CN103957640B - LED drive circuit and its control method - Google Patents
LED drive circuit and its control method Download PDFInfo
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- CN103957640B CN103957640B CN201410198066.6A CN201410198066A CN103957640B CN 103957640 B CN103957640 B CN 103957640B CN 201410198066 A CN201410198066 A CN 201410198066A CN 103957640 B CN103957640 B CN 103957640B
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Abstract
Disclose a kind of LED drive circuit and its control method.The LED drive circuit includes power switch and control circuit；The power switch is used for the turn-on and turn-off of the driving current path for controlling driving LED load；The control circuit includes charging capacitor, the control circuit controls the power switch conducting according to predetermined clock signal, and the charging capacitor is charged using driving current sampled signal, control the power switch to turn off when charging capacitor voltage rises to shut-off threshold value.The turn-on and turn-off of LED drive current path are controlled by being arranged at the power switch on driving current path, and then are directly based upon commutation output signal to realize lighting the driving of LED load, thus, it is possible to reduce the volume of LED drive circuit.
Description
Technical field
The present invention relates to Power Electronic Technique, and in particular to a kind of LED drive circuit and its control method.
Background technology
The features such as light emitting diode (LED) possesses energy-conservation, efficient, pollution-free, long-life and small volume, is widely used
In various occasions, such as mobile phone backlight illumination, giant-screen back lighting, automobile lamp illumination and Landscape Lighting etc..Existing LED
Drive circuit is generally to be realized using switchmode converter, and switchmode converter includes the device such as switching tube, energy-storage travelling wave tube.Example
Such as, the LED drive circuit realized using inverse excitation type converter generally includes switching tube, diode, transformer and electric capacity, its volume
It is larger, it is unfavorable for being placed on inside LED lamp cover.
The content of the invention
In view of this, the present invention provides a kind of LED drive circuit and its control method, to reduce the body of LED drive circuit
Product.
A kind of first aspect, there is provided LED drive circuit, including power switch and control circuit；
The power switch is used for the turn-on and turn-off of the driving current path for controlling driving LED load；
The control circuit includes charging capacitor, and the control circuit controls the power switch according to predetermined clock signal
Conducting, and the charging capacitor is charged using driving current sampled signal, when charging capacitor voltage rises to shut-off threshold value
The power switch is controlled to turn off.
Preferably, the control circuit also includes driving current sample circuit, discharge switch, comparator, pulse generation electricity
Road and rest-set flip-flop；
The driving current sample circuit is used to sample the driving current for flowing through the LED load, generates the driving
Current sampling signal；
The discharge switch and charging capacitor are connected in parallel between the first input end of the comparator and earth terminal, together
When, the first input end is connected with the output end of the driving current sample circuit；
Second input of the comparator is input into the shut-off threshold value；
The pulse generation circuit is connected with the output end of the comparator, in the comparator output signal saltus step
Shi Shengcheng pulse signals, the output end of the pulse generation circuit is connected to the reset terminal of the rest-set flip-flop and the electric discharge is opened
The control end of pass；
The set end of the rest-set flip-flop is input into the predetermined clock signal, and the output end of the rest-set flip-flop is connected to work(
Rate switch controlling signal output end；
The power switch control signal output power output switch controlling signal, the power switch control signal is used
In the turn-on and turn-off for controlling the power switch.
Preferably, the power switch is power transistor, and the control circuit also slows down circuit and delay including driving
Circuit；
The driving slows down the output end and power switch control signal output for being electrically connected to the rest-set flip-flop
Between end, for the power switch control signal that the output in the output signal saltus step of the rest-set flip-flop is gradually changed,
To cause the power transistor to be gradually turned on or turn off；
The delay circuit be connected to the pulse signal generative circuit output end and the discharge switch control end it
Between, for by the pulse delay signal scheduled time, to cause that the discharge switch is complete switched off in the power transistor
After turn on.
Preferably, the driving slows down circuit and includes slowing down resistance and slow down electric capacity, it is described slow down resistance be connected to it is described
Between the output end of rest-set flip-flop and the power switch control signal output, the capacitance connection that slows down is opened in the power
Close between control signal output and the earth terminal.
Preferably, the shut-off threshold value is scheduled voltage；Or
The shut-off threshold value is the magnitude of voltage for following the crest voltage of the charging capacitor to change.
Preferably, the control circuit also includes threshold adjustment circuit, for the charging electricity according to upper a cycle
The relation of the crest voltage of appearance and the first predetermined threshold, to adjust the shut-off threshold value so that the charging electricity of current period
The crest voltage of appearance be equal to first predetermined threshold or relative to upper a cycle the charging capacitor crest voltage more
Close to first predetermined threshold, the cycle is equal to the cycle of the predetermined clock signal.
Preferably, the threshold adjustment circuit includes peak sampling hold circuit, trsanscondutance amplifier, compensating electric capacity and addition
Device；
The peak sampling hold circuit is input into the charging capacitor voltage, for obtaining described in a upper cycle
The crest voltage of charging capacitor simultaneously keeps, and is exported with the presently described cycle；
The inverting input of the trsanscondutance amplifier is connected with the peak sampling hold circuit output end, and the mutual conductance is put
The in-phase input end of big device is input into first predetermined threshold；
The compensating electric capacity is connected between the output end of the trsanscondutance amplifier and the earth terminal；
The first input end of the adder is connected with the output end of the trsanscondutance amplifier, the second input input second
Predetermined threshold, the output end of the adder exports the shut-off threshold value to the in-phase input end of the comparator.
Second aspect, there is provided a kind of LED drive circuit control method, the LED drive circuit is by power switch control
Driving the turn-on and turn-off of the driving current path of LED load, methods described includes：
The power switch conducting is controlled according to predetermined clock signal；
The driving current of sampling generates driving current sampled signal；
Charging capacitor is charged using the driving current sampled signal, when charging capacitor voltage rises to shut-off threshold value
The power switch is controlled to turn off.
Preferably, it is described to control the power switch shut-off to include when charging capacitor voltage rises to shut-off threshold value：
Controlled when the charging capacitor voltage rises to the shut-off threshold value control terminal voltage of the power switch by
Zero is gradually dropped to, so that the power switch is gradually turned off.
Preferably, the shut-off threshold value is scheduled voltage；Or
The shut-off threshold value is the magnitude of voltage for following the crest voltage of the charging capacitor to change.
The turn-on and turn-off of LED drive current path are controlled by being arranged at the power switch on driving current path,
And then be directly based upon commutation output signal and realize lighting the driving of LED load, thus, it is possible to reduce the body of LED drive circuit
Product.
Brief description of the drawings
By description referring to the drawings to the embodiment of the present invention, of the invention above-mentioned and other purposes, feature and
Advantage will be apparent from, in the accompanying drawings：
Fig. 1 is the circuit diagram of the LED drive circuit of first embodiment of the invention；
Fig. 2 is the working waveform figure of the LED drive circuit of first embodiment of the invention；
Fig. 3 is the circuit diagram of the LED drive circuit of second embodiment of the invention；
Fig. 4 is the circuit diagram of the LED drive circuit of third embodiment of the invention；
Fig. 5 is the working waveform figure of the LED drive circuit of third embodiment of the invention；
Fig. 6 is the circuit diagram of the LED drive circuit of fourth embodiment of the invention；
Fig. 7 is the circuit diagram of the threshold adjustment circuit of fourth embodiment of the invention；
Fig. 8 is the flow chart of the LED drive circuit control method of fifth embodiment of the invention.
Specific embodiment
Below based on preferred embodiment, present invention is described, but the present invention is not restricted to these embodiments.
Below to detailed description of the invention in, it is detailed to describe some specific detail sections.For a person skilled in the art
The description of part without these details can also completely understand the present invention.In order to avoid obscuring essence of the invention, known side
Method, process, flow, element and circuit do not have narration in detail.
Additionally, it should be understood by one skilled in the art that accompanying drawing is provided to descriptive purpose provided herein, and
What accompanying drawing was not necessarily drawn to scale.
It will also be appreciated that in the following description, " circuit " refers to by electric by least one element or sub-circuit
The galvanic circle that connection or electromagnetism are connected and composed." connected when element or circuit " being connected to " another element or element/circuit is claimed
" between two nodes when, it can directly be coupled or be connected to another element or there may be intermediary element, element it
Between connection can be physically, in logic or its combination.Conversely, " connecting when title element " being directly coupled to " or directly
Be connected to " another element when, it is meant that both do not exist intermediary element.
Unless the context clearly requires otherwise, otherwise entire disclosure and " including " in claims, similar etc. "comprising"
Word should be construed to the implication for including rather than exclusive or exhaustive implication；That is, be " including but not limited to " contains
Justice.
In the description of the invention, it is to be understood that term " first ", " second " etc. be only used for describe purpose, without
It is understood that to indicate or implying relative importance.Additionally, in the description of the invention, unless otherwise indicated, the implication of " multiple "
It is two or more.
Fig. 1 is the circuit diagram of the LED drive circuit of first embodiment of the invention.As shown in figure 1, LED drive circuit 1
Including power switch S1 and control circuit 11.
Power switch S1 is arranged on the current path of the driving current for driving LED load, for control electric current path
Turn-on and turn-off.
Specifically, as shown in figure 1, power switch S1 can be arranged at for by AC signal vacBe converted to direct current signal
vin(the direct current signal vinCan be any period waveform) rectification circuit 2 and LED load 3 between.
Control circuit 11 can include charging capacitor C1, and control circuit 11 controls power switch S1 according to predetermined clock signal
Conducting, and charging capacitor C1 is charged using driving current sampled signal, in the both end voltage v of charging capacitor C1c1Rise to pass
Disconnected threshold value voffWhen control power switch S1 shut-off.
Fig. 2 is the working waveform figure of the LED drive circuit of first embodiment of the invention.As shown in Fig. 2 in the present embodiment
In, the output direct current signal of rectification circuit 2 vin.Predetermined clock signal CLK exports a clock pulses so that work(at predetermined time intervals
Rate switch S1 conductings (such as moment t1).After power switch S1 conductings, driving current IinFlow through power switch S1 and LED load 3
So that LED load 3 works, simultaneously as direct current signal vinIt is lasting to rise, therefore driving current IinCorrespondingly rise.Control electricity
The sampled drive current I of road 11inAnd the driving current sampled signal I obtained using samplingsCharging capacitor C1 is charged.Thus, fill
The both end voltage v of electric capacity C1C1It is lasting to rise, shut-off threshold value v is raised to thereonoffWhen (such as moment t2), control circuit 11 control
Power switch S1 shut-offs processed so that driving current IinIt is changed into 0, LED load 3 does not light, until the predetermined clock of next cycle
Signal CLK causes that power switch S1 is turned on again.
Thus, by using direct current signal vinWhole cycle in a part drive the LED load 3 to work, Ke Yibao
Card LED load will not excessive pressure damages.
It is preferred that can be the shunt capacitance of LED load 3, to smooth curent change.
Therefore, controlled by being arranged at the power switch on driving current path LED drive current path conducting and
Turn off, and then be directly based upon commutation output signal and realize lighting the driving of LED load, thus, it is possible to reduce LED drive circuit
Volume.
Fig. 3 is the circuit diagram of the LED drive circuit of second embodiment of the invention.As shown in figure 3, LED drive circuit 1
Including power switch S1 and control circuit 11.
Power switch S1 is arranged at the driving current I for driving LED loadinCurrent path on, for control electric current path
Turn-on and turn-off.
Control circuit 11 includes driving current sample circuit 11a, discharge switch S2, charging capacitor C1, comparator CMP, arteries and veins
Rush generative circuit oneshot and rest-set flip-flop 11b.
Wherein, driving current sample circuit 11a is connected on current path, for the driving current to flowing through LED load 3
IinSampling, generation driving current sampled signal Is。
Discharge switch S2 and charging capacitor C1 are connected in parallel between the first input end of comparator CMP and earth terminal, together
When, the first input end of comparator CMP is connected with the output end of driving current sample circuit 11a.
The second input input shut-off threshold value v of comparator CMPoff。
Pulse generation circuit oneshot is connected with the output end of comparator CMP, for the output signal in comparator CMP
Pulse signal is generated during saltus step.The output end of pulse generation circuit oneshot is connected to reset terminal and the electric discharge of rest-set flip-flop 11b
Switch the control end of S2.
The set end input predetermined clock signal CLK of rest-set flip-flop 11b, its output end is connected to power switch control signal
Output end.
Power switch control signal output power output switch controlling signal vgate, power switch control signal vgateWith
In the turn-on and turn-off of control power switch S1.
In the circuit of Fig. 3, set end input the predetermined clock signal CLK, predetermined clock signal CLK of rest-set flip-flop 11b
Clock pulses can cause that rest-set flip-flop 11b is set output high level.High level control power switch S1 conductings.In work(
After rate switch S1 conductings, driving current IinPower switch S1 and LED load 3 are flowed through so that LED load 3 works, simultaneously as directly
Stream signal vinIt is lasting to rise, therefore driving current IinCorrespondingly rise, and then cause and driving current IinProportional driving electricity
Stream sampled signal IsRise.Because discharge switch S2 is off state, driving current sampled signal IsCharging capacitor C1 is filled
Electricity so that charging capacitor C1 both end voltages vc1Rise.
In one preferred embodiment, as shown in figure 3, shut-off threshold value voffIt is scheduled voltage, comparator CMP's
First input end is inverting input, and the second input is in-phase input end.In charging capacitor C1 both end voltages vc1Rise to pre-
Fixed shut-off threshold value voffWhen, the output signal of comparator CMP is changed into low level, pulse generation circuit oneshot by high level
Trailing edge (by high level saltus step to low level saltus step) generation pulse signal according to signal.Certainly, those skilled in the art
It is appreciated that, it is also possible to which first input end is set to in-phase input end, the second input is set to inverting input, only needs
Cause that pulse generation circuit oneshot generates pulse signal according to the rising edge of signal.
The of short duration conductings of pulse signal control discharge switch S2 are so as to discharge charging capacitor C1 so that charging capacitor C1 two ends
Voltage vc1Zero.Meanwhile, pulse signal is applied to the reset terminal of rest-set flip-flop 11b so that rest-set flip-flop 11b is reset, power
Switch controlling signal vgateIt is changed into low level.Low level control power switch S1 is turned off.
Thus, the turn-on and turn-off of power switch are controlled by the discharge and recharge to charging capacitor, can be accurately controlled
It is input into the average current of LED load.
Fig. 4 is the circuit diagram of the LED drive circuit of third embodiment of the invention.As shown in figure 4, the present embodiment
LED drive circuit is that in the present embodiment, power switch S1 is with the difference of the LED drive circuit of second embodiment
Power transistor M, meanwhile, control circuit 11 ' also slows down circuit 11c and delay circuit delay including driving.
The drain electrode of power transistor M is connected with rectification circuit 2, and source electrode is connected with LED load 3, and grid is control end.When
So, it will be understood by those skilled in the art that during using different classes of power transistor, above-mentioned annexation may not
Together.
Driving slows down output end and power switch control signal output that circuit 11c is connected to the rest-set flip-flop 11b
Between, for the power switch control signal v that the output in the output signal saltus step of the rest-set flip-flop is gradually changedgate。
Fig. 5 is the working waveform figure of the LED drive circuit of third embodiment of the invention.As shown in figure 5, driving slows down circuit
11c can cause the power switch control signal v being applied on power transistor MgateLow level is tapered to by high level.
Accordingly, power switch control signal vgateTaper to it is low level during, flow through the driving current of power transistor M
IinIt is gradually reduced until and eventually becomes zero.That is, in the both end voltage v of charging capacitor C1c1Rise to shut-off threshold value voffWhen, work(
Rate transistor M is not turned off at once, but is gradually turned off.
Preferably, drive and slow down circuit 11c for RC low-pass filter circuits, it includes slowing down resistance R1 and slows down electric capacity C2,
Slow down resistance R1 to be connected between the output end of rest-set flip-flop 11b and power switch control signal output, slow down electric capacity C2 companies
It is connected between the power switch control signal output and earth terminal.Because there is charge and discharge in the electric capacity in RC low-pass filter circuits
The process of electricity, the time constant of the discharge and recharge is equal to the product of RC, so that signal can not be mutated, that is, causes that signal is jumped
Become edge slowly varying.Therefore, it can be applied to the present embodiment to slow down circuit 11c as driving.
Shut-off threshold value v is risen in the both end voltage of charging capacitor C1offIn a period of time afterwards (during t2 ' to t2), drive
Streaming current IinStill it is not zero, the both end voltage v of charging capacitor C1c1Can be because driving current sampled signal IsCharging and on continuing
Rise.Therefore, if discharged electric capacity C1 using the pulse signal control discharge switch S2 generated in moment t2 ', can cause
Circuit maloperation.So needs control discharge switch S2 to be discharged again after power transistor M is complete switched off.In the present embodiment
In, realize this purpose by setting delay circuit delay pulse signals delay scheduled time.
Delay circuit dealy be connected to pulse signal generative circuit 11a output end and discharge switch S2 control end it
Between, for the pulse delay signal scheduled time for exporting pulse signal generative circuit 11a, to cause discharge switch S2 in power
Transistor M is turned on again after complete switching off.
In the present embodiment, because power transistor M is gradually turned off, driving current IinIt is gradually varied to zero, therefore
The current break in circuit is reduced, the electromagnetic interference in circuit can be correspondingly reduced.
Fig. 6 is the circuit diagram of the LED drive circuit of fourth embodiment of the invention.As shown in fig. 6, in the present embodiment
Shut-off threshold value voffTo follow the crest voltage v of charging capacitor C1peakThe magnitude of voltage of change.
Slow down the presence of circuit 11c due to driving, power transistor M will not after the output signal saltus step of comparator CMP
Complete switch off immediately, but beginning is gradually turned off.During gradually turning off, driving current IinGradually decrease to zero, therefore,
The driving current sampled signal I that charging capacitor C1 is still reduced gradually during this periodsCharge, its both end voltage vC1Will rise
To the last power transistor M is complete switched off.Now, the crest voltage v of charging capacitor C1peakWill be greater than shut-off threshold value voff.Such as
Fruit follows the crest voltage v of charging capacitor by controlpeakThe shut-off threshold value v of changeoff, charging can be more precisely controlled
The crest voltage v of electric capacity C1peak, it is average to ensure the electric current that LED load is input in each predetermined clock signal period
Value is constant, improves systematic function.
Specifically, circuit 11 ' is controlled ' also include threshold adjustment circuit 11d, for the charging capacitor according to upper a cycle
The crest voltage v of C1peak-pWith the first predetermined threshold vref1Relation, to adjust shut-off threshold value voffSo that current period charges
The crest voltage v of electric capacity C1peakEqual to the first predetermined threshold vref1Or the peak value electricity of the charging capacitor C1 relative to upper a cycle
Pressure vpeak-pCloser to the first predetermined threshold vref1.The cycle is equal to the cycle of predetermined clock signal clk.
Preferably, can be by the first predetermined threshold vref1With the crest voltage of the charging capacitor C1 of upper a cycle
vpeak-pGeneration adjustment voltage, according to adjustment voltage and the second predetermined threshold vref2Generation shut-off threshold value voff。
Fig. 7 is the circuit diagram of the threshold adjustment circuit of fourth embodiment of the invention.As shown in fig. 7, adjusting thresholds are electric
Road 11d includes peak sampling hold circuitpEak, trsanscondutance amplifier Gm, compensating electric capacity C3 and adder Add.
Peak sampling hold circuitpEak is connected to the earth-free one end of charging capacitor C1, input charging capacitor voltage vC1,
For in upper a cycle to charging capacitor voltage vC1Crest voltage vpeak-pSample and keep, kept in current period
Output, that is, peak sampling hold circuitpEak sampling charging capacitor voltages vC1Within the cycle of a upper predetermined clock signal
Crest voltage, and export the voltage v equal with the peak value in current periodpeak.The cycle is equal to predetermined clock signal CLK's
Cycle.
The inverting input of trsanscondutance amplifier Gm can be with peak sampling hold circuitpEak output ends are connected, and mutual conductance is amplified
The in-phase input end of device Gm is input into the first predetermined threshold vref1。
Compensating electric capacity C3 is connected between the output and ground of trsanscondutance amplifier Gm.
One input of adder Add is connected with the output end of trsanscondutance amplifier Gm, another input input second
Predetermined threshold vref2, the second input input shut-off threshold value v from the output end of adder Add to comparator CMPoff。
Second predetermined threshold vref2Less than the first predetermined threshold vref1.Second predetermined threshold vref2With the first predetermined threshold
vref1It is steady state value.
It can be seen from Fig. 7, threshold value v is turned offoffEqual to the second predetermined threshold vref2With compensating electric capacity C3 both end voltages vC3's
With that is, voff=vref2+vC3。
As the crest voltage v of upper cycle charging capacitor C1peak-pEqual to the first predetermined threshold vref1When, then now compensate
Electric capacity C3 both end voltages vC3It is steady state value, circuit is in steady operation, that is, can be caused in each clock signal period
The voltage v of charging capacitor C1C1Rise to the first predetermined threshold vref1After decline.
As the crest voltage v of upper cycle charging capacitor C1peak-pMore than the first predetermined threshold vref1When, trsanscondutance amplifier
Gm output ends export negative current so that compensating electric capacity C3 both end voltages vC3Reduce, and then turn off threshold value voffAlso reduce, then now
To turn off threshold value voffIt is the voltage v of the charging capacitor C1 of reference signalC1Also to reduce, then the charging interval of charging capacitor C1
Reduce, and then cause that power transistor M is turned off in advance so that circuit can finally return to stable state.
As the crest voltage v of upper cycle charging capacitor C1peak-pLess than the first predetermined threshold vref1When, trsanscondutance amplifier
Gm output ends export positive current so that compensating electric capacity C3 both end voltages vC3Increase, and then turn off threshold value voffAlso increase, then now
To turn off threshold value voffIt is the voltage v of the charging capacitor C1 of reference signalC1Also to increase, then the charging interval of charging capacitor C1
Increase, and then cause that power transistor M is delayed to turn off so that circuit can finally return to stable state.
In the present embodiment, changed to adjust shut-off threshold according to the crest voltage of charging capacitor by threshold adjustment circuit
Value, such that it is able to realize according to charging capacitor voltage virtual condition, accurate switch-off power transistor.Certainly, art personnel
It is appreciated that above-mentioned threshold adjustment circuit can also be applied to the circuit of second embodiment.
Fig. 8 is the flow chart of the LED drive circuit control method of fifth embodiment of the invention.The present embodiment methods described is fitted
For as above LED drive circuit described in first to fourth embodiment, that is, LED drive circuit controls to drive by power switch
The turn-on and turn-off of the driving current path of LED load, methods described includes：
Step 810, power switch conducting is controlled according to predetermined clock signal.
Step 820, the driving current generation driving current sampled signal of sampling.
Step 830, using the driving current sampled signal to charging capacitor charge, rise to pass in charging capacitor voltage
The power switch is controlled to turn off during disconnected threshold value.
Preferably, in order to reduce due to the electromagnetic interference that driving current mutation is caused, in step 830 on charging capacitor voltage
The power switch shut-off is controlled when being raised to shut-off threshold value to be included：
The control terminal voltage of the power switch is controlled to gradually decrease down when charging capacitor voltage rises to shut-off threshold value
Zero, so that the power switch is gradually turned off.
Preferably, the shut-off threshold value is scheduled voltage；Or
Preferably, the shut-off threshold value is the magnitude of voltage for following the crest voltage of the charging capacitor to change.
The turn-on and turn-off of power switch are controlled by the discharge and recharge to charging capacitor, input can be accurately controlled negative
The average current of load.
The preferred embodiments of the present invention are the foregoing is only, is not intended to limit the invention, for those skilled in the art
For, the present invention can have various changes and change.It is all any modifications made within spirit and principles of the present invention, equivalent
Replace, improve etc., should be included within the scope of the present invention.
Claims (10)
1. a kind of LED drive circuit, including power switch and control circuit；
The power switch is used for the turn-on and turn-off of the driving current path for controlling driving LED load；
The control circuit includes charging capacitor, and the control circuit controls the power switch to lead according to predetermined clock signal
It is logical, and the charging capacitor is charged using driving current sampled signal, rise to shut-off threshold value time control in charging capacitor voltage
The power switch shut-off is made, even being discharged charging capacitor after delay scheduled time of existing side by side.
2. LED drive circuit according to claim 1, it is characterised in that the control circuit is also adopted including driving current
Sample circuit, discharge switch, comparator, pulse generation circuit and rest-set flip-flop；
The driving current sample circuit is used to sample the driving current for flowing through the LED load, generates the driving current
Sampled signal；
The discharge switch and charging capacitor are connected in parallel between the first input end of the comparator and earth terminal, meanwhile,
The first input end is connected with the output end of the driving current sample circuit；
Second input of the comparator is input into the shut-off threshold value；
The pulse generation circuit is connected with the output end of the comparator, for being given birth in the comparator output signal saltus step
Into pulse signal, the output end of the pulse generation circuit is connected to the reset terminal and the discharge switch of the rest-set flip-flop
Control end；
The set end of the rest-set flip-flop is input into the predetermined clock signal, and the output end of the rest-set flip-flop is connected to power and opens
Control signal output is closed, to the power switch control signal output power output switch controlling signal, the power is opened
Closing control signal is used to control the turn-on and turn-off of the power switch.
3. LED drive circuit according to claim 2, it is characterised in that the power switch is power transistor, described
Control circuit also slows down circuit and delay circuit including driving；
The driving slow down the output end that is electrically connected to the rest-set flip-flop and the power switch control signal output it
Between, for the power switch control signal that the output in the output signal saltus step of the rest-set flip-flop is gradually changed, so that
The power transistor is obtained to be gradually turned on or turn off；
The delay circuit is connected between the pulse signal generative circuit output end and the control end of the discharge switch, is used
In by the pulse delay signal scheduled time, to cause that the discharge switch is led after the power transistor is complete switched off
It is logical.
4. LED drive circuit according to claim 3, it is characterised in that the driving slows down circuit to be included slowing down resistance
With slow down electric capacity, it is described to slow down output end and the power switch control signal output that resistance is connected to the rest-set flip-flop
Between, the capacitance connection that slows down is between the power switch control signal output and the earth terminal.
5. the LED drive circuit according to any one of claim 1-4, it is characterised in that the shut-off threshold value is predetermined
Magnitude of voltage；Or
The shut-off threshold value is the magnitude of voltage for following the crest voltage of the charging capacitor to change.
6. the LED drive circuit according to any one of claim 2-4, it is characterised in that the control circuit also includes
Threshold adjustment circuit, the relation of crest voltage and the first predetermined threshold for the charging capacitor according to upper a cycle,
To adjust the shut-off threshold value so that the crest voltage of the charging capacitor of current period be equal to first predetermined threshold or
Relative to upper a cycle the charging capacitor crest voltage closer to first predetermined threshold, the cycle is equal to institute
State the cycle of predetermined clock signal.
7. LED drive circuit according to claim 6, it is characterised in that the threshold adjustment circuit includes peak value sampling
Holding circuit, trsanscondutance amplifier, compensating electric capacity and adder；
The peak sampling hold circuit is input into the charging capacitor voltage, charged described in a upper cycle for being obtained
The crest voltage of electric capacity simultaneously keeps, and is exported with the presently described cycle；
The inverting input of the trsanscondutance amplifier is connected with the peak sampling hold circuit output end, the trsanscondutance amplifier
In-phase input end be input into first predetermined threshold；
The compensating electric capacity is connected between the output end of the trsanscondutance amplifier and the earth terminal；
The first input end of the adder is connected with the output end of the trsanscondutance amplifier, and the second input input second makes a reservation for
Threshold value, the output end of the adder exports the shut-off threshold value to the in-phase input end of the comparator.
8. a kind of LED drive circuit control method, the LED drive circuit passes through power switch and controls to drive the drive of LED load
The turn-on and turn-off of streaming current path, methods described includes：
The power switch conducting is controlled according to predetermined clock signal；
The driving current of sampling generates driving current sampled signal；
Charging capacitor is charged using the driving current sampled signal, is controlled when charging capacitor voltage rises to shut-off threshold value
The power switch shut-off, even and being discharged charging capacitor after the delay scheduled time that opposes.
9. LED drive circuit control method according to claim 8, it is characterised in that the power switch is brilliant power
Body pipe；
It is described to control the power switch shut-off to include when charging capacitor voltage rises to shut-off threshold value：
The control terminal voltage for controlling the power transistor when the charging capacitor voltage rises to the shut-off threshold value is gradually
Zero is dropped to, so that the power transistor is gradually turned off.
10. LED drive circuit control method according to claim 8 or claim 9, it is characterised in that the shut-off threshold value is pre-
Determine magnitude of voltage；Or
The shut-off threshold value is the magnitude of voltage for following the crest voltage of the charging capacitor to change.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410198066.6A CN103957640B (en) | 2014-05-12 | 2014-05-12 | LED drive circuit and its control method |
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| CN105873305B (en) * | 2015-01-19 | 2018-10-30 | 帝奥微电子有限公司 | demagnetization detection circuit |
| CN106028557B (en) * | 2016-07-08 | 2018-01-05 | 上海灿瑞科技股份有限公司 | The constant current driver circuit for LED of the low total harmonic distortion of High Power Factor |
| CN110446301A (en) * | 2019-08-09 | 2019-11-12 | 上海裕芯电子科技有限公司 | A kind of light-operated boosting LED function circuit of solar energy |
| CN111010769B (en) * | 2019-12-24 | 2021-04-27 | 北京集创北方科技股份有限公司 | Amplifying circuit of charging capacitor and driving circuit of light emitting diode |
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| CN103312141A (en) * | 2013-06-09 | 2013-09-18 | 浙江大学 | AC-DC (alternating-current to direct-current) converter control circuit |
| CN203537625U (en) * | 2013-10-28 | 2014-04-09 | 湖南信息科学职业学院 | Solar semiconductor illumination system |
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| CN104080256B (en) * | 2014-07-09 | 2016-05-11 | 无锡硅动力微电子股份有限公司 | Adaptive LED current ripples is eliminated circuit |
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| CN103312141A (en) * | 2013-06-09 | 2013-09-18 | 浙江大学 | AC-DC (alternating-current to direct-current) converter control circuit |
| CN203537625U (en) * | 2013-10-28 | 2014-04-09 | 湖南信息科学职业学院 | Solar semiconductor illumination system |
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