, including the ability to fully charge SC  244  in a very short period of time. This quickly attained “boost charge” can then be utilized to charge Li-ion battery  242  after the device housing the disclosed system is disconnected from a power source (V BUS  and or V SC ). The ability of the disclosed system to utilize a minimal number of components so as to enable the switchable establishment of configurations supporting charging of Li-ion battery  242  and SC  244 , either separately or simultaneously, by an external power source (V BUS  and/or V SC ), the discharging of the Li-ion battery to a load and the discharging of the SC to charge the Li-ion battery makes the system well-suited for portable applications where both space and cost need to be minimized. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. For example, the battery may be Li-ion, Ni metal hydride, or other high-current density power storage technology. The SC may be any cell having a low-current energy density that permits it to be charged in a significantly shorter period than the battery utilized in the system. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.