CN210274618U - PWM dimming circuit - Google Patents

Abstract

The application discloses PWM dimming circuit, including constant current power supply module, power module, the light emitting module of a plurality of n series connections, every light emitting module includes parallelly connected LED and first switch tube, wherein: the first end of the power supply module is respectively connected with the first end of the constant current power supply module and the first end of the first light-emitting module, the second end of the power supply module and the second end of the constant current power supply module are both grounded, the control ends of the constant current power supply module are respectively connected with the control ends of all the first switch tubes, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module. This application connects a first switch tube in parallel at LED both ends, and in the twinkling of an eye when the PWM signal changes, through the switch on or turn-off of controlling first switch tube, makes the corresponding change of LED electric current, in addition, establishes ties all light emitting module, need not set up multichannel constant current power supply module, and circuit structure is simple, and is with low costs.

Description

PWM dimming circuit

Technical Field

The application relates to the field of PWM dimming, in particular to a PWM dimming circuit.

Background

In professional LED lighting systems, such as studios, theaters, etc., very strict requirements are imposed on PWM dynamic dimming. In such applications, LEDs with colors of R (red), G (green), B (blue), W (white), and Y (yellow) are usually included, and in order to achieve the illumination effect, the PWM signals are required to control the on duty ratios of the respective colors, so as to mix the colors into light with various colors.

In the current application system, a commonly used dimming circuit adopts an inductive current hysteresis control architecture, and when a PWM signal changes within a certain range, the LED current does not change, resulting in visual seizure. And when a plurality of LEDs are independently controllable, a plurality of independent constant current power supplies are needed to control the plurality of LEDs respectively, so that the cost is high, the complexity is high, and the reliability is reduced.

Therefore, how to provide a solution to the above technical problem is a problem that needs to be solved by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a PWM dimmer circuit connects a first switch tube in parallel at LED both ends, and in the twinkling of an eye when the PWM signal changes, through the switching on or the shutoff of controlling first switch tube, makes the corresponding change of LED electric current, in addition, establishes ties all light emitting module, need not set up multichannel constant current power supply module, and circuit structure is simple, and is with low costs.

In order to solve the above technical problem, the present application provides a PWM dimming circuit, including: constant current power supply module, power module, the luminous module of n series connection, every luminous module includes parallelly connected LED and first switch tube, and n is the positive integer, wherein:

the first end of the power supply module is respectively connected with the first end of the constant current power supply module and the first end of the first light-emitting module, the second end of the power supply module and the second end of the constant current power supply module are both grounded, the control ends of the constant current power supply module are respectively connected with the control ends of all the first switch tubes, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module;

the constant current power supply module receives n paths of PWM signals, when the PWM signals changed from high level to low level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched on, and when the PWM signals changed from low level to high level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched off.

Preferably, the constant current power supply module includes a controller, a second switching tube, an inductor, and a first diode, wherein:

the first control end of the controller is used as the control end of the constant current power supply module, the second control end of the controller is connected with the control end of the second switch tube, the first end of the controller and the cathode of the first diode are connected to be used as the first end of the constant current power supply module, the first end of the second switch tube is respectively connected with the first end of the inductor and the anode of the first diode, the second end of the inductor is used as the third end of the constant current power supply module, and the second end of the second switch tube is used as the second end of the constant current power supply module.

Preferably, the constant current power supply module further includes:

and the first end of the resistor is connected with the first diode, and the second end of the resistor is respectively connected with the first end of the first light-emitting module and the detection end of the controller.

Preferably, the PWM dimming circuit further includes a third switching tube and a second diode, wherein:

the second end of the third switching tube is connected with the cathode of the first diode, the first end of the third switching tube is connected with the first end of the first light-emitting module, the control end of the third switching tube is connected with the first control end of the controller, the cathode of the second diode is connected with the second end of the inductor, and the anode of the second diode is grounded.

Preferably, the second switch tube is an NMOS tube, and the third switch tube and all the first switch tubes are PMOS tubes.

The application provides a PWM dimming circuit, including constant current power supply module, power module, the light emitting module of a plurality of n series connection, every light emitting module includes parallelly connected LED and first switch tube, and n is the positive integer, wherein: the first end of the power supply module is respectively connected with the first end of the constant current power supply module and the first end of the first light-emitting module, the second end of the power supply module and the second end of the constant current power supply module are both grounded, the control ends of the constant current power supply module are respectively connected with the control ends of all the first switch tubes, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module; the constant current power supply module receives n paths of PWM signals, when the PWM signals changed from high level to low level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched on, and when the PWM signals changed from low level to high level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched off.

In practical application, by adopting the scheme of the application, the two ends of the LED are connected with the switching tube in parallel, when the PWM signal is changed from high to low, the constant current power supply module controls the switching tube to be switched on, at the moment, the LED is short-circuited, the current does not pass through the LED any more, when the PWM signal is changed from low to high, the constant current power supply module controls the switching tube to be switched off, the LED has the current to flow, namely when the PWM signal is changed, the current of the LED can be correspondingly changed, and therefore the purpose of controlling the current of the LED is achieved. In addition, all the light emitting modules are connected in series, when dimming is needed, corresponding PWM signals are applied to one constant current power supply module, multiple paths of constant current power supply modules are not needed, and the circuit is simple in structure and low in cost.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the prior art and the embodiments are briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a PWM dimming circuit provided in the present application;

fig. 2 is a schematic structural diagram of another PWM dimming circuit provided in the present application;

fig. 3a is a schematic structural diagram of another PWM dimming circuit provided in the present application;

FIG. 3b is a schematic diagram of a PWM signal and LED current waveform provided by the present application;

fig. 4 is a schematic structural diagram of another PWM dimming circuit provided in the present application;

fig. 5 is a schematic structural diagram of another PWM dimming circuit provided in the present application;

fig. 6 is a schematic structural diagram of another PWM dimming circuit provided in the present application.

Detailed Description

The core of this application is to provide a PWM dimmer circuit, connects a first switch tube in parallel at LED both ends, in the twinkling of an eye when the PWM signal changes, through the switch on or the shutoff of controlling first switch tube, makes the corresponding change of LED electric current, in addition, establishes ties all light emitting module, need not set up multichannel constant current power supply module, and circuit structure is simple, and is with low costs.

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a PWM dimming circuit provided in the present application, the PWM dimming circuit includes:

constant current power supply module 1, power module V1, the light emitting module 2 of n series connection, every light emitting module 2 includes parallelly connected LED and first switch tube M1, and n is the positive integer, wherein:

the first end of the power supply module V1 is respectively connected with the first end of the constant current power supply module 1 and the first end of the first light-emitting module, the second end of the power supply module V1 and the second end of the constant current power supply module 1 are both grounded, the control end of the constant current power supply module 1 is respectively connected with the control ends of all the first switch tubes M1, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module 1;

when the constant current power supply module 1 receives n paths of PWM signals, the first switching tube M1 in the light emitting module 2 corresponding to the PWM signal is controlled to be turned on when the PWM signal changed from the high level to the low level exists, and the first switching tube M1 in the light emitting module 2 corresponding to the PWM signal is controlled to be turned off when the PWM signal changed from the low level to the high level exists.

Specifically, all the LEDs are arranged in series, each LED is respectively denoted as an LED1, an LED2, …, and LEDn according to the series sequence, and correspondingly, the first switching tube M1 connected in parallel with each LED is denoted as M11, M12, …, and M13, in fig. 1, the first switching tube M1 is represented as a PMOS tube, and of course, the first switching tube M1 may also adopt other switching tubes having the same function as the PMOS tube, which is not limited herein.

As a preferred embodiment, referring to fig. 2, the constant current power supply module 1 includes a controller 11, a second switch M2, an inductor L1, and a first diode D1, in fig. 2, the second switch M2 is shown as an NMOS transistor, but the second switch M2 may also be another switch having the same function as the NMOS transistor, and the application is not limited herein. A first end of the controller 11 is connected to a cathode of the first diode D1, a first end of the power supply module V1, and a first end of the first light emitting module, a first control end of the controller 11 is connected to control ends of all the first switching tubes (M11, M12, …, M1n), a second control end of the controller 11 is connected to a control end of the second switching tube M2, a first end of the second switching tube M2 is connected to a first end of the inductor L1 and an anode of the first diode D1, a second end of the second switching tube M2 is connected to a second end of the power supply module V1 and ground, and a second end of the inductor L1 is connected to a second end of the nth light emitting module; the controller 11 is configured to receive the n-channel PWM signals, and when there is a PWM signal changed from a high level to a low level, control the first switching tube M1 in the light emitting module 2 corresponding to the PWM signal to be turned on, and when there is a PWM signal changed from a low level to a high level, control the first switching tube M1 in the light emitting module 2 corresponding to the PWM signal to be turned off.

Specifically, referring to fig. 3a, first, a control scheme when the PWM dimming circuit includes only one light emitting module 2 to convert the PWM signal is described, and when the PWM dimming circuit includes a plurality of light emitting modules 2, a control scheme for each light emitting module 2 is similarly described. The light emitting module 2 includes an LED1 and a first switch transistor M11, and assuming that the first switch transistor M11 is a PMOS transistor, a first end of the LED1 is connected to a source of the PMOS transistor as a first end of the light emitting module 2, and a second end of the LED1 is connected to a drain of the PMOS transistor as a second end of the light emitting module 2.

When the controller 11 detects the instant when the PWM signal changes from high level to low level, the first switching tube M11 in the lighting module 2 is controlled to be turned on, and the flow direction of the inductor current is L1 → D1 → M11, it can be seen that the inductor current no longer flows through the LED1, the LED1 is short-circuited, and the current of the LED1 is as shown in fig. 3b, at the instant when the PWM signal changes from high level to low level, the LED1 is short-circuited, so that the current of the LED1 is instantly reduced and not equal to the previous one, correspondingly, when the controller 11 detects the instant when the PWM signal changes from low level to high level, the first switching tube M11 in the lighting module 2 is controlled to be turned off, and at this time, a current flows through the LED1, so that when the PWM signal changes, the current of the LED1 also changes correspondingly, thereby achieving the purpose of controlling.

It can be understood that the controller 11 may receive multiple paths of PWM signals, and respectively control the corresponding LED and the first switch tube M1 according to the PWM signal of each path, and when a certain path of PWM signal changes, the controller 11 controls the first switch tube M1 corresponding to the changed PWM signal to turn on or off, thereby implementing independent control of multiple LEDs. When dimming is needed, the controller 11 is only required to add the corresponding PWM signal, for example, when the brightness of a certain LED needs to be increased, the duty ratio of the corresponding PWM signal is increased, and otherwise, the duty ratio of the corresponding PWM signal is decreased. Each LED in the PWM dimming circuit may be an LED displaying different colors, for example, LED1 displays red light, LED2 displays green light, LED3 displays blue light, and … … and LEDn display yellow light, although LED-LEDn may also display the same color.

The application provides a PWM dimming circuit, including constant current power supply module, power module, the light emitting module of a plurality of n series connection, every light emitting module includes parallelly connected LED and first switch tube, and n is the positive integer, wherein: the first end of the power supply module is respectively connected with the first end of the constant current power supply module and the first end of the first light-emitting module, the second end of the power supply module and the second end of the constant current power supply module are both grounded, the control ends of the constant current power supply module are respectively connected with the control ends of all the first switch tubes, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module; the constant current power supply module receives n paths of PWM signals, when the PWM signals changed from high level to low level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched on, and when the PWM signals changed from low level to high level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched off.

In practical application, by adopting the scheme of the application, the two ends of the LED are connected with the switching tube in parallel, when the PWM signal is changed from high to low, the constant current power supply module controls the switching tube to be switched on, at the moment, the LED is short-circuited, the current does not pass through the LED any more, when the PWM signal is changed from low to high, the constant current power supply module controls the switching tube to be switched off, the LED has the current to flow, namely when the PWM signal is changed, the current of the LED can be correspondingly changed, and therefore the purpose of controlling the current of the LED is achieved. In addition, all the light emitting modules are connected in series, when dimming is needed, corresponding PWM signals are applied to one constant current power supply module, multiple paths of constant current power supply modules are not needed, and the circuit is simple in structure and low in cost.

Referring to fig. 4, fig. 4 is a schematic structural diagram of another PWM dimming circuit provided in the present application, where the PWM dimming circuit is based on the foregoing embodiments:

as a preferred embodiment, the constant current power supply module 1 further includes:

and a resistor R1 having a first end connected to the first diode D1 and a second end connected to the first end of the first light-emitting module and the detection end of the controller 11.

Specifically, the controller 11 is further configured to obtain an inductor current, and when the inductor current is greater than a first preset current value I1, control the second switch tube M2 to turn off, and when the inductor current is less than a second preset current value I2, control the second switch tube M2 to turn on. Specifically, referring to fig. 5, taking an example that the PWM dimming circuit includes only one light emitting module 2 and the first switching tube M11 in the light emitting module 2 is turned off, a control scheme of the second switching tube M2 is described, when the controller 11 detects that the inductive current is lower than the second preset current value I2, the second switching tube M2 is controlled to be turned on, at this time, the current passes through V1+ → R1 → LED1 → L1 → M2 → V1 to form a loop, the inductive current is increased, the controller 11 obtains the current flowing through the resistor R1, which is the inductive current, when the inductive current increases to the first preset current value I1, the second switching tube M2 is controlled to be turned off, at this time, the inductive current cannot suddenly change, the L1 freewheels, the inductive current passes through L1 → D1 → R1 → LED1 to form a loop, because no extra power source provides energy at this time, so that the inductive current decreases, when the controller 11 detects that the inductive current decreases to the second preset current value I2, the controller 11 controls the second switch M2 to be turned on, and so on.

Referring to fig. 6, fig. 6 is a schematic structural diagram of another PWM dimming circuit provided in the present application, where the PWM dimming circuit is based on the foregoing embodiments:

as a preferred embodiment, the PWM dimming circuit further includes a third switching tube M3 and a second diode D2, wherein:

a second terminal of the third switching tube M3 is connected to a cathode of the first diode D1, a first terminal of the third switching tube M3 is connected to a first terminal of the first light emitting module, a control terminal of the third switching tube M3 is connected to a first control terminal of the controller 11, a cathode of the second diode D2 is connected to a second terminal of the inductor L1, and an anode of the second diode D2 is grounded.

Specifically, when all the LEDs are short-circuited, the freewheeling circuit is L1 → D1 → R1 → M11 → … → M1n, and considering that the voltage across the inductor L1 is low at this time, and therefore the freewheeling current is maintained for a long time, the present application further provides the third switching tube M3 and the second diode D2 in the PWM dimming circuit, and when all the LEDs are short-circuited, the controller 11 controls the third switching tube M3 to turn off, and the freewheeling circuit is changed to D2 → L1 → D1 → V1+ → GND, because the voltage difference across the inductor L1 is large at this time, and the inductor current is absorbed rapidly.

In a preferred embodiment, the second switch transistor M2 is an NMOS transistor, and the third switch transistor M3 and all the first switch transistors M1 are PMOS transistors.

Specifically, the drain of the NMOS transistor serves as the first end of the second switch transistor M2, the source of the NMOS transistor serves as the second end of the second switch transistor M2, the gate of the NMOS transistor serves as the control end of the second switch transistor M2, and correspondingly, the drain of the PMOS transistor serves as the first end of the third switch transistor M3, the source of the PMOS transistor serves as the second end of the third switch transistor M3, and the gate of the PMOS transistor serves as the control end of the third switch transistor M3.

It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" is not excluded from inclusion

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (5)

1. A PWM dimming circuit, comprising: constant current power supply module, power module, the luminous module of n series connection, every luminous module includes parallelly connected LED and first switch tube, and n is the positive integer, wherein:

the first end of the power supply module is respectively connected with the first end of the constant current power supply module and the first end of the first light-emitting module, the second end of the power supply module and the second end of the constant current power supply module are both grounded, the control ends of the constant current power supply module are respectively connected with the control ends of all the first switch tubes, and the second end of the nth light-emitting module is connected with the third end of the constant current power supply module;

the constant current power supply module receives n paths of PWM signals, when the PWM signals changed from high level to low level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched on, and when the PWM signals changed from low level to high level exist, the first switch tube in the light emitting module corresponding to the PWM signals is controlled to be switched off.

2. The PWM dimming circuit according to claim 1, wherein the constant current power supply module comprises a controller, a second switch tube, an inductor, and a first diode, wherein:

the first control end of the controller is used as the control end of the constant current power supply module, the second control end of the controller is connected with the control end of the second switch tube, the first end of the controller and the cathode of the first diode are connected to be used as the first end of the constant current power supply module, the first end of the second switch tube is respectively connected with the first end of the inductor and the anode of the first diode, the second end of the inductor is used as the third end of the constant current power supply module, and the second end of the second switch tube is used as the second end of the constant current power supply module.

3. The PWM dimming circuit according to claim 2, wherein the constant current power supply module further comprises:

and the first end of the resistor is connected with the first diode, and the second end of the resistor is respectively connected with the first end of the first light-emitting module and the detection end of the controller.

4. The PWM dimming circuit according to claim 3, further comprising a third switching tube and a second diode, wherein:

the second end of the third switching tube is connected with the cathode of the first diode, the first end of the third switching tube is connected with the first end of the first light-emitting module, the control end of the third switching tube is connected with the first control end of the controller, the cathode of the second diode is connected with the second end of the inductor, and the anode of the second diode is grounded.

5. The PWM dimming circuit according to claim 4, wherein the second switching tube is an NMOS tube, and the third switching tube and all the first switching tubes are PMOS tubes.

Images