CN206640831U - A kind of LED linear constant current soft start drive circuit - Google Patents

Abstract

The utility model discloses a kind of LED linear constant current soft start drive circuit,Including rectification circuit,Performance loop,Constant-current control circuit,Voltage detecting circuit,Soft starting circuit and external control circuit,Using extremely simple circuit design,Solves complex technical problem,With simple circuit,Without EMI,Constant current accuracy is high,The advantages that larger scope range of the fluctuation of voltage can be born,Also there is function of temperature compensation control function,Soft start function and external dimmer function,The intelligent control of LED lamp and wireless Internet of Things can conveniently be realized,Improve the combination property of driver and cost is declined to a great extent,Special integrated LED driving chip can be made,Both layout design is simplified,Also substantially reduce the cost of integrated circuit,And function and performance have reached the grade that extremely complex circuit design can be completed.

Description

A kind of LED linear constant current soft start drive circuit

Technical field

A kind of LED drive circuit is the utility model is related to, particularly a kind of LED constant current soft start drive circuit.

Background technology

LED illumination lamp has the advantages that energy-conservation, service life is long has come into huge numbers of families, in the prior art, LED The type of drive of illuminator have it is a variety of, wherein, linear constant current driving is because circuit is simple, no EMI and cheap extensive Use, however, linear constant current driving there is also some it is fatal the shortcomings that.

Power device in being driven due to linear constant current is connected with LED load, and power device is under linear condition and worked, Power device both ends need to bear certain pressure difference, and power caused by this pressure difference is reactive power, is driven by linear constant current In power device (be usually MOSFET or other semiconductor power devices) absorb, linear constant current namely passes through adjustment circuit The size of middle pressure difference controls the electric current of LED load to reach constant current purpose.Although in the circuit design of LED lamp, can use up Amount improves load voltage and reduces pressure difference, to reduce power consumption and improve efficiency, in supply voltage more stable area, using being Have no problem, but used in the larger area of voltage ripple of power network amplitude completely, when voltage is increased beyond certain amplitude, can be made The reactive power of light fixture rises violently, except electrical efficiency declines, it is often more important that can influence the service life of light fixture.

Linear constant current driving belongs to non-isolated topological structure, in the application field of LED illumination product, substantially in civil power Worked in the state of direct voltage driving, based on the characteristic of civil power sine wave, line voltage is after over commutation, its direct current peak value Voltage is 1.414 times of input voltage, and the crest voltage of the voltage of LED load and power supply is there is larger pressure difference, therefore Light fixture powered on moment, the electric current being loaded onto in LED load can produce the surge pulse of more than a 5 times operating current, LED born Load causes very big rush of current, although the time is very short (about 100ms), this is for LED load, the defects of being fatal, Frequently switch can make LED life by strong influence.

In order to solve rush of current this problem, a kind of current way is the access filtering electrolysis in supplying DC loop Electric capacity, or in LED load both ends parallel electrolytic electric capacity, surge current is absorbed using the upper electric damping characteristics of electrochemical capacitor, but Added in the major loop of circuit after electrochemical capacitor, can be greatly reduced the power factor of circuit, generally, without electricity The linear drive circuit of electric capacity is solved, its power factor is added after electrochemical capacitor typically more than 0.95, and its power factor is just Less than 0.6 can be dropped to.In addition, need the regular hour to finish the electric energy release of inside after electrochemical capacitor power-off, If re-powered at once after power-off or certain reason switch when upper electric is shaken, above-mentioned damping characteristics are with regard to complete Failure, moreover, increase electrochemical capacitor, can rise the cost of product, volume increase.Current another way is born in LED Carry both ends and meet Transient Suppression Diode TVS, although so can effectively suppress upper electric transient pulse, soft open can not be realized It is dynamic, further, since Transient Suppression Diode TVS costs are high, seldom it is used at present.

In addition, some LED linear constant-current drive circuits have external dimmer interface at present, it can be entered using single-chip microcomputer Dimming function is realized in the adjustment of row PWM or linear level, but its circuit is complicated, and needs to solve special steady of a single-chip microcomputer Voltage source, cost is high, and this method is typically only used on the light fixture product of intelligent control.

The content of the invention

For overcome the deficiencies in the prior art, the utility model provides a kind of simple circuit, energy high without EMI, constant current accuracy Larger scope range of the fluctuation of voltage is born, the LED linear with function of temperature compensation control function, soft start function and external dimmer function Constant current soft start drive circuit.

Technical scheme is used by the utility model solves its technical problem：

A kind of LED linear constant current soft start drive circuit, including：

Performance loop:Including FET T1, the drain D of the FET T1 connected with LED load be followed by it is described straight The positive pole of power supply is flowed, the drain D of the FET T1 and the contact of LED load are named as node 6；The FET T1's Source S is connect publicly by resistance R2, and grid G connects the node 6, the resistance R1 and FET T1 grid by resistance R1 Pole G contact is named as node 7, and the contact of the resistance R2 and FET T1 source S is named as node 10.

Soft starting circuit：Including charging and discharging circuit, charging and discharging circuit connects the contact 7 by one-way isolation circuit.

The charging and discharging circuit includes resistance R7 and electric capacity C1, and the one-way isolation circuit includes diode D5, the electricity Hinder R7 and electric capacity C1 latter terminations in parallel publicly, another termination diode D5 negative pole, the positive pole of the diode D5 Connect the node 7.

Further, drive circuit of the present utility model also includes external control circuit, the external control circuit with it is described Node 7 is connected.

The emitter E that the external control circuit includes PNP type triode T4, the triode T4 connects the node 7, collects Electrode C connects publicly, and base stage B divides two-way, connects the node 7 by resistance R5 all the way, and another way connects outside by diode D6 Signal control terminal.

The base stage B of the triode T4 and publicly between be connected with light adjusting circuit, the light adjusting circuit be potentiometer W or Photo resistance.

Further, drive circuit of the present utility model also includes constant-current control circuit, and the constant-current control circuit includes NPN Type triode T2, the triode T2 base stage B connect the node 10, and colelctor electrode C connects the node 7, and emitter E connects public Ground.

Further, drive circuit of the present utility model also includes voltage detecting circuit, and the voltage detecting circuit includes electricity R3, resistance R4 and NPN type triode T3 are hindered, after resistance R3 and resistance the R4 series connection, a termination node 6, another termination Publicly, wherein, resistance R3 and resistance R4 contact are named as node 11；The base stage B of the triode T3 connects the node 11, Colelctor electrode C connects the node 7 by resistance R6, and emitter E connects publicly.

The node 7 and publicly between be connected with temperature-compensation circuit.

The beneficial effects of the utility model are：The utility model uses extremely simple circuit design, solves more multiple Miscellaneous technical problem, there is simple circuit, high without EMI, constant current accuracy, the advantages that larger scope range of the fluctuation of voltage can be born, With function of temperature compensation control function, soft start function and external dimmer function, can conveniently realize LED lamp intelligent control and Wireless Internet of Things, improve the combination property of driver and cost is declined to a great extent, special integrated LED driving core can be made Piece, both simplifies layout design, also substantially reduces the cost of integrated circuit, and function and performance have reached extremely complex The grade that circuit design can be completed.

Brief description of the drawings

The utility model is further illustrated with reference to the accompanying drawings and examples.

Fig. 1 is the first embodiment circuit diagram of the present utility model；

Fig. 2 is second of embodiment circuit diagram of the present utility model；

Fig. 3 is the third embodiment circuit diagram of the present utility model.

Embodiment

Referring to figs. 1 to Fig. 3, a kind of LED linear constant current soft start drive circuit, including：

Performance loop:Including FET T1, the drain D of the FET T1 and LED load (node 5 and node 6 it Between be LED load) series connection is followed by the positive pole of the dc source (rectifier bridge that dc source is made up of commutation diode D1-D4) (node 4), describe for convenience, the drain D of the FET T1 and the contact of LED load are named as node 6.The field effect Should pipe T1 source S connect publicly (node 9) by resistance R2, grid G meets the node 6, the resistance R1 by resistance R1 Node 7, the contact of the resistance R2 and FET T1 source S are named as with the contact of FET T1 grid G It is named as node 10.

Soft starting circuit：Including charging and discharging circuit, charging and discharging circuit connects the contact 7, tool by one-way isolation circuit For body, the charging and discharging circuit includes resistance R7 and electric capacity C1, and the one-way isolation circuit includes diode D5, the resistance Publicly, another termination diode D5 negative pole, the positive pole of the diode D5 connects R7 and electric capacity C1 latter terminations in parallel The node 7.

External control circuit：The external control circuit is connected with the node 7, specifically, the outside control electricity The emitter E that road includes PNP type triode T4, the triode T4 connects the node 7, and colelctor electrode C connects publicly, B points of base stage Two-way, connects the node 7 by resistance R5 all the way, and another way connects external signal control terminal (node 12) by diode D6.

Constant-current control circuit：Including NPN type triode T2, the base stage B of the triode T2 connects the node 10, colelctor electrode C connects the node 7, and emitter E connects publicly.

Voltage detecting circuit：Including resistance R3, resistance R4 and NPN type triode T3, resistance R3 and resistance the R4 series connection Afterwards, a termination node 6, it is another to terminate publicly, wherein, resistance R3 and resistance R4 contact are named as node 11；It is described Triode T3 base stage B connects the node 11, and colelctor electrode C connects the node 7 by resistance R6, and emitter E connects publicly.

The node 7 and publicly between be connected with temperature-compensation circuit.

The present embodiment illustrates operation principle of the present utility model by taking the circuit shown in Fig. 1 as an example.

1. current constant control part

Realized by performance loop and constant-current control circuit, civil power (220VAC) is respectively connecting to the ac input end of rectifier bridge 1st, 2, after over commutation, a peak value is exported in the DC voltage output end 3,4 of rectifier bridge to input 1.414 times of AC voltages DC pulse moving voltage, if input voltage is AC220V, then the crest voltage of output end 3,4 is DC311.08V, passes through FET T1, resistance R2 form the working current loop of LED load.The operating current size of LED load is controlled by FET T1, and field Effect pipe T1 working condition is controlled by the constant-current control circuit being made up of triode T2, resistance R1 and resistance R2 and controlled again, electricity Resistance R1 provides an operating voltage for FET T1 grid G, the level height of this voltage, directly affects field-effect Pipe T1 output current, so, this level is efficiently controlled, also just directly controls the electric current of LED load.Resistance R2 is used for LED load electric current is detected, when electric current is by resistance R2, a voltage, the size of this voltage will be produced at resistance R2 both ends Relevant with resistance R2 resistance and the size for the electric current I for passing through resistance R2, its calculation formula is：V=IR, this voltage is by three Pole pipe T2 sampling amplifications, and control by triode T2 colelctor electrode C the working condition of FET T1 grid Gs, it is assumed that set The operating current for determining LED load is 100mA, and triode T2 magnification region window, between 0.5-0.6V, sampling voltage is set It is scheduled on 0.5V, then, according to V=IR principle, the resistance for calculating resistance R2 is 5 ohm, so, when the electricity of LED load When stream is more than setting value, sampling voltage will rise therewith in proportion, due to triode T2 amplification, its colelctor electrode C electricity Position drags down therewith, directly controls the operating voltage of FET T1 grid Gs, declines FET T1 output current；When When the electric current of LED load is less than setting value, then sampling voltage will decline therewith in proportion, due to triode T2 amplification, Triode T2 colelctor electrodes C current potential is set also to increase therewith, FET T1 output current increase, therefore, the electric current of LED load It is locked in setting value.

2nd, voltage detecting control section

Realized by voltage detecting circuit, during work, between the direct current output terminal voltage of rectification circuit and the voltage of LED load There is certain pressure difference, this pressure difference is undertaken by FET T1 and resistance R2, and pressure difference signal is also reflected directly in resistance R3 Between resistance R4, after resistance R3 and resistance R4 partial pressures, triode T3 base stage B is fed to by node 11, by three After pole pipe T3 amplifications, FET T1 grid G (node 7) is fed to by resistance R6.

Under normal circumstances, when supply voltage (AC-input voltage) changes, pressure difference also changes simultaneously, supplies In normal state, triode T3 is maintained at the lower limit of initial working region to piezoelectric voltage, and colelctor electrode C current potential is maintained at conjunction In suitable scope, FET T1 is supplied to LED load according to normal electric current.

When supply voltage is less than normal value, the current potential of node 11 declines, triode T3 cut-offs, on colelctor electrode C current potential Rise, compensate for the voltage of FET T1 grid Gs to a certain extent, so, supply voltage is fluctuated in certain amplitude downwards still FET T1 can be so kept to have stable electric current output.

If supply voltage fluctuates upwards, during more than normal value, the current potential of node 11 also rises therewith, due to triode T3 Amplification, triode T3 colelctor electrode C current potential declines, by resistance R6, dragged down the current potential of node 7, made field therewith Effect pipe T1 output current is reduced, and has effectively suppressed the rising of reactive power caused by rising due to input voltage, also greatly Big reduction FET T1 caused temperature due to idle power consumption.

Further, since resistance R3 and resistance R4 forms voltage-dividing detection circuit, resistance R3 can also be skipped to node 6, directly Node 5 (equivalent to 4 ends of rectifier bridge) is connected to, its operation principle is the same.

3rd, soft start control section

Realized by soft starting circuit, when upper electric, FET T1 operating voltage is supplied to by resistance R1, passes through two first Pole pipe D5 charges to electric capacity C1, in the moment that power supply has just been connected, the internal resistance very little at electric capacity C1 both ends, and the moment at its both ends Voltage is approximately 0V, and the voltage of FET T1 grid Gs is pulled low and is in cut-off state.With the increase in charging interval, electricity The voltage for holding C1 both ends slowly rises, and after reaching threshold value, FET T1 enters working condition, the output current of its drain D Slowly rising, the electric current of LED load also slowly rises since 0 therewith, until the current value of setting, completes soft start-up process, Resistance R7 is discharge resistance, and it is the electrical energy discharge for when power is off at once storing electric capacity C1 both ends that it, which is acted on, so as in the short time RestPosed when re-powering.Diode D5 effect is to play one-way isolation to the voltage at electric capacity C1 both ends, is avoided After completing soft start, electric capacity C1 voltage (node 8) pours in down a chimney to node 7, causes FET T1 lagss in response.

The time of soft start depends on electric capacity C1 and resistance R1 R.C time constants, selects appropriate electric capacity C1 and resistance R1 value, soft-start time can be made to be set in desired scope.

4th, temperature-compensating part

Realized by temperature-compensation circuit.Transistor all has the sensitivity characteristic to temperature, especially small-signal triode, In the present embodiment, on the one hand triode T2, triode T3 bear the current regulation to FET T1, are on the other hand even more one Individual temperature sensor of good performance, when operating temperature is more than 80 degrees Celsius, triode T2, triode T3 internal resistance will be with The rising of temperature and decline, so as to drag down the current potential of node 7, also just directly dragged down FET T1 output current, reached Arrived the effect of temperature-compensating, can also in node 7 and publicly between connect thermally sensitive element or circuit, such as temperature-sensitive Resistance etc..

5th, external control circuit part

In today of scientific and technological high development, illuminator is also fast-developing towards the direction of intelligent and wireless Internet of Things, because This, it is particularly necessary to have intelligent interface to LED driver.

A, external PWM signal inputs

Usually, when external signal control terminal (node 12) is vacant, triode T4 is in cut-off state, whole power-supply system Work it is almost unrelated with it, in the present embodiment, external signal control terminal can receive voltage amplitude for 0-5.5V, dutycycle For 0-100% pwm signal, when pwm signal accesses, triode T4 works on off state, when pwm signal is in low level When, triode T4 conductings, the level of the node 7 of internal circuit is dragged down, forces FET T1 to end, pwm signal is in height During level, then triode T4 ends, and FET T1 resumes work, and so, just makes FET T1 working condition and input Pwm signal be consistent.

B, external linear smoothly dims

Many times, it is necessary to brightness regulation be carried out to light fixture using outer member, in the present embodiment, as shown in figure 3, institute State triode T4 base stage B and publicly between be connected with light adjusting circuit, the light adjusting circuit can be potentiometer W, can also For photo resistance etc..Such as desk lamp, as long as potentiometer W to be linked into triode T4 base stage B and publicly, you can LED is born Carry the linearity light adjusting for carrying out 0-100.Potentiometer W access, a negative potential is introduced to triode T4 base stages, as potentiometer W Resistance when being in maximum position, due to the effect of pull-up resistor, three end transistor base stage B undertension is so that T4 enters work Make state, therefore triode T4 is in cut-off state, potentiometer W is adjusted, with diminishing for its resistance, triode T4 base potentials Therewith by high step-down, triode T4 enters working condition, the conducting state of the level of the node 7 in circuit also with triode T4 And change, so, the brightness of LED load with regard to Synchronization Control.

Same reason, if changing potentiometer W into a photo resistance, the bright of external environment condition is detected using photo resistance Degree, then the brightness of LED load will change with the brightness of ambient light, when external environment condition brightness abundance, photo resistance Resistance diminish, promote triode T4 saturation conductions, the current potential of node 7 moved to minimum, LED load is extinguished, and works as external rings During the brightness step-down of border, the resistance of photo resistance also becomes big therewith, and triode T4 conducting state also changes therewith, FET T1 Controlled depth also changes therewith, so as to make the brightness of LED load change with the change of ambient brightness.

In addition, external signal control terminal (node 12) is also compatible with 0-5.5V external voltage source input control, some , it is necessary to control the brightness of LED load using external voltage, this interface is still adapted in place, in this case, triode T4 is in the working region of Linear Amplifer, and for its base stage B current potentials in 5V, triode T4 is completely switched off, plus diode D6 just To pressure drop about 0.5V, it is 5.5V that it, which inputs and effectively controls level, when incoming level is 0V, the fully saturated conductings of triode T4, When input voltage changes between 0-5.5V, triode T4 conducting depth then changes with the change of voltage, so as to FET T1 output currents are controlled therewith to change.Diode D6 effect is to play one-way isolation effect, is avoided different defeated Enter voltage to have an impact circuit.

C, multiple sensors access

External signal control terminal (node 12) can the access of compatible multiple sensors, currently conventional sensor have multiple types Type and specification, such as：Infrared, ultrasonic wave, radar, photoelectricity, acoustic control etc., wherein, sensor assembly be divided into again it is active output and it is passive Two major classes, the sensor assembly of active output are exported, its output end provides a DC voltage, and height is done in sensor actuation Level switches, and its voltage output has plurality of specifications, common are 6V, 12V, 24V etc..The sensor of passive output type, typically It is to provide a group relay make and break contact, the contact is opened or closed in sensor actuation.The sensor of the above type, It is suitable for accessing in this circuit.Diode D6 effect is to carry out voltage isolation to various types of sensors, avoids different electricity Pressure has an impact to circuit.

Currently used transistor has NPN type triode, PNP type triode, N-type FET, p-type FET, specially The technical staff in industry field can be as needed from corresponding component, and according to the corresponding wiring of type change of component Mode, as used NPN triode (small-signal triode), PNP triode (small-signal triode), N-type field-effect in Fig. 1, Fig. 3 Manage, FET is used in Fig. 2, these transistors are operated under switch or Linear Amplifer state, under certain conditions, can To use different types of Replacement of Electronic Components, its circuit operation principle and function are identicals.

Drive circuit of the present utility model can be equivalent to a two end constant flow modules, during work, without being additionally provided work Make power supply, therefore its pressure difference can be made small, realize the low voltage difference concept of Linear Driving.Further, since LED load and this reality It is series relationship with new drive circuit, therefore LED load can be serially connected in the positive terminal of dc source, can also be connected on straight Flow the negative pole end of power supply.If necessary, drive circuit of the present utility model multiple can also be together in series use, to improve circuit Power consumption bearing capacity.

The utility model uses extremely simple circuit design, solves complex technical problem, improves driving The combination property of device and cost is declined to a great extent, special integrated LED driving chip can be made, both simplify layout design, Also substantially reduce the cost of integrated circuit, and function and performance have reached what extremely complex circuit design can be completed Grade, the principle based on the invention, the technical staff of professional domain can make the modification of some adaptability, as shown in Fig. 2 Increase protective tube FUSE, pressure-sensitive diode TVR etc. in circuit to increase security of circuit etc., the technical staff of professional domain The electronic component or circuit done on the premise of the invention objective is not departed from is directly replaced or equivalent variations, still belongs to Within the scope of the invention is covered.

Claims (9)

1. a kind of LED linear constant current soft start drive circuit, it is characterised in that it includes：

Performance loop:Including FET T1, the drain D of the FET T1 is connected with LED load is followed by dc source Positive pole, the drain D of the FET T1 and the contact of LED load are named as node 6；The source S of the FET T1 is led to Cross resistance R2 to connect publicly, grid G connects the node 6 by resistance R1, and the resistance R1 connects with FET T1 grid G Point is named as node 7, and the contact of the resistance R2 and FET T1 source S is named as node 10；

Soft starting circuit：Including charging and discharging circuit, charging and discharging circuit connects the contact 7 by one-way isolation circuit.

2. LED linear constant current soft start drive circuit according to claim 1, it is characterised in that the charging and discharging circuit bag Resistance R7 and electric capacity C1 are included, the one-way isolation circuit includes diode D5, the resistance R7 and electric capacity C1 latter termination in parallel Publicly, another termination diode D5 negative pole, the positive pole of the diode D5 connect the node 7.

3. LED linear constant current soft start drive circuit according to claim 1, it is characterised in that the drive circuit also includes External control circuit, the external control circuit are connected with the node 7.

4. LED linear constant current soft start drive circuit according to claim 3, it is characterised in that the external control circuit Including PNP type triode T4, the emitter E of the triode T4 connects the node 7, and colelctor electrode C connects publicly, and base stage B be divided to two Road, connects the node 7 by resistance R5 all the way, and another way connects external signal control terminal by diode D6.

5. LED linear constant current soft start drive circuit according to claim 4, it is characterised in that the base of the triode T4 Pole B and publicly between be connected with light adjusting circuit.

6. LED linear constant current soft start drive circuit according to claim 5, it is characterised in that the light adjusting circuit is electricity Position device W or photo resistance.

7. LED linear constant current soft start drive circuit according to claim 1, it is characterised in that the drive circuit also includes Constant-current control circuit, the constant-current control circuit connect the node including NPN type triode T2, the base stage B of the triode T2 10, colelctor electrode C connect the node 7, and emitter E connects publicly.

8. LED linear constant current soft start drive circuit according to claim 1, it is characterised in that the drive circuit also includes Voltage detecting circuit, the voltage detecting circuit include resistance R3, resistance R4 and NPN type triode T3, the resistance R3 and electricity After hindering R4 series connection, a termination node 6 is another to terminate publicly, wherein, resistance R3 and resistance R4 contact are named as node 11；The base stage B of the triode T3 connects the node 11, and colelctor electrode C connects the node 7 by resistance R6, and emitter E connects public Ground.

9. LED linear constant current soft start drive circuit according to claim 1, it is characterised in that the node 7 with it is public Temperature-compensation circuit is connected between ground.