CN102281683B

CN102281683B - LED anti-flash circuit

Info

Publication number: CN102281683B
Application number: CN201110218480.5A
Authority: CN
Inventors: 吴其志; 汪彪; 林万炯
Original assignee: Individual
Current assignee: Ningbo Self Electronics Co Ltd
Priority date: 2011-07-28
Filing date: 2011-07-28
Publication date: 2014-03-12
Anticipated expiration: 2031-07-28
Also published as: CN102281683A

Abstract

The invention relates to an LED anti-flicker circuit, comprising an AC/DC module, a DC/DC module, a dimming signal generating circuit, a first capacitor, a second capacitor, the input end of the AC/DC module is connected to an external mains, and the first The two ends of the capacitor are respectively connected to the two output ends of the main power supply end of the AC/DC module, the two ends of the second capacitor are respectively connected to the two output ends of the auxiliary power supply end of the AC/DC module, and the two input ends of the dimming signal generating circuit are respectively It is connected to both ends of the second capacitor, the output end of the dimming signal generating circuit is connected to the dimming interface end of the DC/DC module, and the output end of the DC/DC module is connected to the LED load. It is characterized in that: it also includes a An enabling circuit that controls the working state of the DC/DC module and can forcibly turn off the DC/DC module power supply when the input power supply of the AC/DC module is turned off, the input terminal of the enabling circuit is connected to both ends of the first capacitor, the The output terminal of the enabling circuit is connected with the output terminal of the DC/DC module. Compared with the prior art, the invention can thoroughly solve the flickering phenomenon when the LED power supply is turned off.

Description

A kind of LED anti-flicker circuit

Technical field

The present invention 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 DC/DC module two-stage dimming power source as LED driving power when input power supply is closed, prevent the circuit of LED flicker.

Background technology

Existing LED light regulating technology mainly divides two classes from the signal generation principle of light modulation: the one, and simulation light modulation, the 2nd, PWM light modulation, the two all needs extra circuit module to go to realize, and this just needs the support of extra power supply circuits.The conventional employing first order is that AC/DC module, the second level adopt in the two-stage dimming power source of DC/DC module, the first order is AC/DC module above, for generation of constant pressure source, this voltage source is as the supply power voltage of DC/DC module, the DC/DC module of the second level, for driving LED, makes it to be operated in constant current state.The power supply of dim signal circuit for generating can directly hang on the constant pressure source of AC/DC module generation, mode by step-down is got, the power supply of the power supply of DC/DC module and dim signal circuit for generating is synchronous like this, just do not have the scintillation of switching on and shutting down, but because there is the dividing potential drop of resistance, unloaded power consumption can be larger like this.Another kind of scheme is to increase auxiliary power supply system in first order AC/DC module, dim signal circuit for generating is powered by auxiliary power supply system, no-load power consumption can reach lower state (<0.5W) like this, but because the Capacity Ratio of the filter capacitor C1 of first order AC/DC module output is larger, more than the large several times of capacity of the filter capacitor C2 of the electric power system of dim signal circuit for generating, once power remove (being that civil power is no longer powered to 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 time, LED lamp is because electric current is smaller, brightness is just darker, the voltage of output is also lower, this time, C2 discharged into O, the signal of light modulation has not just had, DC/DC module just returns to common mode of operation, now the upper voltage of C1 is still very high, and higher than the minimum supply power voltage of DC/DC chip, LED is breakdown again so, be operated in normal condition, and brightness necessarily than light modulation to the darkest bright, although the time is very of short duration, but when being exactly shutoff, phenomenon can glimmer, or under several, that gives people feels very uncomfortable.

Summary of the invention

Technical problem to be solved by this invention be for above-mentioned prior art provide a kind of adopt the first order be AC/DC module, the second level adopt DC/DC module two-stage dimming power source as LED driving power when input power supply is closed, prevent the LED anti-flicker circuit of LED flicker.

The present invention solves the problems of the technologies described above adopted technical scheme: this LED anti-flicker circuit, comprise AC/DC module, DC/DC module, dim signal produces circuit, the first electric capacity, the second electric capacity, wherein the input of AC/DC module is connected with external civil power, the two ends of the first electric capacity are connected with two outputs of the main feeder ear of AC/DC module respectively, the two ends of the second electric capacity are connected with two outputs of the auxiliary power supply end of AC/DC module respectively, two inputs that dim signal produces circuit are connected with the two ends of the second electric capacity respectively, dim signal produces the output of circuit and the dimming interface end of DC/DC module is connected, the output of DC/DC module is connected with LED load, it is characterized in that: also comprise that one for controlling DC/DC module operating state, and the enable circuits that energy positive closing DC/DC module makes it no longer to work when the input power of AC/DC module turn-offs, the input of this enable circuits is connected to one end of the first electric capacity, the output of this enable circuits is connected with the input of DC/DC module.

Described enable circuits can have multiple structure, wherein a kind ofly be configured to preferably: described enable circuits comprises a P type field effect transistor, a metal-oxide-semiconductor drive circuit and the first resistance, wherein, the first end of the first resistance is connected with the source electrode of P type field effect transistor, the second end of the first resistance is connected with the grid of P type field effect transistor, and for P type field effect transistor, Q1 provides bias voltage; The input of metal-oxide-semiconductor drive circuit is connected with the cathode output end of the auxiliary power supply end of AC/DC module, the output of metal-oxide-semiconductor drive circuit is connected with the grid of P type field effect transistor, the source electrode of P type field effect transistor is connected with the positive pole of the first electric capacity, and the drain electrode of P type field effect transistor is connected with the power input of DC/DC module.

Described metal-oxide-semiconductor drive circuit comprises the second resistance, the 3rd resistance, the 4th resistance and a N-type field effect transistor, wherein the first termination of the second resistance is connected with the grid of P type field effect transistor, the second end of the second resistance is connected with the drain electrode of N-type field effect transistor, the first end of the 3rd resistance and the 4th resistance is all connected with the grid of N-type field effect transistor, the second end ground connection of the 3rd resistance, the cathode output end that the second end of the 4th resistance is the input of metal-oxide-semiconductor drive circuit and the auxiliary power supply end of AC/DC module is connected, the source ground of N-type field effect transistor.

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

Another is configured to preferably: described enable circuits comprises a N-type field effect transistor, metal-oxide-semiconductor drive circuit, the 5th resistance and the 6th resistance, wherein the input of metal-oxide-semiconductor drive circuit is connected with the cathode output end of the auxiliary power supply end of AC/DC module, the output of metal-oxide-semiconductor drive circuit is connected with the grid of N-type field effect transistor, the drain electrode of N-type field effect transistor is connected with the positive pole of the first electric capacity after connecting the 5th resistance, ground connection after source electrode connection the 6th resistance of N-type field effect transistor, and the source electrode of N-type field effect transistor is also connected with the ON/OFF pin of DC/DC module; The power input of DC/DC module is connected with the positive pole of the first electric capacity.

Described metal-oxide-semiconductor drive circuit comprises the 7th resistance and the 8th circuit, wherein the first end of the 7th resistance and the 8th resistance is all connected with the grid of N-type field effect transistor, the second end ground connection of the 7th resistance, the cathode output end that the second end of the 8th resistance is the input of metal-oxide-semiconductor drive circuit and the auxiliary power supply end of AC/DC module is connected.

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

Compared with prior art, the invention has the advantages that: by 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 of AC/DC module turn-offs, thereby when can thoroughly solve the shutdown of LED power supply, occur the phenomenon of flicker.

Accompanying drawing explanation

Fig. 1 is the circuit theory diagrams of the embodiment of the present invention one.

Fig. 2 is the circuit theory diagrams of the embodiment of the present invention two.

Embodiment

Below in conjunction with accompanying drawing, embodiment is described in further detail the present invention.

Embodiment mono-:

LED anti-flicker circuit shown in Figure 1, comprise AC/DC module, DC/DC module, dim signal produces circuit, the first capacitor C 1, the second capacitor C 2 and for controlling DC/DC module operating state, and the enable circuits of energy positive closing DC/DC modular power source when the input power of AC/DC module turn-offs, wherein the input of AC/DC module is connected with external civil power, the two ends of the first capacitor C 1 respectively with two output VIN+ of the main feeder ear of AC/DC module/-be connected, the two ends of the second capacitor C 2 respectively with two output VCC1+ of the auxiliary power supply end of AC/DC module/-be connected, two inputs that dim signal produces circuit are connected with the two ends of the second capacitor C 2 respectively, dim signal produces the output OUT of circuit and the dimming interface end DIM of DC/DC module is connected, the output of DC/DC module is connected with LED load, the input of described enable circuits is connected to one end of the first capacitor C 1, the output of described enable circuits is connected with the input of DC/DC module.

Described enable circuits comprises a P type field effect transistor Q1 and a metal-oxide-semiconductor drive circuit, and first resistance R 1, wherein the first end of the first resistance R 1 is connected with the source electrode of P type field effect transistor Q1, the second end of the first resistance R 1 is connected with the grid of P type field effect transistor Q1, for P type field effect transistor, Q1 provides bias voltage, the input of metal-oxide-semiconductor drive circuit is connected with the cathode output end VCC1+ of the auxiliary power supply end of AC/DC module, the output of metal-oxide-semiconductor drive circuit is connected with the grid of P type field effect transistor, the source electrode of P type field effect transistor is connected with the positive pole of the first capacitor C 1, the drain electrode of P type field effect transistor is connected with the power input of DC/DC module.

Described metal-oxide-semiconductor drive circuit comprises the second resistance R 2, the 3rd resistance R 3 and the 4th resistance R 4, N-type field effect transistor Q2, wherein the first end of the second resistance R 2 is connected with the grid of P type field effect transistor Q1, the second end of the second resistance R 2 is connected with the drain electrode of N-type field effect transistor Q2, the first end of the 3rd resistance R 3 and the 4th resistance R 4 is all connected with the grid of N-type field effect transistor Q2, the second end ground connection of the 3rd resistance R 3, the cathode output end VCC1+ that the second end of the 4th resistance R 4 is the input of metal-oxide-semiconductor drive circuit and the auxiliary power supply end of AC/DC module is connected, the direct ground connection of source electrode of N-type field effect transistor Q2.

More than the large several times due to Capacity Ratio second capacitor C 2 of the first capacitor C 1, P type field effect transistor Q1 is connected between VIN and VCC, and the voltage of VIN will be higher than VCC1, the energy (1/2CU2) storing in the first capacitor C 1 so will be far longer than the energy storing in the second capacitor C 2, in the time of normal operation, N-type field effect transistor Q2 conducting, the direct ground connection of source electrode due to Q2, the grid of P type field effect transistor Q1 is pulled to ground, because P type field effect transistor is negative pressure conducting, so Q1 conducting in this time, and when mains switch turn-offs, the first capacitor C 1, the second capacitor C 2 starts electric discharge, the velocity of discharge of the second capacitor C 2 will be faster than the first capacitor C 1, when the second capacitor C 2 discharges into a certain degree, this degree is determined 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 the second capacitor C 2 discharges into VOH or a little more than VOH time, just the level of the output drive of metal-oxide-semiconductor drive circuit should be drawn high, make P type field effect transistor Q1 cut-off, the input terminal voltage VCC of DC/DC module is cut off, even voltage or far above VCCmin (the minimum cut-in voltage that DC/DC module will be worked) in this time first capacitor C 1, but rear class DC/DC circuit is no longer worked, the synchronous when cut-off point of main key point P type field effect transistor Q1 of this scheme and the voltage of the dimming interface end DIM of DC/DC module drop to VOH, when both reach Complete Synchronization, just can thoroughly solve the phenomenon that power remove lamp dodges.

Embodiment bis-:

Different from embodiment mono-is, described enable circuits comprises a N-type field effect transistor 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 is connected with the cathode output end in the auxiliary power supply source of AC/DC module, the output of metal-oxide-semiconductor drive circuit is connected with the grid of N-type field effect transistor Q3, the drain electrode of N-type field effect transistor Q3 is connected with the positive pole of the first electric capacity after connecting the 5th resistance R 5, the source electrode of N-type field effect transistor Q3 connects the rear ground connection of the 6th resistance R 6, and the source electrode of N-type field effect transistor is also connected with the ON/OFF pin of DC/DC module, the power input of DC/DC module is connected with the positive pole of the first electric capacity.

Described metal-oxide-semiconductor drive circuit comprises the 7th resistance R 7 and the 8th resistance R 8, wherein the first end of the 7th resistance R 7 and the 8th resistance R 8 is all connected with the grid of N-type field effect transistor Q3, the second end ground connection of the 7th resistance R 7, the cathode output end that the second end of the 8th resistance R 8 is the input of metal-oxide-semiconductor drive circuit and the auxiliary power supply end of AC/DC module is connected.

The same with embodiment mono-, more than the large several times of the Capacity Ratio C2 of the first capacitor C 1, N-type field effect transistor Q3 is for controlling the ON/OFF pin of DC/DC module, when N-type field effect transistor Q3 ends, ON/OFF pin is pulled down to ground by the 6th resistance R 6, DC/DC circuit is just by decapacitation, the technical essential of this scheme is the same with scheme 1, the synchronous when voltage of the dimming interface end DIM of the cut-off point of N-type field effect transistor Q3 and DC/DC module drops to VOH, when both reach Complete Synchronization, just can thoroughly solve the phenomenon that power remove lamp dodges.

Claims

1. An LED anti-flicker circuit, including an AC/DC module, a DC/DC module, a dimming signal generating circuit, a first capacitor, and a second capacitor, wherein the input terminal of the AC/DC module is connected to an external mains power supply, and the first The two ends of the capacitor are respectively connected to the two output ends of the main power supply end of the AC/DC module, the two ends of the second capacitor are respectively connected to the two output ends of the auxiliary power supply end of the AC/DC module, and the two input ends of the dimming signal generating circuit are respectively It is connected to both ends of the second capacitor, the output end of the dimming signal generating circuit is connected to the dimming interface end of the DC/DC module, and the output end of the DC/DC module is connected to the LED load. It is characterized in that it also includes a An enabling circuit that controls the working state of the DC/DC module and can forcibly shut down the power supply of the DC/DC module to make it no longer work when the input power of the AC/DC module is turned off. The input terminal of the enabling circuit is connected to the first The positive pole of the capacitor, the output end of the enabling circuit is connected to the input end of the DC/DC module; the enabling circuit includes a P-type field effect transistor (Q1), a MOS transistor driving circuit and a first resistor (R1), Wherein, the first end of the first resistor (R1) is connected to the source of the P-type field effect transistor (Q1), and the second end of the first resistor (R1) is connected to the gate of the P-type field effect transistor (Q1); The input terminal of the MOS tube drive circuit is connected to the positive output terminal of the auxiliary power supply terminal of the AC/DC module, the output terminal of the MOS tube drive circuit is connected to the gate of the P-type field effect tube, and the source of the P-type field effect tube is connected to the first The positive electrode of the capacitor is connected, and the drain of the P-type field effect transistor is connected with the power input terminal of the DC/DC module; the MOS transistor driving circuit includes a second resistor (R2), a third resistor (R3), a fourth resistor (R4 ) and an N-type field effect transistor (Q2), wherein the first end of the second resistor (R2) is connected to the gate of the P-type field effect transistor (Q1), and the second end of the second resistor (R2) is connected to the N-type The drain of the field effect transistor (Q2) is connected, the first ends of the third resistor (R3) and the fourth resistor (R4) are connected with the gate of the N-type field effect transistor (Q2), and the third resistor (R3) The second end is grounded, the second end of the fourth resistor (R4) is the input end of the MOS transistor drive circuit and is connected to the positive output end of the auxiliary power supply end of the AC/DC module, and the source of the N-type field effect transistor (Q2) is grounded .

2. An LED anti-flicker circuit, including an AC/DC module, a DC/DC module, a dimming signal generating circuit, a first capacitor, and a second capacitor, wherein the input end of the AC/DC module is connected to an external mains, and the first The two ends of the capacitor are respectively connected to the two output ends of the main power supply end of the AC/DC module, the two ends of the second capacitor are respectively connected to the two output ends of the auxiliary power supply end of the AC/DC module, and the two input ends of the dimming signal generating circuit are respectively It is connected to both ends of the second capacitor, the output end of the dimming signal generating circuit is connected to the dimming interface end of the DC/DC module, and the output end of the DC/DC module is connected to the LED load. It is characterized in that it also includes a An enabling circuit that controls the working state of the DC/DC module and can forcibly shut down the power supply of the DC/DC module to make it no longer work when the input power of the AC/DC module is turned off. The input terminal of the enabling circuit is connected to the first The positive electrode of the capacitor, the output end of the enabling circuit is connected to the input end of the DC/DC module; the enabling circuit includes an N-type field effect transistor (Q3), a MOS transistor driving circuit, a fifth resistor (R5) and a first Six resistors (R6), in which the input end of the MOS transistor drive circuit is connected to the positive output end of the auxiliary power supply end of the AC/DC module, and the output end of the MOS transistor drive circuit is connected to the gate of the N-type field effect transistor (Q3), N The drain of the N-type field effect transistor (Q3) is connected to the fifth resistor (R5) and the positive electrode of the first capacitor, the source of the N-type field effect transistor (Q3) is connected to the sixth resistor (R6) and grounded, and the N-type The source of the field effect transistor (Q3) is also connected to the ON/OFF pin of the DC/DC module; the power input terminal of the DC/DC module is connected to the positive pole of the first capacitor; the MOS transistor drive circuit includes a seventh resistor (R7 ) and the eighth circuit (R8), wherein the first ends of the seventh resistor (R7) and the eighth resistor (R8) are connected to the gate of the N-type field effect transistor (Q3), and the first end of the seventh resistor (R7) Two terminals are grounded, and the second terminal of the eighth resistor (R8) is the input terminal of the MOS transistor drive circuit and is connected to the positive output terminal of the auxiliary power supply terminal of the AC/DC module.