CN201489798U - Display device capable of improving optical uniformity and current sharing circuit - Google Patents
Display device capable of improving optical uniformity and current sharing circuit Download PDFInfo
- Publication number
- CN201489798U CN201489798U CN2009201615794U CN200920161579U CN201489798U CN 201489798 U CN201489798 U CN 201489798U CN 2009201615794 U CN2009201615794 U CN 2009201615794U CN 200920161579 U CN200920161579 U CN 200920161579U CN 201489798 U CN201489798 U CN 201489798U
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- light
- display device
- electric current
- emitting device
- plural groups
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Abstract
The utility model relates to a display device, which comprises a plurality of groups of parallel light emitting devices and a current sharing circuit. The current sharing circuit is used to balance the plurality of groups of current passing through the plurality of parallel light emitting devices. The current shafting circuit comprises a plurality of resistances, a plurality of switch assemblies and an operational amplifier. The first end of each switch assembly receives the corresponding current among the plurality of groups of current. The second end of each switch assembly is coupled with the corresponding resistance among the plurality of resistances. Each switch assembly comprises a control end. The positive input end of the operational amplifier receives first current among the plurality of groups of current, the negative input end of the operational amplifier receives second current among the plurality of groups of current and the output end of the operational amplifier is coupled with the control ends of the plurality of groups of switch assemblies.
Description
Technical field
The utility model is relevant to a kind of display device and flow equalizing circuit, refers to a kind of display device and flow equalizing circuit that promotes the optics uniformity coefficient especially.
Background technology
Light emitting diode (light-emitting diode, LED) have low power consumption, long service life, color saturation height, multiple advantages such as reaction velocity is fast, shatter-proof, withstand voltage and volume is little, therefore often be applied to LCD (liquid crystal display, LCD), scanner, advertising lamp box, or the back light in the electronic equipment such as mobile computer.Generally speaking, light-emitting diode lamp tube comprises the light emitting diode of a plurality of serial connections, therefore can provide line source according to the pointolite that each light emitting diode produced.Because the brightness of each light emitting diode is proportional to the electric current of flowing through on it, the light emitting diode number of serial connection is many more, and the light luminance that light-emitting diode lamp tube can provide is strong more, but also can cause higher voltage stress.
Please refer to Fig. 1, Fig. 1 is the synoptic diagram of a LED display device 100 in the prior art.LED display device 100 comprises one direct current/d-c transformer (DC/DC converter), 12, one pulse width modulation (pulse width modulation, PWM) controller 14, a feedback loop 16, and a light source 18.DC-DC transformer 12 comprises a gold medal oxygen half, and (metal-oxide-semiconductor, MOS) switch can be with an input voltage V
iChange an output voltage V
O1With driving light source 18.Light source 18 comprises the light emitting diode D of 2n serial connection
1～D
2n, the forward forward voltage of each light emitting diode is V
F, that is the cross-pressure V on the light source 18
LED1Be (2n) * V
F, and the electric current of the light source 18 of flowing through is by I
LED1Represent.Feedback loop 16 comprises a resistance R
FB1But, detecting current I
LED1Value and a corresponding feedback voltage V is provided according to this
FB1According to feedback voltage V
FB1Value, PWM controller 14 can produce a corresponding control signal to adjust the conduction ratio of MOS switch in the DC-DC transformer 12, therefore can see through the adjustment output voltage V
O1Come steady current I
LED1Value, make light source 18 that uniform luminance can be provided.
In the framework of Fig. 1, the output voltage V of DC-DC transformer 12
O1Cross-pressure V for light source 18
LED1With feedback voltage V
FB1Totalling, that is V
O1=V
LED1+ V
FB1In general, V
LED1＞＞V
FB1, so V
O1≈ V
LED1When a series connection number 2n of light emitting diode in the light source 18 increases, cross-pressure V
LED1Value can become greatly and the output voltage V of DC-DC transformer 12
O1Also can so can cause high voltage stress along with increase.Therefore, the LED display device 100 of prior art has safety to recognize the doubt of row, and needs to use high withstand voltage assembly and integrated circuit, and production cost is high.
Please refer to Fig. 2, Fig. 2 is the synoptic diagram of a LED display device 200 in the prior art.LED display device 200 comprises one direct current/d-c transformer 22, a PWM controller 24, a feedback loop 26, and a light source 28.DC-DC transformer 22 comprises a MOS switch, can be with an input voltage V
iChange an output voltage V
O2With driving light source 28.Light source 28 comprises the light emitting diode string L1 and the L2 of two groups of parallel connections, and light emitting diode string L1 comprises the light emitting diode D of n serial connection
11～D
1n, and light emitting diode string L2 comprises the light emitting diode D of n serial connection
21～D
2nThe forward forward voltage of each light emitting diode is V
F, that is the cross-pressure V of light source 28
LED2Be n*V
FThe electric current of the light emitting diode string of flowing through L1 and L2 is respectively by I
L1And I
L2Represent, and drive current I
LED2Be I
L1And I
L2Totalling.Feedback loop 26 comprises a resistance R
FB2, can detect drive current I
LED2Value and a corresponding feedback voltage V is provided according to this
FB2According to feedback voltage V
FB2Value, PWM controller 24 can produce a corresponding control signal to adjust the conduction ratio of MOS switch in the DC-DC transformer 22, therefore can see through the adjustment output voltage V
O2Come the stabilized driving electric current I
LED2Value, make light source 18 that uniform luminance can be provided.
In the framework of Fig. 2, the output voltage V of DC-DC transformer 22
O2Cross-pressure V for light source 28
LED2With feedback voltage V
FB2Totalling, that is V
O2=V
LED2+ V
FB2In general, V
LED2＞V
FB2, so V
O2≈ V
LED2Because the light source 28 of LED display device 200 adopts framework in parallel, is all under the situation of 2n the output voltage V of DC-DC transformer 22 in the light emitting diode total quantity
O2Value only be the output voltage V of DC-DC transformer 12
O1Half of value, therefore can reduce voltage stress.Yet the LED display device 200 of prior art can't be guaranteed electric current I
L1And I
L2The identical value of tool, so light emitting diode string L1 and L2 have the problem of brightness disproportionation, influences display quality.
The utility model content
The utility model provides a kind of flow equalizing circuit, is used for balance plural groups electric current, and it comprises a plurality of resistance, a plurality of switch module, and an operational amplifier.Each switch module comprises one first end, is used for receiving a corresponding electric current in this plural groups electric current; One second end is coupled to a corresponding resistance in these a plurality of resistance; An and control end.This operational amplifier comprises a positive input terminal, is used for receiving one first electric current in this plural groups electric current; One negative input end is used for receiving one second electric current in this plural groups electric current; And an output terminal, be coupled to the control end of these a plurality of switch modules.
The utility model provides a kind of display device that can promote the optics uniformity coefficient in addition, and it comprises a light source, and it comprises the light-emitting device of plural groups parallel connection; And a flow equalizing circuit, be used for the electric current of equiulbrium flow through this plural groups light-emitting device.This flow equalizing circuit comprises a plurality of resistance, a plurality of switch module and an operational amplifier.Each switch module comprises one first end, is coupled to a corresponding light-emitting device in this plural groups light-emitting device; One second end is coupled to a corresponding resistance in these a plurality of resistance; An and control end.This operational amplifier comprises a positive input terminal, is coupled to one first light-emitting device in this plural groups light-emitting device; One negative input end is coupled to one second light-emitting device in this plural groups light-emitting device; And an output terminal, be coupled to the control end of these a plurality of switch modules.
Description of drawings
Fig. 1 is the synoptic diagram of a LED display device in the prior art.
Fig. 2 is the synoptic diagram of another LED display device in the prior art.
Fig. 3 is the synoptic diagram of a LED display device in the utility model.
Fig. 4 is the synoptic diagram of flow equalizing circuit in the utility model.
Embodiment
In the middle of instructions and aforesaid claim scope, used some vocabulary to censure specific assembly.The person with usual knowledge in their respective areas should understand, and hardware manufacturer may be called same assembly with different nouns.This instructions and aforesaid claim scope are not used as distinguishing the mode of assembly with the difference of title, but the criterion that is used as distinguishing with the difference of assembly on function.Be to be an open term mentioned " comprising " in the middle of instructions and the aforesaid claim in the whole text, so should be construed to " comprise but be not limited to ".In addition, " coupling " speech is to comprise any indirect means that are electrically connected that directly reach at this.Therefore, be coupled to one second device, then represent this first device can directly be electrically connected in this second device, or be electrically connected to this second device indirectly through other device or connection means if describe one first device in the literary composition.
Please refer to Fig. 3, Fig. 3 is the synoptic diagram of a LED display device 300 in the utility model.LED display device 300 comprises one direct current/d-c transformer 32, a PWM controller 34, a feedback loop 36, a light source 38, and a flow equalizing circuit 40.DC-DC transformer 32 comprises a MOS switch, can be with an input voltage V
iChange an output voltage V
O3With driving light source 38.Light source 38 comprises m group LED string L1～Lm in parallel, and each light emitting diode string respectively comprises the light emitting diode of n serial connection, and the m*n that light source 38 comprises an altogether light emitting diode is respectively by D
11～D
MnRepresent.The forward forward voltage of each light emitting diode is V
F, the electric current of the light emitting diode string of flowing through L1～Lm is respectively by I
L1～I
LmRepresent, that is drive current I
LED3Be I
L11～I
LmTotalling.Flow equalizing circuit 40 possesses flow equalizing function, can be with electric current I
L1～I
LmValue all maintain a fixed value (I
LED3/ m).Feedback loop 36 comprises a resistance R
FB3, can detect drive current I
LED3Value and a corresponding feedback voltage V is provided according to this
FB3According to feedback voltage V
FB3Value, PWM controller 34 can produce a corresponding control signal to adjust the conduction ratio of MOS switch in the DC-DC transformer 32, therefore can see through the adjustment output voltage V
O3Come the stabilized driving electric current I
LED3Value, make light source 38 that uniform luminance can be provided.
Please refer to Fig. 4, Fig. 4 is the synoptic diagram of flow equalizing circuit 40 in the utility model.Flow equalizing circuit 40 comprises a plurality of switch Q1～Qm, a plurality of resistance R 1～Rm, and an operational amplifier OP.Switch Q1～Qm can be the two-carrier junction transistor (bipolar junction transistor, BJT), its collection utmost point (collector) is respectively coupled to LED string L1～Lm, emitter-base bandgap grading (emitter) is respectively coupled to resistance R
1～R
m, and base stage (base) all is coupled to the output terminal of operational amplifier OP.Simultaneously, the negative input end of operational amplifier OP is used for received current I
L1, the positive input terminal of operational amplifier OP then is used for received current I
Lm
In the framework of Fig. 4, the base-emitter voltage of switch Q1～Qm is respectively by V
BE1～V
BEmRepresent that the cross-pressure on resistance R 1～Rm is respectively by V
R1～V
RmRepresent, so the voltage V of the output terminal of operational amplifier OP
OUTCan represent by following formula:
V
OUT＝V
BE1+V
R1＝V
BE2+V
R2＝...＝V
BEm+V
Rm
In manufacture process, the characteristic of switch Q1～Qm is difference to some extent, so base-emitter voltage V
BE1～V
BEmAlso can be different.Cross-pressure V on resistance R 1～Rm
R1～V
RmAlso can react base-emitter voltage V respectively
BE1～V
BemDifference, make electric current I
L1～I
LmValue may not can mate fully.Therefore, the utility model uses operational amplifier OP to come offset current difference, makes electric current I
L1～I
LmValue probably maintain a fixed value (I
L1≈ I
L2≈ ... ≈ I
Lm≈ I
LED3/ m), and then reach the purpose of current balance type.
The above only is preferred embodiment of the present utility model, and all equalizations of being done according to the utility model claim scope change and modify, and all should belong to covering scope of the present utility model.
Claims (10)
1. flow equalizing circuit is used for balance plural groups electric current, it is characterized in that, comprises:
A plurality of resistance;
A plurality of switch modules, each switch module comprises:
One first end is used for receiving a corresponding electric current in this plural groups electric current;
One second end is coupled to a corresponding resistance in these a plurality of resistance; And
One control end; And
One operational amplifier, it comprises:
One positive input terminal is used for receiving one first electric current in this plural groups electric current;
One negative input end is used for receiving one second electric current in this plural groups electric current; And
One output terminal is coupled to the control end of these a plurality of switch modules.
2. flow equalizing circuit as claimed in claim 1 is characterized in that, each switch module is to comprise a two-carrier junction transistor.
3. flow equalizing circuit as claimed in claim 2, it is characterized in that this two-carrier junction transistor is to be a NPN transistor, this first end is the collection utmost point for this NPN transistor, this second end is the emitter-base bandgap grading for this NPN transistor, and this control end is the base stage for this NPN transistor.
4. the display device that can promote the optics uniformity coefficient is characterized in that, comprises:
One light source, it comprises the light-emitting device of plural groups parallel connection;
One flow equalizing circuit is used for equiulbrium flow through the electric current of this plural groups light-emitting device, and it comprises:
A plurality of resistance;
A plurality of switch modules, each switch module comprises:
One first end is coupled to a corresponding light-emitting device in this plural groups light-emitting device;
One second end is coupled to a corresponding resistance in these a plurality of resistance; And
One control end; And
One operational amplifier, it comprises:
One positive input terminal is coupled to one first light-emitting device in this plural groups light-emitting device;
One negative input end is coupled to one second light-emitting device in this plural groups light-emitting device; And
One output terminal is coupled to the control end of these a plurality of switch modules.
5. display device as claimed in claim 4 is characterized in that, each switch module is to comprise a two-carrier junction transistor.
6. display device as claimed in claim 5, it is characterized in that this two-carrier junction transistor is to be a NPN transistor, this first end is the collection utmost point for this NPN transistor, this second end is the emitter-base bandgap grading for this NPN transistor, and this control end is the base stage for this NPN transistor.
7. display device as claimed in claim 4 is characterized in that each light-emitting device comprises the light emitting diode of a plurality of serial connections.
8. display device as claimed in claim 4 is characterized in that, also comprises:
One feedback loop is used for providing a feedback voltage according to the total current of this plural groups light-emitting device of flowing through;
One control circuit is used for producing a corresponding control signal according to this feedback voltage; And
One transformer is used for receiving an input voltage, changes this input voltage according to this control signal, and exports a corresponding output voltage to drive this light source.
9. display device as claimed in claim 8 is characterized in that, this feedback loop is to comprise a resistance.
10. display device as claimed in claim 8 is characterized in that, this control circuit is to comprise a pulse width modulation circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009201615794U CN201489798U (en) | 2009-07-30 | 2009-07-30 | Display device capable of improving optical uniformity and current sharing circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009201615794U CN201489798U (en) | 2009-07-30 | 2009-07-30 | Display device capable of improving optical uniformity and current sharing circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201489798U true CN201489798U (en) | 2010-05-26 |
Family
ID=42428668
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009201615794U Expired - Fee Related CN201489798U (en) | 2009-07-30 | 2009-07-30 | Display device capable of improving optical uniformity and current sharing circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201489798U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104200776A (en) * | 2014-09-25 | 2014-12-10 | 武汉精测电子技术股份有限公司 | Pixel driving circuit and driving method for improving Mura defect of OLED panel |
| CN108834265A (en) * | 2018-08-22 | 2018-11-16 | 惠州莫思特智照科技有限公司 | Dimmable lighting device and light adjusting circuit |
-
2009
- 2009-07-30 CN CN2009201615794U patent/CN201489798U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104200776A (en) * | 2014-09-25 | 2014-12-10 | 武汉精测电子技术股份有限公司 | Pixel driving circuit and driving method for improving Mura defect of OLED panel |
| CN104200776B (en) * | 2014-09-25 | 2017-02-15 | 武汉精测电子技术股份有限公司 | Pixel driving circuit and driving method for improving Mura defect of OLED panel |
| CN108834265A (en) * | 2018-08-22 | 2018-11-16 | 惠州莫思特智照科技有限公司 | Dimmable lighting device and light adjusting circuit |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20100526 Termination date: 20170730 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |