GB2389229A

GB2389229A - A light emitting diode

Info

Publication number: GB2389229A
Application number: GB0212251A
Authority: GB
Inventors: Lee Robinson
Original assignee: Roke Manor Research Ltd
Current assignee: Roke Manor Research Ltd
Priority date: 2002-05-28
Filing date: 2002-05-28
Publication date: 2003-12-03
Also published as: EP1510109A1; WO2003101154A1; GB0212251D0; AU2003242572A1

Abstract

A light emitting diode 1 includes an integrated circuit controller 4 encapsulated with a light emitting die 2. The control IC includes a programmable memory which holds its address. The address can be programmed during manufacture or at a later stage. The controller responds to an addressed command on the data signal. The command contains information on the desired output of the device, such as on/off, intensity and colour, it can also contain a new address for re-programming the device. The diode has two, three or four leads 6 for power, ground, clock and data signals. The clock and data may be combined for a three lead device or combined with the power supply for a two lead device. This simplifies the connections required compared to a conventional array of LEDs. Connection 8 provides a ground connection for the controller and connection 5 proves the output to the LED die. The LED can also be mounted on the control IC with different connections.

Description

f A Light Emitting Diode This invention relates to a light emitting diode.

5 Light emitting diodes (LED) are solid-state devices which are used as light sources in displays. They are typically two lead devices which when driven by a suitable supply may be made to emit light. A problem occurs with the use of such LEDs when it is desired to selectively energise one or some of those in the display. In order to cater for selective energisaton it is necessary to provide a multiplicity of lo connecting wires.

The present invention arose from a realization by the inventor that it might be possible to overcome or at least alleviate some of the drawbacks of prior arrangements.

5 According to the invention there is provided a light emitting diode Including a light emitting die and a controller for the die which controller being responsive to an address on a control hne to selectively operate the light emitting die.

By operate it is meant to control an aspect of the LED's function which could 20 include for example, on or off, an increase or decrease in intensity or a variation to the colour or wavelength of the radiation produced.

Specific embodiments of the light emitting diode will now be described by way of example only with reference to the drawings in which: 2s Figures I to 4 show longitudinal sections through different embodiments of the invention; and Figure 5 shows a control signal structure.

( In the description of the embodiments like components are given the same

reference numerals. As is shown In figure 1, a light emitting diode (led) 1 comprises a light emitting diode die 2 of AllnGaP material bonded to a metal cathode leg 3 (other materials may be used), a CMOS control IC 4 wired to the die 2 by a connection 5 and s metal legs 6. The components are encapsulated in an epoxy encapsulation compound 7 of standard type to produce a unitary component. The epoxy compound may be clear or coloured as required for the particular application.

The first embodiment shown in figure 1 has three metals legs 6 which protrude lo beyond the encapsulation. The first leg 6a is a ground connection to the led die 2. The second leg 6b is a data and clock connection to the control IC 4 and the third leg 6c is a power connection to the control IC 4. A further connection 8 to the control IC 4 is provided between the metal leg and the control 1C 4. This further connection connects the control 1C 4 to the ground to ensure that the control IC is provided with a complete 5 power connection between supply and ground.

In the second embodiment two metal legs are provided. The first of these 6a is identical to that disclosed in the first embodiment. The second leg 6d is a connection to power, clock and data. The third embodiment shown in figure 3 has the same two-leg 20 arrangement as the figure 2 embodiment. However, the controller 1C 4 is mounted on the metal cathode underneath the led die 2. Thus in this embodiment there is a direct connection to the ground leg 6 a and a wire link 10 from the dower clock data leg 6d to the control JC 4.

25 The last embodiment is provided with four metal legs. The first leg 6a provides a connection to ground. The second leg providing a connection to data. The third]cg 6f providing a connection to a clock and the fourth leg 6c providing a connection to power. The legs be, f and g are connected to the control IC4 and a power connection made to the led die 2 by wire link 5.

( In essence all the embodiments provide a led controller and a led die in one encapsulation. The way in which the control IC 4 operates to control the LED will now be 5 described. This description is applicable to all the embodiments.

The control 1C includes a programmable memory area which in use holds binary value of its address. The address is programmed during manufacture although it may also be possible to make it programmable at a later stage for example in use or lo during installation of the led into other equipment such as a display. In order to instruct the control IC and hence to affect the operation of the led die itself a data signal Is applied to a data bus (not shown) to which the data leg is connected.

The data signal 50 is shown in figure 5 and comprises a number of fields. The

5 first field 51 is a start field and the last field 52 is a stop field. These include a

sequence to indicate that a message starts and ends to enabic a control IC to Identify the messages In a stream of such messages. The second field 53 is a destination address

field. This field contains the address of the Intended LED control IC. A number of

further data fields 54 are provided which may include error checking information or

20 other signalling data. The next significant field is an address update field 55. This

field contains a new address to be used by the control IC If the following program set

field 56 Is set to 1. This enables the re-programming of each led if required. Field is

the on-off field. If the contents of this field are a I then the control IC switches the

LED die on. If zero the LED die is switched off.

2s The other data fields enable other control functions such as the setting of other

led die properties. For example it may be possible to thereby control the output intensity or the wavelength or colour of the light emitted.

30 The fourth embodiment is controlled In an asynchronous manner requiring the extra leg for the external clock to the control IC.

Claims

/ Claims

Claim I. A light emitting diode including a light emitting die and a controller for the S die which controller being responsive to an address on a control line to selectively operate the light emitting die.
Claim 2. A light emitting diode as claimed in claim 1 wherein the controller is provided as an integrated circuit.
Claim 3. A light emitting diode as claimed in claim 1 or claim 2 wherein the light emitting die is provided with legs to facilitate electrical connection.
Claim 4. A light emitting die as claimed in claim 3 wherein at least one of the legs 15 provides in use a data connection.
Claim 5. A light emitting diode as claimed in anyone of claims I to 4 wherein the light emitting die is encapsulated.

20 Claim
6. A light emitting diode as claimed in claim 5 wherein the controller is encapsulated with the die.
Claim 7. A light emitting diode as claimed in any preceding claim wherein the legs provide a ground, a power, a clock and a data connection.
Claim 8. A light emitting diode substantially as hereinbefore described with reference to, and as illustrated by, figure I or figure 2 or figure 3 or figure 4.