LED stepless dimming circuit and electronic equipment

Abstract

The utility model relates to the technical field of LED dimming, and discloses an LED stepless dimming circuit and electronic equipment, which comprise an adjustable voltage unit, an operational amplifier, a switch tube, a first resistor, an LED and a second resistor. The adjustable voltage unit is used for outputting adjustable voltage; the non-inverting input end of the operational amplifier is connected with the output end of the adjustable voltage unit so as to obtain adjustable voltage; the controlled end of the switching tube is connected with the output end of the operational amplifier; the anode of the LED is connected with the VCC through the first resistor, and the cathode of the LED is connected with the first end of the switching tube; the first end of the second resistor is respectively connected with the second end of the switching tube and the inverted input end of the operational amplifier, and the second end of the second resistor is grounded; wherein the adjustable voltage is used for controlling the switching tube to be in a linear region.

Description

Technical Field

[0001] This utility model relates to the technical field of LED dimming, and in particular to an LED stepless dimming circuit and electronic device. Background Technology

[0002] With the development of electronic technology, most electronic products now include LED lighting functionality. To meet the needs of different usage environments, stepless dimming is required to adjust the brightness of the LEDs. Conventional LED stepless dimming is achieved by adjusting the PWM duty cycle of the circuit. However, in practical applications, it has been found that using a PWM with a slow duty cycle adjustment speed results in a weak dimming effect. Using a specialized PWM chip with a fast duty cycle adjustment speed to achieve stepless dimming of LED lights significantly increases costs. Utility Model Content

[0003] The purpose of this invention is to provide an LED stepless dimming circuit and electronic device, which aims to solve the problem of a significant increase in cost caused by achieving precise LED stepless dimming in the prior art.

[0004] This invention is implemented as follows: This invention provides an LED stepless dimming circuit, comprising:

[0005] Adjustable voltage unit, the adjustable voltage unit being used to output an adjustable voltage;

[0006] An operational amplifier, wherein the non-inverting input terminal of the operational amplifier is connected to the output terminal of the adjustable voltage unit to obtain the adjustable voltage;

[0007] A switching transistor, wherein the controlled terminal of the switching transistor is connected to the output terminal of the operational amplifier;

[0008] First resistor;

[0009] The LED has its anode connected to VCC via the first resistor, and its cathode connected to the first terminal of the switching transistor.

[0010] The second resistor has its first end connected to the second end of the switching transistor and the inverting input terminal of the operational amplifier, respectively.

[0011] The adjustable voltage is used to control the switching transistor to be in the linear region.

[0012] In some embodiments, the adjustable voltage unit includes: an adjustable voltage source, a third resistor, a fourth resistor, a fifth resistor, and a first capacitor;

[0013] The adjustable voltage source is used to output an initial adjustment voltage. The output terminal of the adjustable voltage source is connected to the first terminal of the third resistor. The second terminal of the third resistor is connected to the first terminal of the fourth resistor, the first terminal of the first capacitor, and the first terminal of the fourth resistor. The second terminal of the fourth resistor and the second terminal of the first capacitor are both grounded. The second terminal of the fifth resistor is connected to the non-inverting input terminal of the operational amplifier.

[0014] In some embodiments, the LED stepless dimming circuit further includes: a sixth resistor and a seventh resistor;

[0015] The first end of the sixth resistor is connected to the output terminal of the operational amplifier, and the second end of the sixth resistor is connected to the controlled terminal of the switching transistor.

[0016] The first end of the seventh resistor is connected to the first end of the second resistor, and the second end of the seventh resistor is connected to the inverting input terminal.

[0017] This utility model also provides an electronic device, which includes an LED stepless dimming circuit as described in any one of this utility model.

[0018] This invention provides an LED stepless dimming circuit, comprising: an adjustable voltage unit, an operational amplifier, a switching transistor, a first resistor, an LED, and a second resistor. The adjustable voltage unit outputs an adjustable voltage; the non-inverting input terminal of the operational amplifier is connected to the output terminal of the adjustable voltage unit to obtain the adjustable voltage; the controlled terminal of the switching transistor is connected to the output terminal of the operational amplifier; the anode of the LED is connected to VCC through the first resistor, and the cathode of the LED is connected to the first terminal of the switching transistor; the first terminal of the second resistor is connected to the second terminal of the switching transistor and the inverting input terminal of the operational amplifier, and the second terminal of the second resistor is grounded; wherein, the adjustable voltage is used to control the switching transistor to be in the linear region, which has the following beneficial effects:

[0019] 1. The circuit does not require the use of a PWM chip, reducing component costs;

[0020] 2. After changing the adjustable voltage, the current flowing through the LED can quickly change with the adjustable voltage, so that the LED brightness changes rapidly, improving the user experience. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the first LED stepless dimming circuit provided in this embodiment of the utility model;

[0022] Figure 2 This is a circuit diagram of the second type of LED stepless dimming circuit provided in this embodiment of the present invention.

[0023] Icon labels:

[0024] 100. LED stepless dimming circuit; 11. Adjustable voltage unit; U1. Operational amplifier; VT1. Switching transistor; R1. First resistor; R2. Second resistor; R3. Third resistor; R4. Fourth resistor; R5. Fifth resistor; R6. Sixth resistor; R7. Seventh resistor; C1. First capacitor; V0. Initial voltage; V1. Adjustable voltage. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0026] The implementation of this utility model will be described in detail below with reference to specific embodiments.

[0027] Reference Figure 1 The diagram shows a preferred embodiment of the present invention.

[0028] This utility model provides a first LED stepless dimming circuit 100, including: an adjustable voltage unit 11, an operational amplifier U1, a switching transistor VT1, a first resistor R1, an LED, and a second resistor R2.

[0029] Adjustable voltage unit 11 is used to output an adjustable voltage V1. The non-inverting input terminal of operational amplifier U1 is connected to the output terminal of adjustable voltage unit 11 to obtain the adjustable voltage V1. The controlled terminal of switching transistor VT1 is connected to the output terminal of operational amplifier U1. The anode of the LED is connected to VCC through a first resistor R1, and the cathode of the LED is connected to the first terminal of switching transistor VT1. The first terminal of the second resistor R2 is connected to the second terminal of switching transistor VT1 and the inverting input terminal of operational amplifier U1, and the second terminal of the second resistor R2 is grounded. The adjustable voltage is used to control the switching transistor to be in the linear region.

[0030] By adjusting the value of the adjustable voltage unit 11 to output the adjustable voltage V1, and utilizing the comparison characteristics of operational amplifier U1, when the voltage detected at the inverting input terminal of operational amplifier U1 is less than the voltage (V1) at the non-inverting input terminal, operational amplifier U1 outputs a high level to the controlled terminal of switching transistor VT1, increasing Vgs at the controlled terminal of switching transistor VT1. Since switching transistor VT1 operates in the linear region, the increase in Vgs at the controlled terminal of switching transistor VT1 leads to improved conduction performance of switching transistor VT1 (reduced resistance), thereby increasing the current flowing through the LED. After the current increases, the voltage across the second resistor R2 will rise, thereby increasing the voltage at the inverting input terminal of operational amplifier U1. This continues until the voltage at the inverting input terminal of operational amplifier U1 is essentially the same as the voltage at the non-inverting input terminal, at which point the output voltage of operational amplifier U1 stabilizes at a specific voltage value. Therefore, by appropriately adjusting the adjustable voltage V1, the output level of the operational amplifier U1 can be adjusted, thereby adjusting the current in the switching transistor VT1, and further adjusting the current flowing through the LED, thus achieving stepless dimming.

[0031] It should be noted that the switching transistor VT1 is a MOSFET. The linear region of the switching transistor VT1 is the region in which the conduction performance of the MOSFET remains linear with the change of the gate-source Vgs under specific operating conditions. In this region, the MOSFET is similar to a resistor controlled by the gate-source Vgs. The larger Vgs is, the better its conduction performance (the smaller the resistance).

[0032] To ensure that the switching transistor VT1 is in the linear region, the adjustable voltage V1 and the second resistor R2 need to be configured. The following is an explanation through a specific embodiment. It should be noted that, depending on the different switching transistors or the number of LEDs, the adjustable voltage V1 and the second resistor R2 can be configured in various ways. The following embodiment is for illustrative purposes only and is not intended to limit the scope of protection of this application. Circuit configurations that enable the switching transistor VT1 to be in the linear region to meet the requirements of relevant parameters are all within the scope of protection of this application.

[0033] In one embodiment, VCC=5V, and the maximum current that the LED can withstand is 350mA. As a current-limiting resistor, the first resistor R1 needs to limit the current to within 350mA (since the internal resistance of the switching transistor VT1 is very small when fully turned on, and the value of R2 is also within 1Ω, it is not considered in the calculation). The resistance value of the first resistor R1 is r1=5V / 0.35A=14.28Ω, meaning r1 must not be less than 14.28Ω. Considering the factor of derating to extend the lifespan of the LED, the actual value of r1 will be greater than 14.28Ω, specifically r1=20Ω. Therefore, the actual maximum current of this circuit is: I1=5 / 20=0.25A. The resistance value of R2 is in the range of 0~1Ω. Since the value of R1 already ensures that the LED will not be damaged by overcurrent, R2 only needs to serve as a sampling resistor. Assuming r2 = 1Ω, the maximum current in the entire circuit is I2 = 5V / (20 + 1)Ω = 0.235A, and the maximum voltage across R2 is 0.235A * 1Ω = 0.235V. The value of V1 is 0~0.235V, just make sure it does not damage the MOSFET.

[0034] This utility model provides an LED stepless dimming circuit 100, including: an adjustable voltage unit 11, an operational amplifier U1, a switching transistor VT1, a first resistor R1, an LED, and a second resistor R2. The adjustable voltage unit 11 outputs an adjustable voltage V1; the non-inverting input terminal of the operational amplifier U1 is connected to the output terminal of the adjustable voltage unit 11 to obtain the adjustable voltage V1; the controlled terminal of the switching transistor VT1 is connected to the output terminal of the operational amplifier U1; the anode of the LED is connected to VCC through the first resistor R1, and the cathode of the LED is connected to the first terminal of the switching transistor VT1; the first terminal of the second resistor R2 is connected to the second terminal of the switching transistor VT1 and the inverting input terminal of the operational amplifier U1, and the second terminal of the second resistor R2 is grounded. The adjustable voltage is used to control the switching transistor to be in the linear region, which has the following advantages: 1. The circuit does not require a PWM chip, reducing device costs; 2. After changing the adjustable voltage V1, the current flowing through the LED can quickly change with the adjustable voltage V1, causing the LED to quickly change in brightness, improving the user experience.

[0035] In some embodiments, such as Figure 2 As shown, the adjustable voltage unit 11 includes: an adjustable voltage source E1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first capacitor C1. The adjustable voltage source E1 is used to output an initial adjustment voltage. The output terminal of the adjustable voltage source E1 is connected to the first terminal of the third resistor R3. The second terminal of the third resistor R3 is connected to the first terminal of the fourth resistor R4, the first terminal of the first capacitor C1, and the first terminal of the fourth resistor R4. The second terminals of the fourth resistor R4 and the first capacitor C1 are both grounded. The second terminal of the fifth resistor R5 is connected to the non-inverting input terminal of the operational amplifier U1.

[0036] For example, the adjustable voltage source E1 is implemented through an adjustable resistor array and VCC. The adjustable resistor array divides VCC to obtain the initial voltage V0. The third resistor R3 and the fourth resistor R4 are used to adjust the initial voltage V0 to obtain the adjustable voltage V1. The first capacitor C1 is used for filtering, and the fifth resistor R5 is used for current limiting, both to prevent the adjustable voltage V1 from impacting the operational amplifier U1.

[0037] In some embodiments, the LED stepless dimming circuit 100 further includes a sixth resistor R6 and a seventh resistor R7.

[0038] The first terminal of the sixth resistor R6 is connected to the output terminal of the operational amplifier U1, and the second terminal of the sixth resistor R6 is connected to the controlled terminal of the switching transistor VT1. The sixth resistor R6 is used for current limiting to prevent the high-level signal output by the operational amplifier U1 from impacting the switching transistor VT1.

[0039] The first terminal of the seventh resistor R7 is connected to the first terminal of the second resistor R2, and the second terminal of the seventh resistor R7 is connected to the inverting input terminal. The seventh resistor R7 is used for current limiting to prevent VCC from impacting the LED.

[0040] This utility model also provides an electronic device, which includes an LED stepless dimming circuit 100 as described in any one of the present utility model.

[0041] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An LED stepless dimming circuit, characterized in that, The application relates to an LED stepless dimming circuit. The LED stepless dimming circuit comprises a voltage-adjusting unit, an operational amplifier, a switch tube, a first resistor, an LED, a second resistor and a sixth resistor and a seventh resistor. The non-inverted input end of the operational amplifier is connected with the output end of the voltage-adjusting unit to obtain the adjustable voltage. The controlled end of the switch tube is connected with the output end of the operational amplifier. The anode of the LED is connected with VCC through the first resistor, and the cathode of the LED is connected with the first end of the switch tube. The first end of the second resistor is connected with the second end of the switch tube and the inverted input end of the operational amplifier respectively, and the second end of the second resistor is grounded. The adjustable voltage is used for controlling the switch tube to be in a linear region. The voltage-adjusting unit comprises a voltage-adjusting source, a third resistor, a fourth resistor, a fifth resistor and a first capacitor.

2. The LED stepless dimming circuit according to claim 1, wherein, The voltage-adjusting source is used for outputting an initial adjusting voltage, the output end of the voltage-adjusting source is connected with the first end of the third resistor, the second end of the third resistor is connected with the first end of the fourth resistor, the first end of the first capacitor and the first end of the fourth resistor respectively, the second end of the fourth resistor and the second end of the first capacitor are grounded, and the second end of the fifth resistor is connected with the non-inverted input end of the operational amplifier. The LED stepless dimming circuit further comprises the sixth resistor and the seventh resistor.

3. The LED stepless dimming circuit of claim 1, wherein, The first end of the sixth resistor is connected with the output end of the operational amplifier, and the second end of the sixth resistor is connected with the controlled end of the switch tube. The first end of the seventh resistor is connected with the first end of the second resistor, and the second end of the seventh resistor is connected with the inverted input end. The electronic device comprises the LED stepless dimming circuit as claimed in any one of claims 1 to 3.

4. An electronic device, comprising: ​

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