CN101610621A

CN101610621A - Switchover type light emitting diode (LED) drive circuit

Info

Publication number: CN101610621A
Application number: CNA2008101266295A
Authority: CN
Inventors: 王派酋
Original assignee: Resude Holding Co ltd
Current assignee: Resude Holding Co ltd
Priority date: 2008-06-17
Filing date: 2008-06-17
Publication date: 2009-12-23

Abstract

The invention provides a kind of switchover type light emitting diode (LED) drive circuit, this circuit comprises pulse-width modulation generator, two or more light adjusting type constant current sources and two or more light-emitting diodes (LED); Mainly organize independently periodically pulse-width modulation signal by pulse-width modulation (PWM) generator output n, the period T and the work period d of each group pwm signal are all identical, but its segment pulse continues in time in regular turn, be d=1/n, each group pwm signal exports the light adjusting type constant current source to, with respectively output with the identical sequential of imported pwm signal decide current drives electric power to led array, two or more led array generation high frequencies are put in proper order to go out, the ignition frequency of every led array is 1/T Hz, it is n/T Hz that integral body is put the frequency of going out, light because of LED is discontinuous, therefore can improve drive current improving brightness, and produce continuity high brightness visual effect by the visual persistence effect of naked eyes.

Description

Switchover type light emitting diode (LED) drive circuit

Technical field

The present invention is particularly to drive the circuit of two or more light-emitting diodes relevant for light-emitting diode.

Background technology

In recent years, the manufacturing of light-emitting diode (LED) and application technology have significant progress, LED is with its durability and economize electrical advantage, replace conventional light source gradually, for example backlight of fluorescent lamp (FluorescentLamp), incandescent lamp bulb (Incandescent Lamp), based on halogen bulb (Halogen Bulb), traffic lights (Traffic Light) and liquid crystal panel (LCD Panel) or the like no longer exemplifies.The LED light fixture is most of recently to be developed towards the mode of forming led array, to improve its brightness.

LED is a kind of semiconductor subassembly with PN junction, when forward current (Forward Current) passes through, can emit beam; LED has a key property, and promptly its luminous intensity (Luminous Intensity) is proportional with forward current, and just forward current is bigger, and then luminous intensity is higher; But bigger forward current also can be supervened higher heat, the too high significantly shortening that most probably LED is caused nonvolatil infringement or life-span of heat.Therefore LED manufacturer all can make the mean forward current I that is applicable to continuous use to the LED of each specification of its manufacturing _Avg(Average Forward Current), and another is applicable to the peak forward current I that moment uses _Peak(Peak Pulse Forward Current), the latter must be higher than the former; When LED goes out with high frequency points, can apply higher peak forward current to produce higher instantaneous light emission intensity (Instantaneous Luminous Intensity); And when LED lights continuously, then only can apply lower mean forward current, the luminous intensity that it produced is continuous and consistent, but must be lower than above-mentioned with instantaneous light emission intensity that peak forward current was produced.

Known LED light fixture all adopts the operator scheme of lighting continuously, therefore only can apply lower mean forward current, if when needing to improve luminous intensity, only can solve to change more high-power LED, but it is unquestionable, this measure must expend suitable acquisition cost, and its heat dissipation problem also certainly will more be difficult to resolve certainly; On the other hand, the development of LED product is not stranghtforward, and its developmental restriction is all arranged each period, on market the product that meets user demand fully can not be arranged, and for example above single led being not easy on market of 10W seen at present.Therefore improve the unlikely again problems such as the caloric value increase and the lost of life that cause of its luminous intensity if can will have the LED product now, must have its demand to exist.

Summary of the invention

Originally Given this, main purpose of the present invention is to provide a kind of switchover type light emitting diode (LED) drive circuit, and this LED driving circuit can be saved and be used the more required acquisition cost of high-capacity LED, and can avoid living thereupon heat dissipation problem.

For reaching above-mentioned purpose, the invention provides a kind of switchover type light emitting diode (LED) drive circuit, this light-emitting diode has mean forward current and peak forward current, and this LED driving circuit comprises:

Pulse-width modulation generator, output n group be pulse-width modulation signal periodically independently, and n is a natural number, and n 〉=2, and should the cycle and the work period all identical, the work period is the inverse of n, and its segment pulse continues in time in regular turn;

Two or more light adjusting type constant current sources have the pulse-width modulation signal input part respectively, are connected to this pulse-width modulation generator respectively, receive this pulse-width modulation signal; This light adjusting type constant current source is exported decides that electric current is subjected to the control of this pulse-width modulation signal and interrupted synchronously, and the described output of deciding electric current is greater than described mean forward current, and is less than or equal to described peak forward current;

Two or more light-emitting diodes are connected to described light adjusting type constant current source respectively, and be subjected to that the light adjusting type constant current source exported intermittently decide current drives and point of scintillation is gone out.

As can be seen from the above technical solutions, the invention provides a kind of switchover type light emitting diode (LED) drive circuit, two or more LED or led array are applied the discontinuous current that high frequency switches, and it is put in proper order go out, and this electric current can be higher than mean forward current, even can reach the upper limit of peak forward current, whereby to improve the luminous intensity of LED, and the caloric value of unlikely increase LED can be saved and be used the more required acquisition cost of high-capacity LED, and can avoid living thereupon heat dissipation problem.

Description of drawings

Fig. 1 is the circuit block diagram of switchover type light emitting diode (LED) drive circuit of the present invention;

Fig. 2 is pulse-width modulation (PWM) signal timing diagram of switchover type light emitting diode (LED) drive circuit of the present invention.

Description of reference numerals

Pulse-width modulation generator 1

Light adjusting type constant current source 2a～2f

Led array 3a～3f

Embodiment

Human eye has the characteristic of the persistence of vision, luminous element for high frequency flicker can produce luminous illusion continuously, for example general fluorescent tube (fluorescent lamp) is if drive with the transformer type stabilizer, then must produce the flicker frequency (because of two null value exchange points being arranged in period of wave) of AC system electricity frequency twice at a string, it is the flicker frequency that the 60Hz civil power will produce 120Hz, this flicker frequency human eye is still discernable, even human eye there is adverse influence, so there is the light fixture of higher-order to adopt electronic ballast, supply frequency is converted to the high-frequency range of about 10～30kHz, makes flicker frequency be increased to 20～60kHz, this high frequency flicker has exceeded the scope that human eye can be discovered, and produce a kind of continuously luminous visual effect, in other words, for LED, its point of scintillation is gone out luminous, but for human eye, then for luminous continuously.

See also Fig. 1, it is for the circuit block diagram of switchover type light emitting diode (LED) drive circuit of the present invention, mainly by pulse-width modulation (PWM) generator 1, two or more light adjusting type constant current sources (Dimming ConstantCurrent Source) 2a～2f and two or more led array 3a～3f forms, wherein light adjusting type constant current source 2a～2f and led array 3a～3f are equal number, and be to dispose one to one, be changed to example with six assembly shown in Fig. 1, certainly also can be any amount group except that, on the other hand, this place's explanation is formed a bigger array with six led array 3a～3f, for example, if each led array 3a～3f is made up of 10 LED, then six led array 3a～3f will form a bigger array with 60 LED, certainly this single led array 3a～3f also can be made up of single LED, and Fig. 1 is an example with led array of six LED compositions.So-called in addition light adjusting type constant current source 2a～2f, refer to a kind of direct current constant current source with pwm signal input, the deciding electric current output and can be subjected to the control of pwm signal and produce sync break of this constant current source, as build up DC-DC transducer (DC/DCConverter) integrated circuit of the MBI6650 model that company (Macroblock) produced, the brightness adjustment control end of this DC-DC converter ic crus secunda (DIM, Dimming Control Terminal) promptly can be used as the pwm signal input.

The pwm signal input of this light adjusting type constant current source 2a～2f is connected to the pwm signal output of PWM generator 1 respectively, and light adjusting type constant current source 2a～2f is exported decides that electric current is subjected to the control of this pwm signal and interrupted synchronously, and decide the mean forward current of the output of electric current, and be less than or equal to the peak forward current of light-emitting diode greater than light-emitting diode; This PWM generator 1 can produce the pwm signal with light adjusting type constant current source equal number, PWM generator 1 output n group is the periodicity pwm signal independently, and n is a natural number, and n 〉=2, and export this pwm signal respectively to the light adjusting type constant current source, the sequential of this pwm signal illustrates in Fig. 2; Each group pwm signal is cyclical signal, and its period T and work period d are all identical, also are that the impulse duration τ of each pwm signal is all identical.Suppose that the led array 3a～3f quantity that is driven is n, then work period d is the inverse of n, be d=1/n, and the segment pulse of this led array continues in time in regular turn, the pulse that is first pwm signal that receives of led array 1 is closely followed with the pulse of second pwm signal of led array 2 receptions, and in the time of the end-of-pulsing of first pwm signal, the pulse of second pwm signal promptly takes place, as shown in Figure 2, all the other led array 3 are equal to led array 6; Suppose impulse duration τ=1ms, and n=6, then the period T of each group pwm signal promptly equals 6ms, work period d=1/6 ≈ 16.67%.

Each group pwm signal exports corresponding light adjusting type constant current source 2a～2f to, make this light adjusting type constant current source 2a～2f export respectively with the identical sequential of input pwm signal decide current drives electric power to each led array 3a～3f, make this led array 3a～3f generation high frequency identical put in proper order and go out with Fig. 2, also be that the point of each the single led array 3a～3f frequency of going out is 1/THz, all the integral body point of the led array 3a～3f frequency of going out is n/THz, as above-mentioned illustrated numeral and in conjunction with Fig. 2, if τ=1ms, n=6, T=6ms, then the point of each the single led array 3a～3f frequency of going out is 166.7Hz, it is 1kHz that integral body is put the frequency of going out, if the impulse duration τ of each pwm signal is made as 0.1ms, the whole frequency of going out of putting promptly rises to 10kHz; Frequency will rise to 20kHz if τ=0.05ms, then whole point go out; Frequency will rise to 35kHz if τ=0.0286ms, then whole point go out.

The present invention is gone out two or more led array 3a～3f with high frequency circulation point, and apply the drive current that is higher than the specified mean forward current of LED, its instantaneous light emission intensity is increased, relend eye storage characteristic by human eye, make above-mentioned instantaneous light emission intensity form the visual effect that is equivalent to continuous luminous intensity, also promptly realize the effect that overall brightness improves.

More than explanation is the particular instantiation of preferred embodiment of the present invention only, is not in order to limiting to claim of the present invention, and other are familiar with the equivalent transformation that the people finished of this skill, all should be encompassed within claims scope.

Claims

1, a kind of switchover type light emitting diode (LED) drive circuit is characterized in that, this light-emitting diode has mean forward current and peak forward current, and this LED driving circuit comprises:

Pulse-width modulation generator, output n group be pulse-width modulation signal periodically independently, and n is a natural number, and n 〉=2, and its cycle and work period are all identical, and the work period is the inverse of n, and its segment pulse continues in time in regular turn;

2, switchover type light emitting diode (LED) drive circuit as claimed in claim 1 is characterized in that, described light-emitting diode is formed light emitting diode matrix.