Programmable LED driver

• US 6,144,222 A
• Filed: 07/06/1999
• Issued: 11/07/2000
• Est. Priority Date: 07/09/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Ho, Rupert
• Primary Examiner(s): NGUYEN, TAN
• Application Number:
  US09/348,611
• Time in Patent Office: 490 Days
• Field of Search: 326/82, 326/83, 326/86, 326/49, 326/50, 327/53, 340/815.45, 345/46, 345/82
• US Class Current: 326/82
• CPC Class Codes: H03K 19/018578 with at least one differential stage
• CPC Class Codes: H04B 10/502 LED transmitters
• CPC Class Codes: H04B 10/564 Power control

Abstract

The present invention discloses a high speed programmable electronic current driver circuit for supplying a controlled modulated current to an LED comprising: a current driver operable over a selectable range of current levels for connection to an LED for supplying operating current to an LED; control means connected to the current driver to select the current level for operation of the current driver; transmission gating means connected to the current driver to gate high speed data signal pulses to the current driver to modulate the current of the current driver by the data signal pulses by gating the current of the current driver with the data signal pulses; whereby light output by the LED will be modulated by the data signal pulses at selectable current levels.

Claims

1. A high speed programmable electronic current driver circuit for supplying a controlled modulated current to a LED comprising:

a current driver operable over a selectable range of current levels for connection to an LED for supplying operating current to a LED;

control means connected to said current driver to select the current level for operation of said current driver;

transmission gating means connected to said current driver to gate high speed data signal pulses to said current driver to modulate the current of said current driver by said data signal pulses by gating the current of said current driver with said data signal pulses;

whereby light output by said LED will be modulated by said data signal pulses at selectable current levels.

2. The apparatus of claim 1, wherein

said current driver comprises an output current driver operable over a selectable range of current levels for driving the LED and a current amplifier for supplying current to the output current driver,

said transmission gating means is connected to the current amplifier to gate high speed data signal pulses to the current amplifier to modulate the current of the current amplifier by the data signal pulses, and

said controller means is connected to the output current driver to select the current level for operation of the current driver so that the LED will produce modulated light at a power level corresponding to the current driving the LED from the output current driver.

3. The apparatus of claim 2 wherein the current amplifier comprises a current mirror.

4. The apparatus of claim 3 wherein the current amplifier comprises a plurality of current mirrors connected in a series of stages with the output driver of one stage providing the input to the next.

5. The apparatus of claim 4 wherein said output current driver comprises a current mirror having a driver transistor and a plurality of diode connected source transistors selectably connected in parallel to each other and by gating means and to said driver transistor so that current in said selected source transistors will be mirrored in said driver transistor, the driver transistor being connectable to the LED to provide power to it.

6. The apparatus of claim 5 wherein said control means is controlled by a data transmission controller to which the LED driver is connected to selectively connect said source transistors together to control the current provided to the LED.

7. The apparatus of claim 6 including a DC voltage reference source code which gated by said transmission gating means to said current amplifier to gate a high speed data signal to said current amplifier.

8. The apparatus of claim 7 wherein said control means is adapted to control said transmission gating means with a data signal from an external data transmission controller or transceiver.

9. The apparatus of claim 8 comprising a plurality of current drivers, said current drivers being selectably operable under control of the LED driver'"'"'s controller to select which current driver a data signal will be gated to, and to select the appropriate output level of the selected current driver.

10. The apparatus of claim 9 wherein each said current amplifier and connected to output current mirror driver has selectable source transistors under control of said control means to select the appropriate number of source transistors in accordance with the requirements of an external data transceiver or controller controlling the LED driver and is adapted to gate the current driver current by data signal pulses provided by said external data transceiver or controller.

11. The apparatus of claim 9 wherein each said mirror circuits comprise FET transistor mirror circuits in which the source transistors thereof are diode-connected and have their gates connected to the gate of the corresponding mirror driver transistor.

12. The apparatus of claim 2 including a DC voltage reference source which gated by said transmission gating means to said current amplifier to gate a high speed data signal to said current amplifier.

13. The apparatus of claim 12 wherein said control means is adapted to control said transmission gating means with a data signal from an external data transmission controller or transceiver.

14. The apparatus of claim 13 comprising a plurality of current drivers, said current drivers being selectably operable under control of the LED driver'"'"'s controller to select which current driver a data signal will be gated to, and to select the appropriate output level of the selected current driver.

15. The apparatus of claim 13 wherein each said current amplifier and connected output current mirror driver has selectable source transistors under control of said control means to select the appropriate number of source transistors in accordance with the requirements of an external data transceiver or controller controlling the LED driver and is adapted to gate the current driver current by data signal pulses provided by said external data transceiver or controller.

16. The apparatus of claim 15 wherein each said mirror circuits comprise FET transistor mirror circuits in which the source transistors thereof are diode-connected and have their gates connected to the gate of the corresponding mirror driver transistor.

17. A high speed switchable electronic current driver comprising:

a plurality of current mirrors connected in a series of stages with the output driver of one stage providing the input to the next;

high speed switching means connected to the input of the first stage of said current mirrors to switch said first stage at high speed;

whereby said current driver will be switched at high speed.