1. Field of the Invention
The present disclosure relates to boost circuit technology, and more particularly to a boost circuit having one input voltage and a plurality of output voltages, the LED backlight driving circuit with the boost circuit, and the liquid crystal device (LCD) with the LED backlight driving circuit.
2. Discussion of the Related Art
With the technology revolution, backlight technology of LCDs has been developed. Typical LCDs adopt cold cathode fluorescent lamps (CCFL) as the backlight sources. However, as the CCFL backlight is characterized by attributes including low color reduction ability, low lighting efficiency, high discharging voltage, bad discharging characteristics in low temperature, and also, the CCFL needs a long time to achieve a stable gray scale, LED backlight source is a newly developed technology. For LCDs, the LED backlight source is arranged opposite to the liquid crystal panel so as to provide the light source to the liquid crystal panel. The LED backlight source includes at least one LED string, and each of the LED strings includes a plurality of LEDs serially connected.
The duty ratio of the square-wave signals (S) of the above driving circuit is d. The relationship between the output voltage (Vo) and the input voltage (Vin) is:
In addition to the high voltage needed for the LED string, the driving circuits usually need more converted voltage. For instance, the voltage needed for the operations of the driving circuit (“VCC”), the reference voltage (Vref), and so on. Currently, a single boost line can only obtain one output voltage.
In order to overcome the above problem, the LED backlight driving circuit includes a boost circuit having one input voltage and a plurality of output voltages.
In one aspect, a boost circuit includes: an inductor (L), a MOS transistor (Q), and a number “n” of switch components (Q1-Qn), a first end of the inductor (L) receives an input voltage (Vin), and a second end of the inductor (L) connects to a drain of the MOS transistor (Q), a source of the MOS transistor (Q) is electrically grounded, a gate of the MOS transistor (Q) is driven by one square-wave signals (S), the first ends of the number “n” of switch components (Q1-Qn) respectively connects to the second end of the inductor (L), the second ends of the number “n” of switch components (Q1-Qn) respectively outputs a number “n” of output voltages (Vo1-Von), the number “n” of switch components (Q1-Qn) are driven by a number “n” of square-wave signals (S1-Sn); wherein a duty ratio of the square-wave signals (S) is d, the duty ratios of the square-wave signals (S1-Sn) are d1-dn, before a turn-off time of each period of the MOS transistor (Q), the number “n” of square-wave signals (S1-Sn) are driven by a number “n” of switch components (Q1-Qn) in turn, and d1+d2+d3+ . . . +dn=1−d; and wherein n is an integer greater than one.
Wherein the number “n” of switch components (Q1-Qn) are MOS transistors, the drain of each MOS transistors (Q) respectively connects to the second ends of the inductor (L), the source of each MOS transistors (Q) respectively outputs the number “n” of output voltages (Vo1-Von), and the gate of the MOS transistors (Q) are respectively driven by the number “n” of square-wave signals (S1-Sn).
Wherein n is in a range between 2 and 4.
wherein n equals to 2.
In another aspect, a LED backlight driving circuit includes a boost circuit and at least one LED loading. The boost circuit includes: an inductor (L), a MOS transistor (Q), and a number “n” of switch components (Q1-Qn), a first end of the inductor (L) receives an input voltage (Vin), and a second end of the inductor (L) connects to a drain of the MOS transistor (Q), a source of the MOS transistor (Q) is electrically grounded, a gate of the MOS transistor (Q) is driven by one square-wave signals (S), the first ends of the number “n” of switch components (Q1-Qn) respectively connects to the second end of the inductor (L), the second ends of the number “n” of switch components (Q1-Qn) respectively outputs a number “n” of output voltages (Vo1-Von), the number “n” of switch components (Q1-Qn) are driven by a number “n” of square-wave signals (S1-Sn), one of the number “n” of output voltages (Vo1-Von) supplies a driving voltage to the LED loading, and other output voltages supply the driving voltages to other loadings of the LED backlight driving circuit; wherein a duty ratio of the square-wave signals (S) is d, the duty ratios of the square-wave signals (S1-Sn) are d1-dn, before a turn-off time of each period of the MOS transistor (Q), the number “n” of square-wave signals (S1-Sn) are driven by a number “n” of switch components (Q1-Qn) in turn, and d1+d2+d3+ . . . +dn=1−d; and wherein n is an integer greater than one.
Wherein the LED loading is a LED string or at least two LED strings connected in parallel, and each of the LED string comprises a plurality of LEDs serially connected.
In another aspect, a liquid crystal device includes a liquid crystal panel and a backlight module for providing a display light source to the liquid crystal panel such that the liquid crystal panel is capable of displaying images. The backlight module comprises a LED backlight source having the above LED backlight driving circuit.
In view of the above, the LED backlight driving circuit includes one boost circuit having one input voltage and a plurality of output voltages. Only one energy-saving component is adopted, but two or more output voltages may be obtained. Not only the LED string is supplied with the voltage, but also other loadings of the driving circuit may be supplied with the operational voltage. In this way, it is not needed to adopt large-scale energy-saving component, i.e., inductor, such that the cost of the product is reduced.
Embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.
As shown in
The driving circuit of the LED backlight source includes a boost circuit for converting an input voltage to a plurality of output voltages so as to provide operational voltages to a plurality of loadings, such as the LED string, the operational voltage (Vcc), the reference voltage (Vref), and so on, of the driving circuit.
As shown in
In the embodiment, the number “n” of switch components (Q1-Qn) are MOS transistors. The drain of each MOS transistors (Q) respectively connects to the second ends of the inductor (L). The source of each MOS transistors (Q) respectively outputs the number “n” of output voltages (Vo1-Von). The gate of the MOS transistors (Q) are respectively driven by the number “n” of square-wave signals (S1-Sn). The source of each MOS transistors (Q) are electrically grounded respectively via one capacitor (C1-Cn).
The duty ratio of the square-wave signals (S) of the above boost circuit is d. The duty ratio of the square-wave signals (S1-Sn) are d1-dn. Before a turn-off time of each period of the MOS transistor (Q), the number “n” of square-wave signals (S1-Sn) are driven by the number “n” of switch components (Q1-Qn) in turn. In addition, d1+d2+d3+ . . . +dn=1−d. The waveform diagram of the square-wave signals (S1-Sn) is shown as
When adopting the above boost circuit in LED backlight driving circuits, the number “n” of the switch components may be determined in accordance with the operational voltages of the backlight driving circuits. Preferably, n is in a range between 2 and 4.
As shown in
The duty ratio of the square-wave signals (S) of the above LED backlight driving circuit t is d. The duty ratio of the square-wave signals (S1, S2) are respectively d1 and d2. Before a turn-off time of each period of the MOS transistors (Q1, Q2), the square-wave signals (S1, S2) are driven by MOS transistors (Q1, Q2) in turn. In addition, d1+d2=1−d. The output voltage (Vo1, Vo2) and the input voltage (Vin) satisfy the equations below:
In the embodiment, the LED loading of
In view of the above, the LED backlight driving circuit includes one boost circuit having one input voltage and a plurality of output voltages. Only one energy-saving component is adopted, but two or more output voltages may be obtained. Not only the LED string is supplied with the voltage, but also other loadings of the driving circuit may be supplied with the operational voltage. In this way, it is not needed to adopt large-scale energy-saving component, i.e., inductor, such that the cost of the product is reduced.
It should be noted that the relational terms herein, such as “first” and “second”, are used only for differentiating one entity or operation, from another entity or operation, which, however do not necessarily require or imply that there should be any real relationship or sequence. Moreover, the terms “comprise”, “include” or any other variations thereof are meant to cover non-exclusive including, so that the process, method, article or device comprising a series of elements do not only comprise those elements, but also comprise other elements that are not explicitly listed or also comprise the inherent elements of the process, method, article or device. In the case that there are no more restrictions, an element qualified by the statement “comprises a . . . ” does not exclude the presence of additional identical elements in the process, method, article or device that comprises the said element.
It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.
Number | Date | Country | Kind |
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2014 1 0270602 | Jun 2014 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2014/080817 | 6/26/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2015/192388 | 12/23/2015 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5617015 | Goder | Apr 1997 | A |
6075295 | Li | Jun 2000 | A |
6369551 | Blumenkrantz | Apr 2002 | B1 |
6437545 | Sluijs | Aug 2002 | B2 |
6900620 | Nishimori | May 2005 | B2 |
7176661 | Kranz | Feb 2007 | B2 |
7378823 | Yamanaka | May 2008 | B2 |
20010011885 | Nakagawa | Aug 2001 | A1 |
20030086282 | Zeng | May 2003 | A1 |
20050231177 | Tateno | Oct 2005 | A1 |
20070242487 | Orr | Oct 2007 | A1 |
20080122291 | Uchimoto | May 2008 | A1 |
20100013395 | Archibald | Jan 2010 | A1 |
20100019807 | Zhang | Jan 2010 | A1 |
20100177536 | Liu | Jul 2010 | A1 |
20120200231 | Esaki | Aug 2012 | A1 |
20130002162 | Gao | Jan 2013 | A1 |
20130127348 | Yang | May 2013 | A1 |
Number | Date | Country |
---|---|---|
1578081 | Feb 2005 | CN |
Number | Date | Country | |
---|---|---|---|
20150366031 A1 | Dec 2015 | US |