CN103687245A - Isolated primary feedback LED (light-emitting diode) driving circuit with PFC (power factor correction) and controller of driving circuit - Google Patents

Abstract

The invention provides an isolated primary feedback LED (light-emitting diode) driving circuit with PFC (power factor correction) and a controller of the driving circuit. The controller comprises a secondary diode conduction time detection module, a first multiplier, an error amplifier, a negative voltage to positive voltage module, a sampling and holding circuit, a second multiplier, a current sensing comparator, a follower, a zero-crossing detection module and a trigger, an input end of the negative voltage to positive voltage module is connected with a feedback port, an input end of the sampling and holding circuit is connected with an output end of the negative voltage to positive voltage module, an output end of the sampling and holding circuit outputs multiplied signals, a first input end of the second multiplier is connected with an output end of the error amplifier, a second input end of the second multiplier receives the multiplied signals, a first input end of the current sensing comparator receives sampled signals, a second input end of the current sensing comparator is connected with an output end of the second multiplier, the follower follows current reference signals, the zero-crossing detection module is used for generating zero-crossing detection signals, and the trigger generates driving signals according to output signals of the current sensing comparator and the zero-crossing detection signals. The complexity and the cost of a system scheme can be reduced, and efficiency can be improved.

Description

The former limit of isolated form feedback is with LED drive circuit and the controller thereof of PFC

Technical field

The present invention relates to a kind of LED drive circuit field, relate in particular to the former limit of a kind of isolated form feedback with the LED drive circuit controller of PFC.

Background technology

At present, a lot of isolated supplies, as charger for mobile phone and high-power LED driver etc., have the function of output constant current because application demand requires circuit conventionally.In addition, in order to alleviate the extent of injury of electric pollution, meet the harmonic standard IEEE555-2 of International Electrotechnical Commission and IEC1000-3-2 etc., above-mentioned isolated supplies also must possess power factor correction (PFC) function.

Single-level power factor correction scheme more conventional in prior art is as follows: by detecting the output current of transformer secondary, after secondary carries out constant current control, through optocoupler feedback, deliver to former limit PFC control circuit.But this scheme, due to the existence of secondary current sample circuit and optocoupler, has increased the complexity of circuit, in addition, because optocoupler exists problem of aging, the stability of circuit and useful life are all under some influence.

For the problems referred to above, in prior art, there is a solution, employing has the control program of the constant current control of former limit and power factor emendation function concurrently, without secondary current sampling and optic coupling element, directly by obtain the information of output current on the former limit of isolating transformer, controlled and realized output constant current, and realize High Power Factor simultaneously, as shown in Figure 1, mainly comprise: the constant current of former limit and pfc controller 10, rectifier bridge 11, input capacitance Cin, transformer T, switching tube Q1, current sample module 12, secondary diode Ds, output capacitance Co.Wherein, the constant current of former limit and pfc controller 10 can be the control chips that can realize above-mentioned output constant current and PFC function in prior art.The index of weighing two most criticals in above-mentioned control program is the High Power Factor of inlet wire current and the constant current accuracy of output current, and especially, owing to adopting former limit to control, the constant current accuracy of output current is not as secondary constant current control.

In prior art, a kind of scheme of output constant current is by simulating secondary current on former limit, secondary output current is simulated out or by the mean value calculation of secondary output current out, then on former limit, carry out constant current control, as shown in Figure 2.Constant-current control circuit shown in Fig. 2 mainly comprises: controller 10, rectifier bridge 11, input capacitance Cin, transformer T, switching tube Q1, sampling resistor Rs, secondary diode Ds, output capacitance Co, resistance R 1, resistance R 2.Wherein, controller 10 comprises: secondary diode current flow time detecting module 101, zero passage detection module 102, multiplier 103, sampling hold circuit 104, error amplifier 105, permanent conducting controller 106, rest-set flip-flop 107 and driver module 108.

Circuit shown in Fig. 2 is sampled and is kept obtaining primary current peak value and corresponding secondary current peak value primary current by sample port CS.During normal work, former limit peak current is I _pK, the ON time T of secondary diode Ds by feedback port FB, detected _oFF1thereby, simulate output current:

$I_{\mathrm{OUT}}=\frac{1}{2}\×n\×I_{\mathrm{PK}}\×\frac{T_{\mathrm{OFF}1}}{T}---\left(1\right)$

Wherein n is the former limit winding Np of transformer T and the turn ratio of secondary winding Ns, and T is switch periods, T _oFF1it is the ON time of secondary diode Ds.

Adopt the method for integration to obtain:

$I_{\mathrm{PK}}\×\frac{T_{\mathrm{OFF}1}}{T}---\left(2\right)$

By loop, control, make:

$I_{\mathrm{PK}}\×\frac{T_{\mathrm{OFF}1}}{T}=\frac{V_{\mathrm{REF}}}{R_s}---\left(3\right)$

Wherein, Rs is the resistance value of sampling resistor Rs, V _rEFfor error transfers to the preset reference voltage V of error amplifier 105 _rEFmagnitude of voltage.

So just can obtain output current:

$I_{\mathrm{OUT}}=\frac{1}{2}\×n\×\frac{V_{\mathrm{REF}}}{R_s}---\left(4\right)$

Yet, in side circuit, because sampling hold circuit 104 exists certain delay time between sample & hold switches, can cause the error of primary current peak value sampling, thereby cause the secondary current and the actual value that simulate to have deviation, and this deviate can change with the magnetizing inductance amount of input voltage vin and transformer T, be relatively difficult to compensation, thereby cause output constant current magnetizing inductance difference different with input voltage, transformer T to change, cause output constant current precision lower.

As shown in Figure 3, to adopt permanent ON time to realize PFC function different from technology before for another kind of scheme of the prior art, and this scheme is to adopt multiplier to realize PFC function.

Furthermore, LED drive circuit shown in Fig. 3 mainly comprise controller 20 and with the main circuit of the isolation structure of its coupling, this main circuit comprises: rectifier bridge 21, the first resistance pressure-dividing network 22, the second resistance pressure-dividing network 23, input capacitance Cin, transformer T(comprise former limit winding Np, secondary winding Ns and auxiliary winding Na), secondary diode Ds, switching tube Q1, sampling resistor Rs and output capacitance Co.

In addition, it is a kind of adaptive negative feedback closed loop control mode that the output constant current of the LED drive circuit shown in Fig. 3 is controlled, be the control that current reference signal vmo is subject to error amplification signal vcomp, and the current reference signal vmo producing can have influence on pulse signal iemu, thereby have influence on error amplification signal vcomp.When external condition changes, for example input voltage changes or output voltage changes, and error amplification signal vcomp also can change, thereby changes the amplitude of current reference signal vmo, after reaching balance, again realizes output constant current through negative feedback; By primary current is followed current reference signal vmo, can realize High Power Factor.

With reference to figure 4, Fig. 4 shows the working signal oscillogram of LED drive circuit shown in Fig. 3, owing to can automatically eliminating deviation, the integrated value of pulse signal iemu on-Line Voltage in the half period equals the integrated value of formula (2) on-Line Voltage in the half period above, from realizing constant current angle, is therefore equivalent.But the drive circuit of the first embodiment does not need, to the maintenance of sampling of former limit peak current, just can directly obtain peak current I _pK, therefore can as in prior art, because sampling keeps module, between sample & hold switches, not exist certain delay time to cause the error of primary current peak value sampling.

But, LED drive circuit shown in Fig. 3 also has obvious shortcoming, need exactly to set up the first resistance pressure-dividing network 22 of being taken advantage of in signal input port VAC and peripheral main circuit, in order to detect input voltage vin, complexity and the cost of system schema can be increased like this, and Efficiency Decreasing can be caused.

Summary of the invention

The technical problem to be solved in the present invention is to provide the former limit of a kind of isolated form feedback with LED drive circuit and the controller thereof of PFC, is conducive to reduce complexity and the cost of system schema, and is conducive to raise the efficiency.

For solving the problems of the technologies described above, the invention provides the former limit of a kind of isolated form feedback with the LED drive circuit controller of PFC, there is sample port, feedback port and driving port, comprising:

Secondary diode current flow time detecting module, its input connects described feedback port, for detection of the secondary diode current flow time;

The first multiplier, its first input end is connected with the output of described secondary diode current flow time detecting module;

Error amplifier, its first input end connects the output of described the first multiplier, and its second input receives default reference voltage;

The negative pressure die block of becoming a full member, its input is connected with described feedback port, in order to the feedback signal that described feedback port is received, carries out polarity conversion;

Sampling hold circuit, the become a full member output of die block of its input and described negative pressure is connected, and what its output output was associated with input signal is taken advantage of signal;

The second multiplier, its first input end connects the output of described error amplifier, and its second input connects the output of described sampling hold circuit;

Electric current induction comparator, its first input end connects described sample port to receive sampled signal, and its second input connects the output of described the second multiplier;

Follower, its input is connected with the output of described the second multiplier, and its output is connected with the second input of described the first multiplier, and the current reference signal that described follower produces described the second multiplier is followed;

Zero passage detection module, its input is connected with described feedback port, and the feedback signal of described feedback port is carried out to zero passage detection to produce zero passage detection signal;

Trigger, be connected with the output of zero passage detection module with described electric current induction comparator, according to the zero passage detection signal of the output signal of described electric current induction comparator and the output of described zero passage detection module, produce and drive signal, this drives signal to export via described driving port;

Wherein, the current reference signal that described the first multiplier is followed output by described secondary diode current flow time and described follower is multiplied by generation pulse signal mutually, described error amplifier carries out error amplification to produce error amplification signal by described pulse signal and default reference voltage, described the second multiplier by described error amplification signal and the described signal multiplication of being taken advantage of to produce described current reference signal.

According to one embodiment of present invention, the described negative pressure die block of becoming a full member comprises:

The first triode, its collector electrode connects the output of current source, its grounded emitter;

The second triode, its base stage connects the base stage of described the first triode, and its emitter connects described feedback port;

Current mirror, its input connects the collector electrode of described the second triode, and its output is via grounding through resistance, and the output of described current mirror is as the become a full member output of die block of described negative pressure.

According to one embodiment of present invention, described sampling hold circuit comprises:

Sampling switch, its first end connects the become a full member output of die block of described negative pressure, and its control end receives described driving signal;

Keep electric capacity, its first end connects the second end of described sampling switch, its second end ground connection, and the second end of described maintenance electric capacity is as the output of described sampling hold circuit.

According to one embodiment of present invention, described LED drive circuit controller also has compensation port, and described compensation port is connected with the output of described error amplifier, and is configured to via building-out capacitor ground connection.

According to one embodiment of present invention, described trigger is rest-set flip-flop, and its RESET input connects the output of described electric current induction comparator, and its set input connects the output of described zero passage detection module, and its output is exported described driving signal.

According to one embodiment of present invention, when external condition changes, described error amplification signal changes, thereby affect the amplitude of described current reference signal, the change of the amplitude of described current reference signal affects described error amplification signal, reaches balance again realize output constant current afterwards through negative feedback.

The present invention also provides the LED drive circuit of the former limit of a kind of isolated form feedback with PFC, comprising:

Controller described in above any one;

With the main circuit of described controller coupling, described main circuit is isolated form structure.

According to one embodiment of present invention, described main circuit comprises:

Transformer, the Same Name of Ends of its former limit winding receives described input signal;

Switching tube, its first end connects the different name end of described former limit winding, and its second end connects the sample port of described controller and via sampling resistor ground connection, its control end connects the driving port of described controller;

The second resistance pressure-dividing network, its input connects the Same Name of Ends of the auxiliary winding of described transformer, and its output connects the feedback port of described controller, the different name end ground connection of described auxiliary winding;

Fly-wheel diode, the different name end of the secondary winding of transformer described in its anodic bonding, the Same Name of Ends ground connection of described secondary winding;

Wherein, the Same Name of Ends of the negative electrode of described fly-wheel diode and described secondary winding is as load incoming end.

According to one embodiment of present invention, the course of work of described LED drive circuit comprises:

Step (1), makes described controller be operated in critical conduction mode;

Step (2), what acquisition was associated with described input signal is taken advantage of signal;

Step (3), described the first multiplier is determined described pulse signal, the pulsewidth of this pulse signal reflects the described secondary diode current flow time, the amplitude reflection primary current signal amplitude of this pulse signal, this pulse signal also reflects output current;

Step (4), described error amplifier compares described pulse signal and default reference voltage, produces error amplification signal;

Step (5), described the second multiplier 205 is according to described signal and the error amplification signal taken advantage of, produce current reference signal consistent with described waveform input signal, that amplitude is controlled by described error amplification signal, this current reference signal further feeds back to described the first multiplier, for generating described pulse signal;

Step (6), the current reference signal vmo obtaining according to described step (5) and the described sampled signal obtaining via described sample port, produce for turn-offing the driving signal of described switching tube;

(7) produce the driving signal for switching tube described in conducting;

(8) repeating said steps (1)-(7), until loop balance.

According to one embodiment of present invention, described main circuit also comprises: output loading, the first end of this output loading connects the negative electrode of described fly-wheel diode, the second end of this output loading connects the Same Name of Ends of described secondary winding, this output loading be output capacitance, LED load or output capacitance with LED load in parallel wherein any one.

According to one embodiment of present invention, described main circuit also comprises:

Rectifier bridge, to AC signal, rectification obtains described input signal;

Input capacitance, its first end connects the positive output end of described rectifier bridge, and its second end connects the negative output terminal of described rectifier bridge.

Compared with prior art, the present invention has the following advantages:

In the LED drive circuit controller of the embodiment of the present invention, adopt multiplier to realize PFC function, the current reference signal that multiplier produces comprises the peak current I in each cycle _pKinformation, without the peak current on sampling resistor is sampled, keep just can directly obtaining peak current I _pK, therefore can as in prior art, because sampling hold circuit exists time delay between sample & hold, not cause the error of primary current peak value sampling.And, LED drive circuit in the embodiment of the present invention obtains associated with input signal being taken advantage of signal by become a full member die block and sampling hold circuit of negative pressure, make controller be taken advantage of signal input port without arranging, simultaneously in LED drive circuit also without the first resistance pressure-dividing network is set, be conducive to reduce complexity and the cost of system schema, and be conducive to raise the efficiency.

Accompanying drawing explanation

Fig. 1 is that in prior art, the constant-current drive circuit schematic diagram with PFC is controlled on a kind of former limit;

Fig. 2 is the electrical block diagram of the constant-current drive circuit that in prior art, a kind of former limit is controlled;

Fig. 3 is that in prior art, the electrical block diagram with the LED drive circuit of PFC is fed back on the former limit of a kind of isolated form;

Fig. 4 is the working signal waveform schematic diagram of LED drive circuit shown in Fig. 3;

Fig. 5 is that the former limit of the isolated form of embodiment of the present invention feedback is with the electrical block diagram of the LED drive circuit of PFC;

Fig. 6 and Fig. 7 are the working signal waveform schematic diagrames of LED drive circuit shown in Fig. 5;

Fig. 8 is the become a full member electrical block diagram of die block and sampling hold circuit of the negative pressure in the embodiment of the present invention.

Embodiment

Below in conjunction with specific embodiments and the drawings, the invention will be further described, but should not limit the scope of the invention with this.

In LED drive circuit shown in Fig. 3, controller 20 need to arrange is taken advantage of signal input port VAC, in main circuit, need to arrange the first resistance pressure-dividing network 22 obtain be associated with input signal Vin taken advantage of signal, complexity and the cost that can increase to a certain extent system schema, cause Efficiency Decreasing.

With reference to figure 5, Fig. 5 shows the circuit structure of the LED drive circuit of the embodiment of the present invention,, controller 20 is wherein taken advantage of signal input port without arranging, in main circuit without the first resistance pressure-dividing network is set.

Furthermore, the LED drive circuit of the present embodiment comprise controller 20 and with the main circuit of the isolation structure of its coupling, this main circuit comprises: rectifier bridge 21, the second resistance pressure-dividing network 23, input capacitance Cin, transformer T(comprise former limit winding Np, secondary winding Ns and auxiliary winding Na), secondary diode Ds, switching tube Q1, sampling resistor Rs and output capacitance Co.

Wherein, controller 20 can have sample port CS, feedback port FB, drive port DR and compensation port COMP.Switching tube Q1 can be for example power MOS switch tube, or other suitable switching devices.

21 couples of AC signal AC of rectifier bridge rectification obtains input signal Vin; The first end of input capacitance Cin connects the positive output end of rectifier bridge 21, and the second end of input capacitance Cin connects the negative output terminal of rectifier bridge 21; The Same Name of Ends of the former limit winding Np of transformer T receives input voltage vin; The first end of switching tube Q1 connects the different name end of former limit winding Np, and its second end connects the sample port CS of controller 20 and via sampling resistor Rs ground connection, its control end connects the driving port DR of controller 20; The different name end of the secondary winding Ns of the anodic bonding transformer T of secondary diode Ds; The input of the second resistance pressure-dividing network 23 connects the Same Name of Ends of auxiliary winding Na, and the output of the second resistance pressure-dividing network 23 connects the feedback port FB of controller 20, the different name end ground connection of auxiliary winding Na; The first end of output capacitance Co connects the negative electrode of secondary diode Ds, and the second end of output capacitance Co connects the Same Name of Ends of secondary winding Ns, and output capacitance Co is configured in parallel with LED load.Wherein, the parallel connection of output capacitance Co and LED load can be collectively referred to as output loading, and certainly, output loading also can only comprise output capacitance Co or LED load.

As a nonrestrictive example, the second resistance pressure-dividing network 23 can comprise resistance R 1 and the resistance R 2 of series connection, wherein the first end of resistance R 1 connects the Same Name of Ends of auxiliary winding Na, the second end of the first end contact resistance R1 of resistance R 2, the second end ground connection of resistance R 2.Voltage signal Va on the auxiliary winding Na of the second 23 pairs of resistance pressure-dividing networks carries out dividing potential drop, obtains feedback signal, and this feedback signal is transferred to the feedback port FB of controller 20.

The control end of switching tube Q1 connects the driving port DR of controller 20, conducting or shutoff under the driving signal controlling that drives port DR output.In addition, the compensation port COMP of controller 20 can be via external building-out capacitor ground connection.

Furthermore, controller 20 can comprise: secondary diode current flow time detecting module 201, zero passage detection module 202, the first multiplier 203, error amplifier 204, the second multiplier 205, follower 206, electric current induction comparator 207, trigger 208, driver module 209, negative pressure become a full member die block 210 and sampling hold circuit 211.

Wherein, the input of secondary diode current flow time detecting module 201 connects feedback port FB, for detection of the ON time of secondary diode Ds, furthermore, obtains the ON time of secondary diode Ds by the feedback signal on detection feedback port FB.

The first input end of the first multiplier 203 is connected with the output of secondary diode current flow time detecting module 201, and the second input of the first multiplier 203 connects the output of follower 206 and follows the current reference signal vmo of output to receive follower 206.The current reference signal vmo that this first multiplier 203 is followed output by the ON time of secondary diode Ds and follower 206 multiplies each other, thereby obtains pulse signal iemu.

The first input end of error amplifier 204 connects the output of the first multiplier 203, and its second input receives default reference voltage V _rEF, error amplifier 204 pulse signals iemu and reference voltage V _rEFcarry out error amplification to produce error amplification signal vcomp.In addition, the output of error amplifier 204 can also be connected with compensation port COMP.

The become a full member input of die block 210 of negative pressure is connected with feedback port FB, in order to the feedback signal that feedback port is received, carries out polarity conversion; The become a full member output of die block 210 of the input of sampling hold circuit 211 and negative pressure is connected, and the output output of sampling hold circuit 211 is taken advantage of signal and transmitted it to the second input of the second multiplier 205.

The first input end of the second multiplier 205 connects the output of error amplifier 204, its second input connects the output of sampling hold circuit 211 and is taken advantage of signal to receive, and the second multiplier 205 is taken advantage of signal multiplication with generation current reference signal vmo with quilt error amplification signal vcomp.This current reference signal vmo transfers to the first multiplier 203 after following via follower 206.

The first input end of electric current induction comparator 207 connects sample port CS to receive sampled signal, and its second input connects the output of the second multiplier 205 with received current reference signal vmo.

The input of zero passage detection module 202 connects feedback port FB, and the feedback signal on feedback port FB is carried out to zero passage detection to produce zero passage detection signal.

Trigger 208 is connected with the output of zero passage detection module 202 with electric current induction comparator 207, according to the zero passage detection signal of the output signal of electric current induction comparator 207 and 202 outputs of zero passage detection module, produce and drive signal, this driving signal is via driving port DR to export the control end of switching tube Q1 to.As a nonrestrictive example, this driving signal can transfer to and drive port DR via driver module 209.

As a nonrestrictive example, trigger 208 can be rest-set flip-flop, and its RESET input R connects the output of electric current induction comparator 207, and its set input S connects the output of zero passage detection module 202, its output output drive signal.

It is different that the permanent ON time of LED drive circuit shown in Fig. 5 and available technology adopting realizes PFC function, and this LED drive circuit is to adopt multiplier to realize PFC function.Furthermore, it is a kind of adaptive negative feedback closed loop control mode that the output constant current of this LED drive circuit is controlled, be the control that current reference signal vmo is subject to error amplification signal vcomp, and the current reference signal vmo producing can have influence on pulse signal iemu, thereby have influence on error amplification signal vcomp.When external condition changes, for example input voltage changes or output voltage changes, and error amplification signal vcomp also can change, thereby changes the amplitude of current reference signal vmo, after reaching balance, again realizes output constant current through negative feedback; By primary current is followed current reference signal vmo, can realize High Power Factor.

Furthermore, when switching tube Q1 conducting, the voltage on auxiliary winding Na is:

$\mathrm{Va}=-\frac{\mathrm{Na}}{\mathrm{Np}}\×\mathrm{Vin}---\left(5\right)$

Wherein, Na is the number of turn of auxiliary winding Na, and Np is the number of turn of former limit winding Np, and Vin is the magnitude of voltage of input signal Vin;

By negative pressure, become a full member after die block 210, the become a full member output voltage v1 of die block 210 of negative pressure is:

$\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="HDA0000445142060000041.png,HDA0000445142060000061.png"\; state="\{\{state\}\}">v</figure-callout>}1=-k\&times;\mathrm{Va}=k\&times;\frac{\mathrm{Na}}{\mathrm{Np}}\&times;\mathrm{Vin}---\left(6\right)$

Wherein k is constant, depends on the negative pressure die block 210 of becoming a full member.

In the time of switching tube Q1 conducting, the output voltage vac=v1 of sampling hold circuit 211; When switching tube Q1 turn-offs, sampling hold circuit 211 maintains voltage before, and its signal waveform schematic diagram as shown in Figure 6 and Figure 7.

With reference to figure 8, in a nonrestrictive example, the negative pressure die block of becoming a full member can comprise: the first triode M1, and its collector electrode connects the output of current source I1, its grounded emitter; The second triode M2, its base stage connects the base stage of the first triode M1, and its emitter connects feedback port FB; Current mirror, its input connects the collector electrode of the second triode M2, and its output is via resistance R 5 ground connection, and the output of this current mirror is as the become a full member output of die block of negative pressure.The mirror image ratio of this current mirror can be for example n:1.

Sampling hold circuit can comprise: sampling switch S1, and its first end connects the become a full member output of die block of negative pressure, and its control end connects and drives port DR to drive signal to receive; Keep capacitor C 1, its first end connects the second end of sampling switch S1, and its second end ground connection keeps the second end of capacitor C 1 as the output of sampling hold circuit.

In conjunction with Fig. 5 and Fig. 8, in switching tube Q1 conducting,

$v2=\frac{\mathrm{Na}}{\mathrm{Np}}\&times;\mathrm{Vin}\&times;\frac{1}{n}\&times;\frac{R5}{R1}---\left(7\right)$

Wherein, the mirror image ratio that n is current mirror, R5 is the resistance value of resistance R 5.

When switching tube Q1 turn-offs, the voltage Va on auxiliary winding Na is positive voltage, so v2=0.

In the time of switching tube Q1 conducting, sampling switch S1 is closed, vac=v2; When switching tube Q2 turn-offs, sampling switch S1 disconnects, and the voltage that keeps capacitor C 1 that sampling switch S1 is turn-offed to front v2 maintains.

Become a full member die block and sampling hold circuit of negative pressure shown in Fig. 9 is only a preferred embodiment, it will be appreciated by those skilled in the art that and can also adopt in actual applications other any suitable circuit structures.

The course of work of the LED drive circuit of above-described embodiment is roughly as follows:

Step (1), makes controller 20 be operated in critical conduction mode;

Step (2), by negative pressure become a full member die block and sampling hold circuit, obtain be associated with input signal taken advantage of signal vac, for example can obtain the waveform of the input signal that rectifier bridge exports;

Step (3), obtains the pulse signal iemu that a pulsewidth reflects secondary diode current flow time, amplitude reflection primary current signal amplitude, this pulse signal reflection output current;

Step (4), the pulse signal iemu obtaining according to step (3), adopts error amplifier 204 and reference voltage V _rEFcompare, produce error amplification signal vcomp;

Step (5), according to step (2), obtain by the error amplification signal vcomp that takes advantage of signal vac and obtain according to step (4), by the second multiplier 205, produce the current reference signal vmo that input signal Vin waveform is consistent, amplitude is controlled by error amplification signal vcomp with rectifier bridge 21 outputs, this current reference signal vmo further feeds back to step (3), production burst signal iemu;

Step (6), the sampled signal of the current reference signal vmo obtaining according to step (5) and the primary current that obtains via sample port CS, produces the driving signal for on-off switching tube Q1;

(7) produce the driving signal for actuating switch pipe Q1;

(8) repeating step (1)-(7), until loop balance.

The above, be only preferred embodiment of the present invention, not the present invention done to any pro forma restriction.Therefore, every content that does not depart from technical solution of the present invention, just according to technical spirit of the present invention to any simple modification made for any of the above embodiments, the conversion that is equal to, all still belong in the protection range of technical solution of the present invention.

Claims (11)

1. the former limit of isolated form feedback, with a LED drive circuit controller of PFC, has sample port, feedback port and driving port, it is characterized in that, comprising:

Secondary diode current flow time detecting module, its input connects described feedback port, for detection of the secondary diode current flow time;

The first multiplier, its first input end is connected with the output of described secondary diode current flow time detecting module;

Error amplifier, its first input end connects the output of described the first multiplier, and its second input receives default reference voltage;

The negative pressure die block of becoming a full member, its input is connected with described feedback port, in order to the feedback signal that described feedback port is received, carries out polarity conversion;

Sampling hold circuit, the become a full member output of die block of its input and described negative pressure is connected, and what its output output was associated with input signal is taken advantage of signal;

The second multiplier, its first input end connects the output of described error amplifier, and its second input connects the output of described sampling hold circuit;

Electric current induction comparator, its first input end connects described sample port to receive sampled signal, and its second input connects the output of described the second multiplier;

Follower, its input is connected with the output of described the second multiplier, and its output is connected with the second input of described the first multiplier, and the current reference signal that described follower produces described the second multiplier is followed;

Zero passage detection module, its input is connected with described feedback port, and the feedback signal of described feedback port is carried out to zero passage detection to produce zero passage detection signal;

Trigger, be connected with the output of zero passage detection module with described electric current induction comparator, according to the zero passage detection signal of the output signal of described electric current induction comparator and the output of described zero passage detection module, produce and drive signal, this drives signal to export via described driving port;

Wherein, the current reference signal that described the first multiplier is followed output by described secondary diode current flow time and described follower is multiplied by generation pulse signal mutually, described error amplifier carries out error amplification to produce error amplification signal by described pulse signal and default reference voltage, described the second multiplier by described error amplification signal and the described signal multiplication of being taken advantage of to produce described current reference signal.

2. the former limit of isolated form according to claim 1 feedback, with the LED drive circuit controller of PFC, is characterized in that, the described negative pressure die block of becoming a full member comprises:

The first triode, its collector electrode connects the output of current source, its grounded emitter;

The second triode, its base stage connects the base stage of described the first triode, and its emitter connects described feedback port;

Current mirror, its input connects the collector electrode of described the second triode, and its output is via grounding through resistance, and the output of described current mirror is as the become a full member output of die block of described negative pressure.

3. the former limit of isolated form according to claim 1 feedback, with the LED drive circuit controller of PFC, is characterized in that, described sampling hold circuit comprises:

Sampling switch, its first end connects the become a full member output of die block of described negative pressure, and its control end receives described driving signal;

Keep electric capacity, its first end connects the second end of described sampling switch, its second end ground connection, and the second end of described maintenance electric capacity is as the output of described sampling hold circuit.

4. according to the former limit of the isolated form described in any one in claims 1 to 3, feed back the LED drive circuit controller with PFC, it is characterized in that, described LED drive circuit controller also has compensation port, described compensation port is connected with the output of described error amplifier, and is configured to via building-out capacitor ground connection.

5. according to the former limit of the isolated form described in any one in claims 1 to 3, feed back the LED drive circuit controller with PFC, it is characterized in that, described trigger is rest-set flip-flop, its the RESET input connects the output of described electric current induction comparator, its set input connects the output of described zero passage detection module, and its output is exported described driving signal.

6. according to the former limit of the isolated form described in any one in claims 1 to 3, feed back the LED drive circuit controller with PFC, it is characterized in that, when external condition changes, described error amplification signal changes, thereby affect the amplitude of described current reference signal, the change of the amplitude of described current reference signal affects described error amplification signal, reaches balance again realize output constant current afterwards through negative feedback.

7. the former limit of isolated form feedback, with a LED drive circuit of PFC, is characterized in that, comprising:

Controller in claim 1 to 6 described in any one;

With the main circuit of described controller coupling, described main circuit is isolated form structure.

8. LED drive circuit according to claim 7, is characterized in that, described main circuit comprises:

Transformer, the Same Name of Ends of its former limit winding receives described input signal;

Switching tube, its first end connects the different name end of described former limit winding, and its second end connects the sample port of described controller and via sampling resistor ground connection, its control end connects the driving port of described controller;

The second resistance pressure-dividing network, its input connects the Same Name of Ends of the auxiliary winding of described transformer, and its output connects the feedback port of described controller, the different name end ground connection of described auxiliary winding;

Fly-wheel diode, the different name end of the secondary winding of transformer described in its anodic bonding, the Same Name of Ends ground connection of described secondary winding;

Wherein, the Same Name of Ends of the negative electrode of described fly-wheel diode and described secondary winding is as load incoming end.

9. LED drive circuit according to claim 8, is characterized in that, the course of work of described LED drive circuit comprises:

Step (1), makes described controller be operated in critical conduction mode;

Step (2), what acquisition was associated with described input signal is taken advantage of signal;

Step (3), described the first multiplier is determined described pulse signal, the pulsewidth of this pulse signal reflects the described secondary diode current flow time, the amplitude reflection primary current signal amplitude of this pulse signal, this pulse signal also reflects output current;

Step (4), described error amplifier compares described pulse signal and default reference voltage, produces error amplification signal;

Step (5), described the second multiplier 205 is according to described signal and the error amplification signal taken advantage of, produce current reference signal consistent with described waveform input signal, that amplitude is controlled by described error amplification signal, this current reference signal further feeds back to described the first multiplier, for generating described pulse signal;

Step (6), the current reference signal vmo obtaining according to described step (5) and the described sampled signal obtaining via described sample port, produce for turn-offing the driving signal of described switching tube;

(7) produce the driving signal for switching tube described in conducting;

(8) repeating said steps (1)-(7), until loop balance.

10. LED drive circuit according to claim 8, it is characterized in that, described main circuit also comprises: output loading, the first end of this output loading connects the negative electrode of described fly-wheel diode, the second end of this output loading connects the Same Name of Ends of described secondary winding, this output loading be output capacitance, LED load or output capacitance with LED load in parallel wherein any one.

11. LED drive circuits according to claim 8, is characterized in that, described main circuit also comprises:

Rectifier bridge, to AC signal, rectification obtains described input signal;

Input capacitance, its first end connects the positive output end of described rectifier bridge, and its second end connects the negative output terminal of described rectifier bridge.

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