CN105517250B - A kind of LED constant current drive system and its constant-current control circuit - Google Patents
A kind of LED constant current drive system and its constant-current control circuit Download PDFInfo
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- CN105517250B CN105517250B CN201610036438.4A CN201610036438A CN105517250B CN 105517250 B CN105517250 B CN 105517250B CN 201610036438 A CN201610036438 A CN 201610036438A CN 105517250 B CN105517250 B CN 105517250B
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Abstract
The invention discloses a kind of LED constant current drive system and its constant-current control circuit, constant-current control circuit includes voltage loop and current loop.The present invention is when simulating dimmer voltage signal more than first threshold voltage, and the dutycycle of the square-wave signal of output is adjusted by voltage loop makes the constant current hold of load；When simulating dimmer voltage signal less than first threshold voltage, the pulse frequency of the square-wave signal of output is adjusted by voltage loop makes the constant current hold of load；Double mode auto-changeover control is realized, in normal working conditions, mode of operation is pulse width modulation；Under low-load condition of work, mode of operation automatically switches to pulse frequency modulated, effectively raises the overall operating efficiency of system.The present invention is also by current loop, and according to simulation dimmer voltage signal and load sample rate current, the electric current of adjustment load makes its holding constant；Improve response speed；Two loops are controlled simultaneously, improve control accuracy, response speed and the stability of a system.
Description
Technical field
Field, more particularly to a kind of LED constant current drive system and its current constant control electricity are driven the present invention relates to LED constant current
Road.
Background technology
In modern society, the subject matter that the energy is faced with environmental protection as the mankind.LED due to its efficiently, low consumption, environmental protection,
The advantages of small volume, long lifespan, is increasingly subject to pay attention in lighting field.Limited by its optics, electrology characteristic, LED has to be aided with
Special constant-current drive circuit just can normal work, therefore LED drive system importance is self-evident.
In IC system, the work side that existing LED drive system majority is controlled using PWM mode univoltage loop
Formula, loop generally includes current sample-feedback-part of control circuit three, and usual operating frequency constant is same by sampled signal
Fixed voltage relatively controls change in duty cycle, and then controls the process of output voltage change, and the control to load current is main
By the control completion to output voltage.The major defect of such invention is as follows：One is that control loop is single, from current sample to
Feedback control need to pass fully through system fading margin process, and response speed is partially slow, be vulnerable to the environment such as process deviation, temperature, humidity because
Element influence, causes control accuracy to reduce；Two are a lack of effective control to system effectiveness, and PWM determines the mode of operation of frequency, low negative
Efficiency reduction is difficult to avoid that in the case of load；Three be that the flexibility that system is applied is poor, can only be using customization to peripheral driver majority
Performance and cost are often difficult to take into account in mode, practical application.
Therefore, existing technology could be improved and improve.
The content of the invention
In view of in place of above-mentioned the deficiencies in the prior art, it is an object of the invention to provide a kind of LED constant current drive system and
Its constant-current control circuit, is controlled using voltage and current double loop, improves control accuracy and response speed.
In order to achieve the above object, this invention takes following technical scheme：
A kind of constant-current control circuit of LED constant current drive system, including：
Voltage loop, for when simulating dimmer voltage signal more than first threshold voltage, passing through the square wave for adjusting output
The dutycycle of signal come control load voltage, make the constant current hold of load；It is less than first in simulation dimmer voltage signal
During threshold voltage, the voltage of load is controlled by adjusting the pulse frequency of the square-wave signal exported, the electric current of load is kept
It is constant；
Current loop, for according to simulation dimmer voltage signal and load sample rate current, adjusting the electric current of load, making load
Constant current hold.
In the constant-current control circuit of described LED constant current drive system, the voltage loop includes：
PWM/PFM automatically selects module, for when simulating dimmer voltage signal more than first threshold voltage, output to be fixed frequently
Sawtooth signal；When simulating dimmer voltage signal less than first threshold voltage, output frequency is according to simulation dimmer voltage signal
Change and the sawtooth signal that changes；
Slope compensation module, for the inductive current sampled signal and PWM/PFM of LED constant current drive system to be automatically selected
The sawtooth signal of module output is overlapped；
Error amplification module, for entering to simulation dimmer voltage signal sampled voltage signal corresponding with load sample rate current
Row application condition, produces the voltage signal of dynamic change and exports to comparison module；
Comparison module, the signal of voltage signal and slope compensation the module output for error amplification module to be exported is carried out
Compare, the variable square-wave signal of output duty cycle come control load voltage, make the constant current hold of load.
In the constant-current control circuit of described LED constant current drive system, the current loop includes:
First voltage multiplies module again, for simulation dimmer voltage signal to be amplified by predetermined multiplying power, and by after amplification
Simulation dimmer voltage signal output give spaning waveguide operational amplifier module；
Second voltage multiplies module again, is put for will load the corresponding sampled voltage signal of sample rate current by predetermined multiplying power
Greatly, and by the sampled voltage signal output after amplification spaning waveguide operational amplifier module is given；
Spaning waveguide operational amplifier module, for comparing the simulation dimmer voltage signal after amplification and the sampled voltage signal after amplification,
And adjust the electric current of load in real time according to comparative result, make the constant current hold of load.
In the constant-current control circuit of described LED constant current drive system, the voltage loop also includes drive module, described
Drive module is used to carry out tandem type amplification to the square-wave signal that comparison module is exported, and the band for increasing the square-wave signal carries energy
Power.
In the constant-current control circuit of described LED constant current drive system, the PWM/PFM, which automatically selects module, to be included：
Voltage selecting unit, for when simulating dimmer voltage signal more than first threshold voltage, output first threshold to be electric
Pressure；When simulation dimmer voltage signal is more than second threshold voltage and is less than first threshold voltage, output simulation dimmer voltage is believed
Number；When simulating dimmer voltage signal less than second threshold voltage, second threshold voltage is exported；
Sawtooth waveforms generation unit, for when voltage selecting unit exports first threshold voltage, output to be electric with first threshold
Pressure is corresponding to determine frequency sawtooth signal；In voltage selecting unit output simulation dimmer voltage signal, output frequency is according to simulation
The change of dimmer voltage signal and the sawtooth signal changed；Voltage selecting unit export second threshold voltage when, output with
Second threshold voltage is corresponding to determine frequency sawtooth signal.
In the constant-current control circuit of described LED constant current drive system, the sawtooth waveforms generation unit includes：
Low pressure difference linear voltage regulator subelement, the voltage signal for being exported to voltage selecting unit carries out voltage stabilizing；
Electric current automatic biasing subelement, the voltage signal for low pressure difference linear voltage regulator subelement to be exported is changed into and it
The current signal being directly proportional, carries out mirror image to the current signal, obtains image current；
FREQUENCY CONTROL subelement, for when the voltage of built-in charge and discharge capacitance is less than the bottom threshold of built-in oscillator,
Charged by image current to charge and discharge capacitance；When the voltage of charge and discharge capacitance exceedes the upper threshold of oscillator, oscillator
Give charge and discharge capacitance electric discharge；The voltage of the charge and discharge capacitance is the output voltage of FREQUENCY CONTROL subelement.
In the constant-current control circuit of described LED constant current drive system, the sawtooth waveforms generation unit also includes locking
Unit, the locking subelement is used to, when the voltage signal that voltage selecting unit is exported is less than lock threshold voltage, close low
Pressure difference linear voltage regulator subelement；The lock threshold voltage is less than second threshold voltage.
In the constant-current control circuit of described LED constant current drive system, the voltage selecting unit include first comparator,
Second comparator, the first NOT gate, the second NOT gate, the 3rd NOT gate, the 4th NOT gate, the 5th NOT gate, the first NAND gate, the first transmission
Door, the second transmission gate and the 3rd transmission gate；The simulation dimmer voltage signal provides the anti-phase input that end connects first comparator
The input at end, the inverting input of the second comparator and the second transmission gate；The normal phase input end input of the first comparator
First threshold voltage, the normal phase input end input second threshold voltage of second comparator；The output of the first comparator
The input of the first NOT gate of end connection, the output end of first NOT gate connects the input and the first transmission gate of the second NOT gate
Control end, the input input first threshold voltage of first transmission gate；Second NOT gate output end connection first with
The first input end of NOT gate；The output end of second comparator connects the input of the 3rd NOT gate, the 3rd NOT gate it is defeated
Go out the input of the 4th NOT gate of end connection and the second input of the first NAND gate；The output end connection the 3rd of 4th NOT gate
The control end of transmission gate, the input input second threshold voltage of the 3rd transmission gate；The output end of first NAND gate
The input of the 5th NOT gate is connected, the output end of the 5th NOT gate connects the control end of the second transmission gate, second transmission
The output end of door for voltage selecting unit output end, connect the output end of the first transmission gate, the output end of the 3rd transmission gate and
The input of sawtooth waveforms generation unit.
In the constant-current control circuit of described LED constant current drive system, the low pressure difference linear voltage regulator subelement includes
First operational amplifier, the first metal-oxide-semiconductor, first resistor, second resistance；The normal phase input end of first operational amplifier is low
The input of pressure difference linear voltage regulator subelement, the output end for connecting voltage selecting unit；First operational amplifier it is defeated
Go out the grid of the first metal-oxide-semiconductor of end connection, the drain electrode of first metal-oxide-semiconductor is the output end of low pressure difference linear voltage regulator subelement,
The source electrode of first metal-oxide-semiconductor connects one end and the first operational amplifier inverting input of second resistance by first resistor,
The other end ground connection of the second resistance.
A kind of LED constant current drive system, including constant-current control circuit as described above.
A kind of LED constant current drive system and its constant-current control circuit provided compared to prior art, the present invention, the perseverance
Flow control circuit includes voltage loop and current loop.The present invention simulate dimmer voltage signal be more than first threshold voltage when,
Adjust the dutycycle of the square-wave signal exported to control the voltage of load by voltage loop, make the constant current hold of load；
When simulating dimmer voltage signal less than first threshold voltage, pass through the pulse frequency that voltage loop adjusts the square-wave signal of output
To control the voltage of load, make the constant current hold of load；Double mode auto-changeover control is realized, in normal running conditions
Under, mode of operation is PWM（Pulse width modulation）；Under low-load condition of work, mode of operation automatically switches to PFM（Pulse frequency
Rate is modulated）, effectively raise the overall operating efficiency of system.The present invention is also by current loop, according to simulation dimmer voltage
Signal and load sample rate current, adjust the electric current of load, make the constant current hold of load；Greatly improve response speed；Two
Individual loop is controlled simultaneously, improves control accuracy, response speed and the stability of a system.
Brief description of the drawings
The structured flowchart of the constant-current control circuit for the LED constant current drive system that Fig. 1 provides for the present invention；
In the constant-current control circuit for the LED constant current drive system that Fig. 2 provides for the present invention, PWM/PFM automatically selects module
Structured flowchart；
In the constant-current control circuit for the LED constant current drive system that Fig. 3 provides for the present invention, the circuit of voltage selecting unit
Figure；
In the constant-current control circuit for the LED constant current drive system that Fig. 4 provides for the present invention, the circuit of sawtooth waveforms generation unit
Figure；
In the constant-current control circuit for the LED constant current drive system that Fig. 5 provides for the present invention, the circuit of slope compensation module
Figure；
In the constant-current control circuit for the LED constant current drive system that Fig. 6 provides for the present invention, the circuit diagram of current loop；
The circuit diagram of the first embodiment for the LED constant current drive system that Fig. 7 provides for the present invention；
The circuit diagram of the second embodiment for the LED constant current drive system that Fig. 8 provides for the present invention.
Embodiment
The present invention provides a kind of LED constant current drive system and its constant-current control circuit.To make the purpose of the present invention, technical side
Case and effect are clearer, clear and definite, and the present invention is described in more detail for the embodiment that develops simultaneously referring to the drawings.It should be appreciated that
Specific embodiment described herein only to explain the present invention, is not intended to limit the present invention.
Referring to Fig. 1, the constant-current control circuit for the LED constant current drive system that the present invention is provided, including the He of voltage loop 10
Current loop 20.
The voltage loop 10, for when simulating dimmer voltage signal Vadim more than first threshold voltage VH, passing through and adjusting
Save the dutycycle of the square-wave signal exported to control the voltage of load 30, make the constant current hold of load 30；In simulation light modulation
When voltage signal is less than first threshold voltage VH, the electricity of load 30 is controlled by adjusting the pulse frequency of the square-wave signal exported
Pressure, makes the constant current hold of load 30.The feedback of voltage loop 10 of the present invention is defeated to system using peak-current mode work
Go out voltage effectively to be adjusted；Double mode auto-changeover control can be realized simultaneously, and in normal working conditions, mode of operation is
PWM（Pulse width modulation）；Under low-load condition of work（Less than the first precognition threshold voltage）, mode of operation automatically switches to
PFM（Pulse frequency modulated）；It ensure that system steady operation.Different mode of operations are automatically selected according to load difference, effectively
The overall operating efficiency of raising system.
The current loop 20, for according to simulation dimmer voltage signal and load sample rate current, the electricity of adjustment load 30
Stream, makes the constant current hold of load 30.The current constant control part of current loop 20 can dynamically be adjusted in real time for load current change
It is whole, greatly improve response speed.
The load 30 is preferably LED string.
It follows that two loops are controlled simultaneously, control accuracy, response speed and the stability of a system are greatly improved,
It is better than general LED control system.
Further, the voltage loop 10 automatically selects module 110, slope compensation module 120 including PWM/PFM, missed
Poor amplification module 130, comparison module 140 and drive module 150.
The PWM/PFM automatically selects module 110, for being more than first threshold electricity in simulation dimmer voltage signal Vadim
When pressing VH, frequency sawtooth signal is determined in output；When simulating dimmer voltage signal Vadim less than first threshold voltage VH, output frequency
The sawtooth signal that rate changes according to simulation dimmer voltage signal Vadim change.In other words, the PWM/PFM is automatic
Selecting module 110, according to simulation dimmer voltage signal Vadim size, automatically selects mode of operation, under PWM mode of operations
Frequency sawtooth signal is determined in output, exports the sawtooth signal of respective frequencies according to first threshold voltage VH under PFM mode of operations.
The slope compensation module 120, for by the inductive current sampled signal and PWM/PFM of LED constant current drive system
The sawtooth signal for automatically selecting the output of module 110 is overlapped.
The error amplification module 130, for simulation dimmer voltage signal Vadim and loading that sample rate current is corresponding adopts
Sample voltage signal carries out application condition, produces the voltage signal of dynamic change and exports to comparison module 140.Specifically, described
Error amplification module 130 includes a high precision operating amplifier, and the positive terminal input of the high precision operating amplifier is defeated
Enter to simulate dimmer voltage signal Vadim, the corresponding sampled voltage signal of inverting input input load sample rate current, when anti-phase defeated
The sampled voltage signal for entering end input reaches the voltage of normal phase input end input（Vadim）When, now system is in stablizes relatively
State, the output end of the high precision operating amplifier exports a metastable voltage signal；This output voltage signal by
The sampled voltage sampled signal influence of inverting input input, any small dynamic change of inverting input all will directly reflect
For the dynamic change of output end voltage signal；In other words, any small dynamic change of load current all will directly reflect
For the dynamic change of output end voltage signal.
The comparison module 140, for the voltage signal and slope compensation module 120 for exporting error amplification module 130
The signal of output is compared, the variable square-wave signal of output duty cycle come control load 30 voltage, make the electric current of load 30
Keep constant.The sawtooth signal of the output of first input end input slope compensation module 120 of the comparison module 140；It is described
The voltage signal of the second input error originated from input amplification module 130 output of comparison module 140（Such as the description of the preceding paragraph, this letter
It can change during number stable state with load and have small dynamic change）, the signal of two input inputs is compared, output duty cycle
Variable square-wave signal（Because sawtooth signal is constant, the other end has small dynamic change, therefore dutycycle can also have and follow
Change）, then output voltage is raised for dutycycle increase, and dutycycle, which reduces then output voltage, to be reduced.
The drive module 150, the square-wave signal for being exported to comparison module 140 carries out tandem type amplification, increases institute
State the load capacity of square-wave signal.
The input and error that the simulation dimmer voltage signal offer end connection PWM/PFM automatically selects module 110 are put
The first input end of big module 130, the PWM/PFM automatically selects the output end connection slope compensation module 120 of module 110
First input end, one end of the inductance of the second input connection LED constant current drive system of the slope compensation module 120；Institute
State slope compensation module 120 output end connect comparison module 140 first input end, the error amplification module 130 it is defeated
Go out the second input of end connection comparison module 140, the output end of the comparison module 140 connects negative by drive module 150
Carry 30.
After load feedback signal is adjusted through this voltage loop, the sawtooth signal of fixed frequency is contrasted, duty is produced in real time
Than the square wave of change, driving tube on off state is controlled using switching signal change in duty cycle, so as to change output voltage to influence
Load, reaches the purpose of system feedback regulation.
The current loop 20 multiplies module 210, second voltage including first voltage and multiplies module 220 and spaning waveguide operational amplifier mould again again
Block 230.
The first voltage multiplies module 210 again, for simulation dimmer voltage signal Vadim to be put by predetermined multiplying power
Greatly, and by the simulation dimmer voltage signal output after amplification to spaning waveguide operational amplifier module 230.
The second voltage multiplies module 220 again, for that will load the corresponding sampled voltage signal of sample rate current by predetermined times
Rate is amplified, and by the sampled voltage signal output after amplification to spaning waveguide operational amplifier module 230；That is, described second voltage multiplies again
The peak point current of 220 pairs of loads 30 of module is sampled, and load sample rate current is converted into corresponding sampled voltage signal, will
Sampled voltage signal is amplified by predetermined multiplying power.
The spaning waveguide operational amplifier module 230, for comparing the sampling electricity after the simulation dimmer voltage signal after amplification and amplification
Signal is pressed, the electric current of adjustment load in real time makes the constant current hold of load.That is, to the simulation dimmer voltage signal after amplification
High-precision comparison is carried out with the sampled voltage signal after amplification, and adjusts the electric current of external loading 30 immediately.By to signal
Cascaded amplification, greatly improves the precision and response speed of current constant control.
The first voltage multiplies the first input end of the output end connection spaning waveguide operational amplifier module 230 of module 210 again, and described the
Two voltages multiply the second input of the connection spaning waveguide operational amplifier of module 220 module 230 again.
Further, referring to Fig. 2, the PWM/PFM, which automatically selects mould 110, specifically includes voltage selecting unit and sawtooth
Ripple generation unit.
The voltage selecting unit 111, for being more than first threshold voltage VH in simulation dimmer voltage signal Vadim
（Vadim ＞ VH）When, export first threshold voltage VH；Simulation dimmer voltage signal Vadim be more than second threshold voltage VL and
Less than first threshold voltage VH（VH ＞ Vadim ＞ VL）When, output simulation dimmer voltage signal Vadim；In simulation dimmer voltage
Signal Vadim is less than second threshold voltage VL（Vadim ＜ VL）When, export second threshold voltage VL.The first threshold voltage
VH is more than second threshold voltage VL.
The sawtooth waveforms generation unit 112, for when voltage selecting unit 111 exports first threshold voltage VH, exporting
It is corresponding with first threshold voltage VH to determine frequency sawtooth signal；In voltage selecting unit output simulation dimmer voltage signal Vadim
When, the sawtooth signal that output frequency changes according to the change of simulation dimmer voltage signal；In voltage selecting unit output the
During two threshold voltage VL, output is corresponding with second threshold voltage VL to determine frequency sawtooth signal.
The input connection simulation dimmer voltage signal of the voltage selecting unit 111 provides end, and the voltage selection is single
The input of the output end connection sawtooth waveforms generation unit 112 of member 111, the output end connection of the sawtooth waveforms generation unit 112
Slope compensation module 120.
It follows that passing through voltage selecting unit and sawtooth waveforms generation unit so that in normal working conditions（Vadim
＞ VH）, constant-current control circuit mode of operation is PWM（Pulse width modulation）；Under low-load condition of work（VH ＞ Vadim ＞
VL）, mode of operation automatically switches to PFM（Pulse frequency modulated）；Under too low load operating condition（Vadim ＜ VL）, then switch
Return PWM mode, it is ensured that system steady operation.
The sawtooth waveforms generation unit 112 includes low pressure difference linear voltage regulator subelement 1121, locking subelement 1122, electricity
Flow automatic biasing subelement 1123 and FREQUENCY CONTROL subelement 1124.
The low pressure difference linear voltage regulator subelement 1121, for entering to the voltage signal that voltage selecting unit 111 is exported
Row voltage stabilizing.
The locking subelement 1122, the voltage signal for being exported in voltage selecting unit 111 is less than lock threshold electricity
When pressing VP, low pressure difference linear voltage regulator subelement 1121 is closed, i.e. disconnect low pressure difference linear voltage regulator subelement 1121 and electric current
Electrical connection between automatic biasing subelement 1123, now system be in the lock state, power consumption goes to zero.The lock threshold voltage
VP is less than second threshold voltage VL, it is preferred that the lock threshold voltage VP is much smaller than second threshold voltage VL（VP《VL）.
The electric current automatic biasing subelement 1123, the voltage for low pressure difference linear voltage regulator subelement 1121 to be exported is believed
Number the current signal being proportional is changed into, mirror image is carried out to the current signal, image current is obtained.
The FREQUENCY CONTROL subelement 1124, the threshold value for being less than built-in oscillator in the voltage of built-in charge and discharge capacitance
During lower limit, charged by image current Icharge to charge and discharge capacitance；Exceed the threshold value of oscillator in the voltage of charge and discharge capacitance
During the upper limit, oscillator discharges to charge and discharge capacitance；The voltage of the charge and discharge capacitance is the output voltage of FREQUENCY CONTROL subelement.
The input of the low pressure difference linear voltage regulator subelement 1121 is the input of sawtooth waveforms generation unit 112, connected
The output end of voltage selecting unit 111 is connect, the output end of the low pressure difference linear voltage regulator subelement 1121 passes sequentially through locking
Subelement 1122, the rate of connections of electric current automatic biasing subelement 1123 control the input of subelement 1124, the frequency control word
Output end, connection slope compensation module 120 of the output end of unit 1124 for the sawtooth waveforms generation unit 112.
Referring to Fig. 3, the voltage selecting unit 111 includes first comparator OP1, the second comparator OP2, the first NOT gate
Q1, the second NOT gate Q2, the 3rd NOT gate Q3, the 4th NOT gate Q4, the 5th NOT gate Q6, the first NAND gate Q5, the first transmission gate TG1,
Two transmission gate TG2 and the 3rd transmission gate TG3；The first comparator OP1 and the second comparator OP2 are powered by feeder ear VCC.Institute
State inverting input, the second comparator OP2 anti-phase input that simulation dimmer voltage signal provides end connection first comparator OP1
End and the second transmission gate TG2 input；The normal phase input end input first threshold voltage of the first comparator OP1, it is described
Second comparator OP2 normal phase input end input second threshold voltage；The output end connection first of the first comparator OP1 is non-
Door Q1 input, the output end of the first NOT gate Q1 connects the control of the second NOT gate Q2 input and the first transmission gate TG1
End processed, the input input first threshold voltage of the first transmission gate TG1；The output end connection first of the second NOT gate Q2
NAND gate Q5 first input end；The output end of the second comparator OP2 connects the 3rd NOT gate Q3 input, the described 3rd
NOT gate Q3 output end connects the 4th NOT gate Q4 input and the first NAND gate Q5 the second input；The 4th NOT gate Q4
Output end connect the 3rd transmission gate TG3 control end, the 3rd transmission gate TG3 input input second threshold voltage；
The output end of the first NAND gate Q5 connects the 5th NOT gate Q6 input, the output end connection second of the 5th NOT gate Q6
Transmission gate TG2 control end, the output end of the second transmission gate TG2 is the output end of voltage selecting unit, the biography of connection first
The input of defeated door TG1 output end, the 3rd transmission gate TG3 output end and sawtooth waveforms generation unit.
The first transmission gate TG1, the second transmission gate TG2 and the 3rd transmission gate TG3 clock signal high level are effective, i.e.
High level is turned on.
Please continue to refer to Fig. 3, solid arrow represents the direction of control source/output in Fig. 3.Work as Vadim>During VH, second
The transmission gate TG2 transmission gate TG3 of control end 2 and the 3rd control end 3 is low level, and the first transmission gate TG1 control end 1 is height
Level, then the second transmission gate TG2 closings, the 3rd transmission gate TG3 is closed, and the first transmission gate TG1 conductings, first threshold voltage VH leads to
Cross the first transmission gate TG1 to transmit to the output end of voltage selecting unit 111, VS is the electricity of the output end of voltage selecting unit 111
Pressure.Work as VH>Vadim>During VL, the first transmission gate TG1 transmission gate TG3 of control end 1 and the 3rd control end 3 is low level, the
Two transmission gate TG2 control end 2 is high level, then the first transmission gate TG1 is closed, and the 3rd transmission gate TG3 is closed, the second transmission gate
TG2 is turned on, and simulation dimmer voltage signal Vadim is transmitted to the output end of voltage selecting unit 111 by the second transmission gate TG2.
Work as Vadim<During VL, the first transmission gate TG1 transmission gate TG2 of control end 1 and second control end 2 is low level, the 3rd transmission
Door TG3 control end 3 is high level, then the first transmission gate TG1 is closed, and the second transmission gate TG2 is closed, and the 3rd transmission gate TG3 is led
Logical, second threshold voltage VL is transmitted to the output end of voltage selecting unit 111 by the 3rd transmission gate TG3.It is as shown in table 1 below,
The major function of the voltage selecting unit 111 is to automatically select suitable output voltage VS according to Vadim input range；
| Vadim | Vadim>VH | VH>Vadim>VL | Vadim<VL |
| VS | VH | Vadim | VL |
Table 1：Simulate dimmer voltage signal Vadim and the voltage VS of the output end of voltage selecting unit 111 corresponding relation.
Referring to Fig. 4, the low pressure difference linear voltage regulator subelement 1121 includes the first operational amplifier OP3, the first MOS
Pipe M1, first resistor R1, second resistance R2；The normal phase input end of the first operational amplifier OP3 is low pressure difference linearity voltage stabilizing
The input of device subelement, the output end for connecting voltage selecting unit；The output end connection the of the first operational amplifier OP3
One metal-oxide-semiconductor M1 grid, the drain electrode of the first metal-oxide-semiconductor M1 for low pressure difference linear voltage regulator subelement output end, described the
The one end and the first operational amplifier OP3 anti-phase inputs of one metal-oxide-semiconductor M1 source electrode by first resistor R1 connection second resistances R2
End, the other end ground connection of the second resistance R2.The first metal-oxide-semiconductor M1 is NMOS tube.First operational amplifier OP3, first
Metal-oxide-semiconductor M1, first resistor R1, second resistance R2 composition classics LDO structures, then second resistance R2 electric current can be expressed as IR2=
VS/R2.Therefore flow through electric current Iadim=IR2=VS/R2 on the second metal-oxide-semiconductor M2, the 3rd metal-oxide-semiconductor M3 and the first metal-oxide-semiconductor M1.
The locking subelement 1122 includes the 3rd comparator OP4 and the 4th transmission gate TG4；The 3rd comparator OP4
Normal phase input end input lock threshold voltage VP, the 3rd comparator OP4 inverting input connect the first operation amplifier
Device OP3 inverting input, the voltage of the first operational amplifier OP3 inverting inputs exports for voltage selecting unit 111
The voltage VS's at end follows voltage VSF, and principle, VS=VSF are followed according to LDO.The output end connection of the 3rd comparator OP4
4th transmission gate TG4 control end Vlock, the 4th transmission gate TG4 input for locking subelement 1122 input,
The first metal-oxide-semiconductor M1 drain electrode is connected, the output end of the 4th transmission gate TG4 is the output end of locking subelement 1122, connection
The input of electric current automatic biasing subelement 1123.
Under normal operating conditions, VSF>VP, now Vlock is high level, the 4th transmission gate TG4 conductings, Iadim=VS/
R2, system worked well；Work as VSF<During VP, now Vlock is low level, and the 4th transmission gate TG4 is closed, Iadim=0,
Icharge=0, system is in the lock state.Now power consumption goes to zero, in holding state.
The electric current automatic biasing subelement 1123 includes the second metal-oxide-semiconductor M2, the 3rd metal-oxide-semiconductor M3, the 4th metal-oxide-semiconductor M4, the 5th
Metal-oxide-semiconductor M5, the 6th metal-oxide-semiconductor M6, the 7th metal-oxide-semiconductor M7, the 8th metal-oxide-semiconductor M8, the 9th metal-oxide-semiconductor M9 and the tenth metal-oxide-semiconductor M10.Described
Two metal-oxide-semiconductor M2 drain electrode is the input of electric current automatic biasing subelement 1123, the 4th transmission gate TG4 of connection output end, the 3rd
The grid of metal-oxide-semiconductor M3 grid and the 4th metal-oxide-semiconductor M4；The grid of the second metal-oxide-semiconductor M2 connect the 5th metal-oxide-semiconductor M5 grid and
6th metal-oxide-semiconductor M6 grid；The source electrode of the second metal-oxide-semiconductor M2 connects the 3rd metal-oxide-semiconductor M3 drain electrode, the 3rd metal-oxide-semiconductor M3
Source electrode connect the 4th metal-oxide-semiconductor M4 source electrode, the 6th metal-oxide-semiconductor M6 source electrode and feeder ear VCC, the source of the 6th metal-oxide-semiconductor M6
Extremely the output end of electric current automatic biasing subelement 1123, rate of connections control the input of subelement 1124；4th metal-oxide-semiconductor
M4 the 5th metal-oxide-semiconductor M5 of drain electrode connection source electrode, the 7th metal-oxide-semiconductor M7 of drain electrode connection of the 5th metal-oxide-semiconductor M5 drain electrode, the 7th
The grid of metal-oxide-semiconductor M7 grid and the 8th metal-oxide-semiconductor M8；The 6th metal-oxide-semiconductor M6 drain electrode connection the 6th metal-oxide-semiconductor M6 grid and
8th metal-oxide-semiconductor M8 drain electrode；The source electrode of the 7th metal-oxide-semiconductor M7 connects the 9th metal-oxide-semiconductor M9 drain electrode, the 9th metal-oxide-semiconductor M9 grid
Pole and the tenth metal-oxide-semiconductor M10 grid, the source electrode of the 8th metal-oxide-semiconductor M8 connect the tenth metal-oxide-semiconductor M10 drain electrode, the described 9th
The source ground of metal-oxide-semiconductor M9 source electrode and the tenth metal-oxide-semiconductor M10.The second metal-oxide-semiconductor M2, the 3rd metal-oxide-semiconductor M3, the 4th metal-oxide-semiconductor
M4, the 5th metal-oxide-semiconductor M5 and the 6th metal-oxide-semiconductor M6 are PMOS；The 7th metal-oxide-semiconductor M7, the 8th metal-oxide-semiconductor M8, the 9th metal-oxide-semiconductor M9 and
Tenth metal-oxide-semiconductor M10 is NMOS tube.
4th metal-oxide-semiconductor M4 and the 5th metal-oxide-semiconductor M5 connect the 3rd metal-oxide-semiconductor M3 and the second metal-oxide-semiconductor M2 by grid, will
The complete mirror images of Iadim, enter in terms of the 5th metal-oxide-semiconductor M5 grids, the 4th metal-oxide-semiconductor M4 the 5th metal-oxide-semiconductor M5 of drain electrode connection source electrode,
Source negative feedback, the 5th metal-oxide-semiconductor M5 and the 6th metal-oxide-semiconductor, the 7th metal-oxide-semiconductor M7 and the 8th are introduced for the 5th metal-oxide-semiconductor M5 signals
Metal-oxide-semiconductor M8, the 9th metal-oxide-semiconductor M9 and the tenth metal-oxide-semiconductor M10 are three pairs of current-mirror structures, and the electric current for flowing through the 5th metal-oxide-semiconductor M5 passes through three
It is that the 5th metal-oxide-semiconductor M5 signals introduce positive feedback, for whole loop, it is ensured that negative-feedback is more than just to current mirror mirror image
Feedback can ensure auto bias circuit（Electric current automatic biasing subelement 1123）Normal work.The effect of this partial circuit is to stablize the 3rd
Metal-oxide-semiconductor M3, the second metal-oxide-semiconductor M2 grid voltage, without additionally introducing external bias voltage, simplify circuit structure, save pcb board
Area.
The FREQUENCY CONTROL subelement 1124, including the 11st metal-oxide-semiconductor M11, the 12nd metal-oxide-semiconductor M12, the 13rd metal-oxide-semiconductor
M13,3rd resistor R3, the 4th resistance R4, charge and discharge capacitance C1 and oscillator OSC.The source electrode of the 11st metal-oxide-semiconductor M11 is
The input of FREQUENCY CONTROL subelement 1124, source electrode, the 4th metal-oxide-semiconductor the M4 source electrode and feeder ear for connecting the 3rd metal-oxide-semiconductor M3
VCC；The grid of the 11st metal-oxide-semiconductor M11 connects the 4th metal-oxide-semiconductor M4 grid, the 3rd metal-oxide-semiconductor M3 grid and the 2nd MOS
Pipe M2 drain electrode；The 12nd metal-oxide-semiconductor M12 of drain electrode connection of 11st metal-oxide-semiconductor M11 source electrode, the 12nd metal-oxide-semiconductor
M12 grid connects the grid of the second metal-oxide-semiconductor M2 grid, the 5th metal-oxide-semiconductor M5 grid and the 6th metal-oxide-semiconductor M6；Described tenth
Two metal-oxide-semiconductor M12 drain electrode connects the input of charge and discharge capacitance C1 one end, 3rd resistor R3 one end and oscillator OSC；Institute
State first input of the charge and discharge capacitance C1 one end for the output end, connection slope compensation module of FREQUENCY CONTROL subelement 1124
End；The voltage of the output end of FREQUENCY CONTROL subelement 1124 is Vo；The other end ground connection of the charge and discharge capacitance C1, described the
The three resistance R3 other end passes through the metal-oxide-semiconductor M13 of the 4th resistance R4 connections the 13rd drain electrode, the source of the 13rd metal-oxide-semiconductor M13
Pole is grounded, the grid connection oscillator OSC of the 13rd metal-oxide-semiconductor M13 output end.The 11st metal-oxide-semiconductor M11 and the tenth
Two metal-oxide-semiconductor M12 are PMOS, and the 13rd metal-oxide-semiconductor M13 is NMOS tube.
Icharge electric currents flow through the 11st metal-oxide-semiconductor M11, the 12nd metal-oxide-semiconductor M12, the complete mirror image Iadim of this electric current, therefore
Icharge=VS/R2.Oscillator OSC is using classical threshold level comparator configuration, and therefore not to repeat here.3rd resistor R3,
Four resistance R4 and the 13rd metal-oxide-semiconductor M13 are discharge path.The course of work is as follows：Initial state Vo is less than oscillator OSC threshold
It is worth the upper limit, the voltage Vc of oscillator OSC output ends is low level, and Icharge charges for C1, and Vo increases, sawtooth waveforms rises；Work as Vo
When reaching the upper threshold set by oscillator OSC, Vc is changed into high level, and the 13rd metal-oxide-semiconductor M13 conductings, C1 starts electric discharge, Vo
Reduce, now sawtooth waveforms declines；When Vo reaches bottom threshold set by oscillator OSC, Vc is changed into low level, the 13rd again
Metal-oxide-semiconductor M13 disconnects, and restarts next cycle and is charged for C1, and so on.
Charge and discharge capacitance C1, oscillator OSC upper threshold and bottom threshold are constant in this circuit, therefore influence sawtooth
The factor of wave frequency rate only has Icharge size, due to Icharge=VS/R2, R2（R2 resistance value）It is also constant, so VS
It is the key factor for determining sawtooth wave frequency rate.According to above form, under normal operating conditions, Vadim is set greater than VH, therefore VS
VH, Icharge=VH/R2 are output as, in most of scope, system frequency is fixed, and works in PWM mode；When system load becomes
It is small, when reaching critical point, i.e. VH>Vadim>During VL, now VS is output as Vadim, Icharge=Vadim/R2, within this range
System frequency changes and changed with Vadim, works in PFM patterns；When system load is changed into minimum, i.e. Vadim<During VL, to protect
System worked well is demonstrate,proved, system recovers PWM mode of operations, but now working frequency is extremely low, limit Icharge=VL/R2.
PWM and PFM switching critical points VH, can be determined according to system actual efficiency, it is preferred that by PWM mode and PFM
The efficiency curve of pattern takes joining, and as critical point, in other words, the first threshold voltage VH are voltage loop by adjusting
The dutycycle of the square-wave signal exported is saved to control the efficiency curve during voltage loaded and the square-wave signal by adjusting output
Pulse frequency come control load voltage when efficiency curve the corresponding voltage of joining, in this way, so that load effect
Rate highest.
Referring to Fig. 5, the slope compensation module 120 includes the 14th metal-oxide-semiconductor M14, the 15th metal-oxide-semiconductor M15, the 16th
Metal-oxide-semiconductor M16, the 17th metal-oxide-semiconductor M17, the 5th resistance R5, the first electric capacity C2 and the second electric capacity C3.The 14th metal-oxide-semiconductor M14
Source electrode connection feeder ear VCC；The grid of the 14th metal-oxide-semiconductor M14 connects the 3rd metal-oxide-semiconductor M3 grid, the described 14th
Metal-oxide-semiconductor M14 the 15th metal-oxide-semiconductor M15 of drain electrode connection source electrode, the grid of the 15th metal-oxide-semiconductor M15 connects the second metal-oxide-semiconductor
M2 grid（14th metal-oxide-semiconductor M14, the 15th metal-oxide-semiconductor M15 effect and the 11st metal-oxide-semiconductor M11, the 12nd metal-oxide-semiconductor M12
Effect is identical, is to obtain image current Icharge according to electric current Iadim）, the drain electrode of the 15th metal-oxide-semiconductor M15 is slope
The output end of compensating module 120, the one end for connecting the 5th resistance R5, the first input of the first electric capacity C2 one end and comparison module
End；The other end of the 5th resistance R5 connects the 16th metal-oxide-semiconductor M16 drain electrode, and the grid of the 16th metal-oxide-semiconductor M16 connects
Oscillator OSC output end is connect, the source electrode of the 16th metal-oxide-semiconductor M16 connects the 17th metal-oxide-semiconductor M17 drain electrode, the first electric capacity
One end of the inductance of the C2 other end, the second electric capacity C3 one end and LED constant current drive system, i.e. the first electric capacity C2's
The other end is the second input of slope compensation module 120, the inductive current sampled signal ISW of input LED constant current drive system；
The grid of the 17th metal-oxide-semiconductor M17 inputs the current bias signal Bias of the first electric capacity C2 discharge path, in other words,
The grid of the 17th metal-oxide-semiconductor M17 connects the 9th metal-oxide-semiconductor M9 grid, the source ground of the 17th metal-oxide-semiconductor M17, institute
State the second electric capacity C3 other end ground connection.The 14th metal-oxide-semiconductor M14 and the 15th metal-oxide-semiconductor M15 is PMOS；16th MOS
Pipe M16 and the 17th metal-oxide-semiconductor M17 is NMOS tube.The grid of the 14th metal-oxide-semiconductor M14, the 15th metal-oxide-semiconductor M15 grid and
16th metal-oxide-semiconductor M16 grid constitutes the first input end of slope compensation module 120.The 14th metal-oxide-semiconductor M14 and
15 metal-oxide-semiconductor M15 come electric current Icharge mirror images.Specifically, the FREQUENCY CONTROL subelement 1124 produces image current
Icharge and Vc, Icharge carry out discharge and recharge to electric capacity C1 so as to the sawtooth waveforms Vo produced by Vc；And the 14th MOS
Pipe M14 and the 15th metal-oxide-semiconductor M15 come electric current Icharge mirror images, and electric current Icharge is carried out by Vc to electric capacity C2 and C3
Discharge and recharge, in no ISW signals, the voltage Vslope of the output end of slope compensation module 120 is sawtooth waveforms, itself and frequency control
Sawtooth waveforms at the Vo of subunit 1124 is identical, in other words, and slope compensation module 120 automatically selects module to PWM/PFM
The sawtooth signal of 110 outputs has carried out mirror image, then is folded with the inductive current sampled signal ISW of LED constant current drive system
Plus.
Icharge electric currents automatically select module 110 by PWM/PFM and provided, and charge and discharge electric signal is also provided by oscillator OSC,
It can so ensure that the working frequency of slope compensation is consistent with system operating frequency.Circuit operation principle is Icharge to first
Electric capacity C2 carries out the sawtooth signal of discharge and recharge generation, and ISW is its exterior inductance sampled signal, when Icharge is to the first electricity
When holding C2 chargings, sawtooth waveforms rises, and now external power pipe is turned on, and ISW signals and sawtooth signal are superimposed simultaneously, increase conducting
When slope, play compensating action.Slope compensation can be when effectively suppression system dutycycle be excessive subharmonic oscillation, improve system
System stability.
Referring to Fig. 6, the first voltage multiplies module 210 again includes the second operational amplifier OP5, first resistor string Rn1
Powered with the 6th resistance R6, the second operational amplifier OP5 by feeder ear VCC；The positive of the second operational amplifier OP5
Input multiplies the input of module 210, connection simulation dimmer voltage signal Vadim for first voltage and provides end, described second again
Operational amplifier OP5 output end is that first voltage multiplies the output end of module 210, the first of connection spaning waveguide operational amplifier module 230 again
One end of input and first resistor string Rn1, the other end of the first resistor string Rn1 connects the second operational amplifier OP5's
Inverting input is simultaneously grounded by the 6th resistance R6.The first resistor string Rn1 includes n-1 resistance, first resistor string Rn1
In each resistance resistance it is identical with the 6th resistance R6, multiplied again by first voltage module 210 can will simulation dimmer voltage letter
Number Vadim amplifies predetermined multiplying power n, and the predetermined multiplying power n is determined by first resistor string Rn1 resistance.
The second voltage multiplies module 220 again includes the 3rd operational amplifier OP6, second resistance string Rn2 and the 7th resistance
R7, the 3rd operational amplifier OP6 is powered by feeder ear VCC；The normal phase input end of the 3rd operational amplifier OP6 is the
Two voltages multiply the corresponding sampled voltage signal of the input of module 220, input load sample rate current, the 3rd operation amplifier again
Device OP6 output end be second voltage multiply again the output end of module 220, the second input of connection spaning waveguide operational amplifier module 230 and
Second resistance string Rn2 one end, the other end of the second resistance string Rn2 connects the 3rd operational amplifier OP6 anti-phase input
Hold and be grounded by the 7th resistance R7.The second resistance string Rn2 includes each in n-1 resistance, second resistance string Rn2
The resistance of resistance is identical with the 7th resistance R7, and the corresponding sampling of sample rate current can will be loaded by multiplying module 220 again by second voltage
Voltage signal amplifies predetermined multiplying power n, and the predetermined multiplying power n is determined by second resistance string Rn2 resistance.
The spaning waveguide operational amplifier module 230 includes operational transconductance amplifier OP7, the 18th metal-oxide-semiconductor M18, the 19th metal-oxide-semiconductor
M19 and the 20th metal-oxide-semiconductor M20, the operational transconductance amplifier OP7 is powered by feeder ear VCC.The operational transconductance amplifier
OP7 normal phase input end is the first input end of spaning waveguide operational amplifier module 230, the second operational amplifier OP5 of connection output end；Institute
State second input, connection threeth operation amplifier of the operational transconductance amplifier OP7 inverting input for spaning waveguide operational amplifier module 230
Device OP6 output end；The output end of the operational transconductance amplifier OP7 connects the 18th metal-oxide-semiconductor M18 drain electrode, the 19th MOS
The grid of pipe M19 grid and the 20th metal-oxide-semiconductor M20；The grid of the 18th metal-oxide-semiconductor M18 inputs for digital PWM signal
End, for inputting digital PWM signal DPWM.The source ground of the 18th metal-oxide-semiconductor M18, the 20th metal-oxide-semiconductor M20's
Source electrode connection feeder ear VCC, the 19th metal-oxide-semiconductor M19 drain electrode are the output end of spaning waveguide operational amplifier module 230, connection second
Ten metal-oxide-semiconductor M20 drain electrode, the source ground of the 19th metal-oxide-semiconductor M19.The 18th metal-oxide-semiconductor M18 and the 19th metal-oxide-semiconductor
M19 is NMOS tube, and the 20th metal-oxide-semiconductor M20 is PMOS.
To improve the response of system, the present invention carries out equal proportion to Visen and Vadim and multiplies amplification, the second computing again respectively
Amplifier OP5, first resistor string Rn1 and the 6th resistance R6 constitute n times and multiply circuit, and output end voltage is nVadim（N times
Vadim）；Similarly the 3rd operational amplifier OP6, second resistance string Rn2 and the 7th resistance R7 constitute another n times and multiply circuit,
Output end voltage is nVisen（N times of Visen）.NVadim and nVisen are being respectively connected to operational transconductance amplifier OP7 input just
Anti-phase two ends, by controlling prime driving power pipe M20 and M19 state, adjust external power pipe, have realized to feedback signal
Quick response.
The present invention is while reserved digital PWM light modulation（DPWM）Function, the 18th metal-oxide-semiconductor M18 is used as prime driving power pipe
M20 and M19 enable pipe, grid can access DPWM signals, and digital PWM dimming function is realized by controlling switch state, if
DPWM functions are not needed, the 18th metal-oxide-semiconductor M18 signal is set to high level, system worked well is not influenceed.
Prime is driven to push-pull configuration in the present invention, is output as switch state signal, speed, and in actual applications one
As rear class driving MOSFET constant current tubes.20th metal-oxide-semiconductor M20 is deleted, only stays the 19th metal-oxide-semiconductor M19 to be driven as prime, this
The base stage that structure rear class is connected to outside PNP constant current tubes is planted, base current can be provided for PNP, PNP constant current tubes are directly driven.This
Invention is provided in such alternative, practical application, can be considered to select concrete scheme according to the compromise of performance and cost, carried
The high application flexibility of the present invention.
The constant-current control circuit of the LED constant current drive system provided based on above-described embodiment, the present invention also provides a kind of LED
Constant current driving system.The first embodiment for the LED constant current drive system that Fig. 7 provides for the present invention（Drive MOSFET）Circuit
Figure, in the present embodiment, the LED constant current drive system include constant-current control circuit as described above, in addition to power supply VIN,
Inductance L1, diode D1, the 3rd electric capacity C4, LED string LED1, the 8th resistance R8, the 9th resistance R9, the first power MOS pipe U1
With the second power MOS pipe U2.The negative pole ground connection of the power supply VIN, the positive pole of the power supply VIN passes through inductance L1 the first work(of connection
Rate metal-oxide-semiconductor U1 drain electrode and diode D1 positive pole, the grid of the first power MOS pipe U1 connect the output of drive module
End, the source electrode of the first power MOS pipe U1 connects the second input of slope compensation module, also connect by the 8th resistance R8
Ground；The negative pole of the diode D1 connects LED string LED1 positive pole, also passes through the 3rd electric capacity C4 ground connection；The LED string
LED1 negative pole connects the second power MOS pipe U2 drain electrode, the grid connection spaning waveguide operational amplifier module of the second power MOS pipe U2
Output end, the source electrode of the second power MOS pipe U2 connects the input that the 9th resistance R9 one end, second voltage multiply module again
End and the second input of error amplification module；The other end ground connection of the 9th resistance R9.The first power MOS pipe U1 and
Second power MOS pipe U2 is NMOS tube.
First power MOS pipe U1, inductance L1, the classical boost configuration of diode D1, the 3rd electric capacity C4 composition, the load of system
It is single-string LED lamp string LED1, the second power MOS pipe U2 is LED string LED1 driving tube, and the 9th resistance R9 is load current
Sampling resistor.It is briefly described as follows system work process：Vadim is the simulation dim signal of system, can be given according to practical application
Go out, Visen is load current sampled signal, inductive current sampled signal ISW, voltage loop work is as follows：Vadim passes through PWM/
PFM is automatically selected after module, and the sawtooth waveforms of respective frequencies is exported according to Vadim actual values, then with ISW signals through slope compensation mould
Exported after block superposition；Visen samples to load current in real time, passes through error amplification module with simulation dim signal Vadim,
It is compared afterwards with the signal after slope compensation, the current signal change that sampling is got is presented as drive module to driving tube
（First power MOS pipe U1）Square-wave signal change in duty cycle, after classical boost configuration, output voltage can be changed at any time
VOUT, when Visen is not up to Vadim, VOUT persistently rises, as Visen=Vadim, and system is stable, and VOUT is in dynamic
Poised state.Current loop work is as follows：Load current sampled signal Visen and simulation dim signal Vadim pass through n times simultaneously
Multiply after amplification, the outside constant-current power pipe of driving is compared by trsanscondutance amplifier（Second power MOS pipe U2）, can be to load current
Minor variations adjust rapidly, effectively improve system response time.The voltage loop and current loop of system work simultaneously, control
While VOUT, the dynamic change to Visen is also adjusted in real time.
In whole embodiment, dotted box portion is the constant-current control circuit of the present invention, peripheral circuit（Except constant-current control circuit
Circuit part in addition）LED number can be increased and decreased according to practical application, referred in addition for digital PWM light modulation, degree of regulation etc.
Mark, can also increase and decrease, application is wider according to demand.
Referring to Fig. 8, the second embodiment for the LED constant current drive system that the present invention is provided（Drive BJT）Circuit diagram, this
Embodiment is identical with first embodiment structure, and difference is that the constant current tube U2 driven is BJT bipolar transistors.
Specifically, in the present embodiment, the LED constant current drive system includes constant-current control circuit as described above, also wraps
Include power supply VIN, inductance L1, diode D1, the 3rd electric capacity C4, LED string LED1, the 8th resistance R8, the 9th resistance R9, the tenth electricity
Hinder R10, the first power MOS pipe U1 and BJT bipolar transistor U2.The negative pole ground connection of the power supply VIN, the power supply VIN's
Positive pole by inductance L1 the first power MOS pipes of connection U1 drain electrode and diode D1 positive pole, the first power MOS pipe U1's
Grid connects the output end of drive module, the second input of the source electrode connection slope compensation module of the first power MOS pipe U1
Hold, also pass through the 8th resistance R8 ground connection；The negative pole of the diode D1 connects LED string LED1 positive pole, also passes through the 3rd electricity
Hold C4 ground connection；The negative pole of the LED string LED1 connects the second power MOS pipe U2 source electrode, also passes through the tenth resistance R10 connections
BJT bipolar transistors U2 grid, the grid of the second power MOS pipe U2 connects the output end of spaning waveguide operational amplifier module, institute
State the second power MOS pipe U2 drain electrode connection the 9th resistance R9 one end, second voltage and multiply the input and error of module again and put
Second input of big module；The other end ground connection of the 9th resistance R9.The first power MOS pipe U1 is NMOS tube.
In the present embodiment, a PMOS driving tube need to be only deleted in current loop（20th metal-oxide-semiconductor M20, Fig. 6
It is shown）, by atomic small change, the beneficial effect of acquisition is to improve the flexibility of practical application, can be as needed
The peripheral scheme of selection, reduces periphery PCB costs.Due to the present embodiment and first embodiment architectural difference less, principle is identical, therefore
Workflow is repeated no more.
The LED constant current drive system of the present invention can meet the index in this application well.Except this implementation exception, this hair
The bright electronic system and any constant current driving system for applying also for any LED drivings.
Existing technology, is controlled using single loop, and load current is sampled and feeds back to control section, through control section, is risen
Pressure and peripheral driver realize the control to output voltage, and then adjust load current, and this loop has the disadvantage that feedback form is single,
Response speed is general, and the precision of load current is determined by output voltage precision, therefore control accuracy is general.And what the present invention was provided
LED constant current drive system and its constant-current control circuit, change the single loop control of prior art, using double loop parallel control.
Wherein voltage loop load feedback electric current adjusts driving stage dutycycle through control section, and then adjusts system output voltage, electric current
Control of the loop to feedback signal is embodied directly in prime driving, more quickly and effectively adjusts load current, improves system
Dynamic response, load current precision is not only determined by voltage loop, while by current loop control, improving the essence of load current
Degree.Moreover, system realizes the double mode automatic switchover work of PWM/PFM, the work side of fixed-frequency PWM is usually taken in prior art
Formula, has the disadvantage that frequency is immutable, therefore efficiency can decline therewith during load reduction, and system frequency can be with load change in the present invention
Adjustment in time, it can be ensured that system maintains efficiency operation all the time.In addition, the present invention can provide two kinds of peripheral driver modes
（MOSFET and BJT）, the existing usual customization of LED actuation techniques is higher, and application scenario there are certain requirements, and the present invention is in reality
Drive scheme can be selected according to demand in the application of border, improve the flexibility of application.
It is understood that for those of ordinary skills, can be with technique according to the invention scheme and its hair
Bright design is subject to equivalent substitution or change, and all these changes or replacement should all belong to the guarantor of appended claims of the invention
Protect scope.
Claims (9)
1. a kind of constant-current control circuit of LED constant current drive system, it is characterised in that including：
Voltage loop, for when simulating dimmer voltage signal more than first threshold voltage, passing through the square-wave signal for adjusting output
Dutycycle come control load voltage, make the constant current hold of load；It is less than first threshold in simulation dimmer voltage signal
During voltage, the voltage of load is controlled by adjusting the pulse frequency of the square-wave signal exported, makes the constant current hold of load；
Current loop, for according to simulation dimmer voltage signal and load sample rate current, adjusting the electric current of load, making the electricity of load
Stream keeps constant；
The current loop includes:
First voltage multiplies module again, for simulation dimmer voltage signal to be amplified by predetermined multiplying power, and by the mould after amplification
Intend dimmer voltage signal output and give spaning waveguide operational amplifier module；
Second voltage multiplies module again, is amplified for will load the corresponding sampled voltage signal of sample rate current by predetermined multiplying power,
And give spaning waveguide operational amplifier module by the sampled voltage signal output after amplification；
Spaning waveguide operational amplifier module, for comparing the simulation dimmer voltage signal after amplification and the sampled voltage signal after amplification, and root
Adjust the electric current of load in real time according to comparative result, make the constant current hold of load.
2. the constant-current control circuit of LED constant current drive system according to claim 1, it is characterised in that the Voltage loop
Road includes：
PWM/PFM automatically selects module, for when simulating dimmer voltage signal more than first threshold voltage, frequency sawtooth to be determined in output
Ripple signal；When simulating dimmer voltage signal less than first threshold voltage, output frequency is according to the change for simulating dimmer voltage signal
The sawtooth signal changed and changed；
Slope compensation module, for the inductive current sampled signal and PWM/PFM of LED constant current drive system to be automatically selected into module
The sawtooth signal of output is overlapped；
Error amplification module, for being missed to simulation dimmer voltage signal sampled voltage signal corresponding with load sample rate current
Difference compares, and produces the voltage signal of dynamic change and exports to comparison module；
Comparison module, the signal of voltage signal and slope compensation the module output for error amplification module to be exported is compared
The voltage of load is controlled compared with, the variable square-wave signal of output duty cycle, makes the constant current hold of load.
3. the constant-current control circuit of LED constant current drive system according to claim 2, it is characterised in that the Voltage loop
Road also includes drive module, and the drive module is used to carry out tandem type amplification to the square-wave signal that comparison module is exported, increased
The load capacity of the square-wave signal.
4. the constant-current control circuit of LED constant current drive system according to claim 2, it is characterised in that the PWM/PFM
Automatically selecting module includes：
Voltage selecting unit, for when simulating dimmer voltage signal more than first threshold voltage, exporting first threshold voltage；
When simulation dimmer voltage signal is more than second threshold voltage and is less than first threshold voltage, output simulation dimmer voltage signal；
When simulating dimmer voltage signal less than second threshold voltage, second threshold voltage is exported；
Sawtooth waveforms generation unit, for when voltage selecting unit exports first threshold voltage, exporting and first threshold voltage pair
That answers determines frequency sawtooth signal；In voltage selecting unit output simulation dimmer voltage signal, output frequency is dimmed according to simulation
The change of voltage signal and the sawtooth signal changed；When voltage selecting unit exports second threshold voltage, output and second
Threshold voltage is corresponding to determine frequency sawtooth signal.
5. the constant-current control circuit of LED constant current drive system according to claim 4, it is characterised in that the sawtooth waveforms
Generation unit includes：
Low pressure difference linear voltage regulator subelement, the voltage signal for being exported to voltage selecting unit carries out voltage stabilizing；
Electric current automatic biasing subelement, the voltage signal for low pressure difference linear voltage regulator subelement to be exported is changed into it into just
The current signal of ratio, carries out mirror image to the current signal, obtains image current；
FREQUENCY CONTROL subelement, during the bottom threshold of oscillator, passes through for the voltage in built-in charge and discharge capacitance less than built in
Image current charges to charge and discharge capacitance；When the voltage of charge and discharge capacitance exceedes the upper threshold of oscillator, oscillator is filled
Discharge capacity discharges；The voltage of the charge and discharge capacitance is the output voltage of FREQUENCY CONTROL subelement.
6. the constant-current control circuit of LED constant current drive system according to claim 5, it is characterised in that the sawtooth waveforms
Generation unit also includes locking subelement, and the voltage signal that the locking subelement is used to export in voltage selecting unit is less than lock
When determining threshold voltage, low pressure difference linear voltage regulator subelement is closed；The lock threshold voltage is less than second threshold voltage.
7. the constant-current control circuit of LED constant current drive system according to claim 4, it is characterised in that the voltage choosing
Select unit including first comparator, the second comparator, the first NOT gate, the second NOT gate, the 3rd NOT gate, the 4th NOT gate, the 5th NOT gate,
First NAND gate, the first transmission gate, the second transmission gate and the 3rd transmission gate；The simulation dimmer voltage signal provides end connection the
The input of the inverting input of one comparator, the inverting input of the second comparator and the second transmission gate；Described first compares
The normal phase input end input first threshold voltage of device, the normal phase input end input second threshold voltage of second comparator；Institute
The output end for stating first comparator connects the input of the first NOT gate, and the output end of first NOT gate connects the defeated of the second NOT gate
Enter the control end of end and the first transmission gate, the input input first threshold voltage of first transmission gate；Second NOT gate
Output end connect the first NAND gate first input end；The output end of second comparator connects the input of the 3rd NOT gate
End, the output end of the 3rd NOT gate connects the input of the 4th NOT gate and the second input of the first NAND gate；Described 4th
The output end of NOT gate connects the control end of the 3rd transmission gate, the input input second threshold voltage of the 3rd transmission gate；Institute
The output end for stating the first NAND gate connects the input of the 5th NOT gate, and the output end of the 5th NOT gate connects the second transmission gate
Control end, the output end of second transmission gate for voltage selecting unit output end, connect the first transmission gate output end, the
The output end of three transmission gates and the input of sawtooth waveforms generation unit.
8. the constant-current control circuit of LED constant current drive system according to claim 5, it is characterised in that the low voltage difference
Linear voltage regulator subelement includes the first operational amplifier, the first metal-oxide-semiconductor, first resistor, second resistance；First computing is put
The normal phase input end of big device is the input of low pressure difference linear voltage regulator subelement, the output end of connection voltage selecting unit；Institute
The output end for stating the first operational amplifier connects the grid of the first metal-oxide-semiconductor, and the drain electrode of first metal-oxide-semiconductor is steady for low pressure difference linearity
The output end of depressor subelement, the source electrode of first metal-oxide-semiconductor connects one end and the first fortune of second resistance by first resistor
Calculate amplifier inverting input, the other end ground connection of the second resistance.
9. a kind of LED constant current drive system, it is characterised in that including the current constant control as described in claim 1-8 any one
Circuit.
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| CN109831843B (en) * | 2017-11-23 | 2021-03-23 | 立锜科技股份有限公司 | Light-emitting element driving device with multiple dimming modes and conversion control circuit thereof |
| CN108770132B (en) * | 2018-07-23 | 2023-11-03 | 深圳市明微电子股份有限公司 | LED full-voltage high-efficiency linear driving circuit |
| CN110031660A (en) * | 2019-05-17 | 2019-07-19 | 吴忌 | A kind of multi-functional maintaining detector |
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| CN113162511B (en) * | 2021-04-20 | 2022-08-30 | 江西省万佳通照明科技有限公司 | Broken wall machine integrated circuit |
| CN114244155B (en) * | 2021-12-17 | 2024-03-01 | 深圳市必易微电子股份有限公司 | Double-loop control circuit for power supply conversion circuit and high-precision constant-current control method |
| CN114489216B (en) * | 2022-04-14 | 2022-06-24 | 深圳市赛元微电子有限公司 | Protection circuit applied to LDO (low dropout regulator) |
| CN114596821B (en) * | 2022-05-09 | 2022-08-16 | 惠科股份有限公司 | Control circuit, control method and display device |
| CN114980422B (en) * | 2022-05-19 | 2024-04-09 | 东风柳州汽车有限公司 | Self-adaptive constant current control circuit |
| CN116456528B (en) * | 2023-03-21 | 2023-11-03 | 江苏帝奥微电子股份有限公司 | PWM dimming control system and method thereof |
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| KR20080071072A (en) * | 2005-11-22 | 2008-08-01 | 로무 가부시키가이샤 | Inverter, its control circuit, and light emitting device and liquid crystal television using the same |
| CN101430863B (en) * | 2008-12-02 | 2010-12-01 | 晋城市环球利特光电技术有限公司 | Led back light source driving circuit |
| CN101466187B (en) * | 2009-01-05 | 2012-06-27 | 西安理工大学 | LED drive circuit for PFM/PWM bimodal switch light modulation |
| CN202488816U (en) * | 2012-02-07 | 2012-10-10 | 英飞特电子（杭州）有限公司 | Light-emitting diode (LED) light-adjusting control device |
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