Light emitting diode driver circuit, display apparatus including the same, and method for driving light emitting diode

Patent metadata

Field	Value
Publication number	US-2016309554-A1
Application number	US-201615095862-A
Country	US
Kind code	A1
Filing date	Apr 11, 2016
Priority date	Apr 20, 2015
Publication date	Oct 20, 2016
Grant date	—

Abstract

A light emitting diode (LED) driver circuit is provided. The light emitting diode (LED) driver circuit includes an LED array; an LED driving circuit configured to provide a constant current to the LED array by a switching operation of a switch element; and a driving controller configured to control the switch element using a clock signal of a preset frequency so that the constant current corresponding to a dimming signal is provided to the LED array. The driving controller varies a frequency of the clock signal in response to a signal value indicating that the dimming signal is being transitioned.

First claim

What is claimed is:

1 . A light emitting diode (LED) driver circuit, comprising:
an LED array; an LED driving circuit configured to provide a constant current to the LED array by a switching operation; and a driving controller configured to control the switching operation using a clock signal of a preset frequency so that the constant current corresponding to a dimming signal is provided to the LED array, wherein the driving controller varies a frequency of the clock signal in response to a signal value indicating that the dimming signal is being transitioned.

2 . The LED driver circuit as claimed in claim 1 , wherein the driving controller is configured to use a first clock signal of a first preset frequency preset in response to the signal value indicating that the dimming signal has a first value, and is configured to use a second clock signal of a second preset frequency higher than the first preset frequency in response to the signal value indicating that the dimming signal has a second value lower than the first value.

3 . The LED driver circuit as claimed in claim 1 , wherein the driving controller is configured to vary the frequency of the clock signal after a preset period of time in response to the signal value indicating that the dimming signal is being transitioned.

4 . The LED driver circuit as claimed in claim 3 , wherein the driving controller is configured to use a first clock signal after a first preset time in response to the signal value indicating that the dimming signal is being transitioned from a first value to a second value, which is lower than the first value, and is configured to use a second clock signal after a second preset time, which is longer than the first preset time, in response to the signal value indicating that the dimming signal is transitioned from the second value to the first value.

5 . The LED driver circuit as claimed in claim 4 , wherein the first preset time is longer than one period of the first clock signal, and
wherein the second preset time is longer than one period of the second clock signal.

6 . The LED driver circuit as claimed in claim 3 , wherein the driving controller is configured not to vary the clock signal in response to the dimming signal being subsequently transitioned before the preset time lapses.

7 . The LED driver circuit as claimed in claim 1 , wherein the driving controller comprises:
a clock generator configured to generate a clock signal of a preset frequency; a switching element configured to perform the switching operation; a comparator configured to sense whether or not a current flowing in the switch element is greater than or equal to a preset current; an RS flip-flop configured to receive the clock signal as a set signal and to receive an output of the comparator as a reset signal; and an AND gate configured to perform an AND operation of an output of the RS flip-flop and the dimming signal and configured to provide the result of the AND operation to the switching element.

8 . The LED driver circuit as claimed in claim 7 , wherein the clock generator comprises:
a reference voltage outputter configured to output a reference voltage corresponding to a first preset frequency; a voltage controlled oscillator configured to generate the clock signal using the reference voltage; a gain configured to bypass the reference voltage to the voltage controlled oscillator in response to the signal value indicating that the dimming signal has a first value, and multiply a preset gain value with the reference voltage and provide the result to the voltage controlled oscillator in response to the signal value indicating that the dimming signal has a second value lower than the first value; and a delayer configured to delay the dimming signal by a preset time and provide the delayed dimming signal to the gain.

9 . The LED driver circuit as claimed in claim 7 , wherein the clock generator comprises:
a reference voltage outputter configured to output a reference voltage corresponding to a first preset clock frequency; a voltage controlled oscillator configured to generate the clock signal using the reference voltage; a voltage selector configured to bypass the reference voltage to the voltage controlled oscillator in response to the signal value indicating that the dimming signal has a first value, and to provide a second reference voltage corresponding to a second preset frequency to the voltage controlled oscillator in response to the dimming signal having a second value lower than the first value; and a delayer configured to delay the dimming signal by a preset time and to provide the delayed dimming signal to the voltage selector.

10 . The LED driver circuit as claimed in claim 7 , wherein the clock generator comprises:
a reference voltage outputter configured to output a reference voltage corresponding to a first preset frequency; a voltage controlled oscillator configured to generate the clock signal using the reference voltage; a clock selector configured to bypass and output the clock signal generated by the voltage controlled oscillator to the RS flip-flop in response to the signal value indicating that the dimming signal has a first value, and to provide an output of a second oscillator generating a second clock signal of a second preset frequency to the RS flip-flop in response to the signal value indicating that the dimming signal has a second value lower than the first value; and a delayer configured to delay the dimming signal by a preset time and to provide the delayed dimming signal to the clock selector.

11 . The LED driver circuit as claimed in claim 7 , wherein the clock generator comprises:
a reference voltage outputter configured to output a reference voltage corresponding to a resistance value of a connected resistor; a voltage controlled oscillator configured to generate the clock signal using the reference voltage and provide the generated clock signal to the RS flip-flop; a resistor selector configured to connect a first resistor having a first resistance value corresponding to a first preset clock frequency to the reference voltage output in response to the signal value indicating that the dimming signal has a first value, and connect a second resistor having a second resistance value corresponding to a second preset frequency to the reference voltage output in response to the signal value indicating that the dimming signal has a second value lower than the first value; and a delayer configured to delay the dimming signal by a preset time and to provide the delayed dimming signal to the resistor selector.

12 . The LED driver circuit as claimed in claim 8 , wherein the delayer comprises:
a first resistor configured to receive the dimming signal through a first end thereof; a first diode configured to have an anode connected to a second end of the first resistor; a second resistor configured to be connected to said first end of the first resistor and configured to receive the dimming signal; a second diode configured to have a cathode connected to the second end of the second resistor; and a capacitor configured to be commonly connected to a cathode of the first diode and an anode of the second diode.

13 . The LED driver circuit as claimed in claim 12 , wherein a first resistance value of the first resistor and a second resistance value of the second resistor are different from each other.

14 . The LED driver circuit as claimed in claim 1 , wherein the LED driving circuit comprises:
a power source configured to provide power; a switching element configured to perform the switching operation

Assignees

• Samsung Electronics Co Ltd

Inventors

• Kang Jeong-Il

Classifications

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• G09G3/36

  using liquid crystals · CPC title

• G09G2320/0626

  for control of overall brightness · CPC title

• H05B33/0815 Primary

  Electricity · mapped topic