CN102202449A - LED driving control circuit and method - Google Patents

Abstract

The invention discloses an LED driving control circuit and a method. The LED driving control circuit comprises a voltage comparison module, an output current threshold control module and an LED driving module, wherein the voltage comparison module is used for generating a comparison signal PWM (Pulse-Width Modulation) and providing the comparison signal PWM to the output current threshold control module and the LED driving module; the output current threshold control module is used for generating current threshold control signal IREF/VREF (Input Reference/Voltage Reference) to the LED driving module according to the duty factor of the comparison signal PWM; and the LED driving module is used for generating an LED driving control signal according to the input current threshold control signal IREF/VREF and the comparison signal PWM. The product of the duty factor of the current threshold control signal IREF/VREF and the duty factor of the comparison signal PWM is a constant so that average current output by the LED driving control circuit is equal under the comparison signal PWM of different duty factors. According to the invention, the influence of the overlarge current change of an LED lamp when a commercial power is changed can be solved; output current can be set conveniently; and the flickering problem of the LED lamp resulted from the current change is solved.

Description

LED Drive and Control Circuit and method

Technical field

The present invention relates to the led drive circuit field, relate in particular to and adopt electronic transformer as the led drive circuit technology of power supply for the power supply of LED lamp.

Background technology

Led drive circuit, particularly high-power LED drive circuit comparatively have been widely used in fields such as shot-light, Landscape Lighting, automotive lighting, fluorescent lamp.Traditional Halogen lamp LED power consumption is big, and the life-span is short, and pollution is arranged, and therefore in recent years, replacing Halogen lamp LED with the LED lamp is a kind of trend.

Because traditional Halogen lamp LED electronics transformer-supplied, the Halogen lamp LED that the output of electronic transformer is used for resistance characteristic is a kind of good selection, if but the LED lamp is replaced Halogen lamp LED, then needing to solve electronic transformer is the problem of LED power supply as power supply.

Fig. 1 is the traditional electronic transformer LED drive system schematic diagram as power supply, comprises electronic transformer, rectifier module D 1～D4, filter capacitor C2, LED Drive and Control Circuit 10, peripheral circuit 20 and LED lamp.

Fig. 2 is traditional electronic transformer as the LED Drive and Control Circuit of the power supply schematic diagram with peripheral circuit, and circuit structure adopts the buck pattern.

Peripheral circuit 10 shown in Figure 2 comprises inductance L 1, voltage stabilizing didoe D5, output capacitance C1, output sampling resistor Rs and LED lamp string, annexation is: the DC input voitage VIN behind the rectifying and wave-filtering connects an end of capacitor C 1, an end of inductance L 1, negative pole and the VIN end of LED Drive and Control Circuit 20, the positive pole of an other termination voltage stabilizing didoe D1 of inductance L 1 and the SW of LED Drive and Control Circuit 20 end of LED lamp string.The negative pole of voltage stabilizing didoe D5, the other end of output capacitance C1, the end of output sampling resistor Rs, the SENSE+ of LED Drive and Control Circuit 20 connect, and the positive pole of the other termination LED lamp string of output sampling resistor Rs, SENSE one end of LED Drive and Control Circuit 20 link to each other.

Described LED Drive and Control Circuit (20) comprising: SENSE one end links to each other with the negative terminal of error amplifier 201, the SENSE+ end links to each other with an end of resistance R 201, the other end of R201 and the anode and the fixed threshold of error amplifier 201 are provided with module 202, the output of error amplifier 201 links to each other with the negative terminal of comparator 205, the anode of comparator 205 links to each other with the output of slope-compensation module 209, the input of slope-compensation module 209 is respectively the output of oscillator 204 and the output of amplifier 208, the S end of rest-set flip-flop 206 is received in the another one output of oscillator 204, the output of comparator 205 links to each other with the R end of rest-set flip-flop 206, the output of rest-set flip-flop 206 links to each other with the input of driver module 207, the output of driver module 207 links to each other with the grid of metal-oxide-semiconductor M1, the source electrode of metal-oxide-semiconductor M1 links to each other with an end of resistance R 202, and link to each other with the anode of sampling amplifier 208, an other end of resistance R 202 links to each other with ground, and link to each other with the negative terminal of sampling amplifier 208, the drain electrode of M1 connects the SW end of LED Drive and Control Circuit 20, LED Drive and Control Circuit 20) the VIN port connect an end of internal reference 203.

Civil power AC180～265V power supply provides power supply for electronic transformer, and electronic transformer is converted into the voltage that exchanges AC 12V with civil power, and the voltage that exchanges AC 12V carries out rectification by rectifier module D 1～D4, and the later voltage of rectification passes through filter capacitor C2 filtering.Ideally, filter capacitor C2 is big more, and the ripple voltage of input voltage VIN is more little, but because the volume restrictions of Lamp cup, filter capacitor C2 can not get too big, generally selects the electric capacity of 330uF or 220uF.Even the ripple voltage of input voltage VIN is still very big like this, ripple voltage is minimum can to hang down below the 4V the highest can be up to about 17V.And under same line voltage, the low-voltage of ripple voltage and high-tension pressure reduction can reach more than the 6V.

Input voltage VIN voltage is given the power supply of LED Drive and Control Circuit, and the LED Drive and Control Circuit connects the LED that will be connected in series, and can select 3 * 1W in the general Lamp cup, or the LED lamp of 4 * 1W.LED Drive and Control Circuit I1 can use traditional decompression mode or buck pattern when driving 3 * 1W, adopt the buck pattern during 4 * 1W basically, can adopt boost mode under the partial condition.But no matter adopt which kind of pattern, when 180～265V changed, the output current of LED all can have very big variation at civil power AC, and also can occur the phenomenon of LED lamp flicker under power network fluctuation.Principle is: under different line voltages, as civil power AC when 180～265V changes, the output voltage waveforms of electronic transformer changes, civil power AC voltage is high more, and output voltage is also just high more, and the LED Drive and Control Circuit has minimum operating voltage, when the output voltage of electronic transformer is lower than the minimum operating voltage of LED Drive and Control Circuit, electric current on the LED lamp is zero, and when output voltage was higher than the minimum operating voltage of LED drive controlling chip, the electric current on the LED lamp was a set point.Because civil power AC voltage is when 180～265V changes, the electronic transformer output voltage is higher than the time meeting difference of the minimum operating voltage of LED Drive and Control Circuit, therefore in the cycle of every 10ms, the asynchronism(-nization) of the operate as normal of LED Drive and Control Circuit can cause electric current to alter a great deal.When 180～265V change in voltage, the output current on the LED of the LED Drive and Control Circuit of general decompression mode can change more than 40%; When 180～265V changed, the output current on the LED of the LED Drive and Control Circuit of buck pattern can change more than 30%.This current characteristics is for illuminator, is unfavorable for design, and also there is certain influence in the life-span of LED etc., and is prone to flicker when power network fluctuation.

Summary of the invention

The present invention is intended to solve the deficiencies in the prior art, provide a kind of and change the LED Drive and Control Circuit that scintillation not quite, can not occur at civil power output current when 180V～265V changes, this circuit is applicable to adopting electronic transformer to give the LED driving control device of LED lamp power supply as power supply.

The present invention simultaneously also provides the control method of LED Drive and Control Circuit.

The LED Drive and Control Circuit comprises:

Voltage comparison module, the dividing potential drop of described voltage comparison module input voltage VIN or DC input voitage VIN, to compare with dividing potential drop first reference voltage and second reference voltage of input voltage VIN or DC input voitage VIN, produce a comparison signal PWM and offer output current threshold value control module and LED driver module, described first reference voltage is greater than second reference voltage;

Output current threshold value control module, described output current threshold value control module produces current threshold control signal IREF/VREF to the LED driver module according to the duty ratio of the comparison signal PWM of input;

The LED driver module, described LED driver module produces the LED drive control signal according to the described current threshold control signal IREF/VREF and the comparison signal PWM of input;

After the LED Drive and Control Circuit enters operate as normal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during greater than first reference voltage, the LED drive control signal of the comparison signal PWM control LED driver module output of voltage comparison module output is the LED Continuity signal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during less than second reference voltage, the LED drive control signal of the comparison signal PWM control LED driver module output of voltage comparison module output is the LED cut-off signals, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED Drive and Control Circuit output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

Further, described LED driver module comprises:

Error amplifier, described current threshold control signal IREF/VREF produces threshold voltage through first resistance, offer an input of error amplifier behind the detected voltage superposition of described threshold voltage same sampling anode Sense+, the detected voltage of sampling negative terminal Sense-offers another input of error amplifier, error amplifier amplifies the voltage of two input inputs, and output error is amplified voltage;

Oscillator, described oscillator produce input and the slope-compensation module that an oscillator signal offers trigger;

The NMOS power tube, the drain electrode of described NMOS power tube connects switch port SW, and the source end of NMOS power tube connects earth terminal GND through second resistance;

Sampling amplifier, described sampling amplifier be to the amplification of sampling of the second resistance both end voltage, the output sampled voltage;

The slope-compensation module, the sampled voltage that described slope-compensation module is exported sampling amplifier according to the ramp voltage of oscillator output carries out being input to comparator after the slope-compensation;

Comparator, described comparator compares the output and the output of described error amplifier of slope-compensation module, and its output signal offers another input of trigger;

The input that trigger, the output of described trigger offer driver carries out the signal enhancing;

Driver, the comparison signal PWM of another input input voltage comparison module output of described driver, output end of driver connects the grid of NMOS power tube.

The LED drive system comprises

Electronic transformer, described electronic transformer input AC civil power is converted to low-voltage ac voltage and output with described electric main;

Rectification module, described rectification module is converted to DC input voitage VIN with the low-voltage ac voltage of described electronic transformer output, offers LED Drive and Control Circuit, peripheral circuit and filter capacitor, described rectification module and filter capacitor ground connection;

The LED Drive and Control Circuit, described LED Drive and Control Circuit is imported the dividing potential drop of described DC input voitage VIN or DC input voitage VIN, produces the LED drive control signal and offers the peripheral LED circuit, and described LED Drive and Control Circuit is as mentioned above;

Described peripheral circuit comprises inductance, voltage stabilizing didoe, output capacitance, output sampling resistor and LED lamp;

After the LED drive system powered on, DC input voitage VIN charged to output capacitance;

Behind the LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to first reference voltage, the comparison signal PWM of the voltage comparison module of LED Drive and Control Circuit output at this moment is a high level, drive circuit output high level, the conducting of NMOS power tube, output capacitance is by the discharge of LED lamp, DC input voitage VIN is by inductance L 1, the NMOS power tube, second resistance, ground produces path, electric current on the inductance increases, inductive current on the while second resistance detection inductance also is converted to voltage, the second ohmically voltage amplifies by sampling amplifier, the ramp signal of coming with oscillator superposes, output signal with error amplifier compares then, the voltage on the error amplifier detection output sampling resistor and the pressure reduction of the first ohmically voltage, wherein the first ohmically voltage is that the electric current of output current threshold value control module output is in the first ohmically pressure drop, when inductive current continues to increase, comparator output high level, trigger 306 output low levels, by driver, the NMOS power tube turn-offs; Because the inductive current of inductance needs afterflow, the voltage stabilizing didoe conducting of peripheral circuit, LED upper reaches overcurrent, error amplifier detects the first ohmically pressure drop simultaneously, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN is lower than second reference voltage, voltage comparison module output comparison signal PWM is a low level, comparison signal PWM control and driving module, the driver module output voltage is low, the NMOS power tube turn-offs, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, and after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

The invention has the beneficial effects as follows: compare with traditional technology, the LED Drive and Control Circuit that the present invention proposes adds voltage comparison module and output current threshold value control module, the LED electric current changed excessive influence when this led drive circuit can solve the civil power variation, convenient setting output current, and can solve the problem that electric current changes the LED lamp flicker that brings.

Description of drawings

Fig. 1 is traditional LED drive system schematic diagram;

Fig. 2 is the LED control circuit and the peripheral circuit schematic diagram of traditional buck pattern;

The LED drive system schematic diagram that the LED control circuit that Fig. 3 proposes for the present invention constitutes;

A kind of buck pattern LED drive system schematic diagram figure that the led drive circuit that Fig. 4 proposes for the present invention constitutes;

The another kind of buck pattern LED drive system schematic diagram figure that the led drive circuit that Fig. 5 proposes for the present invention constitutes;

Fig. 6 is a kind of specific embodiment of the voltage comparison module of the led drive circuit of the present invention's proposition;

Fig. 7 is the waveform schematic diagram of the voltage comparison module of the led drive circuit of the present invention's proposition;

Fig. 8 is a kind of concrete enforcement circuit of the current threshold control module of the led drive circuit of the present invention's proposition;

The current threshold control signal of the current threshold control module output of the led drive circuit that Fig. 9 proposes for the present invention is with the variation diagram of duty ratio.

Embodiment

Below in conjunction with accompanying drawing content of the present invention is further specified.

Fig. 3, Fig. 4, Fig. 5 are LED Drive and Control Circuit 30 schematic diagrames that the present invention proposes, and comprising:

Voltage comparison module 310, the dividing potential drop of described voltage comparison module 310 input voltage VIN or DC input voitage VIN, to compare with dividing potential drop first reference voltage and second reference voltage of input voltage VIN or DC input voitage VIN, produce a comparison signal PWM and offer output current threshold value control module 302 and LED driver module 60, described first reference voltage is greater than second reference voltage;

Output current threshold value control module 302, described output current threshold value control module 302 produces current threshold control signal IREF/VREF to LED driver module 60 according to the duty ratio of the comparison signal PWM of input;

LED driver module 60, described LED driver module 60 produces the LED drive control signal according to the described current threshold control signal IREF/VREF and the comparison signal PWM of input;

After LED Drive and Control Circuit 30 enters operate as normal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during greater than first reference voltage, the LED drive control signal of comparison signal PWM control LED driver module 60 outputs of voltage comparison module 310 outputs is the LED Continuity signal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during less than second reference voltage, the LED drive control signal of comparison signal PWM control LED driver module 60 outputs of voltage comparison module 310 outputs is the LED cut-off signals, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED Drive and Control Circuit output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

Further, comprise as Fig. 4 and the described LED driver module 60 of Fig. 5:

Error amplifier 301, described current threshold control signal IREF/VREF produces threshold voltage through first resistance R 301, offer an input of error amplifier 301 behind the detected voltage superposition of described threshold voltage same sampling anode Sense+, the detected voltage of sampling negative terminal Sense-offers another input of error amplifier 301, the voltage of 301 pairs of two inputs inputs of error amplifier amplifies, and output error is amplified voltage;

Oscillator 304, described oscillator 304 produce input and the slope-compensation module 309 that an oscillator signal offers trigger 306;

NMOS power tube M1, the drain electrode of described NMOS power tube M1 connects switch port SW, and the source end of NMOS power tube M1 connects earth terminal GND through second resistance;

The amplification of sampling of sampling amplifier 308,308 pairs second resistance R 302 both end voltage of described sampling amplifier, the output sampled voltage;

Slope-compensation module 309, described slope-compensation module 309 carries out being input to comparator 305 after the slope-compensation according to the ramp voltage of the oscillator 304 output sampled voltage to sampling amplifier output 302;

Comparator 305, described comparator 305 compares the output and 301 outputs of described error amplifier of slope-compensation module 309, and its output signal offers another input of trigger 306;

The input that trigger 306, the output of described trigger 306 offer driver 307 carries out the signal enhancing;

Driver 307, the comparison signal PWM of another input input voltage comparison module 310 outputs of described driver 307, the output of driver 307 connects the grid of NMOS power tube M1.

The LED drive system comprises as shown in Figure 3:

Described LED driving control device, described device comprises:

Electronic transformer, described electronic transformer input termination civil power 220V, the output of electronic transformer connects rectification module;

Rectifier module D 1～D4, described rectification module is converted to DC input voitage VIN with the low-voltage ac voltage of described electronic transformer output, offers LED Drive and Control Circuit, peripheral circuit and filter capacitor, described rectification module and filter capacitor ground connection;

The LED Drive and Control Circuit, described LED Drive and Control Circuit is imported the dividing potential drop of described DC input voitage VIN or DC input voitage VIN, produces the LED drive control signal and offers the peripheral LED circuit, and described LED Drive and Control Circuit is as mentioned above;

Described peripheral circuit comprises inductance L 1, voltage stabilizing didoe D5, output capacitance C1, output sampling resistor Rs and LED lamp;

After the LED drive system powered on, DC input voitage VIN charged to output capacitance C1;

Behind the LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to first reference voltage, the comparison signal PWM of voltage comparison module 310 outputs of LED Drive and Control Circuit is a high level at this moment, drive circuit 307 output high level, NMOS power tube M1 conducting, output capacitance C1 is by the discharge of LED lamp, DC input voitage VIN is by inductance L 1, NMOS power tube M1, second resistance R 302, ground produces path, electric current on the inductance L 1 increases, second resistance R 302 detects the inductive current on the inductance L 1 and is converted to voltage simultaneously, voltage on second resistance R 302 amplifies by sampling amplifier 308, the ramp signal of coming with oscillator 304 superposes, output signal with error amplifier 301 compares then, the voltage on the error amplifier 301 detection output sampling resistor Rs and the pressure reduction of the voltage on first resistance R 301, wherein the voltage on first resistance R 301 is the pressure drop of electric current on first resistance R 301 of output current threshold value control module output, when inductive current continues to increase, comparator 305 output high level, trigger 306 output low levels, by driver 307, NMOS power tube M1 turn-offs; Because the inductive current of inductance L 1 needs afterflow, the voltage stabilizing didoe D5 conducting of peripheral circuit, LED upper reaches overcurrent, pressure drop on the first resistance R s of error amplifier 301 detections simultaneously, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN is lower than second reference voltage, voltage comparison module 310 output pwm signals are low level, pwm signal control and driving module 307, driver module 307 output voltages are low, NMOS power tube M1 turn-offs, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, and after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

Fig. 6 is a kind of concrete enforcement circuit of the voltage comparison module of the LED Drive and Control Circuit of the present invention's proposition, wherein, DC input voitage VIN offers the first divider resistance R1, the first divider resistance R1 connects with the second divider resistance R2, and the dividing potential drop of DC input voitage VIN, the dividing potential drop of DC input voitage VIN offers the negative input end of the first comparator I5 and the positive input terminal of the second comparator I6, the other end ground connection of the second divider resistance R2, the positive input terminal of the first comparator I5 is imported the first reference voltage V REF1, the negative input end of the second comparator I6 is imported the second reference voltage V REF2, the output of the first comparator I5 connects the input S end of the first rest-set flip-flop I7, the output of the second comparator I6 connects the another one input R end of rest-set flip-flop I7, the output of rest-set flip-flop I7 connects the input of inverter I8, and the output signal of inverter I8 is comparison signal PWM.

The operation principle of the instantiation of the described voltage comparison module I2 of Fig. 6 is:

When VINA is uprised gradually by low, when being higher than the second reference voltage V REF2, the first comparator I5 output low level, the second comparator I6 export high level, and the R of rest-set flip-flop I7 holds and resets, the Q output low level of rest-set flip-flop I7, comparison signal PWM is a high level; When VINA by height step-down gradually, when being lower than the first reference voltage V REF1, the first comparator I5 exports high level, the second comparator I6 output low level, the S end set of rest-set flip-flop I7, the Q output high level of rest-set flip-flop I7, comparison signal PWM is a low level.

Fig. 7 is the waveform schematic diagram of the voltage comparison module of the LED Drive and Control Circuit of the present invention's proposition, the relation between VIN/VINA and the comparison signal PWM as seen from Figure 7.

The output current threshold value control module of the LED Drive and Control Circuit that Fig. 8 proposes for the present invention a kind of

Embodiment.

Output current threshold value control module 302 comprises:

The first inverter I31, the comparison signal PWM of input voltage comparison module 310 outputs, the first inverter I31 is output as the inversion signal PWM0 of comparison signal PWM;

The first transmission gate I32 imports the 3rd reference voltage V REF3, and inversion signal PWM0 and comparison signal pwm signal are as the switching signal of transmission gate;

The second transmission gate I33, input signal are ground, and inversion signal PWM0 and comparison signal PWM are as the switching signal of the second transmission gate I33;

The output of the output of the first transmission gate I32, the second transmission gate I33 links together and offers filter circuit, described filter circuit with first transmission gate, second transmission the switching signal exported be filtered into direct current, described filter circuit is exported the 4th voltage VREF4, described the 4th voltage VREF4 is the product of the duty ratio of tertiary voltage VREF3 and comparison signal PWM, that is:

VREF4＝VREF3*D

Described the 4th voltage VREF4 offers first voltage-current converter, and described first voltage-current converter converts the voltage signal of described the 4th voltage VREF4 the current signal of the 4th electric current I REF4 to, that is:

$\mathrm{<figure-callout\; id="4"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}4=\frac{\mathrm{VREF}4}{R32}$

Second voltage-current converter converts the voltage signal of tertiary voltage VREF3 of input the current signal of the 3rd electric current I REF3 to, that is:

$\mathrm{<figure-callout\; id="3"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}3=\frac{\mathrm{VREF}3}{\mathrm{<figure-callout\; id="33"\; label="R"\; filenames="HSA00000528659700021.png"\; state="\{\{state\}\}">R</figure-callout>}33}$

Multiplication/division device I36 multiplies each other the 3rd electric current I REF3 and the 5th electric current I REF5, and product produces current threshold control signal IREF divided by the 4th electric current I REF4:

$\mathrm{IREF}=\frac{\mathrm{<figure-callout\; id="3"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}3*\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}5}{\mathrm{<figure-callout\; id="4"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}4},$ Expression formula substitution with IREF3 and IREF4 obtains:

$\mathrm{IREF}=\frac{\mathrm{IREF}5}{D}$

Because $\mathrm{Iref}=\mathrm{IREF}*\frac{\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSA00000528659700022.png,HSA00000528659700031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}}=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*R301}{D*\mathrm{Rs}},$ Like this, can obtain:

$\mathrm{Iavg}=\mathrm{Iref}*D=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSA00000528659700022.png,HSA00000528659700031.png"\; state="\{\{state\}\}">R</figure-callout>}301*D}{D*\mathrm{Rs}}=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSA00000528659700022.png,HSA00000528659700031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}},$ Order $\frac{\mathrm{IREF}}{}$ $\frac{5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSA00000528659700022.png,HSA00000528659700031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}}=K,$ Obtain like this:

Iavg＝K

Wherein:

Iref is the threshold value of the output current of output sampling resistor;

IREF is the output of output current threshold value control module;

Iavg is the product value of current threshold and duty ratio;

Ton is the ON time of comparison signal pwm signal;

T is the cycle of comparison signal pwm signal.

Particularly, filter circuit comprises: the output of the output of the first transmission gate I32, the second transmission gate I33 connects another termination first capacitor C 31 of the 3rd resistance R 31, the three resistance R 31 and the positive input terminal of the first amplifier I34;

Particularly, first voltage-current converter comprises: the negative input end of the first amplifier I34 connects the source end of the 4th resistance R 32 and the 7th metal-oxide-semiconductor M7, the grid end of output termination the 7th metal-oxide-semiconductor M7 of the first amplifier I34, the other end ground connection of the 4th resistance R 32, the drain terminal of the 7th metal-oxide-semiconductor M7 connects the grid of the grid of the second metal-oxide-semiconductor M2 and drain electrode, the 3rd metal-oxide-semiconductor M3, the source electrode of the second metal-oxide-semiconductor M2 and the 3rd metal-oxide-semiconductor M3 meets internal electric source VDD, and the drain signal of the 3rd metal-oxide-semiconductor M3 connects the input of multiplication/division device I36 as the 4th electric current I REF4;

Particularly, second voltage-current converter comprises: the 3rd reference voltage V REF3 connects the positive input terminal of the second amplifier I35, the negative input end of the second amplifier I35 connects the source end of the 5th resistance R 33 and the 4th metal-oxide-semiconductor M4, the grid end of output termination the 4th metal-oxide-semiconductor M4 of the second amplifier I35, the other end ground connection of the 5th resistance R 33, the drain terminal of the 4th metal-oxide-semiconductor M4 connects grid and the drain electrode of the 5th metal-oxide-semiconductor M5, the grid of the 5th metal-oxide-semiconductor M6, the source electrode of the 5th metal-oxide-semiconductor M5 and the 6th metal-oxide-semiconductor M6 meets internal electric source VDD, and the drain signal of the 6th metal-oxide-semiconductor M6 connects another input of multiplication/division device I36 as the 3rd electric current I REF3.

The operation principle of a kind of embodiment of the described output current threshold value control of Fig. 8 module is: as comparison signal PWM when being high, and the first transmission gate I32 conducting, the second transmission gate I33 is obstructed, and the common output voltage of transmission gate is tertiary voltage VREF3; When comparison signal PWM when low, the first transmission gate I32 is obstructed, the second transmission gate I33 conducting, the common output voltage of transmission gate is ground, filter circuit, be used for the switching signal of transmission gate output is filtered into direct current, promptly the 4th voltage VREF4 is the product of the duty ratio of tertiary voltage VREF3 and comparison signal PWM:

VREF4＝VREF3*D

First voltage-current converter is used for the voltage signal of the 4th voltage VREF4 is converted to the current signal of the 4th electric current I REF4, and it is identical with the breadth length ratio of the 3rd metal-oxide-semiconductor M3 to set the second metal-oxide-semiconductor M2, can get:

$\mathrm{<figure-callout\; id="4"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}4=\frac{\mathrm{VREF}4}{R32}$

Second voltage-current converter is used for the voltage signal of tertiary voltage VREF3 is converted to the current signal of the 3rd electric current I REF3, and it is identical with the breadth length ratio of the 6th metal-oxide-semiconductor M6 to set the 5th metal-oxide-semiconductor M5, can get:

$\mathrm{<figure-callout\; id="3"\; label="IREF"\; filenames="HSA00000528659700051.png"\; state="\{\{state\}\}">IREF</figure-callout>}3=\frac{\mathrm{VREF}3}{\mathrm{<figure-callout\; id="33"\; label="R"\; filenames="HSA00000528659700021.png"\; state="\{\{state\}\}">R</figure-callout>}33}$

The duty ratio that is comparison signal PWM is big more, and current threshold is more little, and both products are constants, so just can so that the output average current of system under different civil power 180～265V equate.

Fig. 9 be IREF/IREF0 with the change in duty cycle curve, wherein IREF is the output of output current threshold value control module, IREF0 is that duty ratio is the output control signal of the output current threshold value control module under 100%.Can see that by figure the product of IREF/IREF0 and duty ratio D is 1.

The invention discloses led drive circuit and driving method thereof, and describe the specific embodiment of the present invention and effect with reference to the accompanying drawings.What should be understood that is; the foregoing description is just to explanation of the present invention; rather than limitation of the present invention; any innovation and creation that do not exceed in the connotation scope of the present invention; include but not limited to voltage comparison module; the modification of the composition mode of output current threshold value control module; to the change of the local structure of circuit (as utilize those skilled in the art thinkable technical method replace voltage comparison module among the present invention; increase and reduce logic control); replacement to the type or the model of components and parts; and the replacement of other unsubstantialities or modification etc., all fall within the protection range of the present invention.

Claims (7)

1. LED Drive and Control Circuit is characterized in that comprising:

Voltage comparison module, the dividing potential drop of described voltage comparison module input voltage VIN or DC input voitage VIN, to compare with dividing potential drop first reference voltage and second reference voltage of input voltage VIN or DC input voitage VIN, produce a comparison signal PWM and offer output current threshold value control module and LED driver module, described first reference voltage is greater than second reference voltage;

Output current threshold value control module, described output current threshold value control module produces current threshold control signal IREF/VREF to the LED driver module according to the duty ratio of the comparison signal PWM of input;

The LED driver module, described LED driver module produces the LED drive control signal according to the described current threshold control signal IREF/VREF and the comparison signal PWM of input;

After the LED Drive and Control Circuit enters operate as normal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during greater than first reference voltage, the LED drive control signal of the comparison signal PWM control LED driver module output of voltage comparison module output is the LED Continuity signal, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN during less than second reference voltage, the LED drive control signal of the comparison signal PWM control LED driver module output of voltage comparison module output is the LED cut-off signals, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED Drive and Control Circuit output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

2. a kind of according to claim 1 LED Drive and Control Circuit is characterized in that described LED driver module comprises:

Error amplifier, described current threshold control signal IREF/VREF produces threshold voltage through first resistance, offer an input of error amplifier behind the detected voltage superposition of described threshold voltage same sampling anode Sense+, the detected voltage of sampling negative terminal Sense-offers another input of error amplifier, error amplifier amplifies the voltage of two input inputs, and output error is amplified voltage;

Oscillator, described oscillator produce input and the slope-compensation module that an oscillator signal offers trigger;

The NMOS power tube, the drain electrode of described NMOS power tube connects switch port SW, and the source end of NMOS power tube connects earth terminal GND through second resistance;

Sampling amplifier, described sampling amplifier be to the amplification of sampling of the second resistance both end voltage, the output sampled voltage;

The slope-compensation module, the sampled voltage that described slope-compensation module is exported sampling amplifier according to the ramp voltage of oscillator output carries out being input to comparator after the slope-compensation;

Comparator, described comparator compares the output and the output of described error amplifier of slope-compensation module, and its output signal offers another input of trigger;

The input that trigger, the output of described trigger offer driver carries out the signal enhancing;

Driver, the comparison signal PWM of another input input voltage comparison module output of described driver, output end of driver connects the grid of NMOS power tube.

3. a kind of as claimed in claim 1 or 2 LED Drive and Control Circuit is characterized in that described voltage comparison module comprises:

DC input voitage offers first divider resistance, first divider resistance is connected with second divider resistance, and the dividing potential drop of DC input voitage VIN, the dividing potential drop of DC input voitage VIN offers the negative input end of first comparator and the positive input terminal of second comparator, the other end ground connection of second divider resistance, the positive input terminal of first comparator is imported the first reference voltage V REF1, the negative input end of second comparator is imported second reference voltage, the output of first comparator connects an input of first rest-set flip-flop, the output of second comparator connects the another one input of rest-set flip-flop, the output of rest-set flip-flop connects the input of inverter, and the output signal of inverter is comparison signal PWM.

4. a kind of as claimed in claim 1 or 2 LED Drive and Control Circuit is characterized in that described output current threshold value control module comprises:

First inverter, the comparison signal PWM of input voltage comparison module output, first inverter is output as the inversion signal of comparison signal PWM;

First transmission gate is imported the 3rd reference voltage V REF3, and inversion signal and comparison signal pwm signal are as the switching signal of first transmission gate;

Second transmission gate, input signal are ground, and inversion signal and comparison signal PWM are as the switching signal of second transmission gate;

The output of the output of first transmission gate, second transmission gate links together and offers filter circuit, described filter circuit with first transmission gate, second transmission the switching signal exported be filtered into direct current, described filter circuit is exported the 4th voltage VREF4, described the 4th voltage VREF4 is the product of the duty ratio of tertiary voltage VREF3 and comparison signal PWM, that is:

VREF4＝VREF3*D

Described the 4th voltage VREF4 offers first voltage-current converter, and described first voltage-current converter converts the voltage signal of described the 4th voltage VREF4 the current signal of the 4th electric current I REF4 to, that is:

$\mathrm{IREF}4=\frac{\mathrm{VREF}4}{R32}$

Second voltage-current converter converts the voltage signal of tertiary voltage VREF3 of input the current signal of the 3rd electric current I REF3 to, that is:

$\mathrm{IREF}3=\frac{\mathrm{VREF}3}{R33}$

Multiplication/division device I36 multiplies each other the 3rd electric current I REF3 and the 5th electric current I REF5, and product produces current threshold control signal IREF divided by the 4th electric current I REF4:

$\mathrm{IREF}=\frac{\mathrm{IREF}3*\mathrm{IREF}5}{\mathrm{IREF}4},$ Expression formula substitution with IREF3 and IREF4 obtains:

$\mathrm{IREF}=\frac{\mathrm{IREF}5}{D}$

Because $\mathrm{Iref}=\mathrm{IREF}*\frac{R301}{\mathrm{Rs}}=\frac{\mathrm{IREF}5*R301}{D*\mathrm{Rs}},$ Like this, can obtain:

$\mathrm{Iavg}=\mathrm{Iref}*D=\frac{\mathrm{IREF}5*R301*D}{D*\mathrm{Rs}}=\frac{\mathrm{IREF}5*R301}{\mathrm{Rs}},$ Order $\frac{\mathrm{IREF}5*R301}{\mathrm{Rs}}=K,$ Obtain like this:

Iavg＝K

Wherein:

Iref is the threshold value of the output current of output sampling resistor;

IREF is the output of output current threshold value control module;

Iavg is the product value of current threshold and duty ratio;

Ton is the ON time of comparison signal pwm signal;

T is the cycle of comparison signal pwm signal.

5.LED drive system comprises:

Electronic transformer, described electronic transformer input AC civil power is converted to low-voltage ac voltage and output with described electric main;

Rectification module, described rectification module is converted to DC input voitage VIN with the low-voltage ac voltage of described electronic transformer output, offers LED Drive and Control Circuit, peripheral circuit and filter capacitor, described rectification module and filter capacitor ground connection;

The LED Drive and Control Circuit, described LED Drive and Control Circuit is imported the dividing potential drop of described DC input voitage VIN or DC input voitage VIN, produces the LED drive control signal and offers the peripheral LED circuit;

Described peripheral circuit comprises inductance, voltage stabilizing didoe, output capacitance, output sampling resistor and LED lamp;

It is characterized in that described LED Drive and Control Circuit as claimed in claim 1 or 2.

6. as LED drive system as described in the claim 5, it is characterized in that:

After the LED drive system powered on, DC input voitage VIN charged to output capacitance;

Behind the LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to first reference voltage, the comparison signal PWM of the voltage comparison module of LED Drive and Control Circuit output at this moment is a high level, drive circuit output high level, the conducting of NMOS power tube, output capacitance is by the discharge of LED lamp, DC input voitage VIN is by inductance L 1, the NMOS power tube, second resistance, ground produces path, electric current on the inductance increases, inductive current on the while second resistance detection inductance also is converted to voltage, the second ohmically voltage amplifies by sampling amplifier, the ramp signal of coming with oscillator superposes, output signal with error amplifier compares then, the voltage on the error amplifier detection output sampling resistor and the pressure reduction of the first ohmically voltage, wherein the first ohmically voltage is that the electric current of output current threshold value control module output is in the first ohmically pressure drop, when inductive current continues to increase, comparator output high level, trigger 306 output low levels, by driver, the NMOS power tube turn-offs; Because the inductive current of inductance needs afterflow, the voltage stabilizing didoe conducting of peripheral circuit, LED upper reaches overcurrent, error amplifier detects the first ohmically pressure drop simultaneously, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN is lower than second reference voltage, voltage comparison module output comparison signal PWM is a low level, comparison signal PWM control and driving module, the driver module output voltage is low, the NMOS power tube turn-offs, the product of the duty ratio of described current threshold control signal IREF/VREF and comparison signal PWM is a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, and after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to first reference voltage from second reference voltage, goes round and begins again.

7. as LED drive system as described in claim 5 or 6, the duty ratio that it is characterized in that described described current threshold control signal IREF/VREF and comparison signal PWM is that the mathematical notation formula of a constant is:

$\mathrm{Iavg}=\frac{\mathrm{Ton}}{T}*\mathrm{Iref}$ Promptly

Iavg=D*Iref, wherein

Control Iref makes:

$\mathrm{Iref}=\frac{K}{D},$ Like this, obtain:

Iavg=K, just Iavg is a constant with independent of duty cycle;

Wherein:

Iavg is the product value of current threshold and duty ratio,

Ton is the ON time of comparison signal pwm signal,

T is the cycle of comparison signal pwm signal,

D is the duty ratio of comparison signal pwm signal,

Iref is the threshold value of the output current of output sampling resistor,

K is a constant.

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