Patent Publication Number: US-11395385-B2

Title: Current converter circuit for airfield ground lighting

Description:
PRIORITY INFORMATION 
     This Application is a Continuation of U.S. application Ser. No. 16/814,366 filed Mar. 10, 2020, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to methods, devices, and systems for a current converter circuit for airfield ground lighting. 
     BACKGROUND 
     Airfields can include lighting systems to provide visual cues and/or signals for the airfield. For example, airfield lighting systems can include luminaires in order to direct aircraft and/or other vehicles in and/or around the airfield. The airfield lighting systems may, in some instances, be mandated by regulatory bodies such as the International Civil Aviation Organization (ICAO) and/or Federal Aviation Administration (FAA), among other examples. Airfield lighting systems can provide safe and efficient way to regulate airfield traffic. 
     Airfield luminaires can include light emitting diodes (LEDs) as light sources. For example, airfield luminaires can include LEDs in order to provide visual cues and/or signals for aircraft and/or other vehicles in and/or around approach areas, runways, taxiways, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an example of a system for a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. 
         FIG. 2  is an example of a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. 
         FIG. 3  is an example of an airfield ground lighting circuit for a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. 
         FIG. 4  is an example of a flow chart of a method for operating a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Methods, devices, and systems for a current converter circuit for airfield ground lighting are described herein. In some examples, one or more embodiments include a bi-directional switch, an inductor to store energy in response to the bi-directional switch being on, and an output capacitor to discharge power to an LED, where the bi-directional switch can switch off to cause the inductor to discharge to the output capacitor in response to a voltage across the output capacitor being less than a threshold voltage. 
     Airfield luminaires can be located in and/or around an airport surface. As used herein, the term “airfield luminaire” refers to a lighting unit including an electric lamp and associated wiring. For example, airfield luminaires can include an LED light source and can be located around approach ways, mounted in the airport surface on runways, taxiways, intersections, etc. 
     Utilizing LEDs as light sources around in airfield luminaires can allow for a longer operating life and/or lower maintenance for the luminaires relative to previous approaches. For example, LEDs may last longer, be more energy efficient, and/or have to be replaced less frequently than halogen light sources. LEDs can, accordingly, allow for cost savings relative to previous approaches. 
     Airfield luminaires utilizing LED light sources can be solid-state devices and as a result, can be more durable than halogen light sources. However, as a solid-state device, airfield luminaires including an LED light source may include certain operating conditions in order to operate similarly to halogen light sources. For example, since an LED light source airfield luminaire utilizes active switching in the electrical circuit, the power system for the LED light source may become unstable. 
     A current converter circuit for airfield ground lighting, in accordance with the present disclosure, can be utilized to reliably operate LED light sources in an airfield luminaire. The current converter circuit can utilize an inductor and a bi-directional switch to cause the inductor to discharge stored energy to an output capacitor which can provide stable power to the LED across an alternating current (AC) cycle of an AC source. Accordingly, the current converter circuit can provide a near unity input power factor which can be compatible with existing airfield infrastructure, such as source regulators of thyristor and insulated-gate bipolar transistor (IGBT) types, while providing simple and reliable performance in a compact form factor, as compared with previous approaches. 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof. The drawings show by way of illustration how one or more embodiments of the disclosure may be practiced. 
     These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice one or more embodiments of this disclosure. It is to be understood that other embodiments may be utilized and that process, electrical, and/or structural changes may be made without departing from the scope of the present disclosure. 
     As will be appreciated, elements shown in the various embodiments herein can be added, exchanged, combined, and/or eliminated so as to provide a number of additional embodiments of the present disclosure. The proportion and the relative scale of the elements provided in the figures are intended to illustrate the embodiments of the present disclosure and should not be taken in a limiting sense. 
     The figures herein follow a numbering convention in which the first digit or digits correspond to the drawing figure number and the remaining digits identify an element or component in the drawing. Similar elements or components between different figures may be identified by the use of similar digits. For example,  102  may reference element “ 02 ” in  FIG. 1 , and a similar element may be referenced as  202  in  FIG. 2 . 
     As used herein, “a”, “an”, or “a number of” something can refer to one or more such things, while “a plurality of” something can refer to more than one such things. For example, “a number of components” can refer to one or more components, while “a plurality of components” can refer to more than one component. 
       FIG. 1  is an example of a system  100  for a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. The system  100  can include an alternating current (AC) source  102 , an input capacitor  104 , a bi-directional switch  106 , an inductor  108 , an output capacitor  110 , a controller  112 , a light emitting diode (LED) driver  114 , an LED  116 , and diodes  124 . 
     As illustrated in  FIG. 1 , a bi-directional switch  106  can be coupled to inductor  108  and be controlled by controller  112 . As used herein, the term “bi-directional switch” refers to a device that allows a two-way bi-directional flow of current when switched on and blocks a bi-directional flow of current when powered off. For example, the bi-directional switch  106  can allow current to flow bi-directionally through the bi-directional switch  106  when switched on (e.g., by controller  112 ) and block the flow of current through the bi-directional switch  106  when switched off (e.g., by controller  112 ). 
     Although not illustrated in  FIG. 1  for clarity and so as not to obscure embodiments of the present disclosure, the bi-directional switch  106  can include a first metal-oxide-semiconductor field-effect transistor (MOSFET) and a second MOSFET. For example, the bi-directional switch  106  can utilize a first MOSFET and a second MOSFET to allow current to flow bi-directionally through the bi-directional switch  106  when switched on and block the flow of current through the bi-directional switch  106  when switched off, as is further described in connection with  FIG. 2 . 
     Current can be provided to the system  100  by the AC source  102 . As used herein, the term “AC source” refers to an origination point of electrical current in which the direction of the flow of electrons switches back and forth at regular cycles. The AC source  102  can be utilized to power airfield luminaires on an airfield. For example, the LED  116  may be included in an airfield luminaire, and the AC source  102  can provide electrical current to power the LED  116 , as is further described herein. Although not illustrated in  FIG. 1  for clarity and so as not to obscure embodiments of the present disclosure, an AC source regulator can be connected between the AC source  102  and the input capacitor  104  to maintain a constant current in a range of 2.8 amperes (A) to 6.6 A to regulate the light intensity of the LED  116 , as is further described in connection with  FIG. 3 . 
     As used herein, the term “LED” refers to a semiconductor light source that emits light when current flows through it. For example, the LED  116  can be a semiconductor light source included in an airfield luminaire. When current flows through the LED  116 , the LED  116  can emit visible light. The light emitted from the LED  116  can provide visual cues and/or signals for an airfield. 
     As shown in  FIG. 1 , an inductor  108  can be coupled to input capacitor  104 , bi-directional switch  106 , and diodes  124 . As used herein, the term “inductor” refers to an electrical device that stores energy in a magnetic field when current flows through it. For example, the inductor  108  can store energy in response to the bi-directional switch  106  being switched on and current (e.g., from the AC source  102 ) flowing through the inductor  108 . 
     As shown in  FIG. 1 , an output capacitor  110  can be coupled to the didoes  124  and the LED driver  114 . As used herein, the term “capacitor” refers to an electrical device that stores electrical energy in an electric field. The output capacitor  110  can receive energy from the inductor  108  and can discharge stored energy to power the LED  116 , as is further described herein. 
     The system  100  can include a controller  112 . The controller  112  can monitor various characteristics of the current converter circuit and control the operation of various components of the current converter system. For example, the controller  112  can monitor a voltage across the output capacitor  110 . Further, the controller  112  can control the operation of the bi-directional switch  106  and the LED driver  114 . 
     The bi-directional switch  106  can be switched off to cause the inductor  108  to discharge to the output capacitor  110  in response to a voltage across the output capacitor  110  being less than a threshold voltage. For example, the controller  112  can monitor the voltage across the output capacitor  110 . In response to the monitored voltage across the output capacitor  110  being less than a threshold voltage, the controller  112  can switch the bi-directional switch  106  from on (e.g., a state in which the bi-directional switch  106  can allow current to flow bi-directionally through the bi-directional switch  106 ) to off (e.g., a state in which the bi-directional switch  106  can block the flow of current through the bi-directional switch  106 ). As a result of the bi-directional switch  106  switching off, energy stored in the inductor  108  can discharge to the output capacitor  110 . 
     As shown in  FIG. 1 , diodes  124  can be coupled to the inductor  108  and the output capacitor  110 . As used herein, the term “diode” refers to an electrical device that conducts current primarily in one direction. The diodes  124  can include and/or refer to a number of diodes, and can direct the energy discharged from the inductor  108  to the output capacitor  110  based on an input cycle of the AC source  102 , as is further described in connection with  FIG. 2 . 
     The output capacitor  110  can discharge energy to power the LED  116  via the LED driver  114 . As used herein, the term “LED driver” refers to a device that converts higher voltage AC current to lower voltage direct current (DC) to power an LED. For instance, the LED driver  114  can regulate the power provided from the AC source  102  and the current converter circuit to the LED  116  to prevent the LED  116  from being provided power outside of the rated operating parameters for the LED  116 , which can prevent the LED  116  from being damaged or destroyed. 
     The controller  112  can control an intensity of the light emitted by the LED  116  using pulse width modulation (PWM). As used herein, the term “PWM” refers to a method of reducing the average power delivered by an electrical signal by dividing the signal into discrete high and low parts over a particular time interval. For example, the controller  112  can control the intensity of the light emitted by the LED  116  by reducing the power delivered by the LED driver  114  to the LED  116  by varying the high parts of the electrical control signal delivered to the LED driver  114  over a particular time interval. Controlling the intensity of the light output of the LED  116  may be utilized for different category (CAT) operating conditions (e.g., CAT-I, CAT-II or CAT-III) for instrument landing system (ILS) operations at the airfield, among other examples. 
       FIG. 2  is an example of a current converter circuit  220  for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. The current converter circuit  220  can include an AC source  202 , an input capacitor  204 , a bi-directional switch  206 , an inductor  208 , an output capacitor  210 , an LED  216 , and diodes  224 - 1 ,  224 - 2 ,  224 - 3 ,  224 - 4 . The bi-directional switch  206  can include a first metal-oxide-semiconductor field-effect transistor (MOSFET)  222 - 1  and a second MOSFET  222 - 2 . 
     As illustrated in  FIG. 2 , the first MOSFET  222 - 1  can be coupled to the inductor  208  and the diodes  224 - 1  and  224 - 3  and the second MOSFET  222 - 2  can be coupled to the inductor  208  and the diodes  224 - 2  and  224 - 4 . As used herein, the term MOSFET refers to a device which is a type of insulated-gate field-effect transistor used to switch electronic signals in a circuit. For example, the first MOSFET  222 - 1  and the second MOSFET  222 - 2  can be utilized in conjunction with each other to switch the bi-directional switch  206  from on to off and/or vice versa. 
     The first MOSFET  222 - 1  and the second MOSFET  222 - 2  can be connected to the input capacitor  204 . For example, the input capacitor  204  can be connected to a source of the first MOSFET  222 - 1  and a source of the second MOSFET  222 - 2 . 
     The input capacitor  204  can be connected to the AC source  202  and can charge in response to the bi-directional switch  206  being on. The input capacitor  204  can charge to a voltage equivalent to an on-state resistance of the first MOSFET  222 - 1  and a DC resistance of the inductor  208 . The input capacitor  204  can buffer the current converter circuit  220  and maintain a predetermined ripple voltage for the current converter circuit  220 . 
     Although the current converter circuit  220  is illustrated in  FIG. 2  as including a single input capacitor  204 , embodiments of the present disclosure are not so limited. For example, the current converter circuit  220  can include multiple input capacitors  204  (e.g., a bank of input capacitors). 
     The inductor  208  can be connected between the first MOSFET  222 - 1  and the second MOSFET  222 - 2 . For example, the inductor  208  can be connected between a drain of the first MOSFET  222 - 1  and a drain of the second MOSFET  222 - 2 . As a result, the inductor  208  can store energy in response to the bi-directional switch  206  being on. For example, as current flows through the first MOSFET  222 - 1 , the inductor  208 , and the second MOSFET  222 - 2 , the inductor  208  can store energy. 
     The output capacitor  210  can be connected to the inductor  208  and to the LED  216 . Although not illustrated in  FIG. 2  for clarity and so as not to obscure embodiments of the present disclosure, the output capacitor  210  can be connected to the LED  216  via an LED driver. The output capacitor  210  can discharge to power the LED  216 . The inductor  208  can discharge energy to the output capacitor  210 , as is further described herein. 
     Although the current converter circuit  220  is illustrated in  FIG. 2  as including a single output capacitor  210 , embodiments of the present disclosure are not so limited. For example, the current converter circuit  220  can include multiple output capacitors  210  (e.g., a bank of output capacitors) to discharge to power the LED  216 . 
     As illustrated in  FIG. 2 , the current converter  220  can include four diodes  224 . A first diode  224 - 1  can be connected to a drain of the first MOSFET  222 - 1  and the output capacitor  210 . A second diode  224 - 2  can be connected to a drain of the second MOSFET  222 - 2  and the output capacitor  210 . A third diode  224 - 3  can be connected to a source of the first MOSFET  222 - 1 . A fourth diode  224 - 4  can be connected to a source of the second MOSFET  222 - 2 . The current path through the current converter circuit  220  and through the diodes  224  can be based on the cycle of the AC source  202 , as is further described herein. 
     Although not illustrated in  FIG. 2  for clarity and so as not to obscure embodiments of the present disclosure, the current converter circuit  220  can be connected to a controller. The controller can monitor a voltage across the output capacitor  210 . In response to the voltage across the capacitor being less than a threshold voltage, the controller can switch the bi-directional switch  206  to off. 
     As a result of the bi-directional switch  206  being switched off, the inductor  208  can discharge to the output capacitor  210 . The current path from the inductor  208  to the output capacitor  210  can be based on the cycle of the AC source  202 . For example, the particular diodes  224  which direct the current from the inductor  208  discharging can depend on whether the bi-directional switch  206  is switched from on to off while the AC source  202  is in an input positive cycle or an input negative cycle, as is further described herein. 
     As previously described above, the current path through the converter circuit  220  and through the diodes  224  can be based on the cycle of the AC source  202 . During an input positive cycle of the AC source  202  and while the bi-directional switch  206  is on, the current from the AC source  202  can flow from point A (e.g., points on the current converter circuit  220  illustrated in  FIG. 2  surrounded by a circle) to the first MOSFET  222 - 1 , to point B, through the inductor  208  to point C, and back to the AC source  202  at point D. During the input positive cycle of the AC source  202  and while the bi-directional switch  206  is on, the inductor  208  can store energy. 
     In response to the bi-directional switch  206  being switched off (e.g., during the input positive cycle of the AC source  202 ), the inductor  208  can discharge to the output capacitor  210 . In response to the inductor  208  discharging, the second diode  224 - 2  can direct current to the output capacitor  210 , and the third diode  224 - 3  can direct current from the output capacitor  210  to the first MOSFET  222 - 1 . Accordingly, during an input positive cycle of the AC source  202  while the bi-directional switch  206  is switched off, the current can flow from point C (e.g., in response to the inductor  208  discharging) through the second diode  224 - 2  to point E, from point E to the output capacitor  210 , from the output capacitor  210  to point F, and from point F through the third diode  224 - 3  to the first MOSFET  222 - 1 . The current can flow to an internal diode  223 - 1  coupled to the first MOSFET  222 - 1 . 
     During an input negative cycle of the AC source  202  and while the bi-directional switch  206  is on, the current from the AC source  202  can flow from point D to the second MOSFET  222 - 2 , to point C, through the inductor  208  to point B, and back to the AC source  202  at point A. During the input negative cycle of the AC source  202  and while the bi-directional switch  206  is on, the inductor  208  can store energy. 
     In response to the bi-directional switch  206  being switched off (e.g., during the input negative cycle of the AC source  202 ), the inductor  208  can discharge to the output capacitor  210 . In response to the inductor  208  discharging, the first diode  224 - 1  can direct current to the output capacitor  210 , and the fourth diode  224 - 4  can direct current from the output capacitor  210  to the second MOSFET  222 - 2 . Accordingly, during an input negative cycle of the AC source  202  while the bi-directional switch  206  is switched off, the current can flow from point B (e.g., in response to the inductor  208  discharging) through the first diode  224 - 1  to point E, from point E to the output capacitor  210 , from the output capacitor  210  to point F, and from point F through the fourth diode  224 - 4  to the second MOSFET  222 - 2 . The current can flow to an internal diode  223 - 2  coupled to the second MOSFET  222 - 2 . 
       FIG. 3  is an example of an airfield ground lighting circuit  340  for a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. The airfield ground lighting circuit  340  can include an AC mains  352 , a constant current regulator  342 , airfield luminaires  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4 ,  302 -N, and series isolation transformers  344 - 1 ,  344 - 2 ,  344 - 3 ,  344 - 4 ,  344 -N. The constant current regulator  342  can include a power transformer  346 , an input filter  348 , and a feedback control  350 . 
     As illustrated in  FIG. 3 , the airfield ground lighting circuit  340  can include airfield luminaires  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4 ,  302 -N. The airfield luminaires  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4 ,  302 -N can include LEDs which can be utilized to direct aircraft and/or other vehicles in and/or around the airfield. 
     The airfield luminaires  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4 ,  302 -N can be connected to the airfield ground lighting circuit  340  via series isolation transformers  344 - 1 ,  344 - 2 ,  344 - 3 ,  344 - 4 ,  344 -N, respectively. As used herein, the term “series isolation transformer” refers to a device to transfer electrical power from a power source to a load. For example, the series isolation transformers  344 - 1 ,  344 - 2 ,  344 - 3 ,  344 - 4 ,  344 -N can transfer electrical power from an AC mains  352  to each of the airfield luminaires  302 - 1 ,  302 - 2 ,  302 - 3 ,  302 - 4 ,  302 -N, respectively. 
     As illustrated in  FIG. 3 , the airfield ground lighting circuit  340  can be connected to an AC mains  352 . As used herein, the term “AC mains” refers to a power source to provide power to the airfield ground lighting circuit  330 . The AC mains  352  can provide a 50 Hz/60 Hz AC power source in a range of 2.8 A to 6.6 A, although embodiments of the present disclosure are not limited to a 50 Hz/60 Hz AC power source and/or a range of 2.8 A to 6.6 A. 
     The AC mains  352  can provide power to the airfield ground lighting circuit  340  via the constant current regulator  342 . As used herein, the term “constant current regulator” refers to a device to regulate an AC power source. For example, the constant current regulator  342  can regulate current from the AC mains  352  by providing current to the airfield ground lighting circuit  340  in the range of 2.8 A to 6.6 A, as well as provide isolation between the AC mains  342  and the rest of the airfield ground lighting circuit  340  in the event of an electrical power surge. 
     The constant current regulator  342  can include a power transformer  346 . The power transformer  346  can isolate an AC signal (e.g., from the AC mains  352 ) from the airfield ground lighting circuit  340 . 
     The power transformer  346  can be connected to an input filter  348 . The input filter  348  can attenuate rippling that may occur as a result of the operation of the constant current regulator  342 . 
     The constant current regulator  342  can include feedback control  350 . The feedback control  350  can include a controller (not illustrated in  FIG. 3  for clarity and so as not to obscure embodiments of the present disclosure) that can monitor an input current from the AC mains  352  to keep the input voltage and current of the AC signal in phase. 
       FIG. 4  is an example of a flow chart of a method  426  for operating a current converter circuit for airfield ground lighting, in accordance with one or more embodiments of the present disclosure. The method  426  may be performed by a current converter circuit (e.g., current converter circuit  220 , previously described in connection with  FIG. 1 ) and a controller (e.g., controller  112 , previously described in connection with  FIG. 1 ). 
     At  428 , the method  426  can include shunting, by a bi-directional switch including a first MOSFET and a second MOSFET, an input capacitor to provide current to an inductor connected between a drain of the first MOSFET and a drain of the second MOSFET in response to the bi-directional switch being switched on. The input capacitor can be connected to an AC source. Shunting the input capacitor can allow current to flow through the inductor (e.g., while the bi-directional switch is switched on). As a result of current flowing through the inductor, the inductor can store energy. 
     As previously described in connection with  FIG. 2 , the AC source can include an input positive cycle and an input negative cycle. During the input positive cycle, current can be directed from the AC source, through the inductor by the first MOSFET, and back to the AC source. During the input negative cycle, current can be directed from the AC source, through the inductor by the second MOSFET, and back to the AC source. 
     At  430 , the method  426  can include switching, by the bi-directional switch, from on to off in response to a voltage across an output capacitor being less than a threshold voltage. For example, a controller can monitor the voltage across the output capacitor. In response to the voltage across the output capacitor being less than the threshold voltage, the controller can cause the bi-directional switch to switch from on to off. 
     At  432 , the method  426  can include discharging, by the inductor in response to the bi-directional switch being off, energy of the inductor to the output capacitor. As previously described above, the inductor can store energy when the bi-directional switch is switched on. The energy stored by the inductor can be discharged to the output capacitor in response to the bi-directional switch being switched off by the controller and can be directed by diodes of the current converter circuit, as is further described herein. 
     During an input positive cycle of the AC source, the current discharged from the inductor can be directed to the output capacitor by a second diode, and current from the output capacitor can be directed to the first MOSFET by a third diode. During an input negative cycle of the AC source, the current discharged from the inductor can be directed to the output capacitor by a first diode, and current from the output capacitor can be directed to the second MOSFET by a fourth diode. 
     Switching the bi-directional switch can occur at a predetermined switching frequency. For example, the bi-directional switch may be switched at  100  kilohertz (KHz) based on the AC source providing current in a range of 2.8 A to 6.6 A. Such switching allows the inductor to store energy when the bi-directional switch is switched on and allows the stored energy of the inductor to be discharged to the output capacitor when the bi-directional switch is switched off. 
     At  434 , the method  426  can include powering, by a discharge of the output capacitor, an LED in response to the inductor discharging energy to the output capacitor. For example, the output capacitor can provide energy to power the LED such that the LED can emit visible light. The light emitted from the LED can provide visual cues and/or signals for an airfield to direct aircraft and/or other vehicles in and/or around the airfield. 
     A current converter circuit, in accordance with the present disclosure, can be utilized to provide a compact, simple, and reliable way to operate LED light sources in an airfield luminaire located on an airfield. Utilizing an inductor to store energy when a bi-directional switch is switched on allows the stored energy of the inductor to be discharged to the output capacitor when the bi-directional switch is switched off, where the output capacitor can power the LED in the airfield luminaire, which can provide stable power to the LED across an AC cycle of an AC source. 
     Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that any arrangement calculated to achieve the same techniques can be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments of the disclosure. 
     It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. 
     The scope of the various embodiments of the disclosure includes any other applications in which the above structures and methods are used. Therefore, the scope of various embodiments of the disclosure should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled. 
     In the foregoing Detailed Description, various features are grouped together in example embodiments illustrated in the figures for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the embodiments of the disclosure require more features than are expressly recited in each claim. 
     Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.