CN216490237U

CN216490237U - Switching power supply

Info

Publication number: CN216490237U
Application number: CN202122606802.5U
Authority: CN
Inventors: 邓志谊; 张永磊; 丁辉清
Original assignee: Kangding Electronics Co ltd
Current assignee: Kangding Electronics Co ltd
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2022-05-10
Anticipated expiration: 2031-10-28

Abstract

The utility model discloses a switching power supply which comprises an input rectifying and filtering module, a transformer, an output rectifying and filtering module, a feedback comparison module and a switch control module. The transformer is provided with a primary coil and a secondary coil, and the switch control module comprises a control unit, a bleeder switch unit and a variable frequency switch unit. The input rectifying and filtering module is used for rectifying and filtering the input power supply; the output rectifying and filtering module is used for rectifying and filtering the output voltage of the transformer; the switch control module is used for adjusting the output voltage of the transformer; the feedback comparison module is used for comparing the output voltage of the output rectifying and filtering module with the first reference voltage and feeding the result back to the switch control module. The switching power supply disclosed by the utility model can adjust the output voltage of the transformer and improve the voltage withstanding performance, thereby stabilizing the output voltage of the output rectifying and filtering module, expanding the voltage output range and being beneficial to improving the comprehensive performance.

Description

Switching power supply

Technical Field

The utility model relates to the technical field of power electronics, in particular to a switching power supply.

Background

In an electricity meter, a line frequency transformer is generally used to convert an input voltage into a suitable voltage for use by the meter. However, the input voltage range of the current industrial frequency transformer is small, and the input voltage is easy to damage in some environments with large input voltage variation or under the condition of high input voltage, so that the comprehensive performance of the circuit is poor.

SUMMERY OF THE UTILITY MODEL

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the utility model provides a switching power supply which can improve the comprehensive performance.

The switching power supply according to the embodiment of the utility model includes: an input rectification filter module; the transformer is provided with a primary coil and a secondary coil, and the first end of the primary coil is connected with the output end of the input rectifying and filtering module; the input end of the output rectifying and filtering module is connected with the first end of the secondary coil; the input end of the feedback comparison module is connected with the output end of the output rectifying and filtering module; the switch control module comprises a control unit, a bleeder switch unit and a variable frequency switch unit, wherein the input end of the bleeder switch unit is connected with the second end of the primary coil, the output end of the bleeder switch unit is connected with the input end of the variable frequency switch unit, the output end of the variable frequency switch unit is grounded, the first output end of the control unit is respectively connected with the controlled end of the bleeder switch unit and the controlled end of the variable frequency switch unit, and the first input end of the control unit is connected with the output end of the feedback comparison module.

The switching power supply provided by the embodiment of the utility model has at least the following beneficial effects: the input rectifying and filtering module is used for rectifying and filtering input voltage and then outputting the input voltage to the transformer, and the output rectifying and filtering module is used for rectifying and filtering output voltage of the transformer and then outputting the output voltage; the feedback comparison module is used for comparing the output voltage of the output rectifying and filtering module with the first reference voltage and then feeding back a voltage signal to the control unit; the control unit is used for controlling the on-off of the bleeder switch unit and the variable frequency switch unit through the PWM signal under the feedback of the feedback comparison module, so as to regulate and control the output voltage of the transformer and further control the output voltage of the output rectification filter module; when the bleeder switch unit and the variable frequency switch unit are simultaneously cut off, a discharge loop is formed in the bleeder switch unit, and the bleeder switch unit and the variable frequency switch unit simultaneously bear input voltage, so that the voltage resistance of the circuit is favorably improved, and the voltage input range is favorably improved. Through the mutual cooperation of the feedback comparison unit, the control unit, the bleeder switch unit and the variable frequency switch unit, the voltage withstanding performance of the switch power supply is favorably improved, the output voltage of the switch power supply is more stable, and the input voltage range and the output voltage range of the switch power supply are favorably improved, so that the comprehensive performance of the switch power supply is improved.

According to some embodiments of the present invention, the input rectifying and filtering module comprises an input rectifying unit, a voltage comparing unit and a plurality of filtering units, wherein an output end of the input rectifying unit is respectively connected with a first input end of the voltage comparing unit and a first end of the primary coil; each filtering unit comprises a filtering capacitor, a voltage-resistant resistor and a conducting switch tube, wherein a first end of the voltage-resistant resistor is connected with an output end of the conducting switch tube or an input end of the conducting switch tube to form a voltage-dividing branch, the voltage-dividing branch is connected with the filtering capacitors in parallel, all the filtering capacitors are sequentially connected in series, a first end of the filtering capacitor of the first filtering unit is connected with an output end of the input rectifying unit, and a second end of the filtering capacitor of the last filtering unit is grounded; the output end of the voltage comparison unit is connected with the controlled end of the conduction switch tube, and the second input end of the voltage comparison unit is a reference voltage port, so that the power consumption is reduced, and the energy is saved.

According to some embodiments of the present invention, the feedback comparison module includes a feedback unit and a comparison unit, an input terminal of the feedback unit and an input terminal of the comparison unit are respectively connected to an output terminal of the output rectifying and filtering module, an output terminal of the feedback unit is connected to the first input terminal of the control unit, and a controlled terminal of the feedback unit is connected to the control terminal of the comparison unit, so as to facilitate feedback.

According to some embodiments of the present invention, the feedback unit includes a resistor R17, a resistor R18, and an optical coupler, a first end of the resistor R17 is connected to the output end of the output rectifying and filtering module, a second end of the resistor R17 is connected to the first end of the resistor R18 and an anode of a light emitting side of the optical coupler, a cathode of the light emitting side of the optical coupler is connected to the second end of the resistor R18 and the control end of the comparing unit, an anode of a light sensing side of the optical coupler is connected to the first input end of the control unit, and a cathode of the light sensing side of the optical coupler is grounded, so that accurate feedback is facilitated.

According to some embodiments of the present invention, the comparing unit includes a controllable precision regulator, a resistor R19, a resistor R20, a resistor R22, and a capacitor C16, a first end of the resistor R19 is connected to the output end of the output rectifying and filtering module, a second end of the resistor R19 is connected to a first end of the capacitor C16, a first end of the resistor R20, and a reference electrode of the controllable precision regulator, a second end of the capacitor C16 is connected to a first end of the resistor R22, a cathode of the controllable precision regulator is connected to a second end of the resistor R22 and a controlled end of the feedback unit, and an anode of the controllable precision regulator and a second end of the resistor R20 are grounded, so as to accurately compare and control the operation of the feedback unit.

According to some embodiments of the present invention, the bleeder switch unit includes a diode D2, a resistor R2, a resistor R3, and a switch Q1, wherein an anode of the diode D2 is connected to the first output terminal of the control unit, a cathode of the diode D2 is connected to the first end of the resistor R2, a second end of the resistor R2 is connected to the first end of the resistor R3 and the controlled end of the switch Q1, respectively, an input end of the switch Q1 is connected to the second end of the primary coil, and an output end of the switch Q1 is connected to the second end of the resistor R3 and the input end of the variable frequency switch unit, respectively, so as to divide voltage.

According to some embodiments of the present invention, the bleeder switch unit further includes a diode D1, a switch Q3, and a resistor R1, a second end of the resistor R2 is connected to a controlled end of the switch Q1 through the diode D1 and the resistor R1 which are sequentially connected, the controlled end of the switch Q3 is connected to a first end of the resistor R3, an input end of the switch Q3 is connected to a connection node of the diode D1 and the resistor R1, and an output end of the switch Q3 is connected to an output end of the switch Q1, so as to bleed a voltage and prevent the switch Q3 from being damaged.

According to some embodiments of the present invention, the variable frequency switch unit includes a resistor R4, a resistor R6, and a switch Q2, the controlled terminal of the switch Q2 is connected to the first output terminal of the control unit through the resistor R4, the input terminal of the switch Q2 is connected to the output terminal of the bleeder switch unit, the output terminal of the switch Q2 is connected to the first terminal of the resistor R6, and the second terminal of the resistor R6 is grounded, so as to divide voltage and adjust the output voltage of the transformer.

According to some embodiments of the present invention, the switch control module further comprises an overload protection unit, a first end of the overload protection unit is connected to the second input end of the control unit, a second end of the overload protection unit is connected to the output end of the switching tube Q2, and a third end of the overload protection unit is grounded, so as to protect a circuit.

According to some embodiments of the present invention, the switch control module further includes a voltage division protection unit, the transformer is further provided with an auxiliary coil, a first end of the auxiliary coil is connected to the second output end of the input rectifying and filtering module, a first end of the voltage division protection unit is connected to the first end of the auxiliary coil, and a voltage division end of the voltage division protection unit is connected to the second output end of the control unit, so as to protect a circuit.

Additional aspects and advantages of the utility model will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the utility model.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a circuit block diagram of a switching power supply according to an embodiment of the present invention;

fig. 2 is a detailed circuit block diagram of the switching power supply shown in fig. 1;

fig. 3 is a circuit diagram of an input rectifying and filtering module of the switching power supply shown in fig. 2;

fig. 4 is a circuit diagram of a transformer and an output rectifying and filtering module of the switching power supply shown in fig. 2;

FIG. 5 is a circuit diagram of a feedback comparison module of the switching power supply shown in FIG. 2;

fig. 6 is a circuit diagram of a switching control module of the switching power supply shown in fig. 2.

The reference numbers are as follows:

the transformer comprises an input rectifying and filtering module 100, an input rectifying unit 110, a voltage comparison unit 120, a filtering unit 130, a transformer 200, a primary coil 210, a secondary coil 220, an auxiliary coil 230, an output rectifying and filtering module 300, a feedback comparison module 400, a feedback unit 410, a comparison unit 420, a switch control module 500, a control unit 510, a bleeder switch unit 520, a variable frequency switch unit 530, an overload protection unit 540, and a voltage division protection unit 550.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and more than, less than, more than, etc. are understood as excluding the present number, and more than, less than, etc. are understood as including the present number. If any description to first, second and third is only for the purpose of distinguishing technical features, it is not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.

Referring to fig. 1, a switching power supply includes an input rectifying and filtering module 100, a transformer 200, an output rectifying and filtering module 300, a feedback comparing module 400, and a switching control module 500. The transformer 200 is provided with a primary coil 210 and a secondary coil 220, wherein a first end of the primary coil 210 is connected with an output end of the input rectifying and filtering module 100; the input end of the output rectifying and filtering module 300 is connected with the first end of the secondary coil 220; the input end of the feedback comparison module 400 is connected with the output end of the output rectifying and filtering module 300; the switch control module 500 includes a control unit 510, a bleeder switch unit 520 and a variable frequency switch unit 530, an input end of the bleeder switch unit 520 is connected to the second end of the primary coil 210, an output end of the bleeder switch unit 520 is connected to an input end of the variable frequency switch unit 530, an output end of the variable frequency switch unit 530 is grounded, a first output end of the control unit 510 is connected to a controlled end of the bleeder switch unit 520 and a controlled end of the variable frequency switch unit 530, respectively, and a first input end of the control unit 510 is connected to an output end of the feedback comparison module 400.

The input end of the input rectifying and filtering module 100 is a power port for power input, and the input rectifying and filtering module 100 is used for rectifying and filtering the input power and outputting the rectified and filtered power to the transformer 200; the output rectifying and filtering module 300 is used for rectifying and filtering the output voltage of the transformer 200 so as to output; the switch control module 500 is configured to adjust an output voltage of the transformer 200, so that the output rectifying and filtering module 300 outputs a stable voltage; the feedback comparison module 400 is configured to compare the output voltage of the output rectifying and filtering module 300 with a first reference voltage inside the feedback comparison module 400, and then feed back the result to the switch control module 500, for example, when the output voltage of the output rectifying and filtering module 300 is greater than the first reference voltage, the feedback comparison module 400 feeds back a voltage signal to the switch control module 500, so that the switch control module 500 adjusts the output voltage of the transformer 200; alternatively, when the output voltage of the output rectifying and filtering module 300 is less than or equal to the first reference voltage, the feedback comparing module 400 has no feedback.

The switch control module 500 includes a control unit 510, a bleeder switch unit 520 and a variable frequency switch unit 530, the control unit 510 is configured to control on and off of the bleeder switch unit 520 and the variable frequency switch unit 530 under feedback of the feedback comparison module 400, that is, the control unit 510 adjusts duty ratios of PWM waves output to the bleeder switch unit 520 and the variable frequency switch unit 530 under feedback of the feedback comparison module 400, so as to regulate and control output voltage of the transformer 200, which is beneficial to stably outputting output voltage of the rectifying and filtering module 300, and to expand a voltage output range of the output rectifying and filtering module 300; when the bleeder switch unit 520 and the variable frequency switch unit 530 are simultaneously turned off, a bleeder circuit is formed in the bleeder switch unit 520, and the bleeder switch unit 520 and the variable frequency switch unit 530 simultaneously bear input voltage, which is beneficial to improving the voltage withstanding performance of the switching power supply, thereby improving the voltage input range of the input rectifying and filtering module 100 and further improving the voltage output range of the output rectifying and filtering module 300. Through the cooperation of the feedback comparison module 400 and the switch control module 500, the voltage endurance of the switching power supply, the voltage input range of the input rectifying and filtering module 100 and the voltage output range of the output rectifying and filtering module 300 are improved, and the voltage output of the output rectifying and filtering module 300 is more stable, so that the comprehensive performance of the switching power supply is improved.

Referring to fig. 2 and 3, the input rectifying and filtering module 100 includes an input rectifying unit 110, a voltage comparing unit 120, and a plurality of filtering units 130, wherein an output terminal of the input rectifying unit 110 is connected to a first input terminal of the voltage comparing unit 120 and a first terminal of the primary coil 210, respectively; each of the filtering units 130 includes a filtering capacitor (not shown), a voltage-withstanding resistor (not shown) and a conducting switch tube (not shown), a first end of the voltage-withstanding resistor is connected to an output end of the conducting switch tube or an input end of the conducting switch tube to form a voltage-dividing branch, the voltage-dividing branch is connected in parallel with the filtering capacitors, all the filtering capacitors are sequentially connected in series, a first end of the filtering capacitor of the first filtering unit 130 is connected to an output end of the input rectifying unit 110, and a second end of the filtering capacitor of the last filtering unit 130 is grounded; the output end of the voltage comparing unit 120 is connected to the controlled end of the conducting switch tube, and the second input end of the voltage comparing unit 120 is a reference voltage port.

The voltage comparing unit 120 is configured to compare the output voltage of the input rectifying unit 110 with a second reference voltage input from the reference voltage port to obtain a comparison result, and control the on/off of the conducting switch tube based on the comparison result, so as to connect/disconnect the voltage-resistant resistor to/from the circuit. For example, when the output voltage of the input rectifying unit 110 is greater than the second reference voltage, the voltage comparing unit 120 outputs a level signal to the conducting switch tube to conduct the conducting switch tube, so that the voltage-resistant resistor is connected to the circuit, and the voltage-resistant resistor divides the voltage of the filter capacitor, thereby preventing the filter capacitor from being damaged due to overhigh voltage; when the output voltage of the input rectifying unit 110 is less than or equal to the second reference voltage, the voltage comparing unit 120 outputs a level signal to the conducting switch tube to turn off the conducting switch tube, so that the voltage-resistant resistor is disconnected from the circuit, and thus, when the filter capacitor normally works, the voltage-resistant resistor is prevented from generating useless power consumption, the power consumption of the circuit is reduced, and the comprehensive performance of the switching power supply is improved. In addition, the voltage resistance is connected, so that the voltage resistance performance is improved, and the voltage input range is enlarged.

It should be noted that, the voltage dividing branch is connected in parallel with the filter capacitor, that is, when the first end of the voltage-resistant resistor is connected with the output end of the conducting switch tube, the second end of the voltage-resistant resistor is connected with the second end of the filter capacitor, and the input end of the conducting switch tube is connected with the first end of the filter capacitor; when the first end of the voltage-resistant resistor is connected with the input end of the conduction switch tube, the second end of the voltage-resistant resistor is connected with the first end of the filter capacitor, and the output end of the conduction switch tube is connected with the second end of the filter capacitor. All the filter capacitors are sequentially connected in series, for example, when the number of the filter capacitors is two, the second end of the first filter capacitor is connected with the first end of the second filter capacitor, and the last filter capacitor is the second filter capacitor; when the number of the filter capacitors is three, the second end of the first filter capacitor is connected with the first end of the second filter capacitor, the second end of the second filter capacitor is connected with the first end of the third filter capacitor, and the last filter capacitor is the third filter capacitor.

The filter capacitor may be formed of one capacitor or a plurality of capacitors. The voltage comparing unit 120 may employ a chip having a comparator, for example, a chip such as LM393, LM324, or LM 358. The reference voltage port is used for inputting a second reference voltage so that the voltage comparison unit 120 operates. The conduction switch tube can adopt a triode or an MOS tube and other switch tubes.

Referring to fig. 2, 4 and 5, the feedback comparison module 400 includes a feedback unit 410 and a comparison unit 420, an input terminal of the feedback unit 410 and an input terminal of the comparison unit 420 are respectively connected to an output terminal of the output rectifying and filtering module 300, an output terminal of the feedback unit 410 is connected to a first input terminal of the control unit 510, and a controlled terminal of the feedback unit 410 is connected to a control terminal of the comparison unit 420. The comparing unit 420 is configured to compare the output voltage of the output rectifying and filtering module 300 with a first reference voltage inside the comparing unit 420, so as to control the feedback unit 410 to operate. For example, when the output voltage of the output rectifying and filtering module 300 is greater than the first reference voltage, the feedback unit 410 operates to change the voltage of the first input terminal of the control unit 510, so that the control unit 510 adjusts the duty ratio of the output PWM wave; alternatively, when the output voltage of the output rectifying and filtering module 300 is less than or equal to the first reference voltage, the feedback unit 410 is disabled, so that the control unit 510 maintains the duty ratio of the PWM wave.

Referring to fig. 4 and 5, the feedback unit 410 includes a resistor R17, a resistor R18, and an optical coupler, a first end of the resistor R17 is connected to an output end of the output rectifying and filtering module 300, a second end of the resistor R17 is connected to a first end of the resistor R18 and a positive electrode of a light-emitting side of the optical coupler, a negative electrode of the light-emitting side of the optical coupler is connected to a second end of the resistor R18 and a control end of the comparison unit 420, a positive electrode of a light-sensing side of the optical coupler is connected to a first input end of the control unit 510, and a negative electrode of the light-sensing side of the optical coupler is grounded. Wherein, divide voltage and current-limiting through resistance R17, resistance R18 to make the opto-coupler normally work, thereby under the control of comparing element 420, make the opto-coupler switch on, so that the luminous side of opto-coupler is luminous, and then change the voltage of the first input of the control unit 510 through the sensitization side of opto-coupler, realize the feedback function.

It should be noted that, in some embodiments, the feedback unit 410 may include a first resistor, a second resistor, a third resistor, and a first switch tube, a first end of the first resistor is connected to the output end of the output rectifying and filtering module 300, a second end of the first resistor is connected to the input end of the first switch tube, an output end of the first switch tube is connected to a first end of the second resistor, a second end of the second resistor is respectively connected to a first end of the third resistor and a first input end of the control unit 510, a second end of the third resistor is grounded, and a controlled end of the first switch tube is connected to the control end of the comparison unit 420.

Referring to fig. 4 and 5, the comparing unit 420 includes a controllable precision voltage regulator, a resistor R19, a resistor R20, a resistor R22 and a capacitor C16, a first end of the resistor R19 is connected to the output end of the output rectifying and filtering module 300, a second end of the resistor R19 is connected to a first end of the capacitor C16, a first end of the resistor R20 and a reference electrode of the controllable precision voltage regulator, a second end of the capacitor C16 is connected to a first end of the resistor R22, a cathode of the controllable precision voltage regulator is connected to a second end of the resistor R22 and a controlled end of the feedback unit 410, and an anode of the controllable precision voltage regulator and a second end of the resistor R20 are grounded. The output voltage of the output rectifying and filtering module 300 is input to a reference electrode of a controllable precise voltage-stabilizing source through a resistor R19 to obtain a reference voltage, the reference voltage is compared with a first reference voltage in the controllable precise voltage-stabilizing source by the controllable precise voltage-stabilizing source, and when the reference voltage is greater than the first reference voltage, conduction is performed between an anode and a cathode of the controllable precise voltage-stabilizing source, so that the feedback unit 410 works normally, and the feedback unit 410 feeds back a voltage signal; when the reference voltage is less than or equal to the first reference voltage, the anode and the cathode of the controllable precision voltage regulator are disconnected, that is, the controlled terminal of the feedback unit 410 is disconnected, so that the feedback unit 410 cannot feed back a voltage signal, and the control unit 510 maintains the duty ratio of the PWM wave, so that the output voltage of the transformer 200 is unchanged, which is beneficial to the stable output of the output rectifying and filtering module 300.

It should be noted that the comparing unit 420 may further include a capacitor CY1, and the anode of the controllable precision voltage regulator and the ground of the second terminal of the resistor R20 are signal grounds, the first terminal of the capacitor CY1 is connected to the signal ground, and the second terminal of the capacitor CY1 is connected to the protection ground, which is beneficial to filtering static electricity in the circuit to avoid electrostatic interference, so as to improve the overall performance of the switching power supply.

It should be noted that the controllable precision voltage regulator may be a TL431 or TL432 chip.

It should be noted that, in some embodiments, the comparing unit 420 may include a comparator and a second switching tube, an input end of the second switching tube is connected to the controlled end of the feedback unit 410, an output end of the second switching tube is grounded, an output end of the comparator is connected to the controlled end of the second switching tube, a first input end of the comparator is connected to the third reference voltage, and a second input end of the comparator is connected to the output end of the output rectifying and filtering module 300.

Referring to fig. 2 and 6, the bleeder switch unit 520 includes a diode D2, a resistor R2, a resistor R3, and a switch tube Q1, an anode of the diode D2 is connected to the first output terminal of the control unit 510, a cathode of the diode D2 is connected to the first end of the resistor R2, a second end of the resistor R2 is connected to the first end of the resistor R3 and the controlled end of the switch tube Q1, an input terminal of the switch tube Q1 is connected to the second end of the primary coil 210, and an output terminal of the switch tube Q1 is connected to the second end of the resistor R3 and the input terminal of the variable frequency switch unit 530. The switching tube Q1 is used to cooperate with the variable frequency switching unit 530 to be turned on or off at the same time under the control of the control unit 510 to change the output voltage of the transformer 200, so as to adjust the output voltage of the output rectifying and filtering module 300. When the switching tube Q1 is cut off, the switching tube Q1 is matched with the variable frequency switching unit 530 to simultaneously bear the input voltage, so as to avoid the damage of components in the circuit and be beneficial to improving the voltage input range of the input rectifying and filtering module 100; when the switching tube Q1 is turned off, the switching tube Q1 and the resistor R3 form a leakage loop to prevent the residual electricity from damaging the switching tube Q1. In addition, the diode D2 serves to prevent the surplus current from flowing backward into the control unit 510.

Referring to fig. 2 and 6, in some embodiments, the bleeder switch unit 520 further includes a diode D1, a switching tube Q3, and a resistor R1, a second end of the resistor R2 is connected to a controlled end of the switching tube Q1 through a diode D1 and a resistor R1 which are sequentially connected, the controlled end of the switching tube Q3 is connected to a first end of the resistor R3, an input end of the switching tube Q3 is connected to a connection node of the diode D1 and the resistor R1, and an output end of the switching tube Q3 is connected to an output end of the switching tube Q1. When the switching tube Q1 is turned off, the switching tube Q3 is turned on, so that the switching tube Q1, the switching tube Q3 and the resistor R1 form a discharging loop to discharge the residual electricity. When the switching tube Q1 is a MOS tube and the switching tube Q3 is a triode, the switching tube Q3 controls the on/off of the bleeder circuit of the switching tube Q1, which is beneficial to improving the reaction speed of the bleeder switch unit 520, so as to adjust the output voltage of the transformer 200 in time in cooperation with the variable frequency switch unit 530. In addition, the diode D1 is used to prevent residual current from flowing through the resistor R3.

Referring to fig. 2 and 6, the variable frequency switch unit 530 includes a resistor R4, a resistor R6, and a switch tube Q2, wherein a controlled terminal of the switch tube Q2 is connected to a first output terminal of the control unit 510 through a resistor R4, an input terminal of the switch tube Q2 is connected to an output terminal of the bleeder switch unit 520, an output terminal of the switch tube Q2 is connected to a first terminal of the resistor R6, and a second terminal of the resistor R6 is grounded. The switching tube Q2 is used for cooperating with the bleeder switch unit 520, and under the control of the control unit 510, adjusts the output voltage of the transformer 200, so that the voltage output of the switching power supply is more stable, and the voltage input range of the input rectifying and filtering module 100 and the voltage output range of the output rectifying and filtering module 300 are improved; in addition, under the control of the control unit 510, the switching tube Q2 is also used to cooperate with the bleeder switch unit 520 to bear the input voltage, so as to avoid the damage of components in the circuit, which is beneficial to improving the voltage input range of the input rectifying and filtering module 100.

Referring to fig. 2 and 6, the switching control module 500 further includes an overload protection unit 540, a first terminal of the overload protection unit 540 is connected to the second input terminal of the control unit 510, a second terminal of the overload protection unit 540 is connected to the output terminal of the switching tube Q2, and a third terminal of the overload protection unit 540 is grounded. The overload protection unit 540 includes a resistor R5 and a capacitor C3, a first end of the resistor R5 is connected to the second input terminal of the control unit 510 and a first end of the capacitor C3, a second end of the resistor R5 is connected to the output terminal of the switching tube Q2, and a second end of the capacitor C3 is grounded. The voltage at the output terminal of the switching tube Q2 is fed back to the control unit 510 through the resistor R5, so that the control unit 510 adjusts the duty ratio of the PWM wave to prevent the switching tube Q2 from being damaged by a high voltage.

It should be noted that, when the switching power supply is subjected to strong magnetic interference, the inductance of the transformer 200 decreases, so that the current flowing through the switching tube Q1, the switching tube Q2 and the resistor R6 increases, and the overload protection unit 540 feeds back the voltage at the output end of the switching tube Q2 to the control unit 510, so that the control unit 510 adjusts the duty ratio of the PWM wave to adjust the output voltage of the transformer 200, so that the inductance of the transformer 200 is stabilized within a certain range, so as to stabilize the output voltage of the output rectifying and filtering module 300, that is, the duty ratio of the PWM wave output by the control unit 510 is adjusted by the feedback of the overload protection unit 540, so as to alleviate the influence of the strong magnetic interference on the switching power supply, and to improve the overall performance of the switching power supply.

Referring to fig. 2 and 6, the switch control module 500 further includes a voltage division protection unit 550, the transformer 200 is further provided with an auxiliary coil 230, a first end of the auxiliary coil 230 is connected to the second output end of the input rectifying and filtering module 100, a first end of the voltage division protection unit 550 is connected to the first end of the auxiliary coil 230, and a voltage division end of the voltage division protection unit 550 is connected to the second output end of the control unit 510. The voltage division protection unit 550 includes a resistor R7, a resistor R8, and a capacitor C8, a first end of the resistor R7 is connected to the first end of the auxiliary coil 230, a second end of the resistor R7 is connected to the first end of the resistor R8, the first end of the capacitor C8, and the second output end of the control unit 510, and the second end of the resistor R8 and the second end of the capacitor C8 are both grounded. The voltage division protection unit 550 performs voltage division protection on the circuit to prevent the circuit from being damaged.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims

1. A switching power supply, comprising:

an input rectification filter module;

the transformer is provided with a primary coil and a secondary coil, and the first end of the primary coil is connected with the output end of the input rectifying and filtering module;

the input end of the output rectifying and filtering module is connected with the first end of the secondary coil;

the input end of the feedback comparison module is connected with the output end of the output rectifying and filtering module;

the switch control module comprises a control unit, a bleeder switch unit and a variable frequency switch unit, wherein the input end of the bleeder switch unit is connected with the second end of the primary coil, the output end of the bleeder switch unit is connected with the input end of the variable frequency switch unit, the output end of the variable frequency switch unit is grounded, the first output end of the control unit is respectively connected with the controlled end of the bleeder switch unit and the controlled end of the variable frequency switch unit, and the first input end of the control unit is connected with the output end of the feedback comparison module.

2. The switching power supply according to claim 1, wherein the input rectifying and filtering module comprises an input rectifying unit, a voltage comparing unit and a plurality of filtering units, and an output end of the input rectifying unit is respectively connected with a first input end of the voltage comparing unit and a first end of the primary coil;

each filtering unit comprises a filtering capacitor, a voltage-resistant resistor and a conducting switch tube, wherein a first end of the voltage-resistant resistor is connected with an output end of the conducting switch tube or an input end of the conducting switch tube to form a voltage-dividing branch, the voltage-dividing branch is connected with the filtering capacitors in parallel, all the filtering capacitors are sequentially connected in series, a first end of the filtering capacitor of the first filtering unit is connected with an output end of the input rectifying unit, and a second end of the filtering capacitor of the last filtering unit is grounded;

the output end of the voltage comparison unit is connected with the controlled end of the conduction switch tube, and the second input end of the voltage comparison unit is a reference voltage port.

3. The switching power supply according to claim 1, wherein the feedback comparison module comprises a feedback unit and a comparison unit, an input terminal of the feedback unit and an input terminal of the comparison unit are respectively connected to the output terminal of the output rectifying and filtering module, an output terminal of the feedback unit is connected to the first input terminal of the control unit, and a controlled terminal of the feedback unit is connected to the control terminal of the comparison unit.

4. The switching power supply according to claim 3, wherein the feedback unit comprises a resistor R17, a resistor R18 and an optical coupler, a first end of the resistor R17 is connected with an output end of the output rectifying and filtering module, a second end of the resistor R17 is connected with a first end of the resistor R18 and an anode of a light-emitting side of the optical coupler respectively, a cathode of the light-emitting side of the optical coupler is connected with a second end of the resistor R18 and a control end of the comparison unit respectively, an anode of a light-sensing side of the optical coupler is connected with a first input end of the control unit, and a cathode of the light-sensing side of the optical coupler is grounded.

5. The switching power supply according to claim 3, wherein the comparing unit comprises a controllable precision voltage regulator, a resistor R19, a resistor R20, a resistor R22 and a capacitor C16, a first end of the resistor R19 is connected with an output end of the output rectifying and filtering module, a second end of the resistor R19 is connected with a first end of the capacitor C16, a first end of the resistor R20 and a reference electrode of the controllable precision voltage regulator, respectively, a second end of the capacitor C16 is connected with a first end of the resistor R22, a cathode of the controllable precision voltage regulator is connected with a second end of the resistor R22 and a controlled end of the feedback unit, respectively, and an anode of the controllable precision voltage regulator and a second end of the resistor R20 are grounded.

6. The switching power supply according to claim 1, wherein the bleeder switch unit comprises a diode D2, a resistor R2, a resistor R3 and a switch Q1, the anode of the diode D2 is connected to the first output terminal of the control unit, the cathode of the diode D2 is connected to the first terminal of the resistor R2, the second terminal of the resistor R2 is respectively connected to the first terminal of the resistor R3 and the controlled terminal of the switch Q1, the input terminal of the switch Q1 is connected to the second terminal of the primary coil, and the output terminal of the switch Q1 is respectively connected to the second terminal of the resistor R3 and the input terminal of the variable frequency switch unit.

7. The switching power supply according to claim 6, wherein the bleeder switch unit further comprises a diode D1, a switching tube Q3 and a resistor R1, the second end of the resistor R2 is connected to the controlled end of the switching tube Q1 through the diode D1 and the resistor R1 which are connected in sequence, the controlled end of the switching tube Q3 is connected to the first end of the resistor R3, the input end of the switching tube Q3 is connected to the connection node of the diode D1 and the resistor R1, and the output end of the switching tube Q3 is connected to the output end of the switching tube Q1.

8. The switching power supply according to claim 1, wherein the variable frequency switching unit comprises a resistor R4, a resistor R6 and a switch tube Q2, the controlled terminal of the switch tube Q2 is connected to the first output terminal of the control unit through the resistor R4, the input terminal of the switch tube Q2 is connected to the output terminal of the bleeder switching unit, the output terminal of the switch tube Q2 is connected to the first terminal of the resistor R6, and the second terminal of the resistor R6 is grounded.

9. The switching power supply according to claim 8, wherein the switching control module further comprises an overload protection unit, a first end of the overload protection unit is connected to the second input end of the control unit, a second end of the overload protection unit is connected to the output end of the switching tube Q2, and a third end of the overload protection unit is grounded.

10. The switching power supply according to claim 1, wherein the switching control module further comprises a voltage division protection unit, the transformer is further provided with an auxiliary coil, a first end of the auxiliary coil is connected to the second output end of the input rectifying and filtering module, a first end of the voltage division protection unit is connected to the first end of the auxiliary coil, and a voltage division end of the voltage division protection unit is connected to the second output end of the control unit.