LED driving device, illuminator, and liquid crystal display device

Patent metadata

Field	Value
Publication number	US-10068511-B2
Application number	US-201715596789-A
Country	US
Kind code	B2
Filing date	May 16, 2017
Priority date	Jul 11, 2011
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

The present invention provides a light emitting diode (LED) driving device as a semiconductor device, which comprises: a direct current/direct current (DC/DC) controller, for controlling an output segment that is used to generate an output voltage from an input voltage and supply the output voltage to an LED; an output current driver, for generating an output current of the LED; and an LED short-circuit detection circuit, for monitoring a cathode voltage of the LED to perform an LED short-circuit detection, wherein the LED short-circuit detection circuit controls whether an action is performed or not according to a short-circuit detection enable signal input from outside the LED driving device.

First claim

What is claimed is:

1. A light emitting diode (LED) driving device, comprising:
a direct current/direct current (DC/DC) controller configured to control an output segment that is used to generate an output voltage from an input voltage and supply the output voltage to an LED;
an output current driver configured to generate an output current of the LED; and
an LED short-circuit detection circuit configured to monitor a cathode voltage of the LED to perform an LED short-circuit detection;
a short-circuit detection signal input terminal arranged to input a short-circuit detection enable signal, the short-circuit detection enable signal is used for controlling whether an LED short-circuit detection action is performed or not,
wherein the LED short-circuit detection circuit is operable to control whether or not an action is performed according to the short-circuit detection enable signal input from outside the LED driving device,
wherein the LED short-circuit detection circuit comprises a comparator operable to compare the cathode voltage of the LED and a predetermined threshold voltage, and operable to control whether or not the action is performed according to the short-circuit detection enable signal.

2. The LED driving device according to claim 1 , wherein the LED driving device is operable to supply the output current to the LED without performing the LED short-circuit detection if the LED short-circuit detection circuit makes the action invalid according to the short-circuit detection enable signal.

3. The LED driving device according to claim 1 , wherein the LED short-circuit detection circuit further comprises a logic gate operable to mask an output signal of the comparator according to the short-circuit detection enable signal.

4. An illuminator, comprising:
the LED driving device according to claim 1 ;
the output segment; and
the LED.

5. A liquid crystal display (LCD) device, comprising:
an LCD panel; and
the illuminator according to claim 4 operable to illuminate the LCD panel from the back.

6. The illuminator according to claim 4 , wherein the LED comprises a plurality of LED rows, and each of the plurality of the LED rows comprises a plurality of LEDs connected in series, and the output voltage generated by the DC/DC controller determines the cathode voltages of the LED rows, and the cathode voltages of the LED rows equal to a maximized sum of the threshold voltages of the plurality of LED rows.

7. The LED driving device according to claim 1 , further comprising an external terminal to receive the cathode voltage of the LED, wherein the output current driver and the LED short-circuit detection circuit are connected to the external terminal.

8. The LED driving device according to claim 1 , wherein the DC/DC controller, the output current driver, and the LED short-circuit detection circuit are integrated.

9. A light emitting diode (LED) driving device, comprising:
a direct current/direct current (DC/DC) controller configured to control an output segment that is used to generate an output voltage from an input voltage and supply the output voltage to an LED;
an output current driver configured to generate an output current of the LED; and
an LED short-circuit detection circuit configured to monitor a cathode voltage of the LED to perform an LED short-circuit detection,
wherein the LED short-circuit detection circuit is operable to compare the cathode voltage of the LED and a predetermined threshold voltage, and
wherein the output current driver and the LED short-circuit detection circuit are connected in parallel.

10. The LED driving device according to claim 9 , further comprising a short-circuit detection signal input terminal arranged to input a short-circuit detection enable signal, the short-circuit detection enable signal being used for controlling whether an LED short-circuit detection action is performed or not.

11. The LED driving device according to claim 10 , wherein the LED short-circuit detection circuit is operable to control whether or not an action is performed according to the short-circuit detection enable signal input from outside the LED driving device.

12. The LED driving device according to claim 10 , wherein the LED short-circuit detection circuit comprises a comparator operable to compare the cathode voltage of the LED and the predetermined threshold voltage, and operable to control whether or not the action is performed according to the short-circuit detection enable signal.

13. The LED driving device according to claim 12 , wherein the LED short-circuit detection circuit further comprises a logic gate operable to mask an output signal of the comparator according to the short-circuit detection enable signal.

14. The LED driving device according to claim 9 , further comprising an external terminal to receive the cathode voltage of the LED, wherein the output current driver and the LED short-circuit detection circuit are connected to the external terminal.

15. The LED driving device according to claim 9 , wherein the LED driving device is operable to supply the output current to the LED without performing the LED short-circuit detection if the LED short-circuit detection circuit makes the action invalid according to the short-circuit detection enable signal.

16. The LED driving device according to claim 9 , wherein the DC/DC controller, the output current driver, and the LED short-circuit detection circuit are integrated.

Assignees

• Rohm Co Ltd

Inventors

• Kanemitsu Ryosuke
• Nakayama Masaaki

Classifications

• H05B45/50

  responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits · CPC title

• H05B45/46

  having LEDs disposed in parallel lines · CPC title

• H05B45/395

  Linear regulators · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• G02F1/133603

  with LEDs · CPC title