CN117674612A

CN117674612A - Power supply circuit and switching power supply

Info

Publication number: CN117674612A
Application number: CN202410139098.2A
Authority: CN
Inventors: 郑凌波; 巫雄; 张峰
Original assignee: Lii Semiconductor Inc
Current assignee: Lii Semiconductor Inc
Priority date: 2024-02-01
Filing date: 2024-02-01
Publication date: 2024-03-08
Anticipated expiration: 2044-02-01

Abstract

The invention discloses a power supply circuit and a switching power supply, wherein the switching power supply is provided with an alternating current input interface, and the power supply circuit comprises: the filter circuit is used for outputting the alternating voltage after the alternating voltage is filtered; the rectification circuit is used for converting the input alternating voltage and outputting direct voltage; the input end of the voltage conversion circuit is electrically connected with the output end of the rectifying circuit, and the voltage conversion circuit is used for carrying out step-up/step-down conversion on the direct-current voltage and then outputting a power supply voltage; the input end of the clamping circuit is electrically connected with the output end of the voltage conversion circuit, and the output end of the clamping circuit is electrically connected with a load; the clamping circuit is used for stabilizing the output voltage. The invention aims to improve the stability of a switching power supply circuit.

Description

Power supply circuit and switching power supply

Technical Field

The present invention relates to the field of power control technologies, and in particular, to a power circuit and a switching power supply.

Background

With the rapid development of electronic information technology, electronic equipment has a close relationship with people's work and life. Any electronic equipment is not separated from a reliable power supply, and the requirements on the power supply are also higher and higher, so that the switching power supply device is widely applied. In order to improve the transmission efficiency and the safety performance of the electric energy, the alternating current is adopted for transmission, and the alternating current is boosted, so that excessive loss of the electric energy in transmission is avoided. In addition, if the power grid is powered off, the network voltage using alternating current can be instantaneously reduced to zero, thereby avoiding additional damage. However, when a conductor is energized with a varying current, an electromagnetic field is generated around it and continuously diffuses away. Such diffused electromagnetic waves may have a certain influence on the operation of the surrounding devices, i.e. electromagnetic interference. Wherein, electromagnetic interference can cause damage to electronic equipment, influence its life-span and stability. For example, in the case of electronic devices such as computers, communication devices, medical devices, etc., the devices may be damaged by being disturbed by high voltage electromagnetic fields. This can lead to serious problems such as data loss, production pauses, medical accidents, etc., which directly affect the production or life of people.

Disclosure of Invention

The invention mainly aims to provide a power supply circuit which aims to improve the stability of a switch power supply circuit.

In order to achieve the above object, the present invention provides a power supply circuit applied to a switching power supply, the switching power supply being provided with an ac input interface, the power supply circuit comprising:

the input end of the filter circuit is electrically connected with the alternating current input interface, and the filter circuit is used for outputting the input alternating current voltage after filtering;

the input end of the rectifying circuit is electrically connected with the output end of the filter circuit, and the rectifying circuit is used for converting the input alternating voltage and then outputting direct voltage;

the input end of the voltage conversion circuit is electrically connected with the output end of the rectifying circuit, and the voltage conversion circuit is used for carrying out step-up/step-down conversion on the direct-current voltage and then outputting a power supply voltage;

the input end of the clamping circuit is electrically connected with the output end of the voltage conversion circuit, and the output end of the clamping circuit is electrically connected with a load; the clamping circuit is used for stabilizing the output voltage.

Preferably, the filter circuit further comprises a protection circuit, wherein an input end of the protection circuit is electrically connected with the alternating current input interface, and the protection circuit is used for limiting the current flowing through the protection circuit to be below a preset threshold current.

Preferably, the filter circuit further comprises a temperature detection circuit, wherein the input end of the temperature detection circuit is electrically connected with the output end of the protection circuit, and the temperature detection circuit is used for detecting the temperature of the power supply circuit and outputting a temperature detection signal.

Preferably, the filter circuit includes: the device comprises a fuse, an NTC resistor, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor, a third capacitor, a differential mode coil, a first common mode coil and a second common mode coil;

the first end of the fuse is electrically connected with the alternating current input positive electrode, and the second end of the fuse is electrically connected with the first end of the NTC resistor; the second end of the NTC resistor is electrically connected with the first end of the first resistor and the first end of the first coil winding of the differential mode coil; the second end of the first coil winding of the differential mode coil is electrically connected with the first end of the first capacitor, the first end of the second resistor and the first end of the first coil winding of the first common mode coil; a second end of the first coil winding of the first common mode coil is electrically connected with a first end of the first coil winding of the second common mode coil; the second end of the first coil winding of the second common-mode coil is electrically connected with the first end of the second capacitor and the positive electrode input end of the rectifying circuit; the second end of the second capacitor is electrically connected with the first end of the third capacitor and the grounding end; the second end of the third capacitor is electrically connected with the second end of the second coil winding of the second common mode coil and the negative electrode input end of the rectifying circuit; a first end of a second coil winding of the second common mode coil is electrically connected with a second end of a second coil winding of the first common mode coil; a first end of a second coil winding of the first common mode coil is electrically connected with a second end of the third resistor, a second end of the first capacitor and a second end of a second coil winding of the differential mode coil; the first end of the second coil winding of the differential mode coil is electrically connected with the second end of the first resistor and the alternating current input negative electrode.

Preferably, the rectifying circuit includes any one of a full-bridge inverter circuit and a push-pull inverter circuit.

Preferably, the rectifying circuit includes a transformer, a dc voltage output terminal, the transformer including a primary winding and a first secondary winding, a second secondary winding, the rectifying circuit including:

a main control circuit;

the first switch assembly is provided with two groups of first switch circuits which are connected in parallel, the controlled ends of the two groups of first switch circuits are respectively and electrically connected with the main control circuit, the input ends of the two groups of first switch circuits are connected with the second end of the first secondary coil, the first end of the first secondary coil is connected with the direct-current voltage output end, and the output ends of the two groups of first switch circuits are grounded;

the second switch assembly is provided with two groups of second switch circuits which are connected in parallel, the controlled ends of the two groups of second switch circuits are respectively and electrically connected with the main control circuit, the input ends of the two groups of second switch circuits are connected with the first ends of the second secondary side coils, the second ends of the second secondary side coils are connected with the direct-current voltage output ends, and the output ends of the two groups of second switch circuits are grounded;

the main control circuit is used for controlling the two groups of first switch circuits and the two groups of second switch circuits to work so as to enable the two groups of first switch circuits and the two groups of second switch circuits to convert alternating current voltage into direct current voltage through the input of the transformer.

Preferably, the first switching circuit comprises a fourth resistor, a fifth resistor, a sixth resistor and a switching tube; the first end of the fourth resistor is electrically connected with the direct-current voltage access end, and the second end of the fourth resistor is electrically connected with the input end of the switching tube; the first end of the fifth resistor is electrically connected with the output end of the main control circuit, and the second end of the fifth resistor is electrically connected with the controlled end of the switching tube; the first end of the sixth resistor is electrically connected with the second end of the fifth resistor, and the second end of the sixth resistor is electrically connected with the output end electrode of the switching tube;

the specific circuit structure of the second switch circuit is consistent with that of the first switch circuit.

In an embodiment, the rectifying circuit further includes a current detection circuit, where the current detection circuit includes a first current detection circuit and a second current detection circuit, output ends of the first current detection circuit and the second current detection circuit are respectively electrically connected with two groups of input ports of the main control circuit, and the first current detection circuit and the second current detection circuit are respectively disposed on the first secondary coil and the second secondary coil, and are used for detecting an output current of the rectifying circuit and outputting a current detection signal;

the main control circuit is used for receiving at least one current detection signal.

The invention also provides a switching power supply which comprises the power supply circuit according to any scheme.

The technical scheme of the invention adopts a power supply circuit. The power supply circuit further comprises a filter circuit, a rectifying circuit, a voltage conversion circuit and a clamping circuit. The filter circuit filters differential mode noise through adopting the differential mode coil and the first capacitor, and filters common mode noise through two groups of common mode coils, the second capacitor and the third capacitor, thereby achieving the technical effect of electromagnetic compatibility of alternating current input. And the alternating voltage after the filtering treatment is rectified and subjected to voltage conversion treatment by the rectification circuit and the voltage conversion circuit and then is output into the direct current supply voltage required by the load. And a clamping circuit is also adopted to protect the power supply circuit.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of an embodiment of a power circuit according to the present invention;

FIG. 2 is a schematic diagram of another embodiment of a power circuit according to the present invention;

FIG. 3 is a schematic diagram of a power circuit according to another embodiment of the present invention;

fig. 4 is a schematic diagram of a power circuit according to another embodiment of the invention.

In the figure:

10. a filter circuit; 20. a rectifying circuit; 21. a main control circuit; 22. a first switch assembly; 23. a second switch assembly; 30. a voltage conversion circuit; 40. a clamp circuit; FU, fuse; an NTC and a thermistor; R1-R6, a first resistor and a sixth resistor; C1-C3, first capacitor-third capacitor; FL1, differential mode coil; FL2, first common mode coil; FL3, second common mode coil.

The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.

Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.

Referring to fig. 1, the present invention proposes a power supply circuit, wherein the switching power supply is provided with an ac input interface, the power supply circuit comprising:

the input end of the filter circuit 10 is electrically connected with the alternating current input interface, and the filter circuit 10 is used for outputting the input alternating current voltage after filtering;

the input end of the rectifying circuit 20 is electrically connected with the output end of the filter circuit 10, and the rectifying circuit 20 is used for converting the input alternating voltage and outputting direct voltage;

the input end of the voltage conversion circuit 30 is electrically connected with the output end of the rectifying circuit 20, and the voltage conversion circuit 30 is used for performing step-up/step-down conversion on the direct-current voltage and then outputting a supply voltage;

a clamping circuit 40, wherein an input end of the clamping circuit 40 is electrically connected with an output end of the voltage conversion circuit 30, and an output end of the clamping circuit 40 is electrically connected with a load; the clamp circuit 40 is used to stabilize the output voltage.

The filter circuit 10 includes: fuse FU, NTC resistor, first resistor R1, second resistor R2, third resistor R3, first capacitor C1, second capacitor C2, third capacitor C3, differential mode coil FL1, first common mode coil FL2, second common mode coil FL3;

wherein a first end of the fuse FU is electrically connected with an alternating current input positive electrode, and a second end of the fuse FU is electrically connected with a first end of the NTC resistor; the second end of the NTC resistor is electrically connected with the first end of the first resistor R1 and the first end of the differential mode coil first coil winding; the second end of the differential mode coil first coil winding is electrically connected with the first end of the first capacitor C1, the first end of the second resistor R2 and the first end of the first common mode coil first coil winding; the second end of the first common mode coil first coil winding is electrically connected with the first end of the second common mode coil first coil winding; a second end of the first coil winding of the second common-mode coil is electrically connected with the first end of the second capacitor C2 and the positive input end of the rectifying circuit 20; the second end of the second capacitor C2 is electrically connected with the first end of the third capacitor C3 and the grounding end; a second end of the third capacitor C3 is electrically connected to a second end of the second coil winding of the second common mode coil and a negative input end of the rectifying circuit 20; the first end of the second common mode coil second coil winding is electrically connected with the second end of the first common mode coil second coil winding; the first end of the first common-mode coil second coil winding is electrically connected with the second end of the third resistor R3, the second end of the first capacitor C1 and the second end of the differential-mode coil second coil winding; the first end of the second coil winding of the differential mode coil is electrically connected with the second end of the first resistor R1 and the alternating current input negative electrode.

In the present embodiment, the filter circuit 10 may employ an EMI filter, that is, an electromagnetic interference filter. It can be understood that electromagnetic interference seriously jeopardizes the normal operation of the power supply system itself, and also causes electromagnetic pollution to the surrounding environment, and the electromagnetic interference can also feed into the power grid to affect the power supply quality and even jeopardize other electric equipment. Therefore, it must be suppressed to achieve electromagnetic compatibility performance. Referring to fig. 2, a set of EMI filter circuits 10 is shown. The first capacitor C1 is a power supply bridge capacitor, the differential mode coil FL1 and the first capacitor C1 are used for filtering differential mode noise, and the second resistor R2 and the third resistor R3 are discharge resistors of the first capacitor C1. The second capacitor C2 and the third capacitor C3 are power bypass capacitors. The first common-mode coil FL2 and the second common-mode coil FL3 are used together with the second capacitor C2 and the third capacitor C3 to filter out common-mode noise. In operation of a switching power supply with output isolation, common mode noise is typically coupled to the output through a transformer, and degradation of the output voltage must be suppressed. The common method is to bridge a group of capacitors, namely the second capacitor C2 and the third capacitor C3 in fig. 2, between two isolated grounds of the switching power supply, so as to filter out common mode noise of the output end, and when the common mode noise is coupled to the output end through the transformer, the common mode noise of the output end is greatly reduced by flowing back to the input ground through a capacitor bypass. Wherein, the value of the third capacitor C3 should be controlled within a certain range. An excessive value of the third capacitor C3 will result in an excessive input/output leakage current.

In the present embodiment, the rectifying circuit 20 may be any of a full-bridge inverter circuit and a push-pull inverter circuit. The rectification circuit 20 can convert the ac voltage output by the filter circuit 10 into a dc voltage to facilitate the subsequent voltage conversion, thereby realizing the power supply requirement of the load.

Alternatively, the voltage conversion circuit 30 may be implemented by a step-down type circuit (an average value of the output voltage is constantly lower than an average value of the input voltage), a step-up/step-down type circuit (an average value of the output voltage is constantly higher than an average value of the input voltage), a step-up type circuit (an average value of the output voltage is constantly higher than an average value of the input voltage), a hill type circuit (a step-up/step-down type circuit in which the input current and the output current are continuous and the harmonic component is small), and the like. It will be appreciated that the AC/DC conversion circuit is constituted by the rectifying circuit 20 together with the voltage conversion circuit 30. The input ac voltage is inverted by the rectifying circuit 20 to output a dc voltage, and the voltage is converted by the voltage converting circuit 30 to a voltage value according with the load power supply requirement. The clamping circuit 40 can be implemented by TVS, so as to suppress leakage inductance peak at the output end and protect the MOS. The TVS tube can be broken down rapidly by zener, and the high-resistance state is changed into the low-resistance state, so that peak voltage is split and clamped, each element in the circuit is protected from being damaged by instant leakage inductance current, and output voltage is stabilized.

In the present embodiment, the filter circuit 10 filters differential mode noise by using the differential mode coil FL1 and the first capacitor C1, and filters common mode noise by using the two sets of common mode coils and the second capacitor C2 and the third capacitor C3, thereby achieving the technical effect of electromagnetic compatibility of ac power input. The ac voltage after the filtering treatment is rectified and voltage-converted by the rectifying circuit 20 and the voltage-converting circuit 30, and then is output as the dc supply voltage required by the load. The clamp circuit 40 is also used to protect and stabilize the power supply circuit.

In an embodiment of the present invention, the filter circuit 10 further includes a protection circuit, an input end of the protection circuit is electrically connected to the ac input interface, and the protection circuit is configured to limit a current flowing through the protection circuit to be less than a preset threshold current.

In this embodiment, to ensure the safety of the filter circuit 10 when the ac voltage is applied, a protection circuit may be added to the filter circuit 10 to improve the safety of the circuit. The protection circuit can be realized by adopting a current limiting circuit, a fuse FU and the like. Specifically, taking fuse FU as an example, when a circuit fails or is abnormal, the current is increased continuously, and the increased current may damage some important devices in the circuit, and may burn out the circuit or even cause fire. If the fuse FU is correctly arranged in the circuit, the fuse FU blows and cuts off the current when the current abnormally rises to a certain height and heat, thereby playing a role in protecting the safe operation of the circuit. The protection circuit is arranged to limit the input alternating current to be below a preset threshold current, namely below a safe current, so that the safety and stability of the filter circuit 10 are improved.

In an embodiment of the present invention, the filter circuit 10 further includes a temperature detection circuit, an input end of the temperature detection circuit is electrically connected to an output end of the protection circuit, and the temperature detection circuit is used for detecting a temperature of the power supply circuit and outputting a temperature detection signal.

In this embodiment, the temperature detection circuit may be implemented using a detection circuit based on a thermosensitive device, for example, a resistor voltage division circuit based on an NTC resistor or an NTC probe, that is, a thermistor NTC; a resistor divider circuit based on a PTC resistor or a PTC probe. Alternatively, the temperature detection circuit may also be implemented using a temperature sensor, such as an infrared temperature sensor, a thermocouple temperature sensor, or the like. The temperature detection circuits may be multiple, and the multiple temperature detection circuits may be separately disposed at different positions in the power supply circuit, and the main control circuit 21 may determine multiple temperature values according to the multiple temperature detection signals, and calculate the actual environmental temperature through a preset temperature algorithm, such as an average value, a weighted calculation, and the like, so as to improve the accuracy of detecting the environmental temperature where the hanging device is located.

Optionally, in an embodiment, the main control circuit 21 may control the switch circuit to be in a closed state or an open state according to a preset control logic according to a temperature value obtained by the temperature detection signal, so that in practical application, the switch power supply is powered on or powered off. For example, during development, a developer sets a preset alarm temperature in the main control circuit 21 in advance, and if the current power supply circuit fails to generate heat, the ambient temperature, that is, the above-mentioned ambient temperature increases and exceeds the preset alarm temperature. In this way, in the actual working process, when the main control circuit 21 determines that the current ambient temperature reaches the preset alarm temperature according to the temperature detection signal, it is confirmed that the current power supply circuit fails to cause overheating, and the switch circuit is controlled to be in an on state, so that the switch power supply is powered down, and the working safety of the power supply circuit is effectively ensured.

In addition, the thermistor NTC may also be used for overcurrent protection in the power supply circuit. When the current exceeds a certain range, the resistance value of the NTC resistor can be rapidly increased, so that the current in the circuit is reduced, and the protection circuit is realized.

It should be understood that, in the rectifying circuit, when the switching components such as the MOS transistor are adopted, serious heat dissipation problems will occur in the MOS transistor circuit in the high-frequency on and off states.

In an embodiment of the present invention, the rectifying circuit 20 includes a transformer, and a dc voltage output terminal, the transformer includes a primary winding, a first secondary winding, and a second secondary winding, and the rectifying circuit 20 includes:

a main control circuit 21;

the first switch assembly 22 is provided with two groups of first switch circuits connected in parallel, the controlled ends of the two groups of first switch circuits are respectively and electrically connected with the main control circuit 21, the input ends of the two groups of first switch circuits are connected with the second end of the first secondary coil, the first end of the first secondary coil is connected with the direct-current voltage output end, and the output ends of the two groups of first switch circuits are grounded;

the second switch assembly 23, the second switch assembly 23 is provided with two groups of second switch circuits connected in parallel, the controlled ends of the two groups of second switch circuits are respectively connected with the main control circuit 21 electrically, the input ends of the two groups of second switch circuits are connected with the first ends of the second secondary windings, the second ends of the second secondary windings are connected with the direct-current voltage output end, and the output ends of the two groups of second switch circuits are grounded;

the main control circuit 21 is configured to control the two sets of the first switch circuits and the two sets of the second switch circuits to operate, so that the two sets of the first switch circuits and the two sets of the second switch circuits convert an ac voltage into a dc voltage through the transformer input.

The first switching circuit comprises a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a switching tube; the first end of the fourth resistor R4 is electrically connected with the direct-current voltage access end, and the second end of the fourth resistor R4 is electrically connected with the input end of the switching tube; the first end of the fifth resistor R5 is electrically connected with the output end of the main control circuit 21, and the second end of the fifth resistor R5 is electrically connected with the controlled end of the switching tube; the first end of the sixth resistor R6 is electrically connected with the second end of the fifth resistor R5, and the second end of the sixth resistor R6 is electrically connected with the output end of the switching tube;

In the present embodiment, it is to be understood that the rectifying circuit 20 employed may be any one of a push-pull inverter circuit, a full-bridge inverter circuit, and the like. The transformer can adopt a step-up transformer and a step-down transformer, and the voltage is regulated by changing the turn ratio of a primary coil and a secondary coil of the transformer. In practical application, a certain adjustment can be made to the transformer according to practical requirements. The transformer secondary winding is disposed in the rectifying circuit 20. In order to realize the matching of the transformer and the rectifying circuit 20, the rectified ac is transformed and output, and the rectifying circuit 20 needs to be provided with a first secondary coil and a second secondary coil. Specifically, a first end of the first secondary coil is connected with the direct-current voltage output end, and a second end of the first secondary coil is connected with the first switch circuit; the second end of the second secondary winding is connected with the direct-current voltage output end, and the first end of the second secondary winding is connected with the second switch circuit. The main control circuit 21 outputs corresponding control signals to control the opening/closing of the two groups of first switch circuits and the two groups of second switch circuits, so that the connection and disconnection of the circuits are realized.

In this embodiment, the main control circuit 21 may be implemented by an MCU (Microcontroller Unit, micro control unit), DSP (Digital Signal Process, digital signal processing Chip), FPGA (Field Programmable Gate Array, programmable gate array Chip), SOC (System On Chip), or the like. The control signal output by the main control circuit 21 may be a PWM control signal, and the control function of the main control circuit 21 in the rectifying circuit 20 is achieved by controlling the opening/closing of the switching circuit. In order to realize the power supply input of the main control circuit, a group of batteries can be additionally arranged to meet the direct current power supply requirement of the main control circuit. In addition, the battery is charged after the voltage conversion at the time of input of the alternating current circuit.

In this embodiment, the first switch component 22 may be formed by two sets of switch circuits connected in parallel, where the switch circuits may be implemented by using switching transistors such as MOS transistors, IGBT transistors, thyristors, triodes, power transistors, and the like. Specifically, a MOS transistor is taken as an example. Two sets of MOS tube circuits are arranged in the first switch assembly 22 in parallel, and the grid electrodes of the MOS tubes in each set of MOS tube circuits are respectively and electrically connected with the main control circuit 21, wherein the grid electrodes of the MOS tubes are in one-to-one correspondence with the signal output ends of the main control circuit 21, and the MOS tubes are opened or closed according to the control signals transmitted by the main control circuit 21 so as to realize the connection and disconnection of the circuits. In the practical application process, in order to ensure the frequency of opening or closing the MOS transistor circuits, the main control circuit 21 generally sets a staggered opening frequency or closing frequency for each group of MOS transistor circuits. Taking the first switch assembly 22 as an example, two sets of parallel MOS transistor circuits are provided. The main control circuit 21 outputs two groups of control signals with the same frequency according to the output frequency required by the alternating voltage of the rectifying circuit 20 by presetting two groups of PWM control signals of the first switch components 22, and the control signals with the high level in a dislocation state in the same time domain are used for controlling the two groups of parallel MOS tube circuits to be sequentially opened or sequentially closed, so that the MOS tube circuits only need 1/2 of the opening frequency or the closing frequency required by the original group of MOS tube circuits. That is, the frequency of opening or closing the original MOS tube circuits is 1MHz, and after two MOS tube circuits which are opened or closed according to the control signal of the main control circuit 21 are arranged, the frequency of opening or closing any MOS tube circuit is 500 MHz. Specifically, the duration of the high level of the PWM control signal outputted from the control circuit is shortened, and the duration of the low level is lengthened. In a certain time, the control signal which is originally in a group of switch circuits and appears twice high level is changed into the control signal which appears once high level. The two groups of switch circuits are controlled by the main control circuit 21, so that the current sequentially passes through the different groups of switch circuits within a certain time.

In the rectifying circuit 20 of the present embodiment, the design concept and implementation manner adopted by the second switch assembly 23 are basically identical to those of the first switch assembly 22, and are only opposite to the first switch assembly 22 in the setting direction, so that the description thereof will be omitted here.

In the present embodiment, the main control circuit 21 controls the opening/closing of each group of switching circuits in the first switching element 22 and the second switching element 23 in the rectifying circuit 20 by outputting a control signal of a preset frequency, and forms a state of sequentially opening/closing, so that the number of times of opening/closing the switching circuits in a certain period of time is greatly reduced. The method is characterized in that the first switch assembly 22 and the second switch assembly 23 control two groups of currents with opposite directions, the currents flow through the secondary coil of the voltage device, the process of converting alternating current into direct current is realized, and the heating problem caused by high-frequency opening/closing of the MOS tube is effectively solved.

In an embodiment of the present invention, the rectifying circuit 20 further includes a current detection circuit, where the current detection circuit includes a first current detection circuit and a second current detection circuit, the output ends of the first current detection circuit and the second current detection circuit are respectively electrically connected to two sets of input ports of the main control circuit 21, and the first current detection circuit and the second current detection circuit are respectively disposed on the first secondary side coil and the second secondary side coil and are used for detecting an output current of the rectifying circuit 20 and outputting a current detection signal;

wherein the master circuit 21 is configured to receive at least one of the current detection signals.

In this embodiment, the current detection circuit may be implemented by using a resistive shunt, a current transformer, a hall current sensor, a rogowski coil current sensor, a fluxgate current sensor, an optical fiber current sensor, and the like. Since the rectifying circuit 20 is provided with the first switch assembly 22 and the second switch assembly 23 in the present embodiment, two sets of current detection circuits corresponding to the first switch assembly 22 and the second switch assembly 23 are required to be provided. Specifically, a hall current detection chip is taken as an example of the current detection circuit. In the actual detection process, the first secondary coil and the second secondary coil of the inverter circuit transformer generate magnetic fields with corresponding intensities when the current changes. The hall current detection chip obtains the specific condition of the ac power input of the rectifying circuit 20 by detecting the change condition of the magnetic field generated by the transformer, for example, the information of the intensity and time of the ac power input can be detected by the hall current detection chip and transmitted to the main control circuit 21. The current detection of the alternating current in the rectifying circuit 20 is realized, and the main control circuit 21 can transmit the received detection information to a display component, a prompting circuit and the like, so that a user can more intuitively know the current condition in the rectifying circuit 20.

The invention also proposes a switching power supply comprising all the embodiments of the power supply circuit described above. It should be noted that, because the switching power supply of the present invention is based on the above-mentioned power supply circuit, the embodiments of the switching power supply of the present invention include all the technical schemes of all the embodiments of the above-mentioned power supply circuit, and the achieved technical effects are identical, and are not described herein again.

The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.

Claims

1. A power supply circuit for a switching power supply, the switching power supply being provided with an ac input interface, the power supply circuit comprising:

2. The power circuit of claim 1, wherein the filter circuit further comprises a protection circuit having an input electrically connected to the ac input interface, the protection circuit configured to limit current flowing through itself to below a predetermined threshold current.

3. The power supply circuit according to claim 2, wherein the filter circuit further comprises a temperature detection circuit, an input terminal of the temperature detection circuit is electrically connected to an output terminal of the protection circuit, and the temperature detection circuit is used for detecting the temperature of the power supply circuit and outputting a temperature detection signal.

4. The power supply circuit of claim 3, wherein the filter circuit comprises: the device comprises a fuse, an NTC resistor, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor, a third capacitor, a differential mode coil, a first common mode coil and a second common mode coil;

5. The power supply circuit according to claim 1, wherein the rectifying circuit includes any one of a full-bridge inverter circuit and a push-pull inverter circuit.

6. The power supply circuit of claim 1, wherein the rectifying circuit comprises a transformer, a dc voltage output, the transformer comprising a primary winding and a first secondary winding, a second secondary winding, the rectifying circuit comprising:

a main control circuit;

the second switch assembly is provided with two groups of second switch circuits which are connected in parallel, the controlled ends of the two groups of second switch circuits are respectively and electrically connected with the main control circuit, the input ends of the two groups of second switch circuits are connected with the first ends of the second secondary side coils, the second ends of the second secondary side coils are connected with the direct-current voltage output end, and the output ends of the two groups of second switch circuits are grounded;

7. The power supply circuit of claim 6, wherein the first switching circuit comprises a fourth resistor, a fifth resistor, a sixth resistor, a switching tube; the first end of the fourth resistor is electrically connected with the direct-current voltage access end, and the second end of the fourth resistor is electrically connected with the input end of the switching tube; the first end of the fifth resistor is electrically connected with the output end of the main control circuit, and the second end of the fifth resistor is electrically connected with the controlled end of the switching tube; the first end of the sixth resistor is electrically connected with the second end of the fifth resistor, and the second end of the sixth resistor is electrically connected with the output end electrode of the switching tube;

8. The power supply circuit according to claim 6, wherein the rectifying circuit further comprises a current detection circuit, the current detection circuit comprises a first current detection circuit and a second current detection circuit, the output ends of the first current detection circuit and the second current detection circuit are respectively and electrically connected with two groups of input ports of the main control circuit, and the first current detection circuit and the second current detection circuit are respectively arranged on the first secondary coil and the second secondary coil and are used for detecting the output current of the rectifying circuit and outputting a current detection signal;

9. A switching power supply comprising a power supply circuit as claimed in any one of claims 1 to 8.