Apparatus and method of LED short detection

Patent metadata

Field	Value
Publication number	US-9329243-B2
Application number	US-201313859573-A
Country	US
Kind code	B2
Filing date	Apr 9, 2013
Priority date	Apr 10, 2012
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

An apparatus and method for detecting a status of at least one of a plurality of light emitting diodes (LEDs), is disclosed in embodiments of the invention. The apparatus includes a first node, a second node, a voltage generator, a current source and a first comparator. The voltage generator generates an output voltage to the first external circuit via the second node. The current source provides a current to the first external circuit via the first node to generate a first node voltage. The first comparator generates a first comparison result according to the first node voltage and a reference voltage, wherein the first comparison result indicates whether the status of at least one of the LEDs is short or not.

First claim

What is claimed is:

1. An apparatus for detecting a status of at least one of a plurality of first light emitting diodes (LEDs) in a first external circuit, the apparatus comprising:
a first node and a second node, coupled to the first external circuit;
a voltage generator, to generate an output voltage to the first external circuit via the second node;
a current source, coupled to the first external circuit via the first node, to provide a current to the first external circuit via the first node to generate a first node voltage at the first node; and
a first comparator, coupled to the first node, to generate a first comparison result according to the first node voltage and a reference voltage;
wherein the first comparison result indicates whether the status of at least one of the first LEDs is short or not.

2. The apparatus of claim 1 , wherein the first external circuit further comprises a first high voltage device, coupled between the LEDs and the current source, wherein a gate of the first high voltage device receives a control voltage and the first high voltage device is on or off status according to the control voltage.

3. The apparatus of claim 2 , wherein the first external circuit further comprises a first voltage divider, coupled to the second node and the gate of the first high voltage device, to generate the control voltage.

4. The apparatus of claim 1 , wherein the first external circuit further comprises a high voltage transistor which operates in a linear region.

5. The apparatus of claim 1 , further comprising:
a third node, coupled to a second external circuit, wherein the second external circuit comprises a plurality of second LEDs connected in series; and
a second comparator, coupled to the third node, to generate a second comparison result according to a voltage at the third node and the reference voltage, wherein the second comparison result indicates whether the status of at least one of the second LEDs is short or not.

6. The apparatus of claim 1 , the voltage generator comprising:
a first transistor and a second transistor, wherein the first transistor coupled between the second transistor and the second node,
wherein a breakdown voltage of the second transistor is different from a breakdown voltage of the first transistor.

7. The apparatus of claim 6 , wherein the breakdown voltage of the second transistor is higher than the breakdown voltage of the first transistor.

8. The apparatus of claim 1 , the voltage generator comprising:
a first transistor and a second transistor, wherein the first transistor coupled between the second transistor and the second node; and
a plurality of diodes coupled in series, wherein one of the diodes is coupled to the second node.

9. The apparatus of claim 8 , wherein a breakdown voltage of the second transistor is different from a breakdown voltage of the first transistor.

10. The apparatus of claim 8 , wherein a breakdown voltage of the second transistor is higher than or equal to a breakdown voltage of the first transistor.

11. The apparatus of claim 1 , further comprising:
a mode control circuit having a plurality of operation modes; wherein the mode control circuit controls a plurality switches to perform a corresponding operation mode.

12. The apparatus of claim 11 , wherein the mode control circuit controls a first switch of the plurality of switches such that the voltage generator is coupled to the second node.

13. The apparatus of claim 12 , wherein the apparatus further comprises a second voltage divider coupled between an input of the first comparator and the first node, wherein the mode control circuit controls a third switch of the plurality of switches to allow the second voltage divider to divide the first node voltage.

14. The apparatus of claim 11 , wherein the mode control circuit controls the plurality of switches such that an internal circuit is coupled to the second node, and the voltage generator is not coupled to the second node.

15. A method for detecting a status of a first light emitting diode (LED) string, wherein the first LED string comprises a plurality of first LEDs connected in series and the first LED string is coupled to a high-voltage device, the method comprising:
providing a first current to the first LED string of a first external circuit via a first node and the high voltage device;
providing a control voltage to a control input of the high-voltage device to generate a first node voltage at the first node according to the first current flowing through the first LED string; and
generating a first comparison result according to the first node voltage and a reference voltage; wherein the first comparison result indicates whether the status of at least one of LEDs in the first LED string is short.

16. The method of claim 15 , further comprising:
controlling a first switch of the plurality of switches such that an output voltage is provided to the first external circuit in a detecting mode.

17. The method of claim 15 , further comprising:
coupling the second node to an internal circuit.

Assignees

• Realtek Semiconductor Corp

Inventors

• Lin Shu Min

Classifications

• G01R31/2632

  for testing diodes · CPC title

• G01R31/025

  Physics · mapped topic

• G01R31/44 Primary

  Testing lamps · CPC title

• G09G3/006 Primary

  Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays (testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309) · CPC title

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title