CN201937925U - LED constant current driver with function of voltage reduction - Google Patents

Abstract

The utility model discloses an LED constant current driver with the function of decompression, which is arranged between a power supply and a load. The LED constant current driver with the function of voltage reduction is characterized by comprising a current limiting circuit, a voltage reduction control circuit, a frequency setting circuit and a constant current control circuit; an output end of the current limiting circuit is electrically connected with an input end of the voltage reduction control circuit; another input end of the voltage reduction control circuit is electrically connected with an output end of the frequency setting circuit; another input end of the voltage reduction control circuit is electrically connected with an output end of the constant current control circuit. The LED constant current driver can satisfy the requirements of expected brightness, can guarantee the coincidence of brightness and color of each LED, simultaneously can avoid that the drive current exceeds the maximal rated value, and has good reliability; and the LED constant current driver further has the advantages of reducing input voltage to the required voltage, improving the utilization rate of energy and the like.

Description

A LED constant current driver with step-down function

technical field

The utility model relates to an LED driver, in particular to an LED constant current driver with a step-down function.

Background technique

Since LED (Light Emitting Diode) is a semiconductor device with sensitive characteristics and has negative temperature characteristics, it is necessary to stabilize its working state in the application process, thus generating the concept of driving. LED devices have almost strict requirements on driving power. Unlike ordinary incandescent bulbs, LEDs can be directly connected to 220V AC. LED is driven by low voltage, so it is necessary to design a complex conversion circuit, and LED lights for different purposes need to be equipped with different power adapters. As customers have higher and higher requirements for efficiency conversion, effective power, constant current accuracy, power supply life, and electromagnetic compatibility of LED drive power supplies, these factors must be considered comprehensively when designing a good power supply, because the power supply plays an important role in the entire lamp. The function is as important as the human heart. Due to the discrete nature of LED volt-ampere characteristics, not only the volt-ampere characteristics of LEDs with the same wattage produced by different manufacturers are different, but also the volt-ampere characteristics of LEDs of the same type produced by the same manufacturer are also different. In the past, a constant voltage power supply was used for power supply. Obviously, the current flowing through each LED is different, and the brightness of each LED is also different. Therefore, a constant voltage power supply cannot be used for power supply. Although another LED driver is a constant current drive, it has no step-down function, and a large part of energy is wasted on the current-limiting resistor connected to the driven LED. Some have a step-down function, but do not use DC/DC step-down, and the energy utilization rate is very low. Therefore, it is necessary to develop a LED that can meet the expected brightness requirements and ensure the consistency of the brightness and chromaticity of each LED. At the same time, it can prevent the driving current from exceeding the maximum rated value and affect its reliability. In addition, it can also use DC/DC voltage conversion. A constant current driver with the advantages of stepping down the input voltage to the required voltage.

Contents of the invention

The purpose of this utility model is to provide a LED that can meet the expected brightness requirements and ensure the consistency of the brightness and chromaticity of each LED. At the same time, it can prevent the driving current from exceeding the maximum rated value and affect its reliability. A constant current driver with the advantages of pressing to the required voltage.

In order to achieve the above purpose, the technical solution adopted by the utility model is: an LED constant current driver with step-down function, which is connected between the power supply and the load, and is characterized in that it includes a current limiting circuit, a step-down control circuit, a frequency setting circuit and a constant current control circuit, the output end of the current limiting circuit is electrically connected to the input end of the step-down control circuit, the other input end of the step-down control circuit is electrically connected to the output end of the frequency setting circuit, and the step-down control circuit Another input end is electrically connected with the output end of the constant current control circuit.

Further technical solutions include:

The step-down control circuit is composed of IC chip MC34063, resistor R1, resistor R2, capacitor Co, inductor L, Schottky diode D1 and triode TR. The collector terminal of the SC switching tube is connected to the collector of the triode TR, and the other end of the resistor R1 is connected to the DRI collector drive terminal of the IC chip MC34063; the base of the triode TR is simultaneously connected to the emitter terminal of the SE switching tube of the IC chip MC34063 and the resistor R2 One end of the resistor R2 is connected to the ground; the emitter of the triode TR is connected to one end of the inductor L and the negative electrode of the Schottky diode D1 at the same time, and the other end of the inductor L is connected to one end of the capacitor Co and the positive electrode of the load at the same time , the anode of the Schottky diode D1 is connected to the ground; the other end of the capacitor Co is grounded.

The current limiting circuit is composed of a resistor Rsc, one end of the resistor Rsc is connected to the power supply and one end of the filter capacitor C1, and the other end of the resistor Rsc is electrically connected to the step-down control circuit.

The other end of the resistor Rsc is simultaneously electrically connected to an input end of the step-down control circuit and an IPK current detection end of the IC chip MC34063.

The frequency setting circuit is composed of a capacitor CT, one end of the capacitor CT is connected to the step-down control circuit, and the other end of the capacitor CT is grounded.

One end of the capacitor CT is connected to the TC timing capacitor end of the step-down control circuit IC chip MC34063.

The constant current control circuit is composed of a resistor R3, one end of the resistor R3 is connected to the step-down control circuit and the negative pole of the load at the same time, and the other end of the resistor R3 is grounded.

One end of the resistor R3 is connected to the inverting input end of the CII comparator of the MC34063 IC chip of the step-down control circuit.

The utility model can realize the constant current drive of the LED, ensure the consistency of the brightness and chromaticity of each connected LED, prevent the driving current from exceeding the maximum rated value, and also realize the protection of the battery to prevent the battery life from being caused by excessive discharge. It is shorter, has higher practical value, and has a simple structure, and the volume can be made small, which is convenient for direct assembly with the device.

Description of drawings

Fig. 1 is the schematic block diagram of the LED constant current driver with step-down function of the utility model;

Fig. 2 is a schematic circuit diagram of the LED constant current driver with step-down function of the present invention.

Detailed ways

Below in conjunction with the embodiment that accompanying drawing provides, the utility model is described in further detail. As shown in Figure 1 and Figure 2, the LED constant current driver with step-down function of the present invention includes a current limiting circuit 1, a step-down control circuit 2, a frequency setting circuit 3 and a constant current control circuit 4, the current limiting circuit The output end of the step-down control circuit is electrically connected to an input end of the step-down control circuit, the other input end of the step-down control circuit is electrically connected to the output end of the frequency setting circuit, and another input end of the step-down control circuit is connected to the output of the constant current control circuit terminal electrical connection.

In the above technical solution, as shown in FIG. 2, the step-down control circuit is composed of IC chip MC34063, resistors R1, R2, capacitor Co, inductor L, Schottky diode D1 and transistor TR. One end of the resistor R1 is connected to the output terminal of the current limiting circuit, the collector terminal of the SC switch tube of the IC chip MC34063 and the collector electrode of the triode TR, and the other end of the resistor R1 is connected to the DRI collector drive terminal of the IC chip MC34063; the triode TR The base of the transistor TR is connected to the emitter end of the SE switch tube of the IC chip MC34063 and one end of the resistor R2 at the same time, and the other end of the resistor R2 is connected to the ground; the emitter of the triode TR is connected to one end of the inductor L and the negative electrode of the Schottky diode D1 at the same time , the other end of the inductor L is connected to one end of the capacitor Co and the anode of the load at the same time, the anode of the Schottky diode D1 is connected to the ground; the other end of the capacitor Co is connected to the ground.

The current limiting circuit is composed of a resistor Rsc, one end of the resistor Rsc is connected to the power supply and one end of the filter capacitor C1 at the same time, and the other end of the resistor Rsc is electrically connected to an input end of the step-down control circuit and the IPK current detection end of the IC chip MC34063 .

The frequency setting circuit is composed of a capacitor CT, one end of the capacitor CT is connected to the TC timing capacitor end of the IC chip MC34063, and the other end of the capacitor CT is connected to the ground.

The constant current control circuit is composed of a resistor R3, one end of the resistor R3 is connected to the inverting input end of the CII comparator of the IC chip MC34063 and the negative pole of the load, and the other end of the resistor R3 is connected to the ground.

When the utility model is used, one way of the power supply is directly connected to the Vcc chip power supply terminal of the IC chip MC34063, and the other way is input to the IPK current detection terminal of the IC chip MC34063, the collector electrode of the drive internal switch tube and the current limiter of the other way through the current limiting resistor Rsc. The collector of the triode TR is also input to the collector of the drive tube through the resistor R1; when the whole circuit is working, the triode TR is in a state of continuous on and off, when TR is on, the Schottky diode D1 is off, and the power supply Charge the inductor, and the capacitor Co provides energy to the load at this time. When TR is cut off, the Schottky diode D1 is turned on, and the inductance provides energy to the capacitor Co and the load at this time. The required constant current can be obtained between the positive output terminal and the inverting input terminal of the CII comparator of the chip MC34063, and the magnitude of the current can be realized by adjusting the size of the resistor R3 as required. When the LED load changes, it will be fed back to the CII terminal of the chip through R3, and then the voltage conversion module can be adjusted to change the output voltage, so as to achieve the purpose of constant current. In addition, the operating frequency of the circuit can be set by changing the size of the capacitor CT.

The utility model has been disclosed above with preferred embodiments, but it is not intended to limit the utility model, and all technical solutions obtained by adopting equivalent replacement or equivalent transformation methods fall within the protection scope of the utility model.

Claims (8)

1. An LED constant current driver with step-down function, which is set between the power supply and the load, and is characterized in that it includes a current limiting circuit (1), a step-down control circuit (2), a frequency setting circuit (3) and a constant current driver. A current control circuit (4), the output end of the current limiting circuit (1) is electrically connected to the input end of the step-down control circuit (2), and the other input end of the step-down control circuit (2) is connected to the frequency setting circuit (3 ) is electrically connected to the output end of the step-down control circuit (2), and another input end of the step-down control circuit (2) is electrically connected to the output end of the constant current control circuit (4). 2. The LED constant current driver with step-down function according to claim 1, characterized in that: the step-down control circuit (2) consists of IC chip MC34063, resistor R1, resistor R2, capacitor Co, inductor L, Xiao The base diode D1 and the triode TR are composed, one end of the resistor R1 is connected with the output end of the current limiting circuit (1), the collector end of the SC switching tube of the IC chip MC34063 and the collector electrode of the triode TR, and the other end of the resistor R1 is connected with the IC The DRI collector drive terminal of the chip MC34063 is connected; the base of the triode TR is connected with the emitter terminal of the SE switch tube of the IC chip MC34063 and one end of the resistor R2 at the same time, and the other end of the resistor R2 is connected with the ground; the emitter of the triode TR is connected with the inductor at the same time One end of L is connected to the negative pole of the Schottky diode D1, the other end of the inductor L is connected to one end of the capacitor Co and the positive pole of the load, the positive pole of the Schottky diode D1 is connected to the ground; the other end of the capacitor Co is grounded. 3. The LED constant current driver with step-down function according to claim 1 or 2, characterized in that: the current limiting circuit (1) is composed of a resistor Rsc, one end of the resistor Rsc is connected to the power supply and the filter capacitor C1 at the same time One end is connected, and the other end of the resistor Rsc is electrically connected to the step-down control circuit (2). 4. The LED constant current driver with step-down function according to claim 3, characterized in that: the other end of the resistor Rsc is simultaneously connected to an input end of the step-down control circuit (2) and the IPK current detection end of the IC chip MC34063 electrical connection. 5. The LED constant current driver with step-down function according to claim 1 or 2, characterized in that: the frequency setting circuit (3) is composed of a capacitor CT, and one end of the capacitor CT is connected to the step-down control circuit (2) , the other end of the capacitor CT is grounded. 6. The LED constant current driver with step-down function according to claim 5, wherein one end of the capacitor CT is connected to the TC timing capacitor end of the step-down control circuit (2) IC chip MC34063. 7. The LED constant current driver with step-down function according to claim 1 or 2, characterized in that: the constant current control circuit (4) is composed of a resistor R3, and one end of the resistor R3 is simultaneously connected with the step-down control circuit ( 2) Connect to the negative pole of the load, and the other end of the resistor R3 is grounded. 8. The LED constant current driver with step-down function according to claim 7, characterized in that: one end of the resistor R3 is connected to the inverting input end of the CII comparator of the MC34063 IC chip of the step-down control circuit (2).

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