CN102724797B - 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 light device

Technical field

The invention belongs to field of LED drive, particularly relate to a kind of LED drive circuit and LED light device.

Background technology

At present, LED as a kind of new type light source, due to its have that energy consumption is low, the strong and advantage that the life-span is long of brightness, be widely used in every field.The LED drive circuit for driving LED work that prior art provides mainly adopts AC-DC isolation drive mode or DC-DC non-isolated type of drive.

But, all need in the circuit structure that above-mentioned two kinds of type of drive adopt to use as the inductive element such as transformer, inductance, 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 comprising pulse-modulator, make whole circuit structure more complicated, be unfavorable for the miniaturization of LED lamp, and add circuit cost.Therefore, there is the complicated and problem that cost is high of circuit structure in prior art.

Summary of the invention

The object of the present invention is to provide a kind of LED drive circuit, under being intended to the prerequisite ensureing to realize High Power Factor and constant current output, solve the complicated and problem that cost is high of circuit structure existing for prior art.

The present invention realizes like this, a kind of LED drive circuit, be connected with rectifier circuit and LED load, described rectifier circuit converts mains signal to the half-sinusoid signal of telecommunication, the input of described LED load connects the output of described rectifier circuit, and described LED drive circuit comprises:

Power factor controlling module, be connected with the output of described rectifier circuit, for sampling to the described half-sinusoid signal of telecommunication, and correspondingly generate and synchronous first in-phase electric signals of the described half-sinusoid signal of telecommunication, or generate and synchronous second in-phase electric signals of the described half-sinusoid signal of telecommunication and control level signal simultaneously;

Constant-current control module, is connected with described power factor controlling module and described LED load, for adjusting according to described first in-phase electric signals or described second in-phase electric signals and the operating current of described control level signal to described LED load.

Another object of the present invention is also to provide a kind of LED light device comprising described LED drive circuit.

In the present invention, adopt the LED drive circuit comprising described power factor controlling module and described constant-current control module, by described power factor controlling module the half-sinusoid signal of telecommunication that described rectifier circuit exports sampled and produce control signal and output to constant-current control module, then while guarantee High Power Factor, current constant control is realized to LED load by described constant-current control module, and do not need to adopt inductive element and the circuit of power factor correction comprising pulse-modulator, and then reduce circuit cost, thus solve the complicated and problem that cost is high of circuit structure existing for prior art.

Accompanying drawing explanation

Fig. 1 is the function structure chart of the LED drive circuit that first embodiment of the invention provides;

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

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

Detailed description of the invention

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

In embodiments of the present invention, adopt the LED drive circuit comprising power factor controlling module and constant-current control module, by power factor controlling module the half-sinusoid signal of telecommunication that rectifier circuit exports sampled and produce control signal and output to constant-current control module, then while guarantee High Power Factor, current constant control is realized to LED load by constant-current control module, and do not need to adopt inductive element and the circuit of power factor correction comprising pulse-modulator, and then reduce circuit cost.

Below in conjunction with specific embodiment, specific implementation 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 convenience of explanation, illustrate only part related to the present invention, details are as follows:

LED drive circuit 100 is connected with rectifier circuit 200 and LED load 300, and rectifier circuit 200 is by mains 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, for the half-sinusoid signal of telecommunication V exported rectifier circuit 200 _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, adjust for the first in-phase electric signals of generating according to power factor controlling module 101 or the second in-phase electric signals and the operating current of control level signal to LED load 300.

LED drive circuit 100 also comprises:

Power module 103, is connected with the output of rectifier circuit 200, for generating 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 convenience of explanation, illustrate only part related to the present invention, details are as follows:

In the present embodiment, the LED connected mode of LED load 300 inside 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 R4 and diode D2;

Grid and the drain electrode of N raceway groove J type FET J1 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 the first end of resistance R4 respectively with negative electrode, second end of resistance R4 is connected with the negative electrode of diode D2, the plus earth of diode D2.Wherein, N raceway groove J type FET J1 can be replaced depletion type NMOS tube; In power module 103, the half-sinusoid signal of telecommunication V that rectifier bridge 200 exports _ienter the negative electrode of diode D2 through N raceway groove J type FET J1, diode D1, resistance R4, then obtain the direct current with fixed voltage value (as 5V) by the clamping action of diode D2.

As one embodiment of the invention, power factor controlling module 101 comprises resistance R1 and resistance R2, and the output of the first termination rectifier circuit 200 of resistance R1, resistance R2 is connected between second end of resistance R1 and ground.

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

Operational amplifier U1, NMOS tube M1, NMOS tube M2 and resistance R3;

The in-phase input end of operational amplifier U1 and positive power source terminal be second end of connecting resistance R1 and second end of resistance R4 respectively, the negative power end ground connection of operational amplifier U1, the grid of NMOS tube M1 and drain electrode be second end of connecting resistance R4 and the output of LED load 300 respectively, the drain and gate of NMOS tube M2 is connected with the source electrode of NMOS tube M1 and the output of operational amplifier U1 respectively, the source electrode of NMOS tube M2 and the first end of resistance R3 are connected to the inverting input of operational amplifier U1 altogether, the second end ground connection of resistance R3.Wherein, NMOS tube M1 is equivalent to a variable resistor, can produce corresponding voltage drop thereon, cause LED to burn out when preventing input voltage too high along with the change of the input voltage of LED load 300.

Below in conjunction with operation principle, the LED drive circuit that the present embodiment provides is described further:

The mains signal V that LED drive circuit 100 accesses _acthe sine wave of to be frequency be 50Hz, expression formula is as follows:

V _ac=V _{in max}·sinωt （1）

V _{in max}mains signal V _acpeak-peak, the sine wave of sin ω t to be frequency be 50Hz, as everyone knows, the half-sinusoid signal of telecommunication V exported after rectifier circuit 200 rectification _ifrequency be 100Hz, i.e. V _ibe expressed as:

V _I=V _{in max}|sinωt| （2）

Then by resistance R1 and resistance R2 to V _ivoltage V is obtained after carrying out dividing potential drop _s(being the magnitude of voltage of the first in-phase electric signals described in 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, export high level driving N metal-oxide-semiconductor M2 conducting from its output, according to the functional characteristic of operational amplifier, the voltage V at the inverting input of known operational amplifier U1 and the common contact place of resistance R3 _cSfor:

V _CS=V _S（4）

Then flow through the electric current I of NMOS tube M2 ₀for:

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

Equation (3) and equation (4) are substituted into equation (5) can obtain:

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

Wherein, I ₀be the electric current flowing through LED load 300, namely the operating current of LED load 300.Because the electric current branching to resistance R1 from the output of rectifier circuit 200 is microampere order electric current, negligible for the operating current of LED load 300, so just equal I from the electric current of rectifier circuit 200 output ₀, from equation (6), the electric current that rectifier circuit 200 exports (namely equals I ₀) and half-sinusoid signal of telecommunication V _iphase place identical, therefore the power factor of LED drive circuit 100 is high.

Due to I ₀phase place and half-sinusoid signal of telecommunication V _iphase place identical, so I ₀be carry out mechanical periodicity with the frequency of 100Hz, and there is visual persistence effect because of human eye, low-frequency curent change like this cannot be distinguished, so human eye institute is it is seen that average current act on the visual effect that LED load 300 is formed, so, by the I in peer-to-peer (6) ₀carry out following integral operation:

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

Finally obtain average current be shown below:

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

Due to V _{in max}be constant, the resistance of resistance R1, resistance R2 and resistance R3 is the fixed value set, and for constant, obviously, from equation (8) known average current be constant, therefore, LED drive circuit can realize constant current to LED load 300 and export.

embodiment three:

Fig. 3 shows the exemplary circuit structure of the LED drive circuit that third embodiment of the invention provides, and for convenience of explanation, illustrate only part related to the present invention, details are as follows:

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

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

Resistance R5, resistance R6, comparator U2, resistance R7, comparator U3, resistance R8, resistance R9 and bandgap voltage reference 1011;

The output of the first termination rectifier circuit 200 of resistance R5, second end of resistance R5 and the first end of resistance R6 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 R6 and the first end of resistance R7 are connected to the in-phase input end of comparator U3 altogether, the negative power end ground connection of comparator U3, resistance R8 is connected between second end of resistance R7 and ground, the positive power source terminal of comparator U2, the positive power source terminal of comparator U3 and the input of bandgap voltage reference 1011 are connected to second end of resistance R4 altogether, the inverting input of comparator U2 and the inverting input of comparator U3 are connected to the output of bandgap voltage reference 1011 altogether.Wherein, bandgap voltage reference 1011 is conventional reference voltage generating circuit, for providing reference voltage V for the inverting input of comparator U2 and the inverting input of comparator U3 _r.

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

NMOS tube M3, NMOS tube M4, NMOS tube M5, operational amplifier U4, NMOS tube M6 and resistance R9;

The drain electrode of NMOS tube M3 and grid connect the grid of NMOS tube M4 and the grid of NMOS tube M5 respectively, the source ground of NMOS tube M3, and the grid of NMOS tube M4 is connected with the output of comparator U2 and the output of comparator U3 respectively with the grid of NMOS tube M5, the drain electrode of NMOS tube M4 and the drain electrode of NMOS tube M5 are connected internal circuit nodes P1 and the output of LED load 300 respectively, the source electrode of NMOS tube M4 and the source electrode of NMOS tube M5 are connected to the drain electrode of NMOS tube M6 altogether, the grid of NMOS tube 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 R4 respectively with negative power end, the source electrode of NMOS tube M6 and the inverting input of operational amplifier U4 are connected to the first end of resistance R9 altogether, the second end ground connection of resistance R9.

Below in conjunction with operation principle, the LED drive circuit that the present embodiment provides is described further:

The operation principle of the operation principle of the resistance R7 in the present embodiment, resistance R8, operational amplifier U4, NMOS tube M6 and resistance R9 and the resistance R1 in second embodiment of the invention, resistance R2, operational amplifier U1, NMOS tube M2 and resistance R3 is identical, wherein, the voltage V of second end of resistance R7 _s1(being the magnitude of voltage of the second in-phase electric signals described in 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 inverting input of operational amplifier U4 and the common contact place of resistance R9 _cS1for:

V _CS1=V _S1（10）

Then flow through the electric current I of NMOS tube M6 ₁for:

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

So, by the I in peer-to-peer (11) ₁carry out integral operation and after averaging, the average current of LED load 300 can be flow through for:

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

From equation (11) and equation (12) equally, LED drive circuit can realize constant current output while guarantee High Power Factor.

As the half-sinusoid signal of telecommunication V that rectifier circuit 200 exports _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:

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

From equation (13) and equation (14):

V _U2>V _U3（15）

Work as V _u2<V _r(then V _u3also V is less than _r) time, comparator U2 and comparator U3 all output low level (being the control level signal described in first embodiment of the invention) can make NMOS tube M4 and NMOS tube M5 cut-off, then now LED load 300 no current passes through.

Work as V _u3<V _r<V _u2time, comparator U2 can export high level driving N metal-oxide-semiconductor M4 conducting, and the LED group 301 now in LED load 300 has electric current I ₁flow through and normally work.

Work as V _r≤ V _u3time, comparator U3 can export high level driving N metal-oxide-semiconductor M5 conducting, and comparator U2 then can output low level make NMOS tube M4 end, so all LED in LED load all have electric current I ₁pass through, and enter constant current duty.

In the present embodiment, comparator U2 and comparator U3 is adopted to control the break-make of NMOS tube M4 and NMOS tube M5 respectively, can at half-sinusoid signal of telecommunication V _ithe part LED in LED load is only opened time lower, and at half-sinusoid signal of telecommunication V _iopen more LED during rising, thus realize according to the LED of the corresponding unlatching right quantity of the change of input voltage, both to have reached and having kept LED load 300 to work under constant current state, illumination can be continued for user provides again.In addition, although the LED in LED load 300 adopts series system to connect, but this is also not used in the range of application limiting the LED drive circuit that the present embodiment provides, LED in 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 LED group 301 can adopt series, parallel or connection in series-parallel combination connecting mode equally.

Another object of the embodiment of the present invention is also to provide a kind of LED light device comprising above-mentioned LED drive circuit.

In embodiments of the present invention, adopt the LED drive circuit comprising power factor controlling module and constant-current control module, by power factor controlling module the half-sinusoid signal of telecommunication that rectifier circuit exports sampled and produce control signal and output to constant-current control module, then while guarantee High Power Factor, current constant control is realized to LED load by constant-current control module, and do not need to adopt inductive element and the circuit of power factor correction comprising pulse-modulator, and then reduce circuit cost, thus solve the complicated and problem that cost is high of circuit structure existing for prior art.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.

Claims (7)

1. a LED drive circuit, be connected with rectifier circuit and LED load, described rectifier circuit converts mains signal to the half-sinusoid signal of telecommunication, and the input of described LED load connects the output of described rectifier circuit, it is characterized in that, described LED drive circuit comprises:

Power factor controlling module, be connected with the output of described rectifier circuit, for sampling to the described half-sinusoid signal of telecommunication, and correspondingly generate and synchronous first in-phase electric signals of the described half-sinusoid signal of telecommunication, or generate and synchronous second in-phase electric signals of the described half-sinusoid signal of telecommunication and control level signal simultaneously;

Constant-current control module, is connected with described power factor controlling module and described LED load, for adjusting according to described first in-phase electric signals or described second in-phase electric signals and the operating current of described control level signal to described LED load;

Described LED drive circuit also comprises:

Power module, is connected with the output of described rectifier circuit, for generating the direct current with fixed voltage value.

2. LED drive circuit as claimed in claim 1, it is characterized in that, described power module comprises:

N raceway groove J type FET J1, diode D1, resistance R4 and diode D2;

Grid and the drain electrode of described N raceway groove J type FET J1 are connected to the output of described rectifier circuit altogether, the anode of described diode D1 is connected with the described source electrode of N raceway groove J type FET J1 and the first end of described resistance R4 respectively with negative electrode, second end of described resistance R4 is connected with the negative electrode of described diode D2, the plus earth of described diode D2.

3. LED drive circuit as claimed in claim 2, it is characterized in that, described power factor controlling module comprises resistance R1 and resistance R2, and the output of rectifier circuit described in first termination of described resistance R1, between the second end that described resistance R2 is connected to described resistance R1 and ground.

4. LED drive circuit as claimed in claim 3, it is characterized in that, described constant-current control module comprises:

Operational amplifier U1, NMOS tube M1, NMOS tube M2 and resistance R3;

The in-phase input end of described operational amplifier U1 and positive power source terminal connect second end of described resistance R1 and second end of described resistance R4 respectively, the negative power end ground connection of described operational amplifier U1, the grid of described NMOS tube M1 and drain electrode be second end of connecting resistance R4 and the output of LED load respectively, the drain and gate of described NMOS tube M2 is connected with the source electrode of described NMOS tube M1 and the output of described operational amplifier U1 respectively, the source electrode of described NMOS tube M2 and the first end of described resistance R3 are connected to the inverting input of described operational amplifier U1 altogether, the second end ground connection of described resistance R3.

5. LED drive circuit as claimed in claim 2, it is characterized in that, described power factor controlling module comprises:

Resistance R5, resistance R6, comparator U2, resistance R7, comparator U3, resistance R8, resistance R9 and bandgap voltage reference;

The output of rectifier circuit described in first termination of described resistance R5, second end of described resistance R5 and the first end of described resistance R6 are connected to the in-phase input end of described comparator U2 altogether, the negative power end ground connection of described comparator U2, second end of described resistance R6 and the first end of described resistance R7 are connected to the in-phase input end of described comparator U3 altogether, the negative power end ground connection of described comparator U3, between the second end that described resistance R8 is connected to described resistance R7 and ground, the positive power source terminal of described comparator U2, the positive power source terminal of described comparator U3 and the input of described bandgap voltage reference are connected to second end of described resistance R4 altogether, the inverting input of described comparator U2 and the inverting input of described comparator U3 are connected to the output of described bandgap voltage reference altogether.

6. LED drive circuit as claimed in claim 5, it is characterized in that, described constant-current control module comprises:

NMOS tube M3, NMOS tube M4, NMOS tube M5, operational amplifier U4, NMOS tube M6 and resistance R9;

The drain electrode of described NMOS tube M3 and grid connect the grid of described NMOS tube M4 and the grid of described NMOS tube M5 respectively, the source ground of described NMOS tube M3, and the grid of described NMOS tube M4 is connected with the output of described comparator U2 and the output of described comparator U3 respectively with the grid of described NMOS tube M5, the drain electrode of described NMOS tube M4 is connected internal circuit nodes and the output of LED load respectively with the drain electrode of described NMOS tube M5, the source electrode of described NMOS tube M4 and the source electrode of described NMOS tube M5 are connected to the drain electrode of described NMOS tube M6 altogether, the grid of described NMOS tube M6 connects the output of described operational amplifier U4, the in-phase input end of described operational amplifier U4 connects second end of described resistance R7, the positive power source terminal of described operational amplifier U4 is connected with ground with second end of described resistance R4 respectively with negative power end, the source electrode of described NMOS tube M6 and the inverting input of described operational amplifier U4 are connected to the first end of described resistance R9 altogether, the second end ground connection of described resistance R9.

7. a LED light device, is characterized in that, described LED light device comprises the LED drive circuit as described in any one of claim 1 to 6.