LED dimming application circuit of linear constant current chip

Abstract

An LED dimming application circuit of a linear constant current chip comprises a main control unit U3, one end of the main control unit U3 receives LED driving voltage, the other end of the main control unit U3 is grounded, the other end of the main control unit U3 receives dimming signals PWM, the LED dimming application circuit further comprises a switching tube Q3, the control end of the switching tube Q3 is connected with the dimming signals PWM, one end of the conduction end of the switching tube Q3 is connected with the main control unit U3, the other end of the conduction end of the switching tube Q3 is connected with the control end of a switching tube Q2, and the control end of the switching tube Q3 is connected with the LED driving voltage. One end of the conduction end of the switch tube Q2 is grounded, the other end of the conduction end of the switch tube Q2 is connected with the LED driving voltage and is further connected with the control end of the switch tube Q1, one end of the conduction end of the switch tube Q1 is grounded, the other end of the conduction end of the switch tube Q1 is connected with the LED driving voltage, one end of the conduction end of the switch tube Q1 is further connected with the reference end of the reference unit U2, and one end of the conduction end of the switch tube Q1 is grounded. And the anode of the light-emitting end of the optical coupler U1 is connected with the LED driving voltage, the emitting electrode of the optical coupler U1 is grounded, and the collecting electrode of the optical coupler U1 receives feedback control FB.

Description

Technical Field

[0001] The utility model relates to the field of LED power supplies, in particular to an LED dimming application circuit of a linear constant current chip. Background Art

[0002] LED dimming application technology, some occasions have relatively high requirements for color temperature during dimming or color adjustment. This requires the development of corresponding LED driver power supplies based on the color temperature properties of LED lamp beads. The currently commonly used solution is to use an AC / DC constant voltage output power supply in the first stage and a linear constant current chip for PWM dimming in the second stage. The linear constant current chip always keeps the current of the LED lamp beads unchanged during the PWM dimming process, ensuring the stability of the color temperature of the LED lamp beads while dimming. When the voltage difference between the two ends of the linear constant current chip is greater than a certain value, the current flowing through the chip is guaranteed to remain constant. However, the loss of the chip will also increase with the increase of the voltage difference, so there will be the following two problems:

[0003] 1. The output voltage of the first-stage AC / DC constant voltage output power supply has an error range. When the output voltage is at the upper limit of the error range, the loss of the linear constant current chip will increase, resulting in increased chip heating and reduced driving efficiency.

[0004] 2. The voltage of the LED lamp bead will have an error range. When the lamp bead voltage is at the lower limit of the error range, the loss of the linear constant current chip will increase, causing the chip to heat up and the driving efficiency to decrease. Utility Model Content

[0005] To solve the above problems, the present technical solution provides an LED dimming application circuit of a linear constant current chip.

[0006] To achieve the above purpose, the technical solution is as follows:

[0007] A LED dimming application circuit for a linear constant current chip includes a main control unit U3, one end of which receives an LED driving voltage, one end is grounded, and one end receives a dimming signal PWM. The main control unit U3 also includes a switch tube Q3, the control end of the switch tube Q3 is connected to the dimming signal PWM, one end of the conduction end is connected to the main control unit U3, and the other end is connected to the control end of the switch tube Q2. The conduction end of the switch tube Q2 has one end grounded and the other end connected to the LED driving voltage. The conduction end of the switch tube Q1 is also connected to the reference end of the reference unit U2, one end is grounded, and the other end is grounded to the cathode of the light-emitting end of the optocoupler U1. The anode of the light-emitting end of the optocoupler U1 is connected to the LED driving voltage. The emitter of the optocoupler U1 is grounded, and the collector receives feedback control FB.

[0008] In some embodiments, the switch tube Q1 , the switch tube Q2 , and the switch tube Q3 are other reference sources such as triodes or MOS tubes.

[0009] In some embodiments, a resistor R7 and a diode D1 are sequentially provided between the main control unit U3 and the switch tube Q3.

[0010] In some embodiments, a conduction end of the switch tube Q2 is grounded via a resistor R8 and a capacitor C2 , and the other end of the conduction end is connected to a resistor R5 .

[0011] In some embodiments, one end of the conduction end of the switch tube Q2 is grounded through the resistor R9 and the resistor R10 , and the other end of the conduction end is connected to the resistor R4 .

[0012] In some embodiments, the other end of the reference unit U2 is connected to the LED driving voltage via the capacitor C1 , the resistor R6 , and the resistor R3 in sequence.

[0013] In some embodiments, in some embodiments, the anode of the light-emitting end of the optocoupler U1 is connected to the LED driving voltage through a resistor R1, and a resistor R2 is connected between the anode and the cathode.

[0014] The beneficial effects of this application are:

[0015] This application adds a sampling circuit to keep the voltage difference between the two ends of the linear chip constant when using the linear constant current chip, thereby improving the driving efficiency and expanding the application range of the linear chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0017] Figure 1 It is a structural schematic diagram of an embodiment of the present utility model. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] Please refer to Figure 1As shown, a LED dimming application circuit of a linear constant current chip includes a main control unit U3, one end of the main control unit U3 receives the LED driving voltage, one end is grounded, and one end receives the dimming signal PWM, and also includes a switch tube Q3, the control end of the switch tube Q3 is connected to the dimming signal PWM, one end of the conduction end is connected to the main control unit U3, and the other end is connected to the control end of the switch tube Q2, one end of the conduction end of the switch tube Q2 is grounded, and the other end is connected to the LED driving voltage, and the end is also connected to the control end of the switch tube Q1, one end of the conduction end of the switch tube Q1 is grounded, and the other end is connected to the LED driving voltage, one end of the conduction end of the switch tube Q1 is also connected to the reference end of the reference unit U2, one end is grounded, and the other end is grounded to the cathode of the light-emitting end of the optocoupler U1, the anode of the light-emitting end of the optocoupler U1 is connected to the LED driving voltage, the emitter of the optocoupler U1 is grounded, and the collector receives feedback control FB.

[0020] Preferably, the main control unit U2 is a linear constant current chip.

[0021] In this embodiment, the switch tube Q1 , the switch tube Q2 , and the switch tube Q3 are triodes or MOS tubes.

[0022] In this embodiment, a resistor R7 and a diode D1 are sequentially provided between the main control unit U3 and the switch tube Q3. Preferably, the switch tubes Q1 and Q2 are triodes, and Q3 is a MOS tube.

[0023] In this embodiment, a conducting end of the switch tube Q2 is grounded via a resistor R8 and a capacitor C2 , and the other end of the conducting end is connected to a resistor R5 .

[0024] In this embodiment, one end of the conduction end of the switch tube Q2 is grounded via the resistor R9 and the resistor R10 , and the other end of the conduction end is connected to the resistor R4 .

[0025] In this embodiment, the other end of the reference unit U2 is connected to the LED driving voltage via the capacitor C1 , the resistor R6 , and the resistor R3 in sequence.

[0026] In this embodiment, in some embodiments, the anode of the light-emitting end of the optocoupler U1 is connected to the LED driving voltage through a resistor R1 , and a resistor R2 is connected between the anode and the cathode.

[0027] LED+ is the positive terminal voltage of the LED lamp bead. When the linear chip is turned on, the voltage of LED- to ground is the conductive voltage of the chip; LED- is the negative terminal voltage of the LED lamp bead. LED- is connected to pin 1 of Q2 (point A) through R7, D1, Q3, R8 and C2. Point A is the sampling reference point of LED-; Q2 is connected to pin 1 of U2 (point B) through R5, Q1, R4, R10 and R9. Point B is the sampling reference point of LED+ and serves as the sampling voltage reference of LED-; U2 is connected to U1 through R3, R6, R1, R2 and C1. The FB signal of U1 is connected to the AC / DC The feedback control pin of the power supply can adjust the voltage of LED+ to increase or decrease; PWM is the dimming control signal. When PWM is high, the linear chip U3 is turned on, and current flows through the LED lamp bead. At the same time, Q3 is controlled to be turned on and the voltage value of LED-end is sampled. Because the reference voltage at point A always remains unchanged, when the sampled value of the LED-end voltage is higher or lower than the voltage value at point A, a feedback signal will eventually be generated at point FB to the AC / DC control chip. The control chip adjusts the voltage of LED+ end according to this signal, so that the voltage of LED-end (both ends of U3) remains constant.

[0028] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other embodiments whose principles and basic structures are the same or similar to those of the present application are within the scope of protection of the present application.

Claims

1. A linear constant current chip LED dimming application circuit, characterized in that: It includes a main control unit U3, one end of which receives the LED driving voltage, one end is grounded, and one end receives the dimming signal PWM. It also includes a switch tube Q3, the control end of the switch tube Q3 is connected to the dimming signal PWM, one end of the conduction end is connected to the main control unit U3, and the other end is connected to the control end of the switch tube Q2. One end of the conduction end of the switch tube Q2 is grounded, and the other end is connected to the LED driving voltage. This end is also connected to the control end of the switch tube Q1. One end of the conduction end of the switch tube Q1 is grounded, and the other end is connected to the LED driving voltage. One end of the conduction end of the switch tube Q1 is also connected to the reference end of the reference unit U2, one end is grounded, and the other end is grounded to the cathode of the light-emitting end of the optocoupler U1. The anode of the light-emitting end of the optocoupler U1 is connected to the LED driving voltage. The emitter of the optocoupler U1 is grounded, and the collector receives feedback control FB.

2. The LED dimming application circuit of the linear constant current chip according to claim 1, characterized in that: The switch tube Q1 , the switch tube Q2 and the switch tube Q3 are triodes or MOS tubes.

3. The LED dimming application circuit of the linear constant current chip according to claim 2, characterized in that: A resistor R7 and a diode D1 are sequentially provided between the main control unit U3 and the switch tube Q3.

4. The LED dimming application circuit of the linear constant current chip according to claim 1, characterized in that: The conducting end of the switch tube Q2 is grounded through the resistor R8 and the capacitor C2, and the other end of the conducting end is connected to the resistor R5.

5. The LED dimming application circuit of the linear constant current chip according to claim 1, characterized in that: One end of the conducting end of the switch tube Q2 is grounded through the resistor R9 and the resistor R10 , and the other end of the conducting end is connected to the resistor R4 .

6. The LED dimming application circuit of the linear constant current chip according to claim 1, characterized in that: The other end of the reference unit U2 is connected to the LED driving voltage via the capacitor C1 , the resistor R6 , and the resistor R3 in sequence.

7. The LED dimming application circuit of the linear constant current chip according to claim 1, wherein The characteristic is that: the anode of the light-emitting end of the optical coupler U1 is connected to the LED driving voltage through the resistor R1, A resistor R2 is connected between the anode and the cathode.

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