CN202004664U - Primary-side-feedback flyback switching power supply circuit - Google Patents

Abstract

The utility model relates to a primary-side-feedback flyback switching power supply circuit, which comprises an alternating-current rectifier circuit, an electromagnetic interference filter circuit, a feedback circuit, a flyback switching circuit, an output rectifier filter circuit and a control circuit, wherein the input end of the alternating-current rectifier circuit is connected with an alternating-current power supply and the output end of the alternating-current rectifier circuit is connected with the input end of the electromagnetic interference filter circuit; the input end of the electromagnetic interference filter circuit is connected with the output end of the alternating-current rectifier circuit and the output end of the electromagnetic interference filter circuit is connected with the input end of the flyback switching circuit and the input end of the control circuit; the input end of the feedback circuit is connected with the output end of the flyback switching circuit and the output end of the feedback circuit is connected with the input end of the control circuit; and the input end of the flyback switching circuit is connected with the output end of the electromagnetic interference filter circuit and the output end of the control circuit, the output end of the flyback switching circuit is connected with the input ends of the feedback circuit, the output rectifier filter circuit and the control circuit, and the flyback switching circuit additionally comprises an absorbing circuit which stretches across the two ends of the primary winding of a flyback transformer in the flyback switching circuit.

Description

Primary side feedback flyback switching power supply circuit

technical field

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

Background technique

Now the world is saving energy and reducing emissions, and green energy is the general trend. Switching power supplies or chargers have put forward higher technical requirements for lower standby power consumption (for example, less than 50mW) and lower costs. The original design adopts the method of controlling the duty ratio and output voltage with the secondary feedback of the optocoupler and the secondary reference voltage regulator, which is costly and the size of the circuit board is large.

Contents of the invention

In view of the above problems, the utility model proposes a flyback switching power supply circuit using primary side feedback.

A flyback switching power supply circuit according to an embodiment of the present invention includes an AC rectification circuit, an electromagnetic interference filter circuit, a feedback circuit, a flyback switch circuit, an output rectification filter circuit, and a control 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 flyback switch The input end of the circuit is connected with the input end of the control circuit; the input end of the feedback circuit is connected with the output end of the flyback switch circuit, and the output end is connected with the input end of the control circuit; the input end of the flyback switch circuit is connected with the electromagnetic interference The output terminal of the filter circuit is connected to the output terminal of the control circuit, the output terminal is connected to the input terminal of the feedback circuit, the input terminal of the output rectification filter circuit, and the input terminal of the control circuit, and the flyback switch circuit also includes The absorption circuit at both ends of the primary winding of the flyback transformer in the excitation switching circuit; the input end of the output rectification filter circuit is connected with the output end of the flyback switching circuit, and the output end is connected with the load; and the input end of the control circuit is connected with the electromagnetic The output end of the interference filter circuit, the output end of the feedback circuit, and the output end of the flyback switch circuit are connected, and the output end is connected with the input end of the flyback switch circuit.

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, low cost and low standby power consumption.

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;

Fig. 3 shows various connection methods of the EMI filter circuit shown in Fig. 2;

Fig. 4 shows two connection methods of the output rectification filter circuit shown in Fig. 2;

Fig. 5 shows various connection methods of the snubber circuit shown in Fig. 2;

FIG. 6 shows various connection methods of the rectifying and filtering power supply circuits used in points A and B in the control circuit shown in FIG. 2 .

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 provides a 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 includes an AC rectifier circuit A, an electromagnetic interference filter circuit B, a feedback circuit C, a flyback switch circuit D, an output rectification filter circuit E, and a control circuit F, and the flyback switch Circuit D also includes a snubber circuit G.

Among them, the input end of the AC rectification circuit A is connected to the AC power supply, and the output end is connected to the input end of the electromagnetic interference filter circuit B; the input end of the electromagnetic interference filter circuit B is connected to the output end of the AC rectification circuit A, and the output end It is connected with the input end of the flyback switch circuit D and the input end of the control circuit F; the input end of the feedback circuit C is connected with the output end of the flyback switch circuit D, and the output end is connected with the input end of the control circuit F; The input end of the excitation switch circuit D is connected to the output end of the electromagnetic interference filter circuit B and the output end of the control circuit F, and the output end is connected to the input end of the feedback circuit C, the input end of the output rectification filter circuit E, and the control circuit F. The input terminal is connected; the input terminal of the output rectification filter circuit F is connected with the output terminal of the flyback switch circuit D, and the output terminal is connected with the load; and the input terminal of the control circuit F is connected with the output terminal and feedback of the electromagnetic interference filter circuit B The output end of the circuit C is connected with the output end of the flyback switch circuit D, and the output end is connected with the input end of the flyback switch circuit D.

Fig. 2 shows a circuit diagram of a pan-excited switching power supply circuit according to an embodiment of the present invention. As shown in Figure 2, the flyback switching power supply circuit according to an embodiment of the present invention includes an AC rectification circuit 1, an electromagnetic interference (EMI) filter circuit 2, an absorption circuit 3, a feedback circuit 4, a flyback switching circuit 5, Output rectification filter circuit 6, and control circuit 7.

In the embodiment shown in FIG. 2 , the AC rectification circuit 1 includes a fuse (FUSE) and a rectification diode, and its main function is to rectify the AC voltage. Wherein, the minimum number of rectifying diodes can be one, and the maximum number can be eight. Fuses can also be replaced with fuse resistors, wirewound resistors, or inductors.

In the embodiment shown in FIG. 2 , the EMI filter circuit 2 includes an inductor, a high-voltage electrolytic capacitor, and an electrostatic discharge (ESD) resistor, the main function of which is to suppress EMI and filter after rectification. According to different applications, two inductors can be used in the EMI filter circuit, or only one common mode inductor can be used; only one high-voltage electrolytic capacitor can be used; and in some occasions, the ESD discharge resistor R1 can also be omitted. Figure 3 shows various connection methods of the EMI filter circuit, where R1 is an 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 FIG. 2, the snubber circuit 3 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.

In the embodiment shown in Fig. 2, the feedback circuit 4 includes a sampling resistor, and its main function is to use the sampling resistor to send the secondary AC voltage (the AC voltage on the feedback winding) induced in proportion to the primary power supply winding of the transformer to the control Circuit 7. 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 Figure 2, the flyback switch circuit 5 includes a flyback transformer, a switching transistor, and a current detection resistor, and its main function is to convert the high-voltage DC voltage after AC rectification into a relatively low secondary voltage through the flyback transformer. 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 rectifying and filtering circuit 6 includes two main parts: an output rectifying diode and a filtering capacitor. 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 two reinforced output rectifying and filtering circuits, where R2 can be connected in parallel or in series with one or more resistors to achieve the required resistance value.

In the embodiment shown in FIG. 2 , the main components of the control circuit 7 are a pulse width modulation (PWM) control chip and necessary peripheral auxiliary components. For example, OB2520 or a control chip with similar functions, the chip (IC) contains a total of 6 functional pins, which are:

Power supply pin (PIN-A): used to provide the working voltage for the chip, connected to the flyback switch circuit 5 through the rectification and filtering power supply circuit in points A and B;

Feedback signal pin (PIN-B): used to detect the output voltage of the flyback switching power supply circuit, connected to the output terminal of the feedback circuit 4;

Low-pass filter pin (PIN-C): used for low-pass filter, external capacitor to ground, external capacitor can be connected in series and/or in parallel to achieve the desired filtering effect;

Current detection pin (PIN-D): used to detect the output current of the flyback switching power supply circuit, and provide protection for the switch tube Q1 in the flyback switching circuit 5 according to the detected current, through the flyback switching circuit The RC network in 5 is connected to the switching tube current detection resistor Rs;

Switch tube driving pin (PIN-E): used to drive the switch tube Q1, connected to the flyback switch circuit 5 through Q1;

Ground pin (PIN-F): used for grounding.

(PIN order is not limited to the above order)

Wherein, a resistor may or may not be connected between the current detection pin and the switch tube Q1.

Fig. 6 shows various connection methods of the rectification and filtering power supply circuit in points A and B in the control circuit.

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 (9)

1. an inverse-excitation type switch power-supply circuit comprises ac rectifier, electromagnetic interference filter circuit, feedback circuit, anti-energizing switch circuit, output rectifier and filter, reaches control circuit, wherein:

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

The input of described electromagnetic interference filter circuit is connected with the output of described ac rectifier, and output is connected with the input of described anti-energizing switch circuit and the input of described control circuit;

The input of described feedback circuit is connected with the output of described anti-energizing switch circuit, and output is connected with the input of described control circuit;

The input of described anti-energizing switch circuit is connected with the output of the output of described electromagnetic interference filter circuit and described control circuit, output is connected with the input of the input of described feedback circuit, described output rectifier and filter and the input of described control circuit, and described anti-energizing switch circuit also comprises the absorption circuit across the two ends of the elementary winding of the anti-violent change depressor in described anti-energizing switch circuit;

The input of described output rectifier and filter is connected with the output of described anti-energizing switch circuit, and output is connected with load; And

The input of described control circuit is connected with the output of the output of described electromagnetic interference filter circuit, described feedback circuit and the output of described anti-energizing switch circuit, and output is connected with the input of described anti-energizing switch circuit.

2. inverse-excitation type switch power-supply circuit according to claim 1 is characterized in that described control circuit comprises power-supply rectifying filter circuit and control chip, and described control chip comprises:

The A pin of powering is used to described control chip that operating voltage is provided, and is connected with the output of described anti-energizing switch circuit by described rectifying and wave-filtering power supply circuits;

B feedback signal pin is used to detect the output voltage of described inverse-excitation type switch power-supply circuit, is connected with the output of described feedback circuit;

C low-pass filtering pin is used for low-pass filtering, and external capacitor is to ground;

D current detecting pin, be used for detecting the former limit winding output current of described switch flyback switch circuit transformer, and provide turn-off protection for the switching tube in the described anti-energizing switch circuit according to the voltage that is detected, be connected with the output of described anti-energizing switch circuit;

The E switching tube drives pin, is used for driving the switching tube of described anti-energizing switch circuit, and is connected with described anti-energizing switch circuit by described switching tube; And

The F grounding leg is used for ground connection.

3. inverse-excitation type switch power-supply circuit according to claim 1 is characterized in that described ac rectifier comprises fuse and rectifier diode, and the number of described rectifier diode is between 1 to 8.

4. inverse-excitation type switch power-supply circuit according to claim 1 is characterized in that, described electromagnetic interference filter circuit comprises inductance and high-pressure electrolysis electric capacity.

5. inverse-excitation type switch power-supply circuit according to claim 3 is characterized in that described electromagnetic interference filter circuit also comprises static discharge resistance.

6. inverse-excitation type switch power-supply circuit according to claim 1 is characterized in that, described feedback circuit comprises series connection and/or a plurality of sample resistances in parallel.

7. inverse-excitation type switch power-supply circuit according to claim 1 is characterized in that, described anti-energizing switch circuit comprises anti-violent change depressor, switch triode and current sense resistor.

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

9. inverse-excitation type switch power-supply circuit according to claim 7 is characterized in that, described output rectifier and filter also comprises π type filter circuit or common mode filtering circuit.

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