CN102724797A - Light emitting diode (LED) drive circuit and LED lighting device - Google Patents

Abstract

The invention is applicable to the field of light emitting diode (LED) drive, and provides an LED drive circuit and an LED lighting device. The LED drive circuit comprises a power factor control module and a constant-current control module. The power factor control module samples a half-sinusoid electric signal outputted by a rectifier bridge circuit, generates a control signal and outputs the control signal to the constant-current control module; the constant-current control module realizes constant-current control over an LED load and ensures a high power factor; and moreover, inductive elements and a power-factor correction circuit which comprises an impulse modulator are not required, so circuit cost is reduced, and problems of complicated circuit structure and high cost in the prior art are solved.

Description

A kind of led drive circuit and LED lighting device

Technical field

The invention belongs to LED and drive the field, relate in particular to a kind of led drive circuit and LED lighting device.

Background technology

At present, LED because it has the advantage that energy consumption is low, brightness is strong and the life-span is long, has been widely used in every field as a kind of new type light source.The led drive circuit that is used for driving LED work that prior art provided mainly adopts AC-DC isolation drive mode or the non-isolation drive mode of DC-DC.

Yet; All need use like inductive elements such as transformer, inductance in above-mentioned two kinds of circuit structures that type of drive adopted; And in order to improve power factor, also need on the basis of existing constant-current control circuit, increase the circuit of power factor correction that comprises pulse modulator, make the entire circuit structure complicated more; Be unfavorable for the miniaturization of LED light fixture, and increased circuit cost.Therefore, prior art exists circuit structure complicacy and the high problem of cost.

Summary of the invention

The object of the present invention is to provide a kind of led drive circuit, be intended to guarantee to realize to solve existing in prior technology circuit structure complicacy and the high problem of cost under the prerequisite of High Power Factor and constant current output.

The present invention realizes like this; A kind of led drive circuit is connected with rectifier circuit and LED load, and said rectifier circuit converts the civil power AC signal to the half-sinusoid signal of telecommunication; The input of said LED load connects the output of said rectifier circuit, and said led drive circuit comprises:

The power factor controlling module; Be connected with the output of said rectifier circuit; Be used for the said half-sinusoid signal of telecommunication is sampled; And correspondingly generate and synchronous first in-phase electric signals of the said half-sinusoid signal of telecommunication, or generate and synchronous second in-phase electric signals of the said half-sinusoid signal of telecommunication and control level signal simultaneously;

The constant current control module is connected with said power factor controlling module and said LED load, is used for according to said first in-phase electric signals or said second in-phase electric signals and said control level signal the operating current of said LED load being adjusted.

Another object of the present invention also is to provide a kind of LED lighting device that comprises said led drive circuit.

In the present invention; Employing comprises the led drive circuit of said power factor controlling module and said constant current control module; By said power factor controlling module the half-sinusoid signal of telecommunication of said rectifier circuit output is sampled and produced control signal and output to the constant current control module; When guaranteeing High Power Factor, the LED load is realized constant current control through said constant current control module then; And need not adopt inductive element and comprise the circuit of power factor correction of pulse modulator, and then reduce circuit cost, thereby solve existing in prior technology circuit structure complicacy and the high problem of cost.

Description of drawings

Fig. 1 is the modular structure figure of the led drive circuit that provides of first embodiment of the invention;

Fig. 2 is the exemplary circuit structure chart of the led drive circuit that provides of second embodiment of the invention;

Fig. 3 is the exemplary circuit structure chart of the led drive circuit that provides of third embodiment of the invention.

Embodiment

In order to make the object of the invention, technical scheme and advantage clearer,, the present invention is further elaborated below in conjunction with accompanying drawing and embodiment.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.

In embodiments of the present invention; Employing comprises the led drive circuit of power factor controlling module and constant current control module; By the power factor controlling module half-sinusoid signal of telecommunication of rectifier circuit output is sampled and produced control signal and output to the constant current control module; When guaranteeing High Power Factor, the LED load is realized constant current control through the constant current control module then, and need not adopt inductive element and comprise the circuit of power factor correction of pulse modulator, and then reduced circuit cost.

Below in conjunction with specific embodiment concrete realization of the present invention is described in detail:

Embodiment one:

Fig. 1 shows the modular structure of the led drive circuit that first embodiment of the invention provides, and for the ease of explanation, only shows the part relevant with the present invention, and details are as follows:

Led drive circuit 100 is connected with rectifier circuit 200 and LED load 300, and rectifier circuit 200 is with civil power AC signal V _AcConvert half-sinusoid signal of telecommunication V to _I, the input of LED load 300 connects the output of rectifier circuit 200, and led drive circuit 100 comprises:

Power factor controlling module 101 is connected with the output of rectifier circuit 200, is used for the half-sinusoid signal of telecommunication V to rectifier circuit 200 outputs _ISample, and correspondingly generate and half-sinusoid signal of telecommunication V _ISynchronous first in-phase electric signals, or generate and half-sinusoid signal of telecommunication V simultaneously _ISynchronous second in-phase electric signals and control level signal;

Constant current control module 102; With being connected of power factor controlling module 101 and LED load 300, first in-phase electric signals that is used for being generated according to power factor controlling module 101 or second in-phase electric signals and control level signal are adjusted the operating current of LED load 300.

Led drive circuit 100 also comprises:

Power module 103 is connected with the output of rectifier circuit 200, is used to generate the direct current with fixed voltage value.

Embodiment two:

Fig. 2 shows the exemplary circuit structure of the led drive circuit that second embodiment of the invention provides, and for the ease of explanation, only shows the part relevant with the present invention, and details are as follows:

In the present embodiment, LED load 300 inner LED connected modes can be series, parallel or connection in series-parallel combination.

As one embodiment of the invention, power module 103 comprises:

N raceway groove J type FET J1, diode D1, resistance R 4 and diode D2;

The grid of N raceway groove J type FET J1 and drain electrode are connected to the output of rectifier circuit 200 altogether; The anode of diode D1 is connected with the source electrode of N raceway groove J type FET J1 and first end of resistance R 4 respectively with negative electrode; Second end of resistance R 4 is connected the plus earth of diode D2 with the negative electrode of diode D2.Wherein, the replaceable depletion type NMOS of being of N raceway groove J type FET J1 manages; In power module 103, the half-sinusoid signal of telecommunication V of rectifier bridge 200 outputs _IGet into the negative electrode of diode D2 through N raceway groove J type FET J1, diode D1, resistance R 4, then obtain the having fixed voltage value direct current of (like 5V) of the clamping action through diode D2.

As one embodiment of the invention, power factor controlling module 101 comprises resistance R 1 and resistance R 2, the output of the first termination rectifier circuit 200 of resistance R 1, and resistance R 2 is connected between second end and ground of resistance R 1.

As one embodiment of the invention, constant current control module 102 comprises:

Operational amplifier U1, NMOS pipe M1, NMOS pipe M2 and resistance R 3;

Second end of the in-phase input end of operational amplifier U1 and positive power source terminal difference connecting resistance R1 and second end of resistance R 4; The negative power end ground connection of operational amplifier U1; The grid of NMOS pipe M1 and second end of drain electrode difference connecting resistance R4 and the output of LED load 300; The drain and gate of NMOS pipe M2 is connected with the source electrode of NMOS pipe M1 and the output of operational amplifier U1 respectively; The source electrode of NMOS pipe M2 and first end of resistance R 3 are connected to the inverting input of operational amplifier U1, the second end ground connection of resistance R 3 altogether.Wherein, NMOS pipe M1 is equivalent to a variable resistor, can produce correspondent voltage above that along with the variation of the input voltage of LED load 300 and fall, and prevents to cause when input voltage is too high LED to burn out.

Below in conjunction with operation principle the led drive circuit that present embodiment provided is described further:

The civil power AC signal V that led drive circuit 100 is inserted _AcBe that frequency is the sine wave of 50Hz, expression formula is following:

V _ac=V _in?max·sinωt （1）

V _{In max}Be civil power AC signal V _AcPeak-peak, sin ω t is that frequency is the sine wave of 50Hz, and is well-known, through the half-sinusoid signal of telecommunication V that is exported after rectifier circuit 200 rectifications _IFrequency be 100Hz, i.e. V _IBe expressed as:

V _I=V _in?max|sinωt| （2）

Then by resistance R 1 and 2 couples of V of resistance R _ICarry out obtaining voltage V after the dividing potential drop _S(being the magnitude of voltage of described first in-phase electric signals of first embodiment of the invention), then V _SFor:

$V_S=\frac{V_{\mathrm{in}\max }\·\left|\sin \mathrm{\ωt}\right|\·R2}{R1+R2}---\left(3\right)$

The in-phase input end of operational amplifier U1 receives voltage V _S,,, can know the voltage V at common contact place of inverting input and the resistance R 3 of operational amplifier U1 according to the functional characteristic of operational amplifier from its output output high level driving N metal-oxide-semiconductor M2 conducting _CSFor:

V _CS=V _S （4）

Then flow through the electric current I of NMOS pipe M2 ₀For:

$I_0=\frac{V_{\mathrm{CS}}}{R3}---\left(5\right)$

Equality (3) and equality (4) substitution equality (5) can be got:

$I_0=\frac{V_{\mathrm{in}\max }\·\left|\sin \mathrm{\ωt}\right|\·R2}{(R1+R2)\·R3}---\left(6\right)$

Wherein, I ₀Be the electric current that flows through LED load 300, the operating current of LED load just 300.The electric current that branches to resistance R 1 owing to the output from rectifier circuit 200 is the microampere order electric current, for the operating current of LED load 300, can ignore, so just equal I from the electric current of rectifier circuit 200 outputs ₀, can know that by equality (6) electric current of rectifier circuit 200 outputs (promptly equals I ₀) and half-sinusoid signal of telecommunication V _IPhase place identical, so the power factor of led drive circuit 100 is high.

Because I ₀Phase place and half-sinusoid signal of telecommunication V _IPhase place identical, so I ₀Being to change with the frequency of the 100Hz cycle of carrying out, and because of human eye has visual persistence effect, can't distinguishing low-frequency electric current like this to change, is average current so human eye sees

Act on LED load 300 formed visual effects, so, through to the I in the equality (6) ₀Carry out following integral operation:

${\stackrel{\‾}{I}}_0=\frac{1}{\mathrm{\π}}{\∫}_0^{\mathrm{\π}}\frac{V_{\mathrm{in}\max }\·\left|\sin \mathrm{\ωt}\right|\·R2}{(R1+R2)\·R3}\mathrm{d\ωt}---\left(7\right)$

Obtaining average current

at last is shown below:

${\stackrel{\‾}{I}}_0=\frac{V_{\mathrm{in}\max }\·R2}{(R1+R2)\·R3}\·\frac{2}{\mathrm{\π}}---\left(8\right)$

Because V _{In max}Be constant, the resistance of resistance R 1, resistance R 2 and resistance R 3 is the fixed value that configures, and

Be constant, obviously, can know average current from equality (8)

Be constant, therefore, led drive circuit can be realized constant current output to LED load 300.

Embodiment three:

Fig. 3 shows the exemplary circuit structure of the led drive circuit that third embodiment of the invention provides, and for the ease of explanation, only shows the part relevant with the present invention, and details are as follows:

In the present embodiment, the LED in the LED load 300 is the relation of being connected in series, and wherein the output of LED lamp group 301 is the internal circuit nodes P1 of LED load 300; It is consistent that the circuit structure of power module 103 and second embodiment of the invention are provided, and therefore repeats no more.

As one embodiment of the invention, power factor controlling module 101 comprises:

Resistance R 5, resistance R 6, comparator U2, resistance R 7, comparator U3, resistance R 8, resistance R 9 and bandgap voltage reference 1011;

The output of the first termination rectifier circuit 200 of resistance R 5; Second end of resistance R 5 and first end of resistance R 6 are connected to the in-phase input end of comparator U2 altogether; The negative power end ground connection of comparator U2; Second end of resistance R 6 and first end of resistance R 7 are connected to the in-phase input end of comparator U3 altogether, the negative power end ground connection of comparator U3, and resistance R 8 is connected between second end and ground of resistance R 7; The input of the positive power source terminal of the positive power source terminal of comparator U2, comparator U3 and bandgap voltage reference 1011 is connected to second end of resistance R 4 altogether, and the inverting input of the inverting input of comparator U2 and comparator U3 is connected to the output of bandgap voltage reference 1011 altogether.Wherein, bandgap voltage reference 1011 is used to the inverting input of comparator U2 and the inverting input of comparator U3 reference voltage V is provided for reference voltage generating circuit commonly used _r

As one embodiment of the invention, constant current control module 102 comprises:

NMOS pipe M3, NMOS pipe M4, NMOS pipe M5, operational amplifier U4, NMOS pipe M6 and resistance R 9;

The drain electrode of NMOS pipe M3 and grid connect the grid of NMOS pipe M4 and the grid of NMOS pipe M5 respectively; The source ground of NMOS pipe M3; And the grid of NMOS pipe M4 is connected with the output of comparator U2 and the output of comparator U3 respectively with the grid of NMOS pipe M5; The drain electrode of NMOS pipe M4 and the drain electrode of NMOS pipe M5 are connected the internal circuit nodes P1 and the output of LED load 300 respectively, and the source electrode of NMOS pipe M4 is connected to the drain electrode that NMOS manages M6 altogether with the source electrode of NMOS pipe M5, and the grid that NMOS manages M6 connects the output of operational amplifier U4; Second end of the in-phase input end connecting resistance R7 of operational amplifier U4; The positive power source terminal of operational amplifier U4 is connected with ground with second end of resistance R 4 respectively with negative power end, and the source electrode of NMOS pipe M6 and the inverting input of operational amplifier U4 are connected to first end of resistance R 9, the second end ground connection of resistance R 9 altogether.

Below in conjunction with operation principle the led drive circuit that present embodiment provided is described further:

The operation principle of the resistance R 7 in the present embodiment, resistance R 8, operational amplifier U4, NMOS pipe M6 and resistance R 9 is identical with the operation principle that resistance R 1, resistance R 2, operational amplifier U1, NMOS in the second embodiment of the invention manages M2 and resistance R 3; Wherein, the voltage V of second end of resistance R 7 _S1(being the magnitude of voltage of described second in-phase electric signals of first embodiment of the invention) is:

$V_{S1}=\frac{V_{\mathrm{in}\max }\·\left|\sin \mathrm{\ωt}\right|\·R8}{R5+R6+R7+R8}---\left(9\right)$

The voltage V at the common contact place of the inverting input of operational amplifier U4 and resistance R 9 _CS1For:

V _CS1=V _S1 （10）

Then flow through the electric current I of NMOS pipe M6 ₁For:

$I_1=\frac{V_{\mathrm{in}\max }\·\left|\sin \mathrm{\ωt}\right|\·R8}{(R5+R6+R7+R8)\·R9}---\left(11\right)$

So, through to the I in the equality (11) ₁After carrying out integral operation and averaging, can flow through the average current of LED load 300

For:

${\stackrel{\‾}{I}}_1=\frac{V_{\mathrm{in}\max }\·R8}{(R5+R6+R7+R8)\·R9}\·\frac{2}{\mathrm{\π}}---\left(12\right)$

Can know equally that from equality (11) and equality (12) led drive circuit can be realized constant current output when guaranteeing High Power Factor.

The half-sinusoid signal of telecommunication V that is exported when rectifier circuit 200 _IWhen changing from low to high, the voltage V of the in-phase input end of comparator U2 _U2For:

$V_{U2}=V_I\·\frac{R6+R7+R8}{R5+R6+R7+R8}---\left(13\right)$

The voltage V of the in-phase input end of comparator U3 _U3For:

$V_{U3}=V_I\·\frac{R7+R8}{R5+R6+R7+R8}---\left(14\right)$

Can know from equality (13) and equality (14):

V _U2>V _U3 （15）

Work as V _U2<v _r(V then _U3Also less than V _r) time, comparator U2 and comparator U3 all can output low level (being the described control level signal of first embodiment of the invention) end NMOS pipe M4 and NMOS pipe M5, and then LED load this moment 300 no currents pass through.

Work as V _U3<v _r<v _U2The time, comparator U2 can export high level driving N metal-oxide-semiconductor M4 conducting, and the LED lamp group 301 in LED load this moment 300 has electric current I ₁Flow through and operate as normal.

Work as V _r≤V _U3The time, comparator U3 can export high level driving N metal-oxide-semiconductor M5 conducting, and comparator U2 then can output low level end NMOS pipe M4, so all LED in the LED load all have electric current I ₁Through, and get into the constant current operating state.

In the present embodiment, adopt comparator U2 and comparator U3 respectively the break-make of NMOS pipe M4 and NMOS pipe M5 to be controlled, can be at half-sinusoid signal of telecommunication V _IOnly open the partial L ED in the LED load when low, and at half-sinusoid signal of telecommunication V _IOpen more LED during rising, thereby realize and both to have reached maintenance LED load 300 and under constant current state, to have worked according to the LED of the corresponding unlatching right quantity of the variation of input voltage, can continue illumination for the user provide again.In addition; Though the LED in the LED load 300 adopts series system to connect; But this also is not used in the range of application that limits the led drive circuit that present embodiment provided; LED in the LED load 300 also can adopt parallel connection or connection in series-parallel combination connecting mode, and for the partial circuit as LED load 300, the LED in the LED lamp group 301 can adopt series, parallel or connection in series-parallel combination connecting mode equally.

Another purpose of the embodiment of the invention also is to provide a kind of LED lighting device that comprises above-mentioned led drive circuit.

In embodiments of the present invention; Employing comprises the led drive circuit of power factor controlling module and constant current control module; By the power factor controlling module half-sinusoid signal of telecommunication of rectifier circuit output is sampled and produced control signal and output to the constant current control module; When guaranteeing High Power Factor, the LED load is realized constant current control through the constant current control module then; And need not adopt inductive element and comprise the circuit of power factor correction of pulse modulator, and then reduce circuit cost, thereby solve existing in prior technology circuit structure complicacy and the high problem of cost.

The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being done, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims (7)

1. led drive circuit; Be connected with rectifier circuit and LED load, said rectifier circuit converts the civil power AC signal to the half-sinusoid signal of telecommunication, and the input of said LED load connects the output of said rectifier circuit; It is characterized in that said led drive circuit comprises:

The power factor controlling module; Be connected with the output of said rectifier circuit; Be used for the said half-sinusoid signal of telecommunication is sampled; And correspondingly generate and synchronous first in-phase electric signals of the said half-sinusoid signal of telecommunication, or generate and synchronous second in-phase electric signals of the said half-sinusoid signal of telecommunication and control level signal simultaneously;

The constant current control module is connected with said power factor controlling module and said LED load, is used for according to said first in-phase electric signals or said second in-phase electric signals and said control level signal the operating current of said LED load being adjusted.

2. led drive circuit as claimed in claim 1 is characterized in that, said led drive circuit also comprises:

Power module is connected with the output of said rectifier circuit, is used to generate the direct current with fixed voltage value;

Said power module comprises:

N raceway groove J type FET J1, diode D1, resistance R 4 and diode D2;

The grid of said N raceway groove J type FET J1 and drain electrode are connected to the output of said rectifier circuit altogether; The anode of said diode D1 is connected with the source electrode of said N raceway groove J type FET J1 and first end of said resistance R 4 respectively with negative electrode; Second end of said resistance R 4 is connected the plus earth of said diode D2 with the negative electrode of said diode D2.

3. led drive circuit as claimed in claim 2; It is characterized in that; Said power factor controlling module comprises resistance R 1 and resistance R 2, the output of the said rectifier circuit of first termination of said resistance R 1, and said resistance R 2 is connected between second end and ground of said resistance R 1.

4. led drive circuit as claimed in claim 3 is characterized in that, said constant current control module comprises:

Operational amplifier U1, NMOS pipe M1, NMOS pipe M2 and resistance R 3;

The in-phase input end of said operational amplifier U1 and positive power source terminal connect second end of said resistance R 1 and second end of said resistance R 4 respectively; The negative power end ground connection of said operational amplifier U1; The grid of said NMOS pipe M1 and second end of drain electrode difference connecting resistance R4 and the output of LED load; The drain and gate of said NMOS pipe M2 is connected with the source electrode of said NMOS pipe M1 and the output of said operational amplifier U1 respectively; The source electrode of said NMOS pipe M2 and first end of said resistance R 3 are connected to the inverting input of said operational amplifier U1, the second end ground connection of said resistance R 3 altogether.

5. led drive circuit as claimed in claim 2 is characterized in that, said power factor controlling module comprises:

Resistance R 5, resistance R 6, comparator U2, resistance R 7, comparator U3, resistance R 8, resistance R 9 and bandgap voltage reference;

The output of the said rectifier circuit of first termination of said resistance R 5; Second end of said resistance R 5 and first end of said resistance R 6 are connected to the in-phase input end of said comparator U2 altogether; The negative power end ground connection of said comparator U2; Second end of said resistance R 6 and first end of said resistance R 7 are connected to the in-phase input end of said comparator U3 altogether; The negative power end ground connection of said comparator U3; Said resistance R 8 is connected between second end and ground of said resistance R 7, and the positive power source terminal of the positive power source terminal of said comparator U2, said comparator U3 and the input of said bandgap voltage reference are connected to second end of said resistance R 4 altogether, and the inverting input of the inverting input of said comparator U2 and said comparator U3 is connected to the output of said bandgap voltage reference altogether.

6. led drive circuit as claimed in claim 5 is characterized in that, said constant current control module comprises:

NMOS pipe M3, NMOS pipe M4, NMOS pipe M5, operational amplifier U4, NMOS pipe M6 and resistance R 9;

The drain electrode of said NMOS pipe M3 and grid connect the grid of said NMOS pipe M4 and the grid of said NMOS pipe M5 respectively; The source ground of said NMOS pipe M3; And the grid of said NMOS pipe M4 is connected with the output of said comparator U2 and the output of said comparator U3 respectively with the grid of said NMOS pipe M5; The drain electrode of said NMOS pipe M4 and the drain electrode of said NMOS pipe M5 are connected the internal circuit nodes and the output of LED load respectively; The source electrode of the source electrode of said NMOS pipe M4 and said NMOS pipe M5 is connected to the drain electrode of said NMOS pipe M6 altogether; The grid of said NMOS pipe M6 connects the output of said operational amplifier U4, and the in-phase input end of said operational amplifier U4 connects second end of said resistance R 7, and the positive power source terminal of said operational amplifier U4 is connected with ground with second end of said resistance R 4 respectively with negative power end; The source electrode of said NMOS pipe M6 and the inverting input of said operational amplifier U4 are connected to first end of said resistance R 9, the second end ground connection of said resistance R 9 altogether.

7. a LED lighting device is characterized in that, said LED lighting device comprises like each described led drive circuit of claim 1 to 6.

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