Dynamic brightness control of light-emitting diode array

Abstract

To provide suitable dynamic brightness control of a light-emitting diode array.SOLUTION: An apparatus includes a light emitting diode (LED) driver circuit, one or more LEDs of an LED array, and an electronic switching circuit. The LED driver circuit is configured to generate a current. The one or more LEDs are electrically connected to the LED driver circuit. The electronic switching circuit is electrically connected to the one or more LEDs and configured to be placed in one of a plurality of switching configurations. The electronic switching circuit is further configured to direct a portion of the current away from the one or more LEDs such that a remaining portion of the current drives the one or more LEDs. The portion of the current corresponds to one of the plurality of switching configurations.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Application No. 62 / 950,324, filed December 19, 2019, which is incorporated by reference in its entirety.

[0002] The present disclosure relates to methods and apparatus for controlling the dynamic brightness of a light emitting diode (LED) array, such as an electronic display or LED lighting system. [Background technology]

[0003] Conventional lighting controller circuits used to drive electronic displays and other lighting systems sometimes provide a relatively narrow range of brightness. A narrow range of brightness can affect the user experience, especially when projecting light under dark ambient light conditions where a lower overall brightness is desired. Furthermore, an electronic display or other lighting system that is too bright can increase power consumption and increase the visibility of optical artifacts. Summary of the Invention [Means for solving the problem]

[0004] Innovative aspects of the subject matter described herein include a method and apparatus for controlling a light emitting diode (LED) array. The apparatus for controlling the LED array includes an LED driver circuit, one or more LEDs of the LED array, and an electronic switching circuit. The LED driver circuit is configured to generate a current. The one or more LEDs are electrically connected to the LED driver circuit. The electronic switching circuit is electrically connected to the one or more LEDs and configured to be placed in one of a plurality of switching configurations. The electronic switching circuit is further configured to direct a portion of the current away from the one or more LEDs such that a remaining portion of the current drives the one or more LEDs. The portion of the current corresponds to one of the plurality of switching configurations.

[0005] Innovative aspects of the subject matter described herein further include a method and apparatus for controlling an LED array. The apparatus for controlling an LED array includes one or more LEDs of the LED array, a first programmable LED driver circuit electrically connected to the one or more LEDs, and a second programmable LED driver circuit electrically connected to the one or more LEDs. The first programmable LED driver circuit is configured to be placed in one of a set of first configurations. The first programmable LED driver circuit is further configured to generate a first current corresponding to one of the set of first configurations. The second programmable LED driver circuit is configured to be placed in a second of the set of second configurations. The second programmable LED driver circuit is further configured to generate a second current corresponding to a second of the set of second configurations. The first current and the second current are combined into a third current to drive one or more LEDs.

[0006] Among other benefits and advantages, the embodiments disclosed herein increase the dynamic brightness range of Red-Green-Blue (RGB) LED arrays compared to conventional methods by reducing the minimum brightness limit of LEDs powered by an LED driver circuit. The embodiments provide an improved user experience for users of RGB displays, especially under low lighting conditions. The embodiments also enable lower power consumption compared to conventional LED controllers by extending the dynamic range of display brightness.

[0007] The details of one or more embodiments of the subject matter described herein are set forth in the accompanying drawings and the description below. Other potential features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. The present specification also provides, for example, the following items: (Item 1) 1. An apparatus for controlling a light emitting diode (LED) array, the apparatus comprising: an LED driver circuit configured to generate a current; one or more LEDs in the LED array, the one or more LEDs being electrically connected to the LED driver circuit; an electronic switching circuit electrically connected to the one or more LEDs, the electronic switching circuit comprising: Installed in one of several switching configurations, directing a portion of the current away from the one or more LEDs such that a remaining portion of the current drives the one or more LEDs, the portion of the current corresponding to one of the plurality of switching configurations. An electronic switching circuit configured to An apparatus comprising: (Item 2) 2. The apparatus of claim 1, wherein each LED of the one or more LEDs has a first brightness in response to being driven by the current, and each LED of the one or more LEDs has a second brightness in response to being driven by a remainder of the current, the second brightness being less than the first brightness. (Item 3) 2. The apparatus of claim 1, wherein a brightness of each of the one or more LEDs varies according to each switching configuration of the plurality of switching configurations. (Item 4) The electronic switching circuit includes: one or more electronic switches configured to place the electronic switching circuitry in one of the plurality of switching configurations; one or more resistors electrically connected to the one or more electronic switches and configured to direct a portion of the current to a port of the LED driver circuit such that a portion of the current from the one or more resistors and a remaining portion of the current driving the one or more LEDs are combined at the port of the LED driver circuit; Item 2. The device according to item 1, comprising: (Item 5) The electronic switching circuit includes: a plurality of electronic switches electrically connected in a first parallel configuration; a plurality of resistors electrically connected in a second parallel configuration, each electronic switch of the plurality of electronic switches electrically connected to a corresponding one or more of the plurality of resistors; Item 2. The device according to item 1, comprising: (Item 6) The electronic switching circuitry comprises N electronic switches, and the plurality of switching configurations are N 2. The apparatus of claim 1, comprising N switching arrangements, N being greater than or equal to 1. (Item 7) Item 1 , wherein the electronic switching circuitry comprises one or more variable resistors. (Item 8) The electronic switching circuit includes: one or more electronic switches; one or more resistors, wherein the one or more LEDs are electrically connected to each other in a series configuration, and each electronic switch of the one or more electronic switches is electrically connected to a corresponding LED of the one or more LEDs and a corresponding resistor of the one or more resistors; Item 2. The device according to item 1, comprising: (Item 9) 2. The apparatus of claim 1, wherein the current is in a range of 20 mA to 400 mA, and the remainder of the current is in a range of 0 mA to 380 mA. (Item 10) 2. The device of claim 1, wherein the one or more LEDs comprise a first LED having a first color and a second LED having a second color, the first color being different from the second color. (Item 11) 1. An apparatus for controlling a light emitting diode (LED) array, the apparatus comprising: one or more LEDs of said LED array; a first programmable LED driver circuit electrically connected to the one or more LEDs, the first programmable LED driver circuit comprising: located in one of a first plurality of configurations; generating a first current corresponding to one of the first plurality of configurations; a first programmable LED driver circuit configured to: a second programmable LED driver circuit electrically connected to the one or more LEDs, the second programmable LED driver circuit comprising: located in a second of the second plurality of configurations; The first current and the second current are combined into a third current to generate a second current corresponding to a second one of the second plurality of configurations to drive the one or more LEDs. a second programmable LED driver circuit configured to: An apparatus comprising: (Item 12) and a controller circuit electrically connected to the first programmable LED driver circuit and the second programmable LED driver circuit, the controller circuit comprising: placing the first programmable LED driver circuit in one of the first plurality of configurations and adjusting the first current; placing the second programmable LED driver circuit in a second one of the second plurality of configurations and adjusting the second current; Item 12. The apparatus of item 11, configured to perform the steps of: (Item 13) Item 12. The apparatus of item 11, wherein each LED of the one or more LEDs has a first minimum brightness in response to being driven by the first current, each LED of the one or more LEDs has a second minimum brightness in response to being driven by the second current, and each LED of the one or more LEDs has a third minimum brightness in response to being driven by the third current, the third minimum brightness equal to the lower of the first minimum brightness and the second minimum brightness. (Item 14) Item 12. The apparatus of item 11, wherein each LED of the one or more LEDs has a first maximum brightness in response to being driven by the first current, each LED of the one or more LEDs has a second maximum brightness in response to being driven by the second current, and each LED of the one or more LEDs has a third maximum brightness in response to being driven by the third current, the third maximum brightness being equal to the greater of the first maximum brightness and the second maximum brightness. (Item 15) Item 12. The apparatus of item 11, wherein a brightness of each LED of the one or more LEDs varies according to each configuration of the first plurality of configurations, and a brightness of each LED of the one or more LEDs varies according to each configuration of the second plurality of configurations. (Item 16) Item 12. The device of item 11, wherein the one or more LEDs comprise a first LED having a first color and a second LED having a second color, the first color being different from the second color. (Item 17) 1. A method for controlling a light emitting diode (LED) array, the method comprising: A current is generated by the LED driver circuit; placing the electronic switching circuitry in one of a plurality of switching configurations with one or more electronic switches; directing, by the electronic switching circuitry, a portion of the current away from one or more LEDs of the LED array such that a remaining portion of the current drives the one or more LEDs, the portion of the current corresponding to one of the plurality of switching configurations; A method comprising: (Item 18) Item 18. The method of item 17, wherein each LED of the one or more LEDs has a first brightness in response to being driven by the current, and each LED of the one or more LEDs has a second brightness in response to being driven by a remainder of the current, the second brightness being less than the first brightness. (Item 19) Item 18. The method of item 17, wherein a brightness of each LED of the one or more LEDs varies according to each switching configuration of the plurality of switching configurations. (Item 20) directing a portion of the current to a port of the LED driver circuit by one or more resistors; combining, by an electrical network, a portion of the current from the one or more resistors and a remaining portion of the current that drives the one or more LEDs at a port of the LED driver circuit; 18. The method of claim 17, further comprising: [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an apparatus for controlling a light emitting diode (LED) array.

[0009] [Diagram 2] FIG. 2 illustrates an apparatus for controlling an LED array.

[0010] [Diagram 3] FIG. 3 illustrates an apparatus for controlling an LED array.

[0011] [Figure 4] FIG. 4 illustrates an apparatus for controlling an LED array.

[0012] [Diagram 5] FIG. 5 illustrates an apparatus for controlling an LED array.

[0013] [Figure 6] FIG. 6 is a flow chart illustrating operations in a method for controlling an LED array.

[0014] [Figure 7] FIG. 7 is a flow chart illustrating operations in a method for controlling an LED array. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Detailed Description FIG. 1 illustrates an apparatus for controlling a light-emitting diode (LED) array. The LED array can be used in electronic displays, such as in devices (e.g., headsets) that provide virtual reality, augmented reality, or mixed reality experiences. The LED array can also be used to provide illumination in aviation lighting systems, automobile headlamps, traffic signals, cameras, medical devices, and / or other suitable systems. The apparatus illustrated in FIG. 1 includes a controller circuit 100, an LED driver circuit 108, one or more LEDs 112 of an LED array, and an electronic switching circuit 128. The LED driver circuit 108 is configured to generate a current 116 to power the one or more LEDs 112. In some embodiments, the current 116 generated by the LED driver circuit 108 is in the range of 20 mA to 400 mA. The amount of current 116 will depend on the type of LED driver circuit 108 used. The one or more LEDs 112 are electrically connected to and powered by the LED driver circuit 108.

[0016] The electronic switching circuit 128 includes an electronic switch 120 and a resistor 124. The electronic switching circuit 128 is electrically connected to the one or more LEDs 112. The electronic switching circuit 128 is configured to be placed in one of a plurality of switching configurations. For example, when the electronic switch 120 is open, the electronic switching circuit 128 is placed in a first switching configuration and the current 116 flows through the one or more LEDs 112, driving the one or more LEDs 112 one at a time. Each LED of the one or more LEDs 112 is connected to a separate pull-down circuit in the LED driver circuit 108. In some embodiments, the controller circuit 100 is configured to generate a control signal 104 that activates only one of the one or more pull-down circuits at a time. Thus, only one of the one or more pull-down circuits is active at a time. Thus, only one of the one or more LEDs 112 is driven at a time.

[0017] When the electronic switch 120 is closed, the electronic switching circuit 128 is placed in a second switching configuration. In the second switching configuration, the electronic switching circuit 128 is configured to direct a portion 132 of the current 116 through the resistor 124 and away from the one or more LEDs 112. A remaining portion 136 of the current 116 drives the one or more LEDs 112. The portion 132 of the current 116 corresponds to the switching configuration in which the electronic switching circuit 128 is placed. For example, in the first switching configuration, the portion 132 is zero. In the second switching configuration, when the electronic switch 120 is closed, the portion 132 corresponds to the voltage drop across the electronic switching circuit 128 divided by the resistance of the resistor 124. In some embodiments, the remaining portion 136 of the current 116 is in the range of 0 mA to 380 mA. Thus, the brightness of each LED 112 is reduced when it is driven by the remainder 136 instead of the current 116 .

[0018] In the device illustrated in FIG. 1 , each LED of the one or more LEDs 112 has a first brightness in response to being driven by the current 116. When the electronic switching circuit 128 is not used, the minimum brightness limit of the LED array corresponds to a minimum limit for the current 116 generated by the LED driver circuit 108. Each LED of the one or more LEDs 112 has a second brightness in response to being driven by the remaining portion 136 of the current 116. When the electronic switching circuit 128 is used, the minimum brightness limit of the LED array corresponds to a minimum limit for the remaining portion 136 of the current 116. The remaining portion 136 of the current 116 is less than the current 116. Thus, the second brightness is less than the first brightness. Thus, when the electronic switching circuit 128 is used, the minimum brightness limit of the LED array is reduced compared to when the electronic switching circuit 128 is not used.

[0019] 2 illustrates an apparatus for controlling an LED array. The apparatus illustrated in FIG. 2 includes an LED driver circuit 200, one or more LEDs 204 of an LED array, and an electronic switching circuit 256. The LED driver circuit 200 is configured to generate a current 208 to power the one or more LEDs 204. The one or more LEDs 204 are electrically connected to and powered by the LED driver circuit 200.

[0020] The electronic switching circuit 256 is electrically connected to one or more LEDs 204. In some embodiments, the electronic switching circuit 256 includes a plurality of electronic switches (216, 220, 224, ..., 228) electrically connected in a first parallel configuration. The electronic switching circuit 256 further includes a plurality of resistors (240, 244, 248, ..., 252) electrically connected in a second parallel configuration. Each electronic switch, e.g., electronic switch 216, is electrically connected to one or more corresponding resistors, e.g., resistor 240.

[0021] The plurality of electronic switches are configured to place the electronic switching circuitry 256 in one of a plurality of switching configurations. The electronic switching circuitry 256 is configured to be placed in a particular switching configuration by closing different combinations of the plurality of electronic switches. In each switching configuration, the electronic switching circuitry 256 directs a portion 212 of the current 208 away from the one or more LEDs 204 such that a remaining portion 260 of the current 208 drives the one or more LEDs 204. The portion 212 of the current 208 corresponds to the switching configuration in which the electronic switching circuitry 256 is placed.

[0022] The resistors (240, 244, 248, ..., 252) are electrically connected to the plurality of electronic switches (216, 220, 224, ..., 228) and configured to direct a portion 212 of the current 208 to a port 236 of the LED driver circuit 200. The portion 212 of the current 208 flowing through one or more of the resistors (240, 244, 248, ..., 252) and a remaining portion 260 of the current 208 driving the one or more LEDs 204 are combined into a current 232 and directed to the port 236 of the LED driver circuit 200.

[0023] In some embodiments, the electronic switching circuitry 256 includes N electronic switches, where N is greater than or equal to 1. For example, N can be 1, 17, 124, etc. The electronic switching circuitry 256 can thus provide two separate switching circuits by closing different combinations of electronic switches. N The current 208 can be placed in one of four switching configurations at a time. For example, consider an embodiment in which N is four. In a first switching configuration, all four electronic switches (216, 220, 224, 228) are open and a portion 212 of the current 208 is zero. In a second switching configuration, the electronic switch 216 is closed and the remaining three electronic switches (220, 224, 228) are open. In a third switching configuration, the electronic switches 216, 220 are closed and the electronic switches 224, 228 are open. In a sixteenth switching configuration, all four electronic switches (216, 220, 224, 228) are closed.

[0024] A portion 212 of the current 208 varies according to a switching configuration in which the electronic switching circuitry 256 is installed. For example, the portion 212 of the current 208 varies according to a resistance of the electronic switching circuitry 256. Thus, a remaining portion 260 of the current 208 varies according to a switching configuration in which the electronic switching circuitry 256 is installed. Because the brightness of each LED of the one or more LEDs 204 varies according to the remaining portion 260 of the current 208, the brightness of each LED varies according to the switching configuration in which the electronic switching circuitry 256 is installed. By closing different combinations of the electronic switches (216, 220, 224, 228), the brightness of the LED array is varied.

[0025] In some embodiments, the electronic switching circuit 256 includes one or more variable resistors. For example, one or more of the resistors (240, 244, 248, ..., 252) can be variable resistors. The resistance of each variable resistor can be adjusted by a controller circuit, such as the controller circuit 100 illustrated in FIG. 1. Thus, the portion 212 of the current 208 can be adjusted by adjusting the resistance in each variable resistor.

[0026] 3 illustrates an apparatus for controlling an LED array. The apparatus illustrated in FIG. 3 includes an LED driver circuit 300, one or more LEDs 312 of an LED array, and an electronic switching circuit 316. The LED driver circuit 300 is configured to generate a current and power the one or more LEDs 312. The one or more LEDs 312 are electrically connected to and powered by the LED driver circuit 300.

[0027] The electronic switching circuit 316 includes one or more electronic switches 304 and one or more resistors 308. The one or more LEDs 312 are electrically connected to each other in a series configuration. Each electronic switch of the one or more electronic switches 304 is electrically connected to a corresponding LED of the one or more LEDs 312 and a corresponding resistor of the one or more resistors 308. When a particular electronic switch of the one or more electronic switches 304 is closed, the electronic switching circuit 316 directs a portion of the current away from the corresponding LED such that the remaining portion of the current drives the corresponding LED. Thus, the brightness of the corresponding LED is reduced compared to the brightness of the corresponding LED when the particular switch is open. Thus, the brightness of the LED array can be varied by closing different combinations of the one or more electronic switches 304.

[0028] FIG. 4 illustrates an apparatus for controlling an LED array. The apparatus illustrated in FIG. 4 includes one or more LEDs 436 of an LED array, a first programmable LED driver circuit 412, a second programmable LED driver circuit 416, and a controller circuit 400. The first programmable LED driver circuit 412 is electrically connected to the one or more LEDs 436 and configured to power the one or more LEDs 436. The first programmable LED driver circuit 412 is configured to be installed in one of a set of first configurations. In each of the set of first configurations, the first programmable LED driver circuit 412 generates a first current 420 to power the one or more LEDs 436. The first current 420 corresponds to the configuration in which the first programmable LED driver circuit 412 is installed. The controller circuit 400 is electrically connected to the first programmable LED driver circuit 412. The controller circuit 400 is configured to place the first programmable LED driver circuit 412 in each of the set of first configurations and adjust the first current 420. For example, the controller circuit 400 generates a control signal 408 that places the first programmable LED driver circuit 412 in each configuration.

[0029] The second programmable LED driver circuit 416 is configured to be placed in a second one of the set of second configurations. In each of the set of second configurations, the second programmable LED driver circuit 416 generates a second current 424 to power one or more LEDs 436. The second current 424 corresponds to the configuration in which the second programmable LED driver circuit 416 is placed. The controller circuit 400 is electrically connected to the second programmable LED driver circuit 416. The controller circuit 400 is configured to place the second programmable LED driver circuit 416 in each of the set of second configurations and adjust the second current 424. For example, the controller circuit 400 generates a control signal 404 that places the second programmable LED driver circuit 416 in each configuration.

[0030] The brightness of each LED of the one or more LEDs 436 varies according to the first current 420. The first current 420 varies according to each configuration of the set of first configurations. Thus, the brightness of each LED of the one or more LEDs 436 varies according to each configuration in which the first programmable LED driver circuit 412 is installed. The brightness of each LED of the one or more LEDs 436 also varies according to the second current 424. The second current 424 varies according to each configuration of the set of second configurations. Thus, the brightness of each LED of the one or more LEDs 436 varies according to each configuration in which the second programmable LED driver circuit 416 is installed. By controlling the configuration in which the first programmable LED driver circuit 412 and the second programmable LED driver circuit 416 are installed using the controller circuit 400, the brightness of the LED array can be adjusted.

[0031] The first current 420 and the second current 424 are combined into a third current 428 to drive one or more LEDs 436. For example, the first current 420 can be in a range of 1 mA to 50 mA. The second current 424 can be in a range of 50 mA to 500 mA. The third current 428 can be in a range of 1 mA to 550 mA. Each LED of the one or more LEDs 426 has a first minimum brightness in response to being driven by the first current 420 (e.g., 1 mA). Each LED of the one or more LEDs 436 has a second minimum brightness in response to being driven by the second current 424 (e.g., 50 mA). Each LED of the one or more LEDs 436 has a third minimum brightness in response to being driven by the third current 428 (e.g., 1 mA). The third minimum color value is the lower of the first minimum color value and the second minimum color value.

[0032] Each LED of the one or more LEDs 436 has a first maximum brightness in response to being driven by a first current 420 (e.g., 50 mA). Each LED of the one or more LEDs 436 has a second maximum brightness in response to being driven by a second current 424 (e.g., 500 mA). Each LED of the one or more LEDs 436 has a third maximum brightness in response to being driven by a third current 428 (e.g., 550 mA). The third maximum brightness is the higher of the first maximum brightness and the second maximum brightness.

[0033] The one or more LEDs include at least a first LED having a first color (e.g., red) and a second LED having a second color (e.g., green). The first color is different from the second color. One or more blue LEDs can also be used to construct an LED array. In some embodiments, the controller circuit 400 programs at least one of the first programmable LED driver circuit 412 or the second programmable LED driver circuit 416 to adjust the brightness of each LED of the one or more LEDs 436 within one frame cycle. The frame cycle corresponds to a cycle rate or image frame rate of an electronic display or lighting system using the one or more LEDs 436. In other embodiments, the controller circuit 400 synchronizes the change in brightness of each LED of the one or more LEDs 436 with the output of the electronic display or lighting system using the one or more LEDs 436. For example, in a virtual reality game that is displayed on a virtual reality headset using one or more LEDs 436, the controller circuit 400 can synchronize the dimming of the LEDs with the display of a particular image on the headset.

[0034] Figure 5 illustrates an apparatus for controlling an LED array. The apparatus illustrated in Figure 5 includes a controller circuit 500, an LED driver circuit 504, a red LED 508, a green LED 512, a blue LED 516, and an electronic switching circuit 520. The electronic switching circuit 520 includes an electronic switch 524 and three resistors 528, 532, 536. In some embodiments, the apparatus illustrated in Figure 5 is used to control a lighting system having an LED array with two or more unique colors, e.g., purple, amber, white, etc.

[0035] The LED driver circuit 504 is configured to generate a current 540 to power the LEDs 508, 512, 516. The controller circuit 500 controls and operates the LED driver circuit 504 to regulate the amount of current 540 generated. The LEDs 508, 512, 516 are electrically connected to and powered by the LED driver circuit 504. The electronic switching circuit 520 is electrically connected to the LEDs 508, 512, 516. The electronic switching circuit 520 is configured to be placed in one of two switching configurations. For example, when the electronic switch 524 is open, the electronic switching circuit 520 is placed in a first switching configuration. When the electronic switch 524 is closed, the electronic switching circuit 520 is placed in a second switching configuration.

[0036] The electronic switching circuitry 520 directs a portion 544 of the current 540 away from the LEDs 508, 512, 516 such that a remaining portion 548 of the current 540 drives each of the LEDs 508, 512, 516. The portion 544 of the current 540 corresponds to the switching configuration in which the electronic switching circuitry 520 is placed. For example, in a first configuration, the portion 544 of the current 540 is zero.

[0037] When the red LED 508 is driven in the second switching configuration, a portion 544 of the current 540 corresponds to the voltage drop across the red LED 508 divided by the resistance of resistor 528. When the green LED 512 is driven in the second switching configuration, a portion 544 of the current 540 corresponds to the voltage drop across the green LED 512 divided by the resistance of resistor 532. When the blue LED 516 is driven in the second switching configuration, a portion 544 of the current 540 corresponds to the voltage drop across the blue LED 516 divided by the resistance of resistor 536. The remaining portion 548 of the current 540, which drives each of the LEDs 508, 512, 516, is therefore less than the current 540 at all times when the electronic switches are closed. For example, when the current 540 generated by the LED driver circuit 504 is in the range of 20 mA to 400 mA, the remaining portion 548 of the current 540 is in the range of 0 mA to 380 mA. The minimum brightness of the LEDs 508, 512, 516 in the second configuration (when the electronic switching circuit 520 is used) is therefore less than the minimum brightness of the LEDs 508, 512, 516 when the electronic switching circuit 520 is not used. The apparatus illustrated in FIG. 5 therefore provides a lower minimum brightness, a wider dynamic brightness range, and improved sensitivity control for the LED array compared to conventional methods.

[0038] In some embodiments, using the apparatus illustrated in FIGS. 1-5, the brightness and color characteristics of an electronic display (or other lighting system) can be adjusted by characterizing the temperature and current dependence of each LED and, based on the characterization, adjusting the manner in which the electronic display receives and handles the light emitted from the LED. These two steps are sometimes also referred to as "thermal calibration" or "color calibration" of the electronic display. The characterization step can occur during or after processing, for example while the electronic display is still in the factory, by positioning a light detection device (e.g., a spectrometer) at a distance from the eyepiece where a user's eye would receive the light when the device is in use. The light detection device detects the light output of each LED, in turn, through the electronic display while a controller (e.g., a feedforward controller) iterates through multiple temperatures and currents. The light output of the LEDs is analyzed to extract chromaticity and luminance data that is used to characterize each LED. When the electronic display is actually being used by a user, a calibration step is performed by measuring the temperature and adjusting the LED current and color calculation algorithms based on the characterization data as captured by the measured temperature. Details of the calibration process and feedforward control are disclosed in U.S. Patent Application Serial No. 16 / 530,599, which is incorporated herein by reference in its entirety.

[0039]

[0013] Figure 6 illustrates a method for controlling an LED array. In some embodiments, the process illustrated in Figure 6 is performed by the apparatus illustrated in Figure 1. In other embodiments, the process illustrated in Figure 6 is performed by other apparatus, such as the apparatus illustrated in Figures 2, 3, or 5.

[0040] An LED driver circuit (e.g., LED driver circuit 108) generates (604) a current (e.g., current 116). The LED driver circuit 108 and current 116 are shown and described in further detail with reference to FIG. 1. The current 116 is for powering one or more LEDs (e.g., one or more LEDs 112) of an LED array. The one or more LEDs 112 are shown and described in further detail with reference to FIG. 1.

[0041] One or more electronic switches (e.g., electronic switch 120) place an electronic switching circuit (e.g., electronic switching circuit 128) in one of a plurality of switching configurations (608). The electronic switch 120 and the electronic switching circuit 128 are shown and described in further detail with reference to FIG. 1 . The electronic switching circuit 128 includes a resistor 124. The electronic switching circuit 128 is electrically connected to the one or more LEDs 112. When the electronic switch 120 is open, the electronic switching circuit 128 is placed in a first switching configuration and the current 116 flows through the one or more LEDs 112, powering them one at a time.

[0042] The electronic switching circuitry 128 directs (612) a portion (e.g., portion 132) of the current 116 away from one or more LEDs 112 of the LED array. A remaining portion (e.g., remaining portion 136) of the current 116 drives one or more LEDs 112. The portion 132 of the current 116 corresponds to the switching configuration in which 128 is installed. Each LED has a first brightness in response to being driven by the current 116. Thus, the minimum brightness limit of the LED array corresponds to the minimum limit for the current 116 when the electronic switching circuitry 128 is not being used. Each LED has a second brightness in response to being driven by the remaining portion 136 of the current 116. Thus, the minimum brightness limit of the LED array corresponds to the minimum limit for the remaining portion 136 of the current 116 when the electronic switching circuitry 128 is being used. Thus, the second brightness is less than the first brightness, and the minimum brightness limit of the LED array can be reduced when the electronic switching circuit 128 is used compared to when the electronic switching circuit 128 is not used.

[0043] 7 illustrates a method for controlling an LED array. In some embodiments, the process illustrated in FIG. 7 is performed by the apparatus illustrated in FIG.

[0044] A controller circuit (e.g., controller circuit 400) places a first programmable LED driver circuit (e.g., first programmable LED driver circuit 412) in one of the set of first configurations (704). The controller circuit 400 and the first programmable LED driver circuit 412 are illustrated and described in further detail with reference to FIG. 4. For example, the controller circuit 400 generates a control signal 408 that places the first programmable LED driver circuit 412 in each of the set of first configurations. The first programmable LED driver circuit 412 is electrically connected to one or more LEDs (e.g., one or more LEDs 436) and configured to power the one or more LEDs 436. The one or more LEDs 436 are illustrated and described in further detail with reference to FIG. 4.

[0045] In each of the set of first configurations, the first programmable LED driver circuit 412 generates (708) a first current 420 to power one or more LEDs 436. The first current 420 corresponds to the configuration in which the first programmable LED driver circuit 412 is installed. The first current 420 is shown and described in further detail with reference to FIG.

[0046] The controller circuit 400 places (712) a second programmable LED driver circuit (e.g., the second programmable LED driver circuit 416) in a second one of the set of second configurations. The second programmable LED driver circuit 416 is shown and described in further detail with reference to FIG. 4. For example, the controller circuit 400 generates control signals 404 that place the second programmable LED driver circuit 416 in each of the set of second configurations. The second programmable LED driver circuit 416 is electrically connected to and configured to power the one or more LEDs 436.

[0047] In each of the second set of configurations, the second programmable LED driver circuit 416 generates (716) a second current 424 to power one or more LEDs 436. The second current 424 corresponds to the configuration in which the second programmable LED driver circuit 416 is installed.

[0048] An electrical network (e.g., electrical network 432) combines (720) the first current 420 and the second current 424 into a third current 428 to drive one or more LEDs 436 of the LED array. The brightness of each LED varies according to the first current 420 and the respective configuration in which the first programmable LED driver circuit 412 is installed. The brightness of each LED also varies according to the second current 424 and the respective configuration in which the second programmable LED driver circuit 416 is installed. By controlling the configuration in which the first programmable LED driver circuit 412 and the second programmable LED driver circuit 416 are installed, the controller circuit 400 adjusts the brightness of the LED array.

[0049] In some configurations, the controller circuit places the first programmable LED driver circuit in one of the set of first configurations. The first programmable LED driver circuit generates a first current corresponding to one of the set of first configurations. The controller circuit places the second programmable LED driver circuit in a second of the set of second configurations. The second programmable LED driver circuit generates a second current corresponding to the second of the set of second configurations. The electrical network combines the first current and the second current into a third current to drive one or more LEDs of the LED array.

[0050] In some configurations, placing the first programmable LED driver circuit in one of the first set of configurations adjusts a first current, and placing the second programmable LED driver circuit in a second of the second set of configurations adjusts a second current.

[0051] In some configurations, each LED of the one or more LEDs has a first minimum brightness in response to being driven by a first current. Each LED of the one or more LEDs has a second minimum brightness in response to being driven by a second current. Each LED of the one or more LEDs has a third minimum brightness in response to being driven by a third current. The third minimum brightness is equal to the lower of the first minimum brightness and the second minimum brightness.

[0052] In some configurations, each LED of the one or more LEDs has a first maximum brightness in response to being driven by a first current. Each LED of the one or more LEDs has a second maximum brightness in response to being driven by a second current. Each LED of the one or more LEDs has a third maximum brightness in response to being driven by a third current. The third maximum brightness is equal to the greater of the first maximum brightness and the second maximum brightness.

[0053] In some configurations, a brightness of each LED of the one or more LEDs varies according to each configuration of the first set of configurations, and a brightness of each LED of the one or more LEDs varies according to each configuration of the second set of configurations.

[0054] In some configurations, the one or more LEDs include a first LED having a first color and a second LED having a second color, the first color being different from the second color.

[0055] In some configurations, the controller circuit adjusts the brightness of each LED of one or more LEDs of the LED array within one frame cycle of the LED array.

[0056] In some configurations, the controller circuit synchronizes the output of the LED array with changes in brightness of each of one or more LEDs in the LED array.

Claims

[Claim 1] The invention described in this specification.

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