KR102331664B1 - High speed image refresh system - Google Patents

Abstract

An LED controller for an LED pixel array includes an image frame buffer for receiving image data; and a standby image buffer coupled to the image frame buffer to hold the standby image. The coupled command and control module is configured to replace the image in the image frame buffer with the standby image in the standby image buffer when image data is unavailable.

Description

HIGH SPEED IMAGE REFRESH SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is filed on June 28, 2019 in U.S. Patent Application No. 16/456,858, filed on June 28, 2019 in U.S. Patent Application Serial No. 16/456,862, filed on October 30, 2018 Claims priority to European Patent Application No. 18203445.4, and U.S. Provisional Patent Application No. 62/729,257, filed September 10, 2018, the entire contents of each of which are incorporated herein by reference. .

technical field

The present disclosure relates generally to a microcontroller having external data image inputs capable of supporting an addressable LED pixel array at high image refresh rates.

Although pixel arrays of LEDs with supporting CMOS circuitry have been used, practical implementations suitable for commercial use may face serious manufacturing, power and data management issues. The individual light intensity of thousands of light-emitting pixels may need to be controlled with a refresh rate of 30-60 Hz. For many applications, high data refresh rates are needed, and systems that support various calibration, test and control methods are needed.

In one embodiment, an LED controller for an LED pixel array includes a serial interface to an external data bus, along with the serial interface and an address generator coupled to the LED pixel array. The image frame buffer is coupled to the interface to receive image data and further coupled to an address generator to receive an image frame buffer address. The command and control module is coupled to the serial interface and configured to modify the image frame buffer output signals. The calibration data storage module is coupled to the command and control module for storing calibration data related to the pixel voltage response in the LED pixel array.

In one embodiment, the standby image buffer is coupled to the image frame buffer to hold the default image. In another embodiment, a pulse width modulator is coupled between the image frame buffer and the LED pixel array.

In some embodiments, the image frame buffer may refresh retained images at a rate of 60 Hz or higher. The image refresh data may be provided externally through a serial interface.

In one embodiment, the command and control module is coupled to an ADC that receives temperature data. The command and control module is coupled to the ADC that receives the _{V f data.} In some embodiments, the command and control module may be coupled to a DAC that receives _{V bias data.}

The command and control module may be coupled to a second interface that provides external control signals. In another embodiment, the command and control module includes a bypass line connected to the LED pixel array to allow for individual pixel addressing.

In some embodiments, images in the image buffer may be partially or differentially refreshed.

In some embodiments, an LED controller for an LED pixel array includes an image frame buffer for receiving image data; and a standby image buffer coupled to the image frame buffer to hold the standby image. The command and control module is configured to replace the image in the image frame buffer with the standby image in the standby image buffer when the image data is unavailable. Image data may be unavailable due to errors in the image, or failure to receive the image in a timely manner. In some embodiments, the image data held in the image frame buffer is provided, at least in part, by the vehicle or LED controller. Likewise, the atmospheric image may be provided, at least in part, by the vehicle or LED controller.

1 is a diagram illustrating the illumination of a road in individual sectors with active headlamps;
2 shows a dynamic pixel addressable lighting module positioned adjacent to a static lighting module.
3A is an embodiment of a vehicle headlamp system for controlling an active headlamp;
3B is one embodiment of a vehicle headlamp system for controlling an active headlamp having a connection to a vehicle processing output.
4 is a schematic diagram of one embodiment of an active headlamp controller;
5 is an illustration of a microcontroller assembly for an LED pixel array.
6A and 6B show an LDO bypass circuit for a pixel control circuit, and a gate timing diagram, respectively.
6C and 6D show alternative pixel control circuitry and gate timing diagrams, respectively.
7 shows an active matrix pixel array with row and column selection supporting LDO bypass.

Emissive pixel arrays can support applications that benefit from fine-grained intensity, spatial and temporal control of light distribution. This may include, but is not limited to, precise spatial patterning of light emitted from blocks of pixels or individual pixels. Depending on the application, the emitted light is spectrally distinct, adaptive over time, and/or environmentally responsive. Emissive pixel arrays can provide a pre-programmed light distribution in varying intensity, spatial or temporal patterns. The emitted light may be based at least in part on received sensor data and may be used for optical wireless communications. Associated optics may be distinguished at the pixel, block of pixels, or device level. An exemplary light emitting pixel array may include a device having a common controlled central block of high intensity pixels having an associated common optics, while edge pixels may have individual optics. Common applications supported by light emitting pixel arrays include video lighting, automotive headlights, architectural and area lighting, street lighting, and information displays.

Light emitting pixel arrays can be used to selectively and adaptively illuminate buildings or areas for improved visual display or to reduce lighting costs. Additionally, light emitting pixel arrays can be used to project media facades for decorative motion or video effects. In conjunction with tracking sensors and/or cameras, selective illumination of areas surrounding the pedestrian may be possible. The spectrally distinct pixels may be used to control the color temperature of illumination as well as support horticultural illumination for each wavelength.

Street lighting is an important application that can greatly benefit from the use of light emitting pixel arrays. A single type of light emitting array can be used to mimic the different types of street lights, eg to allow switching between a Type I linear street light and a Type IV semicircular street light by appropriate activation or deactivation of selected pixels. Additionally, street lamp cost can be reduced by adjusting the light beam intensity or distribution according to environmental conditions or usage time. For example, light intensity and distribution area may be reduced when no pedestrians are present. When the pixels of the light emitting pixel array are spectrally distinct, the color temperature of the light can be adjusted according to the respective daylight, twilight, or nighttime conditions.

Light emitting arrays are also well suited to support applications requiring direct or projection display. For example, warning, emergency or information indications may all be displayed or projected using light emitting arrays. This allows, for example, exit signs that change color or flash to be projected. If the light emitting array is composed of a large number of pixels, text or numeric information may be presented. Directional arrows or similar indicators may also be provided.

Vehicle headlamps are light-emitting array applications that require high pixel counts and high data refresh rates. Automotive headlights that actively illuminate only selected sections of the roadway can be used to reduce problems associated with glare or dazzling of oncoming drivers. Using infrared cameras as sensors, light-emitting pixel arrays activate only those pixels necessary to illuminate the roadway, while deactivating pixels that could dazzle the eyes of pedestrians or drivers of oncoming vehicles. Additionally, to improve the driver's environmental awareness, off-road pedestrians, animals or signs may be selectively illuminated. When the pixels of the light emitting pixel array are spectrally distinct, the color temperature of the light can be adjusted according to the respective daylight, twilight, or night conditions. Some pixels may be used for optical wireless vehicle-to-vehicle communication.

One high-value application for light-emitting arrays is shown with respect to FIG. 1 , which shows a potential roadway lighting pattern 100 for a vehicle headlamp system that illuminates an area 120 in front of the vehicle. As shown, road 110 includes a left edge 112 , a right edge 114 , and a centerline 116 . In this example, two main areas are illuminated - a downward statically illuminated area 122 and a dynamically illuminated area 130 . The light intensity within region 130 may be dynamically controlled. For example, as an oncoming vehicle (not shown) traveling between the centerline 116 and the left edge 112 moves into a subregion 132 , the light intensity may be reduced or completely blocked. . As an oncoming vehicle moves towards small area 134, a series of small areas (not shown) may also be defined to have reduced light intensity, thereby reducing the possibility of unsafe glare or glare. Reduce. As will be appreciated, in other embodiments, the light intensity may be increased to highlight road signs or pedestrians, or with spatial lighting patterns adjusted to allow dynamic light tracking of, for example, a curved road.

FIG. 2 illustrates positioning of lighting modules 200 that may provide an illumination pattern as discussed in relation to FIG. 1 . The LED light module 222 may include LEDs alone or with primary or secondary optics including lenses or reflectors. To reduce overall data management requirements, the light module 222 may be limited to an on/off function, or to switch between relatively small light intensity levels. Pixel level control of light intensity is not necessarily supported.

Located adjacent to the LED light module 222 is an active LED array 230 . The LED array includes a CMOS die 202 having a pixel region 204 and alternatively selectable LED regions 206 and 208 . Pixel region 204 may have 104 rows and 304 columns, with a total of 31,616 pixels distributed over an area of 12.2 millimeters by 4.16 millimeters. Selectable LED regions 206 and 208 allow for different aspect ratios suitable for different vehicle headlamps or applications to be selected. For example, in one embodiment, the selectable LED region 206 may have a 1:3 aspect ratio with 82 rows and 246 columns, with a total of 20,172 pixels distributed over an area of 10.6 millimeters by 4 millimeters. do. Alternatively, the selectable LED region 208 may have a 1:4 aspect ratio with 71 rows and 284 columns, with a total of 20,164 pixels distributed over an area of 12.1 millimeters by 3.2 millimeters. In one embodiment, the pixels may be actively managed to have a 10-bit intensity range, and a refresh rate of 30-100 Hz, with a typical operating refresh rate of 60 Hz or higher.

3A shows an embodiment of a vehicle headlamp system 300 including a vehicle assist power 302 , and a control system that includes a data bus 304 . The sensor module 306 may detect environmental conditions (eg, time of day, rain, fog, ambient light level, etc.), vehicle conditions (parking, moving, speed, direction), or the presence/location of other vehicles or pedestrians. may be coupled to the data bus 304 to provide data related to . A separate headlamp controller 330 may be connected to the vehicle assist power and control system.

The vehicle headlamp system 300 may include a power input filter and a control protection module 310 . Module 310 may support various filters to reduce conducted emissions and provide power immunity. Electrostatic discharge (ESD) protection, load-dump protection, alternator field attenuation protection, and reverse polarity protection may also be provided by module 310 .

The filtered power may be provided to the LED DC/DC module 312 . Module 312 may only be used to power the LEDs, and typically has an input voltage between 7 and 18 volts with a nominal 13.2 volts. The output voltage may be set slightly higher (eg, 0.3 volts) than the LED array maximum voltage determined by factory or local calibration and operating condition adjustments due to load, temperature or other factors.

The filtered power is also provided to a logic LDO module 314 that can be used to power the microcontroller 322 or CMOS logic of the active headlamp 324 .

The vehicle headlamp system 300 may also include a bus transceiver 320 (eg, having a UART or SPI interface) coupled to a microcontroller 322 . Microcontroller 322 may interpret vehicle input based on or including data from sensor module 306 . The interpreted vehicle input may include a video signal transmittable to an image buffer of the active headlamp module 324 . Additionally, microcontroller 322 can load default image frames and test for open/shorted pixels during startup. In one embodiment, the SPI interface loads the image buffer into CMOS. Image frames may be full frame, differential or partial. Other microcontroller 322 features may include a logic LDO output as well as a control interface monitor of CMOS state including die temperature. In some embodiments, the LED DC/DC output can be dynamically controlled to minimize headroom. In addition to providing image frame data, other headlamp functions, such as those used complementary to side markers or turn signals, and/or activation of daytime running lights may also be controlled.

3B shows one embodiment of various components and modules of a vehicle headlamp system 330 that can accept vehicle sensor inputs and commands, as well as commands based on the headlamp or locally mounted sensors. As can be seen in FIG. 3B , on-board systems 332 may include remote sensors 340 , and electronic processing modules capable of sensor processing 342 . The processed sensor data may be input to various decision algorithms within the decision algorithm module 344 , which may include, for example, ambient light level, time of day, vehicle location, location of other vehicles, road conditions, or weather conditions. resulting in command instructions or pattern generation based, at least in part, on various sensor input conditions, such as As will be appreciated, useful information for the decision algorithm module 344 is also provided from other sources including connections to the user's smart phone, vehicle-to-vehicle wireless connections, or connections to remote data or information resources. can be

Based on the results of the decision algorithm module 344 , the image generation module 346 provides an image pattern that will ultimately provide the vehicle headlamp with an active lighting pattern that is dynamically adjustable and suitable for conditions. This generated image pattern may be encoded for serial or other transmission scheme by the image coding module 348 and transmitted to the image decoding module 354 via the high-speed bus 350 . Once decoded, the image pattern is provided to the uLED module 380 to drive activation and intensity of the illumination pixels.

In some modes of operation, system 330 may be driven with a default or simplified image pattern using instructions provided to headlamp control module 370 via connection of decision algorithm module 344 via CAN bus 352 . can For example, the initial pattern when starting the vehicle may be a uniform pattern of low light intensity. In some embodiments, the headlamp control module may be used to drive other functions including sensor activation or control.

In other possible modes of operation, system 330 may be driven with an image pattern derived from local sensors or commands, without requiring input via CAN bus 352 or high-speed bus 350 . For example, local sensors 360 , and electronic processing modules capable of sensor processing 362 may be used. The processed sensor data may be input to various decision algorithms within the decision algorithm module 364 , which may include, for example, ambient light level, time of day, vehicle location, location of other vehicles, road conditions, or weather conditions. resulting in command instructions or pattern generation based, at least in part, on various sensor input conditions, such as As will be appreciated, useful information for the decision algorithm module 364, such as the vehicle assisted remote sensors 340, may include connections to the user's smart phone, vehicle-to-vehicle wireless connections, or remote data or information resources. may also be provided from other sources, including links to

Based on the results of the decision algorithm module 364 , the image generation module 366 provides an image pattern that will ultimately provide the vehicle headlamp with an active lighting pattern that is dynamically adjustable and suitable for conditions. In some embodiments, this generated image pattern may be transmitted directly to the uLED module 380 to drive illumination of selected pixels without requiring additional image coding/decoding steps.

FIG. 4 shows one embodiment of various components and modules of an active headlamp system 400 such as that described for active headlamp 330 of FIG. 3 . As shown, the internal modules include an LED power distribution and monitor module 410 , and a logic and control module 420 .

Images or other data from the vehicle may arrive via the SPI interface 412 . Successive images or video data may be stored in image frame buffer 414 . If image data is not available, one or more standby images held in the standby image buffer 416 may be directed to the image frame buffer 414 . Such atmospheric images may include, for example, intensity and spatial patterns consistent with the vehicle's legally permitted low beam headlamp radiation patterns. If it is determined that the image data is in error or it has not been received in a timely manner, the image data may also be replaced with standby images. In some embodiments, before replacing the atmospheric image, the image frame may be repeated from the determined number of times.

In operation, the pixels in the images are used to define the response of the corresponding LED pixels in the pixel module 430 , and the intensity and spatial modulation of the LED pixels is based on the image(s). To reduce data rate issues, in some embodiments groups of pixels (eg, a 5x5 block) may be controlled as single blocks. High speed and high data rate operation is supported, where pixel values from successive images can be loaded as successive frames in an image sequence at a rate of 30 Hz to 100 Hz, with 60 Hz being typical. With respect to the pulse width modulation module 418 , each pixel within the pixel module may be operable to emit light in a pattern and intensity that depends, at least in part, on the image held in the image frame buffer 414 .

In one embodiment, the intensity may be individually controlled and adjusted by using the logic and control module 420 and the pulse width modulation module 418 to set the appropriate ramp time and pulse width for each LED pixel. This allows for staging of LED pixel activation to reduce power fluctuations and provide various pixel diagnostic functions.

5 shows a microcontroller assembly 500 for an LED pixel array. Assembly 500 may receive logic power through Vdd and Vss pins. The active matrix receives power for controlling the LED array by a _{plurality of V LEDs} and V _{cathode pins.} Serial Peripheral Interface (SPI) can provide full-duplex mode communication using a master-slave architecture with a single master. The master device generates frames for reading and writing. Multiple slave devices are supported through selection with individual slave select (SS) lines. The input pins may include a Master Output Slave Input (MOSI), a Master Input Slave Output (MISO), a chip select (SC) and a clock (CLK) and , all of which are connected to the SPI interface.

In one embodiment, the SPI frame contains 2 stop bits (both "0"), 10 data bits, MSB first, 3 CRC bits (x3 + x + 1), start 111b and target 000b. The timing may be set according to the SafeSPI “in-frame” standard.

MOSI field data may be as follows:

Frame 0: header

Frame 1/2: Start column address [SCOL]

Frame 3/4: Start row address [SROW]

Frame 5/6: Number of columns [NCOL]

Frames 7/8: Number of rows [NROW]

Frame 9: Intensity Pixels [SCOL, SROW]

Frame 10: Intensity Pixels [SCOL + 1, SROW]

Frame 9 + NCOL: intensity pixels [SCOL + NCOL, SROW]

Frame 9 + NCOL + 1: Intensity Pixels [SCOL, SROW + 1]

Frame 9 + NCOL + NROW: intensity pixels [SCOL + NCOL, SROW + NROW]

MISO field data may include loopback of frame memory.

A field refresh rate of 60 Hz (60 full frames per second) is supported, with bit rates of at least 10 Mbps, typically between 15 and 20 Mbps.

The SPI interface is coupled to an address generator, a frame buffer, and a standby frame buffer. The pixels have a parameter set and signals or power modified by the command and control module (eg, via power gating prior to input to the frame buffer, or after output from the frame buffer via pulse width modulation or power gating). can have The SPI interface may be coupled to the address generation module, which in turn provides row and address information to the active matrix. The address generator module may in turn provide the frame buffer address to the frame buffer.

The command and control modules ^{can be controlled externally via an I 2} C (Inter-Integrated Circuit) serial bus. A clock (SCL) pin and a data (SDA) pin with 7-bit addressing are supported.

The command and control module includes a digital-to-analog converter (DAC), and two analog-to-digital converters (ADC). They are used to set _{the V bias} for the connected active matrix, _{help determine the maximum V f ,} and determine the system temperature, respectively. An oscillator OSC is also connected to set the pulse width modulated oscillation (PWMOSC) frequency for the active matrix. There are also bypass lines that allow the addressing of individual pixels or blocks of pixels within the active matrix for diagnostic, calibration, or test purposes.

In one embodiment, the command and control module may provide the following inputs and outputs.

Input to CMOS chip:

VBIAS: Set the voltage bias for the LDO.

GET_WORD [...]: Request output from CMOS.

TEST_M1: Pixel test run: LDO in bypass mode uses an internal 1 μA source to address columns sequentially, then rows, output VF.

Vf values output through SPI.

TEST_M2: Pixel test run: LDO in bypass mode uses external I source to address columns sequentially, then rows, output VF.

Vf values output through SPI.

TEST_M3: LDO in bypass mode uses an internal 1μA source to address via I2C and output Vf via I2C.

TEST_M4: LDO in bypass mode uses an external I source to address via I2C and output Vf via I2C.

BUFFER_SWAP: Swapping to/from the standby buffer.

COLUMN_NUM: Addressing a specific row.

ROW_NUM: Addressing a specific column.

Output from CMOS chip:

CW_PHIV_MIN, CW_PHIV_AVG, CW_PHIV_MAX: Factory measured EOL global luminous flux data.

CW_VLED_MIN, CW_VLED_AVG, CW_VLED_MAX: Factory measured EOL global forward voltage data.

CW_SERIALNO: Die/CMOS combo serial number for traceability purposes.

TEMP_DIE: The value of the die temperature.

VF: The value of the Vf bus as addressed by COLUMN_NUM and ROW_NUM.

BUFFER_STATUS: Indicates which buffer is being selected.

Various calibration and testing methods for microcontroller assembly 500 are supported. During factory calibration, the V _f of every pixel can be measured. The maximum, minimum and average V _f of the active region may be “burned” as a calibration frame. The maximum Vf and dVf/dT calibration frames can be used with the measured die temperature to dynamically determine the _{actual V LED. Typically, V LEDs} between 3.0V-4.5V are supported, the actual value determined by a feedback loop to an external DC/DC converter as described for FIG. 3 .

6A and 6B show one embodiment of a pixel control circuit 600 and an associated timing diagram 610, respectively. Pixel control circuit 600 includes logic with bypass signals and row and column selection. The PWN OSC input and data, along with the output from the logic, are fed first into the generator and then into the PWM. After all, PWM has a duty cycle that controls the activation of a particular pixel. This is described in more detail in connection with the following description of the pixel control circuit 630 of FIG. 6C . The factory-calibrated V _f of all pixels can be measured at 1.0 μA and 1.0 mA using an external current source and LDO bypass function.

This operation may be bypassed when the LED pixel is supported by a low dropout (LDO) linear regulator as shown in circuit 600 . During bypass, V _f can be measured with an internal 1 μA current source or an external current source on the _{V LED.} Bypass can be done as a per-pixel operation using row and column selection. Advantageously, this pixel bypass circuit allows determination of whether a particular pixel is operating correctly or if any error condition has occurred.

)는 각각의 픽셀에 대해 상이하게 설정될 수 있다.As shown in FIG. 6B , image data and pulse width modulated oscillation clock data may be received by a pulse width modulator. Based on input from the logic module, gate timing including pulse start, ramp time and pulse duration/width (duty cycle) can be set in pixels. For example, the duty cycle [delta] may be loaded from the frame buffer at "read". 8-bit δ resolution may be supported. In one embodiment, pulse leading-edge phase shift (

) can be set differently for each pixel.

6C shows a pixel control circuit 630 that does not support a bypass circuit. Pixel control circuitry 630 includes logic with row and column selection. The output from the logic is fed first into the generator and then into the PWM. After all, PWM has a duty cycle that uses additional circuitry to control the activation of a particular pixel in the following manner. The three switches K1 to K3 are controlled by signals received from a central control block outside the pixels. Switch K3 is a current source or LDO, its current is controlled by Vbias. K2 is a PWM switch that is turned on and off based on the PWM duty cycle determined by the image data. In this example, K2 and K3 are P channel MOSFets but may be any other suitable type of switch. In Figure 6c, the PWM signal is connected to the gate of K2, and the drain node of K2 is connected to the gate of K3. Consequently, when the PWM signal is high, K2 is off and K3 is on, so the LED is on and the current is determined by the Vbias voltage. When PWM is low, K2 is on, turning it off by pulling K3 gate high, so the LED is off.

The switch K1 is turned on and off based on the row select and column select signals. K1 will only turn on when a particular pixel's row and column is selected, otherwise it will stay off. When K1 is turned on, its impedance will be low and the LED forward voltage at the anode or Va node of that pixel will appear on the Vf bus. Since the impedance of the Vf bus is much higher than that of K1 in the turn-on state, the Vf voltage will be equal to the Va node voltage. When a fault condition occurs in a circuit or LED, the LED forward voltage can deviate from its normal value. Thus, the Vf voltage can be used to determine if a pixel is operating correctly or if any error condition has occurred, without requiring specific pixel bypass circuitry such as that disclosed for FIG. 6A . In this way, real-time or “on-the-fly” detection can be realized, whereby pixel status can be monitored and reported during operation.

Because the V _f bus is a shared node for all pixels, the K1 switch can only be turned on for one pixel at a time. The best time to detect error conditions is when the pixel is turned on by PWM. Preferably, the PWM values defined by the application image may be used for testing, although special test images may also be optional. When a pixel is turned off, detection can still be done, albeit at a more limited level than during turn on.

K1 switching control for PWM can be flexible. Depending on the detection requirements, the K1 frequency may be higher or lower than the PWM frequency. Obviously, the higher the K1 frequency, the faster the detection, ie more pixels can be tested in a time span. For example, if the PWM frequency is 500 Hz, then with a K1 frequency of 500 Hz only one pixel can be tested for one PWM period or 2 ms, whereas with a K1 frequency of 5000 Hz, 10 pixels can be tested for 2 ms. can Moreover, the two frequencies may be synchronous or asynchronous.

6D shows an exemplary control scheme for a pixel control circuit. In this embodiment, the K1 frequency is set close to the PWM frequency at which the turn-on is synchronized. It should be noted that although this example shows only three pixels, it can be extended in a similar manner to an entire matrix array of pixels. For each pixel, the diagram shows the PWM signal voltage, the Va node voltage, and the K1 control voltage. For a normal pixel, the Va node voltage is high when the PMM signal is high and low when the PWM is low. Similarly, K1 turns on when the K1 control voltage is high and turns off when the control voltage is low. Depending on the circuit design, the control phases of PWM and K1 can be reversed, turning each switch on when it is low and turning off each switch when it is high.

The operation of pixel 1 proceeds as follows:

t1 to t4: PWM voltage is high. The pixel is turned on and the Va node is high. Meanwhile, the K1 control voltage is also high at t1 and is synchronized with the turn-on of the PWM. The K1 control voltage is held low for pixels 2 and 3. Since K1 of pixel 1 is turned on and the Va node voltage appears on the Vf bus, the Vf bus voltage is equal to the Va voltage of pixel 1 at this time. Since the turn-off moment t3 of K1 is earlier than the turn-off moment t4 of the PWM, the pixel test can be completed before the pixel is turned off.

The operation of Pixel 2 proceeds as follows:

At t2: PWM is high and the pixel is turned on. The slight delay between t1 and t2 is a phase shift. At this time, since K1 of pixel 1 is still on, the K1 control voltage of pixel 2 is low and pixel 2 is not tested during this PWM cycle.

t5 to t7: PWM is high and the pixel is turned on again for a second time. The K1 control voltage is synchronized with pixel 2 at the turn-on moment of t5 and remains on until t6. The K1 control voltage is held low for the other two pixels. Thus, the Vf bus voltage reflects the Va node voltage of pixel 2. In this example, the PWM duty cycle of pixel 2, which is the conduction or on time expressed as a period or percentage of cycle time, is greater than the duty cycle of pixel 1. The voltage Va of pixel 2 is lower than the voltage of pixel 1 when turned on.

The operation of Pixel 3 proceeds as follows:

PWM is always low. The pixel stays off and the Va node voltage is low.

t8 to t9: The K1 control voltage is high for pixel 3 and low for the other two pixels. Consequently, the Vf bus voltage at this time represents the low Va voltage of pixel 3. The Va node voltage relationship is:

7 shows a block diagram 600 of an active matrix array supporting LDO bypass in greater detail. Row and column selection is used to address individual pixels fed to the data line, bypass line, PWMOSC line, V _bias line and V _{f line.} The timing and activation of the gate and pulse width modulator oscillator (PWMOSC) is shown with respect to FIG. 6B . As will be appreciated, in certain embodiments LDO bypass is not required and the pixel test may proceed using the circuitry and/or control schemes described with respect to FIGS. 6C and 6D .

Many modifications and other embodiments of the present invention will occur to those skilled in the art having the benefit of the teachings presented in the above description and associated drawings. Accordingly, it is to be understood that the invention is not limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims. It is also understood that other embodiments of the invention may be practiced without elements/steps not specifically disclosed herein.

Claims (20)

An LED controller for a light emitting diode (LED) pixel array, comprising:
a driving module configured to drive the LED pixel array;
an image frame buffer configured to receive image data;
a standby image buffer coupled to the drive module in series with the image frame buffer, the standby image buffer configured to hold a standby image; and
a command and control module coupled to both the image frame buffer and the standby image buffer, wherein the command and control module, in response to determining that the image data is unavailable, writes the standby image in the standby image buffer to the image frame buffer. Constructed to Orient -
An LED controller for an LED pixel array, comprising: The LED controller of claim 1 , wherein the command and control module is configured to determine that the image data is unavailable due to an error in the received image data. The LED of claim 1 or 2, wherein the command and control module is configured to determine that the image data is unavailable due to failure to timely receive the image data in the image frame buffer. controller. 3. The LED controller of claim 1 or 2, wherein the image frame buffer is configured to receive the image data from a vehicle. The LED controller according to claim 1 or 2, wherein the atmospheric image data held in the atmospheric image buffer is provided at least in part by a vehicle. 3. The LED controller of claim 1 or 2, wherein the standby image data held in the standby image buffer is provided at least in part by the LED controller. The LED controller according to claim 1 or 2, wherein the image frame buffer is capable of refreshing held images at a rate of 30 Hz or higher. The LED controller according to claim 1 or 2, wherein the image frame buffer is capable of refreshing held images at a rate of at least 60 Hz. 3. The LED controller of claim 1 or 2, wherein images in the image frame buffer can be partially refreshed. 3. The LED controller of claim 1 or 2, wherein images in the image frame buffer can be refreshed differentially. The LED controller according to claim 1 or 2, wherein images in the image frame buffer can be modified by the command and control module. 3. The method of claim 1 or 2, wherein the command and control module is configured to direct the standby image in the standby image buffer to the image frame buffer by issuing a buffer swapping command for swapping the standby image into the image frame buffer. An LED controller for an LED pixel array, configured to: The LED according to claim 1 or 2, wherein the command and control module is configured to direct the standby image in the standby image buffer to the image frame buffer after the stored image in the image frame buffer is repeated a threshold number of times. LED controller for pixel array. A vehicle headlamp system comprising:
a vehicle supported power and control system including a data bus;
a headlamp module having a light emitting diode (LED) controller with an array of connected LED pixels;
a driving module configured to drive the LED pixel array;
an image frame buffer in the LED controller, the image frame buffer configured to receive image data;
a standby image buffer in the LED controller, the standby image buffer being connected to the driving module in series with the image frame buffer, and configured to hold a standby image; and
a command and control module in the LED controller, wherein the command and control module is configured to direct the standby image in the standby image buffer to the image frame buffer in response to determining that the image data is unavailable.
A vehicle headlamp system comprising a. The vehicle headlamp system of claim 14 , wherein the command and control module is configured to determine that the image data is unavailable due to an error in the received image data. 16. A vehicle headlamp system according to claim 14 or 15, wherein the command and control module is configured to determine that the image data is unavailable due to failure to timely receive the image data in the image frame buffer. 16. A vehicle headlamp system according to claim 14 or 15, wherein the image frame buffer is configured to receive the image data from a vehicle. 16. A vehicle headlamp system according to claim 14 or 15, wherein the atmospheric image data held in the atmospheric image buffer is at least partially provided by the vehicle. 16. A vehicle headlamp system according to claim 14 or 15, wherein the atmospheric image data held in the atmospheric image buffer is provided at least in part by the LED controller. 16. The method of claim 14 or 15, wherein the command and control module is configured to direct the standby image in the standby image buffer to the image frame buffer by issuing a buffer swapping command for swapping the standby image into the image frame buffer. A vehicle headlamp system configured to

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