TWM499024U - LED driver circuit - Google Patents

Description

LED drive circuit

The present invention relates to the field of circuits, and more particularly to an LED driving circuit.

At present, LED technology has become increasingly mature, and various LED lamps have been seen everywhere in the market. This trend is in line with the requirements of energy saving and low carbon. However, as LED lamps enter thousands of households, the requirements for luminaire efficiency and cost are also increasing. However, the current LED power supply on the market is generally low-voltage and high-current type. This type of LED power supply has the disadvantages of many parts, large volume, low power conversion efficiency, and large heat generation. Therefore, a new type of LED driving circuit is needed to solve the above problems.

In view of one or more of the problems described above, the present application provides a novel LED driver circuit.

The LED driving circuit according to the embodiment of the present invention comprises an AC power input rectification and electromagnetic interference filtering circuit, a control circuit, and a buck structure switching circuit, wherein: an input end of the AC input rectification and electromagnetic interference filtering circuit is connected to the AC power source, The output end is connected to the first terminal of the control circuit; the first terminal of the control circuit is connected with the output terminal of the AC input rectification and electromagnetic interference filter circuit and the first terminal of the buck structure switch circuit, and the second terminal and the buck structure a second terminal of the switching circuit is connected, the third and fourth terminals are connected to a reference ground; and a first terminal of the step-down structure switching circuit is connected to the first terminal of the control circuit, and the second terminal is connected to the second terminal of the control circuit The terminals are connected and the load circuit is spanned between the third terminal and the fourth terminal of the buck structure switching circuit.

The LED driving circuit according to the present embodiment has the advantages of high conversion efficiency, small number of system parts, and small volume.

1‧‧•AC (AC) input rectification and electromagnetic interference (EMI) filter circuit

2‧‧‧Control circuit

3‧‧‧Buck structure switch circuit

C1, C2, C4‧‧‧ filter capacitor

C3‧‧‧Power supply capacitor

D1, D2, D3, D4‧‧ ‧ Rectifiers

F1‧‧‧Fuse

L1‧‧‧Filter Inductor

L2‧‧‧Buck Switch Inductor

R1‧‧‧ output dummy load

U1‧‧‧Control chip

Drain‧‧‧汲 pole

HV‧‧‧High pressure feet

GND‧‧‧Grounding feet

VDD‧‧‧ power supply foot

Fig. 1 is a circuit diagram showing an LED driving circuit according to the present embodiment.

Features and exemplary embodiments of various aspects of the present teachings are described in detail below with reference to the drawings. The following description covers many specific details to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely provided to provide a clearer understanding of the present invention by the example of the present invention. The present invention is in no way limited to any specific configuration as set forth below, but without departing from the spirit of the present invention, any modification, substitution, or modification of the related elements or components.

The LED drive circuit according to the present embodiment is developed based on a buck structure switching circuit. The LED driving circuit according to the present embodiment will be described in detail below with reference to FIG.

Fig. 1 is a circuit diagram showing an LED driving circuit according to the present embodiment. As shown in FIG. 1, the LED driving circuit includes an alternating current (AC) input rectification and electromagnetic interference (EMI) filter circuit 1, a control circuit 2, and a buck structure switching circuit 3.

Wherein, the input end of the AC input rectification and EMI filter circuit 1 is connected to the AC power source, and the output end is connected to the first terminal of the control circuit 2; the first terminal of the buck structure switching circuit 3 is also the same as the control circuit 2 One terminal is connected, the second terminal of the buck structure switching circuit 3 is connected to the second terminal of the control circuit 2, and the load circuit driven by the LED driving circuit spans the third and fourth of the buck structure switching circuit 3 Between terminals; first terminal of control circuit 2 Simultaneously connected to both the output terminal of the AC input rectification and EMI filter circuit 1 and the first terminal of the buck structure switching circuit 3, the second terminal of the control circuit 2 is connected to the second terminal of the buck structure switching circuit 3, And the third terminal of the control circuit 2 is connected to the reference ground.

The LED driving circuit has the characteristics of stable current output (for example, 40 mA ^to 80 mA), no current detecting resistor, no starting resistor, built-in freewheeling diode, and valley bottom conduction, and can overcome many parts of the LED driving circuit in the prior art. Large volume, low power conversion efficiency, and high heat generation.

As shown in FIG. 1, in one embodiment, the AC input rectification and EMI filter circuit 1 includes a fuse F1, rectifying diodes D1, D2, D3, D4, a filter inductor L1, and filter capacitors C1 and C2. The four rectifying diodes D1, D2, D3, and D4 are connected in a bridge rectified structure for rectifying the input AC AC signal. In addition, the filter inductor L1 and the filter capacitors C1, C2 together constitute an EMI filter circuit for filtering the rectified signal.

In one embodiment, the control circuit 2 includes a control wafer U1 and a power supply capacitor C3. The control chip U1 includes four function legs: a drain pin Drain, a high voltage pin HV, a ground pin GND and a power supply pin VDD, as follows:

(1) Drain foot Drain, which is a gate of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) that controls the inside of the wafer U1, and is used to control the gate of the MOSFET. The switch is turned on and on, and the control circuit 2 also performs overvoltage protection (OVP) monitoring through the demagnetization time of the drain waveform at the drain pin Drain. When the demagnetization time is less than the predetermined threshold, the control circuit 2 will perform an operation related to the overvoltage protection.

The high voltage foot HV is a cathode that controls the freewheeling diode inside the wafer U1. When the MOSFET inside the control wafer U1 is turned off, the buck switching inductor L2 in the buck structure switching circuit 3 discharges power to the load circuit through the built-in diode.

(3) The grounding pin GND is connected to the reference ground and serves as a reference ground for controlling the wafer U1.

(4) The power supply pin VDD is connected to the grounding pin GND through the power supply capacitor C3 for supplying power to the control chip U1. When the MOSFET inside the control chip U1 is turned off, its 汲 is extremely high voltage level, at which time the power supply capacitor C3 will be charged by controlling the drain of the MOSFET inside the wafer U1.

The power supply pin VDD is connected to the first terminal of the power supply capacitor C3, and the ground pin GND and the second terminal of the power supply capacitor C3 are both connected to the reference ground. The high voltage foot HV is connected as the first terminal of the control circuit 2 to both the output terminal of the AC input rectification and EMI filter circuit 1 and the first terminal of the buck structure switch circuit 3, and the drain pin Drain is used as the control circuit 2 The two terminals are connected to the second terminal of the step-down structure switching circuit 3, and the third terminal of the second terminal control circuit 2 of the power supply capacitor C3, the ground pin GND is the fourth terminal of the control circuit 2. According to an embodiment of the present invention, the control circuit 2 is responsible for controlling the operation of the entire LED drive circuit, such as controlling the demagnetization process of the buck structure switching circuit 3, overvoltage protection, and the like. In some embodiments of the present author, the control wafer U1 may be a pulse width modulated (PWM) wafer.

In one embodiment, the buck structure switching circuit 3 includes a filter capacitor C4, a buck switch inductor L2, and an output dummy load R1. The filter capacitor C4 and the output dummy load R1 are connected in parallel. The first terminal of the parallel structure is the third terminal of the buck structure switch circuit 3 and the second terminal of the parallel structure is the fourth terminal of the buck structure switch circuit 3. As described above, there is a load circuit connected across it; the buck switch inductor L2 is connected in series between the second terminal of the control circuit 2 and the fourth terminal of the buck structure switching circuit 3.

Specifically, in the LED driving circuit shown in FIG. 1, when the input terminal of the AC input rectification and EMI filter circuit 1 is connected to the AC power source, the gate pin Drain of the control chip U1 in the control circuit 2 is directed to the control chip U1. The power supply capacitor C3 connected to the power supply pin VDD is charged. When the voltage at the supply pin VDD of the control wafer U1 reaches the set threshold (T1) inside the control wafer U1, the control wafer U1 starts operating. When the MOSFET inside the control wafer U1 is turned on, the LED driving circuit starts to supply power to the load circuit, and the buck switch in the buck structure switching circuit 3 The inductor L2 starts to store energy; when the peak value of the buck switch inductor L2 in the buck structure switching circuit 3 reaches the set threshold (T2) inside the control wafer U1, the MOSFET inside the control wafer U1 is turned off, and the buck switching inductor L2 The demagnetization is started to supply the energy stored during the conduction through the freewheeling diode of the control wafer U1 to the load circuit via the high voltage pin HV of the control wafer U1 while supplying power to the power supply pin VDD of the control wafer U1. When the energy of the buck switching inductor L2 in the buck switching circuit 3 is released, the voltage at the drain Drain of the control wafer U1 starts to drop, and the control wafer U1 detects this and then turns on the inside of the control wafer U1 again. The MOSFET is turned on to achieve valley bottom. During the turn-off of the MOSFET inside the control wafer U1, the control wafer U1 will detect the demagnetization time of the buck switch inductor L2. If the demagnetization time is less than the internal threshold (T3) of the control wafer U1, the control chip U1 considers that the output has occurred. In the overvoltage state, the control wafer U1 is immediately stopped and the operation is started again after the time set inside the control wafer U1. When the temperature of the control wafer U1 exceeds the set threshold (T4) inside the control wafer U1, the control wafer U1 also stops working immediately until the temperature drops to another set threshold (T5) inside the control wafer U1, and the control wafer U1 is controlled. Return to work.

As can be seen from FIG. 1, the LED driving circuit provided according to the present creative embodiment is developed based on a common step-down structure switching circuit, has a stable current output (for example, 40 mA ^to 80 mA), and the LED driving circuit does not need current. The components such as the resistor and the starting resistor are detected, and the built-in freewheeling diode and the bottom conduction structure are adopted, so that the conversion efficiency is high, the number of system parts is small, and the volume is small.

The present invention has been described above with reference to the specific embodiments of the present invention, but it will be understood by those skilled in the art that various modifications, combinations and changes may be made to the specific embodiments without departing from the scope of the appended claims. The spirit and scope of this creation. In addition, any signal orientation in the figures should be considered as illustrative only and not limiting, unless otherwise specifically indicated.

1‧‧•AC (AC) input rectification and electromagnetic interference (EMI) filter circuit

2‧‧‧Control circuit

3‧‧‧Buck structure switch circuit

C1, C2, C4‧‧‧ filter capacitor

C3‧‧‧Power supply capacitor

D1, D2, D3, D4‧‧ ‧ Rectifiers

F1‧‧‧Fuse

L1‧‧‧Filter Inductor

L2‧‧‧Buck Switch Inductor

R1‧‧‧ output dummy load

U1‧‧‧Control chip

Drain‧‧‧汲 pole

HV‧‧‧High pressure feet

GND‧‧‧Grounding feet

VDD‧‧‧ power supply foot

Claims (8)

An LED driving circuit comprises an AC input rectification and electromagnetic interference filtering circuit, a control circuit, and a buck structure switching circuit, wherein: the input end of the AC input rectification and electromagnetic interference filtering circuit is connected with an AC power source, and the output end is a first terminal of the control circuit is connected; a first terminal of the control circuit is connected to an output end of the AC input rectification and electromagnetic interference filter circuit and a first terminal of the buck structure switch circuit, and a second terminal Connected to a second terminal of the buck structure switching circuit, the third and fourth terminals are connected to a reference ground; and the first terminal of the buck structure switching circuit is connected to the first terminal of the control circuit a second terminal is coupled to the second terminal of the control circuit, and a load circuit is spanned between the third terminal and the fourth terminal of the buck structure switching circuit. The LED driving circuit of claim 1, wherein the control circuit comprises a control chip, wherein the control chip comprises only the following function legs: a tripod foot, the gate pin is the control a drain of a metal-oxide-semiconductor field-effect transistor (MOSFET) inside the wafer for controlling turn-off and conduction of the MOSFET; a high-voltage leg that is a freewheeling diode inside the control wafer a cathode; a power supply pin for powering the control wafer; and a grounding pin for use as a reference ground for the control wafer. The LED driving circuit of claim 2, wherein the control circuit further comprises a power supply capacitor, wherein: the first terminal of the power supply capacitor is connected to the power supply pin of the control chip, The second terminal is a third terminal of the control circuit; a gate pin of the control chip is a second terminal of the control circuit; and a ground pin of the control chip is a fourth terminal of the control circuit. The LED driving circuit of claim 2, wherein the step-down junction The switching circuit includes: a filter capacitor, a buck switch inductor, and an output dummy load, wherein: the filter capacitor and the output dummy load are connected in parallel, and the first terminal of the parallel structure of the filter capacitor and the output dummy load is a third terminal of the buck structure switching circuit and a second terminal of the parallel structure of the filter capacitor and the output dummy load is a fourth terminal of the buck structure switching circuit; and the buck switch inductor string Connected between the second terminal of the control circuit and the fourth terminal of the buck structure switching circuit. The LED driving circuit of claim 4, wherein the step-down switching inductor releases electrical energy to the load circuit through a freewheeling diode inside the control wafer. The LED driving circuit of claim 2 or 3, wherein the control circuit further performs overvoltage protection monitoring by a demagnetization time of the drain waveform at the gate pin. The LED driving circuit of claim 3, wherein when the metal oxide semiconductor field effect transistor (MOSFET) inside the control wafer is turned off, the voltage level at the gate pin It is quasi-high voltage level, at which time the power supply capacitor is charged through the MOSFET of the MOSFET. The LED driving circuit of claim 1, wherein the AC input rectification and electromagnetic interference filtering circuit comprises: a fuse, a rectifier bridge formed by four rectifying diodes, a filter inductor, and a first filter. Capacitor, and second filter capacitor.