CN101727831B - Drive circuit of back light module and method thereof - Google Patents
Drive circuit of back light module and method thereof Download PDFInfo
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- CN101727831B CN101727831B CN2008101675329A CN200810167532A CN101727831B CN 101727831 B CN101727831 B CN 101727831B CN 2008101675329 A CN2008101675329 A CN 2008101675329A CN 200810167532 A CN200810167532 A CN 200810167532A CN 101727831 B CN101727831 B CN 101727831B
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Abstract
The invention discloses a drive circuit of a back light module, which comprises a signal producing circuit, a resonance circuit, a control circuit and a regulator circuit, wherein the signal producing circuit is used for producing an alternate current signal of a fixed frequency; the resonance circuit is coupled to the signal producing circuit and is used for producing an oscillator signal based on the alternate current signal of the fixed frequency to drive a back light source; the control circuit is used for providing a control signal; and the regulator circuit is coupled to the control circuit, and the resonance circuit and the back light source for providing an impedance based on the control signal so as to regulate a current value of the back light source.
Description
Technical field
The present invention refers to the light modulation driving circuit and the method for a kind of thermionic-cathode tube module backlight especially relevant for a kind of driving mechanism of module backlight.
Background technology
The display device that generally needs backlight, for example LCD etc. can need suitable light modulation mechanism because of user's hobby and background luminance, reaches required brightness so that can adjust the backlight power.
With thermal cathode fluorescent tube (Hot Cathode Fluorescent Lamp; During HCFL) as backlight; The brightness adjustment control mode of its driving circuit has a variety of; Wherein commonly used is frequency modulation (frequencymodulation) control, amplitude modulation (amplitude modulation) control and pulse wave width modulation (pulse width modulation) control, and wherein frequency modulation control can effectively reach the light modulation purpose, and its control circuit is also quite simple; Yet, because the change of frequency, make that the design of filtering circuit of prime also can be because of electromagnetic interference (EMI) (Electro-Magnetic Interference, the EMI) difficulty that becomes, and also can't magnet assembly be done best application; Amplitude adjustment control then is the purpose of borrowing the direct supply that changes resonant circuit to reach light modulation, and its circuit framework design is difficulty comparatively; Pulse wave width modulation control then is to change the purpose that the ON time of switch module reaches light modulation; Generally speaking; Pulse wave width modulation control can be used the mode of symmetrical pulse wave width modulation control; But can cause switch cost high on the switch module and can't reach purpose of power saving, and this circuit framework is also than the frequency modulation control complicated circuit.
Please refer to Fig. 1, shown in Figure 1 is the synoptic diagram of known quasi-semibridge frequency conversion type driving circuit 100.Driving circuit 100 includes a direct current voltage source V dc; One signal generating circuit 110 is used for producing an AC signal of a variable frequency; One resonant circuit 120 is coupled to signal generating circuit 110, is used for this AC signal according to this variable frequency to produce an oscillator signal and drive a backlight 130; One electric capacity 140 is coupled to resonant circuit 120 and backlight 130, is used to provide an impedance, with a current value of adjustment backlight 130; And two electric capacity 160 and 170, be coupled to signal generating circuit 110 and backlight 130, be used for producing a direct current voltage quasi position.In addition, signal generating circuit 110 comprises two transistor 112,114 in addition, and via the frequency of adjusting switching transistor 112,114, can determine the frequency of output AC signal; Resonant circuit 120 includes an inductance 122 and an electric capacity 124 in addition, is used for the AC signal that signal generating circuit 110 is exported is changed into a string ripple signal to drive backlight 130.
As shown in Figure 1, electric capacity 140 is parallel to backlight 130.The frequency that produces the AC signal of circuit 110 generations when basis signal is ω, and then the impedance of electric capacity 140 is 1/ ω C
f, C wherein
fCapacitance for electric capacity 140.According to electric capacity 140 ratio with backlight 130 impedances, can determine the size of current of the backlight 130 of flowing through again, therefore, when the impedance of electric capacity 140 during greater than the impedance of backlight 130, main current path is a backlight 130, that is lights fluorescent tube; And when the impedance of electric capacity 140 during less than the impedance of backlight 130, main current path is an electric capacity 140, that is lighting tube brightness reduces even extinguishes.
The above-mentioned mode that reaches light modulation according to frequency variation has simple circuit framework, yet because the change of frequency can make the filtering circuit of prime receive electromagnetic interference (EMI) and can't magnet assembly be done best application.
Summary of the invention
The object of the present invention is to provide a kind of fixed light modulation driving circuit and method frequently, to solve the above problems.
The embodiment of the invention discloses a kind of driving circuit of module backlight, and it includes: a signal generating circuit is used for producing an AC signal of a fixed frequency; One resonant circuit is coupled to this signal generating circuit, is used for this AC signal according to this fixed frequency to produce an oscillator signal and drive a backlight; One control circuit is used to provide a control signal; And one the adjustment circuit, be coupled to this control circuit, this resonant circuit and this backlight, be used for one impedance being provided, to adjust a current value of this backlight according to this control signal.
The embodiment of the invention discloses a kind of driving method of module backlight, and it includes: an AC signal that produces a fixed frequency; Produce an oscillator signal according to this AC signal of this fixed frequency and drive a backlight; One control signal is provided; And an adjustment circuit was provided, and should adjusts circuit and be coupled to this backlight; And control this adjustment circuit according to this control signal one impedance is provided, to adjust a current value of this backlight.
Description of drawings
Fig. 1 is the synoptic diagram of known quasi-semibridge frequency conversion type driving circuit;
Fig. 2 is the quasi-semibridge synoptic diagram of formula driving circuit frequently surely of first embodiment of the invention;
Fig. 3 is the quasi-semibridge synoptic diagram of formula driving circuit frequently surely of second embodiment of the invention;
Fig. 4 can be used as the transistorized equivalent circuit diagram that variable resistor uses;
Fig. 5 is a transistorized PCD process characterization diagram shown in Figure 4.
[primary clustering symbol description]
100: quasi-semibridge frequency conversion type driving circuit
200,300: quasi-semibridge is frequency formula driving circuit surely
110,210,310: signal generating circuit
112,114,212,214,252,254, transistor
312、314、352、354：
120,220,320: resonant circuit
122,222,322: inductance
124,140,160,170,224,258, electric capacity
260、270、324、360、370：
130,230,330: backlight
240,340: control circuit
250,350: the adjustment circuit
256: two-way switch
Vdc: direct voltage source
G: grid
D: drain electrode
S: source electrode
Dg: diode
Rg: resistance
Rgd: resistance between grid drain electrode
Cgd: electric capacity between grid drain electrode
Cgs: gate source interelectrode capacity
Rs: resistance
Vgs: gate source voltage across poles
Vds: drain source voltage across poles
In: drain source electrode current
Vth: critical voltage
Embodiment
Please refer to Fig. 2, shown in Figure 2 is the quasi-semibridge synoptic diagram of formula driving circuit 200 frequently surely of first embodiment of the invention.In the present embodiment, driving circuit 200 includes a direct current voltage source V dc; One signal generating circuit 210 is used for producing an AC signal of a fixed frequency; One resonant circuit 220 is coupled to signal generating circuit 210, is used for this AC signal according to this fixed frequency to produce an oscillator signal and drive a backlight 230; One control circuit 240 is used to provide a control signal; One adjustment circuit 250 is coupled to control circuit 240, resonant circuit 220 and backlight 230, is used for according to this control signal one impedance being provided, with a current value of adjustment backlight 230; And two electric capacity 260 and 270, be coupled to signal generating circuit 210 and backlight 230, be used for producing a direct current voltage quasi position.In addition, signal generating circuit 210 comprises two transistor 212 and 214 in addition, and wherein switching transistor 212 and 214 can produce the AC signal of above-mentioned fixed frequency; Resonant circuit 220 includes an inductance 222 and an electric capacity 224 in addition, is used for the AC signal that signal generating circuit 210 is exported is changed into a string ripple signal to drive backlight 230; Adjustment circuit 250 includes as a two-way switch 256 and an electric capacity 258 in addition, and wherein two-way switch 256 is made up of 252,254 of two transistors.
As shown in Figure 2, electric capacity 258 is series at two-way switch 256, and electric capacity 258 then is parallel to backlight 230 with two-way switch 256.The frequency of the AC signal that produces when signal generating circuit 210 is ω
1, be to open under the situation of (switched on) at two-way switch 256, the impedance of electric capacity 258 is 1/ ω
1C
f, C wherein
fCapacitance for electric capacity 258.In the present embodiment, impedance 1/ ω of electric capacity 258
1C
fVia well-designed and can be much smaller than the impedance of backlight 230, be under the situation of opening therefore at two-way switch 256, main current path is adjustment circuit 250, that is the brightness of backlight 230 minimum brightness under the driving circuit for this reason; When two-way switch 256 is when closing (switched off), main current path then is a backlight 230, this moment backlight 230 the brightness high-high brightness under the driving circuit for this reason.
In known frequency conversion type driving circuit shown in Figure 1; Be the purpose that the direct electric current of adjusting the backlight of flowing through reaches light modulation, and compared to known technology, in the present embodiment; The size of current of backlight 230 has only two fixing current values because flow through; High-high brightness and the minimum brightness of representing backlight 230 respectively, therefore, the disclosed dimming mode of this case is to utilize control circuit 240 to control the time scale that two-way switch 256 is closed and opened; This ratio also is the time scale of backlight 230 high-high brightness and minimum brightness, just can reach the purpose of adjustment backlight 230 brightness thus.For instance; Suppose that required back light source brightness is the half the of high-high brightness; Then control circuit 240 control two-way switchs 256 time scale of closing and opening is 1:1; That is the time scale of backlight 230 high-high brightness and minimum brightness is 1:1 also, and under the influence of visual fatigue, human eye just can be experienced this required brightness.
The circuit framework of the drive circuit structure of present embodiment and frequency conversion type driving circuit shown in Figure 1 is similar, is under the jurisdiction of the driving circuit with ball bearing made using framework.In addition, because therefore the AC signal frequency of signal generating circuit 200 generations does not have the influence of electromagnetic interference (EMI) for what fix, make that the design of magnet assembly and application can be more efficient.And aspect dimming scope, because the frequency range that signal generating circuit produced has restriction, so the impedance of electric capacity 140 also can be limited in the scope in the frequency conversion type driving circuit 100, causes only providing a limited dimming scope; Yet,, therefore can have bigger dimming scope because utilize control circuit 240 to control the time scale that two-way switch 256 is closed and opened at deciding in the frequency formula driving circuit 200 of present embodiment.
Please refer to Fig. 3, shown in Figure 3 is the quasi-semibridge synoptic diagram of formula driving circuit 300 frequently surely of second embodiment of the invention.In present embodiment, driving circuit 300 includes a direct current voltage source V dc; One signal generating circuit 310 is used for producing an AC signal of a fixed frequency; One resonant circuit 320 is coupled to signal generating circuit 310, is used for this AC signal according to this fixed frequency to produce an oscillator signal and drive a backlight 330; One control circuit 340 is used to provide a control signal; One adjustment circuit 350 is coupled to control circuit 340, resonant circuit 320 and backlight 330, is used for according to this control signal one impedance being provided, with a current value of adjustment backlight 330; And two electric capacity 360 and 370, be coupled to signal generating circuit 310 and backlight 330, be used for producing a direct current voltage quasi position.In addition, signal generating circuit 310 comprises two transistor 312 and 314 in addition, and wherein switching transistor 312 and 314 can produce the AC signal of above-mentioned fixed frequency; Resonant circuit 320 includes an inductance 322 and an electric capacity 324 in addition, is used for the AC signal that signal generating circuit 310 is exported is changed into a string ripple signal to drive backlight 330; Adjustment circuit 350 includes two transistor 352 and 354 in addition with as a two-way switch.
As shown in Figure 3, adjustment circuit 350 is a two-way switch, wherein has a transistor design to become variable-resistance kenel in this two-way switch.Please refer to Fig. 4, Fig. 4 is the equivalent circuit diagram of transistor 352 shown in Figure 3.Do not influence technology of the present invention open under, be that example is explained only at this, yet the present invention is not as limit with transistor 352.As shown in Figure 4, the equivalent electrical circuit of transistor 352 includes three node grid (Gate) G, drain electrode (Drain) D and source electrode (Source) S; A capacitor C gs and a resistance R s between capacitor C gd, a gate-source between resistance R gd, a grid drain electrode between one resistance Rg, a diode Dg, a grid drain electrode; Wherein the operating characteristic of transistor 352 is as shown in Figure 5; In Fig. 5, from top to bottom be respectively between gate source voltage across poles Vgs, drain source voltage across poles Vds and drain-source electric current I n to time relation.At first working as transistorized grid voltage begins to start from being closed to; That is operate in zone (a); This moment, gate source voltage across poles Vgs did not surpass its critical voltage (Thresholdvoltage) Vth as yet, did not therefore have electric current to produce, and the drain source voltage across poles also remains unchanged.Along with gate source voltage across poles Vgs continues to be increased to above critical value, shown in zone (b) among Fig. 5, electric current I n begins to produce between drain-source.Afterwards; Along with the increase of time, electric current I n continues by drain D source S to be charged between drain-source, so drain source voltage across poles Vds can continue to reduce up to drain electrode with till source electrode reaches identical voltage quasi position; Shown in zone (c); Because the drain source electrode resistance is the ratio of electric current I n between drain source voltage across poles Vds and drain-source, therefore in zone (c), the drain source electrode resistance is a variable resistor.If get into zone (d), then all no longer changes of electric current I n between drain source voltage across poles Vds and drain-source.
Therefore; In shown in Figure 3 deciding in the frequency formula driving circuit 300, when control circuit 340 cuts out transistor 352 and 354, that is adjustment circuit 350 has great resistance; Therefore main current path is a backlight 330, and this moment, backlight 330 can reach the high-high brightness under this driving circuit; Otherwise when control circuit 340 turn-on transistor 352 and 354, that is adjustment circuit 350 has very little resistance, and this moment, main current path was adjustment circuit 350, and backlight 330 can reach the minimum brightness under this driving circuit.In the present embodiment; When control circuit 340 operates in variable resistor with transistor 352 or 354; Current path just can be decided by the variable resistor resistance of adjustment circuit 350 and the ratio of backlight resistance, just can reach the purpose of control back light source brightness thus.
The drive circuit structure of present embodiment (that is driving circuit 300) and frequency conversion type driving circuit 100 shown in Figure 1 and the circuit framework of deciding frequency formula driving circuit 200 shown in Figure 2 are similar, all are under the jurisdiction of the driving circuit with ball bearing made using framework.In addition, as before embodiment shown in Figure 2 said, present embodiment decide frequency formula driving circuit 300 owing to there is not the influence of electromagnetic interference (EMI), thereby can make the design of magnet assembly with use can be more efficient.Likewise; Aspect dimming scope; The frequency formula driving circuit 300 of deciding of present embodiment utilizes control circuit 340 to control the resistance value of two-way switch, and the scope of this two-way switch resistance value can be the infinity of certain value (for example 10 millioersted nurses) to convergence, therefore just can have bigger dimming scope.
The above is merely preferred embodiment of the present invention, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (13)
1. the driving circuit of a module backlight is characterized in that, includes:
One signal generating circuit is to produce an AC signal of a fixed frequency;
One resonant circuit is coupled to this signal generating circuit, produces an oscillator signal with this AC signal according to this fixed frequency and drives a backlight;
One control circuit is to provide a control signal; And
One adjustment circuit is coupled to this control circuit, this resonant circuit and this backlight, according to this control signal one impedance to be provided, to adjust a current value of this backlight.
This adjustment circuit comprises a two-way switch, and the impedance when adjusting this two-way switch conducting and the time scale of closing or adjusting this two-way switch conducting to export this control signal according to this control circuit realizes the control to backlight current.
2. driving circuit as claimed in claim 1 is characterized in that, this adjustment circuit is parallel to this backlight.
3. driving circuit as claimed in claim 1 is characterized in that, this adjustment circuit also comprises:
One electric capacity is series at this two-way switch.
4. driving circuit as claimed in claim 3 is characterized in that, the impedance during this two-way switch conducting is a certain value.
5. driving circuit as claimed in claim 3 is characterized in that the impedance of this electric capacity is less than the impedance of this backlight.
6. driving circuit as claimed in claim 1 is characterized in that, this backlight is a thermal cathode fluorescent tube.
7. the driving method of a module backlight is characterized in that, includes:
Produce an AC signal of a fixed frequency;
Produce an oscillator signal according to this AC signal of this fixed frequency and drive a backlight;
One control signal is provided;
One adjustment circuit is provided, and should adjusts circuit and be coupled to this backlight; And
Control this adjustment circuit according to this control signal one impedance is provided, to adjust a current value of this backlight.
Provide the step of this adjustment circuit to include and a two-way switch is set in this adjustment circuit.
8. driving method as claimed in claim 7 is characterized in that, the step that this adjustment circuit is coupled to this backlight includes: should adjust circuit and be parallel to this backlight.
9. driving method as claimed in claim 7 is characterized in that,
Provide the step of this control signal also to include: to set this control signal and adjust this two-way switch conducting and the time of closing.
10. driving method as claimed in claim 7 is characterized in that, provides the step of this control signal also to include: the impedance when setting this control signal and adjusting this two-way switch conducting.
11. driving method as claimed in claim 9 is characterized in that, provides the step of this adjustment circuit to include: with a capacitances in series in this two-way switch.
12. driving method as claimed in claim 11 is characterized in that, provides the step of this control signal to include: set this control signal so that the impedance during this two-way switch conducting is a certain value.
13. driving method as claimed in claim 11 is characterized in that, provides the step of this adjustment circuit to include: set the impedance of the impedance of this electric capacity less than this backlight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008101675329A CN101727831B (en) | 2008-10-10 | 2008-10-10 | Drive circuit of back light module and method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008101675329A CN101727831B (en) | 2008-10-10 | 2008-10-10 | Drive circuit of back light module and method thereof |
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| Publication Number | Publication Date |
|---|---|
| CN101727831A CN101727831A (en) | 2010-06-09 |
| CN101727831B true CN101727831B (en) | 2012-01-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2008101675329A Active CN101727831B (en) | 2008-10-10 | 2008-10-10 | Drive circuit of back light module and method thereof |
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Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102034438B (en) * | 2010-10-15 | 2013-04-24 | 深圳市华星光电技术有限公司 | Driving circuit and driving method for backlight module of display device |
| CN102654990A (en) * | 2012-05-09 | 2012-09-05 | 深圳市华星光电技术有限公司 | Backlight module for changing oscillation frequency in stereo mode and liquid crystal display with backlight module |
| US9058781B2 (en) | 2012-05-09 | 2015-06-16 | Shenzhen China Star Optoelectronics Technology Co., Ltd. | Backlight unit with changing oscillation frequency in stereoscopic mode and liquid crystal display using the same |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0572207B1 (en) * | 1992-05-26 | 1998-08-26 | Compaq Computer Corporation | Constant brightness liquid crystal display backlight control system |
| JP3145625B2 (en) * | 1995-11-20 | 2001-03-12 | 三菱重工業株式会社 | Piping system fatigue evaluation device |
| KR20010112807A (en) * | 2000-06-15 | 2001-12-22 | 윤종용 | Liquid crystal display device using an alternative common voltage |
| CN2805298Y (en) * | 2005-07-04 | 2006-08-09 | 葛世潮 | Dimmer and ager of cold cathode fluorescent lamp |
-
2008
- 2008-10-10 CN CN2008101675329A patent/CN101727831B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0572207B1 (en) * | 1992-05-26 | 1998-08-26 | Compaq Computer Corporation | Constant brightness liquid crystal display backlight control system |
| JP3145625B2 (en) * | 1995-11-20 | 2001-03-12 | 三菱重工業株式会社 | Piping system fatigue evaluation device |
| KR20010112807A (en) * | 2000-06-15 | 2001-12-22 | 윤종용 | Liquid crystal display device using an alternative common voltage |
| CN2805298Y (en) * | 2005-07-04 | 2006-08-09 | 葛世潮 | Dimmer and ager of cold cathode fluorescent lamp |
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|---|---|
| CN101727831A (en) | 2010-06-09 |
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Effective date of registration: 20230515 Address after: No. two, No. 1188 West Ring Road, Shengze Town, Wujiang District, Jiangsu, Suzhou Patentee after: Suzhou Shengze science and Technology Pioneer Park Development Co.,Ltd. Address before: 215217, No. 88, Tung Hing Road, Tongli District, Wujiang Economic Development Zone, Suzhou, Jiangsu Patentee before: CPTW (WUJIANG) Co.,Ltd. Patentee before: Chunghwa Picture Tubes, Ltd. |