CN102202449B - 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 or VREF (Input Reference or 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 or VREF and the comparison signal PWM. The product of the duty factor of the current threshold control signal IREF or 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 LED drive circuit field, relating in particular to and adopting electronic transformer is the LED drive circuit technology of LED lamp power supply as power supply.

Background technology

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

Due to traditional Halogen lamp LED electronics transformer-supplied, the output of electronic transformer is a kind of well selection for the Halogen lamp LED of resistance characteristic, if but by LED lamp replacement Halogen lamp LED, 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 C1, LED Drive and Control Circuit 10, peripheral circuit 20 and LED lamp.

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

Peripheral circuit 10 shown in Fig. 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 after rectifying and wave-filtering connects one end of capacitor C 1, one end, the negative pole of LED lamp string and the VIN of LED Drive and Control Circuit 20 end, an other positive pole of termination voltage stabilizing didoe D1 of inductance L 1 and the SW of LED Drive and Control Circuit 20 end of inductance L 1.The negative pole of voltage stabilizing didoe D5, the other end of output capacitance C1, one end of output sampling resistor Rs, the SENSE+ of LED Drive and Control Circuit 20 connect, and the positive pole of an other termination LED lamp string of output sampling resistor Rs, the SENSE-end of LED Drive and Control Circuit 20 are connected.

Described LED Drive and Control Circuit (20) comprising: SENSE-end is connected with the negative terminal of error amplifier 201, SENSE+ end is connected with one end of resistance R 201, other one end of R201 and the anode of error amplifier 201 and fixed threshold arrange module 202, the output of error amplifier 201 is connected with the negative terminal of comparator 205, the anode of comparator 205 is connected with the output of slope compensation module 209, the input of slope compensation module 209 is respectively 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 is connected with the R end of rest-set flip-flop 206, the output of rest-set flip-flop 206 is connected with the input of driver module 207, the output of driver module 207 is connected with the grid of metal-oxide-semiconductor M1, the source electrode of metal-oxide-semiconductor M1 is connected with one end of resistance R 202, and be connected with the anode of sampling amplifier 208, other one end of resistance R 202 is connected to the ground, and be connected 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) VIN port connect one end of internal reference 203.

Civil power AC180～265V power supply provides power supply for electronic transformer, and electronic transformer is converted into civil power the voltage that exchanges AC12V, and the voltage that exchanges AC12V carries out rectification by rectifier module D 1～D4, and the later voltage of rectification is by filter capacitor C1 filtering.Ideally, filter capacitor C1 is larger, and the ripple voltage of DC input voitage VIN is less, and still, due to the volume restrictions of Lamp cup, filter capacitor C1 can not get too large, generally selects the electric capacity of 330uF or 220uF.Even if the ripple voltage of DC input voitage VIN is still very large like this, ripple voltage is minimum can be low below 4V, the highest 17V left and right that can be up to.And under same line voltage, more than the low-voltage of ripple voltage and high-tension pressure reduction can reach 6V.

DC input voitage VIN voltage is to the power supply of LED Drive and Control Circuit, and LED Drive and Control Circuit connects the LED that will be connected in series, and in general Lamp cup, can select 3 × 1W, or the LED lamp of 4 × 1W.LED Drive and Control Circuit 11 can be used traditional decompression mode or buck pattern in the time driving 3 × 1W, substantially adopts buck pattern when 4 × 1W, under partial condition, can adopt boost mode.But no matter adopt which kind of pattern, at civil power AC, in the time that 180～265V changes, the output current of LED all can vary widely, and the phenomenon that also there will be LED lamp to glimmer under power network fluctuation.Principle is: under different line voltages, if civil power AC is in the time that 180～265V changes, the output voltage waveforms of electronic transformer changes, civil power AC voltage is higher, and output voltage is also just higher, and LED Drive and Control Circuit has minimum operating voltage, when the output voltage of electronic transformer is during lower than the minimum operating voltage of LED Drive and Control Circuit, electric current on LED lamp is zero, and in the time that output voltage drives the minimum operating voltage of control chip higher than LED, the electric current on LED lamp is set point.While variation from 180～265V due to civil power AC voltage, electronic transformer output voltage can be different higher than the time of the minimum operating voltage of LED Drive and Control Circuit, therefore in the cycle of every 10ms, the asynchronism(-nization) of the normal work of LED Drive and Control Circuit, can cause curent change very large.In the time of 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%; In the time that 180～265V changes, 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 to certain influence in the life-span of LED etc., and is prone to flicker in the time of power network fluctuation.

Summary of the invention

The present invention is intended to solve the deficiencies in the prior art, provide a kind of in the time that civil power changes from 180V～265V output current change LED Drive and Control Circuit little, that there will not be scintillation, this circuit applicable to adopt electronic transformer as power supply the LED driving control device to the power supply of LED lamp.

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

LED Drive and Control Circuit, comprising:

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

Output current threshold value control module, described output current threshold value control module is according to the duty ratio generation current threshold value control signal of the comparison signal PWM of input, i.e. and IREF or VREF, gives LED driver module;

LED driver module, described LED driver module is according to the described current threshold control signal of input, i.e. IREF or VREF, and comparison signal PWM produces LED drive control signal;

LED Drive and Control Circuit enters after normal work, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is greater than the first reference voltage, the LED drive control signal that the comparison signal PWM of voltage comparison module output controls the output of LED driver module is LED Continuity signal, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is less than the second reference voltage, the LED drive control signal that the comparison signal PWM of voltage comparison module output controls the output of LED driver module is LED cut-off signals, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be 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 the first reference voltage from the second reference voltage, go round and begin again.

Further, described LED driver module comprises:

Error amplifier, described current threshold control signal, be IREF or VREF, produce threshold voltage through the first resistance, after the voltage stack that described threshold voltage detects with sampling anode Sense+, offer an input of error amplifier, the voltage that sampling negative terminal Sense-detects offers another input of error amplifier, and error amplifier amplifies the voltage of two input inputs, and output error is amplified voltage;

Oscillator, described oscillator produces an oscillator signal and offers input and the slope compensation module of trigger;

NMOS power tube, the drain electrode connecting valve port SW of described NMOS power tube, the source of NMOS power tube connects earth terminal GND through the second resistance;

Sampling amplifier, described sampling amplifier carries out amplifier to the second resistance both end voltage, output sampled voltage;

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

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

Trigger, the input that the output of described trigger offers driver carries out signal enhancing;

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

LED drive system, comprises

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

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

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

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

After LED drive system powers on, DC input voitage VIN charges to output capacitance;

After LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to the first reference voltage, the comparison signal PWM of the now voltage comparison module of LED Drive and Control Circuit output is high level, drive circuit output high level, the conducting of NMOS power tube, output capacitance is discharged by LED lamp, DC input voitage VIN is by inductance L 1, NMOS power tube, the second resistance, ground produces path, electric current on inductance increases, inductive current on while the second resistance detection inductance is also converted to voltage, the second ohmically voltage amplifies by sampling amplifier, the ramp signal of coming with oscillator superposes, then compare with the output signal of error amplifier, voltage on 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, pass through driver, NMOS power tube turn-offs, because the inductive current of inductance needs afterflow, the voltage stabilizing didoe conducting of peripheral circuit, the upper current flowing of LED, 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 during lower than the second reference voltage, voltage comparison module output comparison signal PWM is low level, comparison signal PWM controls driver module, driver module output voltage is low, NMOS power tube turn-offs, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to the first reference voltage from the second reference voltage, go round and begin again.

The invention has the beneficial effects as follows: compare with conventional art, the LED Drive and Control Circuit that the present invention proposes adds voltage comparison module and output current threshold value control module, the excessive impact of LED curent change when this LED drive circuit can solve civil power variation, convenient set output current, and can solve the problem of the LED lamp flicker that curent change brings.

Brief description of the drawings

Fig. 1 is traditional LED drive system schematic diagram;

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

Fig. 3 is the LED drive system schematic diagram that the LED control circuit that proposes of the present invention forms;

Fig. 4 is a kind of buck pattern LED drive system schematic diagram figure that the LED drive circuit that proposes of the present invention forms;

Fig. 5 is the another kind of buck pattern LED drive system schematic diagram figure that the LED drive circuit that proposes of the present invention forms;

Fig. 6 is a kind of specific embodiment of the voltage comparison module of the LED drive circuit that proposes of the present invention;

Fig. 7 is the waveform schematic diagram of the voltage comparison module of the LED drive circuit that proposes of the present invention;

Fig. 8 is the concrete implementing circuit of one of the current threshold control module of the LED drive circuit that proposes of the present invention;

Fig. 9 is that the current threshold control signal of current threshold control module output of the LED drive circuit that proposes of 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 illustrated.

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 direct-current input voltage VIN or DC input voitage VIN, to compare with dividing potential drop the first reference voltage and the second reference voltage of DC input voitage 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 the first reference voltage is greater than the second reference voltage;

Output current threshold value control module 302, described output current threshold value control module 302 is according to the duty ratio generation current threshold value control signal of the comparison signal PWM of input, i.e. and IREF or VREF, gives LED driver module 60;

LED driver module 60, described LED driver module 60 is according to the described current threshold control signal of input, i.e. IREF or VREF, and comparison signal PWM produces LED drive control signal;

LED Drive and Control Circuit 30 enters after normal work, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is greater than the first reference voltage, the LED drive control signal that the comparison signal PWM control LED driver module 60 that voltage comparison module 310 is exported is exported is LED Continuity signal, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is less than the second reference voltage, the LED drive control signal that the comparison signal PWM control LED driver module 60 that voltage comparison module 310 is exported is exported is LED cut-off signals, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be 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 the first reference voltage from the second reference voltage, go round and begin again.

Further, the LED driver module 60 as described in Fig. 4 and Fig. 5 comprises:

Error amplifier 301, described current threshold control signal, be IREF or VREF, produce threshold voltage through the first resistance R 301, after the voltage stack that described threshold voltage detects with sampling anode Sense+, offer an input of error amplifier 301, the voltage that sampling negative terminal Sense-detects offers another input of error amplifier 301, and error amplifier 301 amplifies the voltage of two input inputs, and output error is amplified voltage;

Oscillator 304, described oscillator 304 produces an oscillator signal and offers input and the slope compensation module 309 of trigger 306;

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

Sampling amplifier 308, described sampling amplifier 308 carries out amplifier to the second resistance R 302 both end voltage, output sampled voltage;

Slope compensation module 309, the ramp voltage that described slope compensation module 309 is exported according to oscillator 304 carries out being input to comparator 305 after slope-compensation to the sampled voltage of sampling amplifier output R302;

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

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

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

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

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

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

After LED drive system powers on, DC input voitage VIN charges to output capacitance C1;

After LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to the first reference voltage, the comparison signal PWM that now voltage comparison module 310 of LED Drive and Control Circuit is exported is high level, drive circuit 307 is exported high level, NMOS power tube M1 conducting, output capacitance C1 discharges by LED lamp, DC input voitage VIN is by inductance L 1, NMOS power tube M1, the second resistance R 302, ground produces path, electric current in inductance L 1 increases, the second resistance R 302 detects the inductive current in inductance L 1 and is converted to voltage simultaneously, voltage in the second resistance R 302 amplifies by sampling amplifier 308, the ramp signal of coming with oscillator 304 superposes, then compare with the output signal of error amplifier 301, error amplifier 301 detects the pressure reduction of the voltage on output sampling resistor Rs and the voltage in the first resistance R 301, wherein the voltage in the first resistance R 301 is the pressure drop in the first resistance R 301 of the electric current of output current threshold value control module output, when inductive current continues to increase, comparator 305 is exported 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, the upper current flowing of LED, error amplifier 301 detects the pressure drop on the first resistance R s simultaneously, when the dividing potential drop of DC input voitage VIN or DC input voitage VIN is during lower than the second reference voltage, voltage comparison module 310 output pwm signals are low level, pwm signal control driver module 307, driver module 307 output voltages are low, NMOS power tube M1 turn-offs, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to the first reference voltage from the second reference voltage, go round and begin again.

Fig. 6 is the concrete implementing circuit of one of the voltage comparison module of the LED Drive and Control Circuit that proposes of the present invention, 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 inputted the first reference voltage V REF1, the negative input end of the second comparator I6 is inputted the second reference voltage V REF2, the output of the first comparator I5 connects an 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, the output signal of inverter I8 is comparison signal PWM.

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

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

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

Fig. 8 is the one of the output current threshold value control module of the LED Drive and Control Circuit that proposes of the present invention

Embodiment.

Output current threshold value control module 302 comprises:

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

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

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

The output of the first transmission gate I32, the output of the second transmission gate I33 link together and offer filter circuit, the switching signal of the first transmission gate, the second transmission gate output is filtered into direct current by described filter circuit, described filter circuit output the 4th voltage VREF4, described the 4th voltage VREF4 is the product of the duty ratio of the 3rd reference voltage V REF3 and comparison signal PWM, that is:

VREF4＝VREF3*D

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

$\mathrm{<figure-callout\; id="4"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}4=\frac{\mathrm{VREF}4}{R32}$

The second reference voltage-current converter, converts the voltage signal of the 3rd reference voltage V REF3 of input to the current signal of the 3rd electric current I REF3, that is:

$\mathrm{<figure-callout\; id="3"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}3=\frac{\mathrm{VREF}3}{R33}$

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

by the expression formula substitution of IREF3 and IREF4, obtain:

$\mathrm{IREF}=\frac{\mathrm{IREF}5}{D}*\frac{R32}{R33}$

Due to $\mathrm{Iref}=\mathrm{IREF}*\frac{\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSB0000122478430000031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}}=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*R301}{D*\mathrm{Rs}}*\frac{R32}{R33},$ Like this, can obtain:

$\mathrm{Iavg}=\mathrm{Iref}*D=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSB0000122478430000031.png"\; state="\{\{state\}\}">R</figure-callout>}301*D}{D*\mathrm{Rs}}*\frac{R32}{R33}=\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSB0000122478430000031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}}*\frac{R32}{R33},$ Order

$\frac{\mathrm{<figure-callout\; id="5"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}5*\mathrm{<figure-callout\; id="301"\; label="R"\; filenames="HSB0000122478430000031.png"\; state="\{\{state\}\}">R</figure-callout>}301}{\mathrm{Rs}}*\frac{R32}{R33}=K,$ 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;

Particularly, filter circuit comprises: the output of the first transmission gate I32, the output of the second transmission gate I33 connect 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, the first reference voltage-current converter comprises: negative input termination the 4th resistance R 32 of the first amplifier I34 and the source of 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, the second reference voltage-current converter comprises: the 3rd reference voltage V REF3 connects the positive input terminal of the second amplifier I35, negative input termination the 5th resistance R 33 of the second amplifier I35 and the source of 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, 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.

Described in Fig. 8, the operation principle of a kind of embodiment of output current threshold value control module is: when comparison signal PWM is while 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 the 3rd reference voltage V REF3; When comparison signal PWM is while being 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, for the switching signal of transmission gate output is filtered into direct current, the 4th voltage VREF4 is the product of the duty ratio of the 3rd reference voltage V REF3 and comparison signal PWM:

VREF4=VREF3*D

The first reference voltage-current converter, for the voltage signal of the 4th voltage VREF4 being converted to the current signal of the 4th electric current I REF4, sets the second metal-oxide-semiconductor M2 identical with the breadth length ratio of the 3rd metal-oxide-semiconductor M3, can obtain:

$\mathrm{<figure-callout\; id="4"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}4=\frac{\mathrm{VREF}4}{R32}$

The second reference voltage-current converter, for the voltage signal of the 3rd reference voltage V REF3 being converted to the current signal of the 3rd electric current I REF3, sets the 5th metal-oxide-semiconductor M5 identical with the breadth length ratio of the 6th metal-oxide-semiconductor M6, can obtain:

$\mathrm{<figure-callout\; id="3"\; label="IREF"\; filenames="HSB0000122478430000042.png"\; state="\{\{state\}\}">IREF</figure-callout>}3=\frac{\mathrm{VREF}3}{R33}$

The duty ratio that is comparison signal PWM is larger, and current threshold is less, and both products are constants, so just can make the output average current of system under different civil power I80～265V equate.

Fig. 9 be IREF/IREF0 with 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 be seen 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, above-described embodiment is just to explanation of the present invention, instead of limitation of the present invention, any innovation and creation that do not exceed within the scope of connotation of the present invention, include but not limited to voltage comparison module, the amendment of the building form of output current threshold value control module, the change of the local structure to circuit (as utilize those skilled in the art thinkable technical method replace the voltage comparison module in the present invention, increase and reduce logic control), type to components and parts or the replacement of model, and replacement or the amendment etc. of other unsubstantialities, within all falling into protection range of the present invention.

Claims (6)

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

Output current threshold value control module, described output current threshold value control module is according to the duty ratio generation current threshold value control signal of the comparison signal PWM of input, i.e. and IREF or VREF, gives LED driver module;

LED driver module, described LED driver module is according to the described current threshold control signal of input, i.e. IREF or VREF, and comparison signal PWM produces LED drive control signal;

LED Drive and Control Circuit enters after normal work, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is greater than the first reference voltage, the LED drive control signal that the comparison signal PWM of voltage comparison module output controls the output of LED driver module is LED Continuity signal, in the time that the dividing potential drop of DC input voitage VIN or DC input voitage VIN is less than the second reference voltage, the LED drive control signal that the comparison signal PWM of voltage comparison module output controls the output of LED driver module is LED cut-off signals, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be 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 the first reference voltage from the second reference voltage, go round and begin again.

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

Error amplifier, described current threshold control signal, be IREF or VREF, produce threshold voltage through the first resistance, after the voltage stack that described threshold voltage detects with sampling anode Sense+, offer an input of error amplifier, the voltage that sampling negative terminal Sense-detects offers another input of error amplifier, and error amplifier amplifies the voltage of two input inputs, and output error is amplified voltage;

Oscillator, described oscillator produces an oscillator signal and offers input and the slope compensation module of trigger;

NMOS power tube, the drain electrode connecting valve port SW of described NMOS power tube, the source of NMOS power tube connects earth terminal GND through the second resistance;

Sampling amplifier, described sampling amplifier carries out amplifier to the second resistance both end voltage, output sampled voltage;

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

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

Trigger, the input that the output of described trigger offers driver carries out signal enhancing;

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

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

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

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

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

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

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

The output of the first transmission gate, the output of the second transmission gate link together and offer filter circuit, described filter circuit by the first transmission gate, the second transmission the switching signal exported be filtered into direct current, described filter circuit output the 4th voltage VREF4, described the 4th voltage VREF4 is the product of the duty ratio of the 3rd reference voltage V REF3 and comparison signal PWM, that is:

VREF4＝VREF3*D

Wherein, D is the duty ratio of comparison signal PWM.

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

Wherein R32 is the resistance of the 4th resistance,

The second reference voltage-current converter, converts the voltage signal of the 3rd reference voltage V REF3 of input to the current signal of the 3rd electric current I REF3, that is:

Wherein, R33 is the resistance of the 5th resistance

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

by the expression formula substitution of IREF3 and IREF4, obtain:

Due to

R301 is the resistance of the first resistance,

Rs is the resistance of output sampling resistor,

Like this, can obtain:

order

obtain like this:

lavg＝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.

5. a LED drive system, comprising:

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

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

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

Described peripheral LED 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. LED drive system as claimed in claim 5, is characterized in that:

After LED drive system powers on, DC input voitage VIN charges to output capacitance;

After LED drive system steady operation, the dividing potential drop of DC input voitage VIN or DC input voitage VIN is elevated to the first reference voltage, the comparison signal PWM of the now voltage comparison module of LED Drive and Control Circuit output is high level, drive circuit output high level, the conducting of NMOS power tube, output capacitance is discharged by LED lamp, DC input voitage VIN is by inductance L 1, NMOS power tube, the second resistance, ground produces path, electric current on inductance increases, inductive current on while the second resistance detection inductance is also converted to voltage, the second ohmically voltage amplifies by sampling amplifier, the ramp signal of coming with oscillator superposes, then compare with the output signal of error amplifier, voltage on 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 level, pass through driver, NMOS power tube turn-offs, because the inductive current of inductance needs afterflow, the voltage stabilizing didoe conducting of peripheral LED circuit, the upper current flowing of LED, 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 during lower than the second reference voltage, voltage comparison module output comparison signal PWM is low level, comparison signal PWM controls driver module, driver module output voltage is low, NMOS power tube turn-offs, described current threshold control signal, be IREF or VREF, with the product of the duty ratio of comparison signal PWM be a constant, and then make under the comparison signal PWM of different duty, the average current of LED driver module output is identical, after this dividing potential drop of DC input voitage VIN or DC input voitage VIN rises to the first reference voltage from the second reference voltage, go round and begin again.

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