CN102184710A - Drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes - Google Patents
Drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes Download PDFInfo
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- CN102184710A CN102184710A CN2011100768008A CN201110076800A CN102184710A CN 102184710 A CN102184710 A CN 102184710A CN 2011100768008 A CN2011100768008 A CN 2011100768008A CN 201110076800 A CN201110076800 A CN 201110076800A CN 102184710 A CN102184710 A CN 102184710A
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Abstract
The invention provides a drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes. The drive circuit comprises a direct current-alternating current conversion circuit, a PWM (Pulse-Width Modulation) drive control circuit, a first high voltage transformer, a second high voltage transformer and a plurality of CCFL tube branches which are connected in parallel, wherein each CCFL tube branch comprises a first triode and a second triode; the emitter of the first triode is mutually connected with the emitter of the second triode, and the base electrode of the first triode and the base electrode of the second triode are connected with a current feedback circuit; the anode of a first diode is connected with the emitter of the first triode, and the cathode of the first diode is connected with the collector of the first triode; the anode of a second diode is connected with the emitter of the second triode, the cathode of the second diode is connected with the collector of the second triode; and the first CCFL tube is connected in series between a first capacitor and the collector of the first triode, and the second CCFL tube is connected in series between a second capacitor and the collector of the second triode. By adopting the drive circuit, currents flowing through the CCFL tubes are equal, and the circuit has a simple structure.
Description
Technical field
The present invention relates to a kind of driving circuit of LCD backlight module, especially relate to the current balance circuit in the driving circuit of a kind of cathode fluorescent tube (CCFL).
Background technology
Cathode fluorescent tube (CCFL, Cold Cathode Fluorescent Lamp) is widely used in the LCD backlight module of backlit display.Usually, the CCFL fluorescent tube light the alternating voltage quite high with need of work, this alternating voltage is provided by driving circuit.
Because LCD module backlight need use a plurality of CCFL fluorescent tubes, and need make the directly luminous brightness of each fluorescent tube identical, just need the CCFL lamp tube current to be consistent.If driving circuit only adds high pressure to CCFL fluorescent tube the two poles of the earth, because each CCFL fluorescent tube characteristic is inconsistent, start or operate as normal no matter be, therefore need to increase extra CCFL lamp tube current balancing circuitry, force each CCFL lamp tube current to keep basically identical, satisfying LCD module backlight provides even and enough brightness.
Figure 1 shows that the synoptic diagram of the driving circuit of existing CCFL fluorescent tube.The driving circuit of CCFL fluorescent tube comprises: the dc-ac conversion circuit that input direct voltage is changed into the alternating voltage that drives a plurality of CCFL lamp works; Two high-tension transformer T1 that primary side is connected with dc-ac conversion circuit and T2, high-tension transformer T1 produces high pressure HV1, high pressure HV1 and capacitor C 1, capacitor C 3, the end of capacitor C n-1 links to each other, capacitor C 1, capacitor C 3, the other end of capacitor C n-1 respectively with CCFL fluorescent tube L1, CCFL fluorescent tube L3, the end of CCFL fluorescent tube Ln-1 links to each other, CCFL fluorescent tube L1, CCFL fluorescent tube L3, the CCFL fluorescent tube Ln-1 other end respectively with CCFL fluorescent tube L2, CCFL fluorescent tube L4, the end of CCFL fluorescent tube Ln links to each other, CCFL fluorescent tube L2, CCFL fluorescent tube L4, the other end of CCFL fluorescent tube Ln respectively with capacitor C 2, capacitor C 4, the end of capacitor C n links to each other, capacitor C 2, capacitor C 4, the other end of capacitor C n produces high pressure HV2 with high-tension transformer T2 respectively and links to each other.The electric current of high pressure HV1 by capacitor C 1, capacitor C 3 ..., capacitor C n-1, CCFL fluorescent tube L1, CCFL fluorescent tube L3 ..., CCFL fluorescent tube Ln-1, CCFL fluorescent tube L2, CCFL fluorescent tube L4 ..., CCFL fluorescent tube Ln, capacitor C 2, capacitor C 4 ..., capacitor C n gets back to other one group of high pressure HV2, or by opposite current direction, with CCFL fluorescent tube L1, CCFL fluorescent tube L2 ..., CCFL lamp tube starting such as CCFL fluorescent tube Ln.
Because capacitor C 1, capacitor C 2 ..., the impedance held of high-tension electricity such as capacitor C n be far longer than a plurality of CCFL fluorescent tube L1, CCFL fluorescent tube L2 ..., CCFL fluorescent tube Ln impedance, so CCFL lamp current Approximate Equivalent in the effective value of sinusoidal high pressure output voltage divided by the high-voltage capacitance impedance.This circuit shortcoming is: the CCFL lamp current depends on the appearance value of high-voltage capacitance substantially, if the deviation of capacitance own is big or after work a period of time variation in capacitance value big, then the CCFL lamp current is will deviation bigger, can not make and flow through each CCFL lamp tube current and equate, can't realize the CCFL lamp tube current balance for a long time, the phenomenon of brightness irregularities may appear in the LCD panel that causes working long hours.
Summary of the invention
The present invention proposes a kind of driving circuit with CCFL fluorescent tube of current balance type, and the driving circuit that has solved present CCFL fluorescent tube can't guarantee the technical matters of each CCFL lamp tube current balance.
The present invention adopts following technical scheme to realize: a kind of driving circuit with CCFL fluorescent tube of current balance type, and this driving circuit comprises: dc-ac conversion circuit; Send pwm signal control dc-ac conversion circuit and finish the PWM Drive and Control Circuit of DC-AC conversion process; Primary side series connection back connects first high-tension transformer and second high-tension transformer of dc-ac conversion circuit, is connected in series some CCFL fluorescent tube branch roads connected with each other between the secondary side of this first high-tension transformer and second high-tension transformer; Wherein, every CCFL fluorescent tube branch road comprises: first triode and second triode, and this first triode and second transistor emitter interconnect, and base stage all connects the PWM Drive and Control Circuit by current feedback circuit; First diode and second diode, wherein, emitter, the negative electrode that the anode of first diode connects first triode connects the collector of first triode, and emitter, the negative electrode that the anode of second diode connects second triode connects the collector of second triode; A wherein end of the one CCFL fluorescent tube is connected in series the secondary side that first electric capacity connects first high-tension transformer, and the other end connects the collector of first triode; A wherein end of the 2nd CCFL fluorescent tube is connected in series the secondary side that second electric capacity connects second high-tension transformer, and the other end connects the collector of second triode.
Therefore, first triode in all CCFL fluorescent tube branch roads, second transistor base all has a points of common connection at current feedback circuit, so first triode in all CCFL fluorescent tube branch roads, the second transistor base electric current is identical, according to the characteristic (collector current is approximately equal to base current and multiply by the triode enlargement factor) of triode as can be known, first triode in all CCFL fluorescent tube branch roads, the collector current of second triode also equates, enlargement factor is identical, so synchronization flows through a CCFL fluorescent tube in each CCFL fluorescent tube branch road, the 2nd CCFL lamp tube current equates, thereby the luminosity that guarantees each CCFL fluorescent tube equates.
In a preferred embodiment, in CCFL fluorescent tube branch road, the base stage of first triode connects collector therein, and the base stage of second triode connects collector.Such as among Fig. 2 in article one CCFL fluorescent tube branch road, triode Q1 is connected collector with the equal base stage of triode Q2, its purpose is set current settings, and the base stage of promptly all triodes is all linked together, and the collector current of its electric current and triode Q1, triode Q2 equates.
Wherein, first triode, second triode are N type triode.
Therefore, the present invention has realized each CCFL lamp tube current, thereby has guaranteed each CCFL lamp luminescence unanimity in the LCD backlight module by current balance circuit simple in structure.
Description of drawings
Fig. 1 is the synoptic diagram of the driving circuit of existing CCFL fluorescent tube.
Fig. 2 is the synoptic diagram of the driving circuit of CCFL fluorescent tube of the present invention.
Embodiment
The invention provides the driving circuit of CCFL fluorescent tube in a kind of LCD module backlight, this driving circuit comprises making and flows through the current balance circuit that each CCFL lamp tube current equates, make the luminosity of each CCFL fluorescent tube equate, thereby guarantee that LCD module backlight has even and enough brightness.
As shown in Figure 2, the driving circuit of CCFL fluorescent tube of the present invention comprises: the dc-ac conversion circuit that input direct voltage is changed into the alternating voltage that drives a plurality of CCFL lamp works; High-tension transformer T1 that primary side is connected with dc-ac conversion circuit and high-tension transformer T2, the secondary side of high-tension transformer T1 produces high pressure HV1, and the secondary side of high-tension transformer T2 produces high pressure HV2; Primary side connects the PWM Drive and Control Circuit, secondary side connects the isolation drive transformer T3 of dc-ac conversion circuit, and wherein the PWM Drive and Control Circuit is sent pwm signal control dc-ac conversion circuit and finished and convert DC voltage to sine-shaped alternating voltage; In addition, the PWM Drive and Control Circuit connects current balance circuit by current feedback circuit; Be serially connected in some CCFL fluorescent tube branch roads between the secondary side of the secondary side of high-tension transformer T1 and high-tension transformer T2, every CCFL fluorescent tube branch road has identical circuit structure and parallel with one another.
Such as, the 1st CCFL fluorescent tube props up route capacitor C 1 and capacitor C 2, triode Q1 and triode Q2, diode D1 and diode D2 composition, CCFL fluorescent tube L1 and CCFL fluorescent tube L2 composition; Wherein, the secondary side serial connection capacitor C 1 of high-tension transformer T1 connects the end of CCFL fluorescent tube L1, and the other end of CCFL fluorescent tube L1 connects the collector of triode Q1, triode Q1 emitter connects the emitter of triode Q2, and the collector of triode Q2 is connected in series the secondary side of CCFL fluorescent tube L2, capacitor C 2 back connection high-tension transformer T2 successively; The base stage of triode Q1 all is connected current feedback circuit with the base stage of triode Q2; The anode of diode D1 connects triode Q1 emitter, and negative electrode connects triode Q1 collector; The anode of diode D2 connects triode Q2 emitter, and negative electrode connects triode Q2 collector.
Has the same structure of forming by capacitor C 3 and capacitor C 4, triode Q3 and triode Q4, diode D3 and diode D4 form, CCFL fluorescent tube L3 and CCFL fluorescent tube L4 form the 2nd CCFL fluorescent tube branch road and the 1st CCFL fluorescent tube branch road.
The rest may be inferred in the circuit structure connection, therefore, the secondary side of high-tension transformer T1 and capacitor C 1, capacitor C 3, the end of capacitor C n-1 links to each other, capacitor C 1, capacitor C 3, the other end of capacitor C n-1 respectively with CCFL fluorescent tube L1, CCFL fluorescent tube L3, the end of CCFL fluorescent tube Ln-1 links to each other, CCFL fluorescent tube L1, CCFL fluorescent tube L3, the CCFL fluorescent tube Ln-1 other end respectively with CCFL fluorescent tube L2, L4, the end of Ln links to each other, CCFL fluorescent tube L2, CCFL fluorescent tube L4, the other end of CCFL fluorescent tube Ln respectively with capacitor C 2, capacitor C 4, the end of capacitor C n links to each other, capacitor C 2, capacitor C 4, the other end of capacitor C n links to each other with the secondary side of high-tension transformer T2 respectively; Triode Qn-1, triode Qn are connected between CCFL fluorescent tube Ln-1, the CCFL fluorescent tube Ln, CCFL fluorescent tube Ln-1 connects the collector of triode Qn-1, the emitter of triode Qn-1 connects the emitter of triode Qn, the collector of triode Qn connects CCFL fluorescent tube Ln, the negative electrode of diode Dn-1 connects the collector of triode Qn-1, the anode utmost point of diode Dn-1 connects the emitter of triode Qn-1, the negative electrode of diode Dn connects the collector of triode Qn, and the anode utmost point of diode Dn connects the emitter of triode Qn.
Therefore, current feedback circuit connect triode Q1, triode Q2 ..., triode Qn base stage.
Dc-ac conversion circuit output High Level AC Voltage is given two high-tension transformer T1 and high-tension transformer T2, and high-tension transformer T1 produces high pressure HV1 and high-tension transformer T2 generation high pressure HV2 alternately is the positive half cycle and the negative half period of sinusoidal voltage respectively.
The 1st the CCFL branch road that constitutes with capacitor C 1, CCFL fluorescent tube L1, triode Q1 and triode Q2, diode D1 and diode D2, CCFL fluorescent tube L2 and capacitor C 2 is that example further specifies driving circuit of the present invention and how to realize each CCFL lamp tube current balance: when high pressure HV1 is the sinusoidal positive half cycle of alternating voltage, high pressure HV2 is in sinusoidal negative half period, electric current is from capacitor C 1 process CCFL fluorescent tube L1, pass through collector, the emitter of triode Q1 again, by diode D2, CCFL fluorescent tube L2, capacitor C 2, flow back to HV2; When HV2 is the sinusoidal positive half cycle of alternating voltage, HV1 is in sinusoidal negative half period, electric current is from capacitor C 2 process CCFL fluorescent tube L2, pass through collector, the emitter of triode Q2 again, by diode D1, CCFL fluorescent tube L1, capacitor C 1, flow back to HV1, the principle of work of other CCFL fluorescent tubes such as CCFL fluorescent tube L1 and CCFL fluorescent tube L2.
Because triode Q1, triode Q2, the base current of triode Qn all is connected with current feedback circuit, so triode Q1, triode Q2, the base current of triode Qn all equates, according to the characteristic (collector current is approximately equal to base current and multiply by the triode enlargement factor) of triode as can be known, triode Q1, triode Q2, the collector current of triode Qn also equates, the enlargement factor of triode is identical, so synchronization flows through CCFL fluorescent tube L1, CCFL fluorescent tube L2, the electric current of CCFL fluorescent tube L n equates, thereby the luminosity that guarantees each CCFL fluorescent tube equates.
The above only is preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of being done within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (3)
1. driving circuit with CCFL fluorescent tube of current balance type, this driving circuit comprises: dc-ac conversion circuit; Send pwm signal control dc-ac conversion circuit and finish the PWM Drive and Control Circuit of DC-AC conversion process; Primary side series connection back connects first high-tension transformer and second high-tension transformer of dc-ac conversion circuit, is connected in series some CCFL fluorescent tube branch roads connected with each other between the secondary side of this first high-tension transformer and second high-tension transformer; It is characterized in that every CCFL fluorescent tube branch road comprises:
First triode and second triode, this first triode and second transistor emitter interconnect, and base stage all connects the PWM Drive and Control Circuit by current feedback circuit;
First diode and second diode, wherein, emitter, the negative electrode that the anode of first diode connects first triode connects the collector of first triode, and emitter, the negative electrode that the anode of second diode connects second triode connects the collector of second triode;
A wherein end of the one CCFL fluorescent tube is connected in series the secondary side that first electric capacity connects first high-tension transformer, and the other end connects the collector of first triode;
A wherein end of the 2nd CCFL fluorescent tube is connected in series the secondary side that second electric capacity connects second high-tension transformer, and the other end connects the collector of second triode.
2. according to the described driving circuit with CCFL fluorescent tube of current balance type of claim 1, it is characterized in that in CCFL fluorescent tube branch road, the base stage of first triode connects collector therein, the base stage of second triode connects collector.
3. according to the described driving circuit of claim 1, it is characterized in that first triode and second triode are N type triode with CCFL fluorescent tube of current balance type.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100768008A CN102184710A (en) | 2011-03-29 | 2011-03-29 | Drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011100768008A CN102184710A (en) | 2011-03-29 | 2011-03-29 | Drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes |
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| CN102184710A true CN102184710A (en) | 2011-09-14 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN2011100768008A Pending CN102184710A (en) | 2011-03-29 | 2011-03-29 | Drive circuit with current balance for CCFL (Cold Cathode Fluorescent Lamp) tubes |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114246961A (en) * | 2020-09-21 | 2022-03-29 | 尚闳科技股份有限公司 | Cold cathode tube ozone lamp |
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| US7042171B1 (en) * | 2004-11-26 | 2006-05-09 | Hsiu-Ying Li | Multiple-CCFL parallel driving circuit and the associated current balancing control method for liquid crystal display |
| CN2847625Y (en) * | 2005-11-25 | 2006-12-13 | 陈强 | Motor vehicle main cable protector |
| CN101144936A (en) * | 2006-09-12 | 2008-03-19 | Lg.菲利浦Lcd株式会社 | Backlight drive device |
| CN201248186Y (en) * | 2008-07-02 | 2009-05-27 | 冠捷投资有限公司 | Multi-lamp-tube current-equalizing circuit for display |
| US20090184656A1 (en) * | 2008-01-21 | 2009-07-23 | Yen-Chen Huang | Backlight system having a lamp current balance and feedback mechanism and related method thereof |
| CN101662871A (en) * | 2009-09-11 | 2010-03-03 | 深圳创维－Rgb电子有限公司 | Current balance circuit for fluorescent lamp, backlight module and liquid crystal display TV |
| TW201029518A (en) * | 2009-01-20 | 2010-08-01 | Univ Ishou | Single-stage driving circuit for fluorescent lamp tube with high power factor and high performance |
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2011
- 2011-03-29 CN CN2011100768008A patent/CN102184710A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7042171B1 (en) * | 2004-11-26 | 2006-05-09 | Hsiu-Ying Li | Multiple-CCFL parallel driving circuit and the associated current balancing control method for liquid crystal display |
| CN2847625Y (en) * | 2005-11-25 | 2006-12-13 | 陈强 | Motor vehicle main cable protector |
| CN101144936A (en) * | 2006-09-12 | 2008-03-19 | Lg.菲利浦Lcd株式会社 | Backlight drive device |
| US20090184656A1 (en) * | 2008-01-21 | 2009-07-23 | Yen-Chen Huang | Backlight system having a lamp current balance and feedback mechanism and related method thereof |
| CN201248186Y (en) * | 2008-07-02 | 2009-05-27 | 冠捷投资有限公司 | Multi-lamp-tube current-equalizing circuit for display |
| TW201029518A (en) * | 2009-01-20 | 2010-08-01 | Univ Ishou | Single-stage driving circuit for fluorescent lamp tube with high power factor and high performance |
| CN101662871A (en) * | 2009-09-11 | 2010-03-03 | 深圳创维－Rgb电子有限公司 | Current balance circuit for fluorescent lamp, backlight module and liquid crystal display TV |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114246961A (en) * | 2020-09-21 | 2022-03-29 | 尚闳科技股份有限公司 | Cold cathode tube ozone lamp |
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Application publication date: 20110914 |