CN101925245A - Inverter duty cycle control method and duty cycle controller for lamp - Google Patents
Inverter duty cycle control method and duty cycle controller for lamp Download PDFInfo
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Abstract
The present invention provides a method of controlling generation of a duty ratio control signal for controlling a duty ratio of an output of an inverter for driving a lamp such as a CCFL or EEFL, which is capable of reducing a current flowing through the inverter or the like when the lamp is short-circuited. The method comprises the following steps: under a normal working state, generating a regulating voltage based on a normal reference voltage and a feedback lamp current, and generating a duty ratio control signal based on the regulating voltage so as to keep the duty ratio at a normal working value; when a short circuit occurs, an adjustment voltage is generated based on the short circuit reference voltage and the feedback lamp current, and a duty ratio control signal is generated based on the adjustment voltage to reduce the duty ratio. The invention also provides a duty ratio controller for realizing the method.
Description
Technical field
The present invention generally relates to cold-cathode fluorescence lamp (CCFL) and external electrode fluorescence lamp (EEFL), relates more specifically to be used for the inverter duty cycle control method of CCFL and EEFL.
Background technology
CCFL is a kind of sealing fluorescent tube of interior filling with inert gas.When applying alternating voltage to fluorescent tube, inert gas is ionized, and produces ultraviolet ray.The fluorescent material of ultraviolet irradiation tube inner wall coating excites it, thereby sends visible light.CCFL has advantages such as high brightness, low-power consumption, low cost, is widely used in for example various fields such as display device, advertising lamp box, business automation equipment and automotive lighting.
The metal electrode that EEFL is adhered to by sealed glass pipe and outside, glass tube two ends constitutes, be filled with inert gas in the glass tube, inner surface scribbles phosphor powder layer, and the electric field that produces between its external metal electrode forms plasma in glass tube, thereby makes lamp luminescence.That EEFL has is energy-conservation, low, the luminous advantage such as evenly of long service life, temperature, therefore obtains application more and more widely in fields such as industry and daily illuminations.
CCFL and the required alternating voltage of EEFL work are provided by inverter and transformer.As shown in Figure 1, inverter 11 receives dc voltage input V
DC, produce alternating voltage V
AC1Offer transformer 12.Transformer 12 is with alternating voltage V
AC1Convert alternating voltage V to
AC2, and export this V
AC2To drive lamp 13, lamp 13 can be CCFL or EEFL.
Short circuit may appear in the use of CCFL and EEFL.For example, the hot junction (end that links to each other with transformer) of human body touching lamp, perhaps the framework short circuit of lamp and support panel all may cause short circuit.Fig. 2 shows the method for test short circuit current.The hot junction of lamp 13 is shorted to ground GND by artifical resistance (dummy resistor) 21, and the electric current of the artifical resistance 21 of flowing through is exactly a short circuit current.
Find that by measuring for CCFL, short circuit current is less, its resonant inductance (the normally leakage inductance of transformer) is bigger.When the hot junction of lamp was shorted to ground by artifical resistance, short circuit current can be restricted to a less value by resonant inductance.
Yet for EEFL, the lamp current under the normal operating state is bigger, and resonant inductance is less.When short circuit occurring, short circuit current is more much bigger than the short circuit current that meets security requirement usually, thereby causes device failure.Therefore, need a kind of being used to limit the short circuit current of EEFL so that it satisfies the method for security requirement.
Prior art is closed inverter after being short-circuited.Yet owing to can not before closing inverter short circuit current be restricted to a less value, the device in the circuit still has impaired possibility.
Summary of the invention
According to the above-mentioned one or more an open questions that exist in the prior art the present invention is proposed.
The invention provides the method for duty cycle control signal that a kind of generation is used for the duty ratio of control inverter output, described inverter is used to drive lamp, and this method comprises: when lamp is short-circuited, produce regulation voltage based on short circuit reference voltage and feedback lamp current; And based on regulation voltage generation duty cycle control signal, to reduce the duty ratio of described inverter.
The present invention also provides the occupancy controller of the duty cycle control signal of the duty ratio that a kind of generation is used for control inverter output, described inverter is used to drive lamp, described occupancy controller comprises: adjuster is used for producing regulation voltage based on short circuit reference voltage and feedback lamp current when lamp is short-circuited; And the duty ratio setting apparatus, be used for producing duty cycle control signal, thereby when being short-circuited, reduce the duty ratio of described inverter based on regulation voltage.
Description of drawings
In conjunction with the accompanying drawings, according to the following explanation to exemplary embodiment, above-mentioned and/or other aspects of general plotting of the present invention will become apparent and be easier to understand, in the accompanying drawings:
Fig. 1 shows the device schematic diagram that drives CCFL or EEFL;
Fig. 2 shows the method for test short circuit current;
Fig. 3 shows the duty ratio control principle according to the embodiment of the invention;
Fig. 4 shows the occupancy controller according to the embodiment of the invention;
Fig. 5 A shows the duty ratio control procedure according to the embodiment of the invention;
Fig. 5 B shows the duty ratio control method according to the embodiment of the invention; And
Fig. 5 C shows the duty ratio control method according to the embodiment of the invention.
Embodiment
Present with detailed embodiment with reference to general plotting of the present invention, the example of these embodiment shown in the drawings, wherein similarly Reference numeral refers to similar elements.Below embodiment is described so that explain general plotting of the present invention by the reference accompanying drawing.
The size of lamp current is relevant with the duty ratio of the output voltage of inverter.When duty ratio was big, lamp current was also bigger; When duty ratio hour, lamp current is also less.Therefore, can recently control lamp current, and when being short-circuited, recently reduce lamp current by reducing duty by the control duty, thus the electric current of devices such as the inverter that reduces under short-circuit condition, to flow through.
Fig. 3 schematically shows the duty ratio control principle according to the embodiment of the invention.As shown in Figure 3, inverter 11 receives dc voltage input V
DC, produce alternating voltage V
AC1Offer transformer 12.Transformer 12 is with alternating voltage V
AC1Convert alternating voltage V to
AC2, and export this V
AC2To drive lamp 13.Occupancy controller 31 receives feedback lamp current from lamp 13 as input.The feedback lamp current can equal the lamp current of lamp 13, also can equal the part of the lamp current of lamp 13.In this article, " lamp current " refers to the electric current via the hot junction inflow of lamp 13.
(being the normal work period after lamp is lighted) in normal operation, short-circuit signal is invalid.Occupancy controller is regulated the duty ratio of inverter output voltage based on the feedback lamp current, thereby lamp current is remained running current.
When lamp was short-circuited, short-circuit signal was effective, and occupancy controller reduces the duty ratio of inverter output voltage based on the feedback lamp current, reducing lamp current, thus the electric current of devices such as the inverter that reduces to flow through.
Preferably, after detecting short circuit, occupancy controller 31 can closed inverter through after the predetermined amount of time.
It will be understood by those skilled in the art that and can adopt several different methods known in the art to detect short circuit, for example can detect the modulating voltage of lamp 13 so that short-circuit signal to be provided, when its during less than predetermined threshold, determine to be short-circuited, and make short-circuit signal effective.
Fig. 4 schematically shows the occupancy controller 31 according to the embodiment of the invention.As shown in Figure 4, occupancy controller 31 comprises adjuster 41, duty ratio setting apparatus 42, switching device shifter 43.Preferably, occupancy controller 31 also comprises timer 44.
First input of adjuster 41 receives the feedback lamp current, and second input is connected to normal reference voltage V1 or short circuit reference voltage V2 via switching device shifter 43, and output is connected to duty ratio setting apparatus 42.Switching device shifter 43 is connected to normal reference voltage V1 or short circuit reference voltage V2 second input of adjuster 41 under the control of short-circuit signal.When short-circuit signal was invalid, switching device shifter 43 was connected to second of adjuster 41 with normal reference voltage V1 and imports, and when short-circuit signal was effective, switching device shifter 43 was connected to short circuit reference voltage V2 second input of adjuster 41.Wherein, normal reference voltage V1 is corresponding to the normality threshold of feedback lamp current, and short circuit reference voltage V2 is corresponding to the default short circuit threshold value of feedback lamp current, V1＞V2.
Adjuster 41 is based on feedback lamp current and normal or short circuit reference voltage (depending on that lamp is in normal operating conditions or short-circuit condition) generation regulation voltage Vadj.In normal operation, when the feedback lamp current was higher than normality threshold, regulation voltage reduced, and when feedback current was lower than normality threshold, regulation voltage increased; Under short-circuit condition, when the feedback lamp current was higher than the short circuit threshold value, regulation voltage reduced, and when feedback current was lower than the short circuit threshold value, regulation voltage increased.
Duty ratio setting apparatus 42 produces duty cycle control signal according to the regulation voltage of adjuster 41 outputs, with the duty ratio of control inverter.In normal operation, when the feedback lamp current was higher than normality threshold, regulation voltage reduced, and the duty ratio setting apparatus produces the duty cycle control signal that duty ratio is reduced, thereby reduces lamp current; When feedback current was lower than normality threshold, regulation voltage increased, and the duty ratio setting apparatus produces the duty cycle control signal that duty ratio is increased, thereby increased lamp current.In this way, lamp current is remained running current.
Under short-circuit condition, when the feedback lamp current was higher than the short circuit threshold value, regulation voltage reduced, and the duty ratio setting apparatus produces the duty cycle control signal that duty ratio is reduced, thereby reduces lamp current; When feedback current was lower than the short circuit threshold value, regulation voltage increased, and the duty ratio setting apparatus produces the duty cycle control signal that duty ratio is increased, thereby increased lamp current.Because under short-circuit condition, adjuster 41 produces regulation voltage based on short circuit reference voltage V2, therefore duty cycle control signal makes the duty ratio of inverter less than the duty ratio under the normal operating conditions, thereby makes lamp current under the short-circuit condition less than the lamp current under the normal operating conditions.
Can realize adjuster 41 in many ways; for example; it can comprise operational amplifier, is used for the pairing voltage of feedback lamp current is compared with normal or short circuit reference voltage (depending on that lamp is in normal operating conditions or short-circuit condition), with the output regulation voltage.
Can adopt multiple mode to realize duty ratio setting apparatus 42 according to the embodiment of the invention.For example, duty ratio setting apparatus 42 can comprise comparator 421, and its first input is connected to the output of adjuster 41, and second input is connected to triangular wave.Comparator 421 compares the output voltage of adjuster 41 and the voltage of triangular signal, and resulting two-value comparison signal is duty cycle control signal.
Below with reference to the duty ratio control procedure of Fig. 5 A description according to the embodiment of the invention.As shown in Figure 5, in normal operation, short-circuit signal is invalid, occupancy controller 31 produces regulation voltage based on normal reference voltage V1 and feedback lamp current, produce duty cycle control signal based on regulation voltage, will feed back lamp current and remain and the normal corresponding normality threshold of reference voltage V1.
At moment t
1Be short-circuited, short-circuit signal is effective, occupancy controller 31 produces regulation voltage based on short circuit reference voltage and feedback lamp current, produces duty cycle control signal based on regulation voltage, will feed back lamp current and be reduced to the corresponding short circuit threshold value with short circuit reference voltage V2.
Preferably, when short-circuit signal was effective, timer 44 picked up counting, and at moment t
2Close inverter, the vanishing of feedback lamp current.
Fig. 5 B shows the duty ratio control method according to the embodiment of the invention, is used for when being short-circuited, reducing lamp current, thus the electric current of the devices such as inverter that reduce to flow through.This method starts from step 501.In step 502, when being short-circuited, produce regulation voltage based on short circuit reference voltage and feedback lamp current.In step 503, produce duty cycle control signal based on regulation voltage, reducing duty ratio, thereby reduce lamp current and the electric current of device such as the inverter of flowing through.This method finishes in step 504.
Fig. 5 C shows the duty ratio control method according to the embodiment of the invention.With compare with reference to the described method of figure 5B, this method can also remain running current with lamp current in normal operation.This method starts from step 511.In step 512, produce regulation voltage based on normal reference voltage and feedback lamp current, produce duty cycle control signal based on regulation voltage, with the duty ratio of control inverter, thereby lamp current is remained running current.In step 513, judge whether to be short-circuited.If be not short-circuited, then method is returned step 512.If be short-circuited, then in step 514, produce regulation voltage based on short circuit reference voltage and feedback lamp current, produce duty cycle control signal based on regulation voltage, reducing duty ratio, thereby reduce lamp current and the electric current of device such as the inverter of flowing through.This method finishes at step 515 place.
According to embodiments of the invention, normal reference voltage is higher than the short circuit reference voltage.In normal operation, when the feedback lamp current was higher than normality threshold, regulation voltage reduced, and when feedback current was lower than normality threshold, regulation voltage increased.Under short-circuit condition, when the feedback lamp current was higher than the short circuit threshold value, regulation voltage reduced, and when feedback current was lower than the short circuit threshold value, regulation voltage increased.
According to embodiments of the invention, when regulation voltage increases, produce the duty cycle control signal that duty ratio is increased, when regulation voltage reduces, produce the duty cycle control signal that duty ratio is reduced.
According to embodiments of the invention, detect modulating voltage, when modulating voltage is lower than predetermined threshold, determine to be short-circuited.Preferably, after being short-circuited, close inverter through behind the predetermined amount of time.
According to embodiments of the invention, the feedback lamp current equals the part of lamp current or lamp current.
According to embodiments of the invention, produce duty cycle control signal based on regulation voltage and comprise regulation voltage is compared with the triangle wave voltage signal, with the two-value comparison signal of generation as duty cycle control signal.
Duty ratio control method of the present invention can reduce rapidly to flow through after the being short-circuited electric current of devices such as inverter avoids excessive short circuit current that device is caused damage.Occupancy controller of the present invention can be common to CCFL and EEFL, and it not only can play the effect of stablizing lamp current in normal operation, and can prevent device failure when being short-circuited.
Top description only is used to illustrate embodiments of the present invention, and does not really want to limit the scope of the invention.It should be appreciated by those skilled in the art that scope of the present invention is defined by the following claims.Any modification or partial replacement that does not break away from spirit of the present invention and principle all should fall within the scope of the present invention.
Claims (17)
1. a generation is used for the method for duty cycle control signal of the duty ratio of control inverter output, and described inverter is used to drive lamp, and this method comprises:
When lamp is short-circuited, produce regulation voltage based on short circuit reference voltage and feedback lamp current; And
Produce duty cycle control signal based on regulation voltage, to reduce the duty ratio of described inverter.
2. method according to claim 1 also comprises:
In normal operation, produce regulation voltage based on normal reference voltage and feedback lamp current; And
Produce duty cycle control signal based on regulation voltage, controlling the duty ratio of described inverter, thereby lamp current is remained running current.
3. method according to claim 2, wherein:
Normal reference voltage is higher than the short circuit reference voltage;
In normal operation, when the feedback lamp current is higher than with the normal corresponding normality threshold of reference voltage, reduce regulation voltage, when the feedback lamp current is lower than normality threshold, increase regulation voltage;
Under short-circuit condition, when the feedback lamp current is higher than with the corresponding short circuit threshold value of short circuit reference voltage, reduce regulation voltage, when the feedback lamp current is lower than the short circuit threshold value, increase regulation voltage.
4. method according to claim 1 and 2, wherein:
When regulation voltage increases, produce the duty cycle control signal that duty ratio is increased;
When regulation voltage reduces, produce the duty cycle control signal that duty ratio is reduced.
5. method according to claim 1 wherein when modulating voltage is lower than predetermined threshold, is determined to be short-circuited.
6. method according to claim 1 wherein after being short-circuited, is closed inverter through behind the predetermined amount of time.
7. method according to claim 1 is wherein fed back the part that lamp current equals lamp current or lamp current, and lamp current is the electric current via the hot junction inflow of lamp.
8. method according to claim 1 wherein produces duty cycle control signal based on regulation voltage and comprises:
Regulation voltage is compared with the triangle wave voltage signal, to produce two-value comparison signal as duty cycle control signal.
9. a generation is used for the occupancy controller of duty cycle control signal of the duty ratio of control inverter output, and described inverter is used to drive lamp, and described occupancy controller comprises:
Adjuster is used for producing regulation voltage based on short circuit reference voltage and feedback lamp current when lamp is short-circuited; And
The duty ratio setting apparatus is used for producing duty cycle control signal based on regulation voltage, thereby reduces the duty ratio of described inverter when being short-circuited.
10. occupancy controller according to claim 9, wherein:
In normal operation, adjuster produces regulation voltage based on normal reference voltage and feedback lamp current, the duty ratio setting apparatus produces duty cycle control signal based on regulation voltage, controlling the duty ratio of described inverter, thereby lamp current is remained running current.
11. occupancy controller according to claim 10, wherein:
Normal reference voltage is higher than the short circuit reference voltage;
In normal operation, when the feedback lamp current was higher than with the normal corresponding normality threshold of reference voltage, adjuster reduced regulation voltage, and when feedback current was lower than normality threshold, adjuster increased regulation voltage;
Under short-circuit condition, when the feedback lamp current was higher than with the corresponding short circuit threshold value of short circuit reference voltage, adjuster reduced regulation voltage, and when feedback current was lower than the short circuit threshold value, adjuster increased regulation voltage.
12. according to claim 9 or 10 described occupancy controllers, wherein:
The duty ratio setting apparatus produces the duty cycle control signal that duty ratio is increased when regulation voltage increases, when regulation voltage reduces, produce the duty cycle control signal that duty ratio is reduced.
13. occupancy controller according to claim 9 also comprises timer, is used for after being short-circuited, and closes inverter through behind the predetermined amount of time.
14. occupancy controller according to claim 9 wherein feeds back the part that lamp current equals lamp current or lamp current, lamp current is the electric current via the hot junction inflow of lamp.
15. occupancy controller according to claim 10, wherein:
Adjuster comprises first input and second input, and first input is connected to the feedback lamp current, and second input is connected to normal reference voltage or short circuit reference voltage via switching device shifter, and described switching device shifter is controlled by short-circuit signal; And
In normal operation, second input of adjuster is connected to normal reference voltage via switching device shifter, and when being short-circuited, second input of adjuster is connected to the short circuit reference voltage via switching device shifter.
16. occupancy controller according to claim 9, wherein adjuster comprises operational amplifier.
17. occupancy controller according to claim 9, wherein the duty ratio setting apparatus comprises comparator, is used for regulation voltage is compared with the triangle wave voltage signal, to produce the two-value comparison signal as duty cycle control signal.
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| CN2010102799970A CN101925245A (en) | 2010-09-09 | 2010-09-09 | Inverter duty cycle control method and duty cycle controller for lamp |
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|---|---|---|---|
| CN2010102799970A CN101925245A (en) | 2010-09-09 | 2010-09-09 | Inverter duty cycle control method and duty cycle controller for lamp |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104582174A (en) * | 2014-12-31 | 2015-04-29 | 无锡华润矽科微电子有限公司 | LED drive circuit with sampling resistor protecting function and drive method thereof |
| CN106300944A (en) * | 2016-08-06 | 2017-01-04 | 杰华特微电子（张家港）有限公司 | Over-current control circuit, cross method of flow control and apply its power-supply system |
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| CN101083865A (en) * | 2006-05-31 | 2007-12-05 | 美国芯源系统股份有限公司 | System and method for open lamp protection |
| CN101383503A (en) * | 2007-09-03 | 2009-03-11 | 深圳市汇川技术股份有限公司 | System and method for detecting short circuit to ground of motor |
| CN101689059A (en) * | 2007-03-05 | 2010-03-31 | 塔西软件开发有限及两合公司 | Method and firmware for controlling voltage and current in a fluorescent lamp array |
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2010
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| CN101083865A (en) * | 2006-05-31 | 2007-12-05 | 美国芯源系统股份有限公司 | System and method for open lamp protection |
| CN101689059A (en) * | 2007-03-05 | 2010-03-31 | 塔西软件开发有限及两合公司 | Method and firmware for controlling voltage and current in a fluorescent lamp array |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104582174A (en) * | 2014-12-31 | 2015-04-29 | 无锡华润矽科微电子有限公司 | LED drive circuit with sampling resistor protecting function and drive method thereof |
| CN104582174B (en) * | 2014-12-31 | 2017-08-25 | 无锡华润矽科微电子有限公司 | The LED drive circuit and its driving method protected with sampling resistor |
| CN106300944A (en) * | 2016-08-06 | 2017-01-04 | 杰华特微电子（张家港）有限公司 | Over-current control circuit, cross method of flow control and apply its power-supply system |
| CN106300944B (en) * | 2016-08-06 | 2018-12-14 | 杰华特微电子（张家港）有限公司 | Over-current control circuit crosses method of flow control and the power-supply system using it |
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Application publication date: 20101222 |