METHOD AND DEVICE FOR LED CHANNEL MANAGMENT IN LED DRIVER

• US 20090315481A1
• Filed: 01/30/2009
• Published: 12/24/2009
• Est. Priority Date: 06/23/2008
• Status: Active Grant

• Current Assignee: SK Hynix Inc.
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Zhao, Bin
• Granted Patent: US 8,035,314 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/38 using boost topology

Abstract

Disclosed are example open channel detection techniques at a light emitting diode (LED) driver of an LED system. The LED driver does not enable its LED channels before normal operation so as to inhibit current flow through the LED channels during start-up. While the LED channels are disabled, the LED driver compares the voltages at the LED channel inputs with a predetermined voltage to determine whether an operational LED string of an associated LED panel is connected to the LED channel. In the event that an LED channel is determined to be an “open” channel, the LED driver further disables the LED channel for the following normal operational mode. Otherwise, if the LED channel is determined to be connected to an operational LED string, the LED driver enables the LED channel for the normal operational mode, during which the LED channel can be selectively activated for light output subject to display data for the LED panel.

Claims

1. A method comprising:

providing a light emitting diode (LED) driver comprising a voltage source having an output configured to couple to a head end of each of one or more LED strings of a LED panel and a plurality of LED channels, each LED channel comprising an LED channel input configured to couple to a tail end of a corresponding LED string; and

for a first mode of the LED driver;

configuring each LED channel to inhibit current flow through the LED channel during the first mode;

configuring the voltage source to provide a predetermined first voltage at the output; and

determining, for each LED channel, whether the LED channel is coupled to an operative LED string based on a voltage at the LED channel input of the LED channel.

2. The method of claim 1, wherein each LED channel includes a corresponding current regulator coupled to the corresponding LED channel input, and wherein configuring each LED channel to inhibit current flow comprises disabling the corresponding current regulator.

3. The method of claim 1, wherein configuring the voltage source to provide an output voltage having the predetermined first voltage comprises increasing a voltage at the output until the voltage at the output is equal to the predetermined first voltage.

4. The method of claim 1, wherein determining whether the LED channel input is coupled to an operative LED string comprises:

determining the LED channel input is coupled to an operative LED string in response to determining the voltage at the LED channel input is greater than a predetermined second voltage; and

determining the LED channel input is not coupled to an operative LED string in response to determining the voltage at the LED channel input is not greater than the predetermined second voltage.

5. The method of claim 1, wherein the predetermined first voltage is less than an over-voltage protection threshold of the LED driver.

6. The method of claim 1, further comprising:

for a second mode of the LED driver subsequent to the first mode;

configuring the voltage source to provide a second voltage at the output;

for each LED channel determined as not connected to an operational LED string, configuring the LED channel to inhibit current flow through the LED channel; and

for each LED channel determined as connected to an operational LED string, configuring the LED channel to permit current flow through the LED channel responsive to display data associated with the LED panel.

7. The method of claim 6, further comprising:

for the second mode, controlling the voltage source to adjust an output voltage using tail voltages of LED channels determined as connected to an operational LED string and without using tail voltages of LED channels determined as not connected to an operational LED string.

8. The method of claim 1, wherein providing the LED driver comprises providing an integrated circuit (IC) device comprising the LED driver, and wherein the IC device comprises a plurality of input pins, each input pin coupled to a corresponding LED channel input and configured to couple to a tail end of a corresponding LED string.

9. A system comprising:

a light emitting diode (LED) driver comprising;

a voltage source having an output configured to couple to a head end of each of one or more LED strings of a LED panel; and

a plurality of LED channels, each LED channel comprising an LED channel input configured to couple to a tail end of a corresponding LED string;

a LED channel detector configured to;

for a first mode of the LED driver;

configure each LED channel to inhibit current flow through the corresponding LED channel input during the first mode;

configure the voltage source to provide a predetermined first voltage at the output; and

determine, for each LED channel input, whether the LED channel is coupled to an operative LED string based on a voltage at the LED channel input.

10. The system of claim 9, wherein:

each LED channel comprises a current regulator coupled to the corresponding LED channel input; and

the LED channel detector is configured to configure each LED channel to inhibit current flow through the corresponding LED channel input by disabling the corresponding current regulator.

11. The system of claim 9, wherein the LED channel detector is configured to configure the voltage source to provide an output voltage having the predetermined first voltage by configuring the voltage source to increase a voltage at the output until the voltage at the output is equal to the predetermined first voltage.

12. The system of claim 9, wherein the LED channel detector is configured to determine whether the LED channel input is coupled to an operative LED string by:

determining the LED channel input is coupled to an operative LED string in response to determining the voltage at the LED channel input is greater than a predetermined second voltage; and

determining the LED channel input is not coupled to an operative LED string in response to determining the voltage at the LED channel input is not greater than the predetermined second voltage.

13. The system of claim 12, wherein the LED channel detector comprises:

a comparator having a first input to receive the predetermined second voltage, a second input coupled to the LED channel input of an LED channel, and an output; and

a detect controller comprising an input coupled to the output of the comparator, the detect controller configured to selectively enable or disable the LED channel based on a state of the output of the comparator.

14. The system of claim 9, wherein the predetermined first voltage is less than an over-voltage protection threshold of the LED driver.

15. The system of claim 9, further comprising:

a LED data/timing controller configured to;

for a second mode of the LED driver subsequent to the first mode;

configure the voltage source to provide a second voltage at the output; and

for each LED channel input determined to be connected to an operational LED string, selectively configure the LED channel to permit current flow through the corresponding LED channel input responsive to display data associated with the LED panel; and

wherein the LED channel detector is configured to;

for the second mode;

for each LED channel input determined as not connected to an operational LED string, configure the LED channel to inhibit current flow through the corresponding LED channel input.

16. The system of claim 15, wherein the LED driver is configured to:

for the second mode, control the voltage source to adjust an output voltage using tail voltages of LED channels determined as connected to an operational LED string and without using tail voltages of LED channels determined as not connected to an operational LED string.

17. The system of claim 9, the LED driver is an integrated circuit (IC) device comprising a plurality of input pins, each input pin coupled to a corresponding LED channel input and configured to couple to a tail end of a corresponding LED string.

18. A system comprising:

a light emitting diode (LED) panel; and

a LED driver comprising an output coupled to the LED panel, a first LED channel coupled to a tail end of an operative LED string, and a second LED channel that is not coupled to a tail end of an operative LED string, the LED driver configured to;

determine the first LED channel is coupled to an operative LED string based on a first voltage at an input of the first LED channel input while the LED channel is configured to inhibit current flow during a start-up mode; and

determine the second LED channel is not coupled to an operative LED string of the LED panel based on a second voltage at an input of the second LED channel while the LED channel is configured to inhibit current flow during the start-up mode.

19. The system of claim 18, wherein the LED driver further is configured to:

inhibit flow of current at the second LED channel input during an operational mode responsive to determining the second LED channel is not coupled to an operative LED string; and

permit flow of current at the first LED channel input during the operational mode responsive to determining the first LED channel is coupled to the operative LED string.

20. The system of claim 18, wherein the LED driver further is configured to provide a predetermined voltage at the output coupled to the LED panel during the start-up mode, the predetermined voltage being less than an over-voltage protection threshold of the LED driver.