CN102610199A - Light-emitting diode (LED) backlight driving circuit - Google Patents
Light-emitting diode (LED) backlight driving circuit Download PDFInfo
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- CN102610199A CN102610199A CN2012100679348A CN201210067934A CN102610199A CN 102610199 A CN102610199 A CN 102610199A CN 2012100679348 A CN2012100679348 A CN 2012100679348A CN 201210067934 A CN201210067934 A CN 201210067934A CN 102610199 A CN102610199 A CN 102610199A
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Abstract
The invention aims to provide a light-emitting diode (LED) backlight driving circuit, which comprises a stabilized power supply and a constant current driving circuit. The constant current driving circuit comprises a plurality of driving branch circuits which are the same. The first driving branch circuit comprises a first driving triode. The input end of a series-wound LED set is connected with the anode of the stabilized power supply, and the output end of the series-wound LED set is connected with the collector of the first driving triode. The emitter of the first driving triode is grounded through an emitter resistor of the first driving branch circuit, and the base of the first driving triode is connected with base bias voltage through a base resistor. The LED backlight driving circuit also comprises a constant current control circuit. The constant current control circuit comprises a reference voltage source which is connected to the two ends of an emitter resistor of the first driving branch circuit. The circuit disclosed by the invention is simple, easy to control and low in cost.
Description
Technical field
The present invention relates to the driving power field of the backlight circuit of LED screen, the stabilized voltage supply that particularly a kind of constant-current circuit, this constant-current circuit utilize the LLC voltage-stabilized power supply circuit to export is accurately controlled the electric current of each LED that flows through in the LED screen.
Background technology
At present, the backlight drive circuit of LED screen generally comprises a LLC voltage-stabilized power supply circuit and a constant-current drive circuit, and the LLC voltage-stabilized power supply circuit can change output voltage through the wherein different transformer turn ratio of design.A kind of linear constant-current driving that is widely used at present produces the LED lamp that continuous current drives one group of quantity with the DC voltage of the LLC voltage-stabilized power supply circuit of front output after through the DC/DC booster circuit; This constant-current drive circuit has a BOOST DC/DC booster circuit, and the boost in voltage that the LLC voltage-stabilized power supply circuit is exported arrives 100V, and the voltage of this 100V is added on the circuit by 33 LED polyphones; The driving LED lamp; In order to guarantee the effect of current stabilization, this constant-current drive circuit also carries out constant flow regulation to the circuit that the LED of every group of 33 polyphones forms, and such circuit constant current source is relatively good; But circuit more complicated, cost are also high.
Summary of the invention
Present invention is directed to the high deficiency of complicated circuit cost in the constant-current drive circuit in the present LED screen backlight drive circuit, a kind of LED-backlit driving circuit is provided.
The technical scheme that the present invention adopts in order to realize goal of the invention is: a kind of LED-backlit driving circuit; Comprise stabilized voltage supply and constant-current drive circuit; Described constant-current drive circuit comprises that at least one drives branch road, and all driving branch road parallel connections insert described stabilized voltage supply; Any driving branch road drives the LED polyphone group of being contacted by two LED at least;
Comprise that first drives branch road in the described at least one driving branch road; Described first drives branch road comprises that first drives triode; The described positive pole of stabilized voltage supply of input termination of described LED polyphone group; The output termination of described LED polyphone group described first drives the collector of triode, and the emitter of the described first driving triode drives branch road emitter resistance ground connection through first, and the base stage of the described first driving triode connects the inclined to one side threshold voltage of base stage through base resistance;
Driving triode, the emitter resistance of all driving branch road tool identical parameters, all driving transistor bases link together, and drive the LED polyphone group of identical parameters;
Also comprise constant-current control circuit, described constant-current control circuit comprises reference voltage source, and described reference voltage source joins described first and drives branch road emitter resistance two ends;
The output voltage of described stabilized voltage supply is adjusted into LED WV sums all in the described LED polyphone group and adds that described reference voltage adds LED voltage deviation amount.
Further, in the above-mentioned LED-backlit driving circuit: in described constant-current control circuit, also comprise control capacittance, described control capacittance two ends connect the emitter that described reference voltage source positive pole and described first drives triode respectively.
Further; In the above-mentioned LED-backlit driving circuit: also comprise second base resistance; Described second base resistance is connected in base resistance and drives between the base stage of triode, and the positive pole of described constant-current control circuit links to each other with the second base resistance tie point with described base resistance.
Further, in the above-mentioned LED-backlit driving circuit: described stabilized voltage supply is the LLC circuit.
LED-backlit driving circuit of the present invention is simple and easy to control, has reduced cost.
Below will combine accompanying drawing and embodiment, the present invention will be carried out comparatively detailed explanation.
Description of drawings
Fig. 1 is a constant-current control circuit of the present invention.
Embodiment
Embodiment 1; As shown in Figure 1; Present embodiment is the LLC topology that drives of a kind of LED-backlit that is applicable to the big screen LED TV and the uniting and adjustment circuit of linear constant current, the LED of this drives n*m array, and a total m bar drives branch road; Every drives a driving of route triode like Q1, Q2, Qm driving among the figure, and a branch road has n LED polyphone.These triodes have identical electrical quantity, and whole base stages is received on the identical base circuit R1, in order to join with constant-current control circuit, also are provided with the second base resistance R2 and R1 polyphone, are connected between the inclined to one side threshold voltage 12V of base stage and base stage.The driving triode of each bar branch road connects into emitter follower circuit, and it is identical that emitter resistance is illustrated in figure 1 as R3, R4, R2+m resistance.Specifically as shown in Figure 1:
Following map 1 is introduced the principle of work of present embodiment.Introduce first branch road earlier, the driving triode of this branch road is the first driving triode Q1, and power supply adopts the stabilized voltage supply of LLC circuit; LED polyphone group, Q1 and R3 resistance inflow place that the output DC OUT voltage of the power supply of voltage stabilizing is formed through many n LED D11, D12, D1n lamp, wherein R3 has two effects, the one, emitter resistance; Simultaneously be used for doing detection resistance again, the emitter resistance size of other branch road is identical with it, but is not used for doing detection resistance; Only be used for mating; Make other branch road identical with first branch road, model is that the high-precision reference voltage source U1 of TL431 detects through this detection resistance R 3, detects resistive voltage and reaches reference voltage like (1.25V or 2.5V etc.) this control circuit control first control triode Q1; The control of realization closed loop current, other branch road principle is identical therewith.In order to reach Optimal Control, make LLC circuit stabilized voltage supply and back level LED linear constant current circuit coupling, need satisfy several conditions: (1) LED constant current value is: U1 reference voltage V REF/R3; Because Q1, Q2, Q3 base stage connect; Then voltage is consistent, and triode connects and is emitter following, and it is identical with R3 to get resistances such as R4, Rm+2; Then Q2, Qm constant current are the same with Q1, reach the consistent constant current requirement of multichannel; (2) LLC circuit stabilized voltage supply DCOUT voltage is set at VLED* serial number+reference voltage value+LED voltage deviation amount; Here LED voltage deviation amount is caused by the LED characteristic; Adopt same batch LED, LED voltage deviation amount is a constant, for all outlets; All be the number that to grasp, can adjust the voltage that is fit to the use of this driving circuit through the primary and secondary coil of regulating the LLC circuit.(3) VCE voltages such as Q1, Q2, Q3 are limited in the suitable voltage scope, and promptly Vce*Ic is lower than the triode dissipated power, is usually less than 1W.
In the present embodiment, constant-current control circuit comprises that reference voltage source U1 is high-precision reference voltage source TL431, but is not limited to TL431, and reference voltage source U1 only joins first and drives branch road emitter resistance R3 two ends; Because the base stage in all outlets is connected; And have identical driving triode and identical grounded emitter resistance, and drive equal number and identical LED, therefore; Must there be identical steady current in other outlet with first branch road; Therefore on other branch road, do not need constant-current control circuit, comprise also in the constant-current control circuit that control capacittance C1, control capacittance two ends connect the emitter that described reference voltage source U1 positive pole and first drives triode Q1 respectively.In addition, also comprise the second base resistance R2, the second base resistance R2 is connected in base resistance R1 and drives between the base stage of triode, and the positive pole of reference voltage source U1 links to each other with the second base resistance R2 tie point with base resistance R1 in the constant-current control circuit.
Through Experiment of Electrical Circuits; The present embodiment circuit is through the different transformer turn ratioes in the design LLC circuit; Change output voltage, make it with Fig. 1 in Circuit Matching, can save the more BOOST DC/DC of present use; To big screen LED TV realization high-accuracy and constant backlight current control, be that resistances such as R3, R4, Rm+2 are selected for use and reached high-accuracy and constant current control, high-level efficiency and effect cheaply through control LLC series resonant converter output voltage.
Present embodiment has following effect:
(1) be limited to LED-backlit driving power in the LED TV, adopt the LLC series resonant converter, the LLC output voltage need require the design output voltage according to the back linear constant current of level simultaneously;
(2) base stages such as Q1, Q2, Qm connect, and the Q1 emitter connects employing resistance, and resistance satisfies the VREF/LED constant current value, and U1 adopts high-precision reference voltage source, like TL431, but is not limited to TL431, like similar principles circuit such as other operational amplifiers;
(3) the DC OUT voltage setting value of the stabilized voltage supply of LLC output is VLED* serial number+reference voltage value+LED voltage deviation amount (is set at Vce*Ic and is lower than the triode dissipated power, be usually less than 1W).
Claims (5)
1. a LED-backlit driving circuit comprises stabilized voltage supply and constant-current drive circuit, and described constant-current drive circuit comprises that at least one drives branch road, and all driving branch road parallel connections insert described stabilized voltage supply; Any driving branch road drives the LED polyphone group of being contacted by two LED at least; It is characterized in that:
Comprise that first drives branch road in the described at least one driving branch road; Described first drives branch road comprises that first drives triode (Q1); The described positive pole of stabilized voltage supply of input termination of described LED polyphone group; The output termination of described LED polyphone group described first drives the collector of triode (Q1); The emitter of the described first driving triode (Q1) drives branch road emitter resistance (R3) ground connection through first, and the base stage of the described first driving triode (Q1) connects the inclined to one side threshold voltage of base stage through base resistance (R1);
Driving triode, the emitter resistance of all driving branch road tool identical parameters, all driving transistor bases link together, and drive the LED polyphone group of identical parameters;
Also comprise constant-current control circuit, described constant-current control circuit comprises reference voltage source (U1), and described reference voltage source (U1) joins described first and drives branch road emitter resistance (R3) two ends;
The output voltage of described stabilized voltage supply is adjusted into LED WV sums all in the described LED polyphone group and adds that described reference voltage adds LED voltage deviation amount.
2. LED-backlit driving circuit according to claim 1; It is characterized in that: in described constant-current control circuit, also comprise control capacittance (C1), described control capacittance two ends connect the emitter that described reference voltage source (U1) positive pole and described first drives triode respectively.
3. LED-backlit driving circuit according to claim 2; It is characterized in that: also comprise second base resistance (R2); Described second base resistance (R2) is connected in base resistance (R1) and drives between the base stage of triode, and the positive pole of described constant-current control circuit links to each other with second base resistance (R2) tie point with described base resistance (R1).
4. according to arbitrary described LED-backlit driving circuit in the claim 1 to 3, it is characterized in that: described stabilized voltage supply is the LLC circuit.
5. according to arbitrary described LED-backlit driving circuit in the claim 1 to 3, it is characterized in that: described reference voltage source (U1) is the high-precision reference voltage source of TL431 for model.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012100679348A CN102610199A (en) | 2012-03-15 | 2012-03-15 | Light-emitting diode (LED) backlight driving circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2012100679348A CN102610199A (en) | 2012-03-15 | 2012-03-15 | Light-emitting diode (LED) backlight driving circuit |
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| CN102610199A true CN102610199A (en) | 2012-07-25 |
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| CN2012100679348A Pending CN102610199A (en) | 2012-03-15 | 2012-03-15 | Light-emitting diode (LED) backlight driving circuit |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102802307A (en) * | 2012-08-02 | 2012-11-28 | 常州星宇车灯股份有限公司 | Intelligent topology protection system of LED (Light-Emitting Diode) car lamp |
| CN103269541A (en) * | 2013-05-08 | 2013-08-28 | 珠海雷特电子科技有限公司 | LED constant-current controller integrating three types of output current specifications |
| CN103680414A (en) * | 2012-09-13 | 2014-03-26 | 上海江森自控汽车电子有限公司 | LCD backlight constant current drive circuit |
| CN103813576A (en) * | 2012-11-15 | 2014-05-21 | 欧普照明股份有限公司 | Multipath LED (light-emitting diode) driving circuit |
| WO2014190579A1 (en) * | 2013-05-28 | 2014-12-04 | 深圳市华星光电技术有限公司 | Led backlight drive circuit, liquid crystal display device and drive method |
| CN104219843A (en) * | 2014-08-29 | 2014-12-17 | 深圳市奋勇光电有限公司 | Multi-output circuit with superposed constant-current control architecture |
| US9018857B2 (en) | 2013-05-28 | 2015-04-28 | Shenzhen China Star Optoelectronics Technology Co., Ltd | LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit |
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| JP2007281417A (en) * | 2006-04-04 | 2007-10-25 | Lg Phillips Lcd Co Ltd | Light-emitting diode driving device and liquid crystal display using the same |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102802307A (en) * | 2012-08-02 | 2012-11-28 | 常州星宇车灯股份有限公司 | Intelligent topology protection system of LED (Light-Emitting Diode) car lamp |
| CN103680414A (en) * | 2012-09-13 | 2014-03-26 | 上海江森自控汽车电子有限公司 | LCD backlight constant current drive circuit |
| CN103680414B (en) * | 2012-09-13 | 2016-01-06 | 上海伟世通汽车电子系统有限公司 | A kind of LCD backlight constant current drive circuit |
| CN103813576A (en) * | 2012-11-15 | 2014-05-21 | 欧普照明股份有限公司 | Multipath LED (light-emitting diode) driving circuit |
| CN103813576B (en) * | 2012-11-15 | 2016-12-21 | 欧普照明股份有限公司 | A kind of multipath LED drive circuit |
| CN103269541A (en) * | 2013-05-08 | 2013-08-28 | 珠海雷特电子科技有限公司 | LED constant-current controller integrating three types of output current specifications |
| CN103269541B (en) * | 2013-05-08 | 2015-10-28 | 珠海雷特电子科技有限公司 | A kind of LED constant current controller of integrated three kinds of output current specifications |
| WO2014190579A1 (en) * | 2013-05-28 | 2014-12-04 | 深圳市华星光电技术有限公司 | Led backlight drive circuit, liquid crystal display device and drive method |
| US9018857B2 (en) | 2013-05-28 | 2015-04-28 | Shenzhen China Star Optoelectronics Technology Co., Ltd | LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit |
| CN104219843A (en) * | 2014-08-29 | 2014-12-17 | 深圳市奋勇光电有限公司 | Multi-output circuit with superposed constant-current control architecture |
| CN104219843B (en) * | 2014-08-29 | 2016-11-16 | 深圳市奋勇光电有限公司 | The multiplex output circuit of superposition current constant control framework |
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Application publication date: 20120725 |