CN100397955C - Discharging fluorescent tube circuit capable of controlling starating time and possessing overvoltage protection - Google Patents
Discharging fluorescent tube circuit capable of controlling starating time and possessing overvoltage protection Download PDFInfo
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- CN100397955C CN100397955C CNB021418659A CN02141865A CN100397955C CN 100397955 C CN100397955 C CN 100397955C CN B021418659 A CNB021418659 A CN B021418659A CN 02141865 A CN02141865 A CN 02141865A CN 100397955 C CN100397955 C CN 100397955C
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- discharge lamp
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- drive circuit
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Abstract
The present invention relates to a discharge lamp tube circuit capable of controlling starting time and carrying out over-voltage protection, which comprises a drive circuit, a detection circuit, a timing circuit and a starting circuit, wherein the drive circuit is used for generating the starting voltage of a discharge lamp tube and providing lamp tube current flowing through the discharge lamp tube. The detection circuit can detect whether the lamp tube current exists or not. The timing circuit is controlled by the detection circuit and is capable of forming a reference voltage in the starting stage when a setting period ends so as to control the starting time of the discharge lamp tube. In addition, the starting circuit makes the drive circuit continuously apply the starting voltage to the discharge lamp tube for starting before the reference voltage is formed. The starting circuit turns off the drive circuit to avoid generating oversize voltage when the detection circuit does not detect the lamp tube current.
Description
Technical field
The present invention is relevant for the drive circuit field of discharge lamp, refers in particular to be applicable to liquid crystal display (LiquidCrystal Display LCD) installs the circuit of its (backlight) backlight module.
Background technology
More and more many in recent years information, communication and consumption electronic products adopt lcd screen to come display message, generally speaking, the LCD panel utilizes a backlight module that comprises discharge lamp (discharge lamp) to provide light source to the image that shows on the panel, in the at present all types of discharge lamps with cathode fluorescent tube (Cold-Cathode Fluorescent Lamp, CCFL) can satisfy the demand of LCD backlight module, backlight module then must have high efficiency AC makes its normal running to supply high alternating voltage to CCFL.
The required starting resistor (kick-off or strike voltage) of ignition CCFL is 2-3 a times of the required alternating voltage of its operate as normal, can reach kilovolt, and after applying this high starting resistor, CCFL can postpone a period of time and just understand Discharge illuminating, so characteristic according to different CCFL, generally can apply starting resistor and continue the several seconds and discharge, and be called the light-off time of CCFL during this period of time up to fluorescent tube.Can export high alternating voltage owing to drive the AC of CCFL; if CCFL does not install as yet when starting backlight module; or the CCFL loose contact takes place when operation; CCFL fault even; these situations all can cause does not have the traditional C CFL of over-voltage protection function drive circuit to export excessive voltage constantly, and damages backlight module even hurt the user or the maintenance personal.
Summary of the invention
In view of this, the purpose of this invention is to provide a kind of circuit, can control and apply the light-off time of starting resistor, to be suitable for different discharge lamps in discharge lamp.
Another object of the present invention provides a kind of circuit, can be when the damage of discharge lamp or fluorescent tube be installed, and the drive circuit that turn-offs discharge lamp is to avoid producing excessive voltage.
For reaching described purpose, the invention provides a kind of discharge lamp circuit, may command light-off time and have over-voltage protection function, discharge lamp circuit of the present invention comprise one drive circuit, a testing circuit, regularly a circuit and a start-up circuit.Drive circuit is in order to starting resistor that produces discharge lamp and the lamp current that the discharge lamp of flowing through is provided, and whether testing circuit then can detect lamp current.Timing circuit is controlled by testing circuit, can form a reference voltage during one section setting when the ignition stage finishes, and controls the light-off time of discharge lamp by this.Moreover before forming reference voltage, start-up circuit makes the drive circuit can be in the light-off time of discharge lamp, be continuously applied starting resistor in discharge lamp with ignition; And when start-up circuit detects less than lamp current at testing circuit, turn-off drive circuit to avoid producing excessive voltage.
According to a preferred embodiment of the invention, timing circuit comprises that a resistance and one is connected to the electric capacity of testing circuit, and this electric capacity connects resistance in a node, by during adjusting resistance value and capacitance and can determining described setting.Start-up circuit then comprises a first transistor, and it is connected to the node of timing circuit, and testing circuit comprises a transistor seconds, and it is connected to the electric capacity of timing circuit.Start-up circuit receives an input signal to provide an enabling signal to drive circuit, if the difference between the voltage of the voltage of input signal and node is enough to make the first transistor conducting, then the enabling signal of Chan Shenging is that first signal value is to start drive circuit, when if fluorescent tube so ignition and testing circuit detect lamp current, make the transistor seconds conducting, make the capacitor discharge of timing circuit.If when the damage of discharge lamp or fluorescent tube is not installed, testing circuit detects less than lamp current, transistor seconds shutoff formation is opened circuit cause the electric capacity charging, when therefore during setting, finishing, timing circuit forms reference voltage at node, cause the first transistor that the voltage of input signal and the difference between reference voltage can't the conducting start-up circuit and form and open circuit, make start-up circuit become the secondary signal value to enabling signal to turn-off drive circuit, so avoid producing excessive voltage.In addition, start-up circuit also comprises one the 3rd transistor, and it is connected to the electric capacity of timing circuit, when under normal circumstances turn-offing drive circuit, makes the electric capacity can repid discharge.
Description of drawings
For described purpose of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and conjunction with figs. are described in detail as follows:
Fig. 1 is the block schematic diagram of discharge lamp circuit of the present invention; And
Fig. 2 is the circuit diagram of the preferred embodiment of the present invention.
Label declaration
100-discharge lamp circuit
The 110-drive circuit
The 120-testing circuit
The 130-timing circuit
The 140-start-up circuit
The D1-diode
The LP1-discharge lamp
Q1-Q3-transistor switch device
C1, C2-electric capacity
R1-R9-resistance
V
CC-system direct voltage
Embodiment
According to the present invention, may command light-off time and discharge lamp circuit 100 with overvoltage protection comprise drive circuit 110, testing circuit 120, timing circuit 130 and start-up circuit 140 as shown in Figure 1.Drive circuit 110 can produce the starting resistor of cathode fluorescent tube (CCFL) LP1 and the lamp current I of the fluorescent tube LP1 that flows through is provided
LP, resistance R 1 and diode D1 are series at fluorescent tube LP1, with lamp current I
LPFeed back to drive circuit 110, by this brightness of drive circuit 110 scalable fluorescent tube LP1.Whether 120 of testing circuits are connected to fluorescent tube LP1 via diode D1, have electric current to pass through fluorescent tube LP1 to detect.Timing circuit 130 connects also and is controlled by testing circuit 120, can adjust, determine one to set during T
ON, so at the ignition stage of fluorescent tube LP1 T during this sets
ONWill form reference voltage V during end
REF, can control the light-off time of fluorescent tube LP1 by this.Start-up circuit 140 is connected respectively to drive circuit 110 and timing circuit 130, before timing circuit 130 forms reference voltage, start-up circuit 140 makes the drive circuit 110 can be in the required light-off time of fluorescent tube LP1, be continuously applied starting resistor in fluorescent tube LP1 with ignition; And detect less than lamp current I at testing circuit 120
LPThe time, timing circuit 130 is through T during setting
ONThe back forms reference voltage V
REF, make start-up circuit 140 turn-off drive circuit 110 to avoid producing excessive voltage.
Fig. 2 has illustrated the circuit diagram of preferred embodiment, wherein V
CCRepresent the employed system of backlight module direct voltage, Q1-Q3 then is a switching device, can be ambipolar (Bipolar JunctionTransistor, BJT) or metal-oxide semiconductor (MOS) (Metal-Oxide-Semiconductor, MOS) transistor, for convenience of explanation, this sentences the BJT transistor is representative.Testing circuit 120 is made of capacitor C 2, resistance R 8-R9 and NPN transistor Q2, when testing circuit 120 detects electric current by fluorescent tube LP1, then can produce enough base voltages on resistance R 8 and make transistor Q2
(that is: first switching state), otherwise, when testing circuit 120 detects less than electric current, then can't on resistance R 8, produce voltage, so transistor Q2 turn-off and form and open circuit (that is: second switching state).Capacitor C 1 and resistance R 7 form timing circuit 130, and resistance R 7 one ends connect V
CC, the other end connects capacitor C 1 in node A, and collector electrode, the emitter of capacitor C 1 two ends cross-over connection transistor Q2.T during R7 resistance value by adjusting timing circuit 130 and C1 capacitance can determine to set
ON, turn-off to form when opening circuit at transistor Q2, capacitor C 1 will begin charging and during setting T
ONForm reference voltage V at node A during end
REF
Start-up circuit 140 comprises NPN transistor Q1 and PNP transistor Q3.The emitter of the emitter of transistor Q1 and transistor Q3 is connected to the node A of timing circuit 130 together, and the collector electrode of transistor Q1 connects V via resistance R 2
CCThe collector electrode of transistor Q3 then is connected to ground (ground), the base stage of transistor Q1 connects the bleeder circuit that formed by resistance R 3, R6 with receiving inputted signal ON/OFF, and similarly, the base stage of transistor Q3 then connects the bleeder circuit that formed by resistance R 4, R5 with receiving inputted signal ON/OFF.When backlight module starts, input signal ON/OFF is a logic high, fluorescent tube LP1 does not begin discharge as yet, so testing circuit 120 detects less than lamp current transistor Q2 shutoff formation is opened circuit, this moment, the capacitor C 1 of timing circuit 130 began charging by zero potential, and the difference between the voltage of the voltage of input signal ON/OFF and node A is enough to make transistor Q1 conducting, and in other words, the base stage of transistor Q1 is V via the base voltage that resistance R 3, R6 dividing potential drop input signal ON/OFF form
B1And the voltage V on the node A
A, therefore, the voltage difference V between transistor Q1 base, emitter
B1-V
ACan allow transistor Q1 be operated in saturated (saturation) district, the result on the collector electrode of transistor Q1, produce logic low (that is: enabling signal S first signal value), and drive circuit 110 receive the enabling signal S of logic low after the output starting resistor give fluorescent tube LP1, as long as voltage difference V
B1-V
ABe enough to turn-on transistor Q1, drive circuit 110 just can be continuously applied starting resistor with ignition fluorescent tube LP1 in the required light-off time of fluorescent tube LP1.Adjust the resistance R 3 of resistance R 7, capacitor C 1 and the bleeder circuit of timing circuit 130, the part value of R6, can change the length and the dividing potential drop V in 1 charging interval of capacitor C
B1Size, just can control and apply the light-off time of starting resistor, to be suitable for different discharge lamps in discharge lamp.
If fluorescent tube LP1 can ignition, testing circuit 120 detects electric current, and turn-on transistor Q2 makes node A be connected to ground by fluorescent tube LP1, therefore transistor Q1 keeps conducting state to continue to provide the enabling signal S of logic low, on the other hand, drive circuit 110 drops to output voltage by the lamp current of feedback the normal working voltage of fluorescent tube LP1.If fluorescent tube LP1 installs as yet, or fluorescent tube LP1 loose contact, fault even take place when operation, testing circuit 120 can't detect electric current and turn-off transistor Q2, makes capacitor C 1 begin charging, T during through one section setting
ONAfter, node A forms reference voltage V
A=V
REF, the voltage difference V between this moment transistor Q1 base, emitter
B1-V
ACan't allow transistor Q1 be operated in the saturation region, transistor Q1 is turn-offed, the result on the collector electrode of transistor Q1, produce logic high (that is: the enabling signal S secondary signal value) and turn-off drive circuit 110 to avoid exporting excessive voltage constantly.
In the preferred embodiment of Fig. 2, the transistor Q3 of start-up circuit 140 and relevant bleeder circuit R4, R5 are as the repid discharge path of capacitor C 1.When input signal ON/OFF is logic high, turn-offs transistor Q3 formation and open circuit; When turn-offing drive circuit, input signal ON/OFF transfers logic low to, the base voltage V that resistance R 4, R5 dividing potential drop input signal ON/OFF form
B2Make transistor Q3 conducting, thus, the electric charge that capacitor C 1 stores can remove apace via transistor Q3.
Comprehensive the above; discharge lamp circuit disclosed by the invention; the resistance R 3 of resistance R 7, capacitor C 1 and bleeder circuit by adjusting timing circuit 130, the part numerical value of R6; just can control and apply the light-off time of starting resistor in discharge lamp; and, install as yet at fluorescent tube, or the fluorescent tube loose contact takes place when operation, even under the situation of fault; start-up circuit 140 turn-offs drive circuit 110 to avoid exporting excessive voltage constantly, to reach the purpose of overvoltage protection.
Though the present invention with a specific embodiment openly as above; so it is only in order to be easy to illustrate technology contents of the present invention; and be not with narrow sense of the present invention be defined in this embodiment; those skilled in the art; under the situation that does not break away from the spirit and scope of the present invention; can change and variation, so protection scope of the present invention is as the criterion with the scope that claim was defined that is proposed.
Claims (13)
1. a may command light-off time and discharge lamp circuit with overvoltage protection comprise:
One drive circuit is in order to a starting resistor that produces a discharge lamp and the lamp current that this discharge lamp of flowing through is provided;
One testing circuit is in order to detect this lamp current;
One timing circuit is controlled by this testing circuit, forms a reference voltage during in order to end during sets, and controls the light-off time of this discharge lamp by this; And
One start-up circuit, be connected respectively to drive circuit and timing circuit, it is in order to before forming this reference voltage, make this drive circuit can be in the light-off time of this discharge lamp, be continuously applied this starting resistor in this discharge lamp with this discharge lamp of ignition, and when detecting less than this lamp current, turn-off this drive circuit at this testing circuit.
2. discharge lamp circuit as claimed in claim 1, wherein said timing circuit comprises resistance and an electric capacity, and this electric capacity connects this resistance in a node, by adjusting this resistance value and this capacitance, and form described reference voltage at this node can during described setting, finish the time with during determining described setting.
3. discharge lamp circuit as claimed in claim 2, wherein said start-up circuit comprises that one first switching device receives an input signal to provide an enabling signal to described drive circuit, this first switching device connects the described node of described timing circuit, if the difference between the voltage of the voltage of this input signal and described node is enough to make this first switching device conducting, then this enabling signal of Chan Shenging is that one first signal value is to start described drive circuit.
4. discharge lamp circuit as claimed in claim 3, wherein said testing circuit comprise that a second switch device is connected to described electric capacity, and when described testing circuit detected described lamp current, this second switch device of conducting made described capacitor discharge.
5. discharge lamp circuit as claimed in claim 4, wherein said testing circuit is when detecting less than described lamp current, described second switch device turn-offs to form and opens circuit, and forms described reference voltage at described node when making described electric capacity charging with end during described setting.
6. discharge lamp circuit as claimed in claim 5, wherein said second switch device forms to open circuit and makes described electric capacity charging, and form described reference voltage at described node when during described setting, finishing, cause the voltage of described input signal and the difference between described reference voltage that described first switching device of described start-up circuit is formed and open circuit, the described enabling signal that described start-up circuit is produced is that a secondary signal value is to turn-off described drive circuit.
7. discharge lamp circuit as claimed in claim 6, wherein said start-up circuit comprise that also one the 3rd switching device is connected to described electric capacity, in order to when turn-offing described drive circuit, make described electric capacity repid discharge.
8. a may command light-off time and discharge lamp circuit with overvoltage protection comprise:
One drive circuit is in order to a starting resistor that produces a discharge lamp and the lamp current that this discharge lamp of flowing through is provided;
One testing circuit is connected to this discharge lamp, in order to detect this lamp current;
One timing circuit, an electric capacity that comprises a resistance and be connected to this testing circuit, and this electric capacity connects this resistance in a node, by adjusting this resistance value and this capacitance with during determining one to set, form a reference voltage at this node during in order to end during this setting, control the light-off time of this discharge lamp by this; And
One start-up circuit, comprise a first transistor, it is connected to this node of this timing circuit, in order to before forming this reference voltage on this node, to make this first transistor be in conducting state, allow this drive circuit can be in the light-off time of this discharge lamp, be continuously applied this starting resistor in this discharge lamp with this discharge lamp of ignition, and in order to detect less than this lamp current at this testing circuit, and when making this node during this setting, finish to form this reference voltage, make this first transistor be in off-state to turn-off this drive circuit.
9. discharge lamp circuit as claimed in claim 8, wherein said start-up circuit receives an input signal to provide an enabling signal to described drive circuit, if the difference between the voltage of the voltage of this input signal and described node is enough to make described the first transistor to be in described conducting state, then this enabling signal of Chan Shenging is that one first signal value is to start described drive circuit.
10. discharge lamp circuit as claimed in claim 9, wherein said testing circuit comprises a transistor seconds, and it is connected to described electric capacity, when described testing circuit detects described lamp current, this transistor seconds becomes described conducting state, makes described capacitor discharge.
11. discharge lamp circuit as claimed in claim 10, wherein said testing circuit is when detecting less than described lamp current, described transistor seconds becomes described off-state, forms described reference voltage at described node when making described electric capacity charging with end during described setting.
12. discharge lamp circuit as claimed in claim 11, wherein said transistor seconds is in described off-state makes described electric capacity charging, and form described reference voltage at described node when during described setting, finishing, cause the voltage and the difference between described reference voltage of described input signal to cause that described the first transistor transfers described off-state to, the described enabling signal that described start-up circuit is produced is that a secondary signal value is to turn-off described drive circuit.
13. discharge lamp circuit as claimed in claim 12, wherein said start-up circuit also comprise one the 3rd transistor, it is connected to described electric capacity, in order to when turn-offing described drive circuit, makes described electric capacity repid discharge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021418659A CN100397955C (en) | 2002-08-27 | 2002-08-27 | Discharging fluorescent tube circuit capable of controlling starating time and possessing overvoltage protection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021418659A CN100397955C (en) | 2002-08-27 | 2002-08-27 | Discharging fluorescent tube circuit capable of controlling starating time and possessing overvoltage protection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1479563A CN1479563A (en) | 2004-03-03 |
| CN100397955C true CN100397955C (en) | 2008-06-25 |
Family
ID=34147892
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB021418659A Expired - Lifetime CN100397955C (en) | 2002-08-27 | 2002-08-27 | Discharging fluorescent tube circuit capable of controlling starating time and possessing overvoltage protection |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100397955C (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11283785A (en) * | 1998-03-30 | 1999-10-15 | Toshiba Lighting & Technology Corp | Lighting device of discharge lamp |
| CN1275879A (en) * | 1999-05-26 | 2000-12-06 | 松下电工株式会社 | Ballast for electric discharge lamp |
| US20020101696A1 (en) * | 2000-08-15 | 2002-08-01 | Murata Manufacturing Co., Ltd. | High voltage power supply device for lighting disharge tube having fault protection circuit and fault protection circuit |
-
2002
- 2002-08-27 CN CNB021418659A patent/CN100397955C/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11283785A (en) * | 1998-03-30 | 1999-10-15 | Toshiba Lighting & Technology Corp | Lighting device of discharge lamp |
| CN1275879A (en) * | 1999-05-26 | 2000-12-06 | 松下电工株式会社 | Ballast for electric discharge lamp |
| US20020101696A1 (en) * | 2000-08-15 | 2002-08-01 | Murata Manufacturing Co., Ltd. | High voltage power supply device for lighting disharge tube having fault protection circuit and fault protection circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1479563A (en) | 2004-03-03 |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| ASS | Succession or assignment of patent right |
Owner name: CHINA NATIONAL HEAVY DUTY TRUCK GROUP JINAN POWER Free format text: FORMER OWNER: JINAN TECH CENTER CO., LTD., CHINA HEAVY TRUCK GROUP Effective date: 20101027 |
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| C56 | Change in the name or address of the patentee | ||
| CP01 | Change in the name or title of a patent holder |
Address after: China Taiwan Taoyuan County Patentee after: Qisda Corp. Address before: China Taiwan Taoyuan County Patentee before: Benq Corp. |
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| CX01 | Expiry of patent term |
Granted publication date: 20080625 |
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| CX01 | Expiry of patent term |