LED brightness adjustment circuit

Abstract

The embodiment of the present invention discloses an LED brightness adjustment circuit. The circuit includes: a brightness adjustment module and a parameter adjustment module; wherein the brightness adjustment module includes a light-emitting diode to be controlled, and a transistor connected in series with the light-emitting diode, and the brightness adjustment module is used to adjust the brightness of the light-emitting diode according to the input parameters of the transistor; the parameter adjustment module is used to connect to the IO port of the main control chip through at least one signal input terminal, and adjust the input parameters according to the output state of the IO port. It does not require a dedicated IO port on the main control chip to realize special functions, that is, it does not require the use of a dedicated chip. On the basis of providing multiple brightness level controls, it effectively reduces the implementation cost, thereby improving the user experience of the product and enhancing the product value.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of LED control, and in particular to an LED brightness adjustment circuit. Background Art

[0002] At present, LED has been widely used in many fields, such as screen backlight or indicator light, etc. With the increasing use, there is also a demand for LED brightness adjustment. Taking screen backlight as an example, LED backlight is the light source of LCD screen, and its brightness determines the brightness of LCD screen. In traditional application scenarios, LED backlight only needs to be able to be lit, that is, as long as a suitable voltage and a fixed current are provided at both ends of the LED, the LED can work at a fixed power. However, when the ambient light brightness changes, it will affect the user experience. For example, it will feel darker outdoors during the day and brighter at night. Therefore, there is a need for LED backlight brightness adjustment.

[0003] The existing solution is to output the control signal and PWM signal through the dedicated pins of the chip, so as to control the on and off of the LED through the control signal and adjust the brightness of the LED through the PWM signal. This solution usually requires the use of a dedicated chip, which is costly. Summary of the invention

[0004] The embodiment of the present invention provides an LED brightness adjustment circuit to solve the problem of high cost of current LED brightness adjustment.

[0005] The embodiment of the present invention provides an LED brightness adjustment circuit, which includes: a brightness adjustment module and a parameter adjustment module; wherein:

[0006] The brightness adjustment module includes a light emitting diode to be controlled and a transistor connected in series with the light emitting diode, and the brightness adjustment module is used to adjust the brightness of the light emitting diode according to input parameters of the transistor;

[0007] The parameter adjustment module is used to connect to the IO port of the main control chip through at least one signal input terminal, and adjust the input parameter according to the output state of the IO port.

[0008] Optionally, the transistor is an NPN-type transistor.

[0009] Optionally, the brightness adjustment module further includes a first resistor, which is connected in series between the cathode of the light-emitting diode and the collector of the transistor, the anode of the light-emitting diode is connected to a working power supply, and the emitter of the transistor is grounded.

[0010] Optionally, the parameter adjustment module includes a first signal input terminal, a second resistor and a third resistor, the second resistor is connected in series between the first signal input terminal and the base of the transistor, one end of the third resistor is connected between the first signal input terminal and the second resistor, and the other end is connected to the working power supply.

[0011] Optionally, the first resistor is 18 ohms, the second resistor is 1 kiloohm, the third resistor is 4.2 kiloohms, the operating voltage of the light emitting diode is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor is 100.

[0012] Optionally, the parameter adjustment module includes a second signal input terminal, a third signal input terminal, a fourth resistor and a fifth resistor, the fourth resistor and the fifth resistor are connected in series between the second signal input terminal and the third signal input terminal, and the base of the transistor is connected between the fourth resistor and the fifth resistor.

[0013] Optionally, the first resistor is 18 ohms, the fourth resistor is 3.5 kiloohms, the fifth resistor is 7 kiloohms, the operating voltage of the light emitting diode is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor is 100.

[0014] Optionally, the working power supply is a 3.3 volt DC power supply.

[0015] Optionally, the output state includes: a low level state, a suspended state and a high level state.

[0016] Optionally, the IO port is a general IO port of the main control chip.

[0017] The embodiment of the present invention provides an LED brightness adjustment circuit, including a brightness adjustment module and a parameter adjustment module. The brightness adjustment module includes a light-emitting diode to be controlled and a transistor connected in series with the light-emitting diode. The parameter adjustment module includes at least one signal input terminal connected to an IO port of a main control chip. The input parameters of the transistor are adjusted through different output states of the IO port of the main control chip to obtain different output currents of the transistor, thereby realizing brightness adjustment of the light-emitting diode. The LED brightness adjustment circuit provided by the embodiment of the present invention does not require a dedicated IO port for realizing special functions to be set on the main control chip, that is, it does not require the use of a dedicated chip. On the basis of providing multiple brightness level controls, the implementation cost is effectively reduced, thereby improving the user experience of the product and enhancing the product value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of an LED brightness adjustment circuit provided in Embodiment 1 of the present invention;

[0019] Figure 2 A schematic diagram of the structure of another LED brightness adjustment circuit provided in Embodiment 1 of the present invention;

[0020] Figure 3 This is a structural schematic diagram of another LED brightness adjustment circuit provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0022] It should be mentioned before discussing the exemplary embodiments in more detail that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the steps as sequential processes, many of the steps therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of the steps can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0023] In addition, the terms "first", "second", etc. may be used in this article to describe various directions, actions, steps or elements, but these directions, actions, steps or elements are not limited by these terms. These terms are only used to distinguish a first direction, action, step or element from another direction, action, step or element. For example, without departing from the scope of the embodiment of the present invention, the first resistor may be referred to as the second resistor, and similarly, the second resistor may be referred to as the first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor. The terms "first", "second", etc. cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may expressly or implicitly include one or more of the features. In the description of the embodiment of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] Embodiment 1

[0025] Figure 1 This is a schematic diagram of the structure of the LED brightness adjustment circuit provided in the first embodiment of the present invention. This embodiment can be applied to the situation of adjusting the brightness of LEDs in various occasions. Figure 1As shown, the brightness adjustment circuit 100 includes: a brightness adjustment module 110 and a parameter adjustment module 120; wherein the brightness adjustment module 110 includes a light-emitting diode to be controlled, and a transistor connected in series with the light-emitting diode, and the brightness adjustment module 110 is used to adjust the brightness of the light-emitting diode according to the input parameters of the transistor; the parameter adjustment module 120 is used to connect to the IO port of the main control chip through at least one signal input terminal IO, and adjust the input parameter according to the output state of the IO port.

[0026] Specifically, as a light-emitting diode (LED), which is a light-emitting component, there are two pins. As long as a suitable driving voltage is added to form a current, the LED will emit light, and the intensity of its light emission is related to the power, and the power is equal to the voltage multiplied by the current. Since the LED is essentially a diode, it is a nonlinear component, that is, the current is not proportional to the voltage, and its voltage does not change much after being turned on, so its power is roughly proportional to the current. Based on this, in the brightness adjustment module 110, the light-emitting diode to be controlled can be connected in series with the transistor, that is, the output current of the transistor is the current of the light-emitting diode, so that the brightness of the light-emitting diode can be adjusted by the output current of the transistor. The output current of the transistor can be adjusted by the input parameters, and the input parameters can include input current and input voltage, etc., which can be determined according to the specific transistor type. Then the brightness adjustment module 110 can adjust the brightness of the light-emitting diode according to the input parameters given to the transistor, and the transistor can work in an amplified state. On the one hand, the parameter adjustment module 120 can be connected to the IO port of the main control chip through the signal input terminal IO, wherein the IO port can be a general IO port of the main control chip, that is, no special design is required, as long as the main control chip has extra general IO ports, these general IO ports can be used to realize the function of changing the brightness of the LED. On the other hand, the parameter adjustment module 120 can also be connected to the base of the transistor in the brightness adjustment module 110 by using a circuit composed of one or more resistors to provide input parameters for the transistor, so that different input parameters can be provided for the transistor under different output states of the IO port of the main control chip, thereby realizing the adjustment of the brightness of the LED. Wherein, optionally, the output state includes: low level state (outputlow), floating state (float) and high level state (output high), the level of the IO port is 0V in the low level state, equivalent to disconnection in the floating state, and the level of the IO port is 3.3V in the high level state. Then, using a signal input terminal IO to access an IO port can provide three different input parameters, and using multiple signal input terminals IO to access multiple IO ports respectively, more different input parameters can be provided through the combination of different output states, so that various multi-level brightness adjustments can be realized according to requirements.

[0027] On the basis of the above technical solution, optionally, the transistor is an NPN-type triode, and the brightness adjustment module 110 can specifically adjust the output current of the triode according to the base current of the triode, thereby adjusting the brightness of the light-emitting diode.

[0028] Further optional, such as Figure 2 and Figure 3 As shown, the brightness adjustment module 110 also includes a first resistor R1, which is connected in series between the negative electrode of the light-emitting diode VD and the collector c of the transistor Q, the positive electrode of the light-emitting diode VD is connected to the working power supply VCC, and the emitter e of the transistor Q is grounded. Then, the working voltage and maximum working current of the light-emitting diode VD used can be matched, and by selecting the first resistor R1 with a suitable resistance value, the light-emitting diode VD can reach its maximum brightness under the limitation of the working power supply VCC, thereby achieving better utilization of the light-emitting diode VD. Optionally, the working power supply is a 3.3V DC power supply, which is convenient for the main control chip to provide.

[0029] Further optional, such as Figure 2 As shown, the parameter adjustment module 120 includes a first signal input terminal IO1, a second resistor R2 and a third resistor R3, wherein the second resistor R2 is connected in series between the first signal input terminal IO1 and the base b of the transistor Q, one end of the third resistor R3 is connected between the first signal input terminal IO1 and the second resistor R2, and the other end is connected to the working power supply VCC. Specifically, the first signal input terminal IO1 can be connected to an IO port of the main control chip. When the output state of the IO port is a low level state, the voltage across the second resistor R2 is 0V, the voltage of the base b is pulled down, that is, no current flows through the base b, and the current of the collector c of the corresponding transistor Q, that is, the current of the light emitting diode VD, is 0, and the brightness of the LED is 0. When the output state of the IO port is a suspended state, a voltage can be applied to the base b of the transistor Q through the working power supply VCC through the second resistor R2 and the third resistor R3 to turn it on. When the output state of the IO port is a high level state, a voltage can be applied to the base b of the transistor Q through the second resistor R2 through the level output by the IO port to turn it on. The different brightness of the LED in the suspended state and the high level state can also be configured by selecting the resistance values ​​of the second resistor R2 and the third resistor R3.

[0030] Among them, optionally, the first resistor R1 is 18 ohms, the second resistor R2 is 1 kiloohm, the third resistor R3 is 4.2 kiloohms, the operating voltage of the light emitting diode VD is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor Q is 100. As mentioned above, in the low level state, the brightness of the LED is 0; in the suspended state, the series resistance of the second resistor R2 and the third resistor R3 is 5.2 kilo-ohms, and the working power supply VCC applies a voltage to the base b of the transistor Q through the second resistor R2 and the third resistor R3 to turn it on. At this time, the level of the base b is 0.7V, then the current through the base b = (3.3V-0.7V) / 5.2KΩ = 0.5mA, the output current of the transistor Q, that is, the current of the collector c = 0.5mA*100 = 50mA, that is, the current of the light-emitting diode VD is 50mA, that is, 50% of the maximum working current, and the brightness of the LED is 50% of the maximum brightness; in the high level state, the level of the first signal input terminal IO1 is 3.3V, and a voltage is applied to the base b of the transistor Q through the second resistor R2. Voltage turns it on, at this time the level of base b is 0.7V, then the current through base b = (3.3V-0.7V) / 1KΩ = 2.6mA, assuming the current of collector c = 2.6mA*100 = 260mA, then the voltage across the first resistor R1 = 260mA*18Ω = 4.68V, at this time due to the working voltage of the light emitting diode VD + the voltage across the first resistor R1 = 1.5V+4.68V = 6.18V, greater than the level of the working power supply VCC 3.3V, so in fact the voltage across the first resistor R1 = 3.3V-1.5V = 1.8V, then the current through the first resistor R1, that is, the current of the light emitting diode VD is 1.8V / 18Ω = 100mA, that is, 100% of the maximum working current, the brightness of the LED is the maximum brightness. By using a single IO port to be set to three states: low level state, suspended state and high level state, the brightness of the light-emitting diode can be controlled to be 0, 50% of the maximum brightness and 100% of the maximum brightness respectively, which is more in line with the actual needs under a small number of brightness levels.

[0031] or alternatively, such as Figure 3 As shown, the parameter adjustment module 120 includes a second signal input terminal IO2, a third signal input terminal IO3, a fourth resistor R4 and a fifth resistor R5, wherein the fourth resistor R4 and the fifth resistor R5 are connected in series between the second signal input terminal IO2 and the third signal input terminal IO3, and the base b of the transistor Q is connected between the fourth resistor R4 and the fifth resistor R5. Specifically, the second signal input terminal IO2 and the third signal input terminal IO3 can be connected to two IO ports of the main control chip respectively, and the two IO ports can also be set to a low level state, a suspended state and a high level state respectively. For the brightness control of various output state combinations, the above analysis process can be referred to.

[0032] Among them, optionally, the first resistor R1 is 18 ohms, the fourth resistor R4 is 3.5 kilo ohms, the fifth resistor R5 is 7 kilo ohms, the operating voltage of the light emitting diode VD is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor Q is 100. Then, using a similar method, the current flowing through the light emitting diode VD under various combinations of output states can be calculated as follows: when the second signal input terminal IO2 and the third signal input terminal IO3 are both in a low level state, the current is 0; when the second signal input terminal IO2 is in a low level state and the third signal input terminal IO3 is in a suspended state, the current is 0; when the second signal input terminal IO2 is in a low level state and the third signal input terminal IO3 is in a high level state, the current is 17mA; when the second signal input terminal IO2 is in a suspended state and the third signal input terminal IO3 is in a low level ... When the signal input terminal IO2 and the third signal input terminal IO3 are both in the suspended state, the current is 0; when the second signal input terminal IO2 is in the suspended state and the third signal input terminal IO3 is in the high level state, the current is 37mA; when the second signal input terminal IO2 is in the high level state and the third signal input terminal IO3 is in the low level state, the current is 64mA; when the second signal input terminal IO2 is in the high level state and the third signal input terminal IO3 is in the suspended state, the current is 74mA; when the second signal input terminal IO2 and the third signal input terminal IO3 are both in the high level state, the current is 100mA. The different output state settings of the two IO ports can be used to control the light emitting diode to be 0, 17% of the maximum brightness, 37% of the maximum brightness, 64% of the maximum brightness, 74% of the maximum brightness and 100% of the maximum brightness, thereby providing more brightness levels and being applicable to more application scenarios.

[0033] Similarly, more brightness level controls can be achieved by modifying the number, type or parameters of the above-mentioned resistors or transistors, or increasing the number of IO ports of the main control chip used.

[0034] The LED brightness adjustment circuit provided by the embodiment of the present invention includes a brightness adjustment module and a parameter adjustment module. The brightness adjustment module includes a light-emitting diode to be controlled and a transistor connected in series with the light-emitting diode. The parameter adjustment module includes at least one signal input terminal connected to the IO port of the main control chip. The input parameters of the transistor are adjusted through different output states of the IO port of the main control chip to obtain different output currents of the transistor, thereby realizing brightness adjustment of the light-emitting diode. It does not require a dedicated IO port for realizing special functions to be set on the main control chip, that is, it does not require the use of a dedicated chip. On the basis of providing multiple brightness level controls, the implementation cost is effectively reduced, thereby improving the user experience of the product and enhancing the product value.

[0035] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An LED brightness adjustment circuit, characterized in that: include: Brightness adjustment module and parameter adjustment module; wherein, The brightness adjustment module includes a light emitting diode to be controlled and a transistor connected in series with the light emitting diode, and the brightness adjustment module is used to adjust the brightness of the light emitting diode according to input parameters of the transistor; The parameter adjustment module is used to connect to the IO port of the main control chip through at least one signal input terminal, and adjust the input parameter according to the output state of the IO port, and provide different input parameters for the transistor in different output states; the output state includes: low level state, suspension state and high level state; The transistor is an NPN-type triode; the brightness adjustment module further includes a first resistor, which is connected in series between the cathode of the light-emitting diode and the collector of the transistor, the anode of the light-emitting diode is connected to a working power supply, and the emitter of the transistor is grounded; The parameter adjustment module includes a first signal input terminal, a second resistor and a third resistor, the second resistor is connected in series between the first signal input terminal and the base of the transistor, one end of the third resistor is connected between the first signal input terminal and the second resistor, and the other end is connected to the working power supply, when the output state of the IO port connected to the first signal input terminal is a low level state, the voltage across the second resistor is 0, the base voltage of the transistor is pulled down, and the brightness of the light emitting diode is 0, when the output state of the IO port connected to the first signal input terminal is a suspended state, the working power supply applies a voltage to the base of the transistor through the third resistor and the second resistor to turn it on, and when the output state of the IO port connected to the first signal input terminal is a high level state, the The level output by the IO port connected to the first signal input terminal applies a voltage to the base of the transistor through the second resistor to turn it on, and the different brightness of the light-emitting diode in the suspended state and the high-level state is configured according to the selected resistance values ​​of the second resistor and the third resistor; or the parameter adjustment module includes a second signal input terminal, a third signal input terminal, a fourth resistor and a fifth resistor, the fourth resistor and the fifth resistor are connected in series between the second signal input terminal and the third signal input terminal, the base of the transistor is connected between the fourth resistor and the fifth resistor, the second signal input terminal and the third signal input terminal are respectively connected to the two IO ports of the main control chip, and the output states of the two IO ports are respectively one of a low-level state, a suspended state and a high-level state.

2. The LED brightness adjustment circuit according to claim 1, characterized in that: The first resistor is 18 ohms, the second resistor is 1 kiloohm, the third resistor is 4.2 kiloohms, the operating voltage of the light emitting diode is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor is 100.

3. The LED brightness adjustment circuit according to claim 1, characterized in that: The first resistor is 18 ohms, the fourth resistor is 3.5 kilo ohms, the fifth resistor is 7 kilo ohms, the operating voltage of the light emitting diode is 1.5 volts, the maximum operating current is 100 milliamperes, and the current amplification factor of the transistor is 100.

4. The LED brightness adjustment circuit according to claim 1, characterized in that: The working power supply is a 3.3 volt direct current power supply.

5. The LED brightness adjustment circuit according to claim 1, characterized in that: The IO port is a general IO port of the main control chip.

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