CN203387408U - Flyback switch power supply circuit - Google Patents

Abstract

A flyback switch power supply circuit is disclosed. The flyback switch power supply circuit comprises a flyback switch circuit, an output filter circuit, a control circuit and a total harmonic distortion optimization circuit, wherein the input terminal of the flyback switch circuit and the output terminal of the control circuit as well as an input AC voltage are rectified and then are in power connection, and the output terminal is connected with the input terminal of the output filter circuit; the input terminal of the output filter circuit is connected with the output terminal of the flyback switch circuit, and the output terminal is connected with a load circuit; the input terminal of the control circuit is connected with the output terminal of the total harmonic distortion optimization circuit, and the output terminal is connected with the input terminal of the flyback switch circuit; and the input terminal of the total harmonic distortion optimization circuit and the input AC voltage are rectified and then are in power connection, and the output terminal is connected with the input terminal of the control circuit.

Description

Flyback switching power supply circuit

technical field

The utility model relates to the field of circuits, in particular to a flyback switching power supply circuit.

Background technique

At present, light-emitting diode (LED) technology has matured day by day. Since LED has the characteristics of high luminous efficiency and long service life, it is urgent to replace traditional incandescent lamps in the field of lighting. 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 power factor and high harmonic components. The low power factor and high harmonic components in the switching power supply scheme for low-power LEDs lead to problems such as large harmonic energy in the power grid, low energy utilization rate, and large transmission loss, which increases the burden on the power grid.

Utility model content

In view of one or more problems mentioned above, the utility model provides a novel flyback switching power supply circuit.

The flyback switching power supply circuit according to the embodiment of the present invention includes a flyback switching circuit, an output filter circuit, a control circuit, and a total harmonic distortion optimization circuit. Among them, the input end of the flyback switch circuit is connected with the output end of the control circuit and the rectified power supply of the input AC voltage, and the output end is connected with the input end of the output filter circuit; the input end of the output filter circuit is connected with the output end of the flyback switch circuit connection, the output terminal is connected to the load circuit; the input terminal of the control circuit is connected to the output terminal of the total harmonic distortion optimization circuit, and the output terminal is connected to the input terminal of the flyback switch circuit; the input terminal of the total harmonic distortion optimization circuit is connected to the input AC After the voltage is rectified, it is connected to the power supply, and the output terminal is connected to the output terminal of the control circuit.

In the flyback switching power supply circuit according to the embodiment of the present utility model, the phase difference between the input voltage of the control circuit and the input voltage of the entire flyback switching power supply circuit can be reduced by the total harmonic distortion optimization circuit, and by controlling The current ripple at the input end of the circuit can compensate the waveform distortion of the input current of the entire flyback switching power supply circuit, thereby improving the power factor of the entire flyback switching power supply circuit and reducing its harmonic components.

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 a flyback switching power supply circuit according to an embodiment of the present utility model (wherein, the load circuit is exemplarily shown as a string of LED lights).

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.

Fig. 1 shows a circuit diagram of a flyback switching power supply circuit according to an embodiment of the present invention. It should be noted that the flyback switching power supply circuit according to the embodiment of the present invention can be widely used in various load driving fields.

However, for the convenience of description, FIG. 1 illustrates a flyback switching power supply circuit according to an embodiment of the present invention by taking an application to an LED light string as an example. Of course, those skilled in the art should understand that the flyback switching power supply circuit of the present invention is by no means limited to being suitable for driving LEDs. Here, the flyback switching power supply circuit according to the embodiment of the present invention is developed based on a common flyback circuit.

As shown in FIG. 1 , the flyback switching power supply circuit according to the embodiment of the present invention includes a flyback switching circuit 1 , an output filter circuit 2 , a control circuit 3 , and a total harmonic distortion (Total Harmonic Distortion, THD) optimization circuit 4 . Among them, the input end of the flyback switch circuit 1 is connected to the output end of the control circuit 3 and the rectified power supply of the input AC voltage, and the output end is connected to the input end of the output filter circuit 2; the input end of the output filter circuit 2 is connected to the flyback switch The output end of the circuit 1 is connected, and the output end is connected to the load circuit; the input end of the control circuit 3 is connected to the output end of the THD optimization circuit 4, and the output end is connected to the input end of the flyback switch circuit 1; the input end of the THD optimization circuit 4 It is connected with the rectified power supply of the input AC voltage, and the output terminal is connected with the output terminal of the control circuit 3 .

In one embodiment of the present invention, the flyback switch circuit 1 includes a filter capacitor C1, a flyback transformer T1, a metal oxide semiconductor field effect transistor (MOSFET) Q1, a snubber diode D1, a snubber resistor R1, and a snubber capacitor C2.

In one embodiment of the present invention, the output filter circuit 2 includes two main parts, an output rectifier diode D2 and a filter capacitor C3. For different output ripple requirements, the output filter circuit 2 may also include a π-type filter circuit or a common-mode filter circuit.

In an embodiment of the present invention, the control circuit 3 is mainly composed of a pulse width modulation (PWM) chip U1 as the main control element, and is used to drive the MOSFET Q1 in the flyback switch circuit 1 . Wherein, the PWM chip U1 includes an input pin and an output pin, the input pin is a loop compensation pin (that is, the COMP pin, the COMP pin is connected to the output end of the THD optimization circuit 4 and an external capacitor C4 is connected to the ground), the output pin Connect to the source of MOSFET Q1 in flyback switch circuit 1.

In one embodiment of the present invention, the THD optimization circuit 4 includes resistors R2, R3, and a capacitor C5. Among them, one end of the resistor R2 is connected to the positive end of the capacitor C1 in the flyback switch circuit 1 (the end of R2 and the positive end of C1 are both connected to the power supply after rectifying the input AC voltage), and the other end is connected to one end of the resistor R3. The other end of the resistor R3 is connected to the ground; the connection node between R2 and R3 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is connected to the COMP pin of the PWM chip U1 in the control circuit 3 (that is, the input of the control circuit 3 end). The phase difference between the COMP pin and the input voltage can be reduced by THD optimization circuit 4, and the waveform distortion of the input current can be compensated by the ripple of the COMP pin, thereby improving the power factor and reducing the harmonic component.

The utility model has been described above with reference to the specific embodiments of the utility model, but those skilled in the art all understand that various modifications, combinations and changes can be made to these specific embodiments without departing from the claims or their equivalents. The spirit and scope of the utility model defined by the object.

Claims (7)

1. A flyback switching power supply circuit, comprising a flyback switching circuit, an output filter circuit, a control circuit, and a total harmonic distortion optimization circuit, wherein: The input end of the flyback switch circuit is connected to the output end of the control circuit and the rectified power supply of the input AC voltage, and the output end is connected to the input end of the output filter circuit; The input end of the output filter circuit is connected to the output end of the flyback switch circuit, and the output end is connected to the load circuit; The input end of the control circuit is connected to the output end of the total harmonic distortion optimization circuit, and the output end is connected to the input end of the flyback switch circuit; and The input terminal of the total harmonic distortion optimization circuit is connected with the rectified input AC voltage power supply, and the output terminal is connected with the input terminal of the control circuit. 2. The flyback switching power supply circuit according to claim 1, wherein the total harmonic distortion optimization circuit comprises two resistors and a capacitor, wherein the two resistors are connected in series when the input AC voltage is rectified Between the rear power supply and the ground, and the connection node between the two resistors is connected to one end of the one capacitor, and the other end of the one capacitor is connected to the input end of the control circuit. 3. The flyback switching power supply circuit according to claim 1, wherein the output filter circuit comprises an output rectifier diode and a filter capacitor. 4. The flyback switching power supply circuit according to claim 3, wherein the output filter circuit further comprises a π-type filter circuit or a common-mode filter circuit. 5. The flyback switching power supply circuit according to claim 1, wherein the control circuit comprises a pulse width modulation chip. 6. The flyback switching power supply circuit according to claim 5, wherein the input pin of the pulse width modulation chip is connected to the output terminal of the total harmonic distortion optimization circuit and an external capacitor is connected to ground, and the The output pin of the pulse width modulation chip is connected with the input end of the flyback switch circuit. 7. The flyback switching power supply circuit according to claim 1, wherein the flyback switching circuit comprises a filter capacitor, a flyback transformer, a metal oxide semiconductor field effect transistor, a snubber diode, a snubber resistor, and a snubber capacitor .

Images