CN204465954U - A LED lamp driving circuit with dimming function - Google Patents

Abstract

The utility model discloses a kind of LED lamp drive circuit with dimming function, comprise gray value Acquisition Circuit, STC89C51 single-chip microcomputer, power circuit and control circuit, described power circuit comprises rectifier bridge T, transformer W and electric capacity C1, and described control circuit comprises amplifier IC2, amplifier IC3 and metal-oxide-semiconductor Q2.The utility model LED drive circuit controls using single-end flyback switching power supply as prime, and linear pressure-controlled constant-current source is as the rear class controlled.Make constant-current source accurately at the input voltage changing its constant-current source in a big way, efficiency and precision can be improve while control LED, meanwhile, the not fragile LED of two-step evolution, therefore this circuit have that efficiency is high, stable performance, long service life advantage.

Description

A LED lamp driving circuit with dimming function

technical field

The utility model relates to an LED circuit, in particular to an LED lamp driving circuit with dimming function.

Background technique

LED is recognized as the fourth-generation green light source. It is a solid cold light source with many advantages such as high efficiency, long life, safety and environmental protection, small size, high reliability, and fast response. At present, to achieve the same lighting effect, the power consumption of LED is about 1/10 of incandescent lamp and 1/2 of fluorescent lamp. LED drive circuit is very important for LED, and LED dimming control can save energy. High-brightness white LED The driving and dimming of LEDs are research hotspots in recent years. Most traditional LED drive circuits use switching power supply control. The actual feedback control of the switching power supply is the output voltage. It is not easy to achieve accurate output current control, and the simple switching power supply control has It is easy to damage the LED lamp when it deviates, and the efficiency of the linear circuit is not high.

Utility model content

The purpose of the utility model is to provide a high-efficiency, stable-performance LED lamp driving circuit with a dimming function, so as to solve the problems raised in the above-mentioned background technology.

In order to achieve the above object, the utility model provides the following technical solutions:

An LED lamp driving circuit with a dimming function, comprising a grayscale value acquisition circuit, a STC89C51 single-chip microcomputer, a power supply circuit and a control circuit, the power supply circuit comprising a rectifier bridge T, a transformer W and a capacitor C1, and the control circuit comprising an amplifier IC2, amplifier IC3 and MOS tube Q2;

Port 1 and port 3 of the rectifier bridge T are respectively connected to both ends of the 220V AC, port 2 of the rectifier bridge T is connected to the capacitor C1 and the winding L1 of the transformer W, and port 2 of the rectifier bridge T is connected to the other end of the capacitor C1 and the MOS tube The source of Q1 and the drain of MOS transistor Q1 are connected to the other end of the winding L1 of the transformer W, the gate of the MOS transistor Q1 is connected to the output end of the isolation drive circuit, one end of the winding L2 of the transformer W is connected to the anode of the diode D1, and the diode D1 The cathode of the capacitor C2 is connected to the LED lamp H, the other end of the capacitor C2 is connected to the capacitor C3, the other end of the winding L2 of the transformer W and the winding L3 of the transformer W, the other end of the winding L3 of the transformer W is connected to the anode of the diode D2, and the diode D2 The cathode is connected to the other end of resistor R1, resistor R2 and capacitor C3, the other end of resistor R2 is connected to pin 1 of the three-terminal adjustable reference source P and pin 1 of AND gate chip IC1, and pin 2 of AND gate chip IC1 is connected to STC89C51 microcontroller Pin P1.3 of the AND gate chip IC1 is connected to the input end of the isolation drive circuit, pin 2 of the three-terminal adjustable reference source P is connected to resistor R3 and grounded, and pin 3 of the three-terminal adjustable reference source P is connected to the resistor The other end of R1 and the other end of resistor R3, the P3.2 pin of the STC89C51 single-chip microcomputer is connected to the gray value acquisition circuit, the P1.0 pin of the STC89C51 single-chip microcomputer is connected to the resistor R6, the other end of the resistor R6 is connected to the capacitor C4, and the other end of the capacitor C4 Connect resistors R7, R9~R12 and capacitor C5 and ground, the other end of resistor R10 is connected to resistor R4, resistor R5, pin 3 of amplifier IC3 and pin P3.3 of STC89C51 microcontroller, and the other end of resistor R4 is connected to pin 1 of amplifier IC2 , the other end of resistor R4 is connected to pin 1 of amplifier IC3 and the other end of resistor R7, pin 2 of amplifier IC3 is connected to the other end of capacitor C5 and resistor R8, the other end of resistor R9 is connected to pin 2 of amplifier IC2, and pin 3 of amplifier IC2 The other end of the resistor R11 is connected to the gate of the MOS transistor Q2, the other end of the resistor R8 is connected to the source of the MOS transistor Q2 and the other end of the resistor R12, and the drain of the MOS transistor Q2 is connected to the other end of the LED lamp H.

As a preferred solution of the utility model: the models of the amplifiers IC2 and IC3 are both LM311.

As a preferred solution of the utility model: the isolated drive circuit is an isolated drive module centered on a 4N25 optocoupler.

Compared with the prior art, the utility model has the beneficial effects that: the utility model LED drive circuit uses a single-ended flyback switching power supply as the front stage control, and a linear voltage control constant current source as the control stage. The constant current source can precisely control the LED while changing the input voltage of the constant current source in a wide range, which improves the efficiency and precision. At the same time, the two-level control is not easy to damage the LED lamp, so this circuit has high efficiency, stable performance, and is easy to use. The advantage of long life.

Description of drawings

Fig. 1 is a circuit diagram of an LED lamp driving circuit with dimming function;

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. example. 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.

Please refer to Figure 1, a LED lamp driving circuit with dimming function, including a gray value acquisition circuit, STC89C51 single-chip microcomputer, power supply circuit and control circuit, the power supply circuit includes a rectifier bridge T, a transformer W and a capacitor C1, so Said control circuit comprises amplifier IC2, amplifier IC3 and MOS tube Q2;

Port 1 and port 3 of the rectifier bridge T are respectively connected to both ends of the 220V AC, port 2 of the rectifier bridge T is connected to the capacitor C1 and the winding L1 of the transformer W, and port 2 of the rectifier bridge T is connected to the other end of the capacitor C1 and the MOS tube The source of Q1 and the drain of MOS transistor Q1 are connected to the other end of the winding L1 of the transformer W, the gate of the MOS transistor Q1 is connected to the output end of the isolation drive circuit, one end of the winding L2 of the transformer W is connected to the anode of the diode D1, and the diode D1 The cathode of the capacitor C2 is connected to the LED lamp H, the other end of the capacitor C2 is connected to the capacitor C3, the other end of the winding L2 of the transformer W and the winding L3 of the transformer W, the other end of the winding L3 of the transformer W is connected to the anode of the diode D2, and the diode D2 The cathode is connected to the other end of resistor R1, resistor R2 and capacitor C3, the other end of resistor R2 is connected to pin 1 of the three-terminal adjustable reference source P and pin 1 of AND gate chip IC1, and pin 2 of AND gate chip IC1 is connected to STC89C51 microcontroller Pin P1.3 of the AND gate chip IC1 is connected to the input terminal of the isolation drive circuit, pin 2 of the three-terminal adjustable reference source P is connected to resistor R3 and grounded, and pin 3 of the three-terminal adjustable reference source P is connected to resistor R1 The other end of the resistor R3 and the other end of the resistor R3, the P3.2 pin of the STC89C51 microcontroller is connected to the gray value acquisition circuit, the P1.0 pin of the STC89C51 microcontroller is connected to the resistor R6, the other end of the resistor R6 is connected to the capacitor C4, and the other end of the capacitor C4 is connected to Resistors R7, R9~R12 and capacitor C5 are connected to ground, the other end of resistor R10 is connected to resistor R4, resistor R5, pin 3 of amplifier IC3 and pin P3.3 of STC89C51 microcontroller, and the other end of resistor R4 is connected to pin 1 of amplifier IC2. The other end of resistor R4 is connected to pin 1 of amplifier IC3 and the other end of resistor R7, pin 2 of amplifier IC3 is connected to the other end of capacitor C5 and resistor R8, the other end of resistor R9 is connected to pin 2 of amplifier IC2, and pin 3 of amplifier IC2 The other end of the resistor R11 is connected to the gate of the MOS transistor Q2, the other end of the resistor R8 is connected to the source of the MOS transistor Q2 and the other end of the resistor R12, and the drain of the MOS transistor Q2 is connected to the other end of the LED lamp H.

Amplifiers IC2 and IC3 are both LM311.

The isolated drive circuit is an isolated drive module centered on a 4N25 optocoupler.

The working principle of the utility model is: transformer W, MOS tube Q1, diode D1 and capacitor C1 form a single-ended flyback switching power supply in Figure 1; devices such as amplifier IC2, IC3 and power tube Q2 form a voltage-controlled constant current source; STC89C51 The single chip microcomputer is the core control device. When the gray value changes, the microcontroller generates a corresponding brightness control voltage according to the obtained gray value. Brightness control voltage is added to pin 1 of IC2, pin 2 of IC2 is the current signal flowing through the LED lamp obtained by IC3, and R12 is the current detection resistor. The output voltage of pin 3 of IC2 is the control voltage of MOS tube Q2. According to the concept of virtual short of the operational amplifier, the reverse input voltage of IC2 must be equal to the voltage on its positive input terminal, that is, the current on R12 is controlled by the brightness when it is stable. The control of the control voltage does not change with the change of the load. The single-chip microcomputer generates a corresponding brightness control voltage according to the gray value obtained by it, and at the same time generates a PWM signal output by P1.3, and the PWM signal meets the signal on the three-terminal adjustable reference source P to control the MOS transistor Q1 Then the MCU changes the duty cycle of the PWM signal according to the obtained LED current signal, and changes the output voltage of the switching power supply, that is, changes the input voltage of the constant current source to reduce the voltage on the power transistor Q2, so that it can reduce the voltage on the power tube Q2 when the output current is not constant. Work in the adjustable resistance area or close to the adjustable resistance area to improve efficiency. The existence of the three-terminal adjustable shunt reference P and its corresponding electric phase here is to limit the maximum output voltage of the switching power supply and further improve the safety of the system. When the light is relatively good, the single-chip microcomputer controls the output brightness control voltage according to the obtained gray value, so that the output current of the constant current source is relatively small, which can achieve energy saving effect. The circuit uses a single-ended flyback switching power supply as the pre-stage control, and a linear voltage-controlled constant current source as the post-stage control. After the city power is converted by a single-ended flyback power supply, a DC voltage output can be obtained, and this output is used as the input of the voltage-controlled constant-current source of the subsequent stage. Since the input voltage of the voltage-controlled constant-current source is powered by a high-efficiency single-flyback switching power supply, the voltage-controlled constant-current source can precisely control the LED while changing the input voltage of its constant-current source in a wide range, so the efficiency and accuracy are both Guaranteed and mains ready. At the same time, the two-level control is not easy to damage the LED light.

Claims (3)

1., with a LED lamp drive circuit for dimming function, comprise gray value Acquisition Circuit, STC89C51 single-chip microcomputer, power circuit and control circuit; It is characterized in that, described power circuit comprises rectifier bridge T, transformer W and electric capacity C1, and described control circuit comprises amplifier IC2, amplifier IC3 and metal-oxide-semiconductor Q2;

1 port and 3 ports of described rectifier bridge T are connected the two ends of 220V alternating current respectively, 2 ports of rectifier bridge T connect the winding L 1 of electric capacity C1 and transformer W, 2 ports of rectifier bridge T connect the other end of electric capacity C1 and the source electrode of metal-oxide-semiconductor Q1, the other end of the winding L 1 of the drain electrode connection transformer W of metal-oxide-semiconductor Q1, the grid of metal-oxide-semiconductor Q1 connects the output of isolated drive circuit, one end of the winding L 2 of transformer W connects the anode of diode D1, the negative electrode of diode D1 connects electric capacity C2 and LED lamp H, the other end of electric capacity C2 connects electric capacity C3, the other end of the winding L 2 of transformer W and the winding L 3 of transformer W, the other end of the winding L 3 of transformer W connects the anode of diode D2, the negative electrode contact resistance R1 of diode D2, the other end of resistance R2 and electric capacity C3, the other end of resistance R2 connects 1 pin of three end adjustable reference source P and 1 pin with door chip IC 1, the P1.3 pin of STC89C51 single-chip microcomputer is connected with 2 pin of door chip IC 1, the input of isolated drive circuit is connected with 3 pin of door chip IC 1, the 2 pin contact resistance R3 of three end adjustable reference source P ground connection, the other end of 3 pin contact resistance R1 of three end adjustable reference source P and the other end of resistance R3, the P3.2 pin of STC89C51 single-chip microcomputer connects gray value Acquisition Circuit, the P1.0 pin contact resistance R6 of STC89C51 single-chip microcomputer, the other end of resistance R6 connects electric capacity C4, the other end contact resistance R7 of electric capacity C4, R9 ~ R12 and electric capacity C5 ground connection, the other end contact resistance R4 of resistance R10, resistance R5, 3 pin of amplifier IC3 and the P3.3 pin of STC89C51 single-chip microcomputer, the other end of resistance R4 connects 1 pin of amplifier IC2, the other end of resistance R4 connects 1 pin of amplifier IC3 and the other end of resistance R7, 2 pin of amplifier IC3 connect the other end and the resistance R8 of electric capacity C5, the other end of resistance R9 connects 2 pin of amplifier IC2, the other end of 3 pin contact resistance R11 of amplifier IC2 and the grid of metal-oxide-semiconductor Q2, the other end of resistance R8 connects the source electrode of metal-oxide-semiconductor Q2 and the other end of resistance R12, the drain electrode of metal-oxide-semiconductor Q2 connects the other end of LED lamp H.

2. a kind of LED lamp drive circuit with dimming function according to claim 1, is characterized in that, the model of described amplifier IC2 and IC3 is LM311.

3. a kind of LED lamp drive circuit with dimming function according to claim 1, is characterized in that, described isolated drive circuit is the isolation drive module centered by 4N25 optical coupler.