The patent's inventors are Wen, Chun-Kuei (Hsinchu, TW); Kuo, Shih-Chieh (Taipei County, TW); Chen, Che-Hsien (
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention generally relates to a light source system, in particular, to a light source system and a driving method for light emitting diodes (LEDs).
"Recently, with the vigorous development of semiconductor technology, portable electronic products and flat panel display (FPD) products also rise. Among many types of the FPDs, the liquid crystal display (LCD) immediately becomes the mainstream of various display products due to advantages such as low-voltage operation, radiation-free line scattering, a light weight, and a small volume. Generally, an LCD panel itself does not have the characteristic of light-emission, and thus it is necessary to dispose a backlight module below the LCD panel, so as to provide the required light (backlight) source for the LCD panel.
"The conventional backlight module may be roughly divided into two categories: the backlight module formed by cold cathode fluorescent lamps (CCFLs), and the backlight module formed by LEDs. As the LED backlight module is capable of improving the color gamut of the LCD, currently most panel manufacturers replace the CCFL backlight module with the LED backlight module.
"The LED backlight module has a plurality of parallel LED strings, and each LED string is formed by a plurality of LEDs connected in series. In practice, each LED string is operated under a direct current (DC) output voltage provided by a boost circuit. Besides, a driver for driving the LED strings generates a plurality of pulsation current signals in response to a setting signal provided by a system terminal, so as to respectively drive the LED strings. Specifically, both the frequency and the duty cycle of each pulsation current signal generated by the driver are in accordance with the frequency and the duty cycle of the setting signal provided by the system terminal.
"However, as the frequency of the setting signal provided by the system terminal is limited within 200 Hz to 20 KHz, an output capacitor (Cout) of the boost circuit generates resonance with the print circuit board (PCB) in response to the pulsation of the pulsation current signals generated by the driver, so as to produce acoustic noises. Moreover, if the frequency of the setting signal provided by the system terminal (that is, the frequency of the pulsation current signal) is close to the multiple of the frame rate of the LCD (for example, 240 Hz, 300 Hz, etc.), it is more likely that unnecessary oblique or horizontal stripes (i.e. wave noises) are generated in images displayed by the LCD, which may affect the quality of the frame."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Accordingly, the present invention is directed to a light source system and a method for driving LEDs so as to effectively solve the problems in the prior art.
"In an embodiment, the present invention provides a light source system, which includes an LED module and a driving unit. The LED module has a plurality of LED strings operated under a DC output voltage. The driving unit is coupled to the LED module, and used for providing the DC output voltage by adopting a boost means and generating a plurality of pulsation current signals according to a setting signal so as to respectively drive the LED strings. The frequencies of the pulsation current signals are higher than a predetermined frequency.
"In another embodiment, the present invention further provides a method for driving LEDs, applicable to driving a plurality of LED stings, which includes providing a DC output voltage by adopting a boost means so as to enable the LED strings to be operated under the DC output voltage; and generating a plurality of pulsation current signals according to a setting signal so as to respectively drive the LED strings. The frequencies of the pulsation current signals are higher than a predetermined frequency.
"In an embodiment of the present invention, the frequencies of the pulsation current signals may be the same or different from each other.
"In an embodiment of the present invention, the frequency of each pulsation current signal has a multiple relation with the predetermined frequency, and the multiple relation may be greater than or equal to an integral or a non-integral multiple of one.
"In an embodiment of the present invention, the predetermined frequency is a highest audio frequency in an audible acoustic wave range.
"Based on the above descriptions, the present invention mainly designs the frequencies of the pulsation current signals for driving the respective LED strings into frequencies higher than the audible acoustic wave range (that is, 20 Hz to 20 KHz). Therefore, the intensities of the acoustic noises produced by the resonance between the output capacitor used in the adopted boost means and the PCB can be significantly suppressed. Moreover, as the frequencies of the pulsation current signals for driving the LED strings may also be designed into different values, unnecessary oblique or horizontal stripes (i.e. wave noises) can be avoided in the images displayed by the LCD if the light source system of the present invention is applied in the LCD system.
"It should be understood that the above descriptions and the following specific implementations are only for illustration and explanation, and are not intended to limit the claimed scope of the present invention."
For the URL and additional information on this patent, see: Wen, Chun-Kuei; Kuo, Shih-Chieh; Chen, Che-Hsien; Huang, Hung-Min. Light Source System and Method for Driving Light Emitting Diodes. U.S. Patent Number 8618738, filed
Keywords for this news article include: Electronics, Light-emitting Diode,
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