CN101102635B - Lamp tube current feedback and open circuit protection circuit - Google Patents
Lamp tube current feedback and open circuit protection circuit Download PDFInfo
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- CN101102635B CN101102635B CN2006100615139A CN200610061513A CN101102635B CN 101102635 B CN101102635 B CN 101102635B CN 2006100615139 A CN2006100615139 A CN 2006100615139A CN 200610061513 A CN200610061513 A CN 200610061513A CN 101102635 B CN101102635 B CN 101102635B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
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Abstract
The invention provides lamp current feedback and an open circuit protective circuit, which includes a detection circuit, a pulse width modulation IC and an input circuit. The pulse width modulation IC includes a current sampling terminal and stops work when the current sampling terminal is in a low voltage state, which is characterized in that the detection circuit comprises at least a backlight luminous tube and a detection output terminal; when any backlight luminous tube turns on, the detection output terminal generates a low voltage signal, the input circuit includes a resistance of which one terminal is connected to the current sampling terminal of the pulse width modulation IC, and the other terminal is used as an input terminal of the input circuit, and the detection output terminal of the detection circuit is electrically connected to the input terminal of the input circuit.
Description
Technical field
The invention relates to a kind of lamp current feedback and open loop protection circuit, especially about a kind of lamp current feedback and open loop protection circuit that is used for liquid crystal indicator.
Background technology
Therefore advantages such as liquid crystal indicator has gently, approaches, power consumption is little are widely used in modernized information equipments such as TV, notebook computer, mobile phone, personal digital assistant.Because the liquid crystal molecule itself in the liquid crystal indicator is not luminous, therefore liquid crystal indicator needs to show by the luminous image of realizing of a module backlight, common module backlight comprises the pulse-width modulation integrated circuit of a plurality of backlight lamp tubes and these a plurality of backlight lamp tube operating currents of adjusting, when the backlight lamp tube operate as normal, need a feedback circuit with the backlight lamp tube current feedback to this pulse-width modulation integrated circuit with the Control work electric current.When backlight tube open circuit or short circuit, protect this pulse-width modulation integrated circuit thereby need a protective circuit that this pulse-width modulation integrated circuit is quit work.
See also Fig. 1, it is a kind of prior art lamp current feedback and open loop protection circuit schematic diagram.Describe for convenient, existing situation with four backlight lamp tubes is that example describes.This lamp current feedback and open loop protection circuit 1 comprise: first to fourth testing circuit, 11,12,13,14, one input circuit 16, one control switchs, 17, one feedback circuits 18 and pulse-width modulation integrated circuits 19.
This first testing circuit 11 comprises that first backlight lamp tube 11 and first detects output 110, this second testing circuit 12 comprises that second backlight lamp tube 121 and second detects output 120, this three testing circuit 13 comprises that the 3rd backlight lamp tube 131 and the 3rd detects output 130, the four testing circuits 14 and comprises that the 4th backlight lamp tube 141 and the 4th detects output 140.
This input circuit 16 comprises: first to fourth transistor 161,162,163,164, first to fourth diodes, 1601,1602,1603,1604, four biasing resistors 165 and four filter capacitors 166.The grounded drain of this first transistor 161, its source electrode is connected with the drain electrode of this transistor seconds 162, the source electrode of this transistor seconds 162 is connected with the drain electrode of the 3rd transistor 163, the source electrode of the 3rd transistor 163 is connected with the drain electrode of the 4th transistor 164, and the source electrode of the 4th transistor 164 is outputs of this input circuit 16.The grid of this first transistor 161 is by a biasing resistor 165 and a filter capacitor 166 ground connection in parallel, the negative electricity of this first diode 1601 is connected to the grid of this first transistor 161, and the positive pole of this first diode 1601 is as the first input end of this input circuit 16.The grid syndeton of this second to the 4th transistor 162,163,164 is identical with the grid syndeton of this first transistor 161, the positive pole of this second to the 4th diode 1602,1603,1604 respectively as this input circuit 16 second to four-input terminal.
This pulse-width modulation integrated circuit 19 comprises a current sample end 191, and when this current sample end 191 was drawn to low-voltage, this pulse-width modulation integrated circuit 19 quit work.
This control switch 17 comprises one the 5th transistor 171 and a current-limiting resistance 172, the grounded drain of the 5th transistor 171, the source electrode of the 5th transistor 171 is electrically connected to the grid of current sample end 191, the five transistors 171 of this pulse-width modulation integrated circuit 19 and the source electrode of the 4th transistor 164 is electrically connected to a 5V power supply (pin of pulse-width modulation integrated circuit) by this current-limiting resistance 172 simultaneously.
This feedback circuit 18 comprises first and second feedback resistance 181,182, one end of this first, second feedback resistance 181,182 all is connected with the current sample end 191 of this pulse-width modulation integrated circuit 19, its other end is respectively as first, second feedback input end of this feedback circuit 18, this first feedback input end is used to receive the voltage signal of this first detection output 110 or this second detection output, 120 outputs, and this second feedback input end is used to receive the 3rd detection output 130 or the 4th and detects the voltage signal that output 140 is exported.
During operate as normal, these first to fourth detection output, 110,120,130,140 equal output HIGH voltage signals, this four high voltage signal makes this first to fourth transistor 161,162,163,164 all open by this first to fourth diode 1601,1602,1603,1604, then the source electrode of the 4th transistor 164 by drop-down be low-voltage, so the 5th transistor 171 is closed.This first, the 3rd high voltage signal that detects output 110,130 or this second, the 4th detection output 120,140 outputs feeds back to the current sample end 191 of this pulse-width modulation integrated circuit 19 to measure the size of this backlight lamp tube electric current by this first, second feedback resistance 181,182 simultaneously.
When backlight tube open circuit, for convenience of description, be the example explanation now: behind these first backlight lamp tube, 111 open circuits with first backlight lamp tube, 111 open circuits, this first detection output 110 produces a low voltage signal, this low voltage signal makes this first transistor 161 close by this first diode 1601, and promptly the grid of the 5th transistor 171 disconnects with ground.Because the grid of the 5th transistor 171 is electrically connected to a power supply by this current-limiting resistance 172, therefore the grid of the 5th transistor 171 is a high voltage, the 5th transistor 171 is opened, and this current sample end 191 is drawn to be low-voltage, and this pulse-width modulation integrated circuit 19 quits work.
This lamp current feedback and open loop protection circuit 1 adopt this input circuit 16, control switch 17 and feedback circuit 18 to realize lamp current feedback and open circuit protecting function, and circuit structure is complicated.And each backlight lamp tube all corresponding one detects output, and when the backlight lamp tube that adopts increased, this detection output and electronic component also needed corresponding increase, further increase cost.
Summary of the invention
In order to solve feedback of lamp current in the prior art and open loop protection circuit complex structure, problem that cost is high, the invention provides a kind of lamp current feedback simple in structure, lower-cost and open loop protection circuit.
A kind of lamp current feedback and open loop protection circuit, it comprises at least one testing circuit, at least one input circuit and a pulse-width modulation integrated circuit.Each testing circuit comprises that at least one backlight lamp tube and detects output, and this detection output produces a low voltage signal when arbitrary backlight tube open circuit.This pulse-width modulation integrated circuit comprises a current sample end, and when this current sample end was drawn to low-voltage, this pulse-width modulation integrated circuit quit work.Each input circuit comprises a resistance, and this resistance one end connects the current sample end of this pulse-width modulation integrated circuit, and its other end is as the input of this input circuit.The detection output of this at least one testing circuit is electrically connected with the input of this at least one input circuit respectively.
Lamp current feedback of the present invention and open loop protection circuit only need can be realized the function of input circuit in the prior art, control switch and feedback circuit by the input circuit that resistance and diode constitute; and testing circuit is transformed, and per two backlight lamp tubes only need a detection output to get final product.Compared with prior art, lamp current feedback of the present invention and open loop protection circuit circuit structure are simple, and cost is low.
Description of drawings
Fig. 1 is a kind of prior art lamp current feedback and open loop protection circuit schematic diagram.
Fig. 2 is the schematic diagram of lamp current feedback of the present invention and open loop protection circuit.
Fig. 3 is the schematic diagram of backlight lamp tube lamp current feedback and open loop protection circuit when being one.
Fig. 4 is the schematic diagram of backlight lamp tube lamp current feedback and open loop protection circuit when being two.
Fig. 5 is the schematic diagram of backlight lamp tube lamp current feedback and open loop protection circuit when being six.
Embodiment
See also Fig. 2, it is the schematic diagram of lamp current feedback of the present invention and open loop protection circuit.Describe for convenient, existing situation with four backlight lamp tubes is that example describes.This lamp current feedback and open loop protection circuit 2 comprise one first testing circuit 21, one second testing circuit 22, one first input circuit 24, one second input circuit 25 and a pulse-width modulation integrated circuit 26.
This first testing circuit 21 comprises that one first backlight lamp tube 211, one second backlight lamp tube 212 and one first detect output 210, and this second testing circuit 22 comprises that one the 3rd backlight lamp tube 221, one the 4th backlight lamp tube 222 and one second detect output 220.This backlight lamp tube is cold cathode ray tube or light-emitting diode.
This pulse-width modulation integrated circuit 26 comprises a current sample end 261, and when this current sample end 261 was drawn to low-voltage, this pulse-width modulation integrated circuit 26 quit work.
This first input circuit 24 comprises first resistance 241 and first diode 242 of a parallel connection, the anode of this first diode 242 connects the current sample end 261 of this pulse-width modulation integrated circuit 26, and the negative electrode of this first diode 242 is as the input 240 of this input circuit 24.This second input circuit 25 comprises second resistance 251 and second diode 252 of a parallel connection, the anode of this second diode 252 connects the current sample end 261 of this pulse-width modulation integrated circuit 26, and the negative electrode of this second diode 252 is as the input 250 of this input circuit 25.The span of this first, second resistance 241,251 be 0.1 kilo-ohm to 1 megaohm, preferred value is 33 kilo-ohms.This first, second diode the 242, the 252nd, B AW 56 type diodes.
During operate as normal, first, second of this first and second testing circuit 21,22 detects output 210,220 equal output HIGH voltage signals, and this high voltage signal feeds back to the current sample end 261 of this pulse-width modulation integrated circuit 26 to measure the size of backlight lamp tube electric current by this first, second resistance 241,251 respectively.
When backlight tube open circuit, for convenience of description, be the example explanation with first backlight lamp tube, 211 open circuits now: behind these first backlight lamp tube, 211 open circuits, the voltage signal that this first testing circuit 21 is sampled to is 0 substantially, and promptly the input 240 of this first input circuit 24 is a low voltage signal.This second detection output 220 is still exported a high voltage signal, this high voltage signal feeds back to the current sample end 261 of this pulse-width modulation integrated circuit 26 by this second resistance 251, at this moment, the anode of this first diode 242 loads high voltage signal, its negative electrode loads low voltage signal, these first diode, 242 conductings, the high voltage signal that this current sample end 261 loads is dragged down is low voltage signal, this pulse-width modulation integrated circuit 26 quits work.Operation principles and said process when the 3rd fluorescent tube 221 is open circuit are in full accord.This second fluorescent tube 212 is connected with this first fluorescent tube 211, and when these second fluorescent tube, 212 open circuits, the voltage signal that this first testing circuit 21 is sampled to also is 0 substantially, so it is equivalent to first fluorescent tube, 211 open circuits.The operation principles and second fluorescent tube 212 of the 4th fluorescent tube 222 open circuits are in full accord.
Lamp current of the present invention feedback and open loop protection circuit 2 only need can be realized the function of input circuit 16 in the prior art, control switch 17 and feedback circuit 18 by first, second input circuit 24,25 that two resistance and two diodes constitute; and testing circuit is transformed, and four backlight lamp tubes only need two detection outputs to get final product.Compared to prior art, lamp current feedback of the present invention and open loop protection circuit 2 circuit structures are simple, and cost is low.
When the backlight lamp tube number changes, lamp current feedback and the also corresponding change of open loop protection circuit.For example; when backlight lamp tube is one or two; corresponding lamp current feedback and open loop protection circuit 3,4 are respectively as shown in Figures 3 and 4; at this moment; this input circuit 34,44 only needs a resistance 341,441 to realize; these resistance 341,441 1 ends connect the current sample end 361,461 of this pulse-width modulation integrated circuit 36,46, and its other end is as the input 340,440 of this input circuit.The detection output 310,410 of this testing circuit 31,41 is electrically connected with the input 340,440 of this input circuit 34,44.When backlight lamp tube is six; corresponding lamp current feedback and open loop protection circuit 5 as shown in Figure 5, this lamp current feedback and open loop protection circuit 5 increase by a testing circuit 53 on the basis of lamp current feedback shown in Figure 2 and open loop protection circuit 2 and an input circuit 57 gets final product.
Claims (10)
1. a lamp current feeds back and open loop protection circuit; it comprises at least one testing circuit; one pulse-width modulation integrated circuit and at least one input circuit; this pulse-width modulation integrated circuit comprises a current sample end; this pulse-width modulation integrated circuit quits work when this current sample end is drawn to low-voltage; it is characterized in that: each testing circuit comprises that at least one backlight lamp tube and detects output; this detection output produces a low voltage signal when arbitrary backlight tube open circuit; each input circuit comprises a resistance; this resistance one end connects the current sample end of this pulse-width modulation integrated circuit; the other end is as the input of this input circuit, and the detection output of this at least one testing circuit is electrically connected with the input of this at least one input circuit respectively.
2. lamp current feedback as claimed in claim 1 and open loop protection circuit; it is characterized in that: each input circuit further comprises a diode; this resistance is in parallel with this diode; the anode of this diode connects the current sample end of this pulse-width modulation integrated circuit, and the negative electrode of this diode is as the input of this input circuit.
3. lamp current feedback as claimed in claim 1 and open loop protection circuit, it is characterized in that: this at least one testing circuit is two, this at least one input circuit is two.
4. lamp current feedback as claimed in claim 1 and open loop protection circuit, it is characterized in that: this at least one testing circuit is three, this at least one input circuit is three.
5. lamp current as claimed in claim 1 feedback and open loop protection circuit is characterized in that: the span of this at least one input circuit resistance be 0.1 kilo-ohm to 1 megaohm.
6. lamp current feedback as claimed in claim 5 and open loop protection circuit, it is characterized in that: the resistance value of this at least one input circuit resistance is 33 kilo-ohms.
7. lamp current feedback as claimed in claim 2 and open loop protection circuit, it is characterized in that: the diode of this at least one input circuit is a BAW56 type diode.
8. lamp current feedback as claimed in claim 1 and open loop protection circuit, it is characterized in that: this backlight lamp tube is cold cathode ray tube or light-emitting diode.
9. lamp current feedback as claimed in claim 1 and open loop protection circuit, it is characterized in that: the backlight lamp tube of this at least one testing circuit is two.
10. lamp current feedback as claimed in claim 1 and open loop protection circuit, it is characterized in that: the backlight lamp tube of this at least one testing circuit is one.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2006100615139A CN101102635B (en) | 2006-07-05 | 2006-07-05 | Lamp tube current feedback and open circuit protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2006100615139A CN101102635B (en) | 2006-07-05 | 2006-07-05 | Lamp tube current feedback and open circuit protection circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101102635A CN101102635A (en) | 2008-01-09 |
| CN101102635B true CN101102635B (en) | 2011-12-14 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2006100615139A Expired - Fee Related CN101102635B (en) | 2006-07-05 | 2006-07-05 | Lamp tube current feedback and open circuit protection circuit |
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| Country | Link |
|---|---|
| CN (1) | CN101102635B (en) |
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- 2006-07-05 CN CN2006100615139A patent/CN101102635B/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| CN101102635A (en) | 2008-01-09 |
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| ASS | Succession or assignment of patent right |
Owner name: QIMEI ELECTRONIC CO LTD Free format text: FORMER OWNER: INNOLUX DISPLAY CORPORATION |
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Effective date of registration: 20111021 Address after: 518109 Longhua, Shenzhen, town, Foxconn science and Technology Industrial Park E District, building 1, floor 4, Applicant after: Qunkang Technology (Shenzhen) Co., Ltd. Co-applicant after: Chimei Optoelectronics Co., Ltd. Address before: 518109 Longhua, Shenzhen, town, Foxconn science and Technology Industrial Park E District, building 1, floor 4, Applicant before: Qunkang Technology (Shenzhen) Co., Ltd. Co-applicant before: Innolux Display Group |
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