Abstract:
A system balances current flowing through a solid-state power controller system including at least two output channels connected in parallel. The system delivers a first current to a load via a first output channel to a load, and delivers a second current to the load via a second output channel connected in parallel with the first output channel. The system further determines a first strength of the first current and a second strength of the second current, and adjusts at least one of a first resistance of the first output channel and a second resistance of the second output channel such that the first current strength is substantially equal to the second current strength.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to solid-state power controllers and their components, and more particularly, to balancing parallel solid-state power controller channel currents. 
       BACKGROUND 
       [0002]    Solid-state power controllers (“SSPC”) have been designed to have a current channel that can be used individually or combined with current channels of other SSPCs to achieve a desired current capacity. However when paralleling, the individual channels may experience different conditions such as, for example, in the event that outrush current demands vary or component values including board parasitics vary to a sufficient degree to create a current imbalance or wiring resistance varies from channel to channel. Some channels may become overloaded while other channels may remain within operating specifications. In some instances, this results in possible overloading of one or more circuits, trip coordination complexity, and other factors, such as thermal “hot spots.” 
         [0003]    Conventional SSPC systems designs have attempted to balance the current flowing through the SSPC channels by matching field effect transistor (“FET”) values and/or matching trace line lengths to naturally approximately balance in the current loading between channels. 
       SUMMARY 
       [0004]    According to a non-limiting embodiment, a solid-state power controller system comprises a power source, at least one solid-state power controller, and an electronic controller. The power source includes at least two output channels connected in parallel. The at least two output channels include a first output channel configured to deliver a first current therethrough to a load, and a second output channel configured to deliver a second current therethrough to the load. The second output channel is connected in parallel with the first output channel. The at least one solid-state power controller includes at least one first main control transistor, at least one first electronic balancing device, at least one second main control transistor, and at least one second electronic current balancing device. The at least one first main control transistor is connected in series along the first output channel to control the first current output to the load. The at least one first electronic current balancing device is configured to regulate current delivered to the at least one first main control transistor. The at least one second main control transistor is connected in series along the second output channel to control the second current output to the load. The at least one second electronic current balancing device is configured to regulate current delivered to the at least one second main control transistor. The electronic controller is in electrical communication with the first solid-state power controller and the second solid-state power controller to determine a strength of the first and second currents. The electronic controller further controls at least one of the at least one first electronic current balancing device and the at least one second electronic current balancing device to maintain that the first current flowing through the first channel is substantially equal to the second current flowing through the second channel. 
         [0005]    According to another non-limiting embodiment, a method is provided to balance current flowing through a solid-state power controller system including at least two output channels connected in parallel. The method comprises delivering a first current to a load via a first output channel to a load, and delivering a second current to the load via a second output channel connected in parallel with the first output channel. The method further includes determining a first strength of the first current and a second strength of the second current. The method further includes adjusting at least one of a first resistance of the first output channel and a second resistance of the second output channel such that the first current strength is substantially equal to the second current strength. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The subject matter of the disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features of the various embodiments are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0007]      FIG. 1  illustrates a SSPC system comprising multiple SSPCs coupled in parallel having individual channels in accordance with various embodiments; 
           [0008]      FIG. 2  is a schematic illustrating a multi-channel platform balancing parallel SSPC channel current system including an electronic analog sharing control unit that controls an impedance of a sharing field effect transmitter (FET) to control sharing of an individual AC SSPC according to a non-limiting embodiment; 
           [0009]      FIG. 3  is a schematic illustrating a multi-channel platform balancing parallel SSPC channel current system including an electronic analog sharing control unit that controls an impedance of a sharing field effect transmitter (FET) to control sharing of an individual DC SSPC according to a non-limiting embodiment; 
           [0010]      FIG. 4  is a schematic illustrating a multi-channel platform balancing parallel SSPC channel current system that controls an AC channel, and that includes an electronic digital sharing control unit that selectively enables one or more sharing FETs to balance the system according to a non-limiting embodiment; and 
           [0011]      FIG. 5  is a schematic illustrating a multi-channel platform balancing parallel SSPC channel current system that controls a DC channel, and that includes an electronic digital sharing control unit that selectively enables one or more sharing FETs to balance the system according to a non-limiting embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    According to various embodiments described herein, a multi-channel platform balancing parallel SSPC channel current system is provided. The multi-channel platform balancing parallel SSPC channel current system is configured to operate according to both analog control systems using a single sharing FET operated in a linear mode, for example, and digital control using a plurality of sharing FETs that can be individually enabled via a digital microcontroller, for example. The sharing FETs used for both analog control and digital control can be connected at various locations in series between the source and load. In addition, various embodiments described herein provide a multi-channel platform balancing parallel SSPC channel current system that is configured to operate with either N channel or P channel FETs depending on the optimum configuration to match the local supply and selected supply reference. For example, a multi-channel platform balancing parallel SSPC channel current system is configured to operate either a P-channel sharing FET with a local supply that is negative relative to the feed input (e.g., the main feed power supply) or an N-channel sharing FET with a local supply that is positive relative to the feed input, independently of how or what controls the main SSPC switch that is in series with the sharing FET(s). At least one embodiment also provides a multi-channel platform balancing parallel SSPC channel current system capable of being digitally controlled instead of controlled using a digital-to-analog converter or other type analog control loop. 
         [0013]    Various embodiments of the multi-channel platform balancing parallel SSPC channel current system recited herein provide additional technical features including, for example, allowing both a current sensing device (e.g., a current sensing resistor) and the sharing control functions to remain at low voltage differences with respect to the main feed line. In this manner, the controls can be feed-referenced and can all have low voltage ratings. As a result, only the main switching FET(s) On/Off control has to be level shifted or isolated in order to follow the load voltage when turned On/Off. According to at least one embodiment, a P-channel main FET is provided that is operated according to a DC source only, which allows all control operations to be low voltage control circuits and referenced to the line. Accordingly, this P-type configuration uses negative local supply voltages relative to the main feed line and P channel sharing FET(s). Therefore, when the AC and/or N channel FET(s) are utilized, the gate drive are controlled to be +5V to +10V above the feed input power supply. 
         [0014]    Referring now to  FIG. 1 , a multi-channel platform balancing parallel SSPC system  10  comprising multiple SSPCs that selectively enable respective SSPC channels  3 ,  6 ,  9 ,  12  coupled in parallel is illustrated according to a non-limiting embodiment. Although four channels are shown, it should be appreciated the system is not limited thereto. The multi-channel platform balancing parallel SSPC system  10  comprise a system whereby electrical power is provided for use by a load  4 . Moreover, multi-channel platform balancing parallel SSPC system  10  may condition the electrical power so that its current and voltage remains within defined boundaries and may protect itself, and/or the load  4 , by preventing the current from unwanted deviations. For instance, the multi-channel platform balancing parallel SSPC system  10  may comprise one or more channels, such as channel 1 ( 3 ), channel 2 ( 6 ), channel 3 ( 9 ), channel 4 ( 12 ), coupled in parallel whereby the sensed channel voltage output  8  and/or the channel current output  7  may be controlled. According to a non-limiting embodiment, the parallel connections can be achieved through connections established using an aircraft harness connector. 
         [0015]    In various embodiments and with continued reference to  FIG. 1 , the multi-channel platform balancing parallel SSPC system  10  may comprise a power source  1 , a controller  2 , and SSPCs comprising channel 1 ( 3 ), channel 2 ( 6 ), channel 3 ( 9 ), channel 4 ( 12 ). The power source  1  may provide electrical power via a channel to one or more SSPCs. Each SSPC can then selectively output the power to load  4  in response to receiving a control signal  5  comprising directions generated by controller  2 , and in response to protective actions taken by the SSPC channels both independently and in response to the control signal  5 . 
         [0016]    The power source  1  may comprise any apparatus whereby electrical power may be provided. For example, the power source  1  may be a solid-state power supply. The power source  1  may be a linear power supply, or a switching-mode power supply, or a power supply operating according to a variety of different modes. The power source  1  may further comprise a generator, an alternator, a fuel cell, or another source of electrical energy and in various embodiments may be configured for aircraft use. For example, the power source  1  may comprise a generator mechanically connected with a turbine engine, such as an aircraft engine or an aircraft auxiliary power unit engine. The scalable SSPC systems  10  disclosed herein involve power sources  1  that provide AC channels (see  FIGS. 2 and 4 ), or DC channels (see  FIGS. 3 and 5 ). 
         [0017]    The top level controller  2  may be configured to selectively enable or disable each output channel  3 ,  6 ,  9 ,  12 . The multi-channel platform balancing parallel SSPC system  10  may include a power source  1  comprising a plurality of output channels  3 ,  6 ,  9 , and  12  (also referred to herein as “channels”) comprising a first output channel  3  and a second output channel  6 . It should be appreciated that while  4  channels are shown, any number channels greater than 1 channel may be utilized. 
         [0018]    As mentioned above, the multi-channel platform balancing parallel SSPC system  10  includes a first solid-state power controller  2  that generates a control signal to control the output of one or more of the channels  3 ,  6 ,  9  and  12 . The selective operation may be achieved using one or more main channel transistors. For example, a first main channel transistor may be connected in series with the output of a respective channel  3 ,  6 ,  9  and  12 , as discussed in greater detail below. The multi-channel platform balancing parallel SSPC system  10  may include a second solid-state power controller. A second main channel transistor may be connected to the second solid-state power controller, and may be coupled in series along a second output channel. The multi-channel platform balancing parallel SSPC system  10  may include a controller  2  in electrical communication with the first solid-state power controller and the second solid-state power controller, for example. Accordingly, operation of the first main channel transistor selectively enables and/or disables a respective first channel, e.g., channel  3 , while the second main channel transistor selectively enables and/or disables a respective second channel, e.g., channel  6 . 
         [0019]    According to a non-limiting embodiment, a first channel  3  outputs a first power to a load  4 , a second channel  6  outputs a second power to the load  4 , a third channel  9  outputs a third power to the load  4 , and the fourth channel  12  outputs a fourth power to the load  4 . The electrical power may be combined by the various SSPCs. Each SSPC may receive a corresponding control signal  5  from the controller  2  that selectively enables and/or disables the respective SSPC. For example, the first SSPC may receive a first control signal, the second SSPC may receive a second control signal, the third SSPC may receive a third control signal, and the fourth SSPC may receive a fourth control signal. By controlling each SSPC, the controller  2  may logically combine SSPCs to distribute the amount of current drawn from each channel  3 ,  6 ,  9 , and  12 . A bidirectional communications linkage  5 , may be configured to allow the controller  2  also to receive information, such as the present current load on a channel from the individual channels, such as the first channel  3 , the second channel  6 , the third channel  9 , and/or the fourth channel  12 . The outputs of one or more individual channels may be coupled via a wired linkage  11  to a load  4 . The wire linkage  11  may establish parallel connections of channels  3 ,  6 ,  9  and  12  with respect to one another. Conventional SSPC systems assumed a single SSPC module could not be designed to accommodate different connections provided by different wire linkages  11 . According to at least one embodiment of the present teachings, however, a multi-channel platform balancing parallel SSPC system  10  is provided that is compatible with multiple aircraft applications and different connections established by different wire linkages  11 . 
         [0020]    Further referencing  FIG. 1 , the multi-channel platform balancing parallel SSPC system  10  includes an electronic control sharing control module  14  and one or more electronic current balancing devices  16 . The electronic current balancing devices include, for example, one or more sharing field effect transistors (FETs) as discussed in greater detail below. Each electronic current balancing device  16  is disposed on each channel (e.g.,  3 ,  6 ,  9 ,  12 ) and is configured to realize a varied impedance that controls the overall resistance of the channel in response to a control signal output by the control sharing control module  14 . The control sharing control module  14  generates one or more controls signals that control a respective current balancing device  16  based on a control algorithm, for example, the control algorithm can be one of a variety of schemes including one programmed to direct matching of currents (based on exchange of total or average current of the other parallel channels) or for example act as a limiter to direct a parallel channel not to exceed a locally controlled current and/or time-current curve. Stated another way, the control algorithm may be configured to direct current matching between a first channel e.g., channel  3 , and a second, e.g., channel  6 . According to various embodiments, the control algorithm is configured to utilize the average current of a first current measured over the first channel and a second current measured over the second channel to direct current matching between the plurality of channels, e.g., the first channel  3  and the second channel  6 . While shown as a separate control sharing control module  14 , in various embodiments the sharing control function may also be combined with controller  2 . 
         [0021]    According to various embodiments, the control algorithm may be configured to utilize the total sum of current of a first current measured over a first channel, e.g., channel  3  and a second current measured over a second channel, e.g., channel  6 , to direct current matching between the first output channel, the second output channel and/or any desired number of additional coupled channels. 
         [0022]    Referring now to  FIG. 2 , a SSPC channel  100  including an analog-based current balancing device configured as a sharing FET  102  that provides selective current limiting is illustrated according to a non-limiting embodiment. The sharing FET  102  is illustrated as being connected in parallel with a sharing resistor  103 , but it should be appreciated that the sharing resistor  103  may be omitted. Although only a single SSPC channel is illustrated, e.g., channel  3 , it should be appreciated that channels  6 ,  9  and  12  may be constructed in a similar manner. The SSPC channel  100  comprises an electronic main channel controller  104 , a first main channel transistor  106  and a second main channel transistor  108 . The main channel transistors  106 , 108  may be configured as a p-channel FET, or an n-channel FET. Alternatively, other transistors such as bipolar junction transistors (“BJTs”), whether NPN or PNP, may be implemented, or other voltage-controlled switches or other current-controlled switches may be implemented without departing from the scope of the inventive teachings. 
         [0023]    The main channel controller  104  directs the operation of a gate of the first main channel transistor  106  and a gate of the second main channel transistor  108  via a control algorithm. For example, the main channel controller  104  can generate a command signal  214  and a control loop output signal  216 . In this manner, the gate voltage of the first main channel transistor  106  may be changed in response to the control loop output  216 , while operation of the gate of the second main channel transistor  108  may be directed in response to the command signal  214 . 
         [0024]    According to an embodiment, the SSPC channel  100  may also include one or more measurement or sensing nodes. For example, the SSPC channel  100  may include a sensed channel current output node  7 , a sensed channel voltage output node  8 , and a main transistor voltage sensing node  20 . The sensed channel current output node  7  measures current flowing through a current sense resistor  110 , which is indicative of the current flowing through the SSPC channel  100 . The sensed channel voltage output node  8  measures the voltage across the main power feed and the load  4 , which is indicative of the voltage across the SSPC channel  100 . The main transistor voltage sensing node  20  is connected between the first main channel transistor  106  and the second main channel transistor  108 . 
         [0025]    Various embodiments provide a multi-channel platform balancing parallel SSPC system that allows shared control over an individual SSPC channel  100  that operates in parallel with other SSPC channels (not shown in  FIG. 2 ). In this manner, the local current flowing through the SSPC channel  100  can be assured that SSPC channel-currents coordinate correctly with respective secondary protection (not shown in  FIG. 2 ), thereby promoting thermal balance between the power dissipation of the channels in the group. In addition, the channel-current coordination information can be stored locally as configuration data during module manufacture or configured during power-up sequencing. According to an embodiment, the channel-current coordination information can also be dynamically controlled by an algorithm to track a control parameter or maintain one side of a control parameter during, for example, active limiter operation. 
         [0026]    The sharing FET  102  (in either an analog control embodiment or a digital control embodiment) can be connected at various locations in series between the source and load. For example, the sharing FET  102  can be connected in series between the power source (e.g., power feed), and one or more of the main channel transistors  106 , 108 . According to another embodiment, the electronic current balancing device  102  are connected in series between the load  4 , and one or more of the main channel transistors  106 ,  108 . It should be appreciated that the sharing FET  102  can be located at additional locations including, but not limited to, above the current sense resistor  110 , below the current sense resistor  110 , etc. 
         [0027]    The sharing FET  102  has a gate voltage-to-impedance characteristic. In this manner, the impedance of the sharing FET  102  can be adjusted in response to varying the gate voltage as discussed in greater detail below. A gain feedback sensing node  22  may also be provided between the sharing FET  102  and the first main channel transistor  106 . The gain feedback sensing node  22  measures the effective gain of the sharing FET  102  and feeds the gain information back to the analog control sharing control module  14 . In this manner, analog control sharing control block  14  can monitor the effective gain of the sharing FET  102  and adjust a gate signal  218 , thereby adjusting the resistance of the respective channel  100  (e.g., channel  3 ) so that current flowing through the respective channel  100  is balanced with respect to one or more of the remaining channels (e.g.,  6 ,  9  and  12 ). 
         [0028]    According to a non-limiting embodiment, the sharing FET  102  is controlled via an analog control signal. For example, the analog control sharing control module  14  includes an analog signal driver circuit that generates a pulse-width modulated (PWM) gate signal  218 . The pulse width of the PWM signal  218  varies the impedance of the sharing FET  102 , which in turn controls the overall resistance of the channel  100 . For example, disconnecting the gate signal  218  from the sharing FET  102  disables (i.e., switches off) the sharing FET  102 , and generates a fixed resistance in the channel  100 . When a PWM gate signal  218  is generated by the analog control sharing control module  14  and applied to the gate of the sharing FET  102 , the sharing FET  102  is enabled (i.e., switched on) such that the resistance of the SSPC channel  100  is reduced. As the analog control sharing control module  14  increases the pulse width of PWM gate signal  218 , the sharing FET  102  is driven toward saturation such that the channel  100  realizes the least amount of resistance. The sharing FET may be controlled according to an analog control loop, a DAC, or various other methods of controlling the FET  102 . 
         [0029]    Turning now to  FIG. 3 , a SSPC channel  200  including a digital sharing control module  14 , and a digital-based current balancing device having a plurality of sharing FETs  102   a - 102   c  that provide selective channel resistance is illustrated according to a non-limiting embodiment. The plurality of sharing FETs  102   a - 102   c  are connected in parallel with one another. Although three sharing FETs  102   a - 102   c  are illustrated, any number of sharing FETs  102   n  greater than one sharing FET can be implemented. For instance, each sharing FET  102   a - 102   c  shares a common source and a common drain, while having gates that independently receive a respective gate signal. Unlike the analog-based sharing FET  102  described above, each sharing FETs  102   a - 102   c  is selectively enabled (i.e., switched on) or disabled (i.e., switched off) in response to receiving an independent digital control signal  220   a - 220   c  generated by the digital sharing control module  14 . In this manner, the overall resistance of the SSPC channel  200  decreases as more FETs  102   a - 102   c  are enabled, with least resistance occurring when all the sharing FETs  102   a - 102   c  are enabled. 
         [0030]    According to an embodiment, the digital sharing control module  14  comprises a digital electronic field programmable gate array (FPGA) or any other type of digital logic or digital microcontroller in signal communication with the gates of a respective sharing FETs  102   a - 102   c.  In this manner, the digital sharing control module  14  can generate an active-high signal, for example, to enable a respective sharing FET  102   a - 102   c,  or an active-low signal, for example, to disable a respective sharing FET  102   a - 102   c.    
         [0031]    The SSPC channel  200  may further include a sharing resistor  222  connected in parallel with the plurality of sharing FETs  102 . The sharing resistor  222  defines a fixed max resistance of the SSPC channel  200 . Accordingly, the sharing FETs  102   a - 102   c  can be enabled in various combinations to vary the overall resistance of the SSPC channel  200 . For example, when all the sharing FETs  102  are disabled, the SSPC channel  200  realizes a max fixed resistance defined by the sharing resistor  222 . Turning on one of the sharing FETs (e.g., FET  102   a ), reduces the resistance of the SSPC channel  200 , while enabling all the sharing FETS  102   a - 102   c  provides the least resistance in the SSPC channel  200 . In addition, the sharing FETs  102   a - 102   c  need not be equal in value. In this manner, a larger range of adjustment may be achieved. 
         [0032]    Similar to the SSPC channel  100  discussed above, the SSPC channel  200  including the digital-based current balancing device may include one or more measurement or sensing nodes. For example, the SSPC channel  200  may include a sensed channel current output node  7 , a sensed channel voltage output node  8 , a main transistor voltage sensing node  20 , and a gain feedback sensing node  22 . The sensed channel current output node  7  measures current flowing through a current sense resistor  110 , which is indicative of the current flowing through the SSPC channel  200 . The sensed channel voltage output node  8  measures the voltage across the main power feed and the load  4 , which is indicative of the voltage across the SSPC channel  100 . The main transistor voltage sensing node  20  is connected between the first main channel transistor  106  and the second main channel transistor  108 . 
         [0033]    The gain feedback sensing node  22  may also be provided between the sharing FET  102  and the first main channel transistor  106 . The gain feedback sensing node  22  measures the effective gain of the sharing FET  102  and feeds the gain information back to the digital control sharing control module  14 . In this manner, the digital control sharing control module  14  can monitor the effective gain of the sharing FET  102  and adjust gate signals  220   a - 220   c,  thereby adjusting to resistance of the respective channel  100  (e.g., channel  3 ) so that current flowing the respective channel  100  is balanced with respect to one or more of the remaining channels (e.g.,  6 ,  9  and  12 ). In other words, information necessary to balance the current among all the SSPC channels (e.g.,  3 ,  6 ,  9 ,  12 ) can be dynamically controlled by an algorithm to track a control parameter or stay on one side of a control parameter (active limiter operation). According to another embodiment, the current feedback  7  can also be used to determine if one or more channels are being correctly shared, i.e., to determine whether the current distribution among the channels  3 ,  6 ,  9 ,  12  is correctly balanced. 
         [0034]    According to another embodiment, the gain feedback sensing node  22  can be omitted. In this case, current balance information regarding how local channel current of the SSPC channel  200  correctly coordinates with the SSPC channel&#39;s own secondary protection in order to maintain thermal balance between power dissipation between all the channels (e.g.,  3 ,  6 ,  9 ,  12 ) can be stored locally as configuration data during module manufacturing. In addition, current balance information can be configured during power-up sequencing. 
         [0035]    According to another non-limiting embodiment illustrated in  FIG. 4 , the a SSPC channel  200  can include a digital sharing control module  14 , and a digital-based current balancing device having a plurality of sharing FETs  102   a - 102   c  that provide selective channel resistance is illustrated according to a non-limiting embodiment. The SSPC channel  200  operates similar to the SSPC channel  200  illustrated in  FIG. 3 . In this embodiment, however, a DC SSPC is provided. The DC SSPC may be selectively enabled and/or disabled using a main channel transistor  106  that switched on or off in response to a channel control signal  216  output from electronic main channel controller  104 . 
         [0036]    As used herein, the term module or electronic unit refers to a hardware module including an Application Specific Integrated Circuit (ASIC), for example, an electronic circuit, a computer processor (shared, dedicated, or group) which can execute one or more software or firmware programs, a combinational logic circuit, a FPGA, an electronic microcontroller and/or other suitable components that provide the described functionality stored on electronic memory. In at least one embodiment of the present disclosure, a module may include a microcontroller as understood by those ordinarily skilled in the art. 
         [0037]    While various embodiments have been described in detail in connection with only a limited number of embodiments, it should be readily understood that the features described above are not limited to such disclosed embodiments. Rather, the embodiments can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments have been described, it is to be understood that aspects of the embodiment may include only some of the described embodiments. Accordingly, the described embodiments are not to be seen as limited by the foregoing description.