CN100383837C - Driving circuit of light-emitting diode - Google Patents
Driving circuit of light-emitting diode Download PDFInfo
- Publication number
- CN100383837C CN100383837C CNB2004100911792A CN200410091179A CN100383837C CN 100383837 C CN100383837 C CN 100383837C CN B2004100911792 A CNB2004100911792 A CN B2004100911792A CN 200410091179 A CN200410091179 A CN 200410091179A CN 100383837 C CN100383837 C CN 100383837C
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- resistance
- voltage
- led
- power supply
- changeover device
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Abstract
The present invention relates to a driving circuit for light emitting diodes (LED), which comprises a power supply converter, an LED load, a detection resistor, a divider circuit, an input voltage source, reference voltage, measured voltage and correction voltage, wherein the power supply converter outputs current to the LED load according to the difference value between the measured voltage and the correction voltage, and the current flows along the LED load and the detection resistor; the divider circuit is electrically connected to the LED load, the detection resistor and the third end of the power supply converter, wherein the measured voltage is taken from the divider circuit.
Description
Technical field
The invention relates to a kind of light emitting diode (LED) driving circuit, and particularly relevant for a kind of invention of LED-backlit module drive circuit.
Background technology
High-brightness LED (Light Emitting Diode, light emitting diode) is little with its volume, the life-span is long and advantage such as environmental protection, become the main employing of LCD (Liquid Crystal Display, liquid crystal indicator) backlight module institute light source.3～4 of the needs even backlight of a color/graphics LCD or more White LED, and, in backlight module, must use stable electric current (constant current source) to come driving LED for stabilized illumination.
The size of current of this constant current source is generally 15mA～20mA.The brightness of LED depends on the electric current of its forward, so a plurality of LED polyphone uses, the electric current that can guarantee to flow through each LED is all identical, makes LCD obtain desirable display effect.Present known led drive circuit comprises power supply changeover device, LED load, detects resistance, input voltage source, reference voltage V
Ref, measure voltage V
dAnd output voltage.
Reference voltage V
RefBe the fixed voltage value that provides by the outside, and measure voltage V
dThe electric current I of exporting for power supply changeover device
LEDThe voltage drop that when flowing through detection resistance, is caused.And power supply changeover device is promptly controlled I according to the difference of this two voltage
LEDSize, and then the brightness of control LED load.
Wherein, the first input end of power supply changeover device is electrically connected on input voltage source, and second input end is electrically connected on reference voltage V
RefThe output terminal of power supply changeover device provides output voltage and is electrically connected on the input end of LED load.An end that detects resistance is electrically connected on the output terminal of LED load, and the other end then is electrically connected on earth terminal.Wherein, detect the end points that resistance is connected with the LED load and be mensuration voltage V
dMeasurement point, wherein this measures voltage Vd and is equal to the voltage that detects on the resistance, and this measures voltage Vd and feeds back to power supply changeover device to become loop, and power supply changeover device is regulated output voltage values according to reference voltage, makes final mensuration voltage Vd be equal to reference voltage Vref and makes the LED load obtain stable current source.
In this known technology, as the forward voltage drop sum (V of output voltage greater than the LED load
LED1) time, the LED load obtains drive current I
LEDAnd luminous, shinny, this size of current I
LED=(V
Out-V
LED)/Rsense.Power supply changeover device is according to reference voltage V
RefMensuration voltage V with feedback
dDifference between two voltages decides its output current value, controls the brightness that the LED load can produce in view of the above accurately.
Yet, though this kind control method can be controlled the brightness of LED load accurately, but because the power that input voltage source provided has most is to consume detecting on the resistance, thereby makes the resultant relatively power of LED load obviously tail off, and causes the usefulness of this kind led drive circuit very low.
Summary of the invention
Purpose of the present invention just provides a kind of led drive circuit, to reduce power consumption, improves service efficiency.
The present invention proposes a kind of led drive circuit, comprises the LED load, detects resistance, bleeder circuit and power supply changeover device.
Wherein, the output terminal that first end that detects resistance is electrically connected on the LED load is with the flow through output current of LED load of reception, and this second end that detects resistance is electrically connected on earth terminal.Bleeder circuit is electrically connected on first end and the correction voltage that detect resistance respectively.
Power supply changeover device, first end of this power supply changeover device is electrically connected on the input power supply, and second termination is received reference voltage signal, the mensuration voltage signal that the 3rd termination contracture volt circuit is exported.This power supply changeover device comes the driving LED load according to reference voltage signal and the difference of measuring voltage signal to export stable electric current.
The present invention measures the voltage compensation loop because of adopting, and therefore can reduce to detect the resistance value of the required use of resistance, to reach power saving and the purpose of raising the efficiency.
State with other purpose, feature and advantage and can become apparent on the present invention for allowing, preferred embodiment cited below particularly, and conjunction with figs. are described in detail below.
Description of drawings
Fig. 1 is a kind of led drive circuit of a preferred embodiment of the present invention.
Fig. 2 is a kind of led drive circuit of another preferred embodiment of the present invention.
The main element description of symbols
The 100:LED driving circuit
The 200:LED driving circuit
110,202: power supply changeover device
106,204:LED load
108,206: detect resistance
102,212: input voltage source
150,214: reference voltage V
Ref
160,218: measure voltage V
d
104,220: output voltage
134,208: the first resistance
132,210: the second resistance
216: calibration voltage V
Reg
140: correction voltage V
Reg
112: pulsed modulation formula electric pressure converter
114: comparer
116: buffer memory
118: transistor switch
120: the lifting/voltage reducing circuit
130: bleeder circuit
Embodiment
Please refer to Fig. 1, Fig. 1 is the led drive circuit of a preferred embodiment of the present invention.This led drive circuit 100 comprises input voltage source 102, output voltage 104, LED (LightEmitting Diode, light emitting diode) load 106, detects resistance 108, power supply changeover device 110, bleeder circuit 130, correction voltage V
Reg140, reference voltage V
Ref150 and measure voltage V
d160.
Wherein, power supply changeover device 110 also comprises pulsed modulation formula electric pressure converter 112, comparer 114, buffer memory 116, transistor switch 118 and lifting/voltage reducing circuit 120.Bleeder circuit 130 also comprises first resistance 134 and second resistance 132, and wherein pulsed modulation formula electric pressure converter 112 can be selected the chip Max1856 of Maxim company production for use.
Wherein, the first input end of pulsed modulation formula electric pressure converter 112 is electrically connected on the output terminal that input voltage source 102, the second input ends are electrically connected on comparer 114, and its output terminal then is electrically connected on the input end of buffer memory 116.The input end of transistor switch 118 is electrically connected on the output terminal of buffer memory 116, its output terminal then is electrically connected to the input end of lifting/voltage reducing circuit 120, the output terminal of lifting/voltage reducing circuit 120 is the output terminal of power supply changeover device 110, is electrically connected on the input end of LED load 106.
The input end of power supply changeover device 110 is electrically connected on input voltage source 102, and to receive voltage and to be impulse form via the pulsed modulation formula electric pressure converter 112 of inside with voltage transitions, second input end is electrically connected on reference voltage V
Ref150, the three input ends are electrically connected on the output terminal of bleeder circuit 130, measure voltage V in order to receive
d160.
The comparer 114 of power supply changeover device 110 inside will be measured voltage V
d160 with reference voltage V
Ref150 compare after, export one group and control signal to pulsed modulation formula electric pressure converter 112 with regulation voltage pulsewidth or frequency.
The input end of buffer memory 116 is electrically connected on the output terminal of pulsed modulation formula electric pressure converter 112, with the transmission modulation signal, the input end of transistor switch 118 is electrically connected on the output terminal of buffer memory 116, the voltage of controlling booster circuit 120 with the voltage pulsewidth that receives the modulation back improves ratio, and produces the input end of output voltage 104 to LED loads 106.The output terminal of LED load 106 then is electrically connected on the input end and first end that detects resistance 108 of bleeder circuit 130.
Second end that bleeder circuit 130 comprises first resistance 134 and second resistance, 132, the first resistance 134 is electrically connected on correction voltage V
Reg140, its first end is electrically connected on first end of second resistance 132 and the 3rd input end of power supply changeover device 110.Second end of second resistance 132 is electrically connected on the output terminal and first end that detects resistance 108 of LED load 106, and second end of detection resistance 108 is electrically connected on earth terminal.
Detailed in the present embodiment principle of work is as described below, and LED load 106 is by the circuit that several LED formed, and correction voltage V
Reg140 must satisfy the condition of Vreg＞Vref, and I
LED1Be the load current of stream through LED load 106.
When output voltage 104 during greater than the forward voltage drop sum of LED load 106, power supply changeover device 110 output current I
LED1Come driving LED load 106 to make it luminous, shinny.And this output current size is that power supply changeover device 110 is according to reference voltage V
Ref150 with the mensuration voltage V of feedback
dDifference between 160, two voltages decides its output current value I
LED1Size, when measuring voltage V
d160 are equal to reference voltage V
Ref150 o'clock, then LED load 106 can obtain the electric current I stablized
LED1, therefore can obtain relative steady current, to control the brightness of LED load 106 accurately in order to change reference voltage.
Wherein, reference voltage V
Ref150 are provided by external input voltage, are about 1.24V, and measure voltage V
d160 is the terminal voltage value that detects the resistance two ends in known technology.But, cause owing to the resistance value that detects resistance is excessive to consume too many power, so that make suitable low of whole known driving circuit efficient.
So, in the present embodiment, utilize the bleeder circuit of forming by first resistance 134 and second resistance 132 and cooperate correction voltage V
Reg140 and form to measure voltage compensating circuit, compensate and measure voltage V
d160 magnitude of voltage.
Wherein, first resistance 134 is that R1, second resistance 132 are that R2 and detection resistance 108 are R
SE SE, its relational expression is as shown in following:
(V
reg-V
ref)/R
1＝(V
ref-I
LED1*R
SE\SE)/R
2
Because first resistance 134, second resistance 132 all are the resistance of tens of K ohms,, measure in the voltage compensation loop correction voltage V at this so from following formula, can know
Reg140 most voltages all drop on first resistance 134 and second resistance 132, make to measure voltage V
d160 are no longer just judged by the voltage that detects resistance 108 two ends, provide this to measure voltage V and be transformed into by second resistance 132 and the terminal voltage sum that detects resistance 108
d160.
By such design, can be so that detection resistance 108 that originally may tens of K ohms, owing to added first resistance 134, second resistance 132 and calibration voltage V
RegAfter 140, can be reduced to tens of ohm resistance, also reduced simultaneously and detected the voltage drop that resistance 108 is caused, such benefit is that the power that input voltage source 102 is exported almost can all consume in LED load 106, integral body has improved the efficient of input voltage source 102, and has reached less electricity consumption.
What deserves to be mentioned is that the bleeder circuit in the above-mentioned explanation is not limited only to use R1, R2 resistance to form, if any circuit meet following condition all applicable it:
(V
reg-V
ref)/R
X＝(V
ref-I
LED1*R
SE\CE)/R
Y
Wherein voltage V is measured in the Rx representative
d160 ends are to correction voltage V
RegVoltage V is measured in the resistance value of 140 ends, Ry representative
d160 ends are to the resistance value of first end that detects resistance 108, and meet and the relation of Vreg＞Vref.
Then please continue with reference to figure 2, Fig. 2 is the led drive circuit of another preferred embodiment of the present invention.This led drive circuit 200 comprises power supply changeover device 202, LED (LightEmitting Diode, light emitting diode) load 204, detects resistance 206, first resistance 208, second resistance 210, input voltage source 212, reference voltage V
Ref214, calibration voltage V
Reg216, measure voltage V
d218 and output voltage 220.
Wherein, the first input end of power supply changeover device 202 is electrically connected on input voltage source 212, comes driving LED load 204, the second input ends to be electrically connected on reference voltage V to receive voltage
Ref214, the three input ends are electrically connected on second end of first resistance 208 and first end of second resistance 210, measure voltage V to receive one group
d218, output terminal then output voltage 220 uses for LED load 204 with output driving current to first end of load 204.
First end of first resistance 208 is electrically connected on calibration voltage V
Reg216, second end is electrically connected on first end of second resistance 210 and the 3rd input end of power supply changeover device 202, second end of second resistance 210 is electrically connected on second end and first end that detects resistance 206 of LED load 204, and second end that detects resistance 206 is electrically connected on earth terminal.
In the present embodiment, LED load 204 is by the circuit that several LED formed, and calibration voltage V
Reg216 must satisfy the condition of Vreg＞Vref, and I
LED2Be the load current of stream through LED load 204.
When the output voltage 220 of power supply changeover device 202 during greater than the forward voltage drop sum of LED load 204, power supply changeover device 202 output current I
LED2Come driving LED load 204 to make it luminous, shinny, and this size of current is that power supply changeover device 202 is according to reference voltage V
Ref214 with measure voltage V
dDifference between 218 liang of voltage decides its output current value I
LED2Size, to control the brightness of LED load 204 accurately.
Wherein, reference voltage V
Ref214 are provided by external input voltage, are about 1.24V, and measure voltage V
d218 is for detecting the terminal voltage value at resistance two ends in known technology.But, cause owing to the resistance value of known detection resistance is excessive to consume too many power, so that make suitable low of whole known driving circuit efficient.
So, in the present embodiment, utilize by first resistance 208, second resistance 210 and calibration voltage V
RegThe 216 mensuration voltage compensating circuits of being formed compensate and measure voltage V
d218 magnitude of voltage.
Wherein, first resistance 208 is that R2 and detection resistance are R for R1, second resistance 210
SE CEIts relational expression is as shown in following:
(V
reg-V
ref)/R
1＝(V
ref-I
LED3*R
SE\CE)/R
2
The resistance value of first resistance 208 and second resistance 210 can be designed to more than tens of K ohms in design, so measure in the voltage compensation loop calibration voltage V at this
Reg216 most voltages all drop on first resistance 208 and second resistance 210, make to measure voltage V
d218 are not just judged by the voltage that detects resistance 206 two ends, provide this to measure voltage V and be transformed into by second resistance 210 and detection resistance 206 terminal voltage sums
d218.
By such design, can be so that detection resistance 206 that originally may tens of K ohms, owing to added first resistance 208, second resistance 210 and calibration voltage V
RegAfter 216, can be reduced to tens of ohm resistance, also reach simultaneously and reduce the voltage drop that the detection resistance 206 of tens of K ohms is originally caused, such benefit is that the power that input voltage source 212 is exported almost can all consume in load 204, integral body has improved the efficient of input voltage source 212, and has reached less electricity consumption.
Therefore in sum, the mensuration voltage compensating circuit that the present invention has formed because of having adopted bleeder circuit and calibration voltage can reduce to detect the resistance value of resistance, to reach power saving and the purpose of raising the efficiency.
Though the present invention with preferred embodiment openly as above; right its is not in order to limit the present invention; the ordinary skill of any technical field that the present invention belongs to; in thought that does not break away from the present invention and scope; when can doing a little change and improvement, so the present invention's protection domain is as the criterion when looking claims person of defining.
Claims (7)
1. led drive circuit is characterized in that comprising:
The LED load;
Detect resistance, the output terminal that first end is connected to this LED load is with the flow through output current of this LED load of reception, and this detects the second end ground connection of resistance;
Bleeder circuit is connected to first end and the correction voltage of this detection resistance; And
Power supply changeover device, first end is connected to the input power supply, second termination is received reference voltage signal, the 3rd termination is received the mensuration voltage signal that this bleeder circuit is exported, when measuring voltage signal greater than reference voltage signal, this power supply changeover device is measured the difference of voltage signal according to this reference voltage signal and this, to regulate the stable output current of supplying with this LED load.
2. the led drive circuit according to claim 1 is characterized in that this LED load is made up of a plurality of LED.
3. the led drive circuit according to claim 1 is characterized in that this power supply changeover device also comprises comparer, pulsed modulation formula electric pressure converter, buffer memory, transistor switch and boosts and reduction voltage circuit.
4. the led drive circuit according to claim 1 is characterized in that this power supply changeover device is the integrated-type electronic chip.
5. the led drive circuit according to claim 1 is characterized in that this power supply changeover device has width modulation or pulse frequency modulation function.
6. the led drive circuit according to claim 1, it is characterized in that this bleeder circuit also comprises at least the first resistance and second resistance, second end of first resistance is electrically connected on correction voltage, and first end of first resistance is electrically connected on first end of second resistance and the 3rd input end of power supply changeover device, and second end of second resistance is electrically connected on the output terminal and first end that detects resistance of LED load.
7. the led drive circuit according to claim 6 is characterized in that this correction voltage is that Vreg, this reference voltage are Vref, and this first resistance is that Rx, this second resistance are that Ry, this output current are I
LED2, this detection resistance is Rsence, and this bleeder circuit meets following formula:
(V
reg-V
ref)/R
X＝(V
ref-I
LED2*R
SENCE)/R
Y。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100911792A CN100383837C (en) | 2004-11-23 | 2004-11-23 | Driving circuit of light-emitting diode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100911792A CN100383837C (en) | 2004-11-23 | 2004-11-23 | Driving circuit of light-emitting diode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1779749A CN1779749A (en) | 2006-05-31 |
| CN100383837C true CN100383837C (en) | 2008-04-23 |
Family
ID=36770064
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2004100911792A Expired - Fee Related CN100383837C (en) | 2004-11-23 | 2004-11-23 | Driving circuit of light-emitting diode |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100383837C (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20090043865A (en) * | 2007-10-30 | 2009-05-07 | 삼성전자주식회사 | Liquid crystal display and driving method of the same |
| CN101739943B (en) * | 2008-11-11 | 2013-09-18 | 立锜科技股份有限公司 | Current regulator and method for improving LED display system performance |
| CN102196618B (en) * | 2010-03-16 | 2015-07-22 | 成都芯源系统有限公司 | LED illumination driving circuit and method |
| CN102340904B (en) * | 2010-07-14 | 2015-06-17 | 通用电气公司 | Light-emitting diode driving device and driving method thereof |
| CN102332243A (en) * | 2011-09-16 | 2012-01-25 | 明基电通有限公司 | Power converter and relevant display system |
| US8994639B2 (en) | 2012-05-16 | 2015-03-31 | Shenzhen China Star Optoelectronics Technology Co., Ltd. | LED backlight driving circuit, backlight module, and LCD device |
| CN102682719B (en) * | 2012-05-16 | 2015-07-15 | 深圳市华星光电技术有限公司 | LED (Light Emitting Diode) backlight driving circuit, backlight module and liquid crystal display device |
| CN109686322B (en) * | 2019-02-19 | 2021-11-23 | 昆山龙腾光电股份有限公司 | Switching circuit and backlight driving circuit |
| CN109856524B (en) * | 2019-02-19 | 2021-04-13 | 无锡英迪芯微电子科技股份有限公司 | Voltage measurement method and voltage measurement circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11305198A (en) * | 1998-04-24 | 1999-11-05 | Optrex Corp | Liquid crystal display device |
| JP2001325824A (en) * | 2000-05-17 | 2001-11-22 | Kyocera Corp | Led drive circuit for backlight at portable terminal |
-
2004
- 2004-11-23 CN CNB2004100911792A patent/CN100383837C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11305198A (en) * | 1998-04-24 | 1999-11-05 | Optrex Corp | Liquid crystal display device |
| JP2001325824A (en) * | 2000-05-17 | 2001-11-22 | Kyocera Corp | Led drive circuit for backlight at portable terminal |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1779749A (en) | 2006-05-31 |
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Granted publication date: 20080423 Termination date: 20151123 |