BUS BAR CURRENT CONTROL CIRCUIT, CONSTANT-CURRENT DRIVING CONTROLLER AND LED LIGHT SOURCE

Abstract

The present invention relates to a busbar current control circuit, a constant current drive controller and an LED light source, wherein the busbar current control circuit comprises a branch resistor, a branch capacitor and a branch current source, the branch resistor and the branch capacitor are connected in parallel to form a branch, one end of the branch is connected a position between the busbar resistor and the load, and the other end is connect to the branch current source; the branch current source outputs to the branch a current of adjustable magnitude, the sum of the voltage on the busbar resistor and the voltage on the branch resistor remains constant. Wherein the branch resistor occupies a portion of the voltage of the busbar resistor so that the magnitude of the current output by the busbar changes continuously, that is, when the current flowing into the branch increases, the voltage occupied by the branch resistor increases and the voltage on the busbar resistor decreases, so as to reduce the current on the busbar. Since the branch current is smoothly adjusted by the branch current source, the regulation of the output current on the busbar is also smooth. This avoids the use of the SPWM wave or the dimming switch circuit in the prior art, and the stroboscopic phenomenon due to the discontinuity of the driving current.

Claims

1. A busbar current control circuit, characterized in that it comprises a branch resistor, a branch capacitor and a branch current source, wherein the branch resistor and the branch capacitor are connected in parallel to form a branch; one end of the branch is connected to a position between the busbar resistor and the load, and the other end is connected to the branch current source; and the branch current source outputs a current of adjustable magnitude to the branch.

2. A busbar current control circuit according to claim 1, wherein the branch capacitor is a capacitor of 0.01 to 0.22 μF, and the branch resistor is a resistor of 0.5 to 2 KΩ The branch current source is a constant current source.

3. A busbar current control circuit according to claim 2, wherein the constant current source comprises a first triode, a second triode, an equivalent voltage input source and a branch power source; the equivalent voltage input source is a variable resistor, wherein a fixed pin of the variable resistor is connected to the branch power source and the other fixed pin is connected to the base of the first triode, the moving pin of the variable resistor is connected to the base of the second triode; the base of the first triode is connected to a position between the base of the second triode and the moving pin, and the collector of the first triode is connected to its own base and its emitter is grounded; the collector of the second triode is used as the output of the constant current source and its emitter is grounded.

4. A busbar current control circuit according to claim 3, wherein the first triode may be replaced with a first diode, wherein the positive electrode of the first diode is simultaneously connected to the other fixed pin, the base of the second triode and the moving pin, the negative electrode of the first diode is grounded, and the equivalent voltage input source is the variable resistor or other variable voltage input circuit.

5. A busbar current control circuit according to claim 4, wherein it further comprises a first resistor and a second resistor, the first resistor being connected between the base of the second triode and the moving pin, one end of the second resistor being connected between the first resistor and the base of the second triode, and the other end being connected to the other fixed pin; the emitter of the second triode is grounded through a resistor.

6. A constant current drive controller using the busbar current control circuit according to claim 1, wherein it further comprises a constant current control chip, a busbar resistor, a second diode and a energy storage inductor, the constant current control chip comprises a first voltage measurement pin, a second voltage measurement pin and a switch pin; the two ends of the busbar resistor are respectively connected to a power supply and the positive terminals of the load, the negative terminal of the load is connected to one end of the energy storage inductor, the other end of the energy storage inductor is connected to the positive terminal of the second diode and the switch pin, the first voltage measurement pin is connect to a position between the busbar resistor and the power supply; one end of the branch formed by the branch resistor and the branch capacitor connected in parallel in the busbar current control circuit is connected to a position between the busbar resistor and the load, the other end of the branch is connected to the second voltage measurement pin; the sum of the voltage on the busbar resistor and voltage on branch resistor remains constant.

7. A constant current drive controller according to claim 6, wherein the first voltage measurement pin and the second voltage measurement pin are used for measuring a voltage between the busbar resistor and the branch resistor.

8. A constant current drive controller according to claim 6, wherein the constant current control chip is a switching constant current driving chip; the first voltage measurement pin is a power input terminal of the switching constant current driving chip.

9. A constant current drive controller according to claim 6, wherein the constant current control chip, the busbar resistor, the second diode and the energy storage inductor are hybridly packaged.

10. An LED light source using the constant current drive controller according to claim 6, wherein the load connected to the constant current drive controller is an LED load.

Description

DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic structural view of an LED constant current drive controller according to the present invention.

[0026] FIG. 2 is a schematic view showing an adjustment of the busbar resistor voltage V.sub.Rs of the constant current chip of the present invention

[0027] FIG. 3 is a schematic view showing the adjustment of the occupied busbar resistor voltage V.sub.Rs′ after connecting the branch of the present invention FIG. 4 is a schematic structural view of a preferred embodiment of a branch constant current source of the present invention

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention will be described with reference to the accompanying drawings.

[0029] As shown in FIG. 1, the LED constant current drive controller of the present invention mainly includes a constant current control chip 1, a busbar current control circuit, an LED load 3, a busbar resistor R.sub.s, a diode D.sub.1, an energy storage inductor L.sub.1 and a power supply VDD. As an example, the constant current control chip 1 is the switching constant current driver chip 6808. The first voltage measurement pin 11 (the power input terminal VIN), the second voltage measurement pin 12 (voltage sampling terminal CS) and the switch pin 13 (switch terminal DIM) of the constant current control chip 1 is mainly used. The output of the power supply VDD is connected to one end of the busbar resistor R.sub.s. The other end of the busbar resistor R.sub.s is connected to the positive terminal of the LED load 3. The negative terminal of the LED load 3 is connected to one end of the energy storage capacitor L.sub.1. The other end of the energy storage capacitor L.sub.1 is connected to the positive terminal of the diode D.sub.1 and the switching pin 13 of the constant current control chip 1. The negative terminal of the diode D.sub.1 are connected to a position between the busbar resistor R.sub.s and the power supply VDD.

[0030] Between the busbar resistor R.sub.s and the LED load 3, the busbar current control circuit is connected. The busbar current control circuit includes a branch formed in parallel by a branch resistor R.sub.a and a branch capacitor C.sub.1, and a branch constant current source 2 for supplying power to the branch. The one end of the branch is connected to a position between the busbar resistor R.sub.s and the LED load 3, and the other end is connected to the branch constant current source 2. The branch constant current source 2 supplies power to the branch, inputs the branch current I.sub.Ra to the branch and generates the branch resistor voltage V.sub.Ra on the branch resistor R.sub.a. The first voltage measurement pin 11 is connected to one end of the busbar resistor R.sub.s which is close to the power supply VDD. The second voltage measurement pin 12 is connected to the end of the branch which is far away from the busbar. The first voltage measurement pin 11 and the second voltage measurement pin 12 are used to measure the sum of the busbar resistor voltage V.sub.Rs′ and the branch resistor voltage V.sub.Ra after occupied. The branch capacitor C.sub.1 in the present embodiment is preferably a capacitor of 0.01 to 0.22 μF, more preferably 0.1 μF, even 0.001 μF, which may be a general high reliability ceramic capacitor. The branch resistor R.sub.a is a resistor of 0.5 to 2 KΩ, preferably 1 KΩ.

[0031] As shown in FIG. 2, when the branch constant current source 2 of the busbar current control circuit does not output the branch current I.sub.Ra to the branch where the branch resistor R.sub.a is located and the power supply VDD is newly connected to the circuit, the first voltage measurement pin 11 and the second 1 voltage measurement pin 12 detect that the busbar resistor voltage V.sub.Rs is below the minimum rated voltage V.sub.min. Then the switch pin 13 is turned on. The busbar resistor voltage V.sub.Rs, the LED load 3, the energy storage inductor L.sub.1 and the constant current control chip 1 form a loop so that the busbar resistor voltage V.sub.Rs gradually rises, and the energy storage capacitor L.sub.1 is recharged. When the first voltage measurement pin 11 and the second voltage measurement pin 12 of the constant current control chip 1 detect that the busbar resistor voltage V.sub.Rs is higher than the maximum rated voltage V.sub.max the switch pin 13 is turned off. Then the energy storage capacitor L.sub.1 is discharged. The diode D.sub.1 is ON. The busbar resistor voltage V.sub.Rs, the LED load 3, the energy storage inductor L.sub.1 and the diode D.sub.1 form a loop so that the busbar resistor voltage V.sub.Rs gradually decreased. When the first voltage measurement pin 11 and the second voltage measurement pin 12 of the constant current control chip 1 detect that the busbar resistor voltage V.sub.Rs drops to the minimum rated voltage V.sub.min, the switch pin 13 is turned on and the above steps are repeated. Through the control of the constant current control chip 1, the positive terminal current I.sub.Rs of the input LED load 3 tend to be constant, so as to achieve the purpose of LED constant current drive.

[0032] As shown in FIG. 3, when the branch constant current source 2 of the busbar current control circuit outputs branch current I.sub.Ra to the branch where the branch resistor R.sub.a is located, the branch resistor R.sub.a occupies the busbar resistor voltage V.sub.Rs over the busbar resistor R.sub.s. If the occupied busbar resistor voltage V.sub.Rs′+the branch resistor voltage V.sub.Ra=the busbar resistor voltage V.sub.Rs, the measured value between the first voltage measurement pin 11 and the second voltage measurement pin 12 of the constant current control chip 1 remains constant. When the magnitude of the branch current I.sub.Ra output from the branch constant current source 2 varies continuously, accordingly, the branch resistor voltage V.sub.Ra also varies linearly. As the branch current I.sub.Ra becomes larger and the branch resistor voltage V.sub.Ra becomes larger, the occupied busbar resistor voltage V.sub.Rs′ becomes smaller, so that the busbar current I.sub.Rs input to the positive terminal of the LED load 3 becomes smaller and the brightness of the LED becomes lower. On the contrary, when the branch current I.sub.Ra becomes smaller, so that the busbar current I.sub.Rs input to the positive terminal of the LED load 3 become larger, the brightness of the LED will become higher. Accordingly, the continuous, smooth adjustment of the brightness of the LED can be achieved by means of a simple circuit. Therefore, the adjusted maximum rated voltage V.sub.max will be reduced to V.sub.max′, the minimum rated voltage V.sub.min will be reduced to V.sub.min′.

[0033] As shown in FIG. 4, the branch constant current source 2 of the present invention is preferably a constant current source composed of a first triode 21, a second triode 22, a first resistor R.sub.1, a second resistor R.sub.2, a variable resistor R.sub.t and a branch power supply 23. Wherein a fixed pin of the variable resistor R.sub.t is connected to the branch power source 23, and the other fixed pin is connected to the base of the first triode 21, the moving pin is connected to one end of the first resistor R.sub.1; the two ends of the second resistor R.sub.2 is respectively connected to the other end of the first resistor R.sub.1 and the base of the first triode 21, and the other end of the first resistor R1 is connected to the base of the second triode 22; the collector of the first triode 21 is connected to its own base and its emitter is grounded; the collector of the second triode 22 is used as the output of the constant current source and its emitter is grounded through a resistor, which is preferably a resistor of 20 KΩ. The first resistor R1 in the present embodiment is a resistor of 300 to 600 KΩ, preferably a resistor of 400 KΩ. The second resistor R2 is a resistor of 70 to 150 KΩ, preferably a resistor of 100 KΩ.

[0034] The first triode 21 may be replaced by a diode. The positive terminal of the diode is connected to the other fixed pin of the variable resistor R.sub.1. The positive terminal of the diode is also connected to a position between the base of the second triode 22 and the variable resistor R.sub.t. The negative terminal of the diode is grounded.

[0035] It should be noted that the specific embodiments described above may enable those skilled in the art to more fully understand the invention, but not in any way limit the invention. Accordingly, although the present specification has been described in detail with reference to the accompanying drawings and examples, it will be understood by those skilled in the art that modifications may be made to the present invention or equivalents may be substituted for the purposes of the present invention. In summary, all technical solutions and modifications that do not depart from the spirit and scope of the present invention are intended to be encompassed by the scope of the invention as claimed.