CN103957640A - LED driving circuit and control method thereof - Google Patents
LED driving circuit and control method thereof Download PDFInfo
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- CN103957640A CN103957640A CN201410198066.6A CN201410198066A CN103957640A CN 103957640 A CN103957640 A CN 103957640A CN 201410198066 A CN201410198066 A CN 201410198066A CN 103957640 A CN103957640 A CN 103957640A
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Abstract
Disclosed are an LED driving circuit and a control method thereof. The LED driving circuit comprises a power switch and a control circuit, the power switch is used for controlling the closing and opening of a driving current access driving an LED load, and the control circuit comprises a charging capacitor, controls the power switch to be turned on according to reserved clock signals, charges the charging capacitor by utilizing driving current sampling signals and controls the power switch to be turned off when voltage of the charging capacitor rises to a turn-off threshold. The LED driving current access is controlled to be closed and closed through the power switch arranged on the driving current access, driving light emitting of the LED load is achieved directly on the basis of rectifying output signals, and accordingly the size of the LED driving circuit can be reduced.
Description
Technical field
The present invention relates to power electronic technology, be specifically related to a kind of LED drive circuit and control method thereof.
Background technology
That light-emitting diode (LED) possesses is energy-conservation, efficient, pollution-free, long-life and the feature such as volume is little, is widely used in various occasions, such as mobile phone backlight illumination, large-screen back lighting, automobile lamp illumination and Landscape Lighting etc.Existing LED drive circuit is conventionally to adopt switchmode converter to realize, and switchmode converter comprises the devices such as switching tube, energy-storage travelling wave tube.For example, the LED drive circuit that adopts inverse excitation type converter to realize generally includes switching tube, diode, transformer and electric capacity, and its volume is larger, is unfavorable for being placed on LED lampshade inner.
Summary of the invention
In view of this, the invention provides a kind of LED drive circuit and control method thereof, to reduce the volume of LED drive circuit.
First aspect, provides a kind of LED drive circuit, comprises power switch and control circuit;
Described power switch is for controlling the turn-on and turn-off of the drive current path of driving LED load;
Described control circuit comprises charging capacitor, described control circuit is according to power switch conducting described in predetermined clock signal controlling, and utilize drive current sampled signal to charge to described charging capacitor, when charging capacitor voltage rises to shutoff threshold value, control described power switch and turn-off.
Preferably, described control circuit also comprises drive current sample circuit, discharge switch, comparator, pulse generation circuit and rest-set flip-flop;
Described drive current sample circuit, for to flowing through the drive current sampling of described LED load, generates described drive current sampled signal;
Described discharge switch and charging capacitor are connected in parallel between the first input end and earth terminal of described comparator, and meanwhile, described first input end is connected with the output of described drive current sample circuit;
The second input of described comparator is inputted described shutoff threshold value;
Described pulse generation circuit is connected with the output of described comparator, and for production burst signal when the described comparator output signal saltus step, the output of described pulse generation circuit is connected to the reset terminal of described rest-set flip-flop and the control end of described discharge switch;
The set end of described rest-set flip-flop is inputted described predetermined clock signal, and the output of described rest-set flip-flop is connected to power switch control signal output;
Described power switch control signal output power output switch controlling signal, described power switch control signal is for controlling the turn-on and turn-off of described power switch.
Preferably, described power switch is power transistor, and described control circuit also comprises that driving slows down circuit and delay circuit;
Described driving slows down between the output and described power switch control signal output that circuit is connected to described rest-set flip-flop, for the described power switch control signal that output gradually changes when the output signal saltus step of described rest-set flip-flop, so that conducting or the shutoff gradually of described power transistor;
Described delay circuit is connected between described pulse signal generative circuit output and the control end of described discharge switch, for by the described pulse delay signal scheduled time, so that described discharge switch closes at described power transistor the conducting of having no progeny completely.
Preferably, described driving slows down circuit and comprises and slow down resistance and slow down electric capacity, described slowing down between the output and described power switch control signal output that resistance is connected to described rest-set flip-flop, described in slow down electric capacity and be connected between described power switch control signal output and described earth terminal.
Preferably, described shutoff threshold value is scheduled voltage; Or
Described shutoff threshold value is the magnitude of voltage of following the crest voltage variation of described charging capacitor.
Preferably, described control circuit also comprises threshold adjustment circuit, be used for according to the relation of the crest voltage of the described charging capacitor of upper one-period and the first predetermined threshold, to adjust described shutoff threshold value, make the crest voltage of the described charging capacitor of current period equal described the first predetermined threshold or more approach described the first predetermined threshold with respect to the crest voltage of the described charging capacitor of upper one-period, the described cycle equals the cycle of described predetermined clock signal.
Preferably, described threshold adjustment circuit comprises peak sampling hold circuit, trsanscondutance amplifier, building-out capacitor and adder;
Described peak sampling hold circuit is inputted described charging capacitor voltage, for obtaining the crest voltage of charging capacitor described in the upper described cycle and keeping, to export within the current described cycle;
The inverting input of described trsanscondutance amplifier is connected with described peak sampling hold circuit output, and the in-phase input end of described trsanscondutance amplifier is inputted described the first predetermined threshold;
Described building-out capacitor is connected between the output and described earth terminal of described trsanscondutance amplifier;
The first input end of described adder is connected with the output of described trsanscondutance amplifier, and the second input is inputted the second predetermined threshold, and the output of described adder is exported described shutoff threshold value to the in-phase input end of described comparator.
Second aspect, provides a kind of LED drive circuit control method, and described LED drive circuit is controlled the turn-on and turn-off of the drive current path of driving LED load by power switch, and described method comprises:
According to power switch conducting described in predetermined clock signal controlling;
The described drive current of sampling generates drive current sampled signal;
Utilize described drive current sampled signal to charge to charging capacitor, when charging capacitor voltage rises to shutoff threshold value, control described power switch and turn-off.
Preferably, describedly at charging capacitor voltage, rise to and control described power switch while turn-offing threshold value and turn-off and comprise:
The control end voltage of controlling described power switch when described charging capacitor voltage rises to described shutoff threshold value drops to zero gradually, thereby described power switch is turn-offed gradually.
Preferably, described shutoff threshold value is scheduled voltage; Or
Described shutoff threshold value is the magnitude of voltage of following the crest voltage variation of described charging capacitor.
By being arranged at power switch on drive current path, control the turn-on and turn-off of LED drive current path, and then directly based on rectification output signal, realize luminously to the driving of LED load, thus, can reduce the volume of LED drive circuit.
Accompanying drawing explanation
By the description to the embodiment of the present invention referring to accompanying drawing, above-mentioned and other objects, features and advantages of the present invention will be more clear, 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.
Embodiment
Based on preferred embodiment, present invention is described below, but the present invention is not restricted to these embodiment.In below details of the present invention being described, detailed some specific detail sections of having described.Do not have for a person skilled in the art the description of these detail sections can understand the present invention completely yet.For fear of obscuring essence of the present invention, known method, process, flow process, element and circuit do not describe in detail.
In addition, it should be understood by one skilled in the art that the accompanying drawing providing at this is all for illustrative purposes, and accompanying drawing is not necessarily drawn in proportion.
, should be appreciated that in the following description, " circuit " refers to the galvanic circle being connected and composed by electrical connection or electromagnetism by least one element or electronic circuit meanwhile.When claiming that element or circuit " are connected to " another element or claim that element/circuit " is connected to " between two nodes, it can be directly couple or be connected to another element or can have intermediary element, and the connection between element can be physically, in logic or its combination.On the contrary, when claiming element " to be directly coupled to " or during " being directly connected to " another element, meaning that both do not exist intermediary element.
Unless context explicitly calls for, otherwise the implication that " comprising " in whole specification and claims, " comprising " etc., similar word should be interpreted as comprising rather than exclusive or exhaustive implication; That is to say, be the implication of " including but not limited to ".
In description of the invention, it will be appreciated that, term " first ", " second " etc. are only for describing object, and can not be interpreted as indication or hint relative importance.In addition,, in description of the invention, except as otherwise noted, the implication of " a plurality of " 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 comprises power switch S1 and control circuit 11.
Power switch S1 is arranged on the current path of drive current of driving LED load, for controlling the turn-on and turn-off of current path.
Particularly, as shown in Figure 1, power switch S1 can be arranged at for by AC signal v
acbe converted to direct current signal v
in(described direct current signal v
incan be any period waveform) rectification circuit 2 and LED load 3 between.
Control circuit 11 can comprise charging capacitor C1, and control circuit 11 is according to predetermined clock signal controlling power switch S1 conducting, and utilizes drive current sampled signal to charging capacitor C1 charging, at the both end voltage v of charging capacitor C1
c1rise to and turn-off threshold value v
offin time, is controlled power switch S1 and turn-offs.
Fig. 2 is the working waveform figure of the LED drive circuit of first embodiment of the invention.As shown in Figure 2, in the present embodiment, rectification circuit 2 output direct current signal v
in.Predetermined clock signal CLK makes power switch S1 conducting (for example moment t1) every clock pulse of scheduled time output.After power switch S1 conducting, drive current I
inflow through power switch S1 and LED load 3 and make LED load 3 work, meanwhile, due to direct current signal v
incontinue to rise, so drive current I
incorrespondingly rise.Control circuit 11 sampling drive current I
inand the drive current sampled signal I that utilizes sampling to obtain
scharging capacitor C1 is charged.Thus, the both end voltage v of charging capacitor C1
c1continue to rise, be raised to thereon and turn-off threshold value v
offtime (for example constantly t2), control circuit 11 power ratio control switch S 1 are turn-offed, and make drive current I
inbecome 0, LED load 3 not luminous, until the predetermined clock signal CLK of next cycle makes power switch S1 conducting again.
Thus, by utilizing direct current signal v
inthe whole cycle in a part carry out driving LED load 3 work, can guarantee that LED load can not damage in overvoltage.
Meanwhile, preferably, can, for LED load 3 shunt capacitances, with smoothing current, change.
Therefore, by being arranged at power switch on drive current path, control the turn-on and turn-off of LED drive current path, and then directly based on rectification output signal, realize luminously to the driving of LED load, thus, can reduce the volume of LED drive circuit.
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 comprises power switch S1 and control circuit 11.
Power switch S1 is arranged at the drive current I of driving LED load
incurrent path on, for controlling the turn-on and turn-off of current path.
Control circuit 11 comprises drive current sample circuit 11a, discharge switch S2, charging capacitor C1, comparator C MP, pulse generation circuit oneshot and rest-set flip-flop 11b.
Wherein, drive current sample circuit 11a is connected on current path, for to flowing through the drive current I of LED load 3
insampling, generates drive current sampled signal I
s.
Discharge switch S2 and charging capacitor C1 are connected in parallel between the first input end and earth terminal of comparator C MP, and meanwhile, the first input end of comparator C MP is connected with the output of drive current sample circuit 11a.
Threshold value v is turn-offed in the second input input of comparator C MP
off.
Pulse generation circuit oneshot is connected with the output of comparator C MP, production burst signal during for output signal saltus step at comparator C MP.The output of pulse generation circuit oneshot is connected to the reset terminal of rest-set flip-flop 11b and the control end of discharge switch S2.
The set end input predetermined clock signal CLK of rest-set flip-flop 11b, its output is connected to power switch control signal output.
Power switch control signal output power output switch controlling signal v
gate, power switch control signal v
gateturn-on and turn-off for power ratio control switch S 1.
In the circuit of Fig. 3, the set end of rest-set flip-flop 11b input predetermined clock signal CLK, the clock pulse of predetermined clock signal CLK can be so that rest-set flip-flop 11b be set output high level.This high level power ratio control switch S 1 conducting.After power switch S1 conducting, drive current I
inflow through power switch S1 and LED load 3 and make LED load 3 work, meanwhile, due to direct current signal v
incontinue to rise, so drive current I
incorrespondingly rise, and then make and drive current I
inproportional drive current sampled signal I
srise.Because discharge switch S2 is in off state, drive current sampled signal I
sto charging capacitor C1 charging, make charging capacitor C1 both end voltage v
c1rise.
One preferred embodiment in, as shown in Figure 3, turn-off threshold value v
offfor scheduled voltage, the first input end of comparator C MP is inverting input, and the second input is in-phase input end.At charging capacitor C1 both end voltage v
c1rise to predetermined shutoff threshold value v
offtime, the output signal of comparator C MP changes low level into by high level, and pulse generation circuit oneshot is according to the trailing edge of signal (by extremely low level saltus step of high level saltus step) production burst signal.Certainly, it will be understood by those skilled in the art that also and can be set to in-phase input end by first input end, the second input is set to inverting input, only need to make pulse generation circuit oneshot according to the rising edge production burst signal of signal.
Thereby the 2 of short duration conductings of pulse signal controlled discharge switch S, to charging capacitor C1 electric discharge, make charging capacitor C1 both end voltage v
c1make zero.Meanwhile, pulse signal is applied to the reset terminal of rest-set flip-flop 11b, and rest-set flip-flop 11b is reset, power switch control signal v
gatebecome low level.This low level control power switch S1 turn-offs.
Thus, by the turn-on and turn-off that discharge and recharge power ratio control switch to charging capacitor, the accurately average current of control inputs 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 difference of the LED drive circuit of the LED drive circuit of the present embodiment and the second embodiment is, in the present embodiment, power switch S1 is power transistor M, meanwhile, control circuit 11 ' also comprises that driving slows down circuit 11c and delay circuit delay.
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.Certainly, it will be understood by those skilled in the art that, while adopting different classes of power transistor, above-mentioned annexation may be different.
Driving slows down between the output and power switch control signal output that circuit 11c is connected to described rest-set flip-flop 11b, the power switch control signal v that during for output signal saltus step at described rest-set flip-flop, output gradually changes
gate.
Fig. 5 is the working waveform figure of the LED drive circuit of third embodiment of the invention.As shown in Figure 5, drive slow down circuit 11c can be so that be applied to the power switch control signal v on power transistor M
gateby high level, taper to low level.Accordingly, power switch control signal v
gatetaper in low level process, flow through the drive current I of power transistor M
inreduce gradually to the last vanishing.Also, at the both end voltage v of charging capacitor C1
c1rise to and turn-off threshold value v
offtime, power transistor M does not turn-off at once, but is turned off gradually.
Preferably, it is RC low-pass filter circuit that driving slows down circuit 11c, it comprises and slows down resistance R 1 and slow down capacitor C 2, slow down between the output and power switch control signal output that resistance R 1 is connected to rest-set flip-flop 11b, slow down capacitor C 2 and be connected between described power switch control signal output and ground.Because the electric capacity in RC low-pass filter circuit exists the process discharging and recharging, this time constant discharging and recharging equals the product of RC, and institute, so that signal can not suddenly change, namely makes signal saltus step edge slowly change.Therefore, can be applied to the present embodiment and slow down circuit 11c as driving.
Both end voltage at charging capacitor C1 rises to shutoff threshold value v
offafter a period of time in (t2 ' to t2 during), drive current I
instill non-vanishing, the both end voltage v of charging capacitor C1
c1can be because drive current sampled signal I
scharging and continue to rise.Therefore,, if utilize 2 pairs of capacitor C of pulse signal controlled discharge switch S, 1 electric discharge generating when moment t2 ', can cause circuit misoperation.So need to close the controlled discharge switch S 2 again of having no progeny completely at power transistor M discharges.In the present embodiment, by being set, delay circuit delay pulse signals delay scheduled time realizes this purpose.
Delay circuit dealy is connected between the output of pulse signal generative circuit 11a and the control end of discharge switch S2, for the pulse delay signal scheduled time that pulse signal generative circuit 11a is exported, so that discharge switch S2 closes at power transistor M the conducting again of having no progeny completely.
In the present embodiment, due to power transistor, M turn-offs gradually, drive current I
inbe gradually varied to zero, therefore reduced the current break in circuit, correspondingly can reduce the electromagnetic interference in circuit.
Fig. 6 is the circuit diagram of the LED drive circuit of fourth embodiment of the invention.As shown in Figure 6, the shutoff threshold value v in the present embodiment
offfor following the crest voltage v of charging capacitor C1
peakthe magnitude of voltage changing.
Because driving slows down the existence of circuit 11c, power transistor M can not turn-off completely immediately after the output signal saltus step of comparator C MP, but starts to turn-off gradually.In the process of turn-offing gradually, drive current I
inbe reduced to gradually zero, therefore, the drive current sampled signal I that charging capacitor C1 is still reduced gradually during this period
scharging, its both end voltage v
c1the to the last power transistor M that will rise turn-offs completely.Now, the crest voltage v of charging capacitor C1
peakto be greater than and turn-off threshold value v
off.If follow the crest voltage v of charging capacitor by control
peakthe shutoff threshold value v changing
off, can more accurately control the crest voltage v of charging capacitor C1
peak, constant to guarantee to be input to the current average of LED load in each predetermined clock signal period, improve systematic function.
Particularly, control circuit 11 ' ' also comprise threshold adjustment circuit 11d, for according to the crest voltage v of the charging capacitor C1 of upper one-period
peak-pwith the first predetermined threshold v
ref1relation, to adjust, turn-off threshold value v
off, make the crest voltage v of current period charging capacitor C1
peakequal the first predetermined threshold v
ref1or with respect to the crest voltage v of the charging capacitor C1 of upper one-period
peak-pmore approach the first predetermined threshold v
ref1.This cycle equals the cycle of predetermined clock signal clk.
Preferably, can pass through the first predetermined threshold v
ref1crest voltage v with the charging capacitor C1 of upper one-period
peak-pgenerate and adjust voltage, according to adjusting voltage and the second predetermined threshold v
ref2generate and turn-off threshold value v
off.
Fig. 7 is the circuit diagram of the threshold adjustment circuit of fourth embodiment of the invention.As shown in Figure 7, threshold adjustment circuit 11d comprises peak sampling hold circuit
peak, trsanscondutance amplifier Gm, building-out capacitor C3 and adder Add.
Peak sampling hold circuit
peak is connected to the earth-free one end of charging capacitor C1, input charging capacitor voltage v
c1, in upper one-period to charging capacitor voltage v
c1crest voltage v
peak-psample and keep, in current period, keeping output, also, peak sampling hold circuit
peak sampling charging capacitor voltage v
c1crest voltage within the cycle of a upper predetermined clock signal, and the voltage v equating with this peak value in current period output
peak.This cycle equals the cycle of predetermined clock signal CLK.
The inverting input of trsanscondutance amplifier Gm can with peak sampling hold circuit
peak output connects, and the in-phase input end of trsanscondutance amplifier Gm is inputted the first predetermined threshold v
ref1.
Building-out capacitor C3 is connected between the output and ground of trsanscondutance amplifier Gm.
An input of adder Add is connected with the output of trsanscondutance amplifier Gm, and another input is inputted the second predetermined threshold v
ref2, the output of adder Add turn-offs threshold value v to the second input input of comparator C MP
off.
The second predetermined threshold v
ref2be less than the first predetermined threshold v
ref1.The second predetermined threshold v
ref2with the first predetermined threshold v
ref1be steady state value.
Known according to Fig. 7, turn-off threshold value v
offequal the second predetermined threshold v
ref2with building-out capacitor C3 both end voltage v
c3and, also, v
off=v
ref2+ v
c3.
Crest voltage v as a upper cycle charging capacitor C1
peak-pequal the first predetermined threshold v
ref1time, building-out capacitor C3 both end voltage v now
c3for steady state value, circuit is in steady operation, also, and all can be so that the voltage v of charging capacitor C1 in each clock signal period
c1rise to the first predetermined threshold v
ref1rear decline.
Crest voltage v as a upper cycle charging capacitor C1
peak-pbe greater than the first predetermined threshold v
ref1time, trsanscondutance amplifier Gm output output negative current, makes building-out capacitor C3 both end voltage v
c3reduce, and then turn-off threshold value v
offalso reduce, now to turn-off threshold value v
offvoltage v for the charging capacitor C1 of reference signal
c1also will reduce, the charging interval of charging capacitor C1 will reduce so, and then power transistor M is turn-offed in advance, makes circuit can finally return to stable state.
Crest voltage v as a upper cycle charging capacitor C1
peak-pbe less than the first predetermined threshold v
ref1time, trsanscondutance amplifier Gm output output positive current, makes building-out capacitor C3 both end voltage v
c3increase, and then turn-off threshold value v
offalso increase, now to turn-off threshold value v
offvoltage v for the charging capacitor C1 of reference signal
c1also will increase, the charging interval of charging capacitor C1 will increase so, and then makes power transistor M postpone to turn-off, and makes circuit can finally return to stable state.
In the present embodiment, passing threshold Circuit tuning changes to adjust shutoff threshold value according to the crest voltage of charging capacitor, thereby can realize according to charging capacitor voltage virtual condition, accurately switch-off power transistor.Certainly, those skilled in the art are appreciated that above-mentioned threshold adjustment circuit also can be applied to the circuit of the second embodiment.
Fig. 8 is the flow chart of the LED drive circuit control method of fifth embodiment of the invention.Described in the present embodiment, method is applicable to as above LED drive circuit described in first to fourth embodiment, and also, LED drive circuit is controlled the turn-on and turn-off of the drive current path of driving LED load by power switch, and described method comprises:
Step 810, according to power switch conducting described in predetermined clock signal controlling.
Step 820, the described drive current of sampling generate drive current sampled signal.
Step 830, utilize described drive current sampled signal to charge to charging capacitor, at charging capacitor voltage, rise to and control described power switch while turn-offing threshold value and turn-off.
Preferably, for the electromagnetic interference that reduces to cause due to drive current sudden change, when charging capacitor voltage rises to shutoff threshold value in step 830, control described power switch shutoff and comprise:
The control end voltage of controlling described power switch when charging capacitor voltage rises to shutoff threshold value drops to zero gradually, thereby described power switch is turn-offed gradually.
Preferably, described shutoff threshold value is scheduled voltage; Or
Preferably, described shutoff threshold value is the magnitude of voltage of following the crest voltage variation of described charging capacitor.
By the turn-on and turn-off that discharge and recharge power ratio control switch to charging capacitor, the accurately average current of control inputs load.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, to those skilled in the art, the present invention can have various changes and variation.All any modifications of doing, be equal to replacement, improvement etc., within protection scope of the present invention all should be included within spirit of the present invention and principle.
Claims (10)
1. a LED drive circuit, comprises power switch and control circuit;
Described power switch is for controlling the turn-on and turn-off of the drive current path of driving LED load;
Described control circuit comprises charging capacitor, described control circuit is according to power switch conducting described in predetermined clock signal controlling, and utilize drive current sampled signal to charge to described charging capacitor, when charging capacitor voltage rises to shutoff threshold value, control described power switch and turn-off.
2. LED drive circuit according to claim 1, is characterized in that, described control circuit also comprises drive current sample circuit, discharge switch, comparator, pulse generation circuit and rest-set flip-flop;
Described drive current sample circuit, for to flowing through the drive current sampling of described LED load, generates described drive current sampled signal;
Described discharge switch and charging capacitor are connected in parallel between the first input end and earth terminal of described comparator, and meanwhile, described first input end is connected with the output of described drive current sample circuit;
The second input of described comparator is inputted described shutoff threshold value;
Described pulse generation circuit is connected with the output of described comparator, and for production burst signal when the described comparator output signal saltus step, the output of described pulse generation circuit is connected to the reset terminal of described rest-set flip-flop and the control end of described discharge switch;
The set end of described rest-set flip-flop is inputted described predetermined clock signal, and the output of described rest-set flip-flop is connected to power switch control signal output;
Described power switch control signal output power output switch controlling signal, described power switch control signal is for controlling the turn-on and turn-off of described power switch.
3. LED drive circuit according to claim 2, is characterized in that, described power switch is power transistor, and described control circuit also comprises that driving slows down circuit and delay circuit;
Described driving slows down between the output and described power switch control signal output that circuit is connected to described rest-set flip-flop, for the described power switch control signal that output gradually changes when the output signal saltus step of described rest-set flip-flop, so that conducting or the shutoff gradually of described power transistor;
Described delay circuit is connected between described pulse signal generative circuit output and the control end of described discharge switch, for by the described pulse delay signal scheduled time, so that described discharge switch closes at described power transistor the conducting of having no progeny completely.
4. LED drive circuit according to claim 3, it is characterized in that, described driving slows down circuit and comprises and slow down resistance and slow down electric capacity, described slowing down between the output and described power switch control signal output that resistance is connected to described rest-set flip-flop, described in slow down electric capacity and be connected between described power switch control signal output and described earth terminal.
5. according to the LED drive circuit described in any one in claim 1-4, it is characterized in that, described shutoff threshold value is scheduled voltage; Or
Described shutoff threshold value is the magnitude of voltage of following the crest voltage variation of described charging capacitor.
6. according to the LED drive circuit described in any one in claim 2-4, it is characterized in that, described control circuit also comprises threshold adjustment circuit, be used for according to the relation of the crest voltage of the described charging capacitor of upper one-period and the first predetermined threshold, to adjust described shutoff threshold value, make the crest voltage of the described charging capacitor of current period equal described the first predetermined threshold or more approach described the first predetermined threshold with respect to the crest voltage of the described charging capacitor of upper one-period, the described cycle equals the cycle of described predetermined clock signal.
7. LED drive circuit according to claim 6, is characterized in that, described threshold adjustment circuit comprises peak sampling hold circuit, trsanscondutance amplifier, building-out capacitor and adder;
Described peak sampling hold circuit is inputted described charging capacitor voltage, for obtaining the crest voltage of charging capacitor described in the upper described cycle and keeping, to export within the current described cycle;
The inverting input of described trsanscondutance amplifier is connected with described peak sampling hold circuit output, and the in-phase input end of described trsanscondutance amplifier is inputted described the first predetermined threshold;
Described building-out capacitor is connected between the output and described earth terminal of described trsanscondutance amplifier;
The first input end of described adder is connected with the output of described trsanscondutance amplifier, and the second input is inputted the second predetermined threshold, and the output of described adder is exported described shutoff threshold value to the in-phase input end of described comparator.
8. a LED drive circuit control method, described LED drive circuit is controlled the turn-on and turn-off of the drive current path of driving LED load by power switch, and described method comprises:
According to power switch conducting described in predetermined clock signal controlling;
The described drive current of sampling generates drive current sampled signal;
Utilize described drive current sampled signal to charge to charging capacitor, when charging capacitor voltage rises to shutoff threshold value, control described power switch and turn-off.
9. LED drive circuit control method according to claim 8, is characterized in that, describedly at charging capacitor voltage, rises to and controls described power switch while turn-offing threshold value and turn-off and comprise:
The control end voltage of controlling described power switch when described charging capacitor voltage rises to described shutoff threshold value drops to zero gradually, thereby described power switch is turn-offed gradually.
10. LED drive circuit control method according to claim 8 or claim 9, is characterized in that, described shutoff threshold value is scheduled voltage; Or
Described shutoff threshold value is the magnitude of voltage of following the crest voltage variation of described charging capacitor.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105873305A (en) * | 2015-01-19 | 2016-08-17 | 帝奥微电子有限公司 | Demagnetization testing circuit |
| CN106028557A (en) * | 2016-07-08 | 2016-10-12 | 上海灿瑞科技股份有限公司 | LED constant current driving circuit with high power factor and low total harmonic distortion |
| 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 |
| CN111010769A (en) * | 2019-12-24 | 2020-04-14 | 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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| CN203537625U (en) * | 2013-10-28 | 2014-04-09 | 湖南信息科学职业学院 | Solar semiconductor illumination system |
| CN104080256A (en) * | 2014-07-09 | 2014-10-01 | 无锡硅动力微电子股份有限公司 | Self-adaptation LED current ripple canceling 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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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105873305A (en) * | 2015-01-19 | 2016-08-17 | 帝奥微电子有限公司 | Demagnetization testing circuit |
| CN106028557A (en) * | 2016-07-08 | 2016-10-12 | 上海灿瑞科技股份有限公司 | LED constant current driving circuit with high power factor and low total harmonic distortion |
| 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 |
| CN110446301B (en) * | 2019-08-09 | 2024-05-07 | 上海裕芯电子科技有限公司 | Solar light-operated boost LED functional circuit |
| CN111010769A (en) * | 2019-12-24 | 2020-04-14 | 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 |
| 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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