Patent Application
20070182677
The invention relates to a vehicle display configuration, in particular to a display with light emitting diodes (LEDs) for automotive applications, and to a method of controlling an LED display.
LEDs are increasingly used as a replacement for conventional incandescent lamps in cars. For example, LEDs are used in rear lights of cars. General advantages of LEDs over conventional incandescant lamps are their small size, their energy efficiency and their long life expectancy.
Depending on the specific applications in which LEDs are used, it may be necessary to drive the LEDs with a control circuit. For example, if it is desired to have LEDs with an adjustable brightness, the control circuit must be able to control the LEDs such that the brightness can be adjusted to various levels.
For some applications, LEDs are mounted on a circuit board and a row-column method of driving the LEDs is used. This row-column driving method, configured to reduce the number of wires required for a dot-matrix LED control, is achieved by creating a grid of LED connections by which LEDs are pulsed at a high current for a short period of time. A disadvantage of the row-column driving method is that the controllability is limited because only a single LED may be uniquely addressed at a time. As a consequence, it is not possible to simultaneously control the brightness of each individual LED.
According to another method, it is possible to control the brightness over an entire display of LEDs that are mounted on a circuit board. In this case the control is based on varying the supply voltage for the LED display similar to a dimmer switch on a household light. A disadvantage of this solution is that the brightness control affects all LEDs of the display and brightness is shared among all LEDs within the display. It is thus not possible to control individual LEDs or LED segments.
Several U.S. patents disclose the use of LEDs as light sources. U.S. Pat. No. 6,299,337 B1 discloses a flexible multiple LED module having a plurality of rigid printed circuit boards which are connected to one another via a flexible printed circuit board. The LED module has a given flexibility due to the flexible circuit boards provided between the rigid circuit boards.
U.S. Pat. No. 6,657,767 B2 discloses a rearview mirror assembly with LEDs mounted on a flexible circuit board behind the mirror. The LEDs are controlled together and are used as a turn signal indicator.
U.S. Pat. No. 6,652,128 B2 discloses a backlighting method for an automotive trim panel. The trim panel is perforated and a light source is mounted behind the trim panel. An LED incorporated in a flexible printed circuit may serve as the light source.
U.S. Pat. No. 6,158,882 discloses an LED semiconductor lighting system for illuminating vehicle interiors. The lighting system includes a light tube with LEDs inside the light tube. The illumination intensity of the LEDs is controlled by a dimming module.
It is accordingly an object of the invention to provide a vehicle display configuration which overcomes the above-mentioned disadvantages of the heretofore-known vehicle display configurations of this general type and which provides an improved control of individual LEDs or segments of an LED display, in particular their on-off states and their brightness, and which allows a versatile mounting of the LEDs on irregular or non-planar surfaces, in particular on curved surfaces of a vehicle, and which can endure environmental conditions typical for automotive applications. A further object of the invention is to provide a method for controlling an LED display.
With the foregoing and other objects in view there is provided, in accordance with the invention, a vehicle display configuration, including:
a mounting layer having a surface shape;
an LED display including a flexible circuit board and a plurality of LEDs mounted on the flexible circuit board;
the flexible circuit board conforming to the surface shape of the mounting layer;
a control circuit including a driver circuit operatively connected to the LEDs for controlling the LEDs;
the driver circuit having a serial data input and a shift register, the driver circuit shifting data received via the serial data input into the shift register; and
the driver circuit controlling the LEDs in accordance with the data in the shift register.
Advantages of the above-defined vehicle display configuration are that it can be mounted on irregular mounting surfaces, that it conforms to the curvature of the mounting surface and that the on-off states and the brightness of the individual LEDs can be independently controlled. The vehicle display configuration increases the number of surfaces that are suitable for mounting light sources and provides the ability to produce a variety of lighting effects, display graphics or text.
According to another feature of the invention, the control circuit includes a microcontroller connected to the driver circuit for sending data to the serial data input of the driver circuit. Using a microcontroller for providing control data is advantageous because a microcontroller allows implementing a variety of features such as dimming, visual effects, or display graphics. The term microcontroller is understood as a broad term that covers not only dedicated controllers but also covers other types of controllers such as computers or digital signal processors.
According to yet another feature of the invention, the driver circuit is an integrated circuit mounted on the flexible circuit board. Providing the driver circuit on the flexible circuit board simplifies the installation of the vehicle display configuration.
According to yet another feature of the invention, the driver circuit is a first driver circuit connected to a first group of the LEDs mounted on the flexible circuit board; the control circuit includes a microcontroller and includes a second driver circuit connected to a second group of the LEDs mounted on the flexible circuit board; the first driver circuit and the second driver circuit each have a serial data input, a serial data output and a shift register; the serial data input of the first driver circuit is connected to the microcontroller for receiving data from the microcontroller; the serial data input of the second driver circuit is connected to the serial data output of the first driver circuit for receiving data cascaded through the first driver circuit; the first driver circuit and the second driver circuit respectively shift data received via the serial data input into the shift register; and the first driver circuit and the second driver circuit respectively control the first group and the second group of the LEDs in accordance with the data in the shift register. An advantage of cascading the driver circuits is that it allows controlling a plurality of driver circuits and thus allows controlling an increased number of LEDs.
According to a further feature of the invention, the control circuit adjusts a brightness of the LEDs by switching the LEDs on and off in a recurring pattern. An advantage of controlling the brightness by switching the LEDs on and off, rather than adjusting the brightness by adjusting a supply voltage to the LEDs, is that a color shift or wavelength shift of the LEDs can be avoided.
According to a further feature of the invention, the flexible circuit board is coated with a protective material such as polyurethane, acrylic, plastic, rubber or an electromagnetic interference shielding material. A protective layer is advantageous in order to protect the display from moisture, corrosive agents, mechanical pressure or ultraviolet light.
According to a yet further feature of the invention, a liner material at least partially covers the LED display, the LEDs emit light through the liner material; and the liner material is a vehicle roof liner material, a vehicle seat cover material, a vehicle interior panel material or a vehicle dashboard material. Mounting the LED display behind a liner allows creating aesthetically pleasing lighting sources and lighting effects.
According to another feature of the invention, the flexible circuit board is fastened to the mounting layer with a fastening element such as a retaining clip, a hook and loop fastener or an adhesive. An advantage of fastening the circuit board with an adhesive is that no mechanical fastening structures on the mounting layer are necessary.
According to another feature of the invention, the mounting layer is translucent and the flexible circuit board includes translucent lead lines. This feature allows integrating an LED display into a window glass.
According to yet another feature of the invention, the mounting layer is a vehicle component such as a gear shifter, a door handle or a vehicle key.
According to another feature of the invention, an electronic element such as a push button or a sensor element is mounted on the flexible circuit board. This feature advantageously allows mounting pushbuttons or sensors on surfaces without requiring mounting structures such as mounting brackets, mounting holes or the like.
According to yet another feature of the invention, the flexible circuit board is configured to have no through-hole components mounted thereon. An advantage of an LED display according to the invention which has no through-hole components is that they can endure higher levels of mechanical stress and vibration without being damaged.
With the objects of the invention in view there is also provided, a method of controlling a display, which includes the steps of:
providing cycle periods and controlling an LED by switching the LED at each cycle period into an on-state or an off-state;
providing N bits for controlling the on-state and the off-state of the LED, N being an integer greater than 2;
controlling the on-state and the off-state of the LED by repeatedly performing steps a) and b) starting with n=1 and increasing n by 1 until n=N:
Another mode of the method of the invention includes creating a recurring interrupt pattern waveform by continuously repeating the steps a) and b) for n=1 to n=N; and using the recurring interrupt pattern waveform for continuously controlling the LED. An advantage of controlling an LED display with a recurring interrupt pattern waveform is that the LEDs can be controlled with respect to their brightness and that a variety of lighting effects can be generated such as a pulsating heartbeat effect or the effect of a propagating wave.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a vehicle display configuration and a method of controlling a display, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Referring now to the figures of the drawings in detail and first, particularly, to
The LED display 14 which is shown in
The LED display 14 emits for example white light in a uniform manner for an exterior parking light, warning display, interior ambient light, map light or accent light. LEDs of any color may be substituted into the display, as well as a combination of colors or discrete multi-color LEDs.
By controlling the on-off states of the LEDs 16, the LED display 14 can be used to create the impression of movement, visual cues or effects based in the state of the vehicle. For example, the LEDs 16 may flash in the event of a sudden stop, create an indicative motion left-right based on turn signals, brighten when the vehicle transmission is in park, react to the accelerator, or pulsate with the music playing on the vehicle's stereo. The LEDs may further be controlled to be turned on or off in a given sequence, for example starting at one end of the display and propagating to the other end of the display. A pulsating heartbeat effect, whereby all LEDs are simultaneously dimmed on and off, can also be created. It is further possible to create a wave-like effect, where each LED pulsates with a phase offset to create a chasing or traveling pattern. The direction and speed of travel may be chosen as desired.
In a vehicle, an LED display may be mounted beneath a fabric roof liner and extend from the front of the vehicle to the rear of the vehicle. When such an LED display is switched off, it may be controlled such that the illumination fades starting in the front of the vehicle and the fading effect propagates to the rear of the vehicle.
In principle any PCB (printed circuit board) may be constructed as a flexible circuit, however, it was found that through-hole components, which are regarded as the most stable of PCB components, are unsuitable for mounting on the flexible PCB 18.
Mechanical stress and vibration may cause a stretching and tearing of the flexible polyamide PCB 18. As a result, pad separation becomes a problem with through-hole components. Thus, the flexible circuit board 18 is preferably configured to have no through-hole components mounted thereon.
In order to prevent damage to the flexible LED display 14, which may be caused by corrosive agents, ultraviolet light, dust, moisture or mechanical stress, it is advantageous to coat or encase the flexible circuit board 18 with polyurethane. In order to protect the flexible circuit board 18 from radio frequency (RF) interference or noise, it is advantageous to paint the flexible circuit board 18 with an RF or noise shielding material.
The flexible LED display 14 is coated or cast in a protective layer 15 and is disposed on the mounting surface 20 with an adhesive layer 22 provided between the mounting surface 20 and the flexible LED display 14. As can be seen in
The LED display 14 may be mounted behind substantially any cloth or fabric surface such that it provides a hidden, distributed light source. Substantially any fabric surface can therefore be transformed into a lighting element. This allows improving the light distribution and light output.
In the embodiments of the vehicle display configurations shown in FIGS. 5 to 7, the flexible LED display 14 is sufficiently bendable and pliable so that it follows the surface contour of the surface 20 on which it is mounted. As described above, various mounting methods may be used in order to fasten the flexible LED display 14. Also, the LED display 14 may be cast into an acrylic, plastic or rubber material prior to being fastened to the mounting layer 12.
As a result of the flexibility of the LED display 14 and the various mounting methods, it is possible to use the LED display 14 for accent lighting, indicator displays, warning lamps, ambient lighting, text displays, graphic displays, lighting for roof liners and floor liners, UV (ultraviolet) or IR (infrared) LED displays for thermal imaging, UV fluorescence of coated surfaces or as backlight for flexible displays. Further, color changing LEDs may be used as status indicators or for other visual displays. Other applications for the LED displays 14 described above are brake or parking lights, motion triggered warning lights and daylight running lights.
The physical flexibility of the LED display 14 allows installing LEDs and other integrated circuit components on substantially any surface of the vehicle interior or vehicle exterior. By using a thin polyamide material as a substrate for a printed circuit board, the circuitry can conform to any surface such as a curved surface of a window, a roofline, a seat, a door or any other vehicle surface which is not typically used for installing a lighting device or a display device due to the difficulty and expense of providing a stable mounting structure. As described above, the flexible circuit board 18 is preferably encased in a durable polyurethane rubber material which is formed and sealed around the flexible circuit board 18 and the circuit components on the flexible circuit board. As a result, the LED display is a washable, durable, light-weight, moisture-resistant display which can be used as a lighting element that serves, depending on the application, as a distributed, diffuse lighting element or, alternatively, as a focused lighting element.
Further applications of the LED display 14 are fabrics that have a flexible LED display 14 woven into the fabric. It is thus possible to integrate a display for example into the seat fabric of a vehicle. Another embodiment of the display includes a display on glass or polycarbonate and uses clear circuit traces made for example from indium tin oxide (ITO). This makes it possible to integrate a display into window glass. Due to the possibility of the display to conform to curved surfaces, it is possible to include conformal displays on gear shifters, door handles, keys and other objects. A substrate for coating organic LEDs with flexible plastic circuit components to improve component flexibility is also envisioned.
The driving of the embodiment of the LED display 14 shown in
The LED display utilizes high speed shift registers in order to update the state of an arbitrary number of LEDs 16 by transmitting a sequence of bytes hundreds of times per second. The transmitted sequence of bytes represents the brightness of each LED. The brightness of each LED 16 is controlled by cycling the on-off state of the LED 16 in a waveform 34 that is generated on the basis of a recurring interrupt pattern that is used for the LED display 14.
The brightness of each LED 16 is controlled by dividing the period T of the waveform 34 controlling a specific LED 16 into 2n−1 equally timed segments, with n being an integer. For illustrative purposes, this method is outlined here for a 6-bit resolution for the brightness of the LED which results in 63 (26−1) equally timed segments. For 32/63 of the 63 (26−1) segments of the controlling waveform, the value of the most significant bit (MSB) of resolution is transmitted and drives the output for the LED. Similarly, durations of 16/63, 8/63, 4/63, 2/63 and 1/63 of the total drive waveform frequency are transmitted and drive the output of the LED, following the state of each bit of the desired LED brightness. As stated above, by increasing the frequency of the overall control waveform, the on-off cycling of the LED is not perceivable by the human eye, and the result is a solid output of variable brightness.
The method of creating the recurring interrupt pattern waveform by using a serial data control does not require any particular source to provide control over the display. Thus a dedicated controller, a PC (personal computer), a DSP (digital signal processor) or any other suitable controller may be used.
