CN1215639C - Adjustable brightness power conversion circuit suitable for display device backlight module - Google Patents
Adjustable brightness power conversion circuit suitable for display device backlight module Download PDFInfo
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- CN1215639C CN1215639C CN 02101619 CN02101619A CN1215639C CN 1215639 C CN1215639 C CN 1215639C CN 02101619 CN02101619 CN 02101619 CN 02101619 A CN02101619 A CN 02101619A CN 1215639 C CN1215639 C CN 1215639C
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Abstract
A brightness-adjustable power transformation circuit suitable for a backlight module of a display device comprises a transformer, a switching drive device, a modulation control device, a pulse string mode control module and a linear mode control module. The central tap end of the primary side coil of the transformer receives a direct current power supply and generates an alternating current output voltage at the secondary side coil. A first switching device and a second switching device of the switching driving device are respectively connected to two ends of the primary side coil, and the first switching device and the second switching device enable the transformer to convert the direct-current power supply into alternating-current output voltage in a push-pull mode. The modulation control device provides a first modulation signal and a second modulation signal to control the first and second switching devices, respectively. The pulse train mode control module provides a pulse train signal to the modulation control device to output and suppress the first and second modulation signals. In addition, the linear mode control module provides a direct current voltage, so that the modulation control device modulates the first modulation signal and the second modulation signal according to the direct current voltage.
Description
Technical field
The present invention relates to the field of display unit, particularly a kind of adjustable brightness power transformation circuit is applicable to the backlight module of display unit.
Background technology
Liquid crystal display (Liquid Crystal Display, hereinafter to be referred as LCD) panel more and more is used in many electronic installations, the for example display screen of mobile computer, personal digital assistant (Personal Digital Assistant, information products such as PDA), even the aeronautical instrument display system has all adopted the LCD technology.This series products usually can use in the environment of different bright-dark degrees, and in order to allow the image that is presented on the lcd screen have better visibility, the LCD display unit needs one (backlight) backlight source, just a light source that is positioned at the LCD back side of panel.Except providing a backlight, also power backlight must can be adjusted so that the image on the lcd screen is still high-visible in the environment of different bright-dark degrees to the LCD panel.
The fluorescent tube current transformer (lampinverter) 100 of Fig. 1 for being adopted in traditional LCD backlight module.As shown in the figure, current transformer 100 comprises transforming circuit, buck power-switching circuit and pulse width modulation (Pulse Width Modulation is hereinafter to be referred as PWM) device.Wherein, transforming circuit is made of first siding ring, transistor Q2, transistor Q3 and related resistors R3, the R4 of transformer T1, inductance L 1, diode D1 and transistor Q1 and related resistors R1, R2 then form buck power-switching circuit (step-downbuck converter), and DC power supply inputs to the buck power-switching circuit.The two ends of transformer T1 primary side (the 1st, 3 pin) are connected to the collector terminal of transistor Q2, transistor Q3, its central tap terminals then is connected in inductance L 1, the 4th pin of transformer T1 secondary side is connected to the end of fluorescent (fluorescent) fluorescent tube LP, and the 5th pin of secondary side then is connected to the other end of fluorescent lamp LP via a feedback resistance CR.The brightness of fluorescent tube LP can be controlled by adjusting the buck power-switching circuit.
The demand of LCD display unit increases day by day in recent years, and the pressure that reduces manufacturing cost also increases progressively thereupon day by day, though it is not high that the fluorescent tube current transformer that is adopted in the backlight module accounts for whole LCD display unit cost, but traditional current transformer 100 shown in Figure 1 need be used the buck power-switching circuit that inductance L 1, diode D1 and transistor Q1 form, and manufacturing cost is still a burden.And, the employed LCD panel of most electronic products both sides each with a tubes as backlight, thus, the present invention proposes a kind of adjustable brightness power transformation circuit, an available transformer drives two tubes.
Summary of the invention
The purpose of this invention is to provide a kind of adjustable brightness power transformation circuit that is applicable to light module of display device, it is adjustable, and the brightness light reaches (dimming ratio) 100: 1.
Another object of the present invention provides a kind of adjustable brightness power transformation circuit, can drive two fluorescent tubes in the LCD backlight module with economic way.
In order to achieve the above object, the invention provides a kind of adjustable brightness power transformation circuit, be applicable to light module of display device.Adjustable brightness power transformation circuit according to the present invention comprises that a transformer (transformer), switches drive unit, a modulation control device, a pulse string mode (burst mode) control module and a linear model (linear mode) control module.Wherein, transformer has primary side (primary) coil and secondary (secondary) lateral coil, the center tap of first siding ring (center tap) termination is received a direct current power supply, is used for this second siding ring and produces an ac output voltage and offer light module of display device.Switching driving device has first switching device and is connected to an end of first siding ring and the other end that the second switch device is connected to first siding ring, and first switching device and second switch device make transformer that DC power supply is converted to ac output voltage in (push-pull) mode of recommending.Modulation control device provides first modulation signal and second modulation signal in order to control first and second switching devices respectively, and first and second modulation signal has first work period (dutycycle) to take turns opening and closing first and second switching devices.Moreover, the pulse string mode control module provide a burst signal to modulation control device modulating first and second modulation signal, burst signal had for one second work period and can export and suppress first and second modulation signal.The linear model control module provides a dc adjustmenting voltage to modulation control device, make modulation control device according to dc adjustmenting voltage to modulate first work period of first and second modulation signal.In addition, adjustable brightness power transformation circuit comprises that also one starts frequency control module, change the frequency of oscillation of first and second modulation signals that modulation control device provided according to an enabling signal, can be when light module of display device be opened, promote ac output voltage to starting resistor value, after light module of display device is lighted, adjust the frequency of oscillation of first and second modulation signals of modulation control device then, make ac output voltage return back to the normal working voltage value.
Description of drawings
For above-mentioned purpose of the present invention, feature and advantage can more obviously easily be seen, below enumerate a preferred embodiment, and in conjunction with the accompanying drawings, be described in detail below:
Fig. 1 is the circuit diagram of traditional power transformation circuit that fluorescent tube adopted in the backlight module;
Fig. 2 is the rough schematic of the adjustable brightness power transformation circuit of the LCD backlight module according to the present invention;
Fig. 3 is a circuit diagram according to the preferred embodiment of the invention;
Fig. 4 a-4f is the triangular wave of explanation modulation control device internal oscillator generation and the modulation signal waveform schematic diagram of output;
Fig. 5 a-5c is the burst signal waveform schematic diagram that explanation pulse string mode control module comparison one triangular wave and a direct current voltage are exported; And
Fig. 6 a-6d is the explanation modulation control device puts on switching driving device by burst signal output and inhibition a modulation signal waveform schematic diagram.
Embodiment
With reference to figure 2, the adjustable brightness power transformation circuit 200 of LCD backlight module comprises transformer T10, switching driving device 210, modulation control device 220, pulse string mode control module 230, linear model control module 240 and starts frequency control module 250 according to the present invention.DC power supply V
DCPut on the center tap (the 2nd pin) of transformer T10 first siding ring via a bypass capacitor C 10, first switching device S10 of switching driving device 210 and second switch device S20 are connected to the two ends (the 1st, 3 pin) of transformer T10 first siding ring respectively, the first switching device S10 and second switch device S20 with the push pull mode alternately open, close make transformer T10 at second siding ring with DC power supply V
DCBe converted to ac output voltage.The two ends of transformer T10 second siding ring (the 4th, 5 pin) drive fluorescent tube LP1, LP2 and a capacitor C 20 in parallel respectively as filter capacitor.Diode D10, D20 and D30, D40 can not damaged by excessive output voltage with the protection fluorescent tube as the voltage rectifying circuit on LP1, the LP2.270 signal feedback with contact F of feedback circuit are given modulation control device 220.
Pulse string mode control module 230 provide a burst signal 232 to pwm control circuit 220 to modulate first and second modulation signal 222,224, burst signal 232 is the pulse of one-period property, can export and suppress first and second modulation signal 222,224.240 of linear model control modules provide a dc adjustmenting voltage 242 to pwm control circuit 220, and pwm control circuit 220 can be according to dc adjustmenting voltage 242 to modulate the work period of first and second modulation signal 222,224.
In addition, need higher starting resistor owing to light fluorescent tube, adjustable brightness power transformation circuit 200 comprises that also one starts frequency control module 250, and the enabling signal 262 that is provided by light sensing circuit 260 is provided.When light module of display device is opened, because light sensing circuit 260 sensings are less than enough brightness, therefore send enabling signal 262, and start frequency control module 250 according to enabling signal 262, the frequency of first and second modulation signals 222,224 that raising pwm control circuit 220 is provided, the result promotes ac output voltage to starting resistor value to light fluorescent tube LP1, LP2.Then, after light module of display device was lighted, light sensing circuit 260 was received enabling signal 262, and started the frequency that frequency control module 250 is adjusted first and second modulation signals 222,224, made ac output voltage return back to the normal working voltage value.
With reference to figure 3 and in conjunction with Fig. 4 a-4d, Fig. 5 a-5c and Fig. 6 a-6d to further specify adjustable brightness power transformation circuit 200 of the present invention.Pwm control circuit 220 comprises that PWM produces circuit 226 and driving transistors Q10, Q20 and related resistors R10, R20, the base stage of driving transistors Q10, Q20 is received the output 322,324 that PWM produces circuit 226 respectively, and the emitter of driving transistors Q10, Q20 is then exported first and second modulation signal 222,224 to control the first and second switching device S10, S20 respectively.Shown in Fig. 3 preferred embodiment, the feedback signal that the feedback circuit 270 that 226 receptions of PWM generation circuit are made of resistance R 30-R38, capacitor C 30-C34 is provided is adjusted the pulse signal on the output 322,324.Because pwm control circuit 220 is known by those skilled in the art, will repeat no more its detailed principle at this.
The dc adjustmenting voltage 242 that linear model control module 240 is provided can be produced with variable resistor VR dividing potential drop power supply Vcc by resistance R 40 as shown in Figure 3.With reference to 4a figure, PWM produces the result of the position accurate 410 of relatively more inner triangular wave that produces 400 of circuit 226 and dc adjustmenting voltage 242, base stage at driving transistors Q10 produces a pulse 420 (also the base stage at driving transistors Q20 produces another pulse), shown in Fig. 4 b, pulse 420 is pulse width modulating signal (Pulse-Width Modulation, PWM), the work period of pulse 420 changes with the position of dc adjustmenting voltage 242 is accurate.430,440 of pulses among Fig. 4 c, the 4d are created in first and second modulation signal 222,224 that had for 40% work period on driving transistors Q10, the Q20 emitter respectively in order to illustrate, and the pulse 430 ', 440 ' among Fig. 4 e, the 4f then is used for illustrating first and second modulation signal 222,224 with 10% work period.When the user wishes to adjust the LCD brightness of backlight module, can adjust variable resistor VR and just can change dc adjustmenting voltage 242, and then modulate linearly the work period of first and second modulation signal 222,224.In the present embodiment, the frequency range of first and second modulation signal 222,224 is between 40KHz-60KHz.
Among Fig. 4 a, the frequency of the PWM generation circuit 226 inner triangular waves that produce 400 can produce circuit 226 external resistance value, capacitances by PWM and determine.Therefore, shown in Fig. 3 preferred embodiment, starting frequency control module 250 can be made of switching device S50, capacitor C 50 and resistance R 50, R52, owing to need higher starting resistor when fluorescent tube starts, so need to improve the startup frequency of PWM, so when enabling signal 262 is sent, shutting switching device S50 causes resistance R 50 in parallel with resistance R 52, reduce PWM and produced the external resistance value of circuit 226, the result improves the frequency that PWM produces the circuit 226 inner triangular waves that produce 410, has also improved the frequency of first and second modulation signal 222,224 thus.When enabling signal 262 is received, open switching device S50, make PWM produce circuit 226 external resistance value, capacitances and reply normally, adjust first and second modulation signal 222,224 thus and get back to normal frequency.
Pulse string mode control module 230 can comprise a comparator 330, with reference to figure 5a, pulse string mode control module 230 produces burst signal 232 according to triangular wave on two inputs 332,334 of comparator 330 500 and DC input voitage position accurate 510, the waveform 520 of burst signal 232 shown in 5b figure, its work period changes with direct current position accurate 510, and 530 of waveforms among Fig. 5 c are in order to illustrate the burst signal 232 with 50% work period.The user can change triangular wave frequency or the DC input voitage position standard on two inputs 332,334 of comparator 330, to adjust the LCD brightness of backlight module.Fig. 6 a explanation PWM produces circuit 226 puts on switching driving device 210 by burst signal 232 outputs and inhibition modulation signal waveform schematic diagram, Fig. 6 a, waveform 600 is represented burst signal 232 among the 6b, Fig. 6 a, waveform 610 representatives are without first (the second) modulation signal 222 (224) of burst signal 232 modulation among the 6c, Fig. 6 a, 620 of waveforms have been represented the result through 232 modulation of pulse string signal among the 6d, as shown in the figure, when burst signal 232 is high levle, PWM produces circuit 226 can make driving transistors Q10 (Q20) output first (the second) modulation signal 222 (224) to switching driving device 210, and when burst signal 232 was low level, PWM produces 226 in circuit made driving transistors Q10 (Q20) suppress first (the second) modulation signal 222 (224).Thus, according to adjustable brightness power transformation circuit of the present invention, it is adjustable, and the brightness light can reach 100: 1 at least, and for to make the fluorescent tube of lighting not have scintillation, the frequency range of burst signal 232 is between 200Hz-400Hz.
Comprehensively the above the invention discloses a kind of adjustable brightness power transformation circuit that is applicable to light module of display device, can drive two fluorescent tubes in the LCD backlight module with economic way, and have at least 100: 1 adjustable brightness light.
Though the present invention has pressed specific embodiment openly as above; but this technology contents only of the present invention for convenience of explanation; and be not with narrow sense of the present invention be defined in this embodiment; any those skilled in the art; do not breaking away under the spirit and scope of the present invention situation; can make some changes and revise, so protection scope of the present invention is when being as the criterion with defining of appended claim.
Claims (10)
1. adjustable brightness power transformation circuit that is applicable to light module of display device comprises:
One transformer has first siding ring and second siding ring, and the center tap termination of this first siding ring is received a direct current power supply, in order to produce an ac output voltage at this second siding ring and to offer this light module of display device;
One switches drive unit, have first switching device and be connected to an end of this first siding ring and the other end that the second switch device is connected to this first siding ring, this first switching device and this second switch device make this transformer that this DC power supply is converted to this ac output voltage with push pull mode;
One modulation control device, provide first modulation signal and second modulation signal in order to controlling this first switching device and this second switch device respectively, this first and this second modulation signal had for first work period with this first switching device of opening and closing and this second switch device in turn;
One pulse string mode control module, provide a burst signal to this modulation control device modulating this first modulation signal and this second modulation signal, this burst signal had for one second work period with output with suppress this first modulation signal and this second modulation signal;
One linear model control module provides a dc adjustmenting voltage to this modulation control device, make this modulation control device according to this dc adjustmenting voltage with modulate this first and this first work period of this second modulation signal; And
One starts frequency control module, this startup frequency control module changes a frequency of oscillation of above-mentioned first and above-mentioned second modulation signal that above-mentioned modulation control device provides according to an enabling signal, in order to when above-mentioned light module of display device is opened, promote above-mentioned ac output voltage to starting resistor value.
2. adjustable brightness power transformation circuit as claimed in claim 1, wherein above-mentioned startup frequency control module is after above-mentioned light module of display device is lighted, adjust the above-mentioned frequency of oscillation of above-mentioned first and above-mentioned second modulation signal of above-mentioned modulation control device, make above-mentioned ac output voltage return back to the normal working voltage value.
3. adjustable brightness power transformation circuit as claimed in claim 1, wherein above-mentioned modulation control device is a pulse width modulation control circuit.
4. adjustable brightness power transformation circuit as claimed in claim 3, wherein above-mentioned pulse width modulation control circuit is accurate according to the position of the above-mentioned dc adjustmenting voltage that above-mentioned linear model control module provides, change above-mentioned first and above-mentioned first work period of above-mentioned second modulation signal, to modulate above-mentioned first and the pulse duration of above-mentioned second modulation signal.
5. above-mentioned first and above-mentioned second modulation signal that adjustable brightness power transformation circuit as claimed in claim 4, wherein above-mentioned pulse width modulation control circuit provide have a periodic frequency of oscillation.
6. adjustable brightness power transformation circuit as claimed in claim 5, wherein above-mentioned first and the above-mentioned surge frequency range of above-mentioned second modulation signal between 40KHz-60KHz.
7. adjustable brightness power transformation circuit as claimed in claim 1, wherein above-mentioned pulse string mode control module can be adjusted above-mentioned second work period of above-mentioned burst signal, to modulate the pulse duration of above-mentioned burst signal, make that the output of above-mentioned first modulation signal and above-mentioned second modulation signal and the time length of inhibition are controlled.
8. adjustable brightness power transformation circuit as claimed in claim 7, the burst signal that wherein above-mentioned pulse string mode control module provides has a periodic pulse frequency.
9. adjustable brightness power transformation circuit as claimed in claim 8, wherein the above-mentioned pulse frequency scope of above-mentioned burst signal is between 200Hz-400Hz.
10. adjustable brightness power transformation circuit as claimed in claim 1, wherein above-mentioned first of above-mentioned switching driving device and above-mentioned second switch device be transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 02101619 CN1215639C (en) | 2002-01-10 | 2002-01-10 | Adjustable brightness power conversion circuit suitable for display device backlight module |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 02101619 CN1215639C (en) | 2002-01-10 | 2002-01-10 | Adjustable brightness power conversion circuit suitable for display device backlight module |
Publications (2)
| Publication Number | Publication Date |
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| CN1431646A CN1431646A (en) | 2003-07-23 |
| CN1215639C true CN1215639C (en) | 2005-08-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN 02101619 Expired - Fee Related CN1215639C (en) | 2002-01-10 | 2002-01-10 | Adjustable brightness power conversion circuit suitable for display device backlight module |
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Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1826721A (en) | 2004-05-17 | 2006-08-30 | 索尼株式会社 | Power supply apparatus and display apparatus |
| JP2006078974A (en) * | 2004-09-13 | 2006-03-23 | Toshiba Matsushita Display Technology Co Ltd | Light source apparatus |
| CN100416350C (en) * | 2004-11-19 | 2008-09-03 | 索尼株式会社 | Backlight driving device, backlight driving method and liquid crystal display device |
| TWI349917B (en) * | 2005-06-22 | 2011-10-01 | Chunghwa Picture Tubes Ltd | Multi-mode switch for plasma display panel |
| CN101256292B (en) * | 2007-02-28 | 2010-12-29 | 奇美电子股份有限公司 | Backlight module with variable brightness and brightness control method thereof |
| US8471975B2 (en) | 2007-05-23 | 2013-06-25 | Lg Display Co., Ltd. | Display device |
| CN101330792B (en) * | 2007-06-22 | 2012-07-04 | 群康科技(深圳)有限公司 | Circuit and method for regulating light |
| KR101194656B1 (en) * | 2008-02-12 | 2012-10-29 | 엘지디스플레이 주식회사 | Backlight driving system for liquid crystal display device |
| DE102010014941A1 (en) * | 2010-04-14 | 2011-10-20 | Semikron Elektronik Gmbh & Co. Kg | Circuit arrangement and method for isolated power transmission with two output DC voltages |
| CN102376272A (en) * | 2011-09-30 | 2012-03-14 | 青岛海信电器股份有限公司 | Driving circuit of LED (light emitting diode) backlight source, LED backlight source and liquid crystal display device |
| CN103889093B (en) * | 2012-12-20 | 2016-06-08 | 北汽福田汽车股份有限公司 | Backlight regulates device and vehicle |
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2002
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Assignee: Suzhou Darfon Electronic Co., Ltd. Assignor: Dafang Electronics Co., Ltd. Contract fulfillment period: 2004.4.23 to 2017.3.14 contract change Contract record no.: 2009990000827 Denomination of invention: Current changeable circuit of adjustable bright applicable to background light module of display device Granted publication date: 20050817 License type: Exclusive license Record date: 2009.7.31 |
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Free format text: EXCLUSIVE LICENSE; TIME LIMIT OF IMPLEMENTING CONTACT: 2004.4.23 TO 2017.3.14; CHANGE OF CONTRACT Name of requester: SUZHOU DAFANG ELECTRONICS CO., LTD. Effective date: 20090731 |
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Granted publication date: 20050817 Termination date: 20130110 |