LED dimming circuit capable of adjusting two kinds of brightness

Abstract

The utility model relates to an LED dimming circuit capable of adjusting two kinds of brightness. The device comprises a master control circuit and a sampling unit. The main control circuit comprises a control chip U1, a current input control unit and an LED lamp group unit, the current input control unit is respectively connected with the control chip U1 and the sampling unit, and the sampling unit and the LED lamp group unit are respectively connected with the control chip U1; the current input control unit comprises an input interface P1 with an STOP signal input pin and a TAIL signal input pin. According to the utility model, while brightness switching is realized through the sampling unit, the types of components are reduced, the circuit structure is optimized, the area of a PCB (Printed Circuit Board) can be reduced, the product cost is greatly reduced, and the application is wider.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of car light circuit, in particular to a kind of LED dimming circuit with adjustable two luminances. BACKGROUND

[0002] The rapid development of automobile industry drives the development of automobile parts, and the car light, as an important component of automobile, provides lighting for automobile and ensures the safety of automobile driving. With the improvement of people's living standards and the increasingly fierce market competition, safety, comfort and appearance are no longer the only factors considered by consumers. On this basis, consumers hope to purchase products with high cost performance. Therefore, to improve the competitiveness of enterprises, reducing cost has become the trend of product development for main machine factory and parts factory. With the continuous progress of technology, the advantages of LED are increasingly prominent, and the market share of LED module is also expanding. For high-low light functions such as tail light and high brake light, as well as daytime running light and position light, different functions of the module will choose to share parts such as LED, drive chip, etc., and the implementation method is to adjust the current flowing into the LED to achieve different brightness.

[0003] At present, the main dimming method is PWM dimming, which usually introduces PWM signal into the EN / PWM of the chip, adjusts the opening and closing of the chip / PWM channel by controlling the pulse width, so as to adjust the LED current to achieve the purpose of dimming. There are generally two methods to achieve this:

[0004] 1. The circuit uses MCU to realize the output of PWM waveform through software programming, so as to control the EN pin of LED drive chip.

[0005] The disadvantages of using MCU are:

[0006] (1) For some simple function products, it not only wastes MCU resources, but also greatly increases product cost;

[0007] (2) It needs the support of software and hardware engineers and more development resources.

[0008] 2. A PWM signal generating circuit is built outside the main control circuit, such as Figure 1 , to realize the output current adjustment of the existing PWM circuit. The disadvantages of building a PWM signal generating circuit outside are:

[0009] (1) A large number of peripheral devices are needed to build PWM signal, including operational amplifier, voltage stabilizing tube, triode and a number of resistors and capacitors. This module circuit has high cost, and increases the difficulty of procurement, and the risk of material shortage in mass production delivery increases dramatically;

[0010] (2) This module circuit involves a large number of components, which inevitably requires a certain space for placement, which brings challenges to PCB LAYOUT;

[0011] (3) The more peripheral circuit devices, easy to cause greater interference, not conducive to the stability of the circuit work. SUMMARY

[0012] The utility model discloses a kind of adjustable two-brightness LED dimming circuits, which are simple in structure, use as few component types as possible to realize the switching of different functions and different brightness, reduce the area of PCB and greatly reduce the cost.

[0013] The utility model is implemented as follows: an adjustable two-brightness LED dimming circuit includes a main control circuit and a sampling unit; the main control circuit includes a control chip U1, a current input control unit and an LED lamp group unit, the current input control unit is connected with the control chip U1 and the sampling unit respectively, and the sampling unit and the LED lamp group unit are connected with the control chip U1 respectively; the current input control unit includes an input interface P1 with a STOP signal input pin and a TAIL signal input pin;

[0014] The sampling unit includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a MOS tube Q1 and a stabilizing tube Z1; one end of the second resistor R2 is connected with the STOP signal input pin of the input interface P1, and the other end of the second resistor R2 is connected with one end of the third resistor R3, the negative electrode of the stabilizing tube Z1 and the gate of the MOS tube Q1 respectively; the other end of the third resistor R3 is connected with the positive electrode of the stabilizing tube Z1 and the source of the MOS tube Q1 respectively and then grounded; the drain of the MOS tube Q1 is connected with one end of the first resistor R1, the other end of the first resistor R1 is connected with one end of the fourth resistor R4 and the control chip U1 respectively, and the other end of the fourth resistor R4 is grounded.

[0015] The control chip U1 includes a VIN pin, an EN pin, a PWM1 pin, a PWM2 pin, a PWM3 pin, a TEMP pin, an OUT1 pin, an OUT2 pin, an OUT3 pin, a VSNS3 pin, a VSNS2 pin, a VSNS1 pin and a REF pin; the current input control unit further includes a first diode D1, a second diode D2, a first capacitor C1 and a fifth resistor R5, the positive pole of the first diode D1 is connected with one end of the second resistor R2 and a STOP signal input pin of the input interface P1 respectively, the negative pole of the first diode D1 is connected with the negative pole of the second diode D2, one end of the fifth resistor R5, the EN pin of the control chip U1, one end of the first capacitor C1 and the VIN pin of the control chip U1 respectively, the other end of the first capacitor C1 is grounded, the positive pole of the second diode D2 is connected with a TAIL signal input pin of the input interface P1, and the other end of the fifth resistor R5 is connected with the PWM1 pin, the PWM2 pin and the PWM3 pin of the control chip U1 respectively.

[0016] The LED lamp group unit includes a first light emitting diode LD1, a second light emitting diode LD2 and a third light emitting diode LD3 connected in series, the negative pole of the third light emitting diode LD3 is grounded, and the positive pole of the first light emitting diode LD1 is connected with the OUT1 pin, the OUT2 pin, the OUT3 pin, the VSNS3 pin, the VSNS2 pin and the VSNS1 pin of the control chip U1 respectively.

[0017] The TEMP pin of the control chip U1 is grounded through a sixth resistor R6.

[0018] The control chip U1 is a three-channel linear LED driving chip with analog and PWM dimming.

[0019] The utility model discloses a beneficial effect is: through the sampling unit realizes the brightness switching, and the kind of component has reduced, has optimized the circuit structure, has provided the convenience for PCB LAYOUT, can reduce the PCB area simultaneously, has reduced the product cost greatly, makes the application more widely. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the circuit structure schematic diagram of prior art.

[0021] Figure 2 It is the circuit structure schematic diagram of the utility model. DETAILED DESCRIPTION

[0022] According to Figure 2The utility model discloses a kind of adjustable two luminance LED dimming circuit, including main control circuit and sampling unit;The main control circuit includes control chip U1, current input control unit and LED lamp group unit, the current input control unit is connected with the control chip U1 respectively, the sampling unit is connected with the control chip U1 respectively, the current input control unit includes the input interface P1 with the STOP signal input pin and the TAIL signal input pin.

[0023] The sampling unit includes first resistance R1, second resistance R2, third resistance R3, fourth resistance R4, MOS tube Q1 and stabilivolt Z1;One end of the second resistance R2 is connected with the STOP signal input pin of the input interface P1, the other end of the second resistance R2 is connected with the one end of the third resistance R3, the negative pole of stabilivolt Z1 and the grid of MOS tube Q1 respectively;The other end of the third resistance R3 is connected with the positive pole of stabilivolt Z1 and the source of MOS tube Q1 respectively and then grounded;The drain of the MOS tube Q1 is connected with one end of the first resistance R1, the other end of the first resistance R1 is connected with the one end of the fourth resistance R4 and control chip U1 respectively, and the other end of the fourth resistance R4 is grounded.

[0024] The control chip U1 includes VIN pin, EN pin, PWM1 pin, PWM2 pin, PWM3 pin, TEMP pin, OUT1 pin, OUT2 pin, OUT3 pin, VSNS3 pin, VSNS2 pin, VSNS1 pin and REF pin;The current input control unit further includes first diode D1, second diode D2, first capacitor C1 and fifth resistance R5, the positive pole of the first diode D1 is connected with the one end of the second resistance R2 and the STOP signal input pin of the input interface P1 respectively, the negative pole of the first diode D1 is connected with the negative pole of the second diode D2, one end of the fifth resistance R5, the EN pin of the control chip U1, one end of the first capacitor C1 and the VIN pin of control chip U1 respectively;The other end of the first capacitor C1 is grounded;The positive pole of the second diode D2 is connected with the TAIL signal input pin of the input interface P1;The other end of the fifth resistance R5 is connected with the PWM1 pin, PWM2 pin and PWM3 pin of the control chip U1 respectively.

[0025] The LED lamp unit includes a first light-emitting diode LD1, a second light-emitting diode LD2, and a third light-emitting diode LD3 connected in series. The negative terminal of the third light-emitting diode LD3 is grounded. The positive terminal of the first light-emitting diode LD1 is connected to the OUT1, OUT2, OUT3, VSNS3, VSNS2, and VSNS1 pins of the control chip U1, respectively. The TEMP pin of the control chip U1 is grounded through a sixth resistor R6.

[0026] The control chip U1 is a TPS92630 chip manufactured by TI.

[0027] In use, during the TAIL function, the input is connected to the VIN pin of the control chip U1 via the second diode D2 to supply power to the control chip U1. The second diode D2 and the fifth resistor R5 pull the levels of the PWM1, PWM2, and PWM3 pins of the control chip U1 high. At this time, PWM does not regulate the current. The current output by the control chip U1 is controlled by the fourth resistor R4 located next to the REF pin on the control chip U1 and the internal reference voltage VREF of the control chip U1. The output current of the control chip U1 is ITOTAL = ILED = 3 * VREF * K. (I) / R4, where VREF is a fixed value, K (I) It is a fixed value.

[0028] In the STOP function, the input is connected to the VIN pin of the control chip U1 via the first diode D1, supplying power to the control chip U1. The first diode D1 and the fifth resistor R5 pull the levels of the PWM1, PWM2, and PWM3 pins of the control chip U1 high. Compared to the TAIL function, the STOP function adds the sampling unit. The STOP signal turns on the MOSFET Q1 via the second resistor R2, where the turn-on condition for MOSFET Q1 is Vgs > Vgs_th, making the drain and source of MOSFET Q1 conduct. The first resistor R1 is grounded and connected in parallel with the sampling resistor R4 to configure and set the output current of the control chip U1. The Zener diode Z1 clamps the gate-source voltage of MOSFET Q1 to prevent damage from large voltage surges. The third resistor R3 pulls down the gate level of MOSFET Q1 to prevent interference signals from mistakenly turning on MOSFET Q1 when there is no STOP signal. At this time, the output current of the control chip U1 is ITOTAL = ILED = 3 * VREF * K. (I) / (R4 / / R1). Because the STOP function has an additional sampling resistor R1 compared to the TAIL function, and the parallel resistor will reduce the total resistance, the STOP current is larger than the TAIL current, which is reflected as a highlight.

[0029] The utility model discloses a sampling unit realizes the brightness switching, reduces the kind of component, optimizes the circuit structure, provides the convenience for PCB LAYOUT, can reduce the PCB area simultaneously, greatly reduces the product cost, makes the application more widely.

Claims

1. An LED dimming circuit with adjustable brightness of two levels, characterized in that: It includes master control circuit and sampling unit, the master control circuit includes control chip U1, current input control unit and LED lamp group unit, the current input control unit is connected with the control chip U1, the sampling unit respectively, the sampling unit, the LED lamp group unit is connected with the control chip U1 respectively, the current input control unit includes the input interface P1 with the STOP signal input pin and the TAIL signal input pin, The sampling unit includes first resistance R1, second resistance R2, third resistance R3, fourth resistance R4, MOS tube Q1 and stabilivolt Z1, one end of the second resistance R2 is connected with the STOP signal input pin of the input interface P1, the other end of the second resistance R2 is connected with one end of the third resistance R3, negative electrode of stabilivolt Z1 and gate of MOS tube Q1 respectively, the other end of the third resistance R3 is connected with positive electrode of stabilivolt Z1 and source of MOS tube Q1 respectively and then grounded, the drain of MOS tube Q1 is connected with one end of the first resistance R1, the other end of the first resistance R1 is connected with one end of the fourth resistance R4 and control chip U1 respectively, the other end of the fourth resistance R4 is grounded.

2. The adjustable two-brightness LED dimming circuit of claim 1, wherein: The control chip U1 includes VIN pin, EN pin, PWM1 pin, PWM2 pin, PWM3 pin, TEMP pin, OUT1 pin, OUT2 pin, OUT3 pin, VSNS3 pin, VSNS2 pin, VSNS1 pin and REF pin, the current input control unit further includes first diode D1, second diode D2, first capacitor C1 and fifth resistance R5, the positive electrode of the first diode D1 is connected with one end of the second resistance R2 and the STOP signal input pin of the input interface P1 respectively, the negative electrode of the first diode D1 is connected with the negative electrode of the second diode D2, one end of the fifth resistance R5, EN pin of the control chip U1, one end of the first capacitor C1 and VIN pin of control chip U1 respectively, the other end of the first capacitor C1 is grounded, the positive electrode of the second diode D2 is connected with the TAIL signal input pin of the input interface P1, the other end of the fifth resistance R5 is connected with PWM1 pin, PWM2 pin and PWM3 pin of the control chip U1 respectively.

3. The adjustable two-brightness LED dimming circuit of claim 1, wherein: The LED lamp group unit includes first light emitting diode LD1, second light emitting diode LD2 and third light emitting diode LD3 connected in series, the negative electrode of the third light emitting diode LD3 is grounded, the positive electrode of the first light emitting diode LD1 is connected with OUT1 pin, OUT2 pin, OUT3 pin, VSNS3 pin, VSNS2 pin and VSNS1 pin of the control chip U1 respectively.

4. The adjustable two-brightness LED dimming circuit of claim 1, wherein: TEMP pin of the control chip U1 is grounded through the sixth resistance R6.

5. The adjustable two-brightness LED dimming circuit of claim 1, wherein: The control chip U1 is three-channel linear LED driving chip with analog and PWM dimming.

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