LED drive circuit capable of gradually brightening

Abstract

The invention provides an LED drive circuit capable of gradually brightening. The LED drive circuit comprises a main control chip, a switch tube, a first power resistor R15, a second power resistor R16 and a charging capacitor C2. The capacitor C2 is connected between the control electrode of the switch tube Q1 and the GND; the switching tube Q1 and the first power resistor R15 are connected between the REXT2 pin of the main control chip and the GND, and the second power resistor R16 is connected between the REXT1 pin of the main control chip and the GND; the capacitor C2 slows the conduction time of the switch tube Q1 through charging, and when the switch tube Q1 is cut off, the power of the driving circuit is controlled by a second power resistor R16; when the switch tube Q1 enters the amplification area, the power of the drive circuit is controlled by the first power resistor R15 and the second power resistor R16 together.

Description

Technical Field

[0001] The present invention relates to a lighting device, and more particularly to an LED driving circuit capable of gradually increasing brightness. Background Art

[0002] Most of the existing products in the market are of the immediate lighting type. Even relevant standards require that the time from turning on the light to full brightness must be small enough. Therefore, the industry pursues immediate lighting and instant lighting. There are also very few slow-bright LED circuits built with an MCU, but the cost is too high and it is not very suitable for product popularization. Summary of the Invention

[0003] The main technical problem to be solved by the present invention is to provide an LED driving circuit capable of gradually increasing brightness. When the light is turned on, the light gradually transitions from low brightness to full brightness, allowing the human eye to have an adaptation process and avoiding the sudden appearance of full brightness, which instantaneously stimulates the discomfort of the eyes and makes the product more user-friendly.

[0004] To solve the above technical problems, the present invention provides an LED driving circuit capable of gradually increasing brightness, including a main control chip, a switching transistor, a first power resistor R15, a second power resistor R16, and a charging capacitor C2;

[0005] The capacitor C2 is connected between the control electrode of the switching transistor Q1 and GND; the switching transistor Q1 and the first power resistor R15 are connected between the REXT2 pin of the main control chip and GND, and the second power resistor R16 is connected between the REXT1 pin of the main control chip and GND;

[0006] The capacitor C2 slows down the conduction time of the switching transistor Q1 through charging. When the switching transistor Q1 is cut off, the power of the driving circuit is controlled by the second power resistor R16; when the switching transistor Q1 enters the amplification region, the power of the driving circuit is jointly controlled by the first power resistor R15 and the second power resistor R16.

[0007] In a preferred embodiment: it further includes a resistor R4 and a voltage stabilizing diode D3, and the resistor R4 and the voltage stabilizing diode D3 are connected in series between the positive DC output of the rectifier bridge and GND.

[0008] In a preferred embodiment: a diode D4 is connected between the control electrode of the switching transistor Q1 and the charging capacitor C2.

[0009] In a preferred embodiment: the charging capacitor C2 is connected in parallel with a resistor R21.

[0010] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0011] The present invention provides an LED driving circuit that can gradually brighten. A gradually brightening LED driving circuit is formed by simple discrete components, with a simple principle, easy to implement functions, and low cost, which is more suitable for the large-scale popularization of bulb-like and other lighting products. Due to fewer components, it is also very suitable for the DOB direction of the current power supply of the bulb lamp. Brief Description of the Drawings

[0012] Figure 1 It is a circuit diagram of a preferred embodiment of the present invention. Detailed Embodiment

[0013] In order to make the technical solutions and features of the present invention clearer, the following further describes the present invention in detail with reference to the drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, those skilled in the art's various equivalent modifications of the present invention fall within the scope defined by the appended claims of this application.

[0014] Embodiment 1

[0015] Reference Figure 1 , this embodiment provides an LED driving circuit that can gradually brighten, including a main control chip, a switching transistor, a first power resistor R15, a second power resistor R16, and a charging capacitor C2;

[0016] The capacitor C2 is connected between the control electrode of the switching transistor Q1 and GND; the switching transistor Q1 and the first power resistor R are connected between the REXT2 pin of the main control chip and GND, and the second power resistor R16 is connected between the REXT1 pin of the main control chip and GND;

[0017] The capacitor C2 slows down the conduction time of the switching transistor Q1 through charging. Specifically, when the lamp is powered on, the charging capacitor C2 needs to be charged. At this time, the voltage of the control electrode of the switching transistor Q1 is low, and the switching transistor Q1 is cut off and does not conduct. The power of the driving circuit is only controlled by the second power resistor R16, and the driving circuit operates at a relatively small power P1, and the brightness of the lamp is also relatively low. [[ID=[]27]]

[0018] A resistor R4 and a voltage stabilizing diode D3 are also connected in series between the DC output positive pole of the rectifier bridge and GND, and the charging capacitor C2 is connected in parallel with the resistor R21. Thus, a regulated power supply is established. A resistor R20 is also connected between the voltage stabilizing diode D3 and the control electrode of the switching transistor Q1. The charging capacitor C2 is slowly charged through the resistor R20. When the control electrode voltage of the switching transistor Q1 rises from 0 to 1.4V, the switching transistor Q1 starts to enter the amplification region from the cut-off state. After the switching transistor Q1 is turned on, the first power resistor R15 and the second power resistor R16 are connected in parallel to jointly control the lamp power. As the control electrode voltage of the switching transistor Q1 slowly charges from 1.4V to 2.5V, the switching transistor Q1 gradually changes from the amplification region to the conduction region, acting as a variable resistor in the circuit, so that the overall lamp power slowly changes from the lower power W1 to the maximum power P2, and the brightness also slowly changes from low brightness to maximum brightness. In this way, when the switching transistor Q1 is cut off, the power of the drive circuit is controlled by the second power resistor R16; when the switching transistor Q1 enters the amplification region, the power of the drive circuit is jointly controlled by the first power resistor R15 and the second power resistor R16.

[0019] In this embodiment, a diode D4 is connected between the control electrode of the switching transistor Q1 and the charging capacitor C2. In the circuit, the diode D4 reduces the waiting time during the 0 - 1.4V charging process. When the charging voltage of the charging capacitor C2 is 0V, the control electrode voltage Vgs of the switching transistor Q1 is already 0V + the junction voltage Vf of the diode D4. Through the diode D4, the slow change of the control electrode voltage of Q1 from (0 + Vf) or (0 + 2*Vf) to 2.5V can be adjusted. 2*Vf means connecting two diodes in series, thus saving the waiting time of the lamp at the power W1, enabling the overall lamp to reach the power-on power W1 and immediately enter the power climbing stage. After a period of time, the overall lamp reaches the maximum power W2.

[0020] The above is only a specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantive modification made to the present invention using this concept falls within the scope of infringement of the protection of the present invention.

Claims

1. An LED driving circuit capable of gradually increasing brightness, characterized in that: It includes a main control chip, a switching transistor, a first power resistor R15, a second power resistor R16, and a charging capacitor C2; The capacitor C2 is connected between the control electrode of the switching transistor Q1 and GND; the switching transistor Q1 and the first power resistor R15 are connected between the REXT2 pin of the main control chip and GND, and the second power resistor R16 is connected between the REXT1 pin of the main control chip and GND; The capacitor C2 slows down the conduction time of the switching transistor Q1 through charging. When the switching transistor Q1 is cut off, the power of the drive circuit is controlled by the second power resistor R16; when the switching transistor Q1 enters the amplification region, the power of the drive circuit is jointly controlled by the first power resistor R15 and the second power resistor R16.

2. The LED driving circuit capable of gradually increasing brightness according to claim 1, wherein: It also includes a resistor R4 and a voltage stabilizing diode D3, and the resistor R4 and the voltage stabilizing diode D3 are connected in series between the positive pole of the DC output of the rectifier bridge and GND.

3. The LED driving circuit capable of gradually brightening according to claim 1, wherein: A diode D4 is connected between the control electrode of the switching transistor Q1 and the charging capacitor C2.

4. The LED driving circuit capable of gradually brightening according to claim 1, wherein: The charging capacitor C2 is connected in parallel with the resistor R21.

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