A low-cost linear constant current drive circuit based on PWM dimming mode

Abstract

The utility model relates to the technical field of LED regulation control, and specifically discloses a low-cost linear constant-current driving circuit based on a PWM dimming mode, comprising an anti-reverse module, a driving module and an adjusting module which are arranged in sequence; the anti-reverse module comprises a transient voltage suppression diode and an input filter capacitor and an input filter resistor which are respectively connected in parallel with the transient voltage suppression diode; the driving module comprises a plurality of driving resistors which are respectively connected in parallel with the LED; the adjusting module comprises a first regulating transistor, a second regulating transistor and an adjusting resistor, the two ends of the regulating resistor are respectively connected to the emitters of the first regulating transistor and the second regulating transistor, the collector of the first regulating transistor is connected to the LED, the base of the first regulating transistor is connected to the driving resistor, the base of the second regulating transistor is connected to the PWM interface, and the collector of the second regulating transistor is connected to the driving resistor, so as to solve the problem that a complex peripheral circuit is required in the traditional LED brightness regulation, resulting in an increased difficulty in circuit design.

Description

Technical Field

[0001] The present application relates to the technical field of LED regulation control, and specifically discloses a low-cost linear constant current drive circuit based on a PWM dimming mode. Background Art

[0002] LED (light emitting diode) has been widely used in the field of lighting due to its advantages of high efficiency, energy saving and environmental protection. However, the brightness of LED is affected by its driving current. Therefore, how to accurately control the brightness of LED, that is, to achieve LED dimming, is the key to LED lighting technology.

[0003] At present, PWM (pulse width modulation) dimming is a commonly used dimming method, which adjusts the brightness of the LED by changing the duty cycle of the pulse signal. In addition, the linear constant current power supply is also an important part of the LED driver, which can provide a stable current to ensure the normal operation of the LED.

[0004] In the existing technology, a dedicated LED driver chip is usually used to implement PWM dimming and linear constant current drive. At the same time, by inputting a PWM signal, precise control of the LED brightness can be achieved. However, the existing LED brightness adjustment has the following problems:

[0005] First, the price of dedicated LED driver chips is relatively high, which increases the cost of LED lighting products; second, the existing LED brightness adjustment usually requires complex peripheral circuits, which not only increases the difficulty of circuit design, but also increases the complexity and failure rate of the LED brightness adjustment system; finally, the existing LED brightness adjustment needs to be improved in dimming accuracy and dimming range, and cannot meet the needs of some special applications. Therefore, in view of this, the inventor provides a low-cost linear constant current drive circuit based on PWM dimming mode to solve the above problems. Utility Model Content

[0006] The utility model aims to solve the problem that in the traditional LED brightness adjustment, a complex peripheral circuit is required, which increases the difficulty of circuit design and improves the complexity and failure rate of the LED brightness adjustment system.

[0007] In order to achieve the above-mentioned purpose, the basic scheme of the utility model provides a low-cost linear constant current driving circuit based on PWM dimming mode, including an anti-reverse module, a driving module and an adjusting module arranged in sequence;

[0008] The anti-reverse module includes a transient voltage suppression diode and an input filter capacitor and an input filter resistor respectively connected in parallel with the transient voltage suppression diode;

[0009] The driving module includes a plurality of driving resistors respectively connected in parallel with the LEDs and in series with the anti-reverse module;

[0010] The regulating module includes a first regulating transistor, a second regulating transistor and a regulating resistor, wherein the two ends of the regulating resistor are respectively connected to the emitters of the first regulating transistor and the second regulating transistor, the collector of the first regulating transistor is connected to the LED, the base of the first regulating transistor is connected to the driving resistor, the base of the second regulating transistor is connected to the PWM interface, and the collector of the second regulating transistor is connected to the driving resistor.

[0011] Furthermore, there are a plurality of driving resistors connected in parallel with each other, and there are a plurality of adjusting resistors connected in parallel with each other.

[0012] Furthermore, the base of the first regulating transistor is connected to a base resistor, the base of the second regulating transistor is connected to a base capacitor, and the base capacitor is also connected to a ground terminal.

[0013] Furthermore, the emitter of the second regulating transistor and the regulating resistor are both connected to the ground terminal.

[0014] Furthermore, a voltage stabilizing diode and a voltage stabilizing capacitor are connected between the emitter and the collector of the second regulating transistor.

[0015] Furthermore, the anti-reverse module also includes an anti-reverse diode, the input end of the anti-reverse diode is connected to the Vbat terminal, and the output end of the anti-reverse diode is connected to the driving resistor and the LED.

[0016] Furthermore, the transient voltage suppression diode, the input filter capacitor, and the input filter resistor are all connected to the ground terminal.

[0017] The principle and effect of this scheme are:

[0018] Compared with the prior art, the present invention adopts a low-cost PWM dimming mode, and adjusts the opening and closing of the second regulating transistor and the voltage-stabilizing diode by externally inputting a PWM signal to realize a linear constant current drive, thereby avoiding the use of a dedicated LED driver chip and greatly reducing the cost of LED lighting products; compared with the prior art which requires complex peripheral circuits, the design of the present invention is simpler, which reduces the difficulty of design, and also improves the stability and reliability of the system; by inputting a PWM signal, precise control of the LED brightness can be achieved, and the dimming accuracy is improved. At the same time, the dimming range of the present invention is wider, which can meet the needs of more special applications. That is, the present invention has lower costs, simpler designs, higher dimming accuracy and wider dimming range, and has obvious advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic diagram of a low-cost linear constant current drive circuit based on a PWM dimming mode proposed in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the utility model, the specific implementation method, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0022] The figure marks in the drawings of the specification include: transient voltage suppression diode Z1, first input filter capacitor C1, second input filter capacitor C2, third input filter capacitor C3, voltage stabilizing capacitor C4, base capacitor C5, first drive resistor R1, second drive resistor R2, base resistor R3, input filter resistor R4, first adjustment resistor R5, second adjustment resistor R6, first LED lamp D1, second LED lamp D1, anti-reverse diode D3, first adjustment transistor Q1, second adjustment transistor Q2.

[0023] A low-cost linear constant current drive circuit based on PWM dimming mode, implementing Figure 1 As shown, it includes an anti-reverse module, a driving module and an adjusting module which are arranged in sequence;

[0024] The anti-reverse module includes a transient voltage suppression diode Z1, an input filter capacitor and an input filter resistor R4 respectively connected in parallel with the transient voltage suppression diode Z1, and an anti-reverse diode D3. The input end of the anti-reverse diode D3 is connected to the Vbat terminal, wherein there are three input filter capacitors, namely, a first input filter capacitor C1, a second input filter capacitor C2, and a third input filter capacitor C3 arranged between the output end of the anti-reverse diode D3 and the transient voltage suppression diode Z1, and the transient voltage suppression diode Z1, the input filter capacitor, and the input filter resistor R4 are all connected to the ground terminal.

[0025] The driving module includes a plurality of driving resistors respectively connected in parallel with the LEDs and in series with the output end of the anti-reverse diode D3 of the anti-reverse module. There are two driving resistors, namely, a first driving resistor R1 and a second driving resistor R2 connected in parallel with each other. In this embodiment, two LEDs connected in parallel are taken as an example, namely, a first LED lamp and a second LED lamp.

[0026] The regulating module includes a first regulating transistor Q1, a second regulating transistor Q2 and a regulating resistor. There are two regulating resistors, namely, two first regulating resistors R5 and second regulating resistors R6 connected in parallel with each other. The two ends of the regulating resistors are respectively connected to the emitters of the first regulating transistor Q1 and the second regulating transistor Q2. The collector of the first regulating transistor Q1 is connected to the LED, the base of the first regulating transistor Q1 is connected to the driving resistor, the base of the second regulating transistor Q2 is connected to the PWM interface, the collector of the second regulating transistor Q2 is connected to the driving resistor, and a zener diode and a zener capacitor C4 are also connected between the emitter and the collector of the second regulating transistor Q2.

[0027] The base of the first regulating transistor Q1 is connected to the base resistor R3, the base of the second regulating transistor Q2 is connected to the base capacitor C5, the base capacitor C5 is also connected to the ground terminal, and the emitter of the second regulating transistor Q2, the stabilizing capacitor C4, the stabilizing diode and the regulating resistor are all connected to the ground terminal.

[0028] In this embodiment, the transient voltage suppression diode Z1 and the anti-reverse diode D3 protect the input signal of the Vbat terminal. Part of the input signal of the Vbat terminal is given to the positive electrode of the LED, and the other part is given to the driving resistor. After being stepped down by the voltage regulator diode, it stabilizes to a constant value, and the voltage from the base of the first regulating transistor Q1 to the ground terminal is equal to the constant value, minus the conduction voltage drop of the first regulating transistor Q1 is equal to the voltage drop of the regulating resistor, so that the current of the LED can be adjusted by adjusting the resistance value of the two regulating resistors connected in parallel to achieve constant current drive, and the second regulating transistor Q2 is used to turn on the voltage regulator diode, and the second regulating transistor Q2 is turned on by the input signal of the PWM interface, so that the LED is turned on by the voltage regulator diode, and the duty cycle is adjusted to achieve high and low brightness LEDs.

[0029] Compared with the prior art which requires complex peripheral circuits, the design of the utility model is simpler, which reduces the difficulty of design and improves the stability and reliability of the system. By inputting PWM signals, the brightness of the LED can be accurately controlled, and the dimming accuracy is improved. At the same time, the dimming range of the utility model is wider, which can meet the needs of more special applications. That is, the utility model has lower cost, simpler design, higher dimming accuracy and wider dimming range, and has obvious advantages.

[0030] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A low-cost linear constant current drive circuit based on PWM dimming mode, characterized in that: It includes an anti-reverse module, a driving module and an adjusting module which are arranged in sequence; The anti-reverse module includes a transient voltage suppression diode and an input filter capacitor and an input filter resistor respectively connected in parallel with the transient voltage suppression diode; The driving module includes a plurality of driving resistors respectively connected in parallel with the LEDs and in series with the anti-reverse module; The regulating module includes a first regulating transistor, a second regulating transistor and a regulating resistor, wherein the two ends of the regulating resistor are respectively connected to the emitters of the first regulating transistor and the second regulating transistor, the collector of the first regulating transistor is connected to the LED, the base of the first regulating transistor is connected to the driving resistor, the base of the second regulating transistor is connected to the PWM interface, and the collector of the second regulating transistor is connected to the driving resistor.

2. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 1, characterized in that: There are several driving resistors connected in parallel with each other, and there are several adjusting resistors connected in parallel with each other.

3. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 1, characterized in that: The base of the first regulating transistor is connected to a base resistor, the base of the second regulating transistor is connected to a base capacitor, and the base capacitor is also connected to a ground terminal.

4. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 3, characterized in that: The emitter of the second regulating transistor and the regulating resistor are both connected to the ground terminal.

5. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 1, characterized in that: A voltage stabilizing diode and a voltage stabilizing capacitor are also connected between the emitter and the collector of the second regulating transistor.

6. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 1, characterized in that: The anti-reverse module also includes an anti-reverse diode, the input end of the anti-reverse diode is connected to the Vbat terminal, and the output end of the anti-reverse diode is connected to the driving resistor and the LED.

7. A low-cost linear constant current driving circuit based on PWM dimming mode according to claim 6, characterized in that: The transient voltage suppression diode, the input filter capacitor, and the input filter resistor are all connected to the ground terminal.

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