CN108370214B - Switching power supply and control method thereof - Google Patents

Switching power supply and control method thereof Download PDF

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Publication number
CN108370214B
CN108370214B CN201680073601.2A CN201680073601A CN108370214B CN 108370214 B CN108370214 B CN 108370214B CN 201680073601 A CN201680073601 A CN 201680073601A CN 108370214 B CN108370214 B CN 108370214B
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voltage
output voltage
inductor
pass filter
output
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CN108370214A (en
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唐样洋
张臣雄
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/14—Arrangements for reducing ripples from dc input or output

Abstract

A switching power supply and a control method thereof, the switching power supply comprising: the circuit comprises a switch circuit (1), a controller (2), a driver (3) and a fourth-order low-pass filter (4), wherein the fourth-order low-pass filter has a negative coupling characteristic; the switching circuit receives an input voltage and outputs the input voltage to the fourth-order low-pass filter; the fourth-order low-pass filter outputs the first output voltage and the second output voltage to the controller; the controller receives the reference voltage, generates a modulation pulse based on the first output voltage, the second output voltage and the reference voltage, and outputs the modulation pulse to the driver; the driver outputs the modulation pulse to the switching circuit to control the switching circuit by the modulation pulse. The ripple of the output voltage can be reduced by a fourth order low pass filter having a negative coupling characteristic.

Description

Switching power supply and control method thereof
Technical Field
The embodiment of the invention relates to the technical field of electronics, in particular to a switching power supply and a control method thereof.
Background
With the rapid development of electronic technology, electronic devices are increasingly closely related to the work and life of people, and the electronic devices cannot be powered by reliable power supplies. However, the switching power supply is a high-frequency power conversion device for converting an input voltage into a stable voltage required by a user terminal, and is widely used in almost all electronic devices due to its small size, light weight and high efficiency, and thus, the design of the switching power supply is receiving attention.
As shown in fig. 1(a), the switching power supply includes a first MOS (Metal oxide Semiconductor) transistor Q1A second MOS transistor Q2 A signal generator 1 and a low-pass filter 2. Wherein, the first MOS transistor Q1Source s of1Connected with an external power supply VDD for providing input voltage to the switching power supply, a first MOS transistor Q1Drain electrode of (d)1And a second MOS transistor Q2Drain electrode of (d)2Connected, second MOS transistor Q2Source s of2Grounded, first MOS transistor Q1Grid g of1And a second MOS transistor Q2Of a grid electrodeg2Respectively connected with the output end 11 of the signal generator 1, a first MOS transistor Q1Drain electrode of (d)1And a second MOS transistor Q2Drain electrode of (d)2And also to the input of the low-pass filter 2, respectively. In addition, the low-pass filter 2 may be a second-order low-pass filter or a fourth-order low-pass filter. When the low pass filter 2 is a second-order low pass filter, as shown in fig. 1(b), the low pass filter 2 may include a first inductor L1And a first capacitor C1First inductance L1As an input terminal of the low-pass filter 2, a first inductor L1And the other end of the first capacitor C1Is connected to a first capacitor C1And the other end of the same is grounded. When the low pass filter 2 is a fourth order low pass filter, as shown in fig. 1(c), the low pass filter 2 includes a second inductor L2A third inductor L3A second capacitor C2And a third capacitance C3Second inductance L2As an input terminal of the low-pass filter 2, a second inductor L2The other end of the first capacitor is respectively connected with a second capacitor C2And a third inductance L3Is connected to a second capacitor C2Is grounded, and a third inductor L3The other end of which is connected to a third capacitor C3Is connected to a third capacitor C3And the other end of the same is grounded.
When the external power supply is switched on and the signal generator generates a pulse signal, the first MOS tube is controlled to be switched on and the second MOS tube is controlled to be switched off during the high level period of the pulse signal, so that the input voltage provided by the external power supply is transmitted to the low-pass filter, the input voltage is filtered through the low-pass filter, and the direct current output voltage is obtained and is used for supplying power to loads such as electronic equipment and the like. Meanwhile, the low-pass filter can also be charged based on the input voltage. And during the low level period of the pulse signal, the first MOS tube is controlled to be switched off, and the second MOS tube is controlled to be switched on, so that the discharge is carried out through the low-pass filter, and the power supply is carried out on the load.
The above technical scheme has at least the following problems: since the cut-off frequency of the second-order low-pass filter or the fourth-order low-pass filter is low, the attenuation of the second-order low-pass filter or the fourth-order low-pass filter to the input voltage is small, and further, during the discharge period of the second-order low-pass filter or the fourth-order low-pass filter, the ripple of the output voltage is high, wherein the ripple refers to an alternating current component superposed on the stable amount of the direct current output voltage.
Disclosure of Invention
In order to reduce the ripple of the output voltage, embodiments of the present invention provide a switching power supply and a control method thereof. The technical scheme is as follows:
in a first aspect, a switching power supply is provided, which includes: the four-order low-pass filter comprises a first inductor, a second inductor, a first capacitor and a second capacitor, wherein the different name end of the first inductor is respectively connected with the different name end of the second inductor and one end of the first capacitor, and the same name end of the second inductor is connected with one end of the second capacitor so as to enable the first inductor and the second inductor to form an inductor with a negative coupling characteristic;
the switch circuit receives an input voltage and outputs the input voltage to the fourth-order low-pass filter;
the fourth-order low-pass filter outputs a first output voltage and a second output voltage to the controller, wherein the first output voltage is output by a first output end of the fourth-order low-pass filter based on the input voltage, and the second output voltage is output by a second output end of the fourth-order low-pass filter based on the input voltage;
the controller receives a reference voltage, generates a modulation pulse based on the first output voltage, the second output voltage and the reference voltage, and outputs the modulation pulse to the driver;
the driver outputs the modulation pulse to the switching circuit to control the switching circuit by the modulation pulse.
Since the switching circuit receives an input voltage, the input voltage is input to the fourth-order low-pass filter through the switching circuit, and a high-frequency signal in the input voltage is attenuated by the fourth-order low-pass filter. And because the first inductor and the second inductor in the fourth-order low-pass filter can form an inductor with a negative coupling characteristic, that is, the fourth-order low-pass filter has a negative coupling characteristic, high-frequency signals in the input voltage can be further attenuated through the negative coupling characteristic of the fourth-order low-pass filter, the attenuation value of the high-frequency signals in the input voltage is improved, alternating current components in the input voltage are restrained, and then ripples of the output voltage of the switching power supply are reduced.
With reference to the first aspect, in a first possible implementation manner of the first aspect, the switch circuit includes: the MOS transistor comprises a first Metal Oxide Semiconductor (MOS) transistor and a second MOS transistor;
the first MOS tube receives the input voltage and outputs the input voltage to the second MOS tube and the fourth-order low-pass filter;
the first MOS tube and the second MOS tube respectively receive the modulation pulse output by the driver.
The output end of the fourth-order low-pass filter can be connected with a load, when the first MOS tube is connected and the second MOS tube is disconnected, the input voltage provided by the external power supply can be input into the fourth-order low-pass filter through the first MOS tube, so that the load is supplied with power through the output of the fourth-order low-pass filter, and meanwhile, the fourth-order low-pass filter is charged through the input voltage. When the first MOS tube is turned off and the second MOS tube is turned on, the input voltage cannot be input into the fourth-order low-pass filter through the first MOS tube, and at the moment, the fourth-order low-pass filter can discharge through the second MOS tube to supply power to the load.
With reference to the first aspect, in a possible implementation manner of the first aspect, the switch circuit includes: a third MOS tube and a diode;
the third MOS tube receives the input voltage and the modulation pulse output by the driver, and the third MOS tube outputs the input voltage to the diode and the fourth-order low-pass filter.
With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the controller includes: a signal generator, an adder, a comparator and an error amplifier;
the signal generator outputs a generated first pulse signal to the adder, the fourth-order low-pass filter outputs the first output voltage to the adder, the adder adds the first pulse signal and the first output voltage to obtain a second pulse signal, and the second pulse signal is output to the comparator;
the fourth-order low-pass filter outputs the second output voltage to the error amplifier, the error amplifier also receives the reference voltage, and the error amplifier performs error amplification on the second output voltage and the reference voltage to obtain error amplification voltage;
the error amplifier outputs the error amplified voltage to the comparator, the comparator compares the second pulse signal with the error amplified voltage to generate the modulated pulse, and the comparator outputs the modulated pulse to the driver.
With reference to any one possible implementation manner of the first aspect to the second possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the fourth-order low-pass filter includes: the circuit comprises a first inductor, a second inductor, a first capacitor and a second capacitor;
the dotted terminal of the first inductor receives the input voltage output by the switch circuit, the synonym terminal of the first inductor outputs the first output voltage to one terminal of the first capacitor, the other terminal of the first capacitor is grounded, and the first output voltage is obtained by dividing the input voltage by the first inductor;
the synonym end of the first inductor also outputs the first output voltage to the synonym end of the second inductor, the synonym end of the second inductor outputs the second output voltage to one end of the second capacitor, the other end of the second capacitor is grounded, and the second output voltage is obtained by dividing the first output voltage by the second inductor;
the different-name end of the first inductor also outputs the first output voltage to the controller, and the same-name end of the second inductor also outputs the second output voltage to the controller.
When the input voltage is filtered by the fourth-order low-pass filter, the high-frequency signal of the input voltage is attenuated by the first inductor and the first capacitor, and then is further attenuated by the second inductor and the second capacitor. Because the first inductor and the second inductor can form a negative coupling inductor, the equivalent inductance value of the first inductor is smaller after the negative coupling treatment, and the total equivalent inductance value of the fourth-order low-pass filter can be reduced. And because the reduction of the total equivalent inductance value of the fourth-order low-pass filter correspondingly improves the cut-off frequency of the fourth-order low-pass filter, the fourth-order low-pass filter subjected to negative coupling processing can further attenuate high-frequency signals in the input voltage, inhibit alternating current components in the input voltage and further reduce ripples in the output voltage.
In addition, the first output voltage is obtained after the input voltage passes through the first inductor, the second output voltage is obtained after the input voltage passes through the first inductor, the first capacitor and the second inductor, and the first inductor and the first capacitor in the fourth-order low-pass filter can be equivalent to a high-pass link, that is, the first inductor and the first capacitor can be equivalent to a high-pass link, so that the response speed of the first output voltage is greater than that of the second output voltage. The controller respectively processes the first output voltage and the second output voltage through two lines, namely the first output voltage is processed while the second output voltage is processed, a signal fed back to the controller by the first output voltage is a high-frequency component feedback signal, and a signal fed back to the controller by the second output voltage is a direct-current part signal, so that the processing speed of the high-frequency component feedback signal is ensured while the direct-current part signal feedback processing is ensured, the speed of generating modulation pulses by the controller is increased, and the response speed of the switching power supply is also increased.
In a second aspect, there is provided a method for controlling a switching power supply according to any one of the above first to third possible implementation manners of the first aspect, the method including:
detecting, by the controller, the first output voltage and the second output voltage when the input voltage and the reference voltage are turned on;
generating, by the controller, the modulation pulse based on the first output voltage, the second output voltage, and the reference voltage;
outputting, by the controller, the modulated pulses to the driver;
controlling the switching circuit based on the modulation pulse when the modulation pulse is received by the driver.
When the input voltage and the reference voltage are switched on, the first output voltage and the second output voltage can be detected through the controller, so that the modulation pulse is generated through the controller based on the first output voltage, the second output voltage and the reference voltage provided by the reference power supply, and the driver controls the switching circuit based on the modulation pulse, so that the function of converting the electric energy of the switching power supply is realized. The high-frequency signal in the input voltage can be further attenuated by the negative coupling characteristic of the fourth-order low-pass filter, so that the attenuation value of the high-frequency signal in the input voltage is improved, the alternating-current component in the input voltage is restrained, and the ripple of the output voltage of the switching power supply is further reduced.
With reference to the second aspect, in a first possible implementation manner of the second aspect, the switch circuit includes a first MOS transistor and a second MOS transistor;
the controlling the switching circuit based on the modulation pulse includes:
during the high level period of the modulation pulse, controlling the first MOS tube to be conducted and controlling the second MOS tube to be switched off;
and during the low level period of the modulation pulse, the first MOS tube is controlled to be switched off, and the second MOS tube is controlled to be switched on.
With reference to the second aspect, in a possible implementation manner of the second aspect, the switch circuit includes a third MOS transistor and a diode;
the controlling the switching circuit based on the modulation pulse includes:
during the high level period of the modulation pulse, controlling the third MOS tube to be conducted and controlling the diode to be switched off;
and during the low level of the modulation pulse, the third MOS tube is controlled to be switched off, and the diode is controlled to be switched on.
With reference to the second aspect or the first possible implementation manner of the second aspect, in a second possible implementation manner of the second aspect, the controller includes a signal generator, an adder, a comparator, and an error amplifier;
the generating, by the controller, the modulated pulse based on the first output voltage, the second output voltage, and the reference voltage includes:
determining, by the error amplifier, an error amplified voltage based on the second output voltage and the reference voltage;
generating a first pulse signal through the signal generator, and adding the first pulse signal and the first output voltage through the adder to obtain a second pulse signal;
generating the modulation pulse by the comparator based on the error amplification voltage and the second pulse signal.
When the input voltage is filtered by the fourth-order low-pass filter, the high-frequency signal of the input voltage is attenuated by the first inductor and the first capacitor, and then is further attenuated by the second inductor and the second capacitor. Because the first inductor and the second inductor can form a negative coupling inductor, the equivalent inductance value of the first inductor is smaller after the negative coupling treatment, and the total equivalent inductance value of the fourth-order low-pass filter can be reduced. And because the reduction of the total equivalent inductance value of the fourth-order low-pass filter correspondingly improves the cut-off frequency of the fourth-order low-pass filter, the fourth-order low-pass filter subjected to negative coupling processing can further attenuate high-frequency signals in the input voltage, inhibit alternating current components in the input voltage and further reduce ripples in the output voltage.
In addition, the first output voltage is obtained after the input voltage passes through the first inductor, the second output voltage is obtained after the input voltage passes through the first inductor, the first capacitor and the second inductor, and the first inductor and the first capacitor in the fourth-order low-pass filter can be equivalent to a high-pass link, that is, the first inductor and the first capacitor can be equivalent to a high-pass link, so that the response speed of the first output voltage is greater than that of the second output voltage. The controller respectively processes the first output voltage and the second output voltage through two lines, namely the first output voltage is processed while the second output voltage is processed, a signal fed back to the controller by the first output voltage is a high-frequency component feedback signal, and a signal fed back to the controller by the second output voltage is a direct-current part signal, so that the processing speed of the high-frequency component feedback signal is ensured while the direct-current part signal feedback processing is ensured, the speed of generating modulation pulses by the controller is increased, and the response speed of the switching power supply is also increased.
The technical scheme provided by the embodiment of the invention has the beneficial effects that: in the embodiment of the invention, since the switch circuit receives the input voltage and the switch circuit can output the input voltage to the fourth-order low-pass filter, after the input voltage is input to the fourth-order low-pass filter through the switch circuit, the fourth-order low-pass filter can attenuate a high-frequency signal in the input voltage. The first inductor and the second inductor in the fourth-order low-pass filter can form an inductor with a negative coupling characteristic, that is, the fourth-order low-pass filter has a negative coupling characteristic, so that the high-frequency signal in the input voltage can be further attenuated through the negative coupling characteristic of the fourth-order low-pass filter, the attenuation value of the high-frequency signal in the input voltage is improved, the alternating current component in the input voltage is restrained, and the ripple of the output voltage of the switching power supply is further reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1(a) is a schematic structural diagram of a switching power supply provided in the prior art;
FIG. 1(b) is a schematic diagram of a second-order low-pass filter provided in the prior art;
FIG. 1(c) is a schematic diagram of a fourth-order low-pass filter provided in the prior art,
Fig. 2 is a schematic structural diagram of a first switching power supply according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a second switching power supply according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a third switching power supply according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a fourth switching power supply according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a fifth switching power supply according to an embodiment of the present invention;
fig. 7 is a flowchart of a method for controlling a switching power supply according to an embodiment of the present invention;
fig. 8 is a flowchart of another method for controlling a switching power supply according to an embodiment of the present invention.
Description of the prior art figures:
Q1: first MOS transistor, Q2: second MOS transistor, 1: signal generator, 2: a low-pass filter;
s1: source electrode of the first MOS transistor, d1: drain electrode of the first MOS transistor, g1: grid of the first MOS transistor, s2: source electrode of the second MOS transistor, d2: drain electrode of the second MOS transistor, g2: a grid electrode of the second MOS tube;
VDD: external power supply, 11: an output terminal of the signal generator;
L1: a first inductor, C1: a first capacitor;
L2: a second inductance, L3: third inductance, C2: a second capacitor, C3: and a third capacitor.
Description of the invention:
1: switching circuit, 2: controller, 3: driver, 4: fourth-order low-pass filter, VDD: external power supply, VREF: a reference power supply;
11: first input terminal of switching circuit, 12: output terminal of switching circuit, 13: a second input terminal of the switching circuit;
21: first input of controller, 22: second input of controller, 23: third input of controller, 24: an output of the controller;
31: input of driver, 32: output terminal of driver
41: input of fourth order low pass filter, 42: first output terminal of fourth order low pass filter, 43: a second output terminal of the fourth order low pass filter;
Q1: first MOS transistor, Q2: a second MOS transistor;
s1: source electrode of the first MOS transistor, d1: drain electrode of the first MOS transistor, g1: grid of the first MOS transistor, s2: source electrode of the second MOS transistor, d2: drain electrode of the second MOS transistor, g2: a grid electrode of the second MOS tube;
Q3: third MOS transistor, D: a diode;
S3: source electrode of the third MOS transistor, d3: drain electrode of the third MOS transistor, g3: a grid electrode of the third MOS tube;
25: signal generator, 26: adder, 27: comparator, 28: an error amplifier;
L1: a first inductor, L2: a second inductance, C1: a first capacitor, C2: a second capacitance.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 2 is a schematic structural diagram of a switching power supply according to an embodiment of the present invention. Referring to fig. 2, the switching power supply includes: the switching circuit 1, the controller 2, the driver 3 and the fourth order low pass filter 4, see fig. 6, the fourth order low pass filter 4 comprising a first inductance L1A second inductor L2A first capacitor C1And a second capacitor, a first inductor L1The different name end of the first inductor is respectively connected with the second inductor L2And a first capacitor C1Is connected to a second inductance L2End of same name and second capacitor C2Is connected to connect the first inductor L with one end1And a second inductance L2Forming an inductor with negative coupling characteristics;
the switch circuit 1 receives an input voltage and outputs the input voltage to the fourth-order low-pass filter 4;
the fourth-order low-pass filter 4 outputs a first output voltage and a second output voltage to the controller 2, the first output voltage being a voltage output by a first output terminal of the fourth-order low-pass filter 4 based on the input voltage, the second output voltage being a voltage output by a second output terminal of the fourth-order low-pass filter 4 based on the input voltage;
the controller 2 receives the reference voltage, generates a modulation pulse based on the first output voltage, the second output voltage and the reference voltage, and outputs the modulation pulse to the driver 3;
the driver 3 outputs the modulation pulse to the switching circuit 1 to control the switching circuit 1 by the modulation pulse.
Wherein, the first input terminal 11 of the switch circuit 1 is connected with an external power supply VDDThe power supply VDD is connected and used for providing input voltage for the switching power supply; the output 12 of the switching circuit 1 is connected to the input 41 of the fourth order low-pass filter 4, the first output 42 of the fourth order low-pass filter 4 is connected to the first input 21 of the controller 2, the second output 43 of the fourth order low-pass filter 4 is connected to the second input 22 of the controller 2, and the third input 23 of the controller 2 is connected to the reference supply VREFConnected, reference source VREFFor providing a reference voltage to the controller 2; the controller 2 is configured to generate a modulation pulse based on a first output voltage, a second output voltage and a reference voltage, where the first output voltage is a voltage output by a first output terminal 42 of the fourth-order low-pass filter 4, and the second output voltage is a voltage output by a second output terminal 43 of the fourth-order low-pass filter 4; the output 24 of the controller 2 is connected to the input 31 of the driver 3, the output 32 of the driver 3 is connected to the second input 13 of the switching circuit 1, and the driver 3 is adapted to control the switching circuit 1 based on the modulation pulses generated by the controller 2.
In the embodiment of the present invention, since the first input terminal 11 of the switch circuit 1 is connected to the external power supply VDD, and the output terminal 12 of the switch circuit 1 is connected to the input terminal 41 of the fourth-order low-pass filter 4, the input voltage provided by the external power supply VDD can be input into the fourth-order low-pass filter 4 through the switch circuit 1, and the high-frequency signal in the input voltage is attenuated by the fourth-order low-pass filter 4. And due to the first inductance L in the fourth order low pass filter 41And a second inductance L2An inductor with negative coupling characteristics can be formed, that is, the fourth-order low-pass filter 4 has negative coupling characteristics, so that the high-frequency signal in the input voltage can be further attenuated through the negative coupling characteristics of the fourth-order low-pass filter 4, the attenuation value of the high-frequency signal in the input voltage is improved, the alternating-current component in the input voltage is restrained, and the ripple of the output voltage of the switching power supply is further reduced.
Because the switching power supply is based on the on and off of the switching circuit 1, the input voltage provided by the external power supply VDD is converted into the stable voltage required by the load, that is, the switching power supply operates in the on-off state, and because the reference power supply V is usedREFThe reference voltage is determined based on the voltage required by the load, so that when the external power supply VDD and the reference power supply V are connectedREFThe controller 2 may detect the first output voltage and the second output voltage, generate a modulation pulse based on the first output voltage, the second output voltage, and the reference voltage, and output the modulation pulse to the driver 3. Since the output end of the driver 3 is connected to the second input end 13 of the switch circuit 1, the driver 3 can output the modulated pulse to the switch circuit 1, so as to control the switch circuit 1, thereby implementing the function of converting the electric energy of the switching power supply.
Wherein, the external power VDD and the reference power V are connectedREFIn the embodiment of the present invention, the external power source and the reference power source may be turned on manually by a user, or may be turned on intelligently by a certain control strategy.
It should be noted that the external power source may be an independent power supply device, such as a storage battery, and the reference voltage provided by the reference power source may be equal to the voltage required by the load, which is not specifically limited in this embodiment of the present invention.
In addition, the load may include an electronic device, a communication device, and the like, and of course, the load may also be a storage battery, which is not specifically limited in this embodiment of the present invention.
It should also be noted that the second output terminal 43 of the fourth-order low-pass filter 4 may also be connected to a load, so that the load is supplied with the second output voltage.
Referring to fig. 3, the switching circuit 1 includes: first MOS transistor Q1And a second MOS transistor Q2；
First MOS transistor Q1Receiving input voltage and outputting the input voltage to the second MOS transistor Q2And a fourth order low pass filter 4;
first MOS transistor Q1And a second MOS transistor Q2Respectively receive the modulated pulses output by the driver 3.
Wherein, the first MOS transistor Q1Source s of1Receiving an input voltage provided by an external power supply,first MOS transistor Q1Drain electrode of (d)1Outputting the input voltage to a second MOS transistor Q2Drain electrode of (d)2And a fourth order low pass filter 4; first MOS transistor Q1Grid g of1And a second MOS transistor Q2Grid g of2Respectively receive the modulated pulses output by the driver 3. That is, the first MOS transistor Q1Source s of1Connected with an external power supply VDD, a first MOS tube Q1Drain electrode of (d)1And a second MOS transistor Q2Drain electrode of (d)2Connected, first MOS transistor Q1Drain electrode of (d)1And drain electrode d of second MOS tube2And also respectively connected to the input terminals 41 of the fourth order low pass filter 4; first MOS transistor Q1Grid g of1And a second MOS transistor Q2Grid g of2Respectively connected with the output end 32 of the driver 3, a second MOS transistor Q2Source s of2And (4) grounding.
It should be noted that the first MOS transistor Q1Can be a P-type MOS tube and a second MOS tube Q2Can be an N-type MOS transistor, and the first MOS transistor Q1Can be used as a pull-up switch of the switching power supply, and the second MOS tube Q2The pull-down switch may be used as the pull-down switch of the switching power supply, which is not particularly limited in this embodiment of the present invention.
When the driver 3 controls the switch circuit 1 based on the modulation pulse, the first MOS transistor Q1Is a P-type MOS transistor, a second MOS transistor Q2Is an N-type MOS transistor, and the first MOS transistor Q1Source s of1Connected with an external power supply and a second MOS tube Q2Source s of2Grounded, therefore, the first MOS transistor Q is in the high level period of the modulation pulse1Conducting, second MOS tube Q2Turn off, during low level of the modulation pulse, the first MOS transistor Q1Turn-off, second MOS transistor Q2And is turned on, thereby realizing control of the switch circuit 1.
It should be noted that, when the voltage between the drain and the source of the P-type MOS transistor is less than 0 and the voltage between the gate and the source is less than the turn-on voltage, a conductive channel is formed between the source and the drain of the P-type MOS transistor, so that the P-type MOS transistor can be turned on1Source s of1Under the condition of connecting an external power supply, during the high level period of the modulation pulse, the first MOS tube Q1Drain electrode of (d)1And source s1Voltage between is less than O and gate g1And source s1The voltage between is less than the breakover voltage, the first MOS tube Q1Can be conducted, and the first MOS transistor Q is in the low level period of the modulation pulse1May be turned off. Similarly, when the voltage between the drain and the source of the N-type MOS transistor is greater than 0 and the voltage between the gate and the source of the N-type MOS transistor is greater than the turn-on voltage, a conductive channel is formed between the source and the drain of the N-type MOS transistor, so that the N-type MOS transistor can be turned on, and therefore, the source s of the second MOS transistor is connected to the source s of the second MOS transistor2In the case of grounding, the second MOS transistor Q is in the low level period of the modulation pulse2Drain electrode of (d)2And source s2Voltage between is greater than 0 and gate g2And source s2The voltage between is greater than the breakover voltage, the second MOS tube Q2Can be conducted, and the second MOS tube Q is in the high level period of the modulation pulse2May be turned off.
Wherein, when the first MOS transistor Q1Conducting, second MOS tube Q2When the power is turned off, the input voltage provided by the external power supply can pass through the first MOS transistor Q1Is input into the fourth order low pass filter 4 so that the load is supplied with power through the output of the fourth order low pass filter 4, while the fourth order low pass filter 4 is charged by the input voltage. When the first MOS transistor Q1Turn-off, second MOS transistor Q2When the MOS transistor is switched on, the input voltage can not pass through the first MOS transistor Q1The input signal is inputted into a fourth-order low-pass filter 4, and at this time, the fourth-order low-pass filter 4 can pass through the second MOS transistor Q2Discharging is performed to power the load.
In the switching circuit 1 shown in fig. 3, the driver 3 is used to drive the first MOS transistor Q1And a second MOS transistor Q2Thereby enabling control of the switching circuit 1.
The switching power supply is realized by switching off and on the switching circuit 1, that is, in the working process of the switching power supply, the switching circuit needs to be switched between off and on to convert the input voltage into the stable output voltage. Therefore, the switch circuit 1 only needs to be capable of turning off and on, so that the switch circuit 1 may have not only the structure shown in fig. 3 but also other structures, which is not particularly limited in the embodiment of the present invention.
Alternatively, referring to fig. 4, the switching circuit 1 may include: third MOS transistor Q3And a diode D;
third MOS transistor Q3Receiving the input voltage and the modulation pulse output by the driver 3, and a third MOS transistor Q3The input voltage is output to the diode D and the fourth-order low-pass filter 4.
Wherein, the third MOS transistor Q3Source s of3Receiving input voltage provided by external power supply, and a third MOS transistor Q3Grid g of3Receiving the modulation pulse output by the driver 3, and the drain d of the third MOS transistor3The input voltage is output to the cathode of the diode D and the fourth-order low-pass filter 4, and the anode of the diode D is grounded. That is, the third MOS transistor Q3Source s of3A third MOS transistor Q connected with an external power supply VDD3Grid g of3A third MOS transistor Q connected with the output end 32 of the driver 33Drain electrode of (d)3A third MOS transistor Q connected with the cathode of the diode D3Drain electrode of (d)3And the cathode of the diode D is also connected to the input 41 of the fourth order low pass filter 4, respectively, and the anode of the diode D is grounded.
It should be noted that the third MOS transistor Q3Can be a P-type MOS transistor, and a third MOS transistor Q3The diode may be used as a pull-up switch of the switching power supply, and the diode may be used as a pull-down switch of the switching power supply, which is not specifically limited in this embodiment of the present invention.
When the driver 3 controls the switch circuit 1 based on the modulation pulse, the third MOS transistor Q3Is a P-type MOS transistor, a third MOS transistor Q3Source s of3Connected with an external power supply and a third MOS transistor Q3Drain electrode of (d)3Connected to the cathode of the diode D and having a unidirectional conductivity, i.e. a current can flow only from the anode to the cathode of the diode D, therefore, at high power of the modulated pulseIn flat period, the third MOS transistor Q3The diode D is turned off, and the third MOS transistor Q is turned on during the low level of the modulation pulse3And the diode D is turned off and turned on, thereby realizing the control of the switching circuit 1.
In addition, when the third MOS transistor Q3When the diode D is switched on and switched off, the input voltage provided by the external power supply can pass through the third MOS tube Q3Is input into the fourth order low pass filter 4 so that the load is supplied with power through the output of the fourth order low pass filter 4, while the fourth order low pass filter 4 is charged by the input voltage. When the third MOS transistor Q3When the diode D is switched off and the diode D is switched on, the input voltage can not pass through the third MOS tube Q3Is input into the fourth order low pass filter 4, at which time the fourth order low pass filter 4 may be discharged through the diode D to power the load.
In the switching circuit 1 shown in fig. 4, the driver 3 is used to drive the third MOS transistor Q3And the diode D is turned off or on, thereby realizing the control of the switching circuit 1.
It should be further noted that, in the switching circuits shown in fig. 3 and fig. 4, the MOS transistor may also be replaced by a triode, so as to implement the functions of turning off and turning on, which is not specifically limited in the embodiment of the present invention.
Referring to fig. 5, the controller 2 includes: a signal generator 25, an adder 26, a comparator 27, and an error amplifier 28;
the signal generator 25 outputs the generated first pulse signal to the adder 26, the fourth-order low-pass filter 4 outputs the first output voltage to the adder 26, the adder 26 adds the first pulse signal and the first output voltage to obtain a second pulse signal, and outputs the second pulse signal to the comparator 26;
the fourth-order low-pass filter 4 outputs the second output voltage to the error amplifier 28, the error amplifier 28 also receives the reference voltage, and the error amplifier 28 performs error amplification on the second output voltage and the reference voltage to obtain an error amplification voltage;
the error amplifier 28 outputs the error amplification voltage to the comparator 27, the comparator 27 compares the second pulse signal with the error amplification voltage to generate a modulation pulse, and the comparator 27 outputs the modulation pulse to the driver 3.
The adder 26 may output the second pulse signal to the negative input terminal of the comparator, the fourth-order low-pass filter 4 may output the second output voltage to the negative input terminal of the error amplifier 28, the positive input terminal of the error amplifier 28 may receive the reference voltage provided by the reference power supply, and the error amplifier 28 may output the error amplified voltage to the positive input terminal of the comparator 27.
Wherein, the output end of the signal generator 25 and the first output end 42 of the fourth-order low-pass filter 4 are respectively connected with the input end of the adder 26, and the output end of the adder 26 is connected with the negative input end of the comparator 27; the negative input of the error amplifier 28 is connected to the second output 43 of the fourth order low pass filter 4, and the positive input of the error amplifier 28 is connected to the reference supply VREFThe output of error amplifier 28 is connected to the positive input of comparator 27 and the output of comparator 27 is connected to input 31 of driver 3.
It should be noted that the signal generator 25 is configured to generate a first pulse signal, where the first pulse signal may be a periodic sawtooth wave signal or a periodic rectangular signal, and may also be other periodic triangular signals, which is not limited in this embodiment of the present invention.
When the modulation pulse is generated by the controller 2, the signal generator 25 may generate a first pulse signal and input the first pulse signal to the adder 26, and since the first output terminal 42 of the fourth-order low-pass filter 4 is also connected to the input terminal of the adder 26, the adder 26 may add the input first pulse signal and the first output voltage to obtain a second pulse signal and input the second pulse signal to the comparator 27. Meanwhile, since the negative input terminal of the error amplifier 28 in the controller 2 is connected to the second output terminal 43 of the fourth-order low-pass filter 4, and the positive input terminal of the error amplifier 28 is connected to the reference power supply, when the reference power supply is turned on, a second output voltage is obtained by detecting the second output terminal 43 of the fourth-order low-pass filter 4, and the error amplifier 28 may determine an error amplification voltage based on the second output voltage and the reference voltage, and input the error amplification voltage to the comparator 27. At this time, the comparator 27 may compare the second pulse signal with the error amplification voltage, thereby generating a modulation pulse.
When the error amplifier 28 determines the error amplification voltage based on the second output voltage and the reference voltage, the error amplifier 28 may subtract the second output voltage from the reference voltage to obtain an error voltage, and amplify the error voltage to obtain the error amplification voltage.
When the comparator 27 compares the second pulse signal with the error amplification voltage to generate the modulation pulse, the comparator 27 may compare the currently input second pulse signal with the error amplification voltage, generate a low level signal if the second pulse signal is greater than the error amplification voltage, and generate a high level signal if the second pulse signal is less than the error amplification voltage, thereby forming the modulation pulse.
It should be noted that the comparator 27 may include multiple models, the error amplifier 28 may also include multiple models, and the amplification factor of the error amplifier 28 is different for error amplifiers 28 of different models, so in practical application, the comparator 27 and the error amplifier 28 of different models may be selected according to different needs, which is not specifically limited in the embodiment of the present invention.
Referring to fig. 6, the fourth-order low-pass filter 4 includes: first inductance L1A second inductor L2A first capacitor C1And a second capacitor C2；
First inductance L1The same name end of the first inductor receives the input voltage output by the switch circuit 1, and the first inductor L1The different name terminal outputs the first output voltage to the first capacitor C1One terminal of (1), a first capacitor C1The other end of the first output voltage is a first inductor L1Dividing the input voltage to obtain a divided voltage;
first inductance L1The different name end also outputs the first output voltage to the second inductor L2End of synonyms, second telegramFeeling L2The same name terminal outputs the second output voltage to the second capacitor C2One terminal of (C), a second capacitor C2The other end of the first inductor is grounded, and the second output voltage is a second inductor L2Dividing the first output voltage to obtain a first output voltage;
first inductance L1The second inductor L outputs the first output voltage to the controller 22Also outputs a second output voltage into the controller 2.
Wherein, the first inductance L1Is connected to the output 12 of the switching circuit 1, a first inductance L1The different name terminal and the first capacitor C1Is connected to a first capacitor C1The other end of the first and second electrodes is grounded;
first inductance L1The different name end of the inductor is also connected with a second inductor L2Is connected with a second inductor L2End of same name and second capacitor C2Is connected to a second capacitor C2The other end of the first and second electrodes is grounded;
first inductance L2Is further connected to a first input terminal 21 of the controller 2, a second inductance L2Is also connected to a second input 22 of the controller 2.
It should be noted that, the first inductance L is used1Is connected to the output 12 of the switching circuit 1, a first inductance L1End of different name and second inductance L2Is connected with a second inductor L2End of same name and second capacitor C2Is connected, therefore, to the first inductance L1And a second inductance L2A negative coupling inductance can be formed.
The first inductor L filters the input voltage through a fourth order low pass filter 41And a first capacitor C1Attenuating the high-frequency signal of the input voltage, and passing through a second inductor L2And a second capacitor C2Further attenuating. Due to the first inductance L1And a second inductance L2A negative coupling inductor can be formed, so that the first inductor L is subjected to a negative coupling process1Is small, so that the fourth order low pass filter 4 can be reducedThe total equivalent inductance. And because the reduction of the total equivalent inductance value of the fourth-order low-pass filter correspondingly improves the cut-off frequency of the fourth-order low-pass filter, the fourth-order low-pass filter subjected to negative coupling processing can further attenuate high-frequency signals in the input voltage, inhibit alternating current components in the input voltage and further reduce ripples in the output voltage.
In addition, since the first output voltage is the input voltage passing through the first inductor L1Then, the second output voltage is obtained by passing the input voltage through the first inductor L1A first capacitor C1And a second inductance L2Then, the first inductor and the first capacitor in the fourth-order low-pass filter can be equivalent to a high-pass link, that is, the first inductor L1And a first capacitor C1It is equivalent to a high-pass link, so that the response speed of the first output voltage is greater than that of the second output voltage. The controller respectively processes the first output voltage and the second output voltage through two lines, namely the first output voltage is processed while the second output voltage is processed, a signal fed back to the controller by the first output voltage is a high-frequency component feedback signal, and a signal fed back to the controller by the second output voltage is a direct-current part signal, so that the processing speed of the high-frequency component feedback signal is ensured while the direct-current part signal feedback processing is ensured, the speed of generating modulation pulses by the controller is increased, and the response speed of the switching power supply is also increased.
It should be further noted that, since the switching power supply has a certain switching frequency, the switching frequency is the frequency for controlling the switching circuit to be turned off and on in the embodiment of the present invention, and the switching frequency depends on the modulation pulse. When the switching frequency of the switching power supply provided by the embodiment of the invention is higher, for example, the switching frequency is greater than 400MHz, at this time, the first inductor L1And a second inductance L2Can be set to 1.2nH, the first capacitor C1And a second C2Can be set to 2nF, so that the attenuation of high frequency signals in the input voltage can be improved. In addition, experiments prove that when the power supply is switched on and offWhen the switching frequency is 450MHz, the attenuation value of the input voltage attenuated by the second-order low-pass filter is-45 dB, the attenuation value of the input voltage attenuated by the non-coupled fourth-order low-pass filter is-50 dB, the attenuation value of the input voltage attenuated by the positively-coupled fourth-order low-pass filter is-40 dB, and the attenuation value of the input voltage attenuated by the negatively-coupled fourth-order low-pass filter is-62 dB, namely, the attenuation value of the input voltage attenuated by the negatively-coupled fourth-order low-pass filter is the largest, so that the output voltage ripple of the switching power supply can be reduced.
Furthermore, the inductor in the fourth-order low-pass filter has certain power loss, and the inductor loss can be determined by the following formula;
Figure GPA0000248193010000181
wherein P is the inductive loss, IDC1Is the direct part current of the output current of the switching power supply, IAC1Root mean square current, R, of output current ripple of switching power supplyL1，DCIs a first inductance L1Equivalent resistance value of RL2，DCIs a second inductance L2Equivalent resistance value of RL1，ACIs a first inductance L1The ac impedance of (1).
In addition, experiments prove that when the first inductance L is changed1And a second inductance L2The total inductance loss of the negative coupling inductor in the fourth-order low-pass filter can be smaller than that of the second-order low-pass filter or the fourth-order low-pass filter of the positive coupling inductor under certain output current, for example, when the output current is 120 mA-140 mA, the total inductance loss of the negative coupling inductor in the fourth-order low-pass filter is smaller than that of the second-order low-pass filter or the fourth-order low-pass filter of the positive coupling inductor. Therefore, in order to reduce the power loss of the inductor itself in the fourth order low pass filter, the first inductor L may be provided1And a second inductance L2The inductance value of (c) is different.
In the embodiment of the present invention, since the first input terminal of the switch circuit is connected to the external power supply, and the output terminal of the switch circuit is connected to the fourth-order low-pass filter, the input voltage provided by the external power supply can be input to the fourth-order low-pass filter through the switch circuit, and the high-frequency signal in the input voltage is attenuated by the fourth-order low-pass filter. Since the fourth-order low-pass filter has the negative coupling characteristic, the high-frequency signal in the input voltage can be further attenuated by the negative coupling characteristic of the fourth-order low-pass filter, so that the attenuation value of the high-frequency signal in the input voltage is improved, the alternating current component in the input voltage is restrained, and the ripple of the output voltage of the switching power supply is further reduced.
Fig. 7 is a flowchart of a method for controlling a switching power supply according to an embodiment of the present invention. Referring to fig. 7, the method is applied to the switching power supply shown in the above embodiment, and includes:
step 701: the first output voltage and the second output voltage are detected by the controller when the input voltage and the reference voltage are turned on.
Step 702: a modulation pulse is generated by a controller based on the first output voltage, the second output voltage, and a reference voltage.
Step 703: the modulated pulses are output to the driver by the controller.
Step 704: when a modulation pulse is received by the driver, the switching circuit is controlled based on the modulation pulse.
In the embodiment of the invention, when the input voltage and the reference voltage are switched on, the first output voltage and the second output voltage can be detected by the controller, so that the controller generates the modulation pulse based on the first output voltage, the second output voltage and the reference voltage provided by the reference power supply, and the driver controls the switching circuit based on the modulation pulse, thereby realizing the function of converting the electric energy of the switching power supply. The high-frequency signal in the input voltage can be further attenuated by the negative coupling characteristic of the fourth-order low-pass filter, so that the attenuation value of the high-frequency signal in the input voltage is improved, the alternating-current component in the input voltage is restrained, and the ripple of the output voltage of the switching power supply is further reduced.
Optionally, the switching circuit includes a first MOS transistor and a second MOS transistor;
controlling the switching circuit based on the modulated pulses, comprising:
during the high level period of the modulation pulse, controlling the first MOS tube to be conducted and controlling the second MOS tube to be switched off;
and during the low level of the modulation pulse, the first MOS tube is controlled to be switched off, and the second MOS tube is controlled to be switched on.
Optionally, the switching circuit includes a third MOS transistor and a diode;
controlling the switching circuit based on the modulated pulses, comprising:
during the high level period of the modulation pulse, controlling the third MOS tube to be conducted and controlling the diode to be switched off;
and during the low level of the modulation pulse, the third MOS tube is controlled to be switched off, and the diode is controlled to be switched on.
Optionally, the controller comprises a signal generator, an adder, a comparator and an error amplifier;
generating, by a controller, a modulated pulse based on a first output voltage, a second output voltage, and a reference voltage, comprising:
determining, by the error amplifier, an error amplified voltage based on the second output voltage and the reference voltage;
generating a first pulse signal through a signal generator, and adding the first pulse signal and a first output voltage through an adder to obtain a second pulse signal;
a modulated pulse is generated by a comparator based on the error amplified voltage and the second pulse signal.
All the above optional technical solutions can be combined arbitrarily to form an optional embodiment of the present invention, which is not described in detail herein.
Fig. 8 is a flowchart of a method for controlling a switching power supply according to an embodiment of the present invention. Referring to fig. 8, the method is applied to the switching power supply shown in the above embodiment, and includes:
step 801: when the input voltage and the reference voltage are switched on, a first output voltage and a second output voltage are detected by the controller, wherein the first output voltage is output by a first output end of the fourth-order low-pass filter, and the second output voltage is output by a second output end of the fourth-order low-pass filter.
The external power supply and the reference power supply can be switched on when the input voltage and the reference voltage are switched on, the external power supply and the reference power supply can be switched on manually by a user when the external power supply and the reference power supply are switched on, and the external power supply and the reference power supply can also be switched on intelligently by a certain control strategy.
The second output end of the fourth-order low-pass filter can be connected with the load, so that the load can be supplied with power through the voltage output by the second output end of the fourth-order low-pass filter.
It should be noted that the external power source may be a separate power supply device, such as a storage battery, and the reference voltage provided by the reference power source may be equal to the voltage required by the load, which is not specifically limited in this embodiment of the present invention.
In addition, the load may include an electronic device, a communication device, and the like, and of course, the load may also be a storage battery, which is not specifically limited in this embodiment of the present invention.
Step 802: a modulation pulse is generated by a controller based on the first output voltage, the second output voltage, and a reference voltage.
Since the controller may include a signal generator, an adder, a comparator, and an error amplifier, when the modulation pulse is generated by the controller based on the first output voltage, the second output voltage, and a reference voltage provided by a reference power source, it is possible to determine an error amplification voltage by the error amplifier based on the second output voltage and the reference voltage, generate a first pulse signal by the signal generator, and add the first pulse signal to the first output voltage by the adder to obtain a second pulse signal, and generate the modulation pulse by the comparator based on the error amplification voltage and the second pulse signal.
When the error amplifier determines the error amplification voltage based on the second output voltage and the reference voltage, the error amplifier may subtract the second output voltage from the reference voltage to obtain an error voltage, and amplify the error voltage to obtain the error amplification voltage.
When the comparator compares the second pulse signal with the error amplification voltage to generate the modulation pulse, the comparator may compare the currently input second pulse signal with the error amplification voltage, generate a low level signal if the second pulse signal is greater than the error amplification voltage, and generate a high level signal if the second pulse signal is less than the error amplification voltage, thereby constituting the modulation pulse.
It should be noted that, reference may be made to related technologies for a method of adding the first pulse signal and the first output voltage by the adder to obtain the second pulse signal, and this is not described in detail in this embodiment of the present invention.
Step 803: the modulated pulses are output to a driver by a controller.
Since the output of the controller is connected to the input of the driver, after the modulated pulse is generated by the controller, the modulated pulse can also be output to the driver by the controller.
Step 804: when the modulation pulse is received by the driver, the switching circuit is controlled based on the modulation pulse.
In the embodiment of the present invention, two implementation manners of the switching circuit are exemplified, and further, two manners of controlling the switching circuit based on the modulation pulse may also be included, as follows:
(1) when the switching circuit comprises a first MOS tube and a second MOS tube, the first MOS tube is controlled to be switched on and the second MOS tube is controlled to be switched off during the high level period of the modulation pulse; and during the low level period of the modulation pulse, the first MOS tube is controlled to be switched off, and the second MOS tube is controlled to be switched on.
It should be noted that the first MOS transistor may be a P-type MOS transistor, the second MOS transistor may be an N-type MOS transistor, the first MOS transistor may be used as a pull-up switch of the switching power supply, and the second MOS transistor may be used as a pull-down switch of the switching power supply, which is not specifically limited in this embodiment of the present invention.
When the driver is based on modulation pulse to control this switch circuit, because first MOS pipe is P type MOS pipe, the second MOS pipe is N type MOS pipe, and external power supply is connected to the source electrode of first MOS pipe, the source electrode ground connection of second MOS pipe, consequently, during the high level of modulation pulse, first MOS pipe switches on, and the second MOS pipe is shut off, and during the low level of modulation pulse, first MOS pipe is shut off, and the second MOS pipe switches on to the realization is to switch circuit's control.
In addition, when the first MOS tube is switched on and the second MOS tube is switched off, the input voltage provided by the external power supply can be input into the fourth-order low-pass filter through the first MOS tube, so that the load is supplied with power through the output of the fourth-order low-pass filter, and meanwhile, the fourth-order low-pass filter is charged through the input voltage. When the first MOS tube is turned off and the second MOS tube is turned on, the input voltage cannot be input into the fourth-order low-pass filter through the first MOS tube, and at the moment, the fourth-order low-pass filter can discharge through the second MOS tube to supply power to the load.
(2) When the switch circuit comprises a third MOS tube and a diode, the third MOS tube is controlled to be conducted and the diode is controlled to be switched off during the high level period of the modulation pulse; and during the low level period of the modulation pulse, the third MOS tube is controlled to be switched off, and the diode is controlled to be switched on.
It should be noted that the third MOS transistor may be a P-type MOS transistor, the third MOS transistor may be used as a pull-up switch of the switching power supply, and the diode may be used as a pull-down switch of the switching power supply, which is not specifically limited in this embodiment of the present invention.
When the driver controls the switch circuit based on the modulation pulse, the third MOS tube is a P-type MOS tube, the source electrode of the third MOS tube is connected with the external power supply, and the drain electrode of the third MOS tube is connected with the cathode of the diode, so that the third MOS tube is switched on and the diode is switched off during the high level period of the modulation pulse, and the third MOS tube is switched off and the diode is switched on during the low level period of the modulation pulse, thereby realizing the control of the switch circuit.
In addition, when the third MOS transistor is turned on and the diode is turned off, an input voltage provided by the external power supply may be input to the fourth-order low-pass filter through the third MOS transistor, so that the load is powered by an output of the fourth-order low-pass filter, and the fourth-order low-pass filter is charged by the input voltage. When the third MOS transistor is turned off and the diode is turned on, the input voltage cannot be input into the fourth-order low-pass filter through the third MOS transistor, and at this time, the fourth-order low-pass filter can discharge through the diode to supply power to the load.
In the embodiment of the invention, because the external power supply is used for providing input voltage for the switching power supply, and the reference power supply is used for providing the reference power supply for the switching power supply, when the external power supply and the reference power supply are switched on, the first output voltage and the second output voltage can be detected by the controller, so that the controller generates the modulation pulse based on the first output voltage, the second output voltage and the reference voltage provided by the reference power supply, and the driver controls the switching circuit based on the modulation pulse, thereby realizing the function of converting the electric energy of the switching power supply. And because the input voltage provided by the external power supply is input to the fourth-order low-pass filter through the switch circuit, the high-frequency signal in the input voltage can be attenuated by the fourth-order low-pass filter, and because the fourth-order low-pass filter has the negative coupling characteristic, the high-frequency signal in the input voltage can be further attenuated by the negative coupling characteristic of the fourth-order low-pass filter, so that the attenuation value of the high-frequency signal in the input voltage is improved, the alternating-current component in the input voltage is restrained, and the ripple of the output voltage of the switch power supply is further reduced.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (7)

1. A switching power supply, characterized in that the switching power supply comprises: the four-order low-pass filter comprises a first inductor, a second inductor, a first capacitor and a second capacitor, wherein the different name end of the first inductor is respectively connected with the different name end of the second inductor and one end of the first capacitor, and the same name end of the second inductor is connected with one end of the second capacitor so as to enable the first inductor and the second inductor to form an inductor with a negative coupling characteristic;
the switch circuit receives an input voltage and outputs the input voltage to the fourth-order low-pass filter;
the fourth-order low-pass filter outputs a first output voltage and a second output voltage to the controller, wherein the first output voltage is output by a first output end of the fourth-order low-pass filter based on the input voltage, and the second output voltage is output by a second output end of the fourth-order low-pass filter based on the input voltage;
the controller receives a reference voltage, generates a modulation pulse based on the first output voltage, the second output voltage and the reference voltage, and outputs the modulation pulse to the driver;
the driver outputs the modulation pulse to the switching circuit to control the switching circuit by the modulation pulse.
2. The switching power supply according to claim 1, wherein the switching circuit comprises: the MOS transistor comprises a first Metal Oxide Semiconductor (MOS) transistor and a second MOS transistor;
the first MOS tube receives the input voltage and outputs the input voltage to the second MOS tube and the fourth-order low-pass filter;
the first MOS tube and the second MOS tube respectively receive the modulation pulse output by the driver.
3. The switching power supply according to claim 1 or 2, wherein the controller includes: a signal generator, an adder, a comparator and an error amplifier;
the signal generator outputs a generated first pulse signal to the adder, the fourth-order low-pass filter outputs the first output voltage to the adder, the adder adds the first pulse signal and the first output voltage to obtain a second pulse signal, and the second pulse signal is output to the comparator;
the fourth-order low-pass filter outputs the second output voltage to the error amplifier, the error amplifier also receives the reference voltage, and the error amplifier performs error amplification on the second output voltage and the reference voltage to obtain error amplification voltage;
the error amplifier outputs the error amplified voltage to the comparator, the comparator compares the second pulse signal with the error amplified voltage to generate the modulated pulse, and the comparator outputs the modulated pulse to the driver.
4. The switching power supply of claim 1, wherein the fourth order low pass filter comprises: the circuit comprises a first inductor, a second inductor, a first capacitor and a second capacitor;
the dotted terminal of the first inductor receives the input voltage output by the switch circuit, the synonym terminal of the first inductor outputs the first output voltage to one terminal of the first capacitor, the other terminal of the first capacitor is grounded, and the first output voltage is obtained by dividing the input voltage by the first inductor;
the synonym end of the first inductor also outputs the first output voltage to the synonym end of the second inductor, the synonym end of the second inductor outputs the second output voltage to one end of the second capacitor, the other end of the second capacitor is grounded, and the second output voltage is obtained by dividing the first output voltage by the second inductor;
the different-name end of the first inductor also outputs the first output voltage to the controller, and the same-name end of the second inductor also outputs the second output voltage to the controller.
5. A method of controlling the switching power supply of any one of claims 1-4, the method comprising:
detecting, by the controller, the first output voltage and the second output voltage when the input voltage and the reference voltage are turned on;
generating, by the controller, the modulation pulse based on the first output voltage, the second output voltage, and the reference voltage;
outputting, by the controller, the modulated pulses to the driver;
controlling the switching circuit based on the modulation pulse when the modulation pulse is received by the driver.
6. The method of claim 5, wherein the switching circuit comprises a first MOS transistor and a second MOS transistor;
the controlling the switching circuit based on the modulation pulse includes:
during the high level period of the modulation pulse, controlling the first MOS tube to be conducted and controlling the second MOS tube to be switched off;
and during the low level period of the modulation pulse, the first MOS tube is controlled to be switched off, and the second MOS tube is controlled to be switched on.
7. The method of claim 5 or 6, wherein the controller comprises a signal generator, an adder, a comparator, and an error amplifier;
the generating, by the controller, the modulated pulse based on the first output voltage, the second output voltage, and the reference voltage includes:
determining, by the error amplifier, an error amplified voltage based on the second output voltage and the reference voltage;
generating a first pulse signal through the signal generator, and adding the first pulse signal and the first output voltage through the adder to obtain a second pulse signal;
generating the modulation pulse by the comparator based on the error amplification voltage and the second pulse signal.
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