CN204578369U - Inverse-excitation type switch power-supply circuit - Google Patents

Abstract

Disclose a kind of inverse-excitation type switch power-supply circuit.The output of ac rectifier is connected with the input of electromagnetic interference filter circuit; The input of electromagnetic interference filter circuit is connected with the output of ac rectifier, and output is connected with the input of start-up circuit; The input of start-up circuit is connected with the output of electromagnetic interference circuit, and output is connected with the input of flyback switching circuit and control circuit; The input of flyback switching circuit is connected with the output of start-up circuit and control circuit, and output is connected with the input of feedback circuit, output rectifier and filter and control circuit; The input of output rectifier and filter is connected with the output of flyback switching circuit; The input of control circuit is connected with the output of start-up circuit, flyback switching circuit and feedback circuit, and output is connected with the input of flyback switching circuit; The input of feedback circuit is connected with the output of flyback switching circuit, and output is connected with the input of 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

The global energy is becoming increasingly tense, and energy saving, emission reduction, and green energy have become the development trend in the energy field. Relevant energy efficiency standards are becoming more and more stringent, and the new six-level energy efficiency proposes a standby requirement of 75 milliwatts (mW). Big-name mobile phone manufacturers such as Samsung, LG, and Nokia jointly launched a stricter standby rating system, among which only chargers with standby power consumption less than 30mW are designated as five-star chargers. Therefore, using low-cost solutions to achieve low standby power consumption has become a competitive advantage for power management chip manufacturers.

Utility model content

In view of the above problems, the utility model proposes a novel flyback switching power supply circuit.

A flyback switching power supply circuit according to the utility model includes an AC rectification circuit, an electromagnetic interference filter circuit, a starting circuit, a flyback switch circuit, an output rectification filter circuit, a control circuit, and a feedback circuit. Among them, the input end of the AC rectification circuit is connected to the AC power supply, and the output end is connected to the input end of the electromagnetic interference filter circuit; the input end of the electromagnetic interference filter circuit is connected to the output end of the AC rectification circuit, and the output end is connected to the start circuit. The input end is connected; the input end of the start-up circuit is connected with the output end of the electromagnetic interference circuit, and the output end is connected with the input end of the flyback switch circuit and the input end of the control circuit; the input end of the flyback switch circuit is connected with the start-up circuit The output end is connected with the output end of the control circuit, the output end is connected with the input end of the feedback circuit, the input end of the output rectification filter circuit, and the input end of the control circuit; the input end of the output rectification filter circuit is connected with the flyback switch circuit The output terminals are connected, and the output terminals are connected to the load; the input terminals of the control circuit are connected to the output terminals of the start-up circuit, the output terminals of the flyback switching circuit, and the output terminals of the feedback circuit, and the output terminals are connected to the input terminals of the flyback switching circuit. The input terminal of the feedback circuit is connected with the output terminal of the flyback switching circuit, and the output terminal is connected with the input terminal of the control circuit.

Compared with the existing power supply circuit, the flyback switching power supply circuit according to the utility model has fewer peripheral parts, low cost and low standby power consumption. In addition, in the flyback switching power supply circuit according to the utility model, low-current start-up and low-current operating characteristics can be realized, the standby power consumption of the system can be reduced, and the standby power consumption of the five-star charger and the latest energy star such as Energy Star can be satisfied. standard requirements.

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 block diagram of a flyback switching power supply circuit according to an embodiment of the present invention;

Fig. 2 shows a circuit diagram of a flyback switching power supply circuit according to an embodiment of the present invention;

Figure 3 shows various connection methods of the electromagnetic interference (EMI) filter circuit;

Figure 4 shows various connections of the snubber circuit; and

Figure 5 shows two connection methods of the output rectification filter circuit.

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 utility model proposes a novel flyback switching power supply circuit. Fig. 1 shows a block diagram of a flyback switching power supply circuit according to an embodiment of the present invention. As shown in Figure 1, the flyback switching power supply circuit according to the embodiment of the utility model includes an AC rectification circuit 1, an electromagnetic interference (EMI) filter circuit 2, a starting circuit 3, a flyback switching circuit 5, an output rectification filter circuit 6, Feedback circuit 7, and control circuit 8.

Wherein, the input end of the AC rectification circuit 1 is connected with the AC power supply, and the output end is connected with the input end of the electromagnetic interference filter circuit 2; the input end of the electromagnetic interference filter circuit 2 is connected with the output end of the AC rectification circuit 1, and the output end It is connected with the input end of the start-up circuit 3; the input end of the start-up circuit 3 is connected with the output end of the electromagnetic interference circuit 2, and the output end is connected with the input end of the flyback switch circuit 5 and the input end of the control circuit 8; the flyback The input end of the switch circuit 5 is connected with the output end of the starting circuit 3 and the output end of the control circuit 8, and the output end is connected with the input end of the feedback circuit 7, the input end of the output rectification filter circuit 6, and the input end of the control circuit 8. Connect; the input terminal of the output rectification filter circuit 6 is connected with the output terminal of the flyback switch circuit 5, and the output terminal is connected with the load; the input terminal of the control circuit 8 is connected with the output terminal of the starting circuit 3, and the output of the flyback switch circuit 5 end, and the output end of the feedback circuit 7 are connected, and the output end is connected with the input end of the flyback switch circuit 5; the input end of the feedback circuit 7 is connected with the output end of the flyback switch circuit 5, and the output end is connected with the control circuit 8 connected to the input. The flyback switch circuit 5 may further include a snubber circuit 4 across both ends of the primary winding of the flyback transformer in the flyback switch circuit 5 .

Fig. 2 shows a circuit diagram of a flyback switching power supply circuit according to an embodiment of the present invention. Referring to Fig. 2 below, the AC rectifier circuit 1, electromagnetic interference (EMI) filter circuit 2, start-up circuit 3, absorbing circuit 4, and flyback switching circuit 5 included in the flyback switching power supply circuit according to the embodiment of the utility model are described in detail. 1. The circuit composition and function of the output rectification filter circuit 6, the feedback circuit 7, and the control circuit 8.

In the embodiment shown in FIG. 2 , the AC rectification circuit 1 includes a fuse (FUSE) and rectification diodes D1-D4, and its main function is to rectify the AC voltage. Wherein, the number of rectifying diodes included in the AC rectifying circuit 1 may be at least one and may be eight at most. The fuses included in the AC rectifying circuit 1 can be replaced by fuse resistors, wire-wound resistors or inductors.

In the embodiment shown in FIG. 2 , the EMI filter circuit 2 includes inductors L1 and L2 , high-voltage electrolytic capacitors C1 and C2 , and electrostatic discharge (ESD) resistor R1 , whose main function is to suppress EMI and filter after rectification. According to different applications, the EMI filter circuit can include one or two inductors, or only one common mode inductor (while including one or more high-voltage electrolytic capacitors); it can only include one high-voltage electrolytic capacitor (while including one or more Two inductors or one common mode inductor at the same time); and in some occasions, the ESD discharge resistor R1 may not be included. Figure 3 shows a variety of connection methods of the EMI filter circuit, where R1 is the ESD discharge resistor, which can be connected in series or in parallel to achieve the required resistance, or can be canceled.

In the embodiment shown in Figure 2, the main function of the start-up circuit 3 is to provide a start-up current through the start-up resistors R2 and R3, and the start-up current enters the PIN of the control circuit 8 after being amplified by the switch tube Q1 in the flyback switch circuit 5 -D, and then charge the power supply capacitor C4 of the starting circuit 3 through the PIN-F of the control circuit 8, so as to achieve the purpose of starting the control circuit 8. The start-up resistor can choose a relatively large resistance value to realize low-current start-up, reduce power loss of the start-up circuit, and reduce system standby power consumption.

In the embodiment shown in FIG. 2, the snubber circuit 4 can be varied according to different system requirements. Furthermore, the absorbing circuit can also be completely eliminated according to different market requirements, thereby further reducing the cost. Figure 4 shows various connection methods of the snubber circuit. It can be seen from FIG. 2 that the snubber circuit 4 straddles both ends of the primary winding of the switch tube Q1 in the flyback switch circuit 5 .

In the embodiment shown in FIG. 2 , the flyback switch circuit 5 includes a flyback transformer T1, a switch tube Q1, and a current detection resistor Rs, and its main function is to convert the high-voltage DC voltage after AC rectification into relatively low AC voltage. The current detection resistor Rs can be connected in series or in parallel to achieve the required resistance.

In the embodiment shown in FIG. 2 , the output rectification and filtering circuit 6 includes two main parts, an output rectification diode D4 and a filter capacitor Co. For different output ripple requirements, the output rectification filter circuit 6 can add a π-type filter circuit or a common-mode filter circuit to improve the filter effect. Figure 5 shows two connection methods of the output rectification filter circuit to achieve different ripple requirements.

In the embodiment shown in Figure 2, the feedback circuit 7 includes sampling resistors R5 and R6, whose main function is to use the sampling resistors to proportionally induce the secondary AC voltage (on the feedback winding AC voltage) to the control circuit 8. In principle, there is no optocoupler and secondary reference voltage regulator, which greatly reduces the cost. The sampling resistors can be connected in series or in parallel to achieve the required resistance.

In the embodiment shown in FIG. 2 , the main component of the control circuit 8 is a pulse width modulation (PWM) control chip. Wherein, the control chip can be, for example, OB2550 or a control chip with similar functions, and the chip includes the following 6 functional pins in total:

Feedback signal pin (PIN-A): used to detect the output voltage of the flyback switch circuit 5 and connected to the output terminal of the feedback circuit 7;

Ground pin (PIN-B): used for grounding;

Current detection pin (PIN-C): used to detect the primary side current of the flyback switch circuit 5, and provide turn-off control for the switch tube Q1 in the flyback switch circuit 5 according to the detected current, through the control circuit 8 PIN-D is connected to the switch tube Q1 in the flyback switch circuit 5;

Switch tube control pin (PIN-D): connected to the switch tube Q1 in the flyback switch circuit 5, used to control the switch on and off of the emitter of the switch tube Q1;

Drive pin (PIN-E): connected to the output terminal of the start-up circuit 3 and the input terminal of the flyback switch circuit 5;

Power supply pin (PIN-F): used to provide working voltage for the chip, and connected to the output terminal of the startup circuit 3 .

In the flyback switching power supply circuit according to the utility model, a larger start-up resistor is adopted, thereby realizing low-current start-up and low-current operating characteristics, reducing system standby power consumption, and meeting the standby requirements of five-star chargers Power consumption, and the requirements of the latest standards such as Energy Star. That is to say, the flyback switching power supply circuit according to the utility model overcomes the current technical bottleneck, and compared with the existing power supply circuit, it has fewer peripheral parts, lower cost, and lower standby power consumption.

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 (8)

1. an inverse-excitation type switch power-supply circuit, comprises ac rectifier, electromagnetic interference filter circuit, start-up circuit, flyback switching circuit, output rectifier and filter, control circuit and feedback circuit, wherein:

The input of ac rectifier is connected with AC power, and output is connected with the input of electromagnetic interference filter circuit;

The input of electromagnetic interference filter circuit is connected with the output of ac rectifier, and output is connected with the input of start-up circuit;

The input of start-up circuit is connected with the output of electromagnetic interference circuit, and output is connected with the input of control circuit with the input of flyback switching circuit;

The input of flyback switching circuit is connected with the output of control circuit with the output of start-up circuit, and output is connected with the input of the input of feedback circuit, the input of output rectifier and filter and control circuit;

The input of output rectifier and filter is connected with the output of flyback switching circuit, and output is connected with load;

The input of control circuit is connected with the output of start-up circuit, the output of flyback switching circuit and the output of feedback circuit, and output is connected with the input of flyback switching circuit;

The input of feedback circuit is connected with the output of flyback switching circuit, and output is connected with the input of control circuit; Wherein

Flyback switching circuit comprises flyback transformer, switching tube and current sense resistor, and control circuit comprises pulse width modulation control chip, and this pulse width modulation control chip comprises:

Feedback signal pin, for detecting the output voltage of flyback switching circuit, is connected with the output of feedback circuit;

Grounding leg, for ground connection;

Drive pin, be connected with the output of start-up circuit, the input of flyback switching circuit;

Current detecting pin, for detecting the primary current of flyback switching circuit, and providing the shutoff for the switching tube in flyback switching circuit to control according to the electric current detected, being connected to the switching tube in flyback switching circuit by switch controlled pin;

Switch controlled pin, is connected with the switching tube in flyback switching circuit, and the emitter for controlling the switching tube in flyback switching circuit is opened and shutoff;

Power supply pin, for providing operating voltage for this pulse width modulation control chip, is connected with the output of start-up circuit; And

The starting current that start-up circuit provides, after the switching tube in flyback switching circuit amplifies, enters the switch controlled pin of control circuit, then via the power supply pin of control circuit to the power supply capacitor charging of start-up circuit, thus start control circuit.

2. inverse-excitation type switch power-supply circuit according to claim 1, is characterized in that, flyback switching circuit also comprises the absorbing circuit across the armature winding two ends at flyback transformer.

3. inverse-excitation type switch power-supply circuit according to claim 1, is characterized in that, output rectifier and filter comprises output rectifier diode and filter capacitor.

4. inverse-excitation type switch power-supply circuit according to claim 3, is characterized in that, output rectifier and filter also comprises π type filter circuit and/or common mode filtering circuit.

5. inverse-excitation type switch power-supply circuit according to claim 1, is characterized in that, feedback circuit is made up of sample resistance.

6. inverse-excitation type switch power-supply circuit according to claim 1, is characterized in that, start-up circuit comprises starting resistance, and provides starting current by starting resistance.

7. inverse-excitation type switch power-supply circuit according to claim 1, is characterized in that, electromagnetic interference filter circuit comprises inductance and high-voltage electrolytic capacitor.

8. inverse-excitation type switch power-supply circuit according to claim 7, is characterized in that, electromagnetic interference filter circuit also comprises static discharge resistance.