CN203136242U - LED constant-current circuit with PWM light modulation - Google Patents

Abstract

The utility model provides an LED constant current circuit with PWM dimming, comprising a power supply, a self-controlled constant current circuit, an LED lamp string and a PWM dimming module; the LED lamp string is connected in series with the self-controlled constant current circuit, and the The self-controlled constant current circuit provides a constant current for the LED light string, and the circuit load composed of the LED light string and the self-controlled constant current circuit is connected between the positive pole and the negative pole of the power supply. The self-controlled constant current circuit includes a voltage detection control circuit and A constant current circuit, the PWM dimming module is connected with the self-control constant current circuit, the PWM dimming module provides a port that can receive a PWM signal, and the constant current circuit is controlled by the PWM signal.

Description

A LED constant current circuit with PWM dimming

technical field

The utility model relates to the design field of LED lighting lamp drive circuits, in particular to an LED constant current circuit with PWM dimming.

Background technique

Light-emitting diode (LED) solid-state light source has the advantages of high luminous efficiency, environmental protection, and long life, and is known as the fifth-generation lighting source. Due to the high efficiency and good energy-saving effect of LED lamps, LED lamps have gradually replaced white light lamps, and LED lamps have begun to mature. At present, in order to obtain LED lamps with different color temperatures and different intensities, people have also done a lot of research in this regard.

There are mainly two ways to realize dimming in the prior art:

One: The dimming effect is realized by adjusting or fine-tuning the resistor. By changing the effective resistance value of the adjustable or fine-tuning resistor, the driving voltage of the LED lamp is increased or decreased, thereby achieving the effect of increasing or reducing the luminous intensity of the LED lamp. Effect. The disadvantage of this adjustment of luminous intensity is: since the adjustable range of the adjustable or fine-tuned resistor is limited, the flexibility of adjusting the brightness is obviously limited; further, if other button functions need to be integrated, other buttons must be added. Buttons, which not only take up space, but also extremely inconvenient to operate.

Second: the effect of dimming is achieved by adjusting the current changes at both ends of the LED lamp. This method is generally controlled by a single-chip microcomputer chip, and each pixel needs a controllable current source. The disadvantage of this adjustment of luminous intensity is that the circuit is extremely complex, resulting in very high design costs and maintenance costs.

In summary, there are still many deficiencies in the prior art, which need to be further improved and enhanced.

Utility model content

The purpose of the utility model is to solve the problems in the prior art, especially the problems of small dimming range and complex circuit in the prior art.

In order to achieve the above object, the utility model is realized by adopting the following technical solutions:

1. An LED constant current circuit with PWM dimming, characterized in that: it includes a power supply, a self-controlled constant current circuit, an LED light string and a PWM dimming module; the LED light string is connected in series with the self-controlled constant current circuit, so The circuit load composed of the LED lamp string and the self-controlled constant current circuit is connected between the positive pole and the negative pole of the power supply, and the PWM dimming module is connected with the self-controlled constant current circuit.

2. The LED constant current circuit with PWM dimming according to claim 1, characterized in that: the self-controlled constant current circuit includes a voltage detection control circuit and a constant current circuit; the voltage detection control circuit includes a voltage detection A control circuit triode, a first voltage dividing resistor and a second voltage dividing resistor; the constant current circuit includes a constant current circuit MOS tube, a current limiting resistor, a current detection resistor and a constant current circuit triode;

One end of the first voltage dividing resistor and one end of the second voltage dividing resistor are connected to the base of the voltage detection control circuit triode at the same time, the other end of the first voltage dividing resistor is connected to the negative end of the LED light string, and the second voltage dividing resistor The other end is connected to the negative pole of the power supply, the collector of the triode of the voltage detection control circuit is connected to the gate of the MOS transistor of the constant current circuit, and the emitter of the triode of the voltage detection control circuit is connected to the negative pole of the power supply;

The drain of the constant current circuit MOS tube and one end of the current limiting resistor are connected to the negative end of the LED light string, the source of the constant current circuit MOS tube and one end of the current detection resistor are connected to the base of the constant current circuit triode at the same time, the constant current circuit MOS The gate of the tube is simultaneously connected to the other end of the current limiting resistor, the collector of the voltage detection control circuit transistor and the collector of the constant current circuit transistor;

The other end of the current limiting resistor is connected to the collector of the transistor of the constant current circuit and the collector of the transistor of the voltage detection control circuit, and the other end of the current detection resistor and the emitter of the transistor of the constant current circuit are connected to the negative pole of the power supply.

3. The LED constant current circuit with PWM dimming according to claim 2, wherein the PWM dimming module is provided with a PWM dimming port, and the PWM dimming port is connected to the first voltage dividing resistor , the second voltage dividing resistor and the base of the voltage detection control circuit triode are connected to each other.

Compared with the prior art, the utility model provides an LED constant current circuit with PWM dimming function. The LED constant current circuit includes an LED lamp string, a self-controlled constant current circuit, and a PWM dimming module. The utility model solves the problems of high cost of traditional LED constant current drive, complex dimming circuit and small dimming range.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present utility model. Those skilled in the art can also obtain other drawings based on these drawings without any creative work.

Fig. 1 is a specific circuit diagram of an embodiment provided by the utility model.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the utility model clearer, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the embodiments of the utility model and the accompanying drawings. It should be noted that the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Example

The specific embodiment of the utility model is described below in conjunction with accompanying drawing.

As shown in Figure 1, the LED constant current circuit with PWM dimming provided by this embodiment includes a power supply, a self-controlled constant current circuit, an LED light string and a PWM dimming module; the LED light string and the self-controlled constant current circuit connected in series, the circuit load composed of the LED light string and the self-controlled constant current circuit is connected between the positive pole and the negative pole of the power supply, and the PWM dimming module is connected with the self-controlled constant current circuit.

The self-controlled constant current circuit includes a voltage detection control circuit and a constant current circuit.

The voltage detection control circuit includes a voltage detection control circuit transistor V2, a first voltage divider resistor R1 and a second voltage divider resistor R3, one end of the two voltage divider resistors is simultaneously connected to the base of the voltage detection control circuit transistor V2, and the first divider The other end of the piezoresistor R1 is connected to the negative end of the LED light string, the other end of the second voltage dividing resistor R3 is connected to the negative electrode of the power supply, the collector of the voltage detection control circuit triode V2 is connected to the gate of the constant current circuit MOS transistor V1, The emitter of the voltage detection control circuit triode V2 is connected to the negative pole of the power supply.

The constant current circuit includes a constant current circuit MOS transistor V1, a current limiting resistor R2, a current detection resistor R4 and a constant current circuit transistor V3.

The drain of the constant current circuit MOS tube V1 and one end of the current limiting resistor R2 are connected to the negative end of the LED light string; the source of the constant current circuit MOS tube V1 and one end of the current detection resistor R4 are simultaneously connected to the base of the constant current circuit triode V3 ; The gate of the constant current circuit MOS transistor V1 is simultaneously connected to the other end of the first current limiting resistor R2, the collector of the voltage detection control circuit transistor V2 and the collector of the constant current circuit transistor V3.

The other end of the current limiting resistor R2 is connected to the collector of the transistor V3 of the constant current circuit and the collector of the transistor V2 of the voltage detection control circuit; the other end of the current detection resistor R4 and the emitter of the transistor V3 of the constant current circuit are connected to the negative pole of the power supply,

The PWM dimming module is provided with a PWM dimming port, and the PWM dimming port is connected to the junction of the first voltage dividing resistor, the second voltage dividing resistor and the base of the voltage detection control circuit triode. The PWM dimming port receives the PWM dimming signal sent from the outside, and adds the PWM dimming signal to the first voltage dividing resistor and the second voltage dividing resistor to control the turn-on and turn-off of the voltage detection control transistor.

The PWM dimming port can receive the PWM dimming signal sent from the outside, the PWM dimming signal can be directly connected to the base of the voltage detection control circuit transistor V2, or the PWM dimming signal can be connected to the main circuit through the optocoupler After isolation, it is sent to the base of the voltage detection control circuit transistor V2, and the PWM signal controls the on and off of the voltage detection control circuit transistor V2 through the voltage division on the second voltage divider resistor R3.

The self-controlled constant current circuit itself controls the on and off of the voltage detection control circuit triode V2 by controlling the current flowing through the current detection resistor R4 and then divides the voltage, so that the MOS transistor V1 flowing through the constant current circuit current to achieve a constant purpose. The transistor V2 of the voltage detection control circuit is directly connected to the gate of the MOS transistor V1 of the constant current circuit. The conduction and shutdown of the transistor V2 of the voltage detection control circuit can directly control the conduction and shutdown of the MOS transistor V1 of the constant current circuit, thereby controlling the current flow. Through the current of the constant current circuit MOS tube V1, the LED light string and the constant current circuit MOS tube V1 are connected in series, and the current flowing through the LED light string and the constant current circuit MOS tube V1 is equal, by adjusting the duty cycle of the PWM dimming signal , and then can control the magnitude of the current flowing through the MOS transistor V1 of the constant current circuit, thereby controlling the magnitude of the current flowing through the LED light string, and realizing the purpose of LED dimming.

It should be noted that, in the self-controlled constant current circuit in this embodiment, all transistors in the voltage detection control circuit can be replaced by MOS transistors, and the MOS transistors in the constant current circuit can be replaced by triodes.

An LED constant current circuit with PWM dimming function provided in this embodiment, the LED constant current circuit includes an LED lamp string, a self-controlled constant current circuit, and a PWM dimming module, only by changing the components and components in the circuit The connection method does not require additional setting of other buttons to realize the function, which solves the problems of high cost of traditional LED constant current drive, complex dimming circuit, and small dimming range. And the circuit has its own overvoltage and overcurrent protection functions, which can detect that when the voltage at both ends of the LED light string rises, the branch will be turned off, which can protect the LED light source from being burned out by overvoltage; this embodiment uses PWM regulation The optical module adjusts the brightness of the LED light string by receiving the external PWM dimming signal, so that the dimming range of the circuit is wide, and the dimming is stable and reliable.

The above-mentioned embodiments only express several implementations of the utility model, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the patent scope of the utility model. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the utility model patent should be based on the appended claims.

Claims (3)

1. the LED constant-current circuit with the PWM light modulation is characterized in that: comprise power supply, automatic control constant-current circuit, LED lamp string and PWM light-adjusting module; Described LED lamp string is connected with described automatic control constant-current circuit, and the circuit load that described LED lamp string and automatic control constant-current circuit are formed is connected between the positive pole and negative pole of power supply, and described PWM light-adjusting module is connected with the automatic control constant-current circuit.

2. the LED constant-current circuit of band according to claim 1 PWM light modulation, it is characterized in that: described automatic control constant-current circuit comprises a voltage detecting and controling circuit and a constant-current circuit; Described voltage detecting and controling circuit comprises voltage detecting and controling circuit triode, first divider resistance and second divider resistance; Described constant-current circuit comprises constant-current circuit metal-oxide-semiconductor, a current-limiting resistance, a current sense resistor and a constant-current circuit triode;

One end of first divider resistance and an end of second divider resistance are connected the base stage of voltage detecting and controling circuit triode simultaneously, the other end of first divider resistance connects the negative terminal of described LED lamp string, the other end of second divider resistance connects the negative pole of power supply, the collector electrode of voltage detecting and controling circuit triode connects the grid of constant-current circuit metal-oxide-semiconductor, and the emitter of voltage detecting and controling circuit triode connects the negative pole of power supply;

One end of the drain electrode of constant-current circuit metal-oxide-semiconductor and current-limiting resistance is connected the negative terminal of LED lamp string, one end of the source electrode of constant-current circuit metal-oxide-semiconductor and current sense resistor is connected the base stage of constant-current circuit triode simultaneously, and the grid of constant-current circuit metal-oxide-semiconductor connects the other end of current-limiting resistance, the collector electrode of voltage detecting and controling circuit triode and the collector electrode of constant-current circuit triode simultaneously;

The other end of current-limiting resistance connects the collector electrode of constant-current circuit triode and the collector electrode of voltage detecting and controling circuit triode, and the emitter of the other end of current sense resistor and constant-current circuit triode all is connected to the negative pole of power supply.

3. the LED constant-current circuit of band according to claim 2 PWM light modulation, it is characterized in that: described PWM light-adjusting module is provided with PWM light modulation port, and described PWM light modulation port is connected with described first divider resistance, second divider resistance and the base stage three's of voltage detecting and controling circuit triode junction.