CN102170727B - Light-emitting diode (LED) dynamic scan driving circuit capable of preventing current from overshooting - Google Patents
Light-emitting diode (LED) dynamic scan driving circuit capable of preventing current from overshooting Download PDFInfo
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- CN102170727B CN102170727B CN2011100425987A CN201110042598A CN102170727B CN 102170727 B CN102170727 B CN 102170727B CN 2011100425987 A CN2011100425987 A CN 2011100425987A CN 201110042598 A CN201110042598 A CN 201110042598A CN 102170727 B CN102170727 B CN 102170727B
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Abstract
The invention discloses a light-emitting diode (LED) dynamic scan driving circuit capable of preventing current from overshooting. The driving circuit provided by the invention comprises an LED load circuit, a constant-current driving output circuit connected with the LED load circuit and an overshooting measurement and a control circuit connected with the constant-current driving output circuit.According to the invention, the overshooting measurement and control circuit is utilized to detect a state of the LED load circuit when the closure of all row selection pipes and the opening of constant-current output channels are carried out simultaneously; the constant-current output channels are closed or enter into a high-resistance conducting state before the row selection pipes are conducted; and the constant-current output channels are turned back to a normal constant-current output state after the row selection pipes are conducted, thus the problem of serious current overshooting occurred when the row selection pipes are changed into the conducting state from the closed state is effectively eliminated, the driving circuit is effectively protected, the display effect of LED dynamicscan driving application is improved, the gradation of grey is greatly enhanced, and the cost and power consumption of LED products are reduced.
Description
Technical field
The invention belongs to technical field of integrated circuits, be specifically related to a kind of light-emitting diode (LED) dynamic scan drive circuit that prevents current over pulse.
Background technology
Show at LED, in the application of backlight, illumination, along with the raising of LED luminous efficiency, and reduce power consumption, the promotion of demand such as reduce cost, the type of drive of LED expands to the dynamic scan type of drive from the static scanning type of drive.So-called static scanning mode refers to drive " point-to-point " of the direct driving LED of constant current output channel of chip and uses, and dynamic scan mode refers to drive chip and cooperates the persistence of vision phenomenon of utilizing human eye to realize every row constant current output channel timesharing driving multiple spot LED of " point is to being listed as " with line control circuit.Dynamic scan commonly used drives has 1/2,1/4,1/8,1/16 to sweep etc. severally, because the dynamic scan type of drive has reduced power consumption, reduced system cost, demand is increasing, uses also more and more wide.
Fig. 1 is LED constant current static scanning drive circuit commonly used, is that constant current drives output circuit in the square frame, and it is by operational amplifier A MP1, either-or switch SW, adjustment pipe M
1, constant current tube M
0With pull down resistor R
0Form; Wherein the positive input of operational amplifier A MP1 receives the reference voltage V that external equipment provides
Ref1, the negative input of operational amplifier A MP1 and adjustment pipe M
1Source electrode d link to each other, the output of operational amplifier A MP1 links to each other with the first input end a of either-or switch SW, the second input c and the pull down resistor R of either-or switch SW
0An end link to each other pull down resistor R
0Hold ground connection in addition, the control end of either-or switch SW receives the control signal LCt that external equipment provides, the output of either-or switch SW with adjust pipe M
1Grid b link to each other, adjust pipe M
1Drain electrode e be the input that constant current drives output circuit, adjust pipe M
1Source electrode d and constant current tube M
0Drain electrode link to each other constant current tube M
0Grid receive the reference voltage V that external equipment provides
Ref2, constant current tube M
0Source ground, adjust pipe M
1With constant current tube M
0Series connection has constituted the constant current output channel, adjusts pipe M
1Switching tube for the constant current output channel.
Constant current drives the external light-emitting diode D of input e of output circuit
0Constitute static application, and pass through V
Ref1And V
Ref2The size of control continuous current, LCt drives the control signal that the constant current output channel opens or closes.
When the LCt signal was high level, switch SW made a link to each other with b, and the constant current output channel is opened, and operational amplifier A MP1 makes constant current tube M
0Drain voltage equals V
Ref1, according to the variation of LED load, in time adjust M simultaneously
1Grid voltage to reduce the LED load variations to constant current tube M
0The interference of drain voltage guarantees that constant current output is stable; When the LCt signal was low level, switch SW linked to each other c with b, adjusted pipe M
1Grid pass through resistance R
0Ground connection is closed the constant current output channel.
The LCt signal transfers high level to from low level, and switch SW is with the output and adjustment pipe M of operational amplifier A MP1
1Grid link to each other, make and adjust pipe M
1Conducting, the voltage on the constant current driving output circuit input e is from being approximately equal to V
LEDDrop to (V
LED-3.4V), 3.4V is the diode forward conducting voltage.Operational amplifier A MP1 regulates M simultaneously
1Grid voltage makes constant current tube M
0Drain voltage equals V
Ref1Thereby, enter normal constant current output state.
Fig. 2 is LED constant current 1/4 dynamic scan drive circuit commonly used, and the constant current in the empty frame 1 drives the identical of output circuit and Fig. 1, the LED load circuit that different only is empty frame 2 is interior.
As row output, the metal-oxide-semiconductor of connecting with LED is as the row selecting switch pipe by a constant current output channel for this dynamic scan drive circuit, and different with the static scanning drive circuit is that a constant current output channel is connected 4 paths of LEDs (D simultaneously
0, D
1, D
2, D
3), every paths of LEDs is respectively by corresponding line EAC (P
0, P
1, P
2, P
3) and power supply V
LEDConnect, each line EAC is selected signal (HCt by the row of correspondence
0, HCt
1, HCt
2, HCt
3) control, row selects the signal low level effective.4 row select signal to have only an effectively timesharing conducting LED at any time at most, and when any one row selects signal invalid from effectively transferring to, next row could transfer to effectively from invalid after selecting signal demand to wait for the time T that holds off interval, in other words, in adjacent two row selected the hold off interval time T of signal between effectively, all line EACs were all ended.
When the LCt signal makes switch SW a is linked to each other with b, and when entering the constant current output state, if HCt
0Effectively then other three row select invalidating signal, the output current light-emitting diode D that then flows through
0, if HCt
1Effectively other three row select invalidating signal, the output current light-emitting diode D that then flows through
1, and the like timesharing light all LED.
In the practical application, in adjacent two row select the hold off interval time T of signal between effectively, namely all line EAC by the time, constant current drives output circuit can be in the constant current output state, i.e. constant current output channel is opened, and the e end is unsettled, but the constant current output channel is in the conducting state no current and flows through, the d point voltage will be reduced to earth potential like this, and the e point voltage also descends simultaneously, adjust pipe M
1Be operated in linear zone.Because a links to each other with b, so manage M with adjustment
1Constitute degenerative operational amplifier A MP1 and will export and increase adjustment pipe M
1Grid voltage, attempt the d node voltage is returned to V
Ref1But because no current in the passage, so adjust pipe M
1Grid voltage can rise to the ceiling voltage that operational amplifier A MP1 can provide always, make and adjust pipe M
1Conducting resistance reach minimum value under this condition.
Adjust pipe M
1Conducting formula at linear zone is as follows:
R
ds＝{β[2(V
gs-V
th)V
ds-V
ds 2]}
-1 (1)
Wherein, R
DsBe conducting resistance, V
GsBe gate source voltage, V
DsBe drain-source voltage, β=μ WC
Ox/ 2L.
The constant current output channel is actual to be a current source, and desirable current source is to adjust pipe M
1Conducting resistance R
DsThe smaller the better.As seen from formula (1), R
DsWith gate source voltage V
GsBe inversely proportional to, therefore take to improve V
GsReduce and adjust pipe M
1Conducting resistance R
DsBe very effective.
But, if R
DsLess, under the opened condition of constant current output channel, row selects the signal time T that holds off interval to finish to have delegation to select signal to change when effectively making corresponding line EAC conducting supply voltage V over to
LEDCan be rapidly be added to constant current by LED and drive output circuit input e and go up and light LED, because it is very little to adjust the conducting resistance of pipe M1, the d point voltage can rise and greater than set point V moment
Ref1, the quick variation of voltage simultaneously can make constant current tube M
0Parasitic capacitance cause constant current tube M
0Gate source voltage moment increase, at constant current tube M
0Gate source voltage and drain-source voltage situation about all significantly increasing under, output current will substantially exceed set point.Certainly meanwhile, operational amplifier A MP1 can make the d point voltage get back to V by the grid voltage of adjusting M1
Ref1, operational amplifier is returned to V with the d point voltage
Ref1And with constant current tube M
0Gate source voltage return to the process need spended time t of normal value, constant current drives the output circuit normal constant current output state of stable realization again when the t time finishes, and therefore the problem that causes the dynamic scan drive circuit to produce the serious overshoot of electric current just occurs in t in the time.
Summary of the invention
The invention provides a kind of light-emitting diode dynamic scan drive circuit that prevents current over pulse; solved the problem of the serious overshoot of electric current that line EAC takes place in the LED load circuit when cut-off state is converted to conducting state; reduce the power consumption of LED product, and protected drive circuit effectively.
The constant current that a kind of light-emitting diode dynamic scan drive circuit that prevents current over pulse comprises the LED load circuit, be connected with the LED load circuit drives output circuit and drives the overshoot telemetry circuit that output circuit is connected with constant current;
Described overshoot telemetry circuit is by first voltage comparator, second voltage comparator and logic control element are formed, the positive input of described first voltage comparator receives the first benchmark voltage that external equipment provides, the negative input of described first voltage comparator links to each other with the output of described LED load circuit, the output of described first voltage comparator links to each other with the first input end of described logic control element, the positive input of described second voltage comparator receives the second benchmark voltage that external equipment provides, the negative input of described second voltage comparator links to each other with the grid that described constant current drives the adjustment pipe in the output circuit, the output of described second voltage comparator links to each other with second input of described logic control element, the 3rd input of described logic control element receives the control signal that enables that described constant current drives constant current output channel that output circuit provides, and the output of described logic control element links to each other with the grid that described constant current drives the impedance Control pipe of constant current output channel in the output circuit.
Operation principle of the present invention is: gather the voltage signal of LED load circuit output and constant current by the overshoot telemetry circuit and drive the gate voltage signal of adjusting pipe in the output circuit and compare with two default benchmark voltage signals respectively, according to comparative result and in conjunction with the operating state of constant current output channel, the impedance Control pipe that constant current is driven constant current output channel in the output circuit applies control, when all line EACs in the LED load circuit are ended, the high resistance conducting state is closed or entered to the constant current output channel that the overshoot telemetry circuit drives in the output circuit constant current, when in the LED load circuit during a certain line EAC conducting, the constant current output channel that the overshoot telemetry circuit in time drives constant current in the output circuit returns to normal constant current output state.
Wherein, logic control element to the standard that signal carries out logic judgement output is: the voltage of (1) LED load circuit output is less than the first benchmark voltage; (2) adjust the grid voltage of pipe greater than the second benchmark voltage; (3) constant current output channel enables control signal makes the constant current output channel be in opening state, when three conditions satisfy simultaneously, logic control element just can be exported and the impedance Control pipe that constant current drives constant current output channel in the output circuit is applied control, makes the constant current output channel close or enter the high resistance conducting state.
In the optimized technical scheme, described logic control element adopts NAND Logic control unit, NOR-logic control unit or RST (modified model trigger) logic control element.
Described NAND Logic control unit is by two input nand gates, three input nand gates, the 4th inverter and the 4th switching tube are formed, the first input end of described two input nand gates is second input of described NAND Logic control unit, second input of described two input nand gates links to each other with the input of the output of described three input nand gates and described the 4th inverter, the output of described two input nand gates links to each other with the first input end of described three input nand gates, second input of described three input nand gates is the first input end of described NAND Logic control unit, the 3rd input of described three input nand gates is the 3rd input of described NAND Logic control unit, the output of described the 4th inverter links to each other with the grid of described the 4th switching tube, the source ground of described the 4th switching tube, the drain electrode of described the 4th switching tube are the output of described NAND Logic control unit.
Described NOR-logic control unit is by two input NOR gate, three input NOR gate, first inverter, second inverter, the 3rd inverter, hex inverter and second cmos transmission gate are formed, the input of described first inverter is the first input end of described NOR-logic control unit, the output of described first inverter links to each other with the first input end of described two input NOR gate, the output of second input of described two input NOR gate and described three input NOR gate, second control end of the input of described hex inverter and described second cmos transmission gate links to each other, the output of described two input NOR gate links to each other with the first input end of described three input NOR gate, second input of described three input NOR gate links to each other with the output of described second inverter, the input of described second inverter is second input of described NOR-logic control unit, the 3rd input of described three input NOR gate links to each other with the output of described the 3rd inverter, the input of described the 3rd inverter is the 3rd input of described NOR-logic control unit, the output of described hex inverter links to each other with first control end of described second cmos transmission gate, the input of described second cmos transmission gate receives the bias voltage that external equipment provides, and the output of described second cmos transmission gate is the output of described NOR-logic control unit.
Described RST logic control element is by the modified model trigger, first cmos transmission gate and the 5th inverter are formed, the first input end of described modified model trigger is the first input end of described RST logic control element, second input of described modified model trigger is second input of described RST logic control element, the reset terminal of described modified model trigger is the 3rd input of described RST logic control element, the output of described modified model trigger links to each other with the input of described the 5th inverter and first control end of described first cmos transmission gate, the output of described the 5th inverter links to each other with second control end of described first cmos transmission gate, the input of described first cmos transmission gate receives the bias voltage that external equipment provides, and the output of described first cmos transmission gate is the output of described RST logic control element.
In the optimized technical scheme, the operating voltage of corresponding described LED load circuit when the described first benchmark voltage drives output circuit permission output minimum current less than described constant current, and greater than zero.
In the optimized technical scheme, the described second benchmark voltage is less than the operating voltage of described LED load circuit, and corresponding described constant current drives the grid voltage of adjusting pipe in the output circuit when driving output circuit and allow the output maximum current greater than described constant current.
In the optimized technical scheme, described bias voltage drives 0.75 times of threshold voltage of the impedance Control pipe of constant current output channel in the output circuit less than described constant current, and more than or equal to zero.
In the optimized technical scheme, described the 4th switching tube is metal-oxide-semiconductor, NPN transistor or PNP transistor.
The present invention is by utilizing the state of all line EACs when taking place simultaneously with the unlatching of constant current output channel in the overshoot telemetry circuit detecting real-time LED load circuit; before the line EAC conducting, make the constant current output channel close or enter the high resistance conducting state; and after the line EAC conducting, in time the constant current output channel is returned to normal constant current output state; eliminated the serious overshooting problem of electric current when line EAC is converted to conducting state from cut-off state effectively; protected drive circuit effectively; improve the LED dynamic scan and driven the display effect of using; promoted tonal gradation greatly; reducing the LED demonstration; raising display quality in the time of product costs such as backlight and illumination; reduce the product power consumption, eliminated the impact of overshoot to the LED power supply; reduced the noise of LED power supply; reduced the performance requirement of LED power supply.
Description of drawings
Fig. 1 is the circuit diagram of LED constant current static scanning drive circuit commonly used.
Fig. 2 is the circuit diagram of LED constant current 1/4 dynamic scan drive circuit commonly used.
Fig. 3 is the circuit diagram of LED dynamic scan drive circuit of the present invention.
Fig. 4 adopts the circuit diagram of the LED constant current 1/4 dynamic scan drive circuit of NAND Logic control unit for the present invention.
Fig. 5 adopts the circuit diagram of the LED constant current 1/4 dynamic scan drive circuit of RST logic control element for the present invention.
Fig. 6 adopts the circuit diagram of the LED constant current 1/4 dynamic scan drive circuit of NOR-logic control unit for the present invention.
Embodiment
In order more specifically to describe the present invention, below in conjunction with the drawings and the specific embodiments technical scheme of the present invention and relative theory are elaborated.
Embodiment 1
As shown in Figure 3 and Figure 4, a kind of light-emitting diode dynamic scan drive circuit that prevents current over pulse comprises LED load circuit 2, the constant current that is connected with LED load circuit 2 drives output circuit 1 and drive the overshoot telemetry circuit 3 that output circuit 1 is connected with constant current.
Constant current drives output circuit 1 by operational amplifier A MP1, either-or switch cell S W, constant current tube M
0, adjust pipe M
1, resistance R 0 forms.
The positive input of operational amplifier A MP1 meets reference voltage V
Ref1, the negative input of operational amplifier A MP1 connects adjusts pipe M
1Source electrode d, the output of operational amplifier A MP1 connects by either-or switch cell S W and adjusts pipe M
1Grid b and realize that degeneration impedance regulates, force constant current tube M
0Drain voltage equal V
Ref1, suppress the variation of LED load circuit output end voltage simultaneously to the influence of output current.Constant current tube M
0Source ground, constant current tube M
0Drain electrode connect and adjust pipe M
1Source electrode d adjusts pipe M
1Drain electrode e connect LED load circuit output, constant current tube M
0Grid connect reference voltage V
Ref2, at V
Ref1And V
Ref2Acting in conjunction under make constant current tube M
0Be constant-current source, adjust pipe M
1With constant current tube M
0Series connection has constituted the constant current output channel, adjusts pipe M
1Impedance Control pipe for the constant current output channel.Resistance R 0 one termination either-or switch cell S W, resistance R 0 other end ground connection, resistance R
0Meet adjustment pipe M by either-or switch cell S W
1Grid b realize to turn-off the function of constant current output channel, the first input end a of either-or switch cell S W connects the output of operational amplifier, the second input c connecting resistance R0 of either-or switch cell S W, the output termination adjustment pipe M of either-or switch cell S W
1Grid b, the constant current output channel that the control end of either-or switch cell S W receives external equipment to be provided enables control signal LCt.When LCt was high level, either-or switch cell S W was with the output and adjustment pipe M of operational amplifier A MP1
1Grid b be connected, the constant current output channel is opened; When LCt was low level, either-or switch cell S W was with resistance R 0 and adjustment pipe M
1Grid b be connected, the constant current output channel is closed, V
Ref1And V
Ref2Setting require to guaranteeing constant current tube M
0Be in normal constant current operating state and export satisfactory constant current.
LED load circuit 2 is by four line EAC P
0, P
1, P
2, P
3With four light-emitting diode D
0, D
1, D
2, D
3Form V
LEDBe the operating voltage of LED load circuit 2, HCt
0, HCt
1, HCt
2, HCt
3Be four capable control signals, four capable control signal any moment at work a capable control signal is all arranged effectively at most or four capable control signals all invalid.
The NAND Logic control unit is by two input nand gate NAND2, three input nand gate NAND3, the 4th inverter INV4 and the 4th switching tube M
4Form, the first input end of two input nand gate NAND2 is second input of NAND Logic control unit, second input of two input nand gate NAND2 links to each other with the input of the output of three input nand gate NAND3 and the 4th inverter INV4, the output of two input nand gate NAND2 links to each other with the first input end of three input nand gate NAND3, second input of three input nand gate NAND3 is the first input end of NAND Logic control unit, the 3rd input of three input nand gate NAND3 is the 3rd input of NAND Logic control unit, the output of the 4th inverter INV4 and the 4th switching tube M
4Grid link to each other the 4th switching tube M
4Source ground, the 4th switching tube M
4Drain electrode be the output of NAND Logic control unit.
The row control signal is that low level is effective in the present embodiment, for high level is invalid, i.e. and line EAC conducting when the row control signal is low level, line EAC is ended during high level.
Enable control signal LCt when being low level when what constant current drove constant current output channel in the output circuit 1, either-or switch cell S W makes output adjust pipe M
1Grid b by resistance R 0 ground connection, the constant current output channel is closed, because LCt low level, three input nand gate NAND3 output in the NAND Logic control unit is set to high level, being output as low level behind the 4th inverter INV4 ends the 4th switching tube M4, cut off the control of 3 pairs of outputs of overshoot telemetry circuit, shown that overshoot telemetry circuit 3 can keep constant current driving output circuit 1 to be previous status when the constant current output channel is closed.
Enable control signal LCt when being high level when what constant current drove constant current output channel in the output circuit 1, either-or switch cell S W makes output adjust pipe M
1Grid b link to each other with operational amplifier A MP1 output, the constant current output channel is opened and controlled by operational amplifier A MP1, when LED load circuit 2 output end voltages changed, operational amplifier A MP1 regulate to adjust pipe M
1Grid voltage keep adjusting pipe M
1Source voltage equal reference voltage V
Ref1
When LCt is high level, the output result of NAND Logic control unit determines that by other two input end signals of NAND Logic control unit i.e. 3 pairs of constant currents of overshoot telemetry circuit drive the b point of output circuit 1 and the testing result of the voltage signal that e is ordered can determine the 4th switching tube M in the overshoot telemetry circuit 3
4Whether conducting is exchanged homogeneous tube M thereby finish
1Control; According to the characteristic of NAND gate as can be known, have only when the output of two voltage comparators is high level, by two input nand gate NAND2, three input nand gate NAND3, the 4th inverter INV4, the 4th switching tube M
4The NAND Logic control unit that constitutes just can be by making the 4th switching tube M
4Conducting will be adjusted pipe M
1Grid b ground connection and it is ended, otherwise the 4th switching tube M
4All the time by and exchange homogeneous tube M
1Nothing influence; In other words, have only the constant current output channel to open under the prerequisite, when the e point voltage less than V
1, the b point voltage is greater than V
2The time, overshoot telemetry circuit 3 just can be had an effect and it is closed the constant current output channel.
In the present embodiment, V
LED=5V, V
1=0.2V, V
2=4.5V, V
Ref1=0.5V, V
Ref2=1.8V.
After the constant current output channel is forced closed, when the line EAC conducting with V
LEDVoltage is delivered to the e end, and overshoot telemetry circuit 3 determines the e point voltage and is higher than V
1, the comparative result of the first voltage comparator COMP1 changes, and makes the 4th switching tube M
4End, the constant current output channel reopens.
Present embodiment passes through the switching tube M in the constant current output channel
1Proved operating state by detecting constant current output channel by making the output resistance of constant current output channel reach maximum mode, when occurring the constant current output channel prior to the line EAC conducting, by earlier the constant current output channel being closed, and the method for in time opening the constant current output channel after the line EAC conducting is got rid of and is subjected to V when the turntable driving of being expert at is used
LEDThe possibility of voltge surge has fundamentally been eliminated line EAC from when conducting is changed, and the constant current output channel is opened caused overshooting problem.
Embodiment 2
As shown in Figure 5, a kind of light-emitting diode dynamic scan drive circuit that prevents current over pulse comprises LED load circuit 2, the constant current that is connected with LED load circuit 2 drives output circuit 1 and drive the overshoot telemetry circuit 3 that output circuit 1 is connected with constant current.
Constant current drives output circuit 1 by operational amplifier A MP1, switching tube M
k, constant current tube M
0, adjust pipe M
1Form with constant current CMOS transmission gate K.
The positive input of operational amplifier A MP1 meets reference voltage V
Ref1, the negative input of operational amplifier A MP1 connects constant current tube M
0Drain electrode, the output termination adjustment pipe M of operational amplifier A MP1
1Grid b and realize that degeneration impedance regulates, force constant current tube M
0Drain voltage equal V
Ref1, suppress the variation of LED load circuit 2 output end voltages simultaneously to the influence of output current, constant current tube M
0Source ground, constant current tube M
0Drain electrode connect and adjust pipe M
1Source electrode d, constant current tube M
0Grid meet reference voltage V
Ref2, at V
Ref1And V
Ref2Acting in conjunction under make constant current tube M
0Be constant-current source, adjust pipe M
1, switching tube M
kWith constant current tube M
0Series connection has constituted constant current output channel, switching tube M
kImpedance Control pipe for the constant current output channel.Switching tube M
kGrid a connects the output of constant current CMOS transmission gate K, and the input termination constant current output channel of constant current CMOS transmission gate K enables control signal LCt, switching tube M
kSource electrode connect and adjust pipe M
1Drain electrode, switching tube M
kDrain electrode e meet LED load circuit 2 outputs, switching tube M
kConducting realizes opening the function of constant current output channel, switching tube M
kBy then closing the constant current output channel.When LCt was high level, the constant current output channel was opened, and when LCt was low level, the constant current output channel was closed, V
Ref1And V
Ref2Setting require to guaranteeing constant current tube M
0Be in normal constant current operating state and export satisfactory constant current.
LED load circuit 2 is by four line EAC P
0, P
1, P
2, P
3With four light-emitting diode D
0, D
1, D
2, D
3Form V
LEDBe the operating voltage of LED load circuit 2, HCt
0, HCt
1, HCt
2, HCt
3Be four capable control signals, four capable control signal any moment at work a capable control signal is all arranged effectively at most or four capable control signals all invalid.
The RST logic control element is by modified model trigger RST, the first cmos transmission gate K
1Form with the 5th inverter INV5, the first input end of modified model trigger RST is the first input end of RST logic control element, second input of modified model trigger RST is second input of RST logic control element, the reset terminal of modified model trigger RST is the 3rd input of RST logic control element, the output of modified model trigger RST and the input of the 5th inverter INV5, the first cmos transmission gate K
1First control end and second control end of constant current CMOS transmission gate K link to each other the output of the 5th inverter INV5 and the first cmos transmission gate K
1Second control end and first control end of constant current CMOS transmission gate K link to each other the first cmos transmission gate K
1Input receive the bias voltage V that external equipment provides
Bias, the first cmos transmission gate K
1Output be the output of RST logic control element.
The row control signal is that low level is effective in the present embodiment, for high level is invalid, i.e. and line EAC conducting when the row control signal is low level, line EAC is ended during high level.
Enable control signal LCt when being low level when what constant current drove constant current output channel in the output circuit 1, the constant current output channel is closed, because LCt low level, modified model trigger RST in the overshoot telemetry circuit 3 is reset, other input end signal of modified model trigger RST is all invalid, modified model trigger RST is output as high level, is output as low level and makes the first cmos transmission gate K behind the 5th inverter INV5
1End, cut off the control of 3 pairs of outputs of overshoot telemetry circuit, show that overshoot telemetry circuit 3 can keep constant current driving output circuit 1 to be previous status when the constant current output channel is closed.
Enable control signal LCt when being high level, switching tube M when what constant current drove constant current output channel in the output circuit 1
kConducting, the constant current output channel is opened, and when LED load circuit 2 output end voltages changed, operational amplifier A MP1 regulated and adjusts pipe M
1Grid voltage force constant current tube M
0Drain voltage equal V
Ref1Thereby, suppress the variation of LED load circuit 2 outputs to the influence of output current.
When LCt is high level, modified model trigger RST output result is determined by other two input signals of modified model trigger RST in the overshoot telemetry circuit 3, and namely overshoot telemetry circuit 3 is according to determining the first cmos transmission gate K to the b point of constant current driving output circuit 1 and the testing result of the voltage signal that e is ordered
1Whether whether conducting is with bias voltage V
BiasBe applied to switching tube M
kGrid a on; Have only the constant current output channel to open under the prerequisite, when the e point voltage less than V
1, the b point voltage is greater than V
2The time, overshoot telemetry circuit 3 just can be had an effect and makes its high-impedance state the constant current output channel.
In the present embodiment, V
LED=5V, V
1=0.2V, V
2=4.5V, V
Ref1=0.5V, V
Ref2=1.8V, V
Bias=0.6V.
After the constant current output channel is forced closed, when the line EAC conducting with V
LEDVoltage is delivered to the e end, and overshoot telemetry circuit 3 determines the e point voltage and is higher than V
1, the comparative result of the first voltage comparator COMP1 changes, and makes the first cmos transmission gate K
1End, the constant current output channel reopens.
The switching tube M of present embodiment by allowing on the constant current output channel
kHigh resistantization has realized the operating state by detecting constant current output channel, when occurring the constant current output channel prior to the line EAC conducting, by making constant current output channel high-impedance state earlier, and the method for in time opening the constant current output channel after the line EAC conducting is got rid of and is subjected to V when the turntable driving of being expert at is used
LEDThe possibility of the impact of voltage has fundamentally been eliminated line EAC from when conducting is changed, and the constant current output channel is opened caused overshooting problem.
As shown in Figure 6, a kind of light-emitting diode dynamic scan drive circuit that prevents current over pulse comprises LED load circuit 2, the constant current that is connected with LED load circuit 2 drives output circuit 1 and drive the overshoot telemetry circuit 3 that output circuit 1 is connected with constant current.
Constant current drives output circuit 1 by operational amplifier A MP1, switching tube M
k, constant current tube M
0, adjust pipe M
1Form with constant current CMOS transmission gate K.
The positive input of operational amplifier A MP1 meets reference voltage V
Ref1, the negative input of operational amplifier A MP1 connects constant current tube M
0Drain electrode, the output termination adjustment pipe M of operational amplifier A MP1
1Grid b and realize that degeneration impedance regulates, force constant current tube M
0Drain voltage equal V
Ref1, suppress the variation of LED load circuit 2 output end voltages simultaneously to the influence of output current, constant current tube M
0Source ground, constant current tube M
0Drain electrode meet switching tube M
kSource electrode d, constant current tube M
0Grid meet reference voltage V
Ref2, at V
Ref1And V
Ref2Acting in conjunction under make constant current tube M
0Be constant-current source, adjust pipe M
1, switching tube M
kWith constant current tube M
0Series connection has constituted constant current output channel, switching tube M
kImpedance Control pipe for the constant current output channel.Switching tube M
kGrid a connects the output of constant current CMOS transmission gate K, and the input termination constant current output channel of constant current CMOS transmission gate K enables control signal LCt, switching tube M
kDrain electrode connect and adjust pipe M
1Source electrode, adjust pipe M
1Drain electrode e meet LED load circuit 2 outputs, switching tube M
kConducting realizes opening the function of constant current output channel, switching tube M
kBy then closing the constant current output channel.When LCt was high level, the constant current output channel was opened, and when LCt was low level, the constant current output channel was closed, V
Ref1And V
Ref2Setting require to guaranteeing constant current tube M
0Be in normal constant current operating state and export satisfactory constant current.
LED load circuit 2 is by four line EAC P
0, P
1, P
2, P
3With four light-emitting diode D
0, D
1, D
2, D
3Form V
LEDBe the operating voltage of LED load circuit 2, HCt
0, HCt
1, HCt
2, HCt
3Be four capable control signals, four capable control signal any moment at work a capable control signal is all arranged effectively at most or four capable control signals all invalid.
The NOR-logic control unit is by two input NOR gate NOR2, three input NOR gate NOR3, the first inverter INV1, the second inverter INV2, the 3rd inverter INV3, hex inverter INV6 and the second cmos transmission gate K
2Form, the input of the first inverter INV1 is the first input end of NOR-logic control unit, the output of the first inverter INV1 links to each other with the first input end of two input NOR gate NOR2, output, the input of hex inverter INV6, the second cmos transmission gate K of second input of two input NOR gate NOR2 and three input NOR gate NOR3
2Second control end and first control end of constant current CMOS transmission gate K link to each other, the output of two input NOR gate NOR2 links to each other with the first input end of three input NOR gate NOR3, second input of three input NOR gate NOR3 links to each other with the output of the second inverter INV2, the input of the second inverter INV2 is second input of NOR-logic control unit, the 3rd input of three input NOR gate NOR3 links to each other with the output of the 3rd inverter INV3, the input of the 3rd inverter INV3 is the 3rd input of NOR-logic control unit, the output of hex inverter INV6 and the second cmos transmission gate K
2First control end and second control end of constant current CMOS transmission gate K link to each other the second cmos transmission gate K
2Input receive the bias voltage V that external equipment provides
Bias, the second cmos transmission gate K
2Output be the output of NOR-logic control unit.
The row control signal is that low level is effective in the present embodiment, for high level is invalid, i.e. and line EAC conducting when the row control signal is low level, line EAC is ended during high level.
Enable control signal LCt when being low level, switching tube M when what constant current drove constant current output channel in the output circuit 1
kEnd, the constant current output channel is closed, because the LCt low level, the output of the NOR-logic control unit in the overshoot telemetry circuit 3 is set to high level, is output as low level and forces the second cmos transmission gate K behind hex inverter INV6
2End, cut off the control of 3 pairs of outputs of overshoot telemetry circuit, show that overshoot telemetry circuit 3 can keep constant current driving output circuit 1 to be previous status when the constant current output channel is closed.
Enable control signal LCt when being high level, switching tube M when what constant current drove constant current output channel in the output circuit 1
kConducting, the constant current output channel is opened, and when LED load circuit 2 output end voltages changed, operational amplifier A MP1 regulated and adjusts pipe M
1Grid voltage force constant current tube M
0Drain voltage equal V
Ref1Thereby, suppress the variation of LED load circuit 2 outputs to the influence of output current.
When LCt is high level, the output result of NOR-logic control unit determines that by other two input signals of NOR-logic control unit i.e. 3 pairs of constant currents of overshoot telemetry circuit drive the b point of output circuit 1 and the voltage signal testing result that e is ordered can determine the second cmos transmission gate K in the overshoot telemetry circuit 3
2Whether whether conducting is with bias voltage V
BiasBe applied to switching tube M
kGrid a on; Have only the constant current output channel to open under the prerequisite, when the e point voltage less than V
1, the b point voltage is greater than V
2The time, overshoot telemetry circuit 3 just can be had an effect and makes its high-impedance state the constant current output channel.
In the present embodiment, V
LED=5V, V
1=0.2V, V
2=4.5V, V
Ref1=0.5V, V
Ref2=1.8V, V
Bias=0.6V.
After the constant current output channel is forced closed, when the line EAC conducting with V
LEDVoltage is delivered to the e end, and overshoot telemetry circuit 3 determines the e point voltage and is higher than V
1, the comparative result of the first voltage comparator COMP1 changes, and makes the second cmos transmission gate K
2End, the constant current output channel reopens.
The switching tube M of present embodiment by allowing on the constant current output channel
kHigh resistantization has realized the operating state by detecting constant current output channel, when occurring the constant current output channel prior to the line EAC conducting, by making constant current output channel high-impedance state earlier, and the method for in time opening the constant current output channel after the line EAC conducting is got rid of and is subjected to V when the turntable driving of being expert at is used
LEDThe possibility of the impact of voltage has fundamentally been eliminated line EAC from when conducting is changed, and the constant current output channel is opened caused overshooting problem.
Claims (9)
1. light-emitting diode dynamic scan drive circuit that prevents current over pulse comprises the LED load circuit and the constant current that is connected with the LED load circuit drives output circuit, it is characterized in that: also comprise with constant current driving the overshoot telemetry circuit that output circuit is connected;
Described overshoot telemetry circuit is by first voltage comparator, second voltage comparator and logic control element are formed, the positive input of described first voltage comparator receives the first benchmark voltage that external equipment provides, the negative input of described first voltage comparator links to each other with the output of described LED load circuit, the output of described first voltage comparator links to each other with the first input end of described logic control element, the positive input of described second voltage comparator receives the second benchmark voltage that external equipment provides, the negative input of described second voltage comparator links to each other with the grid that described constant current drives the adjustment pipe in the output circuit, the output of described second voltage comparator links to each other with second input of described logic control element, the 3rd input of described logic control element receives the control signal that enables that described constant current drives constant current output channel that output circuit provides, and the output of described logic control element links to each other with the grid that described constant current drives the impedance Control pipe of constant current output channel in the output circuit;
Voltage and constant current that described overshoot telemetry circuit is gathered LED load circuit output drive the grid voltage of adjusting pipe in the output circuit, and utilize first voltage comparator and second voltage comparator that above-mentioned two signals that collect are compared with two default benchmark voltage signals respectively; Described logic control element is according to comparative result and in conjunction with the operating state of constant current output channel, the impedance Control pipe that constant current is driven constant current output channel in the output circuit applies control: when all line EACs in the LED load circuit were ended, the high resistant conducting state is closed or entered to the constant current output channel that logic control element drives in the output circuit constant current; When in the LED load circuit during arbitrary line EAC conducting, logic control element returns to normal constant current output state with the constant current output channel that constant current drives in the output circuit;
Wherein, when following three conditions satisfy simultaneously, judge that all line EACs are ended in the LED load circuit, otherwise then showing there is the line EAC conducting in the LED load circuit;
(1) voltage of LED load circuit output is less than the first benchmark voltage; (2) adjust the grid voltage of pipe greater than the second benchmark voltage; The control signal that enables of (3) constant current output channel makes the constant current output channel be in opening state.
2. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 1 is characterized in that: described logic control element employing NAND Logic control unit, NOR-logic control unit or RST logic control element.
3. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 2, it is characterized in that: described NAND Logic control unit is by two input nand gates, three input nand gates, the 4th inverter and the 4th switching tube are formed, the first input end of described two input nand gates is second input of described NAND Logic control unit, second input of described two input nand gates links to each other with the input of the output of described three input nand gates and described the 4th inverter, the output of described two input nand gates links to each other with the first input end of described three input nand gates, second input of described three input nand gates is the first input end of described NAND Logic control unit, the 3rd input of described three input nand gates is the 3rd input of described NAND Logic control unit, the output of described the 4th inverter links to each other with the grid of described the 4th switching tube, the source ground of described the 4th switching tube, the drain electrode of described the 4th switching tube are the output of described NAND Logic control unit.
4. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 2, it is characterized in that: described NOR-logic control unit is by two input NOR gate, three input NOR gate, first inverter, second inverter, the 3rd inverter, hex inverter and second cmos transmission gate are formed, the input of described first inverter is the first input end of described NOR-logic control unit, the output of described first inverter links to each other with the first input end of described two input NOR gate, the output of second input of described two input NOR gate and described three input NOR gate, second control end of the input of described hex inverter and described second cmos transmission gate links to each other, the output of described two input NOR gate links to each other with the first input end of described three input NOR gate, second input of described three input NOR gate links to each other with the output of described second inverter, the input of described second inverter is second input of described NOR-logic control unit, the 3rd input of described three input NOR gate links to each other with the output of described the 3rd inverter, the input of described the 3rd inverter is the 3rd input of described NOR-logic control unit, the output of described hex inverter links to each other with first control end of described second cmos transmission gate, the input of described second cmos transmission gate receives the bias voltage that external equipment provides, and the output of described second cmos transmission gate is the output of described NOR-logic control unit.
5. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 2, it is characterized in that: described RST logic control element is by the modified model trigger, first cmos transmission gate and the 5th inverter are formed, the first input end of described modified model trigger is the first input end of described RST logic control element, second input of described modified model trigger is second input of described RST logic control element, the reset terminal of described modified model trigger is the 3rd input of described RST logic control element, the output of described modified model trigger links to each other with the input of described the 5th inverter and first control end of described first cmos transmission gate, the output of described the 5th inverter links to each other with second control end of described first cmos transmission gate, the input of described first cmos transmission gate receives the bias voltage that external equipment provides, and the output of described first cmos transmission gate is the output of described RST logic control element.
6. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 1, it is characterized in that: the operating voltage of corresponding described LED load circuit when the described first benchmark voltage drives output circuit permission output minimum current less than described constant current, and greater than zero.
7. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 1, it is characterized in that: the described second benchmark voltage is less than the operating voltage of described LED load circuit, and corresponding described constant current drives the grid voltage of adjusting pipe in the output circuit when driving output circuit and allow the output maximum current greater than described constant current.
8. according to claim 4 or the 5 described light-emitting diode dynamic scan drive circuits that prevent current over pulse, it is characterized in that: described bias voltage drives 0.75 times of threshold voltage of the impedance Control pipe of constant current output channel in the output circuit less than described constant current, and more than or equal to zero.
9. the light-emitting diode dynamic scan drive circuit that prevents current over pulse according to claim 3, it is characterized in that: described the 4th switching tube is metal-oxide-semiconductor, NPN transistor or PNP transistor.
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| CN2011100425987A CN102170727B (en) | 2011-02-22 | 2011-02-22 | Light-emitting diode (LED) dynamic scan driving circuit capable of preventing current from overshooting |
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| EP2590479A1 (en) * | 2011-11-04 | 2013-05-08 | Toshiba Lighting & Technology Corporation | Power supply for lighting and luminaire |
| CN104010404B (en) * | 2013-02-22 | 2016-09-28 | 普诚科技股份有限公司 | Light emitting diode drive device |
| US9236014B2 (en) | 2013-05-08 | 2016-01-12 | Shenzhen China Star Optoelectronics Technology Co., Ltd | LED backlight driving circuit, LCD device, and method for driving the LED backlight driving circuit |
| CN103295536B (en) * | 2013-05-08 | 2015-09-09 | 深圳市华星光电技术有限公司 | A kind of LED backlight drive circuit, liquid crystal indicator and a kind of driving method |
| CN105021912B (en) * | 2014-04-29 | 2018-04-13 | 全汉企业股份有限公司 | Load circuit and load device for LED driver burn-in test |
| CN104238614A (en) * | 2014-09-03 | 2014-12-24 | 李倩 | Reference voltage circuit |
| US10420178B2 (en) | 2017-03-14 | 2019-09-17 | Infineon Technologies Ag | Light emitting diode driver for load and supply changes |
| CN109859681B (en) * | 2019-03-28 | 2024-06-11 | 北京集创北方科技股份有限公司 | LED display driving circuit, display, driving method and driving chip |
| CN110996425B (en) * | 2019-11-26 | 2022-07-12 | 深圳创维－Rgb电子有限公司 | Light bar overshoot protection circuit and backlight module |
| CN112821198B (en) * | 2020-12-30 | 2022-08-30 | 中国电子科技集团公司第十三研究所 | N-surface-separated reverse-order-structure laser chip and preparation method thereof |
| CN113015289B (en) * | 2021-03-15 | 2022-01-28 | 无锡英迪芯微电子科技股份有限公司 | LED constant current drive circuit with low power consumption |
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| CN101340755A (en) * | 2008-08-12 | 2009-01-07 | 深圳市联德合微电子有限公司 | High-speed driving circuit of LED capable of overshooting prevention |
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