CN1801300A - Parallel connection LED drive circuit with adaptive mode switching - Google Patents
Parallel connection LED drive circuit with adaptive mode switching Download PDFInfo
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- CN1801300A CN1801300A CN 200610023332 CN200610023332A CN1801300A CN 1801300 A CN1801300 A CN 1801300A CN 200610023332 CN200610023332 CN 200610023332 CN 200610023332 A CN200610023332 A CN 200610023332A CN 1801300 A CN1801300 A CN 1801300A
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- voltage
- operational amplifier
- parallel connection
- drive circuit
- led drive
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Abstract
Disclosed is a parallel LED driving circuit with self-adapting switching mode which comprises: current control module; operation amplifier (A1); resistors (R1, R2); a feedback control loop which includes a second operation amplifier (A2) and current mirrors (I1, I2) connected with A2. The invention is characterized in that: the voltage difference that is amplified by A2 between voltage (VDROP1) and reference voltage (VREF2) on the current control module controls the current of current mirror (I2) that flows through the resistor (R2); voltage on R2 is amplified by amplifier (A1) and fed back to the negative terminal of the second amplifier (A2) to ensure the voltage value (VDROP1) equals the reference voltage value (VREF2).
Description
Technical field
The present invention relates to a kind of Analogous Integrated Electronic Circuits, especially refer to have the parallel connection type driving circuit that adaptive model switches.
Background technology
In the backlight drive circuit of portable equipments such as mobile phone, MP3, usually, be the total system power supply by a lithium battery, lithium battery voltage is generally between 3.6V-4.2V.And the threshold voltage variation of dissimilar white light LEDs (light emitting diode) is very big, changes the forward conduction voltage drop V of general LED simultaneously along with the variation of temperature and drive current
LEDMay be in the 2.5V-4.5V scope.Therefore for the big LED of conduction voltage drop, lithium battery voltage need be converted into higher voltage and just can provide enough driving forces.
Press the voltage transformation mode, driving circuit generally can be divided into two kinds, and a kind of is tandem drive, and based on inductive type DC-DC (DC-to-dc) boost conversion principle, all LED are connected in series; Another kind is in parallel the driving, and based on capacitive based charge pump multiplication of voltage principle, all LED are connected in parallel.
The mode advantage of tandem drive is the efficient height, the currents match degree height of each LED.But there is the EMI problem in its on ﹠ off operation mode, can bring very big influence to the receiving sensitivity of mobile communication terminals such as mobile phone.
And parallel driver circuit, owing to be to adopt the charge pump of the electric capacity principle of boosting, the interference that it forms power supply is much smaller than the tandem drive circuit.But the efficiency of charge pump circuit becomes a restriction in its application again, so efficient becomes a key issue in the design of parallel connection type led drive circuit.
As shown in Figure 1, the parallel connection type drive circuit chip comprises voltage conversion circuit 1, current control module 2, capacitor C
Out, voltage conversion circuit generally can provide two kinds of mode of operations, i.e. LDO (linear voltage regulator) pattern and charge pump (CHARGE PUMP) pattern, and under the LDO pattern, V
CONVERTVoltage is V
BATTERY, be called 1 * mode of operation.Under charge pump modes, V
CONVERTBoost to 1.5 times of V
BATTERYVoltage is called 1.5 * mode of operation.
Usually circuit can switch between two kinds of mode of operations according to the desired driving force of load.Mode switch points V
THFor:
V
TH＝V
DROP1+V
DROP2+V
LED?(1)
The mode switch criterion is:
V
BATTERY＞＝V
TH (2)
Wherein: V
DROP1Be the pressure drop of chip internal current control module, this voltage is generally about 200mV.V
DROP2For chip operation under 1 * pattern, the desired minimum differntial pressure of internal drive transistor generally also needs about 200mV.V
BATTERYBe lithium battery voltage, V
LEDBe LED forward conduction voltage drop, V
DROPBe V
CONVERTWith V
OUTPressure reduction.
Therefore, under the situation that satisfies formula 2, voltage conversion circuit is operated in 1 * mode of operation.Efficient may be calculated in this case
Eff
1＝V
LED/V
BATTERY (3)
Along with the decline gradually of lithium battery voltage or the change of other condition, formula 2 does not satisfy, and voltage conversion circuit is operated in 1.5 * mode of operation.Efficient may be calculated in this case
Eff
1.5＝V
LED/(1.5×V
BATTERY) (4)
By formula 3 and formula 4,, be operated in the ratio of the efficient of 1.5 * pattern and 1 * pattern for same application conditions
Eff
1.5/Eff
1＝2/3 (5)
Obviously, in order to guarantee high conversion efficiency, voltage conversion circuit should be operated in 1 * mode of operation as much as possible.Therefore be that LED characteristic and working point are chosen suitable mode of operation and become the key of raising the efficiency according to load.
As shown in Figure 2, a kind of common mode control circuit comprises voltage conversion circuit 1, mode switch decision circuitry 3, current control module 2, operational amplifier A 1, divider resistance R1, R2, capacitor C
OutV
OUTVoltage is through being fed to the negative terminal of operational amplifier A 1 behind the electric resistance partial pressure, so in the open-loop gain of A1 enough under the situation of height (greater than 40dB):
V
OUT＝((R1+R2)/R2)×V
REF (6)
By the mode switch criterion that formula 2 provides, this control method has only and just is operated in 1 * mode of operation under the condition that satisfies formula 7.
V
BATTERY＞＝V
OUT+V
DROP2 (7)
Common V
OUTVoltage is set at more than the 4V, because V
OUTVoltage is defined, so mode switch points V
THDo not consider the actual conduction voltage drop of LED, can cause the loss in efficiency under the different situations.For example, work as V
BATTERY=4V under the condition of VLED=3V, can be operated in 1 * pattern and enters the work of 1.5 * pattern, and the loss of efficient is clearly.
Summary of the invention
The present invention aims to provide a kind of parallel connection LED drive circuit that adaptive model switches that has that can improve conversion efficiency.
A kind of parallel connection LED drive circuit that adaptive model switches that has provided by the present invention comprises voltage conversion circuit, mode switch decision circuitry, current control module, operational amplifier A 1, divider resistance R1, R2, capacitor C
Out, it is characterized in that: it also comprises a feedback control loop, this feedback control loop is connected between operational amplifier A 1 and the voltage conversion circuit 1, is used to the enough driving LED of voltage that guarantee that 1 conversion of voltage conversion circuit goes out.
In the above-mentioned parallel connection LED drive circuit with adaptive model switching, feedback control loop comprises current mirror I1, the I2 that one second operational amplifier A 2 and is attached thereto, and makes the voltage V on the current control module
DROP1With reference voltage V
REF2Difference control the electric current that described current mirror I2 flows through divider resistance R2 by the amplification of this second operational amplifier A 2, dividing potential drop on the resistance R 2 feeds back to the negative terminal of second operational amplifier A 2, the voltage V that guarantees at last through the amplification of operational amplifier A 1
DROP1With reference voltage V
REF2Value equates.
In above-mentioned parallel connection LED drive circuit with adaptive model switching, operational amplifier A 1 is provided with a soft start control end SOFT, be used for behind circuit start, provide one by setting the linear voltage signal that rises of slope, and because the FEEDBACK CONTROL effect of this operational amplifier drives output voltage V
OUTSteadily rise.
In above-mentioned parallel connection LED drive circuit with adaptive model switching, the voltage V on the current control module
DROP1Be set between the 200-400mV.
In the above-mentioned parallel connection LED drive circuit with adaptive model switching, the electric current I 1, the I2 that constitute current mirror are the unidirectional current source.
In the above-mentioned parallel connection LED drive circuit with adaptive model switching, the open-loop gain of operational amplifier A 1 is more than or equal to 40dB.
Owing to adopted above-mentioned technical solution, the present invention provides the mode of operation of two kinds of self-adaptations switchings as the backlight driving chip in the handheld devices such as mobile phone, MP3, reaches the high conversion efficiency of whole lithium battery operating voltage range.The present invention has also realized soft start and overvoltage protection when having guaranteed high conversion efficiency, and has very strong exploitativeness.
Description of drawings
Fig. 1 is the principle schematic of existing a kind of parallel connection LED drive circuit;
Fig. 2 is the principle schematic of existing another kind of parallel connection LED drive circuit;
Fig. 3 is the principle schematic that the present invention has the parallel connection LED drive circuit of adaptive model switching;
Fig. 4 is that the present invention has the circuit diagram of parallel connection LED drive circuit under the special case situation that adaptive model switches.
Embodiment
As shown in Figure 3, in circuit of the present invention, V
DROP1Voltage is set at fixing, a less magnitude of voltage that compares, generally between 200-400mV, so V
OUTVoltage no longer is the magnitude of voltage of fixing.According to formula 1, mode switch voltage V
THNo longer be fixed voltage also, and can adjust according to the forward conduction voltage drop of LED.
The mode switch criterion that provides according to formula 2, as can be seen: by mode switch voltage V
THAccording to the adaptive change of load LED characteristic, realized the adaptive control of mode switch.
As shown in Figure 3, the present invention, promptly a kind of parallel connection LED drive circuit with adaptive model switching comprises voltage conversion circuit 1, mode switch decision circuitry 3, current control module 2, operational amplifier A 1, divider resistance R1, R2, capacitor C
Out, and a feedback control loop, this feedback control loop comprises current mirror I1, the I2 that one second operational amplifier A 2 and is attached thereto.
1. the present invention has improved conversion efficiency.As shown in Figure 3, V
DROP1With V
REFThe amplification of difference by operational amplifier A 2 come Control current mirror I2 to flow through the electric current of divider resistance R2, the dividing potential drop on the resistance R 2 feeds back to the negative terminal of A2 at last through the amplification of operational amplifier A 1.By such feedback control loop, can guarantee V
DROP1With V
REF2The magnitude of voltage of setting equates, is generally 200mV.V
DROP2For chip operation under 1 * pattern, the desired minimum differntial pressure of internal drive transistor.Work as V
DROP2During＜150mV, the chip current driving force descends, and enters the work of 1.5 * pattern.
Therefore according to formula 2, as long as satisfy formula 8, chip operation is under 1 * pattern.
V
LED＜V
BATTERY-200mV-150mV (8)
For forward conduction voltage drop V
LEDWith interior LED, in the whole operating voltage range of lithium battery, all be operated in 1 * pattern at 3.2V.Even for the bigger LED of conduction voltage drop, can guarantee that also LED is in 1 * mode of operation in suitable one section operating voltage range of lithium battery.Obviously, voltage transitions efficient has the raising of certain degree.
2, the present invention has realized soft start, has reduced the rush of current to power supply.So-called soft start, i.e. V
OUTVoltage rises so that certain slope is linear, and the LED electric current rises to the start-up course of setting electric current from 0mA and is called soft start.The SOFT of operational amplifier A 1 end is the soft start control end, it after the chip operate as normal, to operational amplifier provide one by certain slope from 0V to V
BATTERYThe linear voltage signal that rises is because the FEEDBACK CONTROL effect of operational amplifier drives V
OUTSteadily rise.The LED cathode voltage is the feedback signal of operational amplifier A 2 because the present invention has sampled simultaneously, considers the non-linear of LED, and in soft start-up process, the LED cathode voltage can not be by following V significantly
OUTRise and rise.But because I1 and I2 are unidirectional current source (promptly can only can not suck electric current in the other direction by the direction as shown output current), so current mirror I1 and I2 are in off state, so the feedback control loop of A2 reality in soft start-up process has disconnected.
So in soft start-up process, actual operating circuit as shown in Figure 4, operational amplifier A 1 is as the main control amplifier, makes V
OUTVoltage can hold the rate of rise of control signal to rise according to SOFT.Soft start-up process is not affected because of the introducing of operational amplifier A 2.
Work as V
OUTRise to enough height, can drive when setting electric current V
DROP1Also rise to about 200mV, this moment, the control loop that A2 constituted played main retroactive effect owing to the amplification of A2.V like this
DROP1Be set at 200mV, finish soft start, enter normal operating conditions.
3, the present invention has realized overvoltage protection.Owing to LED opens circuit or other reason makes LED cathode voltage V
DROP1Be in Very Low Potential, as much smaller than 200mV.Because current mirror I1 and I2 are unidirectional current output, thus the operating circuit under this condition be still as shown in Figure 4 because the FEEDBACK CONTROL effect of operational amplifier A 1, V
OUTVoltage is stabilized in
V
OUT＝((R?1+R2)/R2)×V
REF1 (9)
Like this, V
OUTVoltage is defined, and has protected LED pipe and chip internal device, has realized overvoltage protection.
In sum, the fundamental purpose of mode switch control of the present invention is to improve the overall conversion efficiency in the lithium battery operating voltage range, and as previously mentioned, the efficient of 1 * mode of operation is apparently higher than the efficient of 1.5 * mode of operation.Most LED, working current forward conduction voltage drop when 20mA is generally less than 3.2V.It is high that the VTH voltage that scheme shown in Figure 2 requires under the same application conditions is obviously wanted.By the mode switch criterion that formula 2 provides, control method of the present invention can guarantee chip operation in 1 * mode of operation, and the control method of Fig. 2 is operated in 1.5 * pattern under the kindred circumstances in most of operating voltage range of lithium battery.So control method of the present invention can significantly improve efficient.In addition, the present invention has also realized soft start and overvoltage protection when having guaranteed high conversion efficiency.Therefore, the present invention had both guaranteed high performance, also had very strong exploitativeness simultaneously.
Above embodiment is only for the usefulness that the present invention is described, but not limitation of the present invention, person skilled in the relevant technique, under the situation that does not break away from the spirit and scope of the present invention, can also make various conversion or modification, therefore all technical schemes that are equal to also should belong within the category of the present invention, should be limited by each claim.And include within the scope of claim.
Claims (6)
1. one kind has the parallel connection LED drive circuit that adaptive model switches, and comprises voltage conversion circuit (1), mode switch decision circuitry (3), current control module (2), operational amplifier (A1), divider resistance (R1, R2), electric capacity (C
Out), it is characterized in that: it also comprises a feedback control loop, this feedback control loop is connected between operational amplifier (A1) and the voltage conversion circuit (1), is used to the enough driving LED of voltage that guarantee that the conversion of voltage conversion circuit (1) institute goes out.
2. the parallel connection LED drive circuit with adaptive model switching according to claim 1, it is characterized in that: described feedback control loop comprises one second operational amplifier (A2) and a current mirror that is attached thereto (I1, I2), makes the voltage (V on the current control module
DROP1) and reference voltage (V
REF2) difference control the electric current that described current mirror (I2) flows through divider resistance (R2) by the amplification of this second operational amplifier (A2), dividing potential drop on the resistance (R2) is through the amplification of operational amplifier (A1), feed back to the negative terminal of second operational amplifier (A2) at last, the voltage (V that guarantees
DROP1) and reference voltage (V
REF2) value equates.
3. the parallel connection LED drive circuit with adaptive model switching according to claim 2, it is characterized in that: described operational amplifier (A1) is provided with a soft start control end (SOFT), be used for behind circuit start, provide one by setting the linear voltage signal that rises of slope, and because the FEEDBACK CONTROL effect of this operational amplifier drives output voltage (V
OUT) steadily rise.
4. the parallel connection LED drive circuit with adaptive model switching according to claim 2 is characterized in that: the voltage (V on the described current control module
DROP1) be set between the 200-400mV.
5. the parallel connection LED drive circuit with adaptive model switching according to claim 2 is characterized in that: the electric current of described formation current mirror (I1, I2) is the unidirectional current source.
6. the parallel connection LED drive circuit with adaptive model switching according to claim 1, it is characterized in that: the open-loop gain of described operational amplifier (A1) is more than or equal to 40dB.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2006100233327A CN100392715C (en) | 2006-01-16 | 2006-01-16 | Parallel connection LED drive circuit with adaptive mode switching |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2006100233327A CN100392715C (en) | 2006-01-16 | 2006-01-16 | Parallel connection LED drive circuit with adaptive mode switching |
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| CN1801300A true CN1801300A (en) | 2006-07-12 |
| CN100392715C CN100392715C (en) | 2008-06-04 |
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|---|---|---|---|
| CNB2006100233327A Expired - Fee Related CN100392715C (en) | 2006-01-16 | 2006-01-16 | Parallel connection LED drive circuit with adaptive mode switching |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101902855A (en) * | 2009-05-27 | 2010-12-01 | 登丰微电子股份有限公司 | LED driving circuit and backlight module |
| CN102541135A (en) * | 2011-05-25 | 2012-07-04 | 北京国科世纪激光技术有限公司 | Parallel driving circuit for plurality of titanium pumps |
| CN102695343A (en) * | 2012-06-06 | 2012-09-26 | 矽力杰半导体技术(杭州)有限公司 | LED (Light Emitting Diode) driving circuit |
| CN103841728A (en) * | 2014-03-18 | 2014-06-04 | 杰华特微电子（杭州）有限公司 | Multichannel load balancing steady flow control circuit, corresponding circuit combination and control method |
| CN111477182A (en) * | 2019-01-23 | 2020-07-31 | 纬联电子科技(中山)有限公司 | Display device and power-off control method thereof |
| CN115035867A (en) * | 2022-07-20 | 2022-09-09 | 绵阳惠科光电科技有限公司 | Backlight driving circuit and method, backlight module and display device |
| US11854501B1 (en) | 2022-07-20 | 2023-12-26 | Mianyang HKC Optoelectronics Technology Co., Ltd. | Backlight driving circut, backlight module and display device |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100375513B1 (en) * | 2000-11-28 | 2003-03-10 | 삼성전기주식회사 | Inverter for back-light of LCD |
| JP3763830B2 (en) * | 2003-10-23 | 2006-04-05 | ローム株式会社 | Power supply |
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2006
- 2006-01-16 CN CNB2006100233327A patent/CN100392715C/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101902855A (en) * | 2009-05-27 | 2010-12-01 | 登丰微电子股份有限公司 | LED driving circuit and backlight module |
| CN101902855B (en) * | 2009-05-27 | 2013-04-17 | 登丰微电子股份有限公司 | LED driving circuit and backlight module |
| CN102541135A (en) * | 2011-05-25 | 2012-07-04 | 北京国科世纪激光技术有限公司 | Parallel driving circuit for plurality of titanium pumps |
| CN102541135B (en) * | 2011-05-25 | 2014-06-11 | 北京国科世纪激光技术有限公司 | Parallel driving circuit for plurality of titanium pumps |
| CN102695343A (en) * | 2012-06-06 | 2012-09-26 | 矽力杰半导体技术(杭州)有限公司 | LED (Light Emitting Diode) driving circuit |
| CN102695343B (en) * | 2012-06-06 | 2014-01-29 | 矽力杰半导体技术(杭州)有限公司 | LED (Light Emitting Diode) driving circuit |
| CN103841728A (en) * | 2014-03-18 | 2014-06-04 | 杰华特微电子（杭州）有限公司 | Multichannel load balancing steady flow control circuit, corresponding circuit combination and control method |
| CN111477182A (en) * | 2019-01-23 | 2020-07-31 | 纬联电子科技(中山)有限公司 | Display device and power-off control method thereof |
| CN111477182B (en) * | 2019-01-23 | 2022-03-04 | 纬联电子科技(中山)有限公司 | Display device and power-off control method thereof |
| CN115035867A (en) * | 2022-07-20 | 2022-09-09 | 绵阳惠科光电科技有限公司 | Backlight driving circuit and method, backlight module and display device |
| US11854501B1 (en) | 2022-07-20 | 2023-12-26 | Mianyang HKC Optoelectronics Technology Co., Ltd. | Backlight driving circut, backlight module and display device |
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|---|---|
| CN100392715C (en) | 2008-06-04 |
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