CN101778508B - Driving circuit and method of light emitting diode - Google Patents
Driving circuit and method of light emitting diode Download PDFInfo
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- CN101778508B CN101778508B CN2010100028189A CN201010002818A CN101778508B CN 101778508 B CN101778508 B CN 101778508B CN 2010100028189 A CN2010100028189 A CN 2010100028189A CN 201010002818 A CN201010002818 A CN 201010002818A CN 101778508 B CN101778508 B CN 101778508B
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- emitting diode
- light emitting
- led driving
- diode string
- resistance
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Abstract
The invention provides driving circuit and method of a light emitting diode. The driving circuit of the light emitting diode comprises a driving integrated circuit of the light emitting diode, a light emitting diode string and a resistor. The light emitting diode string is electrically connected with power supply voltage and a control end of the driving integrated circuit of the light emitting diode for accepting the control of the driving integrated circuit of the light emitting diode on driving current of the light emitting diode string; and the resistor is electrically connected to the control end and preset potential.
Description
Technical field
The invention relates to light-emitting diode Driving technique field, and particularly relevant for a kind of LED driving circuit and driving method.
Background technology
See also Fig. 1, it shows a kind of LED driving circuit that is relevant to known technology.As shown in Figure 1, LED driving circuit 10 comprises LED driving integrated circuit 12, a plurality of light emitting diode string 14 and a plurality of transistor 16.
LED driving integrated circuit 12 has a plurality of control pins 121 with the control end as the drive current of light emitting diode string 14, and it is a drive current of controlling light emitting diode string 14 with PWM (PWM) mode.One end of each light emitting diode string 14 is electrically connected to supply voltage VDD, and the transistor 16 that the other end joins through series connection with it is electrically connected to the control corresponding pin 121 of LED driving integrated circuit 12; The conduction and cut-off state of transistor 16 is to be determined by grid control signal Vg.Moreover each light emitting diode string 14 comprises a plurality of light-emitting diodes that are connected in series 141 respectively, because light-emitting diode 141 is driven in forward bias, the size of drive current changes the cross-pressure that can influence light-emitting diode.
Drive with the PWM mode in the process of each light emitting diode string 14 in LED driving integrated circuit 12, at PWM signal V
PWMClose the cycle in (off cycle), the cross-pressure of light-emitting diode 141 with respect to it at PWM signal V
PWMCan descend in the unlatching cycle (on cycle); Make the voltage on the control pin 121 of LED driving integrated circuit 12 increase; This moment, grid control signal Vg then can make transistor 16 end, and ran into the problem that control pin 121 withstand voltage deficiencies are broken to avoid LED driving integrated circuit 12.
In known technology; Though can be used for avoiding the control pin 121 of LED driving integrated circuit 12 to be broken because of withstand voltage deficiency through the dividing potential drop of the transistor 16 that is connected in series with light emitting diode string 12, the configuration of right transistor 16 certainly will cause the cost of LED driving circuit 10 to rise.
Summary of the invention
The object of the invention is providing a kind of LED driving circuit exactly, can avoid the control pin of LED driving integrated circuit to meet with the problem of breaking because of withstand voltage deficiency and have low relatively cost, to overcome the defective that exists in the known technology.
A purpose more of the present invention provides a kind of LED driving method.
A kind of LED driving circuit that the embodiment of the invention proposes comprises LED driving integrated circuit, light emitting diode string and resistance.Wherein, Light emitting diode string is electrically connected between the control end of supply voltage and LED driving integrated circuit to accept the control of LED driving integrated circuit to the drive current of light emitting diode string by this; Resistance is electrically connected between the control end and preset potential of LED driving integrated circuit, resistance need meet the following conditions (1) and (2):
(V
out-N×V
f-off-min)＜V
th (1)
R=(V
out-N×V
f-off-min)/I (2)
Wherein, N is the quantity of said light-emitting diode, V
OutBe supply voltage, V
ThBe the withstand voltage critical value that the control end experience of said LED driving integrated circuit is broken because of withstand voltage deficiency, V
F-off-minFor each light-emitting diode that is connected in series in the said light emitting diode string is in the specific forward cross-pressure when closing in said light emitting diode string, I is that each the said light-emitting diode that is connected in series in the said light emitting diode string is in the specific Weak current that flows through said light emitting diode string when closing in said light emitting diode string.Wherein, light emitting diode string generally includes a plurality of semiconductor light-emitting-diodes that are connected in series or Organic Light Emitting Diode.
In one embodiment of this invention, above-mentioned LED driving circuit more comprises (Boost) circuit that boosts, and be electrically connected between LED driving integrated circuit and the supply voltage, and execution is boosted to produce above-mentioned supply voltage according to input voltage.
In one embodiment of this invention, above-mentioned LED driving integrated circuit comprises that the PWM circuit is to control the drive current of light emitting diode string according to this PWM circuit.
In one embodiment of this invention; The quantity of above-mentioned light emitting diode string is a plurality of; And the quantity of the quantity of control end and resistance is all a plurality of; Thereby each light emitting diode string is electrically connected on corresponding each control end and supply voltage, and each resistance is electrically connected on corresponding each control end and preset potential.
A kind of LED driving method that the embodiment of the invention proposes is applicable to driven for emitting lights diode string; It comprises step: light emitting diode string is electrically connected between supply voltage and the LED driving integrated circuit, to drive this light emitting diode string through LED driving integrated circuit; First end of resistance is electrically connected between light emitting diode string and the LED driving integrated circuit, and makes second end of resistance be electrically connected to preset potential; And the resistance of setting resistance need meet the following conditions (1) and (2):
(V
out-N×V
f-off-min)＜V
th (1)
R=(V
out-N×V
f-off-min)/I (2)
Wherein, N is the quantity of said light-emitting diode, V
OutBe supply voltage, V
ThBe the withstand voltage critical value that the control end experience of said LED driving integrated circuit is broken because of withstand voltage deficiency, V
F-off-minFor each light-emitting diode that is connected in series in the said light emitting diode string is in the specific forward cross-pressure when closing in said light emitting diode string; I is that each the said light-emitting diode that is connected in series in the said light emitting diode string is in the specific Weak current that flows through said light emitting diode string when closing in said light emitting diode string, makes the current potential subcritical value of first end that when light emitting diode string is pent, is provided to resistance.Wherein, LED driving integrated circuit can come driven for emitting lights diode string through the PWM mode usually.
In one embodiment of this invention; The resistance of above-mentioned setting resistance comprises the step of the current potential subcritical value of first end that when light emitting diode string is pent, is provided to resistance: according to the forward cross-pressure (forward voltage) of each light-emitting diode when light emitting diode string is pent in supply voltage and the selected light emitting diode string of this critical value; Obtain each light-emitting diode with the corresponding forward current of forward cross-pressure (forward current); And the resistance that calculates resistance according to supply voltage, forward cross-pressure and forward current.
The embodiment of the invention is electrically connected on through the resistance with the suitable resistance of tool between the node and preset potential between the control end of light emitting diode string and LED driving integrated circuit; Utilize the setting resistance sizes to make light emitting diode string in the PWM signal at stop cycle, have specific Weak current to stay; This Weak current does not influence the overall brightness of light-emitting diode and can make light emitting diode string keep specific cross-pressure; Voltage to reach on the control end of LED driving integrated circuit can be not too high, thereby reach the purpose of the control end of protection LED driving integrated circuit.In addition, the use of resistance has relatively low cost.
Description of drawings
Fig. 1 shows a kind of LED driving circuit that is relevant to known technology.
Fig. 2 shows a kind of LED driving circuit that is relevant to the embodiment of the invention.
Fig. 3 shows the current-voltage characteristic curve of the light-emitting diode that is relevant to the embodiment of the invention.
Drawing reference numeral
10,30: LED driving circuit
12,32: LED driving integrated circuit
320: the PWM circuit
121,321: the control pin
14,34: light emitting diode string
141,341: light-emitting diode
16: transistor
VDD: supply voltage
Vg: grid control signal
V
PWM: the PWM signal
33: booster circuit
V
In: input voltage
V
Out: supply voltage
R: resistance
GND: earthing potential
Embodiment
For let above-mentioned and other purposes of the present invention, feature and advantage can be more obviously understandable, hereinafter is special lifts preferred embodiment, and cooperates appended accompanying drawing, elaborates as follows.
See also Fig. 2, it shows a kind of LED driving circuit that is relevant to the embodiment of the invention.As shown in Figure 2, LED driving circuit 30 comprises LED driving integrated circuit 32, booster circuit 33, a plurality of light emitting diode string 34 and a plurality of resistance R.
LED driving integrated circuit 32 has a plurality of control pins 321, and LED driving integrated circuit 32 comprises that PWM circuit 320 drives each light emitting diode string 34 with the PWM mode in present embodiment; Wherein, PWM circuit 320 provides PWM signal V
PWMA plurality of transistors to being connected with control pin 321 switch each transistorized conduction and cut-off state, and each control pin 321 is then controlled the control end of the drive current of each light emitting diode string 34 as LED driving integrated circuit 32.It should be noted, though all the PWM signal V in Fig. 2
PWMBe connected together, but this is not to represent these transistors must be with same PWM signal V
PWMDrive.Be used for driving each transistorized PWM signal V
PWMCan be one, also can be a lot of.The number end of PWM signal sees that why the demand in when design decide, and is not to be unmodifiable.
One end of each light emitting diode string 34 is electrically connected to the output of booster circuit 33 to receive supply voltage V
Out, the other end is electrically connected to each control pin 321 of LED driving integrated circuit 32.At this, each light emitting diode string 34 comprises a plurality of light-emitting diodes that are connected in series 341 respectively, and because light-emitting diode 341 is driven in forward bias, the size of drive current changes the forward cross-pressure that can influence light-emitting diode 341.In other words, the PWM signal V in Fig. 2
PWMThe cross-pressure of closing the cycle each light-emitting diode that is connected in series 341 in (off cycle) normally less than it at PWM signal V
PWMThe unlatching cycle (on cycle) in cross-pressure.Thereby, at PWM signal V
PWMClose the cycle in (off cycle), can compare higher across each control voltage on pin 321 of LED driving integrated circuit 32.
One end of each resistance R is electrically connected between the control corresponding pin 321 of each light emitting diode string 341 and LED driving integrated circuit 32, and the other end is electrically connected to preset potential for example earthing potential GND or other suitable power supply potentials.
To combine Fig. 3 to specify the embodiment of the invention below is how to utilize the resistance size of setting resistance R to reach the purpose of the control pin 321 of protection LED driving integrated circuit 32; Fig. 3 shows current-voltage (I-V) characteristic curve of light-emitting diode 341, and transverse axis is forward cross-pressure V
f(unit is a volt (V)), the longitudinal axis is forward current I
f(unit is micromicroampere (μ A)); In addition because the resistance size determining method of each resistance R in the present embodiment is identical, so below any a string with in a plurality of light emitting diode string 34 among Fig. 2 only as describing for example.
Be convenient explanation; The quantity of the light-emitting diode 341 in the hypothesis light emitting diode string 34 is that N and each light-emitting diode 341 have identical I-V characteristic curve earlier, and the withstand voltage critical value that the experience of the control pin 321 of definition LED driving integrated circuit 32 is broken because of withstand voltage deficiency is V
Th, each light-emitting diode that is connected in series 341 in the light emitting diode string 34 in light emitting diode string 34 be in when closing (that is, PWM signal V
PWMClose in the cycle) specific forward cross-pressure be V
F-off-min, PWM signal V
PWMClosing the specific Weak current that flows through light emitting diode string 34 in the cycle is I.Break for the control pin 321 of effectively avoiding LED driving integrated circuit 32 meets with, (1) and (2) then need meet the following conditions:
(V
out-N×V
f-off-min)＜V
th ……(1)
R=(V
out-N×V
f-off-min)/I ……(2)
The big I of the resistance of resistance R determines by following mode: at supply voltage V
OutAnd withstand voltage critical value V
ThUnder the known situation, can be according to the specific forward cross-pressure V of selected each light-emitting diode 341 of condition (1)
F-off-minValue, obtain and specific forward cross-pressure V according to the I-V characteristic curve that Fig. 3 illustrated then
F-off-minThe value of corresponding specific Weak current I is (for example shown in Figure 3: as to work as V
F-off-minDuring for 2.3V, then specific Weak current I is about 1.8 μ A), can calculate the value of resistance R afterwards according to condition (2).Need to prove that so-called " specific Weak current I " is meant at PWM signal V
PWMClose the forward current that can not influence the overall brightness of light emitting diode string 34 in the cycle.
At this, because the configuration of the resistance R of the suitable resistance of tool, at PWM signal V
PWMThe cross-pressure of closing light emitting diode string 34 in the cycle is raised with respect to the situation that does not dispose resistance R, thereby makes at PWM signal V
PWMThe voltage of closing in the cycle on the control pin 321 of LED driving integrated circuit 32 correspondingly can be reduced to withstand voltage critical value V
ThBelow, reach the purpose that pin 321 is controlled in protection.
Though the present invention discloses as above with preferred embodiment; Right its is not that the technical staff of any ability is not breaking away from the spirit and scope of the present invention in order to qualification the present invention; When can doing a little change and retouching, so protection scope of the present invention is when being as the criterion with claim institute confining spectrum.
Claims (8)
1. a LED driving circuit is characterized in that, said LED driving circuit comprises:
One LED driving integrated circuit has at least one control end;
At least one light emitting diode string, said light emitting diode string are electrically connected between a supply voltage and the said control end; And
At least one resistance, said resistance are electrically connected between a said control end and the preset potential, said resistance need meet the following conditions (1) and (2):
(V
out-N×V
f-off-min)＜V
th (1)
R=(V
out-N×V
f-off-min)/I (2)
Wherein, N is the quantity of said light-emitting diode, V
OutBe supply voltage, V
ThBe the withstand voltage critical value that the control end experience of said LED driving integrated circuit is broken because of withstand voltage deficiency, V
F-off-minFor each light-emitting diode that is connected in series in the said light emitting diode string is in the specific forward cross-pressure when closing in said light emitting diode string, I is that each the said light-emitting diode that is connected in series in the said light emitting diode string is in the specific Weak current that flows through said light emitting diode string when closing in said light emitting diode string.
2. LED driving circuit as claimed in claim 1 is characterized in that, said LED driving circuit more comprises:
One booster circuit, said booster circuit are electrically connected between said LED driving integrated circuit and the said supply voltage, carry out according to an input voltage and boost to produce said supply voltage.
3. LED driving circuit as claimed in claim 1 is characterized in that, said LED driving integrated circuit comprises:
One PWM circuit is controlled the drive current of said light emitting diode string according to said PWM circuit.
4. LED driving circuit as claimed in claim 1 is characterized in that,
The quantity of said light emitting diode string is a plurality of; And
The quantity of said control end and the quantity of said resistance are all a plurality of; Thereby each said light emitting diode string is electrically connected on corresponding each said control end and said supply voltage, and each said resistance is electrically connected on corresponding each said control end and said preset potential.
5. LED driving circuit as claimed in claim 1 is characterized in that, said light emitting diode string comprises a plurality of semiconductor light-emitting-diodes that are connected in series.
6. LED driving circuit as claimed in claim 1 is characterized in that, said light emitting diode string comprises a plurality of Organic Light Emitting Diodes that are connected in series.
7. a LED driving method is characterized in that, said method is applicable to and drives a light emitting diode string, comprises the following steps:
Said light emitting diode string is electrically connected between a supply voltage and the LED driving integrated circuit;
First end of one resistance is electrically connected between said light emitting diode string and the said LED driving integrated circuit, and makes second end of said resistance be electrically connected to a preset potential; And
The resistance of setting said resistance need meet the following conditions (1) and (2):
(V
out-N×V
f-off-min)＜V
th (1)
R=(V
out-N×V
f-off-min)/I (2)
Wherein, N is the quantity of said light-emitting diode, V
OutBe supply voltage, V
ThBe the withstand voltage critical value that the control end experience of said LED driving integrated circuit is broken because of withstand voltage deficiency, V
F-off-minFor each light-emitting diode that is connected in series in the said light emitting diode string is in the specific forward cross-pressure when closing in said light emitting diode string; I is that each the said light-emitting diode that is connected in series in the said light emitting diode string is in the specific Weak current that flows through said light emitting diode string when closing in said light emitting diode string, makes the current potential that when said light emitting diode string is pent, is provided to first end of said resistance be lower than a critical value.
8. LED driving method as claimed in claim 7 is characterized in that, said method more comprises step:
Said LED driving integrated circuit drives said light emitting diode string through a PWM mode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010100028189A CN101778508B (en) | 2010-01-18 | 2010-01-18 | Driving circuit and method of light emitting diode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010100028189A CN101778508B (en) | 2010-01-18 | 2010-01-18 | Driving circuit and method of light emitting diode |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101778508A CN101778508A (en) | 2010-07-14 |
| CN101778508B true CN101778508B (en) | 2012-10-31 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010100028189A Active CN101778508B (en) | 2010-01-18 | 2010-01-18 | Driving circuit and method of light emitting diode |
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|---|---|
| CN (1) | CN101778508B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102438346A (en) * | 2010-09-29 | 2012-05-02 | 通嘉科技股份有限公司 | Driving integrated circuit of light-emitting diode |
| TW201216763A (en) | 2010-10-06 | 2012-04-16 | Novatek Microelectronics Corp | Light-emitting diode driving device, light-emitting diode device method for driving the same |
| CN102446492A (en) * | 2010-10-08 | 2012-05-09 | 联咏科技股份有限公司 | Short-circuit sensing circuit and method, and driving chip and equipment of light emitting diode |
| CN102467881A (en) * | 2010-11-09 | 2012-05-23 | 联咏科技股份有限公司 | Light-emitting diode (LED) driving device, LED apparatus and driving method thereof |
| KR101189313B1 (en) * | 2010-12-27 | 2012-10-09 | 엘지이노텍 주식회사 | Power supply apparatus |
| US9461028B2 (en) * | 2012-08-07 | 2016-10-04 | Koninklijke Philips N.V. | LED circuit |
Citations (4)
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|---|---|---|---|---|
| US6621235B2 (en) * | 2001-08-03 | 2003-09-16 | Koninklijke Philips Electronics N.V. | Integrated LED driving device with current sharing for multiple LED strings |
| US6636003B2 (en) * | 2000-09-06 | 2003-10-21 | Spectrum Kinetics | Apparatus and method for adjusting the color temperature of white semiconduct or light emitters |
| US6864867B2 (en) * | 2001-03-28 | 2005-03-08 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | Drive circuit for an LED array |
| CN1889806A (en) * | 2006-07-20 | 2007-01-03 | 友达光电股份有限公司 | Driving device for light-emitting diode |
-
2010
- 2010-01-18 CN CN2010100028189A patent/CN101778508B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6636003B2 (en) * | 2000-09-06 | 2003-10-21 | Spectrum Kinetics | Apparatus and method for adjusting the color temperature of white semiconduct or light emitters |
| US6864867B2 (en) * | 2001-03-28 | 2005-03-08 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | Drive circuit for an LED array |
| US6621235B2 (en) * | 2001-08-03 | 2003-09-16 | Koninklijke Philips Electronics N.V. | Integrated LED driving device with current sharing for multiple LED strings |
| CN1889806A (en) * | 2006-07-20 | 2007-01-03 | 友达光电股份有限公司 | Driving device for light-emitting diode |
Also Published As
| Publication number | Publication date |
|---|---|
| CN101778508A (en) | 2010-07-14 |
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