CN103906314B - LED drive circuit and method based on voltage memory with segmentation current limliting - Google Patents
LED drive circuit and method based on voltage memory with segmentation current limliting Download PDFInfo
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- CN103906314B CN103906314B CN201410076451.3A CN201410076451A CN103906314B CN 103906314 B CN103906314 B CN 103906314B CN 201410076451 A CN201410076451 A CN 201410076451A CN 103906314 B CN103906314 B CN 103906314B
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Abstract
The invention discloses a kind of LED drive circuit and method based on voltage memory and segmentation current limliting, described circuit comprises rectification circuit, bleeder circuit, voltage rise and fall detection module, voltage memory module, comparator bank, control logic module, high voltage switch circuit, inspection leakage resistance, inspection stream comparator and LED lamp string; The driving method of described circuit is according to the rise and fall characteristic of the DC pulse moving voltage after direct rectification, the control mode that adopts segmented to light to the load of LED lamp string. The problem of the difference that drive circuit of the present invention has solved the LED chip C-V characteristic that in practical application, lamp string uses on drive current impact; the operating current of LED lamp string within the whole work period is limited in the lowest high-current value Imax of design; avoid occurring the problem that brightness LED chip partially dark and that overcurrent causes that undercurrent causes damages; in improving LED lamp luminescence efficiency, better LED device is carried out to overcurrent protection.
Description
Technical field
The present invention relates to a kind of LED drive circuit and method, especially a kind ofly utilize straight after the direct rectification of electric mainStream pulsating volage is powered, and uses LED drive circuit and the method for voltage memory and segmentation current limliting, belongs to LEDActuation techniques field.
Background technology
LED illumination driving circuit, can make to adopt LED can normally work as the lighting apparatus of luminescent device exactlyNeeded power circuit, can provide required voltage and current for the normal work of LED device. LED illumination is drivenMove circuit structure framework as shown in Figure 1, mainly by rectification circuit, auxiliary power circuit, power converting circuit and anti-Feedback loop forms. The electric main of input is transformed into high direct voltage through rectification circuit, and high direct voltage is by accessory power supplyCircuit produces stable DC low-voltage power supply source translation circuit and uses, and power converting circuit is converted into high direct voltageThe voltage and current that the work of LED device is required, backfeed loop detects the duty of LED, controls by feedbackSystem makes the operating voltage of LED device and current stabilization on design point.
At present, because LED has higher efficiency than conventional light source at energy-saving square mask, its application is more and more extensive, eachPlant the driving power structure using in LED illuminating product also more and more abundanter. Existing LED segmented power supply asShown in Fig. 2, its course of work is as follows: when Output Voltage in Rectified Circuits is during lower than U1, NMOS pipe Q1, Q2,Q3, Q4 conducting, L1 section LED work; Output Voltage in Rectified Circuits is higher than U1 during lower than U2, and NMOS manages Q1Turn-off Q2, Q3, Q4 conducting, L1, L2 section LED work; Output Voltage in Rectified Circuits higher than U2 lower than U3Time, NMOS pipe Q1, Q2 turn-off, Q3, Q4 conducting, L1, L2, L3 section LED work; Rectification circuit outputVoltage is higher than U3 during lower than U4, and NMOS pipe Q1, Q2, Q3 turn-off, Q4 conducting, L1, L2, L3, L4Section LED work; When Output Voltage in Rectified Circuits is during higher than U4, NMOS pipe Q1, Q2, Q3, Q4 turn-off, L1,L2, L3, L4 section LED do not work.
LED segmented drive circuit described above carries out voltage energy storage without electrochemical capacitor, and power factor (PF) is higher, wholeThe lamp life-span can not be limited by electric capacity yet, but this type of drive also has weak point, from the C-V characteristic of LED device,Under its normal working voltage condition, the tiny difference of voltage can cause the obvious fluctuation of electric current, and the light intensity master of LEDTo and flow through the current related of LED; In actual applications, though the LED chip of same batch of production of same producer,Its VA characteristic curve also can exist difference, therefore according to fixed partial pressure than the type of drive of carrying out segmentation, due to useIn reference voltage precision relatively and the reason of LED chip C-V characteristic difference, make the work of LED in lamp stringElectric current can not accurately predicting and design, occurs the driving condition of undercurrent or overcurrent. Undercurrent can cause the brightness of lamp string inclined to one sideSecretly, overcurrent can cause damage to LED chip.
Summary of the invention
The object of the invention is the defect in order to solve above-mentioned prior art, provide a kind of simple in structure, easy to use,Neither need to adopt perceptual device, the LED drive circuit with segmentation current limliting based on voltage memory that also need not electrochemical capacitor.
Another object of the present invention is to provide a kind of driving with the LED drive circuit of segmentation current limliting based on voltage memoryMethod.
Object of the present invention can be by taking following technical scheme to reach:
LED drive circuit based on voltage memory with segmentation current limliting, comprise rectification circuit, bleeder circuit, comparator bank,High voltage switch circuit and LED lamp string, described rectification circuit is connected with bleeder circuit, described high voltage switch circuit and LEDLamp series winding connects, and described LED lamp string is connected with rectification circuit, it is characterized in that: also comprise that voltage rise and fall detect mouldPiece, voltage memory module, control logic module, inspection leakage resistance and inspection stream comparator, described voltage memory module,Comparator bank, control logic module, high voltage switch circuit and LED lamp string are connected successively; Described bleeder circuit respectively withVoltage rise and fall detection module is connected with voltage memory module, described voltage rise and fall detection module respectively with voltageMemory module is connected with control logic module, and described control logic module is connected with voltage memory module; Described height presses offClose circuit and hold and be connected altogether with power supply by inspection leakage resistance, input termination inspection leakage resistance of described inspection stream comparator andThe points of common connection of high voltage switch circuit, another input termination reference voltage, the output of described inspection stream comparator withControl logic module connects.
Preferably, described voltage memory module is made up of multiple voltage retainers, the output of described each voltage retainerEnd is connected with comparator bank respectively.
Preferably, described each voltage retainer is made up of electric capacity and operational amplifier.
Preferably, described comparator bank is made up of multiple voltage comparators, an input of described each voltage comparatorEnd connects one to one with the output of each voltage retainer, and another input is connected together rear and bleeder circuitConnect, the output of described each voltage comparator is connected with control logic module respectively.
Preferably, described control logic module is by multiple d type flip flops and complete the required combined digital logical constitution of function,Described control logic module is defeated with the output of each voltage comparator in comparator bank, voltage rise and fall detection moduleThe output going out and examine stream comparator is as input signal.
Preferably, described voltage rise and fall detection module is made up of differentiation element circuit and voltage comparator, and output refers toShow the square-wave signal of DC pulse moving voltage rise and fall state.
Preferably, described high voltage switch circuit is made up of multiple high pressure NMOS pipes, the storage of described each d type flip flopThe on off state of state and each high pressure NMOS pipe is corresponding one by one; The source electrode of described each high pressure NMOS pipe is connected on mutuallyHold and be connected altogether with power supply through inspection leakage resistance afterwards together, input termination inspection leakage resistance of described inspection stream comparator andThe points of common connection of the source electrode of each high pressure NMOS pipe, another input termination reference voltage; Described each high pressureThe drain electrode of NMOS pipe and LED lamp series winding connect.
Preferably, described LED lamp string is composed in series by multiple LED lamp sections, quantity and the high pressure of described LED lamp sectionThe quantity of NMOS pipe is consistent.
Another object of the present invention can be by taking following technical scheme to reach:
Driving method based on voltage memory with the LED drive circuit of segmentation current limliting, is characterized in that comprising the following steps:
1) electric main, after rectification circuit rectification, is exported HVDC pulsating volage;
2) the HVDC pulsating volage of bleeder circuit after to rectification circuit rectification carries out dividing potential drop according to a certain percentage, outputLow-voltage direct pulsating volage;
3) voltage rise and fall detection module converts the low-voltage direct pulsating volage after dividing potential drop to be used to indicate low-voltage direct toThe square-wave signal of the uphill process of pulsating volage and decline process;
4) in the uphill process of low-voltage direct pulsating volage, voltage in the time of valley, each high pressure NMOS pipeIn conducting state, now only have the LED lamp section being directly connected with HVDC pulsating volage to be access in effective driving defeatedOutbound port, makes the drive current of this LED lamp section reach cut-off current when voltage rises, and the pressure drop on inspection leakage resistance is higher than ginsengExamine voltage, the output voltage generation overcurrent upset of inspection stream comparator, control logic module detects the upset of this signal,The high pressure NMOS pipe being connected with this LED lamp section negative pole is turned off, next the LED lamp being connected with this LED lamp sectionDuan Yiqi is access in effective driver output port, and the electric current on LED lamp string is got back to below cut-off current, inspection stream comparatorBefore output voltage returns to overcurrent upset occurs; According to this rule, often reach primary current cut-off current just turn-off withThe connected high pressure NMOS pipe of part negative pole being access in LED lamp string, makes to be access in effective driver output portLED lamp hop count amount progressively increases; When all LED lamp Duan Jun are access in, the rising of HVDC pulsating volage againMake electric current reach cut-off current, turn-off all high pressure NMOS pipes in high voltage switch circuit, by institute in LED lamp stringHave the disconnection that is connected of LED lamp section and power supply, the control procedure in the uphill process of this DC pulse moving voltage is called forward controlProcess processed; In forward control procedure, the operating current that voltage memory module is write down LED lamp string successively reaches limit at every turnThe instantaneous voltage of low-voltage direct pulsating volage when flow valuve;
5), in the decline process of low-voltage direct pulsating volage, the magnitude of voltage of voltage memory module memory remains unchanged, defeatedEnter to comparator bank and compare processing, the square wave sequence of comparator bank output has oppositely been reappeared in voltage uphill processWhen LED lamp string reaches Current Limits flow valuve at every turn, each controls node; Control node, the output shape of comparator bank at eachState can change, and control logic module detects this state variation, oppositely progressively recovers each in high voltage switch circuitThe individual conducting state that is turned off high pressure NMOS pipe, realizes the reverse symmetry control to LED lamp string; In reverse symmetryIn the process of controlling, if all high pressure in the peak point place of HVDC pulsating volage high voltage switch circuitNMOS pipe is in off state, declines while controlling node through the 1st at HVDC pulsating volage, and control logicModule makes the high pressure NMOS pipe being finally turned off in forward control procedure recover conducting state, all in LED lamp stringLED lamp section is access in effective driver output port; In the time that HVDC pulsating volage declines through the 2nd control node,Control logic module makes the high pressure NMOS pipe that in forward control procedure, second-to-last is turned off recover conducting state, makesThe LED lamp section that is access in effective driver output port in LED lamp string reduces 1 section; According to this rule, after this high pressureDC pulse moving voltage declines and often controls when node through 1, the conducting that just recovers 1 high pressure NMOS pipe being turned offState, gradually reduces the LED lamp section that is access in effective driver output port in LED lamp string, until all heightPress NMOS pipe all to recover conducting state, in LED lamp string, be access in the number of the LED lamp section of effective driver output portTill amount is 1 section.
Preferably, step 3) described voltage rise and fall detection module converts the low-voltage direct pulsating volage after dividing potential drop toBe used to indicate the uphill process of low-voltage direct pulsating volage and the square-wave signal of decline process is specially:
Voltage rise and fall detection module converts low-voltage direct pulsating volage after dividing potential drop to only have two kinds of level of height toSquare-wave signal, uphill process and the decline of indication low-voltage DC pulse moving voltage respectively of two kinds of varying levels of this square-wave signalProcess, wherein high level instruction uphill process, low level instruction decline process, by this square wave signal inversion can obtain withThe indicating mode that original signal is contrary.
The present invention has following beneficial effect with respect to prior art:
The present invention is based on the LED drive circuit of voltage memory and segmentation current limliting according to the DC pulse moving voltage after direct rectificationRise and fall characteristic, the load of LED lamp string is adopted to the control mode lighted of segmented, solved lamp in practical applicationThe problem of the difference of the LED chip C-V characteristic that string uses on drive current impact, makes LED lamp string in whole workThe operating current of doing in the cycle is limited in the lowest high-current value Imax of design, avoids occurring that the brightness that undercurrent causes is inclined to one sideThe problem that LED chip dark and that overcurrent causes damages, in improving LED lamp luminescence efficiency, betterLED device is carried out to overcurrent protection.
Brief description of the drawings
Fig. 1 is LED drive circuit structural framing figure.
Fig. 2 is the structural principle block diagram of existing linear segmented formula LED drive circuit.
Fig. 3 is the structural principle block diagram that the present invention is based on the LED drive circuit of voltage memory and segmentation current limliting.
Fig. 4 is the driving method working waveform figure that the present invention is based on the LED drive circuit of voltage memory and segmentation current limliting.
Detailed description of the invention
Embodiment 1:
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited toThis.
As shown in Figure 3, the present embodiment based on voltage memory and the LED drive circuit of segmentation current limliting comprise rectification circuit 1,Bleeder circuit 2, voltage rise and fall detection module 3, voltage memory module 4, comparator bank 5, control logic module 6,High voltage switch circuit 7, inspection leakage resistance 8 (Ris), inspection stream comparator 9 (Icomp) and LED lamp string 10; DescribedVoltage rise and fall detection module 3 is made up of differentiation element circuit and voltage comparator; Described voltage memory module 4 is by 4Individual voltage retainer forms, and numbering is respectively H1, H2, H3 and H4 from top to bottom, described each voltage retainer byElectric capacity and operational amplifier composition; Described comparator bank 5 is made up of 4 voltage comparators, and numbering is distinguished from top to bottomFor Comp1, Comp2, Comp3 and Comp4; Described control logic module 6 is by 4 d type flip flops and complete meritCombined digital logical constitution that can be required; Described high voltage switch circuit 7 is made up of 4 high pressure NMOS pipes, numbering fromUnder going up extremely, be respectively Q1, Q2, Q3 and Q4; Described LED lamp string 10 is made up of 4 LED lamp sections, numbering fromUnder going up extremely, be respectively L1, L2, L3 and L4, wherein:
Electric main is after described rectification circuit 1 rectification, and output has the (letter of periodic HVDC pulsating volageBe called HVDCP), in the one-period of HVDCP, the process that voltage changes to peak value from valley is uphill process,The process of voltage from peak change to valley is decline process;
The HVDCP of described bleeder circuit 2 after to rectification circuit 1 rectification carries out linear dividing potential drop according to a certain percentage,To low-voltage direct pulsating volage (referred to as LVDCP), as voltage rise and fall detection module 3, voltage memory module4 and the input signal of comparator bank 5, compare the phase place of LVDCP and cycle and its phase with the HVDCP after rectificationWith, in magnitude of voltage size, be proportional routine relation;
Described voltage rise and fall detection module 3 converts the LVDCP after bleeder circuit 2 dividing potential drops to only have two kinds of height toThe square-wave signal RFC of level, two kinds of varying levels of this square-wave signal RFC indicate respectively LVDCP rising and underFall process, as high level instruction uphill process, low level is indicated decline process, after this signal inversion, can obtainTo the indicating mode contrary with original signal; The circuit module that need to use RFC signal when work has voltage memory module 4With control logic module 6;
Described voltage memory module 4 is in the uphill process of DC pulse moving voltage (HVDCP or LVDCP), successivelyThe instantaneous value of LVDCP when the drive current of writing down LED lamp string 10 reaches cut-off current at every turn, due to bleeder circuit 2Linear ratio relation, the instantaneous voltage of the LVDCP recording also becomes one with the instantaneous voltage of HVDCP this momentThe linear ratio relation of one correspondence, it adopts the mode of simulation to carry out voltage memory, the voltage retainer usingNumber is required memory voltage wink in a voltage uphill process of DC pulse moving voltage (HVDCP or LVDCP)The number of duration is also the number of fragments (being 4) of LED lamp string 10; Described voltage memory module 4 is at direct currentIn the decline process of pulsating volage (HVDCP or LVDCP), the magnitude of voltage of its memory remains unchanged, and is input to ratioCompared with comparing processing in device group 5;
In described comparator bank 5, described voltage comparator Comp1, Comp2, Comp3 and Comp4 one is defeatedEnter end and connect one to one with the output of voltage retainer H1, H2, H3 and H4 respectively, another input phaseAfter being connected together, be connected with bleeder circuit 2, LVDCP is as the input signal of this input; Described comparator bank 5In the decline process of DC pulse moving voltage (HVDCP or LVDCP), the output of voltage memory module 4 andLVDCP compares, and exports the square wave corresponding with voltage comparator Comp1, Comp2, Comp3 and Comp4Sequence, the square wave of each output, whether the variation instruction LVDCP of its low and high level has dropped to corresponding electricityThe memory voltage value of pressing comparator to input, the party's wave train has oppositely been reappeared LED lamp string 10 in voltage uphill processWhile reaching current limit value, each controls node at every turn, and is input to control logic module 6 and processes;
In described control logic module 6, the height in the store status of described each d type flip flop and high voltage switch circuit 7Press the on off state of NMOS pipe corresponding one by one, the exportable switching signal of control logic module 6 is to high voltage switch circuit7 high pressure NMOS pipe Q1, Q2, Q3 and Q4 carry out switch control; The positive pole of described LED lamp section L1 and wholeThe HVDCP that current circuit 1 is exported connects, and tie point is N0; The negative pole of described LED lamp section L1 and LED lamp sectionThe positive pole of L2 connects, and tie point is N1, and tie point N1 is connected with the drain electrode of high pressure NMOS pipe Q1; Described LEDThe negative pole of lamp section L2 is connected with the positive pole of LED lamp section L3, and tie point is N2, tie point N2 and high pressure NMOSThe drain electrode of pipe Q2 connects; The negative pole of described LED lamp section L3 is connected with the positive pole of LED lamp section L4, and tie point isN3, tie point N3 is connected with the drain electrode of high pressure NMOS pipe Q3; Negative pole and the high pressure NMOS of described LED lamp section L4The drain electrode of pipe Q4 connects, and tie point is N4; The source electrode of described high pressure NMOS pipe Q1, Q2, Q3 and Q4 joinsTogether, be connected with one end of inspection leakage resistance Ris, tie point is N5, another termination power of inspection leakage resistance RisHold altogether; Input termination inspection leakage resistance Ris of described inspection stream comparator Icomp and high pressure NMOS pipe Q1,The points of common connection N5 of the source electrode of Q2, Q3 and Q4, another input termination reference voltage Vref;
As shown in Figure 4, be the working waveform figure of the LED drive circuit of the present embodiment based on voltage memory and segmentation current limliting,The first half dotted line is the waveform of low-voltage direct pulsating volage signal LVDCP, and heavy line is that voltage rise and fall detect electricityThe square-wave waveform of the output signal RFC on road, the peak value that Umax is LCDCP; The latter half dotted line is low-voltage direct arteries and veinsThe waveform of moving voltage signal LVDCP, the peak value that Umax is LCDCP, heavy line is the electric current that flows through LED lamp stringILEDOscillogram, Imax is ILEDPeak value (being cut-off current), by the reference voltage that is input to inspection stream comparator IcompVref and inspection leakage resistance Ris determine, ILED=Vref/Ris。
As shown in Figure 3 and Figure 4, the driving side of the LED drive circuit of the present embodiment based on voltage memory and segmentation current limlitingMethod, comprises the following steps:
1) electric main, after rectification circuit 1 rectification, is exported HVDCP;
2) HVDCP of bleeder circuit 2 after to rectification circuit 1 rectification carries out dividing potential drop according to a certain percentage, outputLVDCP；
3) voltage rise and fall detection module 3 converts the low-voltage direct pulsating volage after dividing potential drop to only have two kinds of electricity of height toFlat square-wave signal RFC, within a rise and fall cycle of LVDCP, voltage rise and fall inspection in uphill processThe output signal RFC that surveys module 3 is high level, the output signal of voltage rise and fall detection module 3 in decline processRFC is low level, and control logic module 6 is according to its control model of low and high level Determines of RFC, below respectivelyThe control flow of the uphill process to LVDCP and decline process is described:
4) in the uphill process of LVDCP, voltage in the time of valley, each high pressure NMOS pipe Q1, Q2, Q3With Q4 all in conducting state, the time point t0 in corresponding diagram 4; In the process of time period t 0 to t1, high pressure NMOSPipe Q1, Q2, Q3 and Q4 are in conducting state, and tie point N1, N2, N3 and N4 are all by Q1, Q2, Q3Be shorted to tie point N5 with the conducting state of Q4, LED lamp section L2, L3 and L4 are invalid, and LED lamp section L1 is connectEnter between HVDCP and tie point N5 and effectively driven; At time point t1, flow through in LED lamp string 10 and be access inThe drive current I of LED lamp sectionLEDArrive cut-off current Imax, the output state of inspection stream comparator Icomp occurredStream upset, control logic module 6 detects overcurrent upset, output signal control voltage memory module 4 is kept by voltageDevice H1 remembers the now instantaneous voltage value Ua of LVDCP, makes high pressure NMOS pipe Q1 in off state, high pressureNMOS pipe Q2, Q3 and Q4 keep conducting state; In the process of time period t 1 to t2, high pressure NMOS pipeQ1 is in off state, and high pressure NMOS pipe Q2, Q3 and Q4 keep conducting state, tie point N2, N3 andN4 is all shorted to tie point N5 by the conducting state of high pressure NMOS pipe Q2, Q3 and Q4, LED lamp section L3 andL4 is invalid, and LED lamp section L1 and L2 are connected effectively to be driven between access HVDCP and tie point N5; ?After Q1 is turned off, ILEDAgain drop to below Imax, the output of inspection stream comparator Icomp returns to generation overcurrentState before upset. At time point t2, flow through the drive current I of the LED lamp section being access in LED lamp string 10LEDArrive cut-off current Imax, the output state generation overcurrent upset of inspection stream comparator Icomp, control logic module 6 detectsTo overcurrent upset, output signal control voltage memory module 4 remembers that by voltage retainer H2 LVDCP's now is instantaneousMagnitude of voltage Ub, makes high pressure NMOS pipe Q1 and Q2 in off state, and high pressure NMOS pipe Q3 and Q4 keepConducting state; In the process of time period t 2 to t3, high pressure NMOS pipe Q1, Q2 be in off state, Q3,Q4 keeps conducting state, and tie point N3, N4 are all shorted to N5 by the conducting state of Q3, Q4, LED lamp section L4Invalid, LED lamp section L1, L2 and L3 are connected effectively to be driven between access HVDCP and tie point N5; ?After Q1 and Q2 are turned off, ILEDAgain drop to below Imax, the output of inspection stream comparator Icomp returns to generationState before overcurrent upset; At time point t3, flow through the driving electricity of the LED lamp section being access in LED lamp string 10Stream ILEDArrive cut-off current Imax, the output state generation overcurrent upset of inspection stream comparator Icomp, control logic module6 detect overcurrent upset, and output signal control voltage memory module 4 is remembered now LVDCP by voltage retainer H3Instantaneous voltage value Uc, make high pressure NMOS pipe Q1, Q2 and Q3 in off state, high pressure NMOS pipe Q4Keep conducting state; In the process of time period t 3 to t4, high pressure NMOS pipe Q1, Q2 and Q3 are in turn-offing shapeState, high pressure NMOS pipe Q4 keeps conducting state, and tie point N4 is all by the conducting state of high pressure NMOS pipe Q4Be shorted to tie point N5, LED lamp section L1, L2, L3 and L4 are connected between access HVDCP and tie point N5Effectively driven; After Q1, Q2 and Q3 are turned off, ILEDAgain drop to below Imax inspection stream comparator IcompOutput return to the state occurring before overcurrent upset; At time point t4, flow through and be access in LED lamp string 10The drive current I of LED lamp sectionLEDArrive cut-off current Imax, the output state generation overcurrent of inspection stream comparator Icomp turns overTurn, control logic module 6 detects overcurrent upset, and output signal control voltage memory module 4 is by voltage retainer H4Remember the now instantaneous voltage value Ud of LVDCP, make high pressure NMOS pipe Q1, Q2, Q3 and Q4 in turn-offing shapeState; Reach in the process of peak value high pressure NMOS pipe Q1, Q2, Q3 and Q4 place in time period t 4 to LCDCPIn off state, LED lamp section L1, L2, L3 and L4 disconnect from effective output port, ILEDValue be 0, avoidThe continuation rising of voltage causes LED lamp string 10 overcurrents and suffers damage; After Q1, Q2, Q3 and Q4 are turned off,ILEDAgain drop to below Imax, the output of inspection stream comparator Icomp returns to the state occurring before overcurrent upset;
5), in the decline process of LVDCP, control logic module 6 determines high according to the output signal of comparator bank 5Press the on off state of NMOS pipe Q1, Q2, Q3 and Q4; At the peak point of LVDCP in the process of t5, thisTime LVDCP magnitude of voltage ULV> Ud > Uc > Ub > Ua, voltage comparator Comp1, Comp2 in comparator bank 5,The output state of Comp3 and Comp4 remains unchanged, and high pressure NMOS pipe Q1, Q2, Q3 and Q4 keep turn-offingState, LED lamp section L1, L2, L3 and L4 disconnect from effective output port, ILEDValue be 0; At time point t5In the process of t6, Ud > ULV> Uc > Ub > Ua, the output state of voltage comparator Comp1 changes, voltageThe output state of comparator C omp2, Comp3 and Comp4 remains unchanged, at this moment control logic module 6 basesThe output state of Comp1, Comp2, Comp3 and Comp4 makes high pressure NMOS pipe Q4 conducting, high pressure NMOSPipe Q1, Q2 and Q3 keep off state, LED lamp section L1, L2, L3 and L4 connected access HVDCP withBetween tie point N5, effectively driven; At time point t5, LVDCP during due to the voltage of LVDCP and t4 time pointMagnitude of voltage equate, and access LED lamp section identical, therefore t5 and t4 time point ILEDValue equate, and etc.In Imax, the process from time point t5 to t6, electric current ILEDReduce with voltage drop; At time point t6 to t7Process in, Ud > Uc > ULV> Ub > Ua, the output state of voltage comparator Comp2 changes, and voltage ratio isThe output state of device Comp1, Comp3 and Comp4 remains unchanged, and at this moment control logic module 6 is according to voltage ratioMake high pressure NMOS pipe Q3 and Q4 conducting compared with the output state of device Comp1, Comp2, Comp3 and Comp4,High pressure NMOS pipe Q1 and Q2 keep off state, and LED lamp section L1, L2 and L3 are connected accesses HVDCPAnd between tie point N5, effectively driven, L4 is invalid for LED lamp section; At time point t6, due to the voltage of LVDCPDuring with t3 time point, the magnitude of voltage of LVDCP equates, and the LED lamp section of access is identical, therefore t6 and t3 time pointILEDValue equate, and equal Imax, the process from time point t6 to t7, electric current I LED is with voltage dropReduce. At time point t7 in the process of t8, Ud > Uc > Ub > ULV> Ua, the output of voltage comparator Comp3State changes, and the output state of voltage comparator Comp1, Comp2 and Comp4 remains unchanged, this time controlLogic module 6 processed makes high pressure according to the output state of voltage comparator Comp1, Comp2, Comp3 and Comp4NMOS pipe Q2, Q3 and Q4 conducting, high pressure NMOS pipe Q1 keeps off state, LED lamp section L1 and L2Between series connection access HVDCP and tie point N5, effectively driven, LED lamp section L3 and L4 are invalid; In the timePoint t7, due to the voltage of LVDCP, the magnitude of voltage of LVDCP equates during with t2 time point, and the LED lamp section accessingIdentical, therefore t7 and t2 time point ILEDValue equate, and equal Imax, the process from time point t7 to t8,Electric current I LED reduces with voltage drop. At time point t8 in the process of t9, Ud > Uc > Ub > Ua > ULV,The output state of voltage comparator Comp4 changes, and voltage comparator Comp1, Comp2 and Comp3's is defeatedDo well and remain unchanged, at this moment control logic module 6 according to voltage comparator Comp1, Comp2, Comp3 andThe output state of Comp4 makes high pressure NMOS pipe Q1, Q2, Q3 and Q4 conducting, and L1 is by series connection for LED lamp sectionEnter between HVDCP and tie point N5 and effectively driven, LED lamp section L2, L3 and L4 are invalid; At time point t8,Due to the voltage of LVDCP, the magnitude of voltage of LVDCP equates during with t1 time point, and the LED lamp section of access is identical,Therefore t8 and t1 time point ILEDValue equate, and equal Imax, the process from time point t8 to t9, electric currentILED reduces with voltage drop, completes a LED in the LCDCP cycle drive control flow to this.
The above be only patent preferred embodiment of the present invention, but the protection domain of patent of the present invention is not limited toThis, for example, can change the quantity of voltage retainer, voltage comparator, high pressure NMOS pipe etc., is anyly familiar with this skillThe technical staff in art field in the disclosed scope of patent of the present invention, according to the present invention the technical scheme of patent and send outBright design is equal to replaces or changes, and all belongs to the protection domain of patent of the present invention.
Claims (5)
1. the LED drive circuit with segmentation current limliting based on voltage memory, comprises rectification circuit, bleeder circuit, comparisonDevice group, high voltage switch circuit and LED lamp string, described rectification circuit is connected with bleeder circuit, described high voltage switch circuitConnect with LED lamp series winding, described LED lamp string is connected with rectification circuit, it is characterized in that: under also comprising that voltage risesDetection module, voltage memory module, control logic module, inspection leakage resistance and inspection stream comparator fall, described voltage noteRecalling module, comparator bank, control logic module, high voltage switch circuit and LED lamp string is connected successively; Described point of piezoelectricityRoad is connected with voltage rise and fall detection module and voltage memory module respectively, and described voltage rise and fall detection module dividesBe not connected with voltage memory module and control logic module, described control logic module is connected with voltage memory module; InstituteState high voltage switch circuit and hold and be connected altogether with power supply by inspection leakage resistance, the input termination inspection of described inspection stream comparatorThe points of common connection of leakage resistance and high voltage switch circuit, another input termination reference voltage, described inspection stream comparatorOutput is connected with control logic module;
Described voltage memory module is made up of multiple voltage retainers, the output of each voltage retainer respectively with relativelyDevice group connects;
Described comparator bank is made up of multiple voltage comparators, an input and each of described each voltage comparatorThe output of voltage retainer connects one to one, and is connected institute after another input is connected together with bleeder circuitThe output of stating each voltage comparator is connected with control logic module respectively;
Described control logic module is by multiple d type flip flops and complete the required combined digital logical constitution of function, described controlLogic module processed with the output of the output of each voltage comparator in comparator bank, voltage rise and fall detection module andThe output of inspection stream comparator is as input signal;
Described voltage rise and fall detection module is made up of differentiation element circuit and voltage comparator, output instruction direct current arteries and veinsThe square-wave signal of moving voltage rise and fall state;
Described high voltage switch circuit is made up of multiple high pressure NMOS pipes, the store status of described each d type flip flop and everyThe on off state of individual high pressure NMOS pipe is corresponding one by one; Warp after the source electrode of described each high pressure NMOS pipe is connected togetherCross inspection leakage resistance and hold and be connected altogether with power supply, an input termination inspection leakage resistance and each high pressure of described inspection stream comparatorThe points of common connection of the source electrode of NMOS pipe, another input termination reference voltage; Described each high pressure NMOS pipeDrain electrode connects with LED lamp series winding.
2. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 1, its feature existsIn: described each voltage retainer is made up of electric capacity and operational amplifier.
3. the LED drive circuit based on voltage memory and segmentation current limliting according to claim 1, its feature existsIn: described LED lamp string is composed in series by multiple LED lamp sections, the quantity of described LED lamp section and high pressure NMOS pipeQuantity consistent.
4. the driving method based on LED drive circuit described in claim 3, is characterized in that comprising the following steps:
1) electric main, after rectification circuit rectification, is exported HVDC pulsating volage;
2) the HVDC pulsating volage of bleeder circuit after to rectification circuit rectification carries out dividing potential drop according to a certain percentage, outputLow-voltage direct pulsating volage;
3) voltage rise and fall detection module converts the low-voltage direct pulsating volage after dividing potential drop to be used to indicate low-voltage direct toThe square-wave signal of the uphill process of pulsating volage and decline process;
4) in the uphill process of low-voltage direct pulsating volage, voltage in the time of valley, each high pressure NMOS pipeIn conducting state, now only have the LED lamp section being directly connected with HVDC pulsating volage to be access in effective driving defeatedOutbound port, makes the drive current of this LED lamp section reach cut-off current when voltage rises, and the pressure drop on inspection leakage resistance is higher than ginsengExamine voltage, the output voltage generation overcurrent upset of inspection stream comparator, control logic module detects the upset of this signal,The high pressure NMOS pipe being connected with this LED lamp section negative pole is turned off, next the LED lamp being connected with this LED lamp sectionDuan Yiqi is access in effective driver output port, and the electric current on LED lamp string is got back to below cut-off current, inspection stream comparatorBefore output voltage returns to overcurrent upset occurs; According to this rule, often reach primary current cut-off current just turn-off withThe connected high pressure NMOS pipe of part negative pole being access in LED lamp string, makes to be access in effective driver output portLED lamp hop count amount progressively increases; When all LED lamp Duan Jun are access in, the rising of HVDC pulsating volage againMake electric current reach cut-off current, turn-off all high pressure NMOS pipes in high voltage switch circuit, by institute in LED lamp stringHave the disconnection that is connected of LED lamp section and power supply, the control procedure in the uphill process of this DC pulse moving voltage is called forward controlProcess processed; In forward control procedure, the operating current that voltage memory module is write down LED lamp string successively reaches limit at every turnThe instantaneous voltage of low-voltage direct pulsating volage when flow valuve;
5), in the decline process of low-voltage direct pulsating volage, the magnitude of voltage of voltage memory module memory remains unchanged, defeatedEnter to comparator bank and compare processing, the square wave sequence of comparator bank output has oppositely been reappeared in voltage uphill processWhen LED lamp string reaches Current Limits flow valuve at every turn, each controls node; Control node, the output shape of comparator bank at eachState can change, and control logic module detects this state variation, oppositely progressively recovers each in high voltage switch circuitThe individual conducting state that is turned off high pressure NMOS pipe, realizes the reverse symmetry control to LED lamp string; In reverse symmetryIn the process of controlling, if all high pressure in the peak point place of HVDC pulsating volage high voltage switch circuitNMOS pipe is in off state, declines while controlling node through the 1st at HVDC pulsating volage, and control logicModule makes the high pressure NMOS pipe being finally turned off in forward control procedure recover conducting state, all in LED lamp stringLED lamp section is access in effective driver output port; In the time that HVDC pulsating volage declines through the 2nd control node,Control logic module makes the high pressure NMOS pipe that in forward control procedure, second-to-last is turned off recover conducting state, makesThe LED lamp section that is access in effective driver output port in LED lamp string reduces 1 section; According to this rule, after this high pressureDC pulse moving voltage declines and often controls when node through 1, the conducting that just recovers 1 high pressure NMOS pipe being turned offState, gradually reduces the LED lamp section that is access in effective driver output port in LED lamp string, until all heightPress NMOS pipe all to recover conducting state, in LED lamp string, be access in the number of the LED lamp section of effective driver output portTill amount is 1 section.
5. the driving method of LED drive circuit according to claim 4, is characterized in that: step 3) described inVoltage rise and fall detection module converts the low-voltage direct pulsating volage after dividing potential drop to be used to indicate low-voltage direct pulsation electricity toThe uphill process of pressing and the square-wave signal of decline process are specially:
Voltage rise and fall detection module converts low-voltage direct pulsating volage after dividing potential drop to only have two kinds of level of height toSquare-wave signal, uphill process and the decline of indication low-voltage DC pulse moving voltage respectively of two kinds of varying levels of this square-wave signalProcess, wherein high level instruction uphill process, low level instruction decline process, by this square wave signal inversion can obtain withThe indicating mode that original signal is contrary.
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| TW201212710A (en) * | 2010-05-07 | 2012-03-16 | Cree Inc | AC driven solid state lighting apparatus with LED string including switched segments |
| CN102387639A (en) * | 2011-02-16 | 2012-03-21 | 凹凸电子（武汉）有限公司 | Driving circuit, method and dimming controller for driving light source |
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| CN203748074U (en) * | 2014-03-04 | 2014-07-30 | 华南理工大学 | LED driving circuit based on voltage memorization and subsection current limitation |
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| TW201212710A (en) * | 2010-05-07 | 2012-03-16 | Cree Inc | AC driven solid state lighting apparatus with LED string including switched segments |
| CN102387639A (en) * | 2011-02-16 | 2012-03-21 | 凹凸电子（武汉）有限公司 | Driving circuit, method and dimming controller for driving light source |
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