A LED gradual brightening and dimming control circuit

Abstract

The utility model relates to the technical field of lamp power supply. In order to solve the technical problem that the existing LED lamp has poor delay effect, the utility model discloses an LED gradual brightening and dimming control circuit, including an LED component, a switch SW and a PNP-type transistor Q5, and a constant current driver U11 is provided. The collector of the transistor Q5 is connected to the ground by a first series voltage divider circuit, the emitter of the transistor Q5 is connected to a DC power supply V+, the middle node of the first series voltage divider circuit is connected to the enable end of the constant current driver U11, the enable end is connected to the ground through a capacitor C21, the power switch end of the constant current driver U11 is connected to the current sampling end of the constant current driver U11 through an inductor L3 and an LED component in sequence, the current sampling end is connected to the DC power supply V+ through a current detection resistor, the power input end of the constant current driver U11 is connected to the DC power supply V+, and the ground end of the constant current driver U11 is grounded. Compared with the existing circuit, the participation of the constant current driver U11 has high control accuracy, high dimming ratio, and better delay effect.

Description

Technical Field

[0001] The utility model relates to the technical field of lamp power supply, in particular to an LED gradual brightening and dimming control circuit. Background Art

[0002] Whether it is traditional lamps or LED lamps, they usually reach maximum brightness immediately after pressing the switch, and turn off immediately when the switch is turned off. There are some obvious problems with this design. First, each time the lamp is turned on, a strong current surge is generated, which will damage the lamp and shorten its life, while also reducing safety. Second, turning on the light instantly may irritate the eyes, which is not good for eye health. In addition, the instantaneous extinguishing of the lamp will make it difficult for the eyes to adapt to the sudden dark environment, and may even cause dizziness.

[0003] To solve these problems, some lamps are equipped with delay circuits to gradually turn the lamp on and off, thereby providing softer light, reducing eye stress and improving visual comfort. Figure 1 As shown in the figure, it is an LED ceiling light with a delay circuit used in automobiles. The figure is provided with an RC delay circuit, and the capacitor C23 controls the delay time. The cathode of the diode D16 is connected to the switch SW. When the switch SW is closed, the base of the transistor Q6 is at a high level, the transistor Q6 is cut off, the transistor Q7 is also cut off, and the LED ceiling light is not lit; on the contrary, the LED ceiling light is lit. Among them, due to the charging and discharging effect of the capacitor C23, the circuit has a certain delay effect. Although it can be delayed, it is found that the delay is not linear enough and the transition is not smooth enough, which generally reflects that the eyes cannot adapt to this light and dark conversion process. Utility Model Content

[0004] The utility model aims to provide an LED gradual brightening and dimming control circuit to solve the technical problem of poor time delay effect of existing LED lamps.

[0005] To achieve the above purpose, the specific technical solution of a LED gradual brightening and dimming control circuit of the utility model is as follows:

[0006] A LED gradually brightening and dimming control circuit comprises an LED component, a switch SW and a PNP-type transistor Q5, wherein the base of the transistor Q5 is connected to a second series voltage divider circuit, the two ends of the second series voltage divider circuit are respectively connected to a DC power supply V+ and one end of the switch SW, the other end of the switch SW is grounded, a constant current driver U11 is provided, the collector of the transistor Q5 is grounded by the first series voltage divider circuit, the emitter of the transistor Q5 is connected to the DC power supply V+, the middle node of the first series voltage divider circuit is connected to an enable end of the constant current driver U11, the enable end is grounded through a capacitor C21, the power switch end of the constant current driver U11 is connected to a current sampling end of the constant current driver U11 through an inductor L3 and an LED component in sequence, the current sampling end is connected to the DC power supply V+ through a current detection resistor, the power input end of the constant current driver U11 is connected to the DC power supply V+, and the ground end of the constant current driver U11 is grounded.

[0007] Through the gradual brightening and dimming control method, the current impact of the LED component when switching is reduced, thereby reducing the loss of the LED component and extending its service life.

[0008] The gradual brightening and dimming characteristics of LEDs make the changes in light softer and will not suddenly irritate the eyes, thus improving the user's comfort and helping to protect eyesight.

[0009] By controlling the LED component through the constant current driver U11, it can be ensured that the LED component always maintains a stable current when working.

[0010] Preferably, the first series voltage divider circuit includes a resistor R27 and a resistor R28, and a common node of the resistor R27 and the resistor R28 is connected to the enable terminal.

[0011] Preferably, the second series voltage divider circuit includes a resistor R29 and a resistor R30, a common node of the resistor R29 and the resistor R30 is connected to the base of the transistor Q5, the resistor R30 is connected to the switch SW, and the resistor R29 is connected to the DC power supply V+.

[0012] Furthermore, a Schottky diode Z5 is provided, the anode of the Schottky diode Z5 is connected to the power switch end, and the cathode of the Schottky diode Z5 is connected to the power input end, which can prevent damage caused by the reverse voltage of the power switch drain. When the voltage on the power switch end is reversed, the Schottky diode is turned on, and the reverse voltage is connected to the power input end, which is not affected by the reverse voltage. Removing the reverse current can provide a low-impedance path so that the reverse current can flow back to the power supply smoothly, avoiding excessive reverse current in the constant current driver U11. It can be seen that the constant current driver U11 can be effectively protected from the influence of the reverse voltage, and the stability and reliability of the circuit can be improved.

[0013] Furthermore, a diode D11 and a capacitor C22 are provided, the cathode of the diode D11 is grounded, the anode of the diode D11 is connected to the ground terminal, and both ends of the capacitor C22 are connected to the power input terminal and the ground terminal respectively.

[0014] Diode D11 can isolate the voltage fluctuation between the constant current driver U11 and the actual ground to a certain extent, reduce interference, and improve the stability and reliability of the constant current driver U11; it can limit the voltage of the constant current driver U11 to the ground, prevent overvoltage from damaging the constant current driver U11, and play a certain protective role; diode grounding can provide a certain common-mode suppression capability and reduce the circuit's sensitivity to common-mode interference; diode grounding can improve the circuit's stability, reliability and anti-interference ability to a certain extent.

[0015] The LED gradual brightening and dimming control circuit provided by the utility model has the following advantages:

[0016] By connecting a capacitor C21 to the enable terminal, the voltage of the enable terminal rises slowly during startup, so that the current of the LED component also rises slowly, thereby achieving the LED component gradually brightening, and vice versa, achieving the LED component gradually dimming.

[0017] The gradual brightening and dimming control method reduces the current impact of the LED components when they are switched on and off, thereby reducing the loss of the LED components and extending their service life; the gradual brightening and dimming characteristics of the LED make the light change softer and will not suddenly irritate the eyes, improving the user's comfort and also helping to protect eyesight; the constant current driver U11 controls the LED components to ensure that the LED components always maintain a stable current when working. Compared with the existing circuit, the participation of the constant current driver U11 has high control accuracy, high dimming ratio, large dimming range, smoother transition, and better delay effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the existing LED gradual brightening and dimming control circuit diagram;

[0019] Figure 2 This is a LED gradual brightening and dimming control circuit diagram provided by the utility model. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0021] See also Figure 2The utility model provides an LED gradual brightening and dimming control circuit, including a constant current driver U11 and a PNP transistor Q5, the collector of the transistor Q5 is grounded through a resistor R28 and a resistor R27 in sequence, the resistors R28 and R27 are grounded to form a first series voltage divider circuit, the emitter of the transistor Q5 is input with a DC power supply V+, the base of the transistor Q5 is connected to a resistor R29 and a resistor R30 respectively, the other end of the resistor R29 is input with a DC power supply, the other end of the resistor R30 is grounded through a switch SW, the resistors R29 and R30 form a second series voltage divider circuit for providing a turn-on voltage to the base of the transistor Q5.

[0022] The first end of the constant current driver U11 is the ground end, which is grounded through the diode D11. The anode of the diode D11 is connected to the first end of the constant current driver U11, and the cathode of the diode D11 is grounded; the second end of the constant current driver U11 is the power input end; the third end of the constant current driver U11 is the enable end, which is connected to the middle node of the resistor R28 and the resistor R27; the fourth end of the constant current driver U11 is the current sampling end, and the fifth end of the constant current driver U11 is the power switch end, the power switch end is connected with the inductor L3 and the LED component, the inductor L3 is connected in series with the LED component, the LED component is connected to the emitter of the transistor Q5 through the current detection resistor R31, the current detection resistor R31 is connected between the power input end and the current sampling end, and a Schottky diode Z5 is also provided, the anode of the Schottky diode Z5 is connected to the power switch end, and the cathode of the Schottky diode Z5 is connected to the power input end.

[0023] Diode D11 isolates the voltage fluctuation between the constant current driver U11 and the actual ground to a certain extent, thereby reducing interference and improving the stability and reliability of the constant current driver U11. Diode D11 limits the voltage of the constant current driver U11 to the ground, which can effectively prevent overvoltage from damaging the constant current driver U11 and play a certain protective role. In addition, connecting diode D11 to the ground also provides a certain common-mode suppression capability, reducing the circuit's sensitivity to common-mode interference, thereby further improving the circuit's stability and anti-interference ability.

[0024] The constant current driver U11, the inductor L3 and the current sensing resistor R31 form a self-oscillating continuous inductor current mode buck constant current LED controller.

[0025] When V+ is powered on, the initial current of the inductor L3 and the current-sense resistor R31 is zero, and the output current of the LED component is also zero. At this time, the current sampling terminal is at a high level, the internal power switch is turned on, and the level of the power switch terminal is low. The current flows from V+ to ground through the inductor L3, the current-sense resistor R31, the LED component, and the internal power switch. The slope of the current rise is determined by the voltage drop of V+, the inductor L3, and the LED component, and a voltage difference is generated on the current-sense resistor R31 and detected by the current sampling terminal.

[0026] The enable end of the constant current driver U11 can be connected to a DC voltage to adjust the output current of the LED component. The voltage at the middle node of the first series voltage divider circuit can enable the constant current driver U11. When the switch SW connected to the resistor R30 is turned on, the base of the transistor Q5 is at a high level and the transistor Q5 is cut off. Otherwise, the transistor Q5 is turned on. When the transistor Q5 is turned on, the middle node of the first series voltage divider circuit generates a voltage, enabling the constant current driver U11 and causing the constant current driver U11 to start working.

[0027] The resistor R27 is also connected in parallel with a capacitor C21 and a diode D12. By connecting a capacitor C21 to the enable terminal, the voltage of the enable terminal rises slowly during startup, so that the current of the LED component also rises slowly, thereby realizing that the LED component gradually lights up, and vice versa, realizing that the LED component gradually dims.

[0028] In summary, the utility model provides a LED gradual brightening and dimming control circuit, which reduces the current impact of the LED component when it is switched on and off through the gradual brightening and dimming control method, thereby reducing the loss of the LED component and extending its service life; the LED gradual brightening and dimming characteristics make the light change softer and will not suddenly irritate the eyes, improve the user's comfort, and also help protect eyesight; through the control of the LED component by the constant current driver U11, it can be ensured that the LED component always maintains a stable current when working. Compared with the existing circuit, the participation of the constant current driver U11 has high control accuracy, high dimming ratio, large dimming range, smoother transition, and better delay effect.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An LED gradual brightening and dimming control circuit, comprising an LED component, a switch SW and a PNP transistor Q5, wherein the base of the transistor Q5 is connected to a second series voltage divider circuit, the two ends of the second series voltage divider circuit are respectively connected to a DC power supply V+ and one end of the switch SW, and the other end of the switch SW is grounded, characterized in that: A constant current driver U11 is provided, the collector of the transistor Q5 is grounded in a first series voltage divider circuit, the emitter of the transistor Q5 is connected to a DC power supply V+, the middle node of the first series voltage divider circuit is connected to an enable terminal of the constant current driver U11, the enable terminal is grounded through a capacitor C21, the power switch terminal of the constant current driver U11 is connected to a current sampling terminal of the constant current driver U11 through an inductor L3 and an LED component in sequence, the current sampling terminal is connected to a DC power supply V+ through a current detection resistor, the power input terminal of the constant current driver U11 is connected to the DC power supply V+, and the ground terminal of the constant current driver U11 is grounded.

2. The LED gradual brightening and dimming control circuit according to claim 1, characterized in that: The first series voltage divider circuit includes a resistor R27 and a resistor R28, and a common node of the resistor R27 and the resistor R28 is connected to the enable terminal.

3. The LED gradual brightening and dimming control circuit according to claim 2, characterized in that: The second series voltage divider circuit includes a resistor R29 and a resistor R30, a common node of the resistor R29 and the resistor R30 is connected to the base of the transistor Q5, the resistor R30 is connected to the switch SW, and the resistor R29 is connected to the DC power supply V+.

4. The LED gradual brightening and dimming control circuit according to claim 3, characterized in that: A Schottky diode Z5 is provided, an anode of the Schottky diode Z5 is connected to the power switch end, and a cathode of the Schottky diode Z5 is connected to the power input end.

5. The LED gradual brightening and dimming control circuit according to claim 4, characterized in that: A diode D11 and a capacitor C22 are also provided. The cathode of the diode D11 is grounded, the anode of the diode D11 is connected to the ground terminal, and both ends of the capacitor C22 are connected to the power input terminal and the ground terminal respectively.

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