CN203523099U - LED driving circuit - Google Patents

Abstract

The utility model discloses an LED driving circuit. The LED driving circuit includes an alternate current power supply input rectification and electromagnetic interference circuit, a control circuit, a voltage reducing circuit and a filtering circuit, wherein an input terminal of the alternate current power supply input rectification and electromagnetic interference circuit is connected with an alternate current power supply, and an output terminal of the alternate current power supply input rectification and electromagnetic interference circuit is connected with an input terminal of the voltage reducing circuit, an input terminal of the control circuit, and an input terminal of the filtering circuit; one input terminal of the control circuit is connected with the output terminal of the alternate current power supply input rectification and electromagnetic interference circuit, the other input terminal of the control circuit is connected with an output terminal of the voltage reducing circuit, and an output terminal of the control circuit is connected with a reference ground; an input terminal of the voltage reducing output circuit is connected with the output terminal of the alternate current power supply input rectification and electromagnetic interference circuit, one output terminal of the voltage reducing output circuit is connected with the other input terminal of the control circuit, and the other output terminal is connected with a load; and an input terminal of the filtering circuit is connected with the output terminal of the alternate current power supply input rectification and electromagnetic interference circuit, and an output terminal of the filtering circuit is connected with the reference ground. The LED driving circuit has advantages of being high in current accuracy, being high in conversion efficiency, and being rapid to start.

Description

LED drive circuit

technical field

The utility model relates to the field of circuits, in particular to an LED driving circuit.

Background technique

At present, the light-emitting diode (LED) technology has become more and more mature, and because of its high luminous efficiency and long service life, it is urgent to replace the traditional incandescent lamp in the lighting field. However, in the existing switching power supply solutions for low-power LEDs such as lamp cups and lamp tubes, there are generally disadvantages such as low current accuracy, low conversion efficiency, and large printed board size. Because the low current precision will affect the service life of the LED, and the low conversion efficiency will increase the calorific value. Therefore, a new type of LED driving circuit is currently required to solve the above problems.

Utility model content

In view of one or more problems mentioned above, the utility model provides a new type of LED driving circuit.

The LED drive circuit according to the embodiment of the utility model includes an AC power input rectification and electromagnetic interference circuit, a control circuit, a step-down output circuit and a filter circuit, wherein: the input terminal of the AC power input rectification and electromagnetic interference circuit is connected to the AC power supply , the output terminals are respectively connected to the input terminal of the step-down output circuit, the input terminal of the control circuit and the input terminal of the filter circuit; one input terminal of the control circuit is connected to the output terminal of the AC power input rectification and electromagnetic interference circuit, and the other The input terminal is connected to one output terminal of the step-down output circuit, and the output terminal is connected to the reference ground; the input terminal of the step-down output circuit is connected to the output terminal of the AC power input rectification and electromagnetic interference circuit, and one output terminal is connected to the control circuit The other input terminal is connected to the other input terminal, and the other output terminal is connected to the load; the input terminal of the filter circuit is connected to the output terminal of the AC power input rectification and electromagnetic interference circuit, and the output terminal is connected to the reference ground.

The LED driving circuit according to the embodiment of the utility model has the advantages of high current precision, high conversion efficiency and quick start.

Description of drawings

Can understand the utility model better from the following in conjunction with accompanying drawing to the description of the specific embodiment of the utility model, wherein:

Fig. 1 shows a circuit diagram of an LED driving circuit according to an embodiment of the present invention;

Fig. 2 shows the connection circuit of the filter circuit 4 at two points A and B according to the embodiment of the present invention.

Detailed ways

Features and exemplary embodiments of various aspects of the present invention will be described in detail below. The following description covers numerous specific details in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a clearer understanding of the present invention by showing examples of the present invention. The utility model is by no means limited to any specific configuration proposed below, but covers any modification, substitution and improvement of related elements or components without departing from the spirit of the utility model.

The LED drive circuit according to the embodiment of the utility model is developed based on a switch circuit with a step-down structure. The LED driving circuit according to the embodiment of the present utility model will be described in detail below with reference to FIG. 1 and FIG. 2 .

Fig. 1 shows a circuit diagram of an LED driving circuit according to an embodiment of the present invention. As shown in FIG. 1 , the LED driving circuit includes: an alternating current (AC) input rectification and electromagnetic interference (EMI) circuit 1 , a control circuit 2 , a step-down output circuit 3 and a filter circuit 4 .

Wherein, the input end of the AC input rectification and EMI circuit 1 is connected with the AC power supply, and the output end is respectively connected with the input end of the step-down output circuit 3, the input end of the control circuit 2 and the input end of the filter circuit 4; the control circuit 2 One input end of AC input rectifier and the output end of EMI circuit 1 are connected, the other input end is connected with an output end of step-down output circuit 3, and the output end is connected with reference ground; the input of step-down output circuit 3 The terminal is connected with the output terminal of the AC input rectification and EMI circuit 1, one output terminal is connected with the above-mentioned other input terminal of the control circuit 2, and the other output terminal is connected with the load; the input terminal of the filter circuit 4 is connected with the AC input rectification terminal It is connected with the output end of the EMI circuit 1, and the output end is connected with the reference ground.

Through the above-mentioned LED driving circuit, the problems of short service life of LEDs caused by low current precision and high heat generation caused by low conversion efficiency of LEDs in the prior art can be overcome.

As shown in Figure 1, the AC input rectification and EMI circuit 1 includes: a fuse (FUSE), a varistor (MOV), a common mode filter inductor L1, X capacitors CX1, CX2 and a rectifier bridge (BD1).

The control circuit 2 includes: a control chip (U1), a resistor R1, a resistor R3, and a capacitor C1, wherein the resistor R1 and the resistor R2 are connected in series between the control chip U1 and the AC input rectifier and the output of the EMI circuit 1 Between, the resistor R3 and the capacitor C1 are respectively connected between the control chip and the reference ground.

The step-down output circuit 3 includes: a step-down inductor L2, a freewheeling diode D1, a filter capacitor C2 and an output dummy load R4. Among them, the filter capacitor C2, the output dummy load R4 and the load (LED light string) are connected in parallel, one end of the step-down inductor L2 is connected to the other input end of the control circuit 2, and the other end is respectively connected to the filter capacitor C2, output The dummy load R4 is connected to the load (LED light string); the anode of the freewheeling diode D1 is respectively connected to the other input end of the control circuit 2 and one end of the step-down inductor L2, and the cathode is respectively connected to the AC input rectification and EMI circuit The output terminal, the filter capacitor C2, the output dummy load R4 and the load are connected.

In the embodiment shown in Figure 1, the control chip (U1) includes five functional pins:

The peak current sampling pin (CS pin), connected to the reference ground through the resistor R3, is used to receive the peak current sampling signal;

Chip power supply pin (VDD pin), connected in series with resistor R1 and resistor R2, is used to supply power to the control chip; in the circuit shown in Figure 1, resistor R2 is the start-up resistor, VDD pin is connected to one end of resistor R2, and the resistor The other end of R2 is connected to one end of resistor R1, and the other end of resistor R1 is connected to any one of the two input ends of BD1 in AC input rectification and EMI circuit 1, and the VDD pin is externally connected to capacitor C1 to the reference ground ;

Internal integrated metal oxide semiconductor (MOS transistor) source pin (SW pin);

The metal oxide semiconductor drain pin (Drain pin) is internally integrated, and is connected to an output terminal of the step-down output circuit 3; in the circuit shown in FIG. One end is connected, and the other end of the step-down inductor L2 is connected to the negative pole of the LED light string; the Drain pin also needs to be connected to the positive pole of the freewheeling diode D1 in the step-down output circuit 3, and the negative pole of the freewheeling diode D1 is connected to the AC input Rectification is connected to the positive output of BD1 in EMI circuit 1;

The ground pin (GND pin) is connected with the reference ground and is used as the reference ground of the control chip.

FIG. 2 shows the connection circuit of the filtering circuit 4 at points A and B. As shown in FIG. 2(A) and (B), the filter circuit 4 may include capacitors, diodes and filter capacitors, and the filter circuit 4 may also include filter capacitors. In the actual operation process, according to different system requirements, choose one of them.

The LED driving circuit provided according to the embodiment of the present invention has a step-down structure, and the number of system parts is less than that of the LED driving circuit in the prior art (no absorption circuit is required), and has high current accuracy, high conversion efficiency, The advantage of a quick start.

The utility model has been described above with reference to the specific embodiments of the utility model, but those skilled in the art will understand that various modifications, combinations and changes can be made to these specific embodiments without departing from the requirements set by the appended claims or Its equivalents define the spirit and scope of the present invention. Furthermore, any signal arrows in the figures should be considered as illustrative only, and not restrictive, unless specifically indicated otherwise. Combinations of components or steps are also considered to have been recited when terms are foreseen to obscure the ability to separate or combine.

Claims (7)

1. a LED drive circuit, comprises AC power input rectifying and electromagnetic interference circuit, control circuit, reduced output voltage circuit and filter circuit, wherein:

The input of described AC power input rectifying and electromagnetic interference circuit is connected with AC power, and output is connected with the input of the input of described reduced output voltage circuit, the input of described control circuit and described filter circuit respectively;

An input of described control circuit is connected with the output of electromagnetic interference circuit with described AC power input rectifying, and another input is connected with an output of described reduced output voltage circuit, and output is connected with reference ground;

The input of described reduced output voltage circuit is connected with the output of electromagnetic interference circuit with described AC power input rectifying, and an output is connected with another input of described control circuit, and another output is connected with load;

The input of described filter circuit is connected with the output of electromagnetic interference circuit with described AC power input rectifying, and output is connected with reference ground.

2. LED drive circuit according to claim 1, is characterized in that, described control circuit comprises control chip, and described control chip comprises following functions pin:

Peak current sampling pin, for received current sampled signal;

Chip power supply pin, is used to described control chip power supply;

Inner integrated metal oxide semiconductor drain electrode pin, for receiving the voltage from described reduced output voltage circuit output;

Grounding leg, with reference to be connected, as the reference ground of described control chip.

3. LED drive circuit according to claim 2, is characterized in that,

Described peak current sampling pin by resistance and reference be connected;

Described chip power supply pin is connected with the output of electromagnetic interference circuit with described AC power input rectifying by being different from least one resistance of above-mentioned resistance,

Described chip power supply pin also by electric capacity with reference to be connected;

Described inner integrated metal oxide semiconductor drain electrode pin is connected with an output of described reduced output voltage circuit.

4. LED drive circuit according to claim 1, it is characterized in that, described reduced output voltage circuit comprises: buck inductor, fly-wheel diode, filter capacitor and output dummy load, wherein, between described filter capacitor, output dummy load and described load, be connected in parallel

One end of described buck inductor is connected with another input of described control circuit, and the other end is connected with described load with described filter capacitor, output dummy load respectively;

The positive pole of described fly-wheel diode is connected with another input of described control circuit, one end of described buck inductor respectively, and negative pole is connected with described load with described AC power input rectifying and the output of electromagnetic interference circuit, described filter capacitor, output dummy load respectively.

5. LED drive circuit according to claim 1, is characterized in that, described filter circuit comprises: electric capacity, diode and filter capacitor.

6. LED drive circuit according to claim 1, is characterized in that, described filter circuit comprises: filter capacitor.

7. according to the LED drive circuit described in any one in claim 1 to 6, it is characterized in that, described AC power input rectifying and electromagnetic interference circuit comprise: fuse, piezo-resistance, common mode filtering inductance, electric capacity and rectifier bridge.

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