CN104202869B - A kind of constant-current control circuit, LED drive circuit and constant current control method - Google Patents
A kind of constant-current control circuit, LED drive circuit and constant current control method Download PDFInfo
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- CN104202869B CN104202869B CN201410387249.2A CN201410387249A CN104202869B CN 104202869 B CN104202869 B CN 104202869B CN 201410387249 A CN201410387249 A CN 201410387249A CN 104202869 B CN104202869 B CN 104202869B
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Abstract
This application provides a kind of constant-current control circuit, LED drive circuit and constant current control method, in described constant-current control circuit, first charging circuit and the second charging circuit all start to charge up when main switch switches to first state, the sampled signal and a reference voltage that characterize inductive current are compared by the first comparison circuit, result of the comparison controls the charging interval of the first charging circuit, more described second charging circuit of second comparison circuit and the charging voltage of the first charging circuit, result of the comparison controls the charging interval of the second charging circuit, the main switch in described LED drive circuit is made to switch to the second state by first state when described second charging circuit stops and charging, LED drive circuit is controlled to export a constant current signal.Therefore, described constant-current control circuit, when realizing current constant control without external sampling resistance sampling LED current, improves the integrated level of LED drive circuit, and has wide range of applications.
Description
Technical field
The present invention relates to a kind of Power Electronic Technique is and in particular to a kind of constant-current control circuit, LED drive circuit and constant current
Control method.
Background technology
Constantly bringing forth new ideas and developing rapidly with illuminating industry, energy-conservation and environmental protection in addition becomes more and more important, and LED illumination is as one
Plant revolutionary energy-saving illumination technology, develop rapidly.However, because the brightness of LED is related to light output intensity parameter,
It is directly proportional to its electric current and forward voltage drop, and varies with temperature and change.Therefore, LED drive circuit needs to produce a perseverance
Determine electric current LED is driven, be also accomplished by a current constant control electricity that LED drive circuit can be controlled to realize constant current output
Road.
A kind of LED drive circuit that Fig. 1 realizes for prior art, described LED drive circuit includes constant-current control circuit 01
With power stage circuit 02.It is provided with main switch S in described power stage circuit 02WWith inductance L；Described constant-current control circuit is used for
Described main switch S is controlled according to the output current feedback signal of LED drive circuitWSwitch motion so that described LED
Drive circuit exports a constant current signal；The feedback signal of described output current passes through a sampling resistor connected with LED load
RsenseObtain, and by output current feedback signal transmission to described control circuit 01, therefore described LED drive circuit also needs to wrap
Including can be by sampling resistor RsenseThe output current sample circuit constituting.
Constant-current control circuit in LED drive circuit as shown in Figure 1, when realizing current constant control, needs using outside
Sampling resistor is come LED current of sampling, and non-essential resistance is not integrated in the chip that described constant-current control circuit is located, so not
Using LED drive circuit system integrated level it is impossible to improve system efficiency.
Content of the invention
In view of this, the present invention provides a kind of constant-current control circuit, LED drive circuit and constant current control method, to solve
Need the LED drive circuit causing by non-essential resistance sampling LED load electric current when realizing current constant control in prior art
The not high problem of the integrated level of system.
A kind of constant-current control circuit, for LED drive circuit, is provided with main switch and electricity in described LED drive circuit
Sense, described constant-current control circuit includes：
Inductive current sample circuit, flows through the inductive current of described inductance for sampling, and exports a described inductance electricity
The sampled signal of stream；
First comparison circuit, for relatively described sampled signal and a reference voltage signal, and exports the first comparison signal；
First charging circuit, including the first electric capacity, the first current source, in first time period, described first current source pair
Described first electric capacity charges；
Second charging circuit, including the second electric capacity, the second current source, in second time period, described second current source pair
Described second electric capacity charges；
Second comparison circuit, for the voltage on the voltage and the second electric capacity on relatively described first electric capacity, and exports the
Two comparison signals；
Pwm signal generation circuit, for pwm signal is generated according to described second comparison signal and one first control signal,
To control described main switch to switch between the first state and a second state, make described LED drive circuit output one permanent
Stream signal；
When described first control signal is effective status, described main switch switches to described first state and described the
One time period and described second time period start simultaneously at generation, when described sampled signal is equal to described reference voltage signal, institute
State first time period to terminate, when the voltage on described second electric capacity is equal to described the one the of described first time period finish time
During voltage on one electric capacity, described second time period terminates and described main switch switches to described second state；
Described first time period terminates before described second time period terminates.
Preferably, described constant-current control circuit, also includes inductive current sample circuit, described inductive current sample circuit with
One end of described inductance is connected, and for described inductive current of sampling, and exports described sampled signal.
Preferably, described constant-current control circuit, also includes pwm signal generation circuit, and described pwm signal generation circuit is used for
Pwm signal is generated according to described second comparison signal and one first control signal, to control described main switch described first
Switch between state and described second state, make described LED drive circuit export a constant current signal, when the described first control
When signal is effective status, described main switch switches to described first state.
Preferably, described first charging circuit also includes first switch, and the two ends of described first switch are respectively with described
The two ends of one electric capacity are connected；
Described second charging circuit also includes second switch, the two ends of described second switch respectively with described second electric capacity
Two ends are connected；
Described first switch and described second switch all turn off, described during described main open pipe is described first state
Main open pipe is conducting during described second state.
Preferably, described first charging circuit also includes the 3rd switch, and described SAN GUAN is connected to described first current source
And described first electric capacity between, described 3rd switch conducting when described first comparison signal is for effective status.
Preferably, described first comparison circuit includes a first comparator, and described second comparison circuit includes one second ratio
Compared with device, described pwm signal generation circuit includes a rest-set flip-flop；
The input in the same direction of described second comparator receives the voltage on described second electric capacity, and backward end receives described first
Voltage on electric capacity, outfan exports described second comparison signal.
Preferably, described first state is conducting state, and described second state is off-state.
Preferably, described first state is off-state, and described second state is conducting state.
Preferably, the in-phase input end of described first comparator receives described reference voltage signal, and reverse input end receives
Described sampled signal, outfan exports described first comparison signal；
The RESET input of described rest-set flip-flop receives described second comparison signal, and set income end receives described first control
Signal processed.
Preferably, the in-phase input end of described first comparator receives described sampling, and reverse input end receives described benchmark
Voltage signal, outfan exports described first comparison signal；
The RESET input of described rest-set flip-flop receives described first control signal, and set income end receives described second ratio
Compared with signal.
A kind of LED drive circuit, including a power stage circuit, is provided with main switch and electricity in described power stage circuit
Sense, also includes above-mentioned any one described constant-current control circuit,
Described constant-current control circuit exports a pwm signal, to control the switch motion of described main switch, makes described LED
Drive circuit exports a constant current signal.
A kind of constant current control method, for LED drive circuit, is provided with main switch and electricity in described LED drive circuit
Sense, methods described includes：
Obtain the sampled signal characterizing the inductive current flowing through described inductance；
When described main switch switches to first state, start with the first electric current, the first electric capacity to be charged, the second electric current
Second electric capacity is charged；
When described sampled signal is equal to a reference voltage signal, stop described first electric capacity is charged；
When the voltage on described second electric capacity is equal on described first electric capacity stopping when described first electric capacity is charged
During voltage, stop described second electric capacity is charged, and control described main switch to switch to the second state by described first state；
The time period that described first electric capacity is charged is designated as first time period；
Time period when described second electric capacity is charged is designated as second time period；
Described first time period terminates before described second time period terminates.
Therefore, using constant-current control circuit provided herein it is only necessary to be filled using the first charging circuit and second
Circuit all starts to charge up when main open pipe switches to first state, is then characterized one using one first comparison circuit and flows through electricity
The sampled signal of inductive current of sense and a reference voltage are compared, and result of the comparison is used for controlling filling of the first charging circuit
Electric time, then the voltage in order to more described second charging circuit of one second comparison circuit and the first charging circuit, the knot comparing
Fruit is used for controlling the charging interval of the second charging circuit, so so that described LED is driven when described second charging circuit stops and charging
Main switch in circuit switches to the second state by first state, thus controlling LED drive circuit to export a constant current signal.Cause
This, the application provide constant-current control circuit when realizing current constant control need not by external sampling resistance come LED current of sampling,
Effectively raise the integrated efficiency of LED drive circuit, and can be applicable in various types of LED drive circuits, range of application
Extensively.
Brief description
In order to be illustrated more clearly that the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing
Have technology description in required use accompanying drawing be briefly described it should be apparent that, drawings in the following description be only this
Inventive embodiment, for those of ordinary skill in the art, on the premise of not paying creative work, can also basis
The accompanying drawing providing obtains other accompanying drawings.
A kind of structure chart of LED drive circuit that Fig. 1 realizes for prior art；
Fig. 2 is a kind of structure chart of constant-current control circuit disclosed in the embodiment of the present application；
Fig. 3 is the structure chart of another kind of constant-current control circuit disclosed in the embodiment of the present application；
Fig. 4 is another kind of constant-current control circuit working waveform figure disclosed in the embodiment of the present application；
Fig. 5 is the structure chart of the embodiment of the present application another constant-current control circuit disclosed；
Fig. 6 is the embodiment of the present application another constant-current control circuit working waveform figure disclosed；
Fig. 7 is a kind of schematic flow sheet of constant current control method disclosed in the embodiment of the present application.
Specific embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete
Site preparation description is it is clear that described embodiment is only a part of embodiment of the present invention, rather than whole embodiments.It is based on
Embodiment in the present invention, it is every other that those of ordinary skill in the art are obtained under the premise of not making creative work
Embodiment, broadly falls into the scope of protection of the invention.
Fig. 2 is a kind of structure chart of constant-current control circuit disclosed in the embodiment of the present application.
Referring to Fig. 2, described constant-current control circuit disclosed in the embodiment of the present application is applied in LED drive circuit, especially suitable
For, in the LED drive circuit of continuous mode, described LED drive circuit includes power stage circuit 02, described power stage circuit 02
In be provided with main switch SWWith inductance L, described constant-current control circuit 01 is used for controlling described main switch SWSwitch motion,
To control described LED drive circuit to export a constant current signal, make LED load normal work.Described constant-current control circuit 01 includes
Inductive current sample circuit 011, the first comparison circuit 012, the first charging circuit 013, the second charging circuit 014, second compare
Circuit 015 and pwm signal generation circuit 016.
Wherein, described inductive current sample circuit 011 is used for the inductive current I that described inductance L is flow through in samplingL, and export
Described inductive current ILSampled signal Vsen；
Described first comparison circuit 012 is used for relatively described sampled signal VsenWith a reference voltage signal VRef,And export
First comparison signal Q1；
Described first charging circuit 013 includes the first electric capacity and the first current source, in first time period, described first electricity
Charge to described first electric capacity in stream source；
Described second charging circuit 014 includes the second electric capacity and the second current source, in described second time period, described
Two current sources charge to described second electric capacity；
Described second comparison circuit 015 is used for comparing the voltage V on described first electric capacityC1With the electricity on described second electric capacity
Pressure VC2, and export the second comparison signal Q2；
Described pwm signal generation circuit is used for according to described second comparison signal Q2With one first control signal VCrGenerate
Pwm signal, to control described main switch SWSwitch between the first state and a second state, make described LED drive electricity
Road exports a constant current signal；
In described first control signal VCrDuring for effective status, described main switch SWSwitch to described first state and institute
State first time period and described second time period all starts to occur, when described sampled signal VsenValue be equal to described reference voltage
During the value of signal, described first time period terminates, the voltage V on described second electric capacityC2Terminate equal to described first time period
The voltage V on described first electric capacity during the momentC1When, described second time period terminates and described main switch switches to described
Two-state；
Described first time period terminates before described second time period terminates.
In constant-current control circuit disclosed in the embodiment of the present application, described first state is in conducting state and off state
One kind, then described second state be conducting state and off state in another kind.With described first state as conducting state,
Described second state is off state, and described first current source is I1, described first electric capacity is C1, described second current source is
I2, described second electric capacity is C2, the topological structure of the power stage circuit 02 of described LED drive circuit is voltage-dropping type, and mode of operation is
Realizing current constant control work process to the constant-current control circuit disclosed in the embodiment of the present application as a example continuous current mode type is：
When described first control signal VCrDuring for effective status, (effective status refers to that the first control signal triggers described master and opens
Close pipe SWState in which when entering conducting state, such as when described first control signal external timing signal, its effective shape
State may refer to the rising edge of described first control signal, when described first control signal is that other can control described main switch
SWDuring the signal of conducting, its effective status can refer to other forms, such as high level etc.), the pwm signal of described control circuit output
Control described main switch SWSwitching-on state, described first time period T1With described second time period T2(in the present embodiment
In and all described first time period is designated as T in all embodiments below1, described second time period is designated as T2) start to occur, this
When, described first current source I1Start to the first electric capacity C1Charge, described second current source I2Start to the second electric capacity C2Charge,
And will now described inductive current ILValue be designated as IL1, and make sampled signal Vsen=k1×IL, k1For downsampling factor, then now adopt
Sample signal Vsen=k1×IL1；
Described main switch SWAfter entering conducting state, described inductive current ILValue by IL1Start to increase, that is, described adopt
Sample signal Vsen=k1×IL1Start to increase, as described inductive current ILValue by IL1Increase IL2When, described sampled signal VsenDeng
In described reference voltage signal Vref, i.e. Vsen=k1×IL2=VrefWhen, described first comparison signal Q1Saltus step, makes described first
Current source I1Stop to described first electric capacity C1Charge, described first time period T1Terminate, and in described main switch SWSwitch to
The voltage V on described first electric capacity is kept before described second stateC1For described first time period T1The voltage of finish time, i.e. VC1
=I1×T1/C1；
Described first time period T1After end, described second time period T2Proceed, described inductive current ILValue by IL2
Continue to increase, described second current source I2Continue to the second electric capacity C2Charge, as the second electric capacity C2On voltage VC2During equal to first
Between section finish time when described in the first electric capacity C1On voltage VC1When, i.e. VC2=I2×(T1+T2)/C2=VC1=I1×T1/C1When,
Described second time period T2Terminate, now described inductive current ILValue by IL2Increase to IL3, the PWM of described control circuit output
Signal controls described main switch SWSwitch to off state, described inductive current ILValue by IL3Begin to decline, until described
The effective status of the first control signal arrives again, described main switch switching-on state again, and a new cycle opens
Begin, according to such working method, go round and begin again, make described main switch SWCut between conducting state and off state
Change, thus described LED drive circuit can be made to export a constant current signal.
By above-mentioned work process it can be deduced that,
Described second time period T2For described main switch SWTime period in the conduction state, that is, its ON time, described
First time period T1For SWA time period in period time in the conduction state, due to VC2=I2×(T1+T2)/C2=
VC1=I1×T1/C1It can be deduced that working as described first current source I1, the second current source I2, the first electric capacity C1With the second electric capacity C2's
After parameter setting is good, after that is, described constant-current control circuit sets, described first time period T1With described second time period T2Between
Proportionate relationship also determined that, i.e. T1/T2=1/N, N have above-mentioned current source and the parameter of electric capacity to determine.Additionally, by above-mentioned
Work process can draw, IL1And IL3It is respectively described master switch SWSwitch periods in the minima of inductive current and
Maximum, and due to inductive current ILIn main switch SWAdvancing the speed during conducting is identical, and remembers described LED drive circuit
Desired output electric current be Io, then described constant-current control circuit can make in the course of the work following equalities set up：
Due in LED drive circuit, in each switch periods, the maximum IL3 of inductive current IL and minima IL1
Difference be referred to as the ripple value of inductive current, this value generally one definite value determining after circuit design is good, and N, and k1
For the definite value of a determination, then can be drawn by above-mentioned formula, as long as according to desired output current Io of LED drive circuit
Size sets the value of suitable reference voltage signal Vref, just can achieve the constant current output of LED drive circuit, to drive LED to bear
Carry normal work.
In the same manner, if in above-described embodiment, described first state is off state, and described second state is conducting state, then
Described second time period T2 is off the time for described master switch SW, as long as the desired output according to described LED drive circuit
Electric current arranges the value of described reference voltage signal Vref, just can control described in the turn-off time section of described main switch SW
LED drive circuit, makes described main switch SW switch between conducting state and off state, thus described LED can be made
Drive circuit exports a constant current signal.
It should be noted that the power stage circuit of the LED drive circuit in the example above explanation is voltage-dropping type, but this Shen
Please can equally be well applied to power circuit for booster type or other types of LED driving electricity by constant-current control circuit disclosed in embodiment
Lu Zhong.For example, if described LED drive circuit is booster type, the meansigma methodss of the inductive current in described LED drive circuit are equal to
The input current Is of described LED drive circuit, due to closing between the input current Is of described LED drive circuit and output current Io
It is to be：Io=Is (1-D), D are the dutycycle of the pwm signal of described constant-current control circuit output, as long as then according to described LED
When the desired output electric current Io of drive circuit sets the value of described reference voltage signal Vref, it is re-introduced into a described pwm signal
Feedback signal being set, for example can make described reference voltage signal for one and institute when forming described reference voltage
State the related voltage of the dutycycle of pwm signal, such setting means is easy to just may be used for a person skilled in the art
It is accomplished in several ways, therefore concrete setting means does not limit in this application.
Therefore, using constant-current control circuit provided herein it is only necessary to be filled using the first charging circuit and second
Circuit all starts to charge up when main open pipe switches to first state, then utilizes inductance electricity described in an inductive current sample circuit
Stream obtains a sampled signal, and is compared described sampled signal and a reference voltage with one first comparison circuit, compares
Result is used for controlling the charging interval of the first charging circuit, then in order to more described second charging circuit of one second comparison circuit and
The voltage of the first charging circuit, result of the comparison is used for controlling the charging interval of the second charging circuit, so in the described second charging
Circuit stops making the main switch in described LED drive circuit switch to the second state by first state, thus controlling when charging
LED drive circuit exports a constant current signal.Therefore, the constant-current control circuit that the application provides need not lead to when realizing current constant control
Cross external sampling resistance come LED current of sampling, effectively raise the integrated efficiency of LED drive circuit, and can be applicable to various
In the LED drive circuit of type, have wide range of applications.
Fig. 3 is the structure chart of another kind of constant-current control circuit disclosed in the embodiment of the present application.
Referring to Fig. 3, in the present embodiment, described constant-current control circuit is applied in LED drive circuit, and described LED drives
In circuit, the power stage circuit 02 of described LED drive circuit is booster type topological structure, is provided with master in described power stage circuit
Switching tube SW and inductance L.In the present embodiment, give inductive current sample circuit 011 in described constant-current control circuit,
One comparison circuit 012, the first charging circuit 013, the second charging circuit 014, the second comparison circuit 015 and pwm signal produce electricity
The concrete form on road 016.
Described inductive current sample circuit 011 includes ratio circuit 0111 and a transfer resistance R1, described ratio circuit
0111 one end being connected with described inductance L and described SW is connected, and by described transfer resistance R1 ground connection, for obtain one with
Flow through the inductive current I of described inductanceLProportional sample rate current Isen, Isen=k0×IL, k0For proportionality coefficient.Sample rate current
IsenBy transfer resistance R1It is converted into a sampled voltage signal Vsen, i.e. Vsen=Isen*R1=k0×IL×R1, by described sampling electricity
Pressure signal VsenOutput is as described inductive current ILSampled signal.
Described first comparison circuit 012 includes first comparator Comp1, and the in-phase input end of first comparator receives one
Reference voltage signal Vref, the reverse input end described sampled voltage signal V of receptionsen, outfan output the first comparison signal Q1.
Described first charging circuit 013 includes the first current source I1, the first electric capacity C1, first switch S1With the 3rd switch S3.
First current source I1By the 3rd switch S3With the first electric capacity C1One end be connected, the first electric capacity C1The other end is grounded, and described first
Switch S1Two ends respectively with described first electric capacity C1Two ends be connected.Described first switch S1By switch controlling signal Q3Control,
Switch controlling signal Q3The pwm signal that can export for described constant-current control circuit can also be same with described pwm signal for one
The signal of step, the 3rd switch S3By described first comparison signal Q1Control.
Described first charging circuit 014 includes the second current source I2, the second electric capacity C2With second switch S2.Second current source
I2With the second electric capacity C2One end be connected, the second electric capacity C2The other end is grounded, described second switch S2Two ends respectively with described
Two electric capacity C2Two ends be connected.Described second switch S2With described first switch S1On off state identical, also can be controlled by switch
Signal Q processed3Control.
Described second comparison circuit 015 includes the second comparator Comp2, the input in the same direction of the second comparator Comp2 with
The ungrounded end of described second electric capacity C2 is connected, to receive described second electric capacity C2On voltage VC2, reverse input end with described
First electric capacity C1Ungrounded end be connected, to receive described first electric capacity C1On voltage VC1, outfan output second compares letter
Number Q2.
Described pwm signal generative circuit 016 includes a rest-set flip-flop, and the set end of described rest-set flip-flop receives one first control
Signal processed, described first control signal can also can trigger described main switch entrance for other for external timing signal and lead
The signal of logical state, in the present embodiment for an external timing signal CLK, when the rising edge of external timing signal CLK arrives
When, show that external timing signal CLK is in effective status, start to trigger described main switch SWEnter conducting state；Described RS
The reset terminal of trigger receives described comparison signal Q2, outfan exports for controlling described main switch SWSwitch motion
Pwm signal.
In the present embodiment, described first current source I1Electric current and the first electric capacity C1Capacitance ratio be described second electricity
Stream source I2Electric current and the second electric capacity C2The ratio of capacitance twice, i.e. I1/C1=2 × I2/C2, that is, in the present embodiment, T1=
T2/2.
Fig. 4 is the working waveform figure of the constant-current control circuit disclosed in the present embodiment.
With reference to Fig. 4, in t0Moment：The rising edge of external timing signal CLK arrives, and makes the pwm signal that rest-set flip-flop exports
Saltus step is high level, controls described main switch SWEnter conducting state, inductive current ILValue start by IL1Rise, then sample
Voltage signal VsenAlso begin to rise, and now, first switch S2With second switch S2Disconnect, the 3rd switch S3Conducting, the first electricity
Stream source I1With the second current source I2Start respectively to the first electric capacity C1With the second electric capacity C2Charge.Due to I1/C1=2 × I2/C2, the
The voltage V of one electric capacity C1C1(the solid line indicating section in Fig. 4) compares the voltage V of the second electric capacity C2C2(the dotted line instruction unit in Fig. 4
Point) increase fast.In t1Moment, inductive current ILValue rise to IL2, now VsenEqual to Vref, the first comparison signal Q1Saltus step
During low level (in the present embodiment, the effective status of described first comparison signal is high level, and disarmed state is low level, when
So do not limit to such definition), the 3rd switch S3Disconnect, the first current source I1Stop to the first electric capacity C1Charge, VC1In S1Before conducting
Keep constant.From t0To t1Time period be first time period T1, hereafter, the second current source I2Continue to the second electric capacity C2Charge,
Until t2Moment, VC2=VC1, the second comparison signal Q2Saltus step is high level, and the pwm signal saltus step of rest-set flip-flop output is low electricity
Flat, control described main switch SWEnter off state, second time period T2Terminate, now inductive current ILValue rise to IL3,
And start by IL3Decline, until the rising edge of external timing signal CLK arrives again, enter new switch periods.
In the present embodiment, constant-current control circuit is realized the principle of constant-current control circuit and is basically the same as those in the first embodiment, and here is not
It is further continued for illustrating.This enforcement is only through setting the design parameter in the first charging circuit and the second charging circuit, during by first
Between section T1With second time period T2Ratio value be defined as 1：2, i.e. T1/T2=1/2, by be inferred in first embodiment
Formula can draw, in the present embodiment, Vref=Is×k0×R1, IsFor the input current of described LED drive circuit, itself and LED
Output current I of drive circuitoBetween relation be：Is(1-D)=Io, wherein D is the dutycycle of described pwm signal, then Vref
=Io×k0×R1/(1-D).Because circuit is after designing, k0, R1It is the fixed number of determination, as long as then according to desired
Output current IoSize set reference voltage signal VrefValue when, be re-introduced into the feedback signal of pwm signal, make reference voltage
Signal VrefAlso related to the dutycycle of pwm signal, and described LED drive circuit output can be made to meet the perseverance of loading demand
Stream signal, implements setting reference voltage signal VrefThe circuit form of value can be various, and here no longer describes in detail.
Fig. 5 is the structure chart of the embodiment of the present application another constant-current control circuit disclosed.
With reference to Fig. 5, in the constant-current control circuit application LED drive circuit in the present embodiment, described LED drive circuit with upper
Unlike in one embodiment, its power stage circuit 02 is buck topology structure.Described constant-current control circuit and a upper enforcement
Essentially identical in example, different is only that in the present embodiment, the receiving voltage of input in the same direction of first comparator Comp1 is adopted
Sample signal Vsen, reverse input end reception reference voltage signal Vref, and reset terminal reception first control signal of rest-set flip-flop,
Reset terminal receives the second comparison signal.
Fig. 6 is the working waveform figure of the constant-current control circuit of the present embodiment, with reference to Fig. 6, it is known that in the present embodiment,
When first control signal is effective status, main switch SWSwitch to off state, adjust during the off state of main switch
The output current of section LED drive circuit, and above and in embodiment, when the first control signal is effective status, main switch SWCut
Shift to conducting state, the output current of LED drive circuit for adjusting during the conducting state of main switch.Therefore, the present embodiment
In the control process of constant-current control circuit all identical with a upper embodiment with control principle, here is no longer repeated in detail.
T in each embodiment above-mentioned1Represent described first time period T1Duration, T2Represent described second time period T2's
Duration, I1Represent described first current source I1Size of current, I2Represent described second current source I2Size of current, C1Represent institute
State the first electric capacity C1Capacitance, C2Represent described second electric capacity C2Capacitance.
The constant-current control circuit being proposed corresponding to each embodiment above-mentioned, the application also proposed a kind of LED and drives electricity
Road, described LED drive circuit includes any one constant-current control circuit in power stage circuit and above-mentioned each fact Example, described power
It is provided with main switch and inductance, described constant-current control circuit exports a pwm signal, to control described main switch in level circuit
Switch motion, make described LED drive circuit export a constant current signal.
It should be noted that the mode of operation of described LED drive circuit can but be not limited to continuous current mode formula mould
Formula, and the topological structure of described power stage circuit can be booster type, voltage-dropping type or other any kind of topological structure.This Shen
, when realizing constant current output, it is simple to have a control circuit for the LED drive circuit please being provided, and integrated level is high and output current ripple
Little characteristic.
Fig. 7 is a kind of schematic flow sheet of constant current control method disclosed in the embodiment of the present application.
The constant current control method providing with reference to Fig. 7, the present embodiment, is applied in LED drive circuit, and described LED drives electricity
It is provided with main switch and inductance in road, the method comprising the steps of：
Step 701：Obtain the sampled signal characterizing the inductive current flowing through described inductance.
Step 702：When described main switch switches to first state, start with the first electric current, the first electric capacity to be charged,
Second electric current charges to the second electric capacity.
Step 703：When described sampled signal is equal to a reference voltage signal, stop described first electric capacity is charged.
Step 704：When the voltage on described second electric capacity is equal to the voltage on described first electric capacity, stop to described the
Two electric capacity charge.
Step 705：Described main switch is controlled to switch to the second state by described first state.
Wherein, the time period that described first electric capacity is charged is designated as first time period, described second electric capacity will be charged
When time period be designated as second time period, and so that described first time period is terminated before described second time period terminates.
Described first state is conducting state, and described second state is off state it is also possible to make the described first state be
Off state, described second state is conducting state.
The constant current control method that the present embodiment provides is applied in LED drive circuit, can make LED drive circuit output expectation
Output current, to drive LED load normal work, and the constant current control realized using constant current control method provided herein
Circuit processed need not be sampled inductive current using non-essential resistance when realizing current constant control, substantially increases LED drive circuit
Integrated level.
In this specification, each embodiment is described by the way of going forward one by one, and what each embodiment stressed is and other
The difference of embodiment, between each embodiment same or similar partly mutually referring to.
Described above to the disclosed embodiments, makes professional and technical personnel in the field be capable of or uses the present invention.
Multiple modifications to these embodiments will be apparent from for those skilled in the art, as defined herein
General Principle can be realized without departing from the spirit or scope of the present invention in other embodiments.Therefore, the present invention
It is not intended to be limited to the embodiments shown herein, and be to fit to and principles disclosed herein and features of novelty phase one
The scope the widest causing.
Claims (12)
1. a kind of constant-current control circuit, for LED drive circuit, is provided with main switch and inductance in described LED drive circuit,
Described constant-current control circuit includes：
First comparison circuit, flows through the sampled signal of inductive current and the reference voltage letter of described inductance for comparing a sign
Number, and export the first comparison signal；
First charging circuit, including the first electric capacity, the first current source, in first time period, described first current source is to described
First electric capacity charges；
Second charging circuit, including the second electric capacity, the second current source, in second time period, described second current source is to described
Second electric capacity charges；
Second comparison circuit, for the voltage on the voltage and the second electric capacity on relatively described first electric capacity, and exports the second ratio
Compared with signal；
When described main switch switches to first state, described first time period and described second time period start simultaneously at and send out
Raw, when described sampled signal is equal to described reference voltage signal, described first time period terminates, when on described second electric capacity
When voltage is equal to the voltage on described first electric capacity of described first time period finish time, described second time period terminates and institute
State main switch and switch to the second state；
Described first time period terminates before described second time period terminates.
2. constant-current control circuit according to claim 1 is it is characterised in that also including inductive current sample circuit, described
Inductive current sample circuit is connected with one end of described inductance, for described inductive current of sampling, and exports described sampled signal.
3. constant-current control circuit according to claim 2 is it is characterised in that also including pwm signal generation circuit, described
Pwm signal generation circuit is used for generating pwm signal according to described second comparison signal and one first control signal, described to control
Main switch switches between described first state and described second state, makes described LED drive circuit export a constant current
Signal, when described first control signal is effective status, described main switch switches to described first state.
4. constant-current control circuit according to claim 3 is it is characterised in that described first charging circuit also includes first opens
Close, the two ends of described first switch are connected with the two ends of described first electric capacity respectively；
Described second charging circuit also includes second switch, the two ends of described second switch respectively with described second electric capacity two
End is connected；
Described first switch and described second switch all turn off during described main open pipe is described first state, open in described master
Turn on during managing as described second state.
5. constant-current control circuit according to claim 4 is it is characterised in that described first charging circuit also includes the 3rd opens
Close, described 3rd switch is connected between described first current source and described first electric capacity, and the described 3rd switchs described first
Comparison signal is for turning on during effective status.
6. constant-current control circuit according to claim 5 is it is characterised in that described first comparison circuit includes one first ratio
Compared with device, described second comparison circuit includes one second comparator, and described pwm signal generation circuit includes a rest-set flip-flop；
The input in the same direction of described second comparator receives the voltage on described second electric capacity, and backward end receives described first electric capacity
On voltage, outfan export described second comparison signal.
7. constant-current control circuit according to claim 6 is it is characterised in that described first state is conducting state, described
Second state is off-state.
8. constant-current control circuit according to claim 6 is it is characterised in that described first state is off-state, described
Second state is conducting state.
9. constant-current control circuit according to claim 6 is it is characterised in that the homophase input of described first comparator terminates
Receive described reference voltage signal, reverse input end receives described sampled signal, outfan exports described first comparison signal；
The RESET input of described rest-set flip-flop receives described second comparison signal, and set income end receives described first and controls letter
Number.
10. constant-current control circuit according to claim 8 is it is characterised in that the in-phase input end of described first comparator
Receive described sampling, reverse input end receives described reference voltage signal, outfan exports described first comparison signal；
The RESET input of described rest-set flip-flop receives described first control signal, and set income end receives described second and compares letter
Number.
A kind of 11. LED drive circuits, including a power stage circuit, are provided with main switch and inductance in described power stage circuit,
It is characterized in that, also include such as described constant-current control circuit any one in claim 1-10,
Described constant-current control circuit exports a pwm signal, to control the switch motion of described main switch, so that described LED is driven
Circuit output one constant current signal.
A kind of 12. constant current control methods, for LED drive circuit, are provided with main switch and electricity in described LED drive circuit
Sense, methods described includes：
Obtain the sampled signal characterizing the inductive current flowing through described inductance；
When described main switch switches to first state, start with the first electric current, the first electric capacity to be charged, the second electric current is to
Two electric capacity charge；
When described sampled signal is equal to a reference voltage signal, stop described first electric capacity is charged；
When the voltage on described second electric capacity is equal to the voltage on described first electric capacity stopping when described first electric capacity is charged
When, stop described second electric capacity is charged, and control described main switch to switch to the second state by described first state；
The time period that described first electric capacity is charged is designated as first time period；
The time period that described second electric capacity is charged is designated as second time period；
Described first time period terminates before described second time period terminates.
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| CN105657899B (en) * | 2016-02-22 | 2017-12-05 | 南京矽力杰半导体技术有限公司 | Multipath LED constant current drive circuit and its control method |
| CN107306466B (en) * | 2016-04-22 | 2019-05-07 | 美芯晟科技（北京）有限公司 | Adjusting control circuit for LED driver |
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| CN101534587A (en) * | 2009-03-27 | 2009-09-16 | 陕西科技大学 | Commercial power LED constant current driver |
| US20130127356A1 (en) * | 2009-11-25 | 2013-05-23 | Murata Manufacturing Co., Ltd. | Led driving power supply apparatus and led lighting apparatus |
| CN103260318A (en) * | 2013-05-30 | 2013-08-21 | 矽力杰半导体技术(杭州)有限公司 | LED drive circuit capable of adjusting light and light adjusting method thereof |
| CN103813587A (en) * | 2014-01-22 | 2014-05-21 | 长安大学 | LED drive circuit with digital-analog hybrid dimming function |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101534587A (en) * | 2009-03-27 | 2009-09-16 | 陕西科技大学 | Commercial power LED constant current driver |
| US20130127356A1 (en) * | 2009-11-25 | 2013-05-23 | Murata Manufacturing Co., Ltd. | Led driving power supply apparatus and led lighting apparatus |
| CN103260318A (en) * | 2013-05-30 | 2013-08-21 | 矽力杰半导体技术(杭州)有限公司 | LED drive circuit capable of adjusting light and light adjusting method thereof |
| CN103813587A (en) * | 2014-01-22 | 2014-05-21 | 长安大学 | LED drive circuit with digital-analog hybrid dimming function |
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