CN202145692U

CN202145692U - LED flicker filter circuit

Info

Publication number: CN202145692U
Application number: CN201120276763U
Authority: CN
Inventors: 吴其志; 汪彪; 林万炯
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-07-28
Filing date: 2011-07-28
Publication date: 2012-02-15
Anticipated expiration: 2021-07-28

Abstract

The utility model relates to an LED flicker filter circuit, comprising an AC/DC module, a DC/DC module, a light adjusting signal generation circuit, a first capacitor, and a second capacitor, wherein the input end of the AC/DC module is connected with an externally connected utility power supply, both ends of the first capacitor are respectively connected with two output ends of a main power supplying end of the AC/DC module, both ends of the second capacitor are respectively connected with two output ends of an auxiliary power supplying end of the AC/DC module, two input ends of the light adjusting signal generation circuit are respectively connected with both ends of the second capacitor, the output end of the light adjusting signal generation circuit is connected with the light adjusting interface end of the DC/DC module, and the output end of the DC/DC module is connected with an LED load. The LED flicker filter circuit is characterized by also comprising an enable circuit used for controlling the working state of the DC/DC module and forcedly turning-off the power supply of the DC/DC module when the input power supply of the AC/DC module is turned off, wherein the input end of the enable circuit is connected with both ends of the first capacitor, and the output end of the enable circuit is connected with the output end of the DC/DC module. Compared with the prior art, the LED flicker filter circuit can thoroughly eliminate the phenomenon that when the power supply of the LED is turned off the flicker appears.

Description

A kind of LED anti-flicker circuit

Technical field

The utility model relates to a kind of LED anti-flicker circuit, particularly relate to a kind of adopt the first order be AC/DC module, the second level adopt the DC/DC module two-stage light modulation power supply as the LED driving power when the input power supply is closed, prevent the circuit of LED flicker.

Background technology

Existing LED light regulating technology mainly divides two types from the signal generation principle of light modulation: the one, and the simulation light modulation, the 2nd, the PWM light modulation, the two all needs extra circuit module go to realize, the support of the power supply circuits that this just need be extra.The employing first order commonly used is that adopt in the two-stage light modulation power supply of DC/DC module AC/DC module, the second level; The front first order is the AC/DC module; Be used to produce constant pressure source; This voltage source is as the supply power voltage of DC/DC module, and partial DC/DC module is used for driving LED, makes it to be operated in constant current state.The power supply of dim signal generation circuit can directly hang on the constant pressure source of AC/DC module generation; Mode through step-down is got; The power supply of the power supply of DC/DC module and dim signal generation circuit is synchronous like this; Just do not have the scintillation of switching on and shutting down, but like this because the dividing potential drop of resistance is arranged, unloaded power consumption can be bigger.Another kind of scheme is to increase auxiliary power supply system in first order AC/DC module, and dim signal generation circuit is through the auxiliary power supply system power supply, like this no-load power consumption can reach lower state (＜0.5W); But because the Capacity Ratio of the filter capacitor C1 of first order AC/DC module output is bigger, more than the big several times of capacity than the filter capacitor C2 of the electric power system of dim signal generation circuit, in case power remove (being that civil power is no longer supplied power to the AC/DC module) like this; The velocity of discharge of C1 is compared just slow with C2, when in little load and light modulation to the darkest the time, the LED lamp is because current ratio is less; Brightness is just relatively darker, and the voltage of output is also lower, and this time, C2 discharged into 0; The signal of light modulation has not just had, and the DC/DC module just returns to common mode of operation, and upward voltage is still very high for C1 at this moment; And being higher than the minimum supply power voltage of DC/DC chip, LED is breakdown again so, is operated in normal condition; And brightness necessarily than light modulation to the darkest bright, though the time is very of short duration, when phenomenon is exactly shutoff, can glimmer; Under perhaps several, that gives the people feels very uncomfortable.

The utility model content

The utility model technical problem to be solved be to above-mentioned prior art provide a kind of adopt the first order be AC/DC module, the second level adopt the DC/DC module two-stage light modulation power supply as the LED driving power when the input power supply is closed, prevent the LED anti-flicker circuit of LED flicker.

The utility model solves the problems of the technologies described above the technical scheme that is adopted: this LED anti-flicker circuit; Comprise the AC/DC module; The DC/DC module, dim signal produces circuit, first electric capacity; Second electric capacity; Wherein the input of AC/DC module links to each other with external civil power, and the two ends of first electric capacity link to each other with two outputs of the main feeder ear of AC/DC module respectively, and the two ends of second electric capacity link to each other with two outputs of the auxiliary power supply end of AC/DC module respectively; Two inputs that dim signal produces circuit link to each other with the two ends of second electric capacity respectively; The output that dim signal produces circuit links to each other with the dimming interface end of DC/DC module, and the output of DC/DC module links to each other with the LED load, it is characterized in that: comprise that also one is used to control DC/DC module operating state and ability positive closing DC/DC module makes it no longer to work when the input power remove of AC/DC module enable circuits; The input of this enable circuits is connected the two ends of first electric capacity, and the output of this enable circuits links to each other with the input of DC/DC module.

Said enable circuits can have multiple structure; Wherein a kind ofly be configured to preferably: said enable circuits comprises a P type FET, a metal-oxide-semiconductor drive circuit and first resistance; Wherein, First end of first resistance links to each other with the source electrode of P type FET, and second end of first resistance links to each other with the grid of P type FET, and Q1 provides bias voltage for P type FET; The input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of P type FET; The source electrode of P type FET links to each other with the positive pole of first electric capacity, and the drain electrode of P type FET links to each other with the power input of DC/DC module.

Said metal-oxide-semiconductor drive circuit comprises second resistance; The 3rd resistance, the 4th resistance and a N type FET; Wherein first termination of second resistance links to each other with the grid of P type FET; Second end of second resistance links to each other with the drain electrode of N type FET, and first end of the 3rd resistance and the 4th resistance all links to each other with the grid of N type FET, the second end ground connection of the 3rd resistance; The input that second end of the 4th resistance is the metal-oxide-semiconductor drive circuit links to each other the source ground of N type FET with the cathode output end of the auxiliary power supply end of AC/DC module.

The principle of this scheme is: increase switching device between the supply power voltage VCC through the constant pressure source VIN that provides in the AC/DC of first order module and DC/DC module, discharge into 0 or before with the power supply positive closing of DC/DC module at C2.

A kind ofly in addition be configured to preferably: said enable circuits comprises a N type FET, metal-oxide-semiconductor drive circuit, the 5th resistance and the 6th resistance; Wherein the input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of N type FET; The drain electrode of N type FET links to each other with the positive pole of first electric capacity after connecting the 5th resistance; The source electrode of N type FET connects ground connection behind the 6th resistance, and the source electrode of N type FET also links to each other with the ON/OFF pin of DC/DC module; The power input of DC/DC module links to each other with the positive pole of first electric capacity.

Said metal-oxide-semiconductor drive circuit comprises the 7th resistance and the 8th circuit; Wherein first end of the 7th resistance and the 8th resistance all links to each other with the grid of N type FET; The input that the second end ground connection of the 7th resistance, second end of the 8th resistance are the metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module.

The principle of this scheme is: the ON/OFF function that itself has through the DC/DC module, increase switching device, and discharge into 0 or at C2 before with the DC/DC decapacitation, it is no longer worked.

Compared with prior art; The advantage of the utility model is: through the enable circuits that is provided for controlling DC/DC module operating state and can positive closing DC/DC modular power source when the input power remove of AC/DC module, thereby occur the phenomenon of flicker when can thoroughly solve the shutdown of LED power supply.

Description of drawings

Fig. 1 is the circuit theory diagrams of the utility model embodiment one.

Fig. 2 is the circuit theory diagrams of the utility model embodiment two.

Embodiment

Embodiment describes in further detail the utility model below in conjunction with accompanying drawing.

Embodiment one:

Referring to LED anti-flicker circuit shown in Figure 1; Comprise the AC/DC module, the DC/DC module, dim signal produces circuit; First capacitor C 1; Second capacitor C 2 be used to control DC/DC module operating state and when the input power remove of AC/DC module the enable circuits of ability positive closing DC/DC modular power source, wherein the input of AC/DC module links to each other with external civil power, the two ends of first capacitor C 1 respectively with two output VIN+ of the main feeder ear of AC/DC module/-link to each other; The two ends of second capacitor C 2 respectively with two output VCC1+ of the auxiliary power supply end of AC/DC module/-link to each other; Two inputs that dim signal produces circuit link to each other with the two ends of second capacitor C 2 respectively, and the output OUT that dim signal produces circuit links to each other with the dimming interface end DIM of DC/DC module, and the output of DC/DC module links to each other with the LED load; The input of said enable circuits is connected the two ends of first capacitor C 1, and the output of said enable circuits links to each other with the input of DC/DC module.

Said enable circuits comprises a P type FET Q1 and a metal-oxide-semiconductor drive circuit; And first resistance R 1; Wherein first end of first resistance R 1 links to each other with the source electrode of P type FET Q1, and second end of first resistance R 1 links to each other with the grid of P type FET Q1, and Q1 provides bias voltage for P type FET; The input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end VCC1+ of the auxiliary power supply end of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of P type FET, and the source electrode of P type FET links to each other with the positive pole of first capacitor C 1, and the drain electrode of P type FET links to each other with the power input of DC/DC module.

Said metal-oxide-semiconductor drive circuit comprises second resistance R 2; The 3rd resistance R 3 and the 4th resistance R 4; N type FET Q2, wherein first end of second resistance R 2 links to each other with the grid of P type FET Q1, and second end of second resistance R 2 links to each other with the drain electrode of N type FET Q2; First end of the 3rd resistance R 3 and the 4th resistance R 4 all links to each other with the grid of N type FET Q2; The input that the second end ground connection of the 3rd resistance R 3, second end of the 4th resistance R 4 are the metal-oxide-semiconductor drive circuit links to each other the direct ground connection of source electrode of N type FET Q2 with the cathode output end VCC1+ of the auxiliary power supply end of AC/DC module.

Because more than the big several times of Capacity Ratio second capacitor C 2 of first capacitor C 1, P type FET Q1 is connected between VIN and the VCC, and the voltage of VIN will be higher than VCC1; Energy stored (1/2CU2) will be far longer than energy stored on second capacitor C 2 on first capacitor C 1 so, in the time of operate as normal, and N type FET Q2 conducting; Because the direct ground connection of source electrode of Q2, the grid of P type FET Q1 is pulled to ground, because P type FET is the negative pressure conducting; So Q1 conducting in this time, and when mains switch turn-offs, first capacitor C 1, second capacitor C 2 begin discharge; The velocity of discharge of second capacitor C 2 will be faster than first capacitor C 1; When second capacitor C 2 discharged into to a certain degree, this degree was determined that by the high level thresholding VOH of the dimming interface end DIM of DC/DC module the high level voltage that is input to dimming interface end DIM pin when working at ordinary times will be higher than VOH; And between also have certain pressure reduction; When second capacitor C 2 discharges into VOH or a little more than VOH the time, just should the level of the output drive of metal-oxide-semiconductor drive circuit be drawn high, P type FET Q1 is ended; The input terminal voltage VCC of DC/DC module is cut off; Even voltage is still far above VCCmin (the minimum cut-in voltage that the DC/DC module will be worked) on this time first capacitor C 1, but a back level DC/DC circuit no longer works, synchronous when the voltage of the cut-off point of the main key point P type FET Q1 of this scheme and the dimming interface end DIM of DC/DC module drops to VOH; When both reach synchronous fully, just can thoroughly solve the phenomenon that the power remove lamp dodges.

Embodiment two:

Different with embodiment one is; Said enable circuits comprises a N type FET Q3, metal-oxide-semiconductor drive circuit, the 5th resistance R 5 and the 6th resistance R 6; Wherein the input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end in the auxiliary power supply source of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of N type FET Q3; The drain electrode of N type FET Q3 connects the 5th resistance R 5 backs and links to each other with the positive pole of first electric capacity, and the source electrode of N type FET Q3 connects the 6th resistance R 6 back ground connection, and the source electrode of N type FET also links to each other with the ON/OFF pin of DC/DC module; The power input of DC/DC module links to each other with the positive pole of first electric capacity.

Said metal-oxide-semiconductor drive circuit comprises the 7th resistance R 7 and the 8th resistance R 8; Wherein first end of the 7th resistance R 7 and the 8th resistance R 8 all links to each other with the grid of N type FET Q3; The input that the second end ground connection of the 7th resistance R 7, second end of the 8th resistance R 8 are the metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module.

The same with embodiment one; More than the big several times of the Capacity Ratio C2 of first capacitor C 1; N type FET Q3 is used to control the ON/OFF pin of DC/DC module, and the ON/OFF pin is pulled down to ground by the 6th resistance R 6 when N type FET Q3 ends, and the DC/DC circuit is just by decapacitation; The technical essential of this scheme is the same with scheme 1; When the voltage of the cut-off point of N type FET Q3 and the dimming interface end DIM of DC/DC module drops to VOH synchronously, when both reach synchronous fully, just can thoroughly solve the phenomenon of power remove lamp sudden strain of a muscle.

Claims

1. a LED anti-flicker circuit comprises the AC/DC module, the DC/DC module; Dim signal produces circuit; First electric capacity, second electric capacity, wherein the input of AC/DC module links to each other with external civil power; The two ends of first electric capacity link to each other with two outputs of the main feeder ear of AC/DC module respectively; The two ends of second electric capacity link to each other with two outputs of the auxiliary power supply end of AC/DC module respectively, and two inputs that dim signal produces circuit link to each other with the two ends of second electric capacity respectively, and the output of dim signal generation circuit links to each other with the dimming interface end of DC/DC module; The output of DC/DC module links to each other with the LED load; It is characterized in that: also comprise one be used to control DC/DC module operating state and can positive closing DC/DC modular power source when the input power remove of AC/DC module make it no longer to work enable circuits, the input of this enable circuits is connected the two ends of first electric capacity, the output of this enable circuits links to each other with the input of DC/DC module.

2. LED anti-flicker circuit according to claim 1; It is characterized in that: said enable circuits comprises a P type FET (Q1), a metal-oxide-semiconductor drive circuit and first resistance (R1); Wherein, First end of first resistance (R1) links to each other with the source electrode of P type FET (Q1), and second end of first resistance (R1) links to each other with the grid of P type FET (Q1); The input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of P type FET; The source electrode of P type FET links to each other with the positive pole of first electric capacity, and the drain electrode of P type FET links to each other with the power input of DC/DC module.

3. LED anti-flicker circuit according to claim 2; It is characterized in that: said metal-oxide-semiconductor drive circuit comprises second resistance (R2); The 3rd resistance (R3), the 4th resistance (R4) and a N type FET (Q2); Wherein first end of second resistance (R2) links to each other with the grid of P type FET (Q1); Second end of second resistance (R2) links to each other with the drain electrode of N type FET (Q2), and first end of the 3rd resistance (R3) and the 4th resistance (R4) all links to each other with the grid of N type FET (Q2), the second end ground connection of the 3rd resistance (R3); The input that second end of the 4th resistance (R4) is the metal-oxide-semiconductor drive circuit links to each other the source ground of N type FET (Q2) with the cathode output end of the auxiliary power supply end of AC/DC module.

4. LED anti-flicker circuit according to claim 1; It is characterized in that: said enable circuits comprises a N type FET (Q3), metal-oxide-semiconductor drive circuit, the 5th resistance (R5) and the 6th resistance (R6); Wherein the input of metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module; The output of metal-oxide-semiconductor drive circuit links to each other with the grid of N type FET (Q3); (R5) linked to each other with the positive pole of first electric capacity after the drain electrode of N type FET (Q3) connected the 5th resistance, and the source electrode of N type FET (Q3) connects the 6th resistance (R6) back ground connection, and the source electrode of N type FET (Q3) also links to each other with the ON/OFF pin of DC/DC module; The power input of DC/DC module links to each other with the positive pole of first electric capacity.

5. LED anti-flicker circuit according to claim 4; It is characterized in that: said metal-oxide-semiconductor drive circuit comprises the 7th resistance (R7) and the 8th circuit (R8); Wherein first end of the 7th resistance (R7) and the 8th resistance (R8) all links to each other with the grid of N type FET (Q3); The input that the second end ground connection of the 7th resistance (R7), second end of the 8th resistance (R8) are the metal-oxide-semiconductor drive circuit links to each other with the cathode output end of the auxiliary power supply end of AC/DC module.