Patent Publication Number: US-2023163683-A1

Title: Method and System for Balancing Parallel DC/DC Converters

Description:
TECHNICAL FIELD 
     The present invention relates to a DC/DC converter assembly having multiple DC/DC converters connected in parallel. 
     BACKGROUND 
     A DC/DC converter converts an input DC (direct current) voltage into an output DC voltage. More particularly, a buck DC/DC converter converts an input DC voltage with an input DC current into a lower output DC voltage with a higher output DC current. Conversely, a boost DC/DC converter converts an input DC voltage with an input DC current into a higher output DC voltage with a lower output DC current. 
     A vehicle may have a high-voltage (HV) network, for example a 400 V DC network, and a low-voltage (LV) network, for example a 12 V DC network. A DC/DC converter may be used between the HV and LV networks to connect these two voltage networks together. Consequently, the DC/DC converter may convert a high input DC voltage (e.g., 400 V) of the HV network into a low output DC voltage (e.g., 12 V) for use by loads connected to the LV network. Conversely, assuming the DC/DC converter is bidirectional, the DC/DC converter may convert a low input DC voltage of the LV network into a high output DC voltage for use by loads connected to the HV network. 
     Multiple DC/DC converters may be connected in parallel between the HV network and the LV network such as to provide redundancy, to meet increased current commands of loads, and the like. For example, using two of the same DC/DC converters connected in parallel, the output current is effectively doubled. 
     In certain cases, it is desirable that multiple DC/DC converters connected in parallel provide equal output currents (i.e., share the load equally). As an example of equal output currents, in the case of there being four DC/DC converters, each DC/DC converter is to provide 25% of the total output current. In other cases, it is desirable that multiple DC/DC converters connected in parallel provide different predetermined output currents. As an example of different predetermined output currents, in the case of there being two DC/DC converters, one of the DC/DC converters may be to provide, for instance, 40% (or 45%, 48%, etc.) of the total output current and the other one of the DC/DC converters may be to provide 60% (or 55%, 52%, etc.) of the total output current. 
     However, even apparently identical DC/DC converters will have different output voltages due to instability due to component tolerances due to measurement or to generation. In operation, if one of the DC/DC converters determines that its output voltage is over a target output voltage then this DC/DC converter may decide to reduce its output current, while another one of the DC/DC converters may decide the reverse and act otherwise. This may cause a diverging control and instability. Also, if one of the DC/DC converters generates an output current greater than what another one of the DC/DC converters “expects” (due to tolerances), then this other DC/DC converter may decide to reduce its output current, leading to the first DC/DC converter increasing its output current. Consequently, without requisite adjustment, the output currents of the DC/DC converters will be different than what is desired. 
     SUMMARY 
     An object includes a method and system for balancing output currents of parallel connected DC/DC converters in which each DC/DC converter (i) receives, via a communications line connected between the DC/DC converters such as a CAN bus, the value of the output current of the other DC/DC converter and (ii) uses this value in weighing an output voltage comparison performed by the DC/DC converter for generating the output current of the DC/DC converter to thereby adjust the output current of the DC/DC converter based on this value. 
     In carrying out at least one of the above and/or other objects, a DC/DC converter assembly is provided. The DC/DC converter assembly includes a plurality of DC/DC converters connected in parallel. Each DC/DC converter has a controller. The controllers of the DC/DC converters are in communication with one another via a communications line such as a Controller Area Network (CAN) bus. The controller of each DC/DC converter is configured to transmit to the controller of each other DC/DC converter via the communications line a value of an output current of the DC/DC converter. The controller of each DC/DC converter is configured to control the DC/DC converter to cause the output current of the DC/DC converter to tend toward a desired proportion of the output current of the DC/DC converter to a total output current of all of the DC/DC converters. 
     The desired proportion of the output current of the DC/DC converter to the total output current may be such that each DC/DC converter is to provide equal output currents. The desired proportion of the output current of the DC/DC converter to the total output current may be such that one of the DC/DC converters is to provide a greatest output current and another one of the DC/DC converters is to provide a littlest output current. 
     Further, in carrying out at least one of the above and/or other objects, another DC/DC converter assembly is provided. The DC/DC converter assembly includes first and second DC/DC converters connected in parallel. The first DC/DC converter has a first controller. The second DC/DC converter has a second controller. The first and second controllers are in communication with one another via a communications line such as a CAN bus. The first controller is configured to transmit to the second controller via the communications line a value of an output current of the first DC/DC converter and the second controller is configured to transmit to the first controller via the communications line a value of the output current of the second DC/DC converter. The first controller is configured to control the first DC/DC converter to cause the value of the output current of the first DC/DC converter to tend toward the value of the output current of the second DC/DC converter and the second controller is configured to control the second DC/DC converter to cause the value of the output current of the second DC/DC converter to tend toward the value of the output current of the first DC/DC converter. 
     The first controller may control the first DC/DC converter as a function of a ratio of the value of the output current of the first DC/DC converter to a value of a total output current of the DC/DC converter assembly in causing the value of the output current of the first DC/DC converter to tend toward the value of the output current of the second DC/DC converter. The total output current of the DC/DC converter assembly is a summation of the output current of the first DC/DC converter and the output current of the second DC/DC converter. 
     The second controller may control the second DC/DC converter as a function of a ratio of the value of the output current of the second DC/DC converter to the value of the total output current of the DC/DC converter assembly in causing the value of the output current of the second DC/DC converter to tend toward the value of the output current of the first DC/DC converter. 
     The first controller may control the first DC/DC converter based on a difference between an output voltage of the first DC/DC converter and a target voltage of the DC/DC converter assembly and based on a difference between the output current of the first DC/DC converter and a target output current of the first DC/DC converter for the first DC/DC converter to generate the output current of the first DC/DC converter. 
     In this case, the first controller may weigh the difference between the output voltage of the first DC/DC converter and the target voltage of the DC/DC converter assembly as a function of a ratio of the value of the output current of the first DC/DC converter to a value of a total output current of the DC/DC converter assembly. Further in this case, the first controller may adjust the target output current of the first DC/DC converter based on the weighted difference between the output voltage of the first DC/DC converter and the target voltage of the DC/DC converter assembly. 
     The second controller may control the second DC/DC converter based on a difference between an output voltage of the second DC/DC converter and the target voltage of the DC/DC converter assembly and based on a difference between the output current of the second DC/DC converter and a target output current of the second DC/DC converter for the second DC/DC converter to generate the output current of the second DC/DC converter. 
     In this case, the second controller may weigh the difference between the output voltage of the second DC/DC converter and the target voltage of the DC/DC converter assembly as a function of a ratio of the value of the output current of the second DC/DC converter to a value of a total output current of the DC/DC converter assembly. Further in this case, the second controller may adjust the target output current of the second DC/DC converter based on the weighted difference between the output voltage of the second DC/DC converter and the target voltage of the DC/DC converter assembly. 
     The first DC/DC converter and the second DC/DC converter may be for converting an input voltage with an input current of a traction battery of an electric vehicle into an output voltage with a total output current for charging an auxiliary battery of the electric vehicle. The total output current is a summation of the output current of the first DC/DC converter and the output current of the second DC/DC converter. 
     Also, in carrying out at least one of the above and/or other objects, a method for balancing output currents of parallel connected first and second DC/DC converters of a DC/DC converter assembly is provided. The method includes transmitting from a first controller of the first DC/DC converter to a second controller of the second DC/DC converter, via a communications line, such as a CAN bus, connected between the first controller and the second controller, a value of an output current of the first DC/DC converter. The method further includes transmitting from the second controller to the first controller, via the communications line, a value of the output current of the second DC/DC converter. The method further includes controlling, by the first controller, the first DC/DC converter to cause the value of the output current of the first DC/DC converter to tend toward the value of the output current of the second DC/DC converter. The method further includes controlling, by the second controller, the second DC/DC converter to cause the value of the output current of the second DC/DC converter to tend toward the value of the output current of the first DC/DC converter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a block diagram of a DC/DC converter assembly having parallel-connected first and second DC/DC converters in accordance with embodiments of the present invention, the DC/DC converters being connected in parallel between a high-voltage (HV) network and a low-voltage (LV) network; 
         FIG.  2 A  illustrates a block diagram of the first DC/DC converter of the DC/DC converter assembly; 
         FIG.  2 B  illustrates a flow diagram depicting general operation of the first DC/DC converter; 
         FIG.  3    illustrates two electrical schematic diagrams of alternative connection circuits of the DC/DC converter assembly connected between a HV battery of the HV network and a LV battery of the LV network for the first and second DC/DC converters to redundantly supply the LV battery with electrical energy from the HV battery; 
         FIG.  4    illustrates a block diagram of a background DC/DC converter assembly having parallel-connected master and slave DC/DC converters, the DC/DC converters being connected in parallel between the HV battery and the LV battery; 
         FIG.  5    illustrates another block diagram of the DC/DC converter assembly in accordance with embodiments of the present invention, the block diagram of the DC/DC converter shown in  FIG.  5    being a more detailed version of the block diagram of the DC/DC converter shown in  FIG.  1   ; and 
         FIG.  6    illustrates a flow diagram depicting a control algorithm carried out by each of the first and second DC/DC converters of the DC/DC converter assembly in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the present invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     It is recognized that various electrical devices such as controllers as disclosed herein may include various microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, these electrical devices utilize one or more microprocessors to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed. Further, the various electrical devices as provided herein include a housing and various numbers of microprocessors, integrated circuits, and memory devices ((e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM)) positioned within the housing. The electrical devices also include hardware-based inputs and outputs for receiving and transmitting data, respectively from and to other hardware-based devices as discussed herein. 
     Referring now to  FIG.  1   , a block diagram of a DC/DC converter assembly  10  in accordance with embodiments of the present invention is shown. DC/DC converter assembly  10  has a first DC/DC converter  12   a  and a second DC/DC converter  12   b . First and second DC/DC converters  12   a  and  12   b  are connected in parallel between a high-voltage (HV) network  14  and a low-voltage (LV) network  16  (i.e., the converters are connected in parallel between voltage networks having different voltages from one another). 
     HV network  14  and LV network  16  are set forth as examples of voltage networks in which the voltage of one of the voltage networks (i.e., HV network  14 ) is greater than the voltage of the other one of the voltage networks (i.e., LV network  16 ). As such, HV network  14  may be considered to be a “high-voltage” network in the sense that it has a greater voltage than LV network  16 ; and LV network  16  may be considered to be a “low-voltage” network in the sense that is has a smaller voltage than HV network  14 . In other embodiments, HV network  14  may be considered to be a “high-voltage” network in the sense that its voltage falls within a range defined to be a “high-voltage” range (e.g., 200 to 800 V DC); and LV network  16  may be considered to be a “low-voltage” network in the sense that its voltage falls within a range defined to be a “low-voltage” range (e.g., 5 to 24 V DC). Correspondingly, one of voltage networks  14  and  16  may be a “medium-voltage” network having a voltage falling within a range defined to be a “medium-voltage” range (e.g., 36 to 72 V DC). As such, when the medium-voltage network has a greater voltage than the other voltage network, the medium-voltage network may be considered as being a “high-voltage” network simply due to the fact that it has a greater voltage than the other voltage network; and when the medium-voltage network has a smaller voltage than the other voltage network, the medium-voltage network may be considered as being a “low-voltage” network simply do to the fact that it has a smaller voltage than the other voltage network. 
     DC/DC converter assembly  10  may be “on-board” an electric vehicle (EV) with HV network  14  and LV network  16  being voltage networks of the EV. The terms “electric vehicle” and “EV” herein encompass any type of vehicle which uses electrical power for vehicle propulsion including battery-only electric vehicles (BEV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and the like. 
     A traction battery  18  of the EV is connected to HV network  14 . Traction battery  18  is a high-voltage DC battery that stores electrical energy for powering electric machines of the EV to propel the EV. For instance, traction battery  18  is a 400 V DC battery. 
     An auxiliary battery  20  of the EV is connected to LV network  16 . Auxiliary battery  20  is a low-voltage DC battery that stores electrical energy for powering one or more low-voltage vehicle loads. For instance, auxiliary battery  20  is a 12 V DC battery. 
     In addition to providing electric energy for vehicle propulsion, traction battery  18  provides electrical energy for charging auxiliary battery  20 . In this regard, DC converter assembly  10  is connected between traction battery  18  and auxiliary battery  20  as shown in  FIG.  1   . DC/DC converter assembly  10  converts a high-voltage DC output of traction battery  18  into a low-voltage DC output compatible with auxiliary battery  20 . More particularly, DC/DC converters  12   a  and  12   b  in conjunction with one another convert the HV DC output of traction battery  18  to the LV DC output compatible with auxiliary battery  20 . 
     Referring now to  FIGS.  2 A and  2 B , a block diagram of first DC/DC converter  12   a  of DC/DC converter assembly  10  and a flow diagram  25  depicting general operation of the first DC/DC converter is shown.  FIGS.  2 A and  2 B  depict general configuration and operation of a DC/DC converter. In this case, the depicted DC/DC converter is first DC/DC converter  12   a . First and second DC/DC converters  12   a  and  12   b  may be identical DC/DC converters having different component values due to tolerances. As such, the depictions in  FIGS.  2 A and  2 B  are also representative of second DC/DC converter  12   b . Further, first and second DC/DC converters  12   a  and  12   b  may be different types of DC/DC converters having different power input/output capabilities. Nevertheless, the depiction in  FIGS.  2 A and  2 B  of one of the types of DC/DC converters would also be representative of the other type of DC/DC converter. 
     As shown in  FIG.  2 A , DC/DC converter  12   a  includes a power stage  22  and a controller  24 . As known to those of ordinary skill in the art, as an example of a DC/DC converter layout, power stage  22  includes (not shown) an inverter module, a rectifier module, and a transformer module, the transformer module being connected between the inverter module and the rectifier module. The inverter module is connected to HV network  14  and the rectifier module is connected to LV network  16 . The inverter module includes a high-voltage bridge of power switches. The rectifier module includes a low-voltage bridge of power switches or diodes. The transformer module includes a transformer having a primary side connected to the high-voltage bridge of the inverter module and a secondary side connected to the low-voltage bridge of the rectifier module. 
     Controller  24  of DC/DC converter  12   a  is configured to control the operation of power stage  22  for DC/DC converter  12   a  to convert an input DC voltage (V IN ) with an input DC current (I IN ) into a lower output DC voltage (V OUT ) with a higher output DC current (I OUT ). Particularly, controller  24  controls the power switches of the inverter module, and the power switches of the rectifier module if applicable, to turn on and off at a selected interval rate (i.e., selectively activates/deactivates the power switches) for DC/DC converter  12   a  to convert the input DC voltage with the input DC current into a target output DC voltage with a target output DC current. For instance, controller  24  controls the power switches by providing appropriate pulse-width modulated (PWM) control signals to the power switches. 
     In order to appropriately control the power switches of DC/DC converter  12   a , such as by providing appropriate PWM control signals, controller  24  employs digital processing of measured output voltages and measured output currents of power stage  22 . In this regard, controller  24  receives feedback signals indicative of the measured output voltages and measured output currents of power stage  22  as indicated in  FIG.  2 A . In general, controller  24  compares the measured output voltage and measured output current to the target output voltage and target output current in order to generate the appropriate PWM control signals for controlling the power switches of power stage  22 . 
     Flow diagram  25  of  FIG.  2 B  generally depicts the feedback loop control operation of controller  24 . As described, controller  24  receives sensor signals corresponding to the measured output DC voltage (V OUT ) (“Measured V” or “Measured V OUT ”) and the measured output DC current (I OUT ) (“Measured I” or “Measured I OUT ”) of power stage  22  (i.e., of DC/DC converter  12   a ). The sensor signals are received in the time domain where they are converted into the digital domain by controller  24 , such as by analog-to-digital converters of controller  24 . The target output DC voltage (V OUT ) (“Target V” or “Target V OUT ”) of DC/DC converter  12   a  is known by controller  24 . 
     The control operation of controller  24  includes a first comparator (i.e., an adder)  26  of controller  24  comparing a digital version of the measured output DC voltage with a digital version of the target output DC voltage. First comparator  26  outputs a difference (“voltage error”) signal  28  indicative of a difference between the measured output DC voltage and the target output DC voltage. A first proportional-integral (PI) control module  30  of controller  24  integrates voltage error signal  28  to generate the digital target output DC current (I OUT ) (“Target I” or “Target I OUT ”). 
     A second comparator  32  compares a digital version of the measured output DC current with the digital version of the target output DC current. Second comparator  32  outputs a difference (“current error”) signal  34  indicative of a difference between the measured output DC current and the target output DC current. A second PI control module  36  of controller  24  integrates current error signal  34  to generate a digital DC current (I REF ) command. 
     Controller  24  sets and/or adjusts the manner in which the power switches of power stage  22  are controlled (such as by PWM control of the power switches) based on the DC current command such that the value of the output DC current of power stage  22  tends toward the value of the target output DC current. 
       FIG.  3    illustrates two electrical schematic diagrams  40  and  42  of alternative connection circuits of DC/DC converter assembly  10  connected between a HV battery (e.g., traction battery  18 ) and a LV battery (e.g., auxiliary battery  20 ). First DC/DC converter  12   a  and second DC/DC converter  12   b  are thus able to redundantly supply the LV battery with electrical energy of the HV battery. Output current balancing of first and second DC/DC converters  12   a  and  12   b  at the LV battery is desired to ensure stability. Basically, the two electrical schematic diagrams  40  and  42  in  FIG.  3    are intended to convey that first and second converters  12   a  and  12   b  can operate with different input sources connecting to the same output. 
     Referring now to  FIG.  4   , with continual reference to  FIGS.  1 ,  2 A, and  2 B , a block diagram of a background DC/DC converter assembly  50  having parallel-connected master and slave DC/DC converters is shown. Master (i.e., “first”) DC/DC converter  52  and slave (i.e., “second”) DC/DC converter  54  are connected in parallel between a HV battery (e.g., traction battery  18 ) and a LV battery (e.g., auxiliary battery  20 ). Power stage  22  and controller  24  of each of first DC/DC converter  52  and second DC/DC converter  54  are shown in  FIG.  4   . 
     In operation, controller  24  of first DC/DC converter  52  implements the measured output DC voltage and measured output DC current feedback control loop operation depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of first DC/DC converter  52  to generate an output DC voltage with an output DC current (I OUT_DC/DC_1 ). The output DC current of first DC/DC converter  52  is to be one-half of the total output current of DC/DC converter assembly  50  (i.e., the output DC current of first DC/DC converter  52  and the output DC current of second DC/DC converter  54  are to be the same and their summation is to equal the total output DC current of background DC/DC converter assembly  50 ; I OUT_DC/DC_1 =I OUT_DC/DC_2 ; and I OUT_DC/DC_1 +I OUT_DC/DC_2 =I OUT_Total ). 
     With reference to flow diagram  25  of  FIG.  2 B , the output DC voltage of first DC/DC converter  52  will likely be at least slightly different than the target output DC voltage due to tolerances of components of first DC/DC converter  52 . Further, the output DC voltage of first DC/DC converter  52  will likely be at least slightly different than the output DC voltage of second DC/DC converter  54  due to tolerances of components of second DC/DC converter  54 . In sum, the output DC voltages of first and second DC/DC converters  52  and  54  will likely be different from each other and/or the target output DC voltage. 
     The difference in the output DC voltages has to be accounted in attempting to equalize the output DC currents of first and second DC/DC converters  52  and  54 . Background DC/DC converter assembly  50  attempts to handle this task by (i) making one of the DC/DC converters function as a master (i.e., first DC/DC converter  52 ) and each other DC/DC converter function as a slave (i.e., second DC/DC converter  54 ) and (ii) arranging for controller  24  of first DC/DC converter  52  to provide a control signal indicative of the output DC current of first DC/DC converter  52  to controller  24  of second DC/DC converter  54 . Controllers  24  of DC/DC converters  52  and  54  are connected via a direct connection line  56  for the controller of first DC/DC converter  52  to provide the control signal to the controller of second DC/DC converter  54 . 
     Controller  24  of first DC/DC converter  54  implements the measured output DC current feedback control loop operation (and not the measured output DC voltage feedback control loop operation) depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of first DC/DC converter  52  to generate an output DC voltage with an output DC current (I OUT_DC/DC_2 ). In implementing the measured output DC current feedback control loop operation, the value of the output DC current of first DC/DC converter  52  (provided with the control signal communicated over direct connection line  56  from the controller of first DC/DC converter  52  to the controller of second DC/DC converter  54 ) is used as the value of the target output DC current. 
     A problem is that when DC/DC converters  52  and  54  are separate modules, the synchronization control connection provided by direct connection line  56  is relatively expensive (e.g., requires fast data transfer, has low electromagnetic compatibility, has low robustness, etc.) Further, in case of malfunction of first DC/DC converter  52 , second DC/DC converter  54  will take some milliseconds to start supplying electrical energy as a stand-alone. If there is no auxiliary battery  20  (i.e., LV network  16  having no battery source), then this supply interruption will not be acceptable (e.g., 12 V DC electronic control units (ECUs) of loads in LV network  16  will have too long of an electrical energy supply loss). 
     Referring now to  FIG.  5   , with continual reference to  FIGS.  1 ,  2 A, and  2 B , another block diagram of DC/DC converter assembly  10  in accordance with embodiments of the present invention is shown. The block diagram of DC/DC converter assembly  10  in  FIG.  5    is a more detailed version of the block diagram of DC/DC converter assembly  10  shown in  FIG.  1   . 
     In accordance with embodiments of the present invention, DC converter assembly  10  includes the following attributes. Controller  24  of first DC/DC converter  12   a  implements the measured output DC voltage and measured output DC current feedback control loop operation depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of first DC/DC converter  12   a  to generate an output DC voltage with an output DC current (I OUT_DC/DC_1 ). Likewise, controller  24  of second DC/DC converter  12   b  implements the measured output DC voltage and measured output DC current feedback control loop operation depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of second DC/DC converter  12   b  to generate an output DC voltage with an output DC current (I OUT_DC/DC_2 ). 
     Controller  24  of first DC/DC converter  12   a  and controller  24  of second DC/DC converter  12   b  are connected via a communications line  58  such as a Control Area Network (CAN) bus. The CAN bus is an example as communications line  58  may be embodied as another type of wired (or wireless) communications line. Each of first DC/DC converter  12   a  and second DC/DC converter  12   b  functions as a master DC/DC converter. As being master DC/DC converters, controllers  24  of first and second DC/DC converters  12   a  and  12   b  share output DC current measurements with each other through CAN bus  58 . Particularly, controller  24  of first DC/DC converter  12   a  provides, via CAN bus  58 , a control signal indicative of the output DC current (I OUT_DC/DC_1 ) of first DC/DC converter  12   a  to controller  24  of second DC/DC converter  12   b . Likewise, controller  24  of second DC/DC converter  12   b  provides, via CAN bus  58 , a control signal indicative of the output DC current (I OUT_DC/DC_2 ) of second DC/DC converter  12   b  to controller  24  of first DC/DC converter  12   a.    
     In implementing the control algorithm depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of first DC/DC converter  12   a  to generate the output DC voltage with the output DC current (I OUT_DC/DC_1 ), controller  24  of first DC/DC converter  12   a  determines the total output DC current (I OUT_Total ) of DC/DC converter assembly  10 . The total output DC current (I OUT_Total ) is the summation of the output DC current (I OUT_DC/DC_1 ) of first DC/DC converter  12   a  and the output DC current (I OUT_DC/DC_2 ) of second DC/DC converter  12   b  (i.e., I OUT_Total =I OUT_DC/DC_1 +I OUT_DC/DC_2 ). As described, controller  24  of first DC/DC converter  12   a  measures the output DC current (I OUT_DC/DC_1 ) of first DC/DC converter  12   a ; and controller  24  of first DC/DC converter  12   a  obtains a measurement of the output DC current (I OUT_DC/DC_2 ) of second DC/DC converter  12   b  from the control signal provided via CAN bus  58  from controller  24  of second DC/DC converter  12   b.    
     In turn, controller  24  of first DC/DC converter  12   a  compares the output DC current (I OUT_DC/DC_1 ) of first converter  12   a  with the total output DC current (I OUT_Total ) of DC/DC converter assembly  10  (i.e., I OUT_DC/DC_1 /I OUT_Total ) (for example, at a 50% equal ratio). The difference of the output DC current of first converter  12   a  with the total output DC current against the assigned percentage ratio (phrased herein as “the current ratio” of first converter  12   a ) is fed into the DC/DC power stage control (PWM parameter) of the control algorithm depicted in flow diagram  25  of  FIG.  2 B , as will be described in greater detail with reference to  FIG.  6   . As such, in accordance with embodiments of the present invention, an addition to the control algorithm in flow diagram  25  of  FIG.  2 B  carried out by controller  24  of first DC/DC converter  12   a  includes controller  24  of first DC/DC converter  12   a  using a value of the total output DC current (I OUT_Total ) of DC/DC converter assembly  10 , which is determined from the sharing via CAN bus  58  of the measured output DC current (I OUT_DC/DC_2 ) of second DC/DC converter  12   b  with controller  24  of first DC/DC converter  12   a . As will be described in greater detail with reference to  FIG.  6   , controller  24  of first DC/DC converter  12   a  adjusts the comparison between the measured output DC voltage and the target output DC voltage as a function of the current ratio of first converter  12   a.    
     Likewise, in implementing the control algorithm depicted in flow diagram  25  of  FIG.  2 B  to control power stage  22  of second DC/DC converter  12   b  to generate the output DC voltage with the output DC current (I OUT_DC/DC_2 ), controller  24  of second DC/DC converter  12   b  determines the total output DC current (I OUT_Total ) of DC/DC converter assembly  10 . As described, controller  24  of second DC/DC converter  12   b  measures the output DC current (I OUT_DC/DC_2 ) of second DC/DC converter  12   b ; and controller  24  of second DC/DC converter  12   b  obtains a measurement of the output DC current (I OUT_DC/DC_1 ) of first DC/DC converter  12   a  from the control signal provided via CAN bus  58  from controller  24  of first DC/DC converter  12   a.    
     In turn, controller  24  of second DC/DC converter  12   b  compares the output DC current (I OUT_DC/DC_2 ) of second converter  12   b  with the total output DC current (I OUT_Total ) of DC/DC converter assembly  10  (i.e., I OUT_DC/DC_2 /I OUT_Total ). The difference of the output DC current of second converter  12   b  with the total output DC current against the assigned percentage ratio (phrased herein as “the current ratio” of second converter  12   b ) is fed into the DC/DC power stage control (PWM parameter) of the control algorithm depicted in flow diagram  25  of  FIG.  2 B , as will be described in greater detail with reference to  FIG.  6   . As such, in accordance with embodiments of the present invention, an addition to the control algorithm in flow diagram  25  of  FIG.  2 B  carried out by controller  24  of second DC/DC converter  12   b  includes controller  24  of second DC/DC converter  12   b  using a value of the total output DC current (I OUT_Total ) of DC/DC converter assembly  10 , which is determined from the sharing via CAN bus  58  of the measured output DC current (I OUT_DC/DC_1 ) of first DC/DC converter  12   a  with controller  24  of second DC/DC converter  12   b . As will be described in greater detail with reference to  FIG.  6   , controller  24  of second DC/DC converter  12   b  adjusts the comparison between the measured output DC voltage and the target output DC voltage as a function of the current ratio of second converter  12   b.    
     Referring now to  FIG.  6   , with continual reference to  FIGS.  2 B and  5   , a flow diagram  60  depicting the control algorithm carried out by each of first and second DC/DC converters  12   a  and  12   b  is shown. The control algorithm depicted in flow diagram  60  corresponds to flow diagram  25  in  FIG.  2 B  with the addition of each DC/DC converter further using a value of the total output DC current (I OUT_Total ) of DC/DC converter assembly  10  to determine the “current ratio” of the DC/DC converter and to then adjust (i.e., weigh) the comparison between the measured output DC voltage of the DC/DC converter and the target output DC voltage as a function of the current ratio. 
     In more detail, regarding first DC/DC converter  12   a , first comparator  26  of controller  24  of first DC/DC converter  12   a  compares the measured output DC voltage of first DC/DC converter  12   a , indicated with block  62 , with the target output DC voltage of DC/DC converter assembly  10 , indicated with block  64 . Based on the voltage difference, controller  24  of first DC/DC converter  12   a  generates the target output DC current, indicated with block  66 . As such, the target output DC current is “adjusted” from its previous value based on the voltage difference comparison. In this way, block  66  is labeled “Adjust Value”. Second comparator  32  of first DC/DC converter  12   a  compares the measured output DC current of first DC/DC converter  12   a , indicated with block  68 , with the target output DC current. Based on the current difference, controller  24  of first DC/DC converter  12   a  determines a DC current command and sets and/or adjusts the manner in which the power switches of power stage  22  of first DC/DC converter  12   a  are controlled according to the DC current command such that the value of the output DC current of first DC/DC converter  12   a  tends toward the value of the target output DC current, as indicated with block  70 . 
     As noted, controller  24  of first DC/DC converter  12   a  adjusts the comparison between the measured output DC voltage and the target output DC voltage as a function of the current ratio of first DC/DC converter  12   a . In this regard, after using the value of the output DC current of second DC/DC converter  12   b , obtained via CAN bus  58 , to determine the total output DC current of DC converter assembly  10 , a third comparator  72  of first DC/DC converter  12   a  compares the ratio of the output DC current of first converter  12   a  with the total output DC current of DC/DC converter assembly  10 , indicated in block  74 , with an assigned percentage, such as 50%, indicated in block  76 , to determine the “current ratio” of first DC/DC converter  12   a.    
     Controller  24  adjusts the comparison between the measured output DC voltage and the target output DC voltage as a function of the current ratio, as indicated by block  78 . In this way, the difference of the output DC current of first DC/DC converter  12   a  with the output DC current of second DC/DC converter  12   b  (assuming the assigned percentage is 50%) is fed into the control of power stage  22  of first DC/DC converter  12   a  as a PWM parameter to cause the value of the output DC current of first DC/DC converter  12   a  tend toward the value of the output DC current of second DC/DC converter  12   b  (i.e., tend to equalize the output DC current of first DC/DC converter  12   a  with the output DC current of second DC/DC converter  12   b ). 
     For instance, assume the output DC current of first DC/DC converter  12   a  is greater than the output DC current of second DC/DC converter  12   b  by a given first percentage. In this case, controller  24  adjusts the voltage difference between the measured output DC voltage and the target output DC voltage as a function of the given first percentage such that the target output DC current generated based on the voltage difference is smaller as a function of the given first percentage. Conversely, assume the output DC current of first DC/DC converter  12   a  is less than the output DC current of second DC/DC converter  12   b  by a given second percentage. In this case, controller  24  adjusts the voltage difference between the measured output DC voltage and the target output DC voltage as a function of the given second percentage such that the target output DC current generated based on the voltage difference is larger as a function of the given second percentage. 
     Likewise, second DC/DC converter  12   b  performs the control algorithm of flow diagram  60  depicted in  FIG.  6   . As such, the difference of the output DC current of second DC/DC converter  12   b  with the output DC current of first DC/DC converter  12   a  (assuming the assigned percentage is 50%) is fed into the control of power stage  22  of second DC/DC converter  12   b  as a PWM parameter to cause the value of the output DC current of second DC/DC converter  12   b  tend toward the value of the output DC current of first DC/DC converter  12   a  (i.e., tend to equalize the output DC current of second DC/DC converter  12   b  with the output DC current of first DC/DC converter  12   a ). 
     As described, a method and system for balancing parallel DC/DC converters in accordance with embodiments of the present invention provides an algorithm to share data between two (or more) independent DC/DC converters through a CAN bus and enable the interconnection of the outputs of the DC/DC converter. Pursuant to the algorithm, each DC/DC converter receives the value of the output DC current of the other DC/DC converter through a CAN bus and uses this value in the output DC voltage comparison to adjust the PWM control of the power switches of the DC/DC converter. The method and system solve, with optimized costs, problems associated with parallel DC/DC converter synchronization when these DC/DC converters are in separate units. The method and system find use in electrification DC/DC converters that require redundancy (e.g., two DC/DC converters working in parallel) such as because of high automotive safety integrity level (ASIL) of the supplied functions. 
     The method and system for balancing parallel DC/DC converters in accordance with embodiments of the present invention may include assuring system stability (differences due to tolerances, connection path, etc.); no supply interruption in case of one of a DC/DC converter malfunction; equal reaction in case of operation direction change (HV→LV to LV→HV in the connection circuit shown in electrical schematic diagram  40  of  FIG.  3   ; no high-speed data share through already existing digital bus (CAN) so no extra cost; and in case of 800 V DC batteries with each DC/DC converter connected to one 400 V half (the connection circuit shown in electrical schematic diagram  42  of  FIG.  3   ), the percentage ratio of supplied current may be adjusted (different from 50%) depending on HV-battery halves charge and health status. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the present invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the present invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the present invention.