The driving LED constant-current source of a kind of negative pole
Technical field
The present invention discloses a kind of constant-current source, the driving LED constant-current source of particularly a kind of negative pole.
Background technology
Along with the LED illumination is more and more in the application of people's daily life, people are also more and more deep to the research of LED driving power.The driving of LED adopts constant-current source to drive more; the driving constant-current source of present LED all is to adopt anodal the driving; promptly the positive pole of input power supply is controlled; all can be provided with protective circuit and output current sample circuit in the general constant-current supply; in the common constant-current circuit; easily because output voltage is too high, perhaps under the situation such as short circuit output, easy burn-out protective circuit and sample circuit.
Summary of the invention
At shortcomings such as the driving constant-current source easy burn-out protective circuit of the above-mentioned LED of the prior art that mentions and sample circuits; the invention provides the driving LED constant-current source of a kind of new negative pole; it is connected current sampling module on the negative pole of constant-current source output by the negative pole filtration module, thereby addresses the above problem.
The technical scheme that the present invention solves its technical problem employing is: the driving LED constant-current source of a kind of negative pole, constant-current source comprises control module, PWM switch module, current sampling module and negative pole filtration module, the input power supply is given the statements based on collusion of LED lamp through PWM module out-put supply, the break-make of control module control PWM switch module, the negative pole filtration module is connected on the negative pole of out-put supply, current sampling module is taken a sample to output current by the negative pole filtration module, and sampling result is fed back to control module.
The technical scheme that the present invention solves its technical problem employing further comprises:
Described constant-current source also comprises the VCC processing module, and the input power supply is handled the back through the VCC processing module and powered to control module.
Described PWM switch module adopts switching tube Q2.
Described negative pole filtration module comprises filter capacitor C6, power conversion inductance L 1 and sustained diode 1, filter capacitor C6 is connected across between the positive pole and negative pole of out-put supply, power conversion inductance L 1 is connected on the negative pole of out-put supply, and sustained diode 1 is connected across between the positive pole of the prime of power conversion inductance L 1 and out-put supply.
Described current sampling module adopts resistance R 6, resistance R 7 and the resistance L8 that is connected in parallel, the resistance R 6 that is connected in parallel, resistance R 7 and resistance L8 and switching tube Q2 are connected in series between the negative pole and ground of out-put supply, and the common port output current sampling of the resistance R 6 that is connected in parallel, resistance R 7 and resistance L8 and switching tube Q2 feeds back signal to control module.
Described VCC processing module comprises voltage-stabiliser tube ZD1, resistance R 2 and triode Q1, voltage-stabiliser tube ZD1 and resistance R 2 are connected in parallel between the positive pole and ground of control module power supply output, triode Q1 is connected in series on the positive pole of control module power supply output, the break-make of the common port control triode Q1 of voltage-stabiliser tube ZD1 and resistance R 2.
Described input power supply adopts transformer T1, and transformer T1 is provided with additional winding, and additional winding out-put supply is given the VCC processing module.
Described input power supply adopts the single-stage DC power supply, is in series with resistance R 1 and capacitor C 1 between the positive pole of DC power supply and the ground, and the common port out-put supply of resistance R 1 and capacitor C 1 is given the VCC processing module.
The invention has the beneficial effects as follows: circuit structure of the present invention is simple, practical, and it can good treatment high voltage constant current problem in the driving of a plurality of LED series connection.Project organization of the present invention is very ingenious, and the PWM switching tube promptly can be used as the switch of protective circuit as the PWM constant current switch again, as long as it can realize high precision constant current under the high voltage with device seldom.The present invention can be good at solving in the common constant-current circuit too high because of output voltage; easy burn-out protective circuit and this problem of sample circuit during short circuit output; and the present invention is when starting; promptly utilize pulse detection output whether short circuit or open circuit are arranged; thereby control output, when not having load, the PWM switch can not exported for a long time; lowest power consumption when guaranteeing zero load realizes secondary energy-saving.
The present invention will be further described below in conjunction with the drawings and specific embodiments.
Description of drawings
Fig. 1 is a circuit block diagram of the present invention.
Fig. 2 is the embodiment of the invention one circuit theory diagrams.
Fig. 3 is the embodiment of the invention two circuit theory diagrams.
Embodiment
Present embodiment is the preferred embodiment for the present invention, and other all its principles are identical with present embodiment or approximate with basic structure, all within protection range of the present invention.
Please referring to accompanying drawing 1, the present invention mainly comprises control module, PWM switch module, current sampling module and negative pole filtration module, the input power supply is given the statements based on collusion of LED lamp through PWM module out-put supply, the break-make of control module control PWM switch module, the negative pole filtration module is connected on the negative pole of out-put supply, current sampling module is taken a sample to output current by the negative pole filtration module, and sampling result is fed back to control module.Also comprise the VCC processing module among the present invention, the input power supply is handled the back through the VCC processing module and is powered to control module.
Please in conjunction with referring to accompanying drawing 2, the input power supply is imported by transformer T1, in the present embodiment, transformer T1 is provided with two output windings, and wherein, main output winding is exported to LED lamp string and powered, secondary output winding, or be called the additional direct out-put supply of winding to the VCC processing module, control module is powered, thereby guaranteed the stability that control module is powered.In the present embodiment, the VCC processing module comprises voltage-stabiliser tube ZD1, resistance R 2 and triode Q1, voltage-stabiliser tube ZD1 and resistance R 2 are connected in parallel between additional winding (the control module power supply output) positive pole and ground of transformer T1, triode Q1 is connected in series on the positive pole of additional winding (be control module power supply defeated) of transformer T1, the break-make of the common port control triode Q1 of voltage-stabiliser tube ZD1 and resistance R 2, be connected in series with resistance R 1 successively between the additional winding of transformer T1 and the ground, diode D2 and capacitor C 1, the common port of diode D2 and capacitor C 1 is control module power supply output, and it is powered to control module by triode Q1.In the present embodiment, the PWM switch module adopts switching tube Q2, and control module adopts power supply chip U1, the break-make of the drive end control switch pipe Q2 of power supply chip U1.In the present embodiment, current sampling module adopts resistance R 6, resistance R 7 and the resistance L8 that is connected in parallel, the negative pole filtration module comprises filter capacitor C6, power conversion inductance L 1 and sustained diode 1, filter capacitor C6 is connected across between the positive pole and negative pole of out-put supply, power conversion inductance L 1 is connected on the negative pole of out-put supply, and sustained diode 1 is connected across between the positive pole of the prime of power conversion inductance L 1 and out-put supply.Switching tube Q2 and current sampling module are connected in series between the common port and ground of power conversion inductance L 1 and sustained diode 1, the common port of switching tube Q2 and current sampling module is connected on the feedback input end of control module, and the feedback current sampling module is given control module.In the present embodiment, also cross-over connection has filter capacitor C2 between main output winding positive pole and ground.
Please in conjunction with referring to accompanying drawing 3, the basic circuit structure of present embodiment is same as the previously described embodiments, difference is, in the present embodiment, the input power supply directly adopts the DC input, be connected in series with resistance R 1 and capacitor C 1 between the positive pole of DC input and the ground, the common port of resistance R 1 and capacitor C 1 is control module power supply output, and it is powered to control module by triode Q1.
The present invention in use, DC input is through the filtering of capacitor C 2, the afterflow of diode D1, the filtering of capacitor C 6 is exported to LED lamp string and is powered after the power conversion of power conversion inductance L 1.Among the present invention, switching tube Q2 and resistance R 6, resistance R 7, resistance R 8 constant power resistance constitute the current sampling loop to ground.When switching tube Q2 conducting, the output of inductance L 1 is for negative, and input is for just, and the LED conducting is luminous; When switching tube Q2 ended, the input of inductance L 1 was for negative, and output constitutes the loop for just by sustained diode 1 and circuit.Since the storage effect of inductance L 1, the moment that switching tube Q2 ends, the negative pole or the negative voltage of LED lamp string, inductance L 1 is discharged by sustained diode 1, when the discharging current of inductance L 1 hangs down, the conducting of switching tube Q2 Be Controlled, the work of beginning second period.
The present invention utilizes the PWM switch that inductance L 1 is discharged and recharged, and makes the electric current that is added on the LED lamp string remain constant.During current sampling, the size of current the when width of control module measurement pwm pulse and positive pulse, the duty ratio of PWM is controlled in the computing of averaging again then, thereby makes the electric current of output remain on steady state.In the present embodiment, the 5th pin of control module is the pin that external dimmer is used, and can import the pwm signal of regulating duty ratio from this pin input, controls the size of output current, thereby realizes the adjustable brightness of LED.
Project organization of the present invention is very ingenious, and the PWM switching tube promptly can be used as the switch of protective circuit as the PWM constant current switch again, as long as it can realize high precision constant current under the high voltage with device seldom.The present invention can be good at solving in the common constant-current circuit too high because of output voltage; easy burn-out protective circuit and this problem of sample circuit during short circuit output; and the present invention is when starting; promptly utilize pulse detection output whether short circuit or open circuit are arranged; thereby control output, when not having load, the PWM switch can not exported for a long time; lowest power consumption when guaranteeing zero load realizes secondary energy-saving.