CN103716957A - Light emitting diode (LED) control circuit and method - Google Patents
Light emitting diode (LED) control circuit and method Download PDFInfo
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- CN103716957A CN103716957A CN201310633911.3A CN201310633911A CN103716957A CN 103716957 A CN103716957 A CN 103716957A CN 201310633911 A CN201310633911 A CN 201310633911A CN 103716957 A CN103716957 A CN 103716957A
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Abstract
The invention discloses a light emitting diode (LED) control circuit and method. The circuit comprises a control unit, triodes Q1 and Q2, resistors R2 and R3, an LED set, and a power supply. The control interface of the control unit is connected with the base electrode of the triode Q1. The emitter electrode of the triode Q1 is connected with the base electrode of the triode Q2. The base electrode of the triode Q2 is connected with one end of the resistor R2. The collector electrode of the triode Q2 is connected with the base electrode of the triode Q1. The emitter electrode of the triode Q2 is connected with one end of the resistor R3. The other end of the resistor R3 is connected with the base electrode of the triode Q1 to form a loop. The other end of the resistor R2 is connected with the emitter electrode of the triode Q2 and is grounded. The collector electrode of the triode Q1 is connected with the negative electrode of the LED set. The positive electrode of the LED set is connected with the power supply. According to the invention, the LED brightness control and the LED power supply are independent relatively, and current flowing through LEDs is kept unchanged when LED power supply voltage changes.
Description
Technical field
The present invention relates to light-emitting diode control technology field, particularly a kind of LED control circuit and method.
Background technology
LED lamp is indispensable a kind of device in modern consumption electronic product, and the outstanding role of LED product is its Presentation Function.For example, the demonstration of equipment working state (operating state of the different representatives of color is different), device power state shows etc.The use of LED is very simple, but how to guarantee in the unsettled situation of power supply, and the brightness constancy of LED is not but an easy thing.For example, what consumption electronic product generally adopted is powered battery, and along with the consumption of battery electric quantity, voltage must decline, and this will make LED brightness step-down, and the user that brightness step-down must affect product experiences.Meanwhile, for the supply power voltage of LED provides multiple choices, be how also the difficult problem of pendulum in face of technical staff.Therefore, design and a kind ofly can guarantee that LED brightness preservation in the situation that of change in voltage is constant, and make the supply power voltage of LED have the technical scheme of more selection just to seem very necessary.
Summary of the invention
In view of the above problems, the invention provides a kind of a kind of LED control circuit and method that overcomes the problems referred to above or address the above problem at least in part.
According to an aspect of the present invention, provide a kind of LED control circuit, this circuit comprises: control unit, transistor Q1, transistor Q2, resistance R 2 and resistance R 3, LED group and power supply;
The control interface of control unit is connected with the base stage of transistor Q1.
The emitter of transistor Q1 is connected with transistor Q2 base stage.
The base stage of transistor Q2 is connected with one end of resistance R 2.
The collector electrode of transistor Q2 is connected with the base stage of transistor Q1.
The emitter of transistor Q2 is connected with one end of resistance R 3.
The base stage of the other end of resistance R 3 and transistor Q1 is connected to form loop.
The emitter of the other end of resistance R 2 and transistor Q2 is connected and ground connection.
The collector electrode of transistor Q1 is connected with the negative pole of LED group.
The positive pole of LED group is connected with power supply.
In one embodiment of the invention, this circuit also comprises: the first current-limiting circuit; The control interface of control unit is connected with the base stage of transistor Q1 and one end of resistance R 3 by the first current-limiting circuit.
In one embodiment of the invention, the first current-limiting circuit is the resistance R 1 being connected between the control interface of control unit and one end of resistance R 3.
In one embodiment of the invention, to control LED group bright by export high level on control interface for control unit, controls LED group go out by output low level on control interface.
In one embodiment of the invention, control unit changes by control the brightness of LED group at control interface output pulse width modulation (PWM) ripple.
Alternatively, LED group comprises a LED or comprises the LED of a plurality of series connection or comprise the LED of a plurality of parallel connections or comprise the LED that a plurality of connection in series-parallel mix.
In one embodiment of the invention, this circuit also comprises: the second current-limiting circuit, LED group is all connected to the collector electrode of transistor Q1 by the second current-limiting circuit.
In one embodiment of the invention, the second current-limiting circuit is to be connected on the negative pole of LED group and the resistance R 4 between the collector electrode of transistor Q1.
According to another aspect of the present invention, provide a kind of LED control method, the method comprises: make the control interface of control unit be connected with the base stage of transistor Q1;
Make the emitter of described transistor Q1 be connected with transistor Q2 base stage.
Make the base stage of described transistor Q2 be connected with one end of resistance R 2.
Make the collector electrode of described transistor Q2 be connected with the base stage of transistor Q1.
Make the emitter of described transistor Q2 be connected with one end of resistance R 3.
Make the other end of described resistance R 3 and the base stage of described transistor Q1 be connected to form loop.
Make the other end of described resistance R 2 and the emitter of described transistor Q2 be connected and ground connection.
Make the collector electrode of described transistor Q1 be connected with the negative pole of LED group.
Make the positive pole of described LED group be connected with power supply.
In one embodiment of the invention, to control LED group bright by export high level on control interface for control unit, controls LED group go out by output low level on control interface.
In this LED control circuit provided by the invention and method, LED brilliance control is to realize by control unit, power supply only for LED to power supply, LED brilliance control and LED power supply are relatively independent, so the supply power voltage of LED can have multiple choices.Meanwhile, in the technical program is that control unit is controlled, and can export PWM ripple by control unit and control the brightness of LED and change.And technical scheme of the present invention can realize when LED supply power voltage changes, the electric current of the LED that makes to flow through remains unchanged, and guarantees the constant of LED brightness.With respect to other LED control circuit and method, the technical program simplicity of design, stable performance, with low cost, be applicable to various LED drive circuits.
Accompanying drawing explanation
Fig. 1 is the theory diagram of a kind of LED control circuit provided by the invention;
Fig. 2 is the circuit diagram of a kind of LED control circuit of providing of one embodiment of the invention.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.
Fig. 1 is the theory diagram of a kind of LED control circuit provided by the invention.Referring to Fig. 1, core concept of the present invention is by control unit (MCU shown in Fig. 1), specifically to control light on and off state and the brightness variation of LED group, and the power supply of LED is responsible for LED group to power, LED brilliance control and LED power supply are relatively independent, therefore, LED supply power voltage also can have multiple choices.
In one embodiment of the invention, can by MCU, specifically control the light on and off state of LED group, meanwhile, the PWM waveform that can also export by MCU in one embodiment of the invention is as required realized the control of LED group brightness.
Further, this circuit forms a closed feedback loop for adjusting the electric current of LED group by two homotype triode Q1 and Q2 and interlock circuit separately thereof, makes the electric current in LED group trend towards stablizing.
Fig. 2 is the circuit diagram of a kind of LED control circuit of providing of one embodiment of the invention.
Referring to Fig. 2, this LED control circuit in the present invention comprises: control unit, transistor Q1, transistor Q2, resistance R 1, resistance R 2, resistance R 3 and resistance R 4, LED group and power supply.In Fig. 2, do not draw control unit, but illustrated the control interface of control unit.
The control interface of control unit is connected with one end of R1; The other end of R1 is connected with the base stage of transistor Q1.
The emitter of transistor Q1 is connected with transistor Q2 base stage.
The base stage of transistor Q2 is connected with one end of resistance R 2.
The collector electrode of transistor Q2 is connected with the base stage of transistor Q1.
The emitter of transistor Q2 is connected with one end of resistance R 3.
The base stage of the other end of resistance R 3 and transistor Q1 is connected to form loop.
The emitter of the other end of resistance R 2 and transistor Q2 is connected and ground connection.
The collector electrode of transistor Q1 is connected with one end of resistance R 4; The other end of resistance R 4 is connected with the negative pole of described LED group; The positive pole of LED group is connected with power supply.
It should be noted that, in one embodiment of the invention, Q1 and Q2 are all NPN type triode, and concrete model is determined according to side circuit.LED1 is light-emitting diode, and concrete model is determined according to side circuit.The resistance of resistance R 1, resistance R 2, resistance R 3 and resistance R 4 is determined according to the parameter of each related elements in side circuit, the precision encapsulation no requirement (NR) of resistance R 1, resistance R 2, resistance R 3 and resistance R 4.
Resistance R 1 is the first current-limiting circuit; mainly in order to protect the control interface of MCU; because if the words that resistance R 2 resistances are very little; in the time of Q1 conducting; may burn control interface, so resistance R 1 not what must arrange, when the resistance of resistance R 2 and R3 is enough greatly time; can save the setting of resistance R 1, simplify circuit.Similarly, resistance R 4 is the second current-limiting circuit, is mainly used for protecting LED group, neither arrange, and when the resistance of resistance R 2 and R3 is enough greatly time, the setting that also can save resistance R 4.Specifically can arrange according to circuit and product needed.
As shown in Figure 2, in one embodiment of the invention, that control unit adopts is micro-control unit MCU.In one embodiment of the invention, LED can be a LED, also can be the LED group that a plurality of LED are in series, also can be the LED of a plurality of parallel connections, can also be the LED group that mode that a plurality of LED mix by connection in series-parallel is formed by connecting, specifically can be by circuit and product demand and design.Adopt in one embodiment of the invention a LED to carry out exemplary illustration.
In technical scheme of the present invention, MCU is controlled, can control the state of the on and off of LED group by MCU.Particularly, when needs are lighted LED1, the level that can draw high control interface by MCU is controlled the bright of LED1; When not needing to light LED1, can drag down control interface level by MCU and control going out of LED1, improved like this flexibility that LED light on and off state is adjusted.And this scheme also can realize in the time need to regulating the brightness of LED group, only need to regulate the duty ratio of the pulse width modulation (PWM) waveform that MCU exports by control interface, simple and convenient.
Further, technical scheme of the present invention can also realize under the state of lighting at LED1, makes the electric current that flows through LED1 keep constant.Particularly, referring to Fig. 2, by MCU, draw high the level of control interface and light LED1.When MCU output high level, triode Q1 and Q2 are operated in amplification region, and Q1 conducting now has electric current to flow through LED1, so LED1 is lit.When mains voltage variations, Q1 emitter voltage can change, and the change in voltage of Q1 emitter must cause the variation of Q2 operating state.The variation of Q2 operating state, can cause again the variation of the upper voltage of R3, and the variation of the upper voltage of R3 causes again the variation of Q1 operating state.So just formed a closed feedback loop, the result of this feedback loop makes the electric current on LED1 trend towards stablizing.
The above-mentioned electric current that makes to flow through LED1 keeps the specific implementation process of constant thought as follows: large if supply voltage becomes, it is large that the electric current of the LED1 that flows through becomes, and the dividing potential drop on R2 becomes large so, and it is large that the dividing potential drop on R2 becomes, and causes the electric current of Q2 base stage to become large.Because Q2 is operated in amplification region, so Q2 collector current becomes large (I
c=β * I
bβ is constant).The collector current of Q2 becomes can make the voltage decreases of Q1 base stage again greatly.Q1 base voltage diminishes and can make the collector current of Q1 diminish, and the electric current of the LED1 that flows through so will diminish.The result of this process must make the electric current on LED1 trend towards stablizing.
When supply voltage diminishes, analytic process is similar.If supply voltage diminishes, the electric current of the LED1 that flows through diminishes, and causes the electric current of Q2 base stage to diminish.Because Q2 is operated in amplification region, so Q2 collector current diminishes, the collector current of Q2 diminishes, and can make again the voltage of Q1 base stage become large, and Q1 base voltage becomes greatly can make Q1 collector current become large, and the electric current of the LED1 that flows through so will become large.The result of this process is to make the electric current on LED1 trend towards stablizing.
A kind of LED control method is also provided according to another aspect of the present invention, and the method comprises: make the control interface of described control unit be connected with the base stage of transistor Q1; Make the emitter of transistor Q1 be connected with transistor Q2 base stage.
Make the base stage of transistor Q2 be connected with one end of resistance R 2.
Make the collector electrode of transistor Q2 be connected with the base stage of transistor Q1.
Make the emitter of transistor Q2 be connected with one end of resistance R 3.
Make the other end of resistance R 3 and the base stage of transistor Q1 be connected to form loop.
Make the other end of resistance R 2 and the emitter of transistor Q2 be connected and ground connection; Make the collector electrode of transistor Q1 be connected with the negative pole of LED group.
Make the positive pole of LED group be connected with power supply.
In one embodiment of the invention, to control LED group bright by export high level on control interface for control unit, controls LED group go out by output low level on control interface.
In sum, in this LED control circuit provided by the invention and method, LED brilliance control is to realize by control unit, and LED passes through Power supply, LED brilliance control and LED power supply are relatively independent, so the supply power voltage of LED can have multiple choices.Meanwhile, in the technical program is that control unit is controlled, controls the light on and off state of LED by controlled MCU, and can export PWM ripple by control unit and control the brightness of LED and change.Further, technical scheme of the present invention is when LED supply power voltage changes, and the electric current of the LED that makes to flow through remains unchanged, and with this, realizes the constant of LED brightness.
The foregoing is only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.All any modifications of doing within the spirit and principles in the present invention, be equal to replacement, improvement etc., be all included in protection scope of the present invention.
Claims (10)
1. a LED control circuit, is characterized in that, described circuit comprises: control unit, transistor Q1, transistor Q2, resistance R 2 and resistance R 3, LED group and power supply;
The base stage of the control interface of described control unit and described transistor Q1 and one end of resistance R 3 are connected;
The emitter of described transistor Q1 is connected with described transistor Q2 base stage;
The base stage of described transistor Q2 is connected with one end of described resistance R 2;
The collector electrode of described transistor Q2 is connected with the base stage of described transistor Q1;
The emitter of described transistor Q2 is connected with one end of described resistance R 3;
The base stage of the other end of described resistance R 3 and described transistor Q1 is connected to form loop;
The emitter of the other end of described resistance R 2 and described transistor Q2 is connected and ground connection;
The collector electrode of described transistor Q1 is connected with the negative pole of described LED group;
The positive pole of described LED group is connected with described power supply.
2. circuit as claimed in claim 1, is characterized in that, described circuit further comprises: the first current-limiting circuit;
The control interface of described control unit is connected with the base stage of described transistor Q1 and one end of resistance R 3 by the first current-limiting circuit.
3. circuit as claimed in claim 2, is characterized in that, described the first current-limiting circuit is the resistance R 1 being connected between the control interface of described control unit and one end of described resistance R 3.
4. circuit as claimed in claim 1, is characterized in that, to control described LED group bright by export high level on control interface for described control unit, controls described LED group go out by output low level on control interface.
5. circuit as claimed in claim 1, is characterized in that, described control unit changes by control the brightness of described LED group at control interface output pulse width modulation (PWM) ripple.
6. the circuit as described in any one in claim 1 to 5, is characterized in that, described LED group comprises a LED or comprises the LED of a plurality of series connection or comprise the LED of a plurality of parallel connections or comprise the LED that a plurality of connection in series-parallel mix.
7. circuit as claimed in claim 6, is characterized in that, described circuit further comprises: the second current-limiting circuit;
Described LED group is connected to the collector electrode of described transistor Q1 by the second current-limiting circuit.
8. circuit as claimed in claim 7, is characterized in that, described the second current-limiting circuit is to be connected on the negative pole of described LED group and the resistance R 4 between the collector electrode of described transistor Q1.
9. a control method for LED, is characterized in that, the method comprises:
Make the control interface of control unit be connected with the base stage of transistor Q1;
Make the emitter of described transistor Q1 be connected with transistor Q2 base stage;
Make the base stage of described transistor Q2 be connected with one end of resistance R 2;
Make the collector electrode of described transistor Q2 be connected with the base stage of transistor Q1;
Make the emitter of described transistor Q2 be connected with one end of resistance R 3;
Make the other end of described resistance R 3 and the base stage of described transistor Q1 be connected to form loop;
Make the other end of described resistance R 2 and the emitter of described transistor Q2 be connected and ground connection;
Make the collector electrode of described transistor Q1 be connected with the negative pole of LED group;
Make the positive pole of described LED group be connected with power supply.
10. method as claimed in claim 9, is characterized in that,
To control LED group bright by export high level on control interface for described control unit, controls LED group go out by output low level on control interface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310633911.3A CN103716957A (en) | 2013-11-28 | 2013-11-28 | Light emitting diode (LED) control circuit and method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201310633911.3A CN103716957A (en) | 2013-11-28 | 2013-11-28 | Light emitting diode (LED) control circuit and method |
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| CN201310633911.3A Pending CN103716957A (en) | 2013-11-28 | 2013-11-28 | Light emitting diode (LED) control circuit and method |
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Cited By (3)
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| CN104349558A (en) * | 2014-11-11 | 2015-02-11 | 河南天海电器有限公司 | Driving device of automobile LED (light emitting diode) steering lamp |
| CN111098781A (en) * | 2018-10-25 | 2020-05-05 | 杭州三花研究院有限公司 | Control device and control method |
| CN112543529A (en) * | 2020-11-24 | 2021-03-23 | 广州朗国电子科技有限公司 | Control circuit of LED lamp |
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Application publication date: 20140409 |