Optical display device and method of operating an optical display device

• US 6,239,716 B1
• Filed: 06/17/1999
• Issued: 05/29/2001
• Est. Priority Date: 06/25/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Maile, Markus, Pross, Gerhard, Seher, Jens-Peter
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US09/335,418
• Time in Patent Office: 712 Days
• Field of Search: 340/815.4, 340/525, 340/815.45, 340/321, 345/82, 345/183, 362/800, 315/200 A
• US Class Current: 340/815.4
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/0272 Details of drivers for data electrodes, the drivers communicating data to the pixels by means of a current
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 2330/10 Dealing with defective pixels
• CPC Class Codes: G09G 3/14 Semiconductor devices, e.g. diodes
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An optical display device has a set of LEDs arranged in a matrix and includes control circuitry which acts as a controllable current source and as controllable voltage sources. The control circuitry enables a constant current to be applied for each LED, and respective voltages to be established accordingly. Due to the additional logic circuitry which deliver different clock pulses at different frequencies for cyclic switching of at least one LED, signals that are visible to the human eye are generated and at the same time signals that are not visible to the human eye are also generated. The signals that are not visible are digitally coded and transmitted for appropriately adapted reading devices. Thus additional information for a variety of purposes can be made available, especially in the communications and traffic area, simultaneously with the lighting up of the LEDs. This refers in particular to traffic control systems, diagnosis and monitoring. An optical display device designed in this way permits a design, for example, as a taillight, brake light, flashing indicator light and the like in a motor vehicle or with other traffic and communications means and also in equipment in production facilities while permitting favorable production at the same time due to reduced fault in assembly and ease of adjustment of the light values.

Claims

1. An optical display device with a set of LEDs which are connected in series or in parallel, said optical display device comprising:

a set of LEDs comprising a matrix, said matrix comprising at least one column of at least one LED, with the LEDs in each column being connected in series and the columns being connected in parallel,

first control circuit means which are connected to at least each column and act as a controllable current source to set a constant current through the corresponding column(s),

logic circuit means for delivering different clock pulses with different frequencies to the first control circuit means for cyclic switching of at least one LED to generate signals that are visible to the human eye and at the same time signals that are not visible to the human eye, and

second control circuit means connected to the matrix and the first control circuit means, for acting as a controllable voltage source to adjust the voltage across the LEDs as a function of the current injected.

2. An optical display device according to claim 1, wherein for minimal power consumption, the second control circuit means set the lowest possible voltage required for proper functioning of the LEDs.

3. An optical display device according to claim 1, wherein each LED can be short-circuited by a switch.

4. An optical display device according to claim 1, wherein the logic circuit means deliver a signal when there is a failure of one or more LEDs.

5. An optical display device according to claim 1, wherein the logic circuit means switch the LEDs cyclically at a frequency that visible to the human eye to set the brightness in day and night operation.

6. An optical display device according to claim 1, wherein the logic circuit means cyclically switch the LEDs in a digitally coded manner to transmit information to a corresponding receiver.

7. An optical display device according to claim 1, wherein the LEDs for a light point comprise three LEDs in different colors, namely red, green and blue, and the logic circuit means drive them according to a desired color.

8. A method of operating an optical display device with a set of LEDs arranged in series or in parallel, said method comprising the steps of:

setting a constant current through said LEDs;

cyclically switching said LEDs by a logic control means at a frequency that is not visible to the human eye and at the same time delivering an optical signal visible to the human eye, and emitting coded digital signals for suitable adapted reading devices; and

controlling the voltage across the LEDs as a function of the current infected.

9. A method according to claim 8, wherein when several LEDs are connected in series, a faulty LED is bridged when there is a failure in one or more LEDs, and the current is kept constant in the series.

10. A method according to claim 8, wherein luminous power of the LEDs is varied to adapt it to ambient brightness by cyclically switching the LEDs on and off.