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Patent Issued for Light Source Driving Apparatus, Light Source Driving Method, and Display Apparatus

February 26, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventor Kang, Jeong-il (Yongin-si, KR), filed on February 3, 2009, was published online on February 11, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8648790 is assigned to Samsung Electronics Co., Ltd. (Suwon-si, KR).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Apparatuses and methods consistent with the present invention relate to a light source driving apparatus, a light source driving method and a display apparatus, and more particularly, to an apparatus for driving a light source used as a backlight while displaying an image and adjusting light quantity thereof, a method thereof, and a display apparatus having the light source driving apparatus.

"A display apparatus such as a liquid crystal display (LCD) television, etc. is provided with a light source that is used as a backlight while displaying an image and achieved by a light emitting diode (LED) or the like. Such a display apparatus includes a light source driving circuit to drive the light source, and the light source driving circuit controls an electric current supplied to the light source so that the light source can emit light of desired quantity.

"As a method for adjusting the light quantity of the light source, i.e., as a dimming method, there are a pulse width modulation (PWM) dimming method that adjusts a duty ratio of an electric current to be supplied to the light source, an analog dimming method that adjusts a peak value of the current, etc. In particular, the analog dimming method is relatively superior in efficiency and heat-generation characteristics to the PWM dimming method.

"Meanwhile, the light source driving circuit includes a linear type circuit and a switching type circuit. The switching-type light source driving circuit has been widely used since it has a relatively high efficiency. FIG. 1 shows a conventional switching-type light source driving circuit. In FIG. 1, a reference numeral of 1 indicates a light source, a reference numeral of 2 indicates a light source driving circuit, and a reference numeral of 3 indicates a power source. As shown in FIG. 1, the light source driving circuit 2 includes a switching device 31 realized by a metal oxide semiconductor field effect transistor (MOSFET) or the like; an inductor 32, a diode 33, a capacitor 24, a resistor 25, and a PWM controller 26.

"However, the conventional light source driving circuit 2 has to have a reactive device such as the inductor 22 and the capacitor 24 since it is the switching type. Accordingly, there is a problem of a slow response because decrease of an output current Io relies on natural discharge of energy stored in the reactive device when to decrease the output current Io.

"For example, in the case where the analog dimming method is applied to the light source driving circuit 2, as shown in FIG. 2, the current Io flowing in the light source 1 in response to a square-wave analog dimming signal has a considerably long response delay d in a falling edge."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "Accordingly, it is an aspect of the present invention to provide a light source driving apparatus, a light source driving method and a display apparatus, which are improved in response characteristics of an output current while maintaining good efficiency and heat-generation characteristics.

"The foregoing and/or other aspects of the present invention can be achieved by providing a light source driving apparatus including: a switching driver which performs switched-mode power conversion and outputs a first current toward a light source, to control quantity of light emitted from the light source; and a current bypasser which bypasses at least a part of the first current so that a second current branched from the first current flows in the light source.

"Magnitude of the at least a part of the first current may be set to make the second current reach a predetermined target value.

"The target value of the second current may correspond to an input signal of the switching driver.

"The at least the part of the first current may correspond to difference between the first current and the target value.

"The current bypasser may include: a transistor which is connected in parallel with the light source; and a transistor controller which controls the transistor so that the at least the part of the first current flows in the transistor.

"The transistor controller may include an error amplifier to control the transistor to decrease difference between a first voltage corresponding to the second current and a second voltage corresponding to the target value.

"The current bypasser may include: a resistor which is connected in series with the light source; and a differential amplifier which detects voltage difference across the resistor and outputs the voltage difference as the first voltage.

"The switching driver may perform at least one of analog dimming and pulse width modulation (PWM) dimming to control the quantity of the light.

"The light source may include at least one light emitting diode (LED).

"The foregoing and/or other aspects of the present invention can be achieved by providing a method of driving a light source, including: performing switched-mode power conversion and outputting a first current toward the light source, to control quantity of light emitted from the light source; and bypassing at least a part of the first current so that a second current branched from the first current flows in the light source.

"Magnitude of the at least a part of the first current may be set to make the second current reach a predetermined target value.

"The target value of the second current may correspond to an input signal of the switched-mode power conversion.

"The at least the part of the first current may correspond to difference between the first current and the target value.

"The bypass of the at least the part of the first current may include bypassing the at least the part of the first current to decrease difference between a first voltage corresponding to the second current and a second voltage corresponding to the target value.

"The bypass of the at least the part of the first current may include: detecting voltage difference across a resistor which is connected in series with the light source; and outputting the voltage difference as the first voltage.

"The performing and outputting may include performing at least one of analog dimming and pulse width modulation (PWM) dimming to control the quantity of the light.

"The light source may include at least one light emitting diode (LED).

"The foregoing and/or other aspects of the present invention can be achieved by providing a display apparatus including: a video processor which processes an image; a display unit which displays the image processed by the video processor; a light source which illuminates the display unit with light; and a light source driver which drives the light source to control quantity of the light emitted from the light source, the light source driver including: a switching driver which performs switched-mode power conversion and output a first current toward a light source; and a current bypasser which bypasses at least a part of the first current so that a second current branched from the first current flows in the light source.

"Magnitude of the at least a part of the first current may be set to make the second current reach a predetermined target value.

"The target value of the second current may correspond to an input signal of the switching driver.

"The at least the part of the first current may correspond to difference between the first current output and the target value.

"The current bypasser may include: a transistor which is connected in parallel with the light source; and a transistor controller which may control the transistor so that the at least the part of the first current flows in the transistor.

"The transistor controller may include an error amplifier to control the transistor to decrease difference between a first voltage corresponding to the second current and a second voltage corresponding to the target value.

"The current bypasser may include: a resistor which is connected in series with the light source; and a differential amplifier which detects voltage difference across the resistor and outputs the voltage difference as the first voltage.

"The switching driver may perform at least one of analog dimming and pulse width modulation (PWM) dimming to control the quantity of the light.

"The light source may include at least one light emitting diode (LED)."

URL and more information on this patent, see: Kang, Jeong-il. Light Source Driving Apparatus, Light Source Driving Method, and Display Apparatus. U.S. Patent Number 8648790, filed February 3, 2009, and published online on February 11, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=47&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2301&f=G&l=50&co1=AND&d=PTXT&s1=20140211.PD.&OS=ISD/20140211&RS=ISD/20140211

Keywords for this news article include: Light-emitting Diode, Samsung Electronics Co. Ltd.

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Source: Electronics Newsweekly


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