CN105188197A - LED driving circuit - Google Patents
LED driving circuit Download PDFInfo
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- CN105188197A CN105188197A CN201510498306.9A CN201510498306A CN105188197A CN 105188197 A CN105188197 A CN 105188197A CN 201510498306 A CN201510498306 A CN 201510498306A CN 105188197 A CN105188197 A CN 105188197A
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Abstract
The invention provides an LED driving circuit. The LED driving circuit is characterized by comprising a resonance transformation main circuit and a control circuit. The control circuit comprises a comparison circuit, a setting circuit and a parameter transformation circuit. The control circuit detects output currents and output voltages of the resonance transformation main circuit, superposes the output currents and the output voltages as currently superposed values in the setting circuit, according to the size relation between the currently superposed values and a reference superposed value, decides whether the parameter transformation circuit is at a rapid loop state or a slow loop state, and accordingly controls the response speed of the comparison circuit in outputting control signals. In such a way, when the output currents are quite small and the output voltages are quite low, the resonance transformation main circuit, if entering a hiccup mode, can enable the control circuit to rapidly respond to the output voltages and the output currents of the resonance transformation main circuit so that the hiccup efficiency is improved, current ripples output by the resonance transformation main circuit are reduced, and the stroboscopic or scintillation phenomenon of an LED load connected with an LED driver is solved.
Description
Technical field
The application relates to circuit engineering field, particularly relates to a kind of LED drive circuit.
Background technology
At present, LED is as a kind of novel illuminating device, and the advantages such as, life-span high with its light efficiency is long and pollution-free are extensively promoted in lighting field.In the process using LED, need to use LED driver to carry out driving LED luminescence.Wherein, middle high-power LED driver usually selects high efficiency resonant transformation topology as the conversion of DC/DC current constant control.
LED driver includes resonant transformation main circuit and control circuit.Usually, operating frequency and the LED load of resonant transformation main circuit are changing into inverse ratio, and namely the operating frequency of LED load lighter resonant transformation main circuit is higher.But the operating frequency of resonant transformation main circuit has a switching frequency the highest.When load is reduced to a certain degree gradually, the operating frequency of resonant transformation main circuit can reach the upper limit of the highest switching frequency, continue to raise to prevent the operating frequency of resonant transformation main circuit, control circuit can order about resonant transformation main circuit and be operated in low frequency discontinuous operation pattern, is commonly called as " pattern of having the hiccups "; The discontinuous operation frequency of resonant transformation main circuit, is called frequency of having the hiccups.
Under resonant transformation main circuit is operated in the pattern of having the hiccups of low frequency, namely the frequency of having the hiccups of resonant transformation main circuit is usually lower, the current ripples that this can cause LED driver to export becomes large, and then causes the LED load be connected with LED driver to occur stroboscopic or scintillation.
Summary of the invention
This application provides a kind of LED drive circuit, under the pattern of having the hiccups when LED load is lighter, can improve frequency of having the hiccups, the current ripples that LED driver is exported diminishes, thus the problem of stroboscopic or flicker appears in solution LED load.
To achieve these goals, this application provides following technical scheme:
A kind of LED drive circuit, comprising: resonant transformation main circuit and control circuit;
Wherein, described control circuit comprises: comparison circuit, initialization circuit and parameter transformation circuit;
Described comparison circuit is connected with the output of described resonant transformation main circuit, for receiving the output current of described resonant transformation main circuit, the output current of more described resonant transformation main circuit and reference current, and obtain control signal according to the difference after relatively and export described resonant transformation main circuit to;
The input of described initialization circuit is connected with the output of described resonant transformation main circuit, output is connected with described parameter transformation circuit, for receiving output current and the output voltage of described resonant transformation main circuit, superpose described output current and output voltage is current superposition value, and export the magnitude relationship of described current superposition value and benchmark superposition value to described parameter transformation circuit;
Described parameter transformation circuit is connected with described comparison circuit with described initialization circuit, for when described current superposition value is less than described benchmark superposition value, improve the response speed that described comparison circuit exports described control signal, when described current superposition value is not less than described benchmark superposition value, reduce the response speed that described comparison circuit exports described control signal.
Preferably, also comprise: current sampling circuit;
The input of described current sampling circuit is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit with the input of described comparison circuit, output current for described resonant transformation main circuit of sampling obtains current sampling signal, and described current sampling signal is sent to described comparison circuit and described initialization circuit as output current.
Preferably, also comprise: voltage sampling circuit;
The input of described voltage sampling circuit is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit, output voltage for described resonant transformation main circuit of sampling obtains voltage sampling signal, and described voltage sampling signal is sent to described initialization circuit as output voltage.
Preferably, also comprise: decision circuitry;
The input of described decision circuitry is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit, for receiving the output voltage of described resonant transformation main circuit, when described output voltage is greater than reference voltage, output is greater than the input of signal to described initialization circuit of described benchmark superposition value.
Preferably, described initialization circuit comprises: comparator;
The in-phase input end of described comparator is connected through the forward output of the second resistance with described resonant transformation main circuit, be connected through the negative sense output of the 3rd resistance with described resonant transformation main circuit, or, in-phase input end is through the output of described second resistance and described current sampling circuit, and be connected with the output of described voltage sampling circuit through described 3rd resistance, for inputting the current superposition value of described output current and output voltage;
The inverting input of described comparator accesses described benchmark superposition value;
The output of described comparator is connected with described parameter transformation circuit, for more described current superposition value and described benchmark superposition value, and obtains the second control signal according to the difference relatively and exports.
Preferably, described comparison circuit comprises: the first operational amplifier;
The inverting input of described first operational amplifier is connected through the output of the first resistance with described resonant transformation main circuit output or current sampling circuit;
The in-phase input end of described first operational amplifier accesses described reference current;
The output of described first operational amplifier is connected with described resonant transformation main circuit.
Preferably, described parameter transformation circuit comprises:
First non-controlling end, the second non-controlling and control end;
Described first non-controlling end is connected to the output of described first operational amplifier, and described second non-controlling end is connected to the inverting input of described first operational amplifier;
Described control end is connected with the output of described comparator, for receiving described second control signal, when described second control signal is high level, resistance between two the non-controlling ends controlling described parameter transformation circuit reduces, when described second control signal is low level, the resistance between two the non-controlling ends controlling described parameter transformation circuit increases.
Preferably, described decision circuitry comprises: the second operational amplifier and diode;
The in-phase input end of described second operational amplifier is connected with the output of described resonant transformation main circuit;
The inverting input of described second operational amplifier accesses described reference voltage;
The output of described second operational amplifier connects the positive pole of diode;
The negative pole of described diode is connected with the in-phase input end of described comparator through the 4th resistance.
Preferably, described parameter transformation circuit comprises:
Switching tube;
The control end of described switching tube is connected with the output of described comparator;
Described switching tube is by first end and the second end and the 8th resistant series, and the two ends of described series arm are respectively as described first non-controlling end and the second non-controlling end;
Described 9th resistance two ends are connected with described second non-controlling end respectively at described first non-controlling end;
Described first electric capacity and the tenth resistant series, and the two ends after series connection are connected with described second non-controlling end respectively at described first non-controlling end.
By above-mentioned technology contents, can find out that the application has following beneficial effect:
The application provides the control circuit of LED driver, detect output current and the output voltage of resonant transformation main circuit, and by output current and output voltage superposition in initialization circuit, and as current superposition value, according to the magnitude relationship of current superposition value and benchmark superposition value, determine that parameter transformation circuit is in fast loop state or slow loop line state, and then control the response speed that comparison circuit exports described control signal.
Like this when output current is less and output voltage is lower, if resonant transformation main circuit enters the pattern of having the hiccups, control circuit can be made to respond resonant transformation main circuit output voltage and output current fast, thus improve frequency of having the hiccups, reduce the current ripples that resonant transformation main circuit exports, thus there is stroboscopic or scintillation in the LED load that solution is connected with LED driver.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the application, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
The structural representation of Fig. 1 a kind of LED driver disclosed in the embodiment of the present application;
Fig. 2 is the circuit diagram that the embodiment of the present application discloses a kind of LED driver;
Fig. 3 is the structural representation of the embodiment of the present application another LED driver disclosed;
Fig. 4 is the circuit diagram of the embodiment of the present application another LED driver disclosed;
Fig. 5 is the structural representation of the embodiment of the present application another LED driver disclosed;
Fig. 6 is the circuit diagram of the embodiment of the present application another LED driver disclosed.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present application, be clearly and completely described the technical scheme in the embodiment of the present application, obviously, described embodiment is only some embodiments of the present application, instead of whole embodiments.Based on the embodiment in the application, those of ordinary skill in the art are not making the every other embodiment obtained under creative work prerequisite, all belong to the scope of the application's protection.
As shown in Figure 1, this application provides a kind of LED drive circuit, comprising: resonant transformation main circuit 100 and control circuit 200.Described control circuit 200 comprises: comparison circuit 201, initialization circuit 202 and parameter transformation circuit 203.
Resonant transformation main circuit in the application can be any resonant transform circuit of variable frequency control, as LLC resonant transform circuit, and LCC resonant transform circuit, etc.
Below various piece in control circuit 200 is described in detail:
(1) comparison circuit 201
Described comparison circuit 201 is connected with the output of described resonant transformation main circuit 100, for receiving the output current V1 of described resonant transformation main circuit 100, the output current V1 of more described resonant transformation main circuit 100 and reference current Vr1, and obtain control signal Vc according to the difference after relatively and export described resonant transformation main circuit 100 to.
In order to make resonant transformation main circuit 100 export constant current, closed-loop adjustment mode is adopted to control the output current V1 of resonant transformation main circuit 100.Concrete can be: preset a reference current Vr1, and reference current Vr1 should obtain constant current in theory for LED load 300.Then, the output current V1 of resonant transformation main circuit 100 and reference current Vr1 is compared, and feed back to resonant transformation main circuit 100 according to difference output control signal Vc, described control signal Vc can reflect the magnitude relationship between output current V1 and reference current Vr1, as when output current V1 is higher than reference current Vr1, the control signal Vc that comparison circuit 201 exports will reduce, otherwise, when output current V1 is lower than reference current Vr1, Vc will raise.
Resonant transformation main circuit 100 controls the output current V1 of self according to control signal Vc, is specifically as follows: when control signal Vc raises, and the output current V1 of resonant transformation main circuit 100 increases; When control signal Vc reduces, the output current V1 of resonant transformation main circuit 100 reduces, thus dynamic adjustments resonant transformation main circuit 100 makes it export constant current, then exports constant current to LED load 300.
It should be noted that, the response speed that comparison circuit 201 exports control signal Vc is controlled by parameter transformation circuit 203.When parameter transformation circuit 203 is in fast loop state, then comparison circuit 201 response speed from control signal Vc to resonant transformation main circuit 100 that export is very fast, thus improving the frequency of having the hiccups of resonant transformation main circuit 100, the current ripples that resonant transformation main circuit 100 is exported diminishes.When parameter transformation circuit 203 is in slow loop line state, then comparison circuit 201 response speed from control signal Vc to resonant transformation main circuit 100 that export is slower.
(2) initialization circuit 202
The input of described initialization circuit 202 is connected with the output of described resonant transformation main circuit 100, output is connected with described parameter transformation circuit 203, for receiving output current V1 and the output voltage V2 of described resonant transformation main circuit 100, described output current V1 and output voltage V2 is superposed, using after superposition and as current superposition value Vand, and export the magnitude relationship extremely described parameter transformation circuit 203 of described current superposition value Vand and benchmark superposition value Vr2.
It should be noted that, the benchmark superposition value mentioned in the application, refer to and the reference signal that current superposition value signal Vand compares, but not the superposition of two reference signals.
The size of LED load 300 is the watt level of LED load 300, namely the output current V1 of LED and the product of output voltage V2.When the output current V1 of resonant transformation main circuit 100 and output voltage V2 is larger, the power of LED load 300 is larger, and now, the current superposition value Vand of output current V1 and output voltage V2 is also larger; Output current V1 and output voltage V2 is less, and the power of LED load 300 is less, and the current superposition value Vand of output current V1 and output voltage V2 is also less.Therefore, the variation tendency of current superposition value Vand of output current V1 and output voltage V2 is consistent with the variation tendency of power, so, the current superposition value Vand of output current V1 and output voltage V2 can be adopted, reflect the size of the power of LED load 300 from the side.
When the power of LED load 300 is less, resonant transformation main circuit 100 may be made to enter the pattern of having the hiccups, and frequency of having the hiccups under the pattern of having the hiccups is lower, so, the current ripples that resonant transformation main circuit 100 exports becomes large, and this can cause LED load 300 to occur scintillation.Therefore, preset a benchmark superposition value Vr2, for representing a lower value of the power of LED load 300.
When the output current V1 of resonant transformation the main circuit 100 and current superposition value Vand (i.e. the power of LED load 300) of output voltage V2 is less than benchmark superposition value Vr2, then represent that the power of LED load 300 is less.If under resonant transformation main circuit 100 enters the pattern of having the hiccups in this case, then the current ripples easily causing resonant transformation main circuit 100 to export becomes large.Therefore, in the case, initialization circuit 202 controling parameters varying circuit is in fast loop state, thus control the response speed that comparison circuit 201 exports control signal Vc fast, in this case, even if LED power continues to reduce until enter the pattern of having the hiccups, because loop response speed is fast, the frequency of having the hiccups of resonant transformation main circuit 100 also can be improved; This current ripples that resonant transformation main circuit 100 can be made to export diminishes, thus solves the problem of LED flicker.
When the output current V1 of resonant transformation the main circuit 100 and current superposition value Vand of output voltage V2 is greater than benchmark superposition value Vr2, then represent that the power of LED load 300 is larger; There is no fear of in the case entering the pattern of having the hiccups, also would not occur the problem that LED load 300 is glimmered.So now initialization circuit 202 can be in slow loop line state by controling parameters varying circuit, to ensure the loop stability under resonant transformation main circuit 100 case of heavy load.
(3) parameter transformation circuit 203
Described parameter transformation circuit 203 is connected with described comparison circuit 201 with described initialization circuit 202, for when described current superposition value Vand is less than described benchmark superposition value Vr2, improve the response speed that described comparison circuit 201 exports described control signal Vc, when described current superposition value is not less than described benchmark superposition value Vr2, reduce the response speed that described comparison circuit 201 exports described control signal Vc.
Parameter transformation circuit 203 is controlled by initialization circuit 202, initialization circuit 202 export magnitude relationship be current superposition value Vand be less than benchmark superposition value Vr2 time, then control self to be in fast loop state, to improve the response speed that comparison circuit 201 exports control signal Vc.Initialization circuit 202 export magnitude relationship be current superposition value Vand be not less than benchmark superposition value Vr2 time, control self to be in slow loop line state, to reduce the response speed that comparison circuit 201 exports control signal Vc.
The application provides the control circuit 200 of LED driver, detect output current V1 and the output voltage V2 of resonant transformation main circuit 100, and in initialization circuit 202, obtain the current superposition value Vand of output current V1 and output voltage V2, when current superposition value Vand is less than benchmark superposition value Vr2, determine that parameter transformation circuit 203 is in fast loop state, when fast loop state, the response speed that comparison circuit 201 exports control signal Vc can be improved.
Like this when the output current V1 of resonant transformation main circuit 100 is less and output voltage V2 is lower, if resonant transformation main circuit 100 enters the pattern of having the hiccups, then can make control circuit 200 response resonant transformation main circuit 100 output voltage V2 and output current V1 fast, thus improve frequency of having the hiccups, reduce resonant transformation main circuit 100 output current V1 ripple, and then avoid the LED load 300 be connected with LED driver to occur stroboscopic or scintillation.
It should be noted that, the application, by detecting output current and output voltage switching loop response speed, is therefore applicable to the LED driver that constant voltage exports, is also applicable to the LED driver of constant current output.In the LED driver that constant voltage exports, thereafter level connects LED load, the LED driver that constant voltage exports can be the LED driver of adjustable output voltage, its output current is uncontrollable, when output voltage is very low, parameter transformation circuit can be switched to quick responsive state according to initialization circuit by the technical scheme of the application, to avoid the stroboscopic problem caused of having the hiccups of LED load.The LED driver of tunable optical is the LED driver of constant current output, the output current value of LED driver is changed by dimmer voltage or dim signal, when output current value is very low, parameter transformation circuit can be switched to quick responsive state according to initialization circuit by the technical scheme of the application, to avoid the stroboscopic problem of LED load.
In order to clearly introduce LED driver, introduce the particular circuit configurations of LED driver below in detail.As shown in Figure 2, the physical circuit figure that the LED provided for the application drives.
Wherein, comparison circuit 201 comprises: the first operational amplifier U1;
The inverting input of described first operational amplifier U1 is connected with the output of described resonant transformation main circuit 100 through the first resistance R1;
The in-phase input end of described first operational amplifier U1 accesses described reference current Vr1;
The output of described first operational amplifier U1 is connected with described resonant transformation main circuit 100.
Described initialization circuit 202 comprises: comparator U2;
The in-phase input end of described comparator U2 is connected with the forward output of described resonant transformation main circuit 100 through the second resistance R2, be connected with the negative sense output of described resonant transformation main circuit 100 through the 3rd resistance R3, for inputting the current superposition value Vand of described output current V1 and output voltage V2;
The inverting input of described comparator U2 accesses described benchmark superposition value Vr2;
The output of described comparator U2 is connected with described parameter transformation circuit 203, for more described current superposition value and described benchmark superposition value Vr2, and obtains the second control signal according to the difference relatively and exports.
Described parameter transformation circuit 203 comprises:
First non-controlling end A, the second non-controlling end B and control end C;
Described first non-controlling end A is connected to the output of described first operational amplifier U1, and described second non-controlling end B is connected to the inverting input of described first operational amplifier U1;
Described control end C is connected with the output of described comparator U2, for receiving described second control signal, when described second control signal is high level, the resistance controlled between described parameter transformation circuit 203 two non-controlling end A and B reduces, when described control signal is low level, the resistance controlled between described parameter transformation circuit 203 two non-controlling end A and B increases.
Below various piece in the present embodiment is described in detail:
The output current V1 of resonant transformation main circuit 100 inputs to the inverting input of the first operational amplifier U1 through the V1 in the form of voltage that samples.The in-phase input end of the first operational amplifier U1 accesses the reference current Vr1 of the voltage form preset, and the first operational amplifier exports control signal Vc according to the difference of reference current Vr1 and output current V1.Then control signal Vc is exported to resonant transformation main circuit 100 with the response speed of parameter current translation circuit 203.
Because parameter transformation circuit 203 is parallel to input and the output of comparison circuit 201, so, parameter transformation circuit 203 and comparison circuit 201 composition integrating circuit.The ratio of the resistance between two non-controlling ends of parameter transformation circuit 203 and the first resistance R1 of comparison circuit 201 inverting input is proportionality coefficient, when namely increasing the resistance of non-controlling end two ends resistance of parameter transformation circuit 203, it is faster that comparison circuit 201 exports control signal Vc response speed, so, state larger for the resistance of the non-controlling end two ends resistance of parameter transformation circuit 203 is called fast loop state.When reducing the resistance of the non-controlling end two ends resistance of parameter transformation circuit 203, it is slower that comparison circuit 201 exports control signal Vc response speed, so state less for the resistance of parameter transformation circuit 203 non-controlling end two ends resistance is called slow loop line state.
The height of the resistance of parameter transformation circuit 203 non-controlling end two ends resistance, depends on opening or closing of control end.Control end is in open mode resistance quantity then in parallel to be reduced, so parameter transformation circuit 203 overall resistance of control end is higher; Control end is in closed open state resistance quantity then in parallel to be increased, so parameter transformation circuit 203 overall resistance of control end is lower.Opening or closing the output being controlled by initialization circuit 202 of control end is high level or low level.
Output voltage V2 and output current V1 superposes by the second resistance R2 in initialization circuit 202 and the 3rd resistance R3.Then the output current V1 of voltage form and the output voltage V2 of voltage form is carried out superposition and obtain current superposition value Vand, and by the in-phase input end of current superposition value Vand input comparator U2.The anti-phase input termination benchmark superposition value Vr2 of comparator U2, benchmark superposition value Vr2 are for representing LED load 300 smaller value.
Current superposition value Vand can reflect the watt level of LED load 300 from the side, if when current superposition value is less than benchmark superposition value Vr2, can illustrate that the power of LED load 300 is less.In the lower-powered situation of LED load 300, resonant transformation main circuit may enter the pattern of having the hiccups.Therefore, the output of initialization circuit 202 exports high level, and the control end of controling parameters translation circuit 203 is opened.Now the non-controlling end two ends resistance of parameter transformation circuit 203 is comparatively large, and parameter transformation circuit 203 is in fast loop state, thus controls comparison circuit 201 output control signal Vc fast.
When current superposition value Vand is not less than benchmark superposition value Vr2, can illustrate that the power of LED load 300 is larger.Now resonant transformation main circuit 100 can not enter the pattern of having the hiccups, so, the now output output low level of initialization circuit 202, the control end of controling parameters translation circuit 203 closes, now the non-controlling end two ends resistance of parameter transformation circuit 203 is less, parameter transformation circuit 203 is in slow loop line state, thus control comparison circuit 201 exports control signal Vc at a slow speed.
As shown in Figure 3, this application provides a kind of LED drive circuit, can also comprise: current sampling circuit 204 and voltage sampling circuit 205.
The input of described current sampling circuit 204 is connected with the output of described resonant transformation main circuit 100, output is connected with the input of described initialization circuit 202 with the input of described comparison circuit 201, output current V1 for described resonant transformation main circuit 100 of sampling obtains current sampling signal, and described current sampling signal is sent to described comparison circuit 201 and described initialization circuit 202 as output current V1.
The input of described voltage sampling circuit 205 is connected with the output of described resonant transformation main circuit 100, output is connected with the input of described initialization circuit 202, output voltage V2 for described resonant transformation main circuit 100 of sampling obtains voltage sampling signal, and described voltage sampling signal is sent to described initialization circuit 202 as output voltage V2.
Wherein, the concrete structure of current sampling circuit 204 can be sampling resistor R5.The concrete structure of voltage sampling circuit 205 can be two series resistance R6 and R7.
It should be noted that, the signal of the initialization circuit input in the application, except output current and output voltage directly to superpose and except the output current sampled signal shown in Fig. 3 and the superposition of output voltage sampled signal by direct shown in Fig. 2, can also be the superposition of output current sampled signal and output voltage, compared with benchmark superposition value.
See Fig. 4, introduce the structure chart including current sampling circuit 204 and voltage sampling circuit 205 below.
After increase current sampling circuit 204, the reversed-phase output of comparison circuit 201 is connected with the output of sampling resistor R5 through the first resistance R1, and other annexations of comparison circuit 201 are constant.
The in-phase input end of initialization circuit 202 is connected with the intermediate point of two resistance R6 with R7 of voltage sampling circuit 205 through the second resistance R2, and in-phase input end is connected with the output of sampling resistor R5 through the 3rd resistance R3.Other annexation of initialization circuit 202 is constant.
Compared with Fig. 2, Fig. 4 increase only current sampling circuit 204 and voltage sampling circuit 205, and the annexation of other circuit is all constant, and particular content can participate in Fig. 2, does not repeat them here.
As shown in Figure 5, a kind of LED drive circuit that the application provides, can also comprise: decision circuitry 206.
The input of described decision circuitry 206 is connected with the output of described resonant transformation main circuit 100, output is connected with the input of described initialization circuit 202, for receiving the output voltage V2 of described resonant transformation main circuit 100, when described output voltage V2 is greater than reference voltage V r3, output is greater than the input of signal to described initialization circuit 202 of described benchmark superposition value Vr2.
When the output voltage V2 of resonant transformation main circuit 100 is higher, if resonant transformation main circuit 100 enters fast loop state, then control circuit 200 may be caused to occur unstable problem.Therefore reference voltage V r3 is set, for representing a higher magnitude of voltage.
When the output voltage V2 of resonant transformation main circuit 100 is greater than reference voltage V r3, illustrate that the output voltage V2 of now resonant transformation main circuit 100 is higher.In order to prevent circuit from occurring unstable problem, exporting a high level signal higher than benchmark superposition value Vr2 to initialization circuit 202, thus making initialization circuit 202 controling parameters translation circuit 203 be in slow loop line state.Control circuit 200 can be made like this to be in stable regulation state.
As shown in Figure 6, for comprising the structural representation of decision circuitry 206.
Described decision circuitry 206 comprises: the second operational amplifier U3 and diode D1;
The in-phase input end of described second operational amplifier U3 is connected with the output of described resonant transformation main circuit 100;
The inverting input of described second operational amplifier U3 accesses described reference voltage V r3;
The output of described second operational amplifier U3 connects the positive pole of diode D1;
The negative pole of described diode D1 is connected with the in-phase input end of described comparator U2 through the 4th resistance R4.
Under normal circumstances, when the current superposition value Vand of output voltage V2 and output current V1 is less than benchmark superposition value Vr2, controling parameters translation circuit 203 is answered to be in fast loop state.But at one in particular cases, when namely output voltage V2 is higher than certain value, if comparison circuit 201 fast-response control signal Vc, control circuit 200 can be caused to occur unstable problem.
In order to prevent this problem, set a reference voltage V r3, for judging whether output voltage V2 is greater than reference voltage V r3, when output voltage V2 is greater than reference voltage V r3, no matter now whether the current superposition value of output voltage V2 and output current V1 is less than benchmark superposition value Vr2, equal controling parameters translation circuit 203 is in slow loop line state.
In order to achieve this end, when output voltage V2 is greater than reference voltage V r3, the second operational amplifier U3 exports the value being greater than zero, and this value can drive diode D1 to export a high level signal Vh.In initialization circuit 202, high level signal Vh is greater than benchmark superposition value Vr2, initialization circuit 202 is made to export high level, and then controling parameters translation circuit 203 breaker in middle pipe is opened, the resistance controlled between described parameter transformation circuit 203 two non-controlling end A and B increases, and makes parameter transformation circuit 203 be in slow loop line state.This can be in stable operating state by protecting control circuit 200.
When output voltage V2 is lower than reference voltage V r3, the second operational amplifier U3 output low level, diode ends, thus does not affect the normal work of initialization circuit 202.
Circuit diagram shown in Figure 2, at least comprises a switching tube in the parameter transformation circuit of the application.Opening or closing of switching tube is controlled by initialization circuit, and after switching tube is opened, the overall resistance of parameter transformation circuit increases, and after switching tube closes, the overall resistance of parameter transformation circuit reduces.
Concrete, parameter transformation circuit 203 comprises a switching tube K1;
The control end C of described switching tube K1 is connected with the output of described comparator U2;
Described switching tube K1 is connected with the 8th resistance R8 by first end and the second end, and the two ends of described series arm are respectively as described first non-controlling end A and described second non-controlling end B;
The two ends of described 9th resistance R9 are connected with described second non-controlling end B respectively at described first non-controlling end A;
Described first electric capacity C1 connects with the tenth resistance R10, and the two ends after series connection are connected with described second non-controlling end B respectively at described first non-controlling end A.
The way of realization of the parameter transformation circuit that the application uses can be other arbitrary form, way of realization as shown in Figure 6 or other form, as long as the switching tube meeting parameter transformation circuit can change the overall resistance size of parameter transformation circuit or overall capacitance size.
In this specification, each embodiment adopts the mode of going forward one by one to describe, and what each embodiment stressed is the difference with other embodiment, between each embodiment same or similar part mutually see.
To the above-mentioned explanation of the disclosed embodiments, professional and technical personnel in the field are realized or uses the application.To be apparent for those skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein when not departing from the spirit or scope of the application, can realize in other embodiments.Therefore, the application can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.
Claims (9)
1. a LED drive circuit, is characterized in that, comprising: resonant transformation main circuit and control circuit;
Wherein, described control circuit comprises: comparison circuit, initialization circuit and parameter transformation circuit;
Described comparison circuit is connected with the output of described resonant transformation main circuit, for receiving the output current of described resonant transformation main circuit, the output current of more described resonant transformation main circuit and reference current, and obtain control signal according to the difference after relatively and export described resonant transformation main circuit to;
The input of described initialization circuit is connected with the output of described resonant transformation main circuit, output is connected with described parameter transformation circuit, for receiving output current and the output voltage of described resonant transformation main circuit, superpose described output current and output voltage is current superposition value, and export the magnitude relationship of described current superposition value and benchmark superposition value to described parameter transformation circuit;
Described parameter transformation circuit is connected with described comparison circuit with described initialization circuit, for when described current superposition value is less than described benchmark superposition value, improve the response speed that described comparison circuit exports described control signal, when described current superposition value is not less than described benchmark superposition value, reduce the response speed that described comparison circuit exports described control signal.
2. circuit as claimed in claim 1, is characterized in that, also comprise: current sampling circuit;
The input of described current sampling circuit is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit with the input of described comparison circuit, output current for described resonant transformation main circuit of sampling obtains current sampling signal, and described current sampling signal is sent to described comparison circuit and described initialization circuit as output current.
3. circuit as claimed in claim 2, is characterized in that, also comprise: voltage sampling circuit;
The input of described voltage sampling circuit is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit, output voltage for described resonant transformation main circuit of sampling obtains voltage sampling signal, and described voltage sampling signal is sent to described initialization circuit as output voltage.
4. the circuit as described in claim 1 or 3, is characterized in that, also comprises: decision circuitry;
The input of described decision circuitry is connected with the output of described resonant transformation main circuit, output is connected with the input of described initialization circuit, for receiving the output voltage of described resonant transformation main circuit, when described output voltage is greater than reference voltage, output is greater than the input of signal to described initialization circuit of described benchmark superposition value.
5. circuit as claimed in claim 1, it is characterized in that, described initialization circuit comprises: comparator;
The in-phase input end of described comparator is connected through the forward output of the second resistance with described resonant transformation main circuit, be connected through the negative sense output of the 3rd resistance with described resonant transformation main circuit, or, in-phase input end is through the output of described second resistance and described current sampling circuit, and be connected with the output of described voltage sampling circuit through described 3rd resistance, for inputting the current superposition value of described output current and output voltage;
The inverting input of described comparator accesses described benchmark superposition value;
The output of described comparator is connected with described parameter transformation circuit, for more described current superposition value and described benchmark superposition value, and obtains the second control signal according to the difference relatively and exports.
6. circuit as claimed in claim 5, it is characterized in that, described comparison circuit comprises: the first operational amplifier;
The inverting input of described first operational amplifier is connected through the output of the first resistance with described resonant transformation main circuit output or current sampling circuit;
The in-phase input end of described first operational amplifier accesses described reference current;
The output of described first operational amplifier is connected with described resonant transformation main circuit.
7. circuit as claimed in claim 6, it is characterized in that, described parameter transformation circuit comprises:
First non-controlling end, the second non-controlling and control end;
Described first non-controlling end is connected to the output of described first operational amplifier, and described second non-controlling end is connected to the inverting input of described first operational amplifier;
Described control end is connected with the output of described comparator, for receiving described second control signal, when described second control signal is high level, resistance between two the non-controlling ends controlling described parameter transformation circuit reduces, when described second control signal is low level, the resistance between two the non-controlling ends controlling described parameter transformation circuit increases.
8. circuit as claimed in claim 7, it is characterized in that, described decision circuitry comprises: the second operational amplifier and diode;
The in-phase input end of described second operational amplifier is connected with the output of described resonant transformation main circuit;
The inverting input of described second operational amplifier accesses described reference voltage;
The output of described second operational amplifier connects the positive pole of diode;
The negative pole of described diode is connected with the in-phase input end of described comparator through the 4th resistance.
9. circuit as claimed in claim 7, it is characterized in that, described parameter transformation circuit comprises:
Switching tube;
The control end of described switching tube is connected with the output of described comparator;
Described switching tube is by first end and the second end and the 8th resistant series, and the two ends of described series arm are respectively as described first non-controlling end and the second non-controlling end;
Described 9th resistance two ends are connected with described second non-controlling end respectively at described first non-controlling end;
Described first electric capacity and the tenth resistant series, and the two ends after series connection are connected with described second non-controlling end respectively at described first non-controlling end.
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| CN201510498306.9A CN105188197B (en) | 2015-08-13 | 2015-08-13 | A kind of LED drive circuit |
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| CN201510498306.9A CN105188197B (en) | 2015-08-13 | 2015-08-13 | A kind of LED drive circuit |
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| CN105188197B CN105188197B (en) | 2018-05-01 |
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