CN115276418A - High-frequency switching power supply circuit, switching power supply and switching unit - Google Patents

High-frequency switching power supply circuit, switching power supply and switching unit Download PDF

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Publication number
CN115276418A
CN115276418A CN202210988061.8A CN202210988061A CN115276418A CN 115276418 A CN115276418 A CN 115276418A CN 202210988061 A CN202210988061 A CN 202210988061A CN 115276418 A CN115276418 A CN 115276418A
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China
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signal
power supply
preset
voltage
load
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CN202210988061.8A
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Chinese (zh)
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CN115276418B (en
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曹建林
何刚
彭琪
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Shenzhen Chengxin Micro Technology Co ltd
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Shenzhen Chengxin Micro Technology 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/2176—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only comprising a passive stage to generate a rectified sinusoidal voltage and a controlled switching element in series between such stage and the output
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The present application relates to a high-frequency switching power supply circuit, a switching power supply, and a switching unit. The circuit comprises: the transformer comprises a primary coil and a secondary coil; one end of the primary coil is connected with the input power supply module, and the other end of the primary coil is connected with the switch control module and used for conducting according to a preset frequency under the control of the switch control module to generate a first alternating current signal; the secondary coil is connected with two ends of the voltage-stabilizing filtering module respectively and used for receiving the second alternating current signal and sending the second alternating current signal to the voltage-stabilizing filtering module; the voltage stabilizing and filtering module is also connected with the load and used for stabilizing and filtering the second alternating current signal to generate a direct current power supply signal and outputting the direct current power supply signal to the load; the feedback module is connected with the load and the switch control module and used for collecting direct current supply signals and generating feedback voltage signals so that the switch control module determines the preset frequency according to the feedback voltage signals.

Description

High-frequency switching power supply circuit, switching power supply and switching unit
Technical Field
The present application relates to the field of power supplies, and in particular, to a high-frequency switching power supply circuit, a switching power supply, and a switching unit.
Background
With the development of science and technology, electronic devices gradually enter people's lives, and devices such as mobile phones, computers, displays, household appliances and printers have become common equipment in people's daily lives. For such devices, the internal components are mostly dc power, and the municipal power supply is ac power, so that for such devices, it is necessary to convert ac power into dc power to power such devices.
The linear power supply is a power supply which utilizes a transformer to transform alternating current through the transformer and then performs rectification and filtering through a rectifying circuit to obtain direct current voltage.
However, the linear power source has large power consumption, and the transformer used is large and heavy, and is difficult to adapt to power supply of computer equipment such as computers.
Disclosure of Invention
In order to reduce the power consumption of a direct current power supply, the application provides a high-frequency switching power supply circuit, a switching power supply and a switching unit.
In a first aspect, the present application provides a high-frequency switching power supply circuit, which adopts the following technical scheme:
a high frequency switching power supply circuit, power supply circuit is connected with input power module and load, input power module is used for converting municipal power into direct current signal output extremely power supply circuit, power supply circuit includes: the transformer comprises a primary coil and a secondary coil;
one end of the primary coil is connected with the input power supply module, the other end of the primary coil is connected with the switch control module, and the primary coil is used for receiving the direct current electric signal, conducting or disconnecting the direct current electric signal according to preset frequency under the control of the switch control module and generating a first alternating current electric signal;
the secondary coil is coupled with the primary coil, and is also respectively connected with two ends of the voltage stabilizing and filtering module, and is used for receiving a second alternating current signal and sending the second alternating current signal to the voltage stabilizing and filtering module, wherein the second alternating current signal is a signal obtained by voltage-reducing and coupling the first alternating current signal to the secondary coil through a transformer;
the voltage stabilizing and filtering module is also connected with the load and used for stabilizing and filtering the second alternating current signal to generate a direct current power supply signal, outputting the direct current power supply signal to the load and supplying power to the load;
the feedback module is connected with the load and the switch control module and used for collecting the direct current power supply signal and generating a feedback voltage signal to the switch control module so that the switch control module determines the preset frequency according to the feedback voltage signal.
By adopting the technical scheme, the switch control module is used for controlling the primary coil to be switched on or switched off according to the preset frequency, the rectified direct current is firstly converted into the first alternating current signal under the action of the high-frequency switch, then the transformer is used for reducing the first alternating current signal into the second alternating current signal, and finally the filtering and voltage-stabilizing module is used for converting the second alternating current signal into the direct current power supply signal to supply power for the load.
Further, the transformer is conducted according to a preset frequency under the control of the switch control module, namely the transformer is controlled to be conducted for a preset time length in a period, when the transformer is conducted, a primary coil of the transformer continuously accumulates energy, when the transformer is turned off, the accumulated energy is transmitted to a secondary coil, then a voltage stabilizing and filtering module connected with the secondary coil converts an alternating current signal into a direct current power supply signal to supply power to a load, when the preset frequency is higher, the preset time length representing the conduction of the transformer is shortened, then the current for supplying power to the load is reduced, the size of the preset frequency is adjusted according to the load so as to adapt to the power consumption requirements of different loads, and the power consumption in light load or no load is favorably reduced; the preset frequency is determined by the switch control module according to the feedback voltage signal fed back, the condition of the current load is determined according to different feedback voltage signals, and the corresponding preset frequency is selected according to the condition of the current load.
In a possible implementation manner, the transformer further includes an auxiliary coil, and the auxiliary coil is coupled with the secondary coil and further connected to the switch control module, so as to supply power to the switch control module, so that the switch control module operates.
By adopting the technical scheme, the auxiliary coil of the transformer is used for supplying power to the switch control module so as to enable the switch control module to work.
In another possible implementation manner, the high-frequency switching power supply circuit further includes a high-voltage starting module, and the high-voltage starting module is connected to the input power supply module and is configured to receive the direct-current electrical signal; the high-voltage starting module is also connected with the switch control module and used for driving the switch control module to start working after a preset time length when the direct-current signal is received.
By adopting the technical scheme, the switch control module has larger power consumption in a preset time period after the high-frequency switch power supply circuit is started, and in order to reduce the power consumption of the switch control module, the high-voltage start module supplies power to the switch control module after the high-voltage start module delays for a preset time.
In another possible implementation manner, the switch control module includes a switch unit, a resistor CSR1 and a resistor CSR2, where the switch unit includes a DRAIN terminal DRAIN, a source terminal CS, a feedback terminal FB, and a power terminal VDD, the power terminal VDD is used for connecting to a power supply and supplying power to the switch unit, and the feedback module is connected to the feedback terminal FB and is used for feeding a feedback voltage signal back to the switch unit through the feedback terminal FB, so that the switch unit determines a preset frequency corresponding to a current load according to the feedback voltage signal, and controls the DRAIN terminal CS and the source terminal DRAIN to be turned on according to the preset frequency; one end of the resistor CSR1 is connected with the source terminal CS, the other end is grounded, the resistor CSR2 is connected with the resistor CSR1 in parallel, and the DRAIN terminal DRAIN is connected with the same-name terminal of the primary coil.
By adopting the technical scheme, the switching unit determines the preset frequency of the current load according to the feedback voltage signal received by the feedback terminal FB, when the switching unit controls the DRAIN terminal DRAIN and the source terminal CS to be conducted, the primary coil of the transformer is in a conducting state at the moment, when the switching unit controls the DRAIN terminal DRAIN and the source terminal CS to be disconnected, the primary coil of the transformer is in a disconnecting state at the moment, and the DRAIN terminal DRAIN and the source terminal CS are controlled to be conducted or disconnected through the switching unit so as to control the conduction and the disconnection of the primary coil.
In another possible implementation manner, the switching unit includes a MOS transistor MOSFET-N, a soft start circuit, an oscillator OSC, and a PWM modulator, where a DRAIN of the MOS transistor MOSFET-N is used as the DRAIN terminal DRAIN, a source is used as the source terminal CS, and a base is connected to the soft start circuit; the oscillator OSC is used for generating sawtooth wave signals, the PWM modulator comprises a positive input end, a negative input end and an output end, wherein the positive input end is connected with the oscillator OSC and used for receiving the sawtooth wave signals, the negative input end is connected with the feedback end FB and used for receiving feedback voltage signals, and the output end is connected with the soft start circuit and used for generating PWM square wave signals with preset duty ratios according to ramp signals and feedback voltage value signals and outputting the PWM square wave signals to the soft start circuit; the soft start circuit is used for controlling the MOS tube MOSFET-N to be conducted according to the preset frequency corresponding to the preset duty ratio according to the PWM square wave signal of the preset duty ratio.
By adopting the technical scheme, the PWM modulator generates the PWM square wave signal with the preset duty ratio, wherein the sawtooth wave signal is a preset signal, when the load changes, the corresponding feedback voltage signal changes according to the change of the load, so that the preset duty ratio of the PWM square wave signal modulated by the PWM modulator changes along with the change of the load, and the soft start circuit controls the source electrode and the drain electrode of the MOS tube MOSFET-N to be switched on or switched off according to the preset duty ratio, so that the supply current supplied to the load is adjusted according to different loads, and the power consumption can be reduced.
In another possible implementation manner, the soft start circuit comprises a Driver, a logic output and an SR flip-flop, wherein the logic output comprises a first input end, a second input end and an output end;
the output end of the logic output device is connected with the output end of the SR trigger, and the Q end of the SR trigger is connected with the first input end of the logic output device and used for sending the PWM square wave signal with the preset duty ratio to the logic output device;
the second input end of the logic output device is used for receiving a feedback voltage signal input by the feedback end FB, the output end of the logic output device is connected with a Driver, and the Driver is further connected with a base electrode of the MOS tube MOSFET-N, wherein the logic output device is used for driving the Driver to control the switch of the MOS tube MOSFET-N at a first preset frequency when the feedback voltage signal is greater than a first preset voltage threshold value; when the feedback voltage signal is not greater than a first preset voltage threshold and greater than a second preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to the frequency corresponding to the PWM square wave signal with the preset duty ratio; when the feedback voltage signal is not greater than a second preset voltage threshold and greater than a third preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to a second preset frequency; when the feedback voltage signal is not greater than a third preset voltage threshold, the Driver is driven to control the MOS tube MOSFET-N to be in a turn-off state, the feedback voltage signal represents the condition of a load, when the feedback voltage signal is greater than the first preset voltage threshold, the load is represented as a heavy load at the moment, the Driver is driven to control the MOS tube MOSFET-N to be switched on and off at a first preset frequency, namely when the load is the heavy load, the primary coil of the transformer is controlled to be switched on or off at the constant first preset frequency; when the load is a medium load, controlling the primary coil of the transformer to be switched on or switched off by a Driver according to the preset duty ratio of the PWM square wave signal modulated by the PWM modulator; when the load is light, the MOSFET-N of the MOS transistor is switched on and off at a second preset frequency; when the load is in no load, the load can be continuously kept in a disconnected state, different power supply modes are determined according to different loads, and further power consumption can be reduced, so that different load requirements can be met.
In a possible implementation manner, the switch unit further includes a compensator, where the compensator includes a first input port, a second input port, and an output port, where the first input port of the compensator is configured to be connected to the source terminal CS and receive a signal collected by the source terminal CS, the second input port of the compensator is connected to the oscillator OSC, and the output port is connected to the PWM modulator and configured to compensate a sawtooth wave signal generated by the oscillator OSC according to the collected signal, and send the compensated signal to the PWM modulator, so that the PWM modulator determines a PWM square wave signal with a preset duty ratio corresponding to a current load according to the compensated signal and a feedback voltage signal.
By adopting the technical scheme, the compensator performs superposition compensation on the signal collected by the source terminal CS and the sawtooth wave signal generated by the oscillator OSC, and the compensated signal is sent to the PWM modulator, so that the PWM modulator performs PWM square wave modulation, the harmonic generation probability in the high-frequency switching power supply circuit is effectively reduced, and the system is favorably stabilized.
In another possible implementation manner, the switch unit further includes an overvoltage protection unit and a logic or gate, where a positive input terminal of the overvoltage protection unit is used as an overvoltage protection terminal OVP and is configured to receive a collected voltage value, a negative input terminal of the overvoltage protection unit is configured to receive a reference voltage, the overvoltage protection unit is configured to output a stop signal when the collected voltage value is higher than the reference voltage, the output terminal of the overvoltage protection unit outputs the stop signal, one input terminal of the logic or gate is configured to be connected to the output terminal of the overvoltage protection unit, another input terminal of the logic or gate is configured to be connected to the PWM modulator, and the output terminal of the logic or gate is connected to the soft start circuit and is configured to control the soft start circuit to stop working when the overvoltage protection unit outputs the stop signal.
By adopting the technical scheme, when the voltage value of the OVP at the overvoltage protection end is higher than the reference voltage, the soft start circuit is controlled to stop working by utilizing the overvoltage protection unit, namely the soft start circuit controls the primary coil to be in an off state, so that the safety of the high-frequency switching power supply circuit and the load is effectively improved.
In another possible implementation manner, the high voltage starting module includes a resistor R2, a resistor R3, and a third polar capacitor EC3, wherein one end of the resistor R2 is connected to the input power module for receiving a direct current electrical signal, the other end of the resistor R2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to a positive polarity end of the third polar capacitor EC3, a negative polarity end of the third polar capacitor EC3 is grounded, and the switch control module is connected to the positive polarity end of the third polar capacitor EC 3.
By adopting the technical scheme, when the high-frequency switching power supply is started, the resistor R2 and the resistor R3 in the high-voltage starting module are utilized to charge the third polar capacitor EC3, and when the voltage of the positive polarity end of the third polar capacitor EC3 reaches the starting voltage of the switching control module, the switching control module starts to work. In a second aspect, the present application provides a switching power supply, which adopts the following technical solution:
a switching power supply, comprising: the high-frequency switching power supply circuit is provided.
In a third aspect, the present application provides a switch unit, which adopts the following technical solutions:
a switch unit, comprising: the device comprises an MOS tube MOSFET-N, a soft start circuit, an oscillator OSC and a PWM modulator, wherein the DRAIN electrode of the MOS tube MOSFET-N is used as the DRAIN electrode terminal DRAIN, the source electrode is used as the source electrode terminal CS, and the base electrode is connected with the soft start circuit; the oscillator OSC is used for generating sawtooth wave signals, the PWM modulator comprises a positive input end, a negative input end and an output end, wherein the positive input end is connected with the oscillator OSC and used for receiving the sawtooth wave signals, the negative input end is connected with the feedback end FB and used for receiving feedback voltage signals, and the output end is connected with the soft start circuit and used for generating PWM square wave signals with preset duty ratios according to ramp signals and feedback voltage value signals and outputting the PWM square wave signals to the soft start circuit; the soft start circuit is used for controlling the MOS tube MOSFET-N to be conducted according to a preset frequency corresponding to a preset duty ratio according to a PWM square wave signal of the preset duty ratio.
By adopting the technical scheme, the PWM modulator generates the PWM square wave signal with the preset duty ratio, wherein the sawtooth wave signal is a preset signal, when the load changes, the corresponding feedback voltage signal changes according to the change of the load, so that the preset duty ratio of the PWM square wave signal modulated by the PWM modulator changes along with the change of the load, and the soft start circuit controls the source electrode and the drain electrode of the MOS tube MOSFET-N to be switched on or switched off according to the preset duty ratio, so that the supply current supplied to the load is adjusted according to different loads, and the power consumption can be reduced.
In one possible implementation, the soft start circuit includes a Driver, a logic output and an SR flip-flop, where the logic output includes a first input terminal, a second input terminal and an output terminal;
the output end of the logic output device is connected with the output end of the SR trigger, and the Q end of the SR trigger is connected with the first input end of the logic output device and used for sending the PWM square wave signal with the preset duty ratio to the logic output device;
the second input end of the logic output device is used for receiving a feedback voltage signal input by the feedback end FB, the output end of the logic output device is connected with a Driver, and the Driver is further connected with a base electrode of the MOS tube MOSFET-N, wherein the logic output device is used for driving the Driver to control the switch of the MOS tube MOSFET-N at a first preset frequency when the feedback voltage signal is greater than a first preset voltage threshold value; when the feedback voltage signal is not greater than a first preset voltage threshold and greater than a second preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to the frequency corresponding to the PWM square wave signal with the preset duty ratio; when the feedback voltage signal is not greater than a second preset voltage threshold and greater than a third preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to a second preset frequency; when the feedback voltage signal is not greater than a third preset voltage threshold value, the Driver is driven to control the MOS tube to be in a turn-off state
In another possible implementation manner, the switch unit further includes a compensator, where the compensator includes a first input port, a second input port, and an output port, where the first input port of the compensator is configured to be connected to the source terminal CS and receive a signal collected by the source terminal CS, the second input port of the compensator is connected to the oscillator OSC, and the output port is connected to the PWM modulator and is configured to compensate a sawtooth wave signal generated by the oscillator OSC according to the collected signal and send the compensated signal to the PWM modulator, so that the PWM modulator determines, according to the compensated signal and the feedback voltage signal, a PWM square wave signal with a preset duty ratio corresponding to a current load.
In another possible implementation manner, the switch unit further includes an overvoltage protection unit and a logic or gate, where a positive input terminal of the overvoltage protection unit is used as an overvoltage protection terminal OVP and is configured to receive a collected voltage value, a negative input terminal of the overvoltage protection unit is configured to receive a reference voltage, the overvoltage protection unit is configured to output a stop signal when the collected voltage value is higher than the reference voltage, the output terminal of the overvoltage protection unit outputs the stop signal, one input terminal of the logic or gate is configured to be connected to the output terminal of the overvoltage protection unit, another input terminal of the logic or gate is configured to be connected to the PWM modulator, and an output terminal of the logic or gate is connected to the soft start circuit and is configured to control the soft start circuit to stop working when the overvoltage protection unit outputs the stop signal.
To sum up, the application comprises the following beneficial technical effects:
1. the input power module is rectified into a direct current signal by a municipal power supply and then output, the transformer is conducted according to a preset frequency under the control of the switch control module, namely the transformer is controlled to be conducted for a preset duration in a period, when the transformer is conducted, a primary coil of the transformer continuously accumulates energy, when the transformer is turned off, the accumulated energy is transmitted to a secondary coil, then a voltage stabilizing and filtering module connected with the secondary coil converts an alternating current signal into a direct current power supply signal to supply power to a load, when the preset frequency is higher, the preset duration representing the conduction of the transformer is shortened, the current for supplying power to the load is reduced, the size of the preset frequency is adjusted according to the load to adapt to the power consumption requirements of different loads, and the power consumption during light load or no load is reduced; the preset frequency is determined by the switch control module according to the feedback voltage signal fed back, the condition of the current load is determined according to different feedback voltage signals, and the corresponding preset frequency is selected according to the condition of the current load.
2. When the feedback voltage signal represents the condition of a load, the feedback voltage signal represents that the load is heavy load at the moment when the feedback voltage signal is greater than a first preset voltage threshold, and a Driver of a driving Driver controls an MOSFET-N switch of an MOS tube at a first preset frequency, namely when the load is heavy load, a primary coil of a transformer is controlled to be switched on or switched off at a constant first preset frequency; when the load is a medium load, controlling the conduction or the disconnection of a primary coil of the transformer according to the preset duty ratio of the PWM square wave signal modulated by the PWM modulator by the driving Driver; when the load is light, the MOSFET-N of the MOS transistor is switched on and off at a second preset frequency; when the load is in no load, the load can be continuously kept in a disconnected state, different power supply modes are determined according to different loads, and further power consumption can be reduced, so that different load requirements can be met.
Drawings
Fig. 1 is a circuit diagram of a high-frequency switching power supply circuit according to an embodiment of the present application;
FIG. 2 is a circuit diagram of a switch unit according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a compensation curve according to an embodiment of the present application;
FIG. 4 is a schematic diagram of a switching frequency curve according to an embodiment of the present application;
description of reference numerals: 1. an input power module; 11. a surge protection unit; 12. a rectifying unit; 13. a filtering unit; 2. a load; 3. a switch unit; 31. a soft start circuit; 311. a logic follower; 312. an SR flip-flop; 32. a PWM modulator; 33. a compensator; 34. an overvoltage protection unit; 35. a logic OR gate; 4. a transformer; 5. a voltage stabilizing and filtering module; 6. a feedback module; 7. a high voltage start module; 8. a buffer unit.
Detailed Description
The present application is described in further detail below with reference to figures 1-4.
The embodiment of the application discloses high frequency switching power supply circuit, refer to fig. 1, high frequency switching power supply circuit is connected with input power module 1 and load 2, and input power module 1 is used for converting municipal power supply into direct current signal output to high frequency switching power supply circuit.
Specifically, referring to fig. 1, the input power supply module 1 includes a surge protection unit 11, a rectification unit 12, and a filtering unit 13. The surge protection unit 11 is used for receiving the municipal power supply, is also connected with the rectification unit 12, is used for outputting the municipal power supply to the rectification unit 12 when the municipal power supply is normal, and is also used for disconnecting when the municipal power supply has a surge so as to disconnect the connection between the rectification unit 12 and the municipal power supply. When there is inrush current in municipal power supply, can utilize surge protection unit 11 to switch the disconnection between municipal power supply and rectifier unit 12, and then reduce inrush current and flee into high frequency switching power supply circuit and load 2, produce harmful effects to high frequency switching power supply circuit's components and parts and to load 2.
Referring to fig. 1, the input power supply module 1 is provided with two ports for connecting with a municipal power supply, namely an L port and an N port, the rectifying unit 12 includes a positive input end, a positive output end, a negative input end and a negative output end, the positive input end of the rectifying unit 12 is connected with the L port, the negative input end of the rectifying unit 12 is connected with the N port, receives the 220V alternating current municipal power supply, and rectifies and outputs the municipal power supply; the negative output end of the rectifying unit 12 is grounded, the positive output end is connected with the filtering unit 13, and the rectified electric signal is filtered by the filtering unit 13 and then outputs a direct current electric signal to the high-frequency switching power supply circuit.
Specifically, referring to fig. 1, the surge protection unit 11 includes a fuse F having one end connected to the L port and the other end connected to the positive input terminal of the rectifying unit 12, and a thermistor NTC having one end connected to the negative input terminal of the rectifying unit 12 and the other end connected to the N port. When the power supply is normal, the fuse F and the thermistor NTC are in normal states, and the current flows normally; when the system generates surge current, the fuse F is fused to further reduce the damage of the surge current to each working element.
Specifically, the rectifying unit 12 may adopt a full-bridge rectifying circuit, a half-bridge rectifying circuit, or the like, and may also adopt a packaged full-bridge rectifying module, for example, a bridge rectifying module of the DB 207. The embodiments of the present application are not limited, and a packaged full-bridge rectifier module is preferred. The rectifying unit 12 is used for rectifying the municipal power supply into a pulsating direct current signal, but an alternating current ripple is likely to exist in the rectified pulsating direct current signal, so that the direct current signal rectified by the rectifying unit 12 needs to be filtered by the filtering unit 13 before being transmitted to a subsequent circuit.
Referring to fig. 1, the filtering unit 13 includes a first polarity capacitor EC1, a second polarity capacitor EC2, a first resistor R1, a first inductor L1, and a second inductor L2, specifically, a positive output end is connected to a positive polarity end of the first polarity capacitor EC1, a negative output end is connected to a negative polarity end of the first polarity capacitor EC1, one end of the first inductor L1 is connected to the positive polarity end of the first polarity capacitor EC1, the other end is connected to a positive polarity end of the second polarity capacitor EC2, and a high-frequency switching power supply circuit for outputting a filtered dc signal, the negative polarity end of the second polarity capacitor EC2 is grounded, two ends of the first resistor R1 are respectively connected to the negative polarity end of the first polarity capacitor EC1 and the negative polarity end of the second polarity capacitor EC2, and the second inductor L2 is connected between the negative output end and the ground. The DC signal is filtered by an inductor and a capacitor.
Further, referring to fig. 1, the high frequency switching power supply circuit includes: the device comprises a switch control module, a transformer 4, a voltage stabilizing and filtering module 5 and a feedback module 6; the transformer 4 includes a primary coil, a secondary coil, and an auxiliary coil; one end of the primary coil is connected with the input power supply module 1, and the other end of the primary coil is connected with the switch control module and used for receiving the direct current electric signal, conducting or disconnecting the direct current electric signal under the control of the switch control module according to the preset frequency and generating a first alternating current electric signal; the secondary coil is coupled with the primary coil, and two ends of the secondary coil are also respectively connected with two ends of the voltage stabilizing and filtering module 5, and the secondary coil is used for receiving a second alternating current signal and sending the second alternating current signal to the voltage stabilizing and filtering module 5, and the second alternating current signal is a signal of the first alternating current signal which is subjected to voltage reduction and coupling to the secondary coil through the transformer 4; the voltage stabilizing and filtering module 5 is further connected with the load 2, and is configured to stabilize and filter the second alternating current signal to generate a direct current power supply signal, and output the direct current power supply signal to the load 2 to supply power to the load 2.
The auxiliary coil of the transformer 4 is coupled with the secondary coil, and is used for being connected with the switch control module to supply power to the switch control module.
Specifically, when the switch control module controls the primary coil to be turned on, the direct current signal received by the primary coil is stepped down by the transformer 4, and when the switch control module controls the primary coil to be turned off, the direct current signal received by the primary coil cannot circulate, that is, the direct current signal cannot be stepped down by the transformer 4, that is, the voltage value after the voltage value is reduced by the transformer 4 is zero, so that in the process of turning on and off the primary coil, the received direct current signal generates a first alternating current signal due to the switching of the primary coil, wherein the first alternating current signal is a pulse-form electric signal, a high-level period of the pulse is an on period of the primary coil, and the amplitude is equal to the amplitude of the direct current signal, a low-level period of the pulse-form electric signal is an off period of the primary coil, and the frequency of the first alternating current signal is equal to the preset frequency; then the first alternating current signal is transformed by the transformer 4 to generate a second alternating current signal to the secondary coil, and the frequency of the second alternating current signal is also equal to the preset frequency; and then, the second alternating current signal is converted into a direct current power supply signal by using a voltage stabilizing and filtering module 5 connected with the secondary coil, and the direct current power supply signal is supplied to the load 2 so as to realize power supply for the load 2.
Wherein, utilize the mode of high frequency switch, change the direct current signal into first alternating current signal earlier, step down to second alternating current signal again, later generate the direct current supply signal after carrying out steady voltage filtering with second alternating current signal and for load 2 power supplies, transformer 4's small, the loss is little, so be favorable to reducing the consumption for load 2 power supplies, improve power conversion efficiency, transformer 4's volume also reduces by a wide margin to linear power relatively simultaneously, more adapts to computer equipment's requirement.
Specifically, referring to fig. 1, the switch control module includes a switch unit 3, a diode D2, a resistor R6, a resistor CSR1, and a resistor CSR2, the switch unit 3 includes a DRAIN terminal DRAIN, a source terminal CS, and a power supply terminal VDD, wherein an anode of the diode D2 is connected to a dotted terminal of the auxiliary winding, a cathode of the diode D2 is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the power supply terminal VDD of the switch control module, one end of the resistor CSR1 is connected to the CS, the other end is grounded, the resistor CSR2 is connected in parallel to the resistor CSR1, and the DRAIN terminal DRAIN is connected to the dotted terminal of the primary winding. The signal outputted by the auxiliary winding is alternating current, and after passing through the diode D2, the alternating current is converted into direct current and outputted to the VDD pin, and supplies power to the switching unit 3, so that the DRAIN terminal DRAIN and the source terminal CS of the switching unit 3 are turned on or off, for example, during the period when the signal outputted by the auxiliary winding is high level after passing through the diode D2, the DRAIN terminal DRAIN and the source terminal CS of the switching unit 3 are turned on, and further the end with the same name of the primary coil is connected with the ground to form a conducting path, and at this time, the primary coil accumulates energy; when the voltage is low, the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are in an off state, that is, the dotted terminal of the primary coil does not form a conductive path, and at this time, the primary coil of the transformer 4 releases energy and transmits the energy to the secondary coil, and then the voltage stabilizing and filtering module 5 connected to the secondary coil obtains direct current, thereby realizing power supply to the load 2.
The voltage stabilizing and filtering module 5 connected between the secondary coil and the load 2 is configured to convert the second ac signal into a dc power supply signal to the load 2, and specifically, referring to fig. 1, the voltage stabilizing and filtering module 5 includes a diode D3, a resistor R7, a resistor R8, a capacitor C3, a resistor R9, a resistor FBR1, a resistor FBR2, a fourth-polarity capacitor EC4, and a zener diode, wherein an anode of the diode D3 is connected to a dotted terminal of the secondary coil, a cathode of the diode D3 is configured to be connected to the load 2, one end of the resistor R7 is connected to a cathode of the diode D3, the other end of the resistor R7 is connected to one end of the resistor R8, the other end of the resistor R8 is connected to a cathode of the zener diode, an anode of the zener diode is grounded, one end of the resistor FBR1 is connected to a cathode of the diode D3, the other end of the resistor FBR2 is connected to a ground, a positive-polarity end of the fourth-polarity capacitor EC4 is connected to a cathode of the diode D3, and a negative-polarity end of the fourth capacitor EC4 is grounded.
The first alternating current signal output by the primary coil is subjected to voltage reduction through the transformer 4, and then the second alternating current signal is output by the secondary coil, wherein the voltage reduction proportion is determined according to the number of turns of the primary coil and the number of turns of the secondary coil; then, by using the one-way conductivity of the diode D3 and the charge maintaining function of the fourth-polarity capacitor EC4, a direct current is obtained, that is, a direct current supply signal is obtained to the load 2 to supply power to the load 2.
Further, when the load 2 is light load, heavy load or no load, the magnitude of the dc power supply signal can be adjusted by changing the preset frequency of the switch control module, that is, when a large current needs to be provided, the duration of the switch control module controlling the conduction of the primary coil in one period is increased. Referring to fig. 1, the embodiment of the present application further includes a feedback module 6, where the feedback module 6 is connected to the load 2 and is further connected to the switch control module, and is configured to collect the dc power supply signal and generate a feedback voltage signal to the switch control module, so that the switch control module determines the preset frequency according to the feedback voltage signal. The switch control module is used for determining the preset frequency corresponding to the current load 2 according to the feedback voltage signal and controlling the conduction of the primary coil according to the preset frequency corresponding to the current load 2. The current corresponding to the dc power supply signal output to the load 2 can be adjusted by adjusting the preset frequency of the primary coil. The feedback module 6 is used to collect the voltage of the load 2 and transmit the voltage of the load 2 to the switch control module, so that the switch control module adjusts the voltage applied to the load 2 to reduce the loss when a large current or a large voltage is still supplied to the load 2 during light load or no load.
Specifically, referring to fig. 1, the feedback module 6 includes an optocoupler and a capacitor C2, the switch unit 3 includes a feedback terminal FB, wherein an anode terminal of the optocoupler is connected to one end of the resistor R8 connected to the resistor R7, a cathode terminal of the optocoupler is connected to the other end of the resistor R8, a collector of the optocoupler is connected to the feedback terminal FB, an emitter of the optocoupler is grounded, one end of the capacitor C2 is connected to the collector of the optocoupler, and the other end of the capacitor C2 is grounded. The optical coupler is used for generating a feedback voltage signal which is in direct proportion to the voltage of the load 2 and feeding the feedback voltage signal back to the switch unit 3, and the switch unit 3 adjusts the preset frequency according to the voltage value of the feedback voltage signal so as to reduce the loss in the light load process.
In addition, referring to fig. 1, a buffer unit 8 is bridged between the end of the primary coil with the same name and the end of the primary coil with the same name, the buffer unit 8 includes a diode D1, a resistor R5, a resistor R4 and a capacitor C1, wherein the anode of the diode D1 is connected with the end of the primary coil with the same name, the cathode is connected with one end of the resistor R5, the other end of the resistor R5 is connected with one end of the resistor R4, the other end of the resistor R4 is connected with the end of the primary coil with the different name, the capacitor C1 is connected in parallel with the two ends of the resistor R4, and the buffer unit 8 plays a buffer role.
Further, in order to reduce power consumption of the high-frequency switching power supply circuit during starting and standby, referring to fig. 1, the high-frequency switching power supply circuit is provided with a high-voltage starting module 7, wherein the high-voltage starting module 7 is connected with the input power supply module 1 and is used for receiving a direct-current electric signal; the high-voltage starting module 7 is also connected with the switch control module and is used for driving the switch control module to start working after a preset time length when receiving the direct current signal.
Specifically, referring to fig. 1, the high voltage starting module 7 includes a resistor R2, a resistor R3, and a third polar capacitor EC3, wherein one end of the resistor R2 is connected to the input power module 1 for receiving a direct current electrical signal; the other end of the resistor R2 is connected to one end of a third resistor R3, the other end of the third resistor R3 is connected to the positive polarity end of the third polar capacitor EC3, the negative polarity end of the third polar capacitor EC3 is grounded, and the negative polarity end of the third polar capacitor EC3 is connected to the power supply terminal VDD of the switch control module.
When the high-frequency switching power supply is started, a direct-current signal starts to charge the third polar capacitor EC3 through the resistor R2 and the resistor R3, the third polar capacitor EC3 starts to be charged continuously until the voltage at the positive polarity end of the third polar capacitor EC3 reaches the preset turn-on voltage of the switching unit 3, at this time, the switching unit 3 starts to control the primary coil to be turned on or off according to the preset frequency, then, in the normal process of powering the load 2, the electric signal coupled by the auxiliary coil supplies power to the switching unit 3, namely, after the high-frequency switching power supply is started, the high-voltage starting module 7 supplies power to the switching unit 3, compared with a circuit without the high-voltage starting module 7, when the high-voltage starting module 7 is not arranged, in the initial process of starting, continuous working is needed, the switching control module needs to be in a working state at the moment of starting, power consumption is large, and power consumption can be reduced by adopting the high-voltage starting module 7.
Referring to fig. 1, a switch control module includes a switch unit 3, a diode D2, a resistor R6, a resistor CSR1, and a resistor CSR2, the switch unit 3 includes a DRAIN terminal DRAIN, a source terminal CS, and a power terminal VDD, wherein an anode of the diode D2 is connected to a dotted terminal of an auxiliary winding, a cathode of the diode D2 is connected to one end of the resistor R6, another end of the resistor R6 is connected to the power terminal VDD of the switch control module, one end of the resistor CSR1 is connected to the source terminal CS, another end is grounded, the resistor CSR2 is connected in parallel to the resistor CSR1, and the DRAIN terminal DRAIN is connected to the dotted terminal of the primary winding. The signal outputted by the auxiliary winding is an alternating current, and after passing through the diode D2, the signal is converted into a direct current and outputted to the VDD pin, so as to supply power to the switch unit 3, so that the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are turned on or off, for example, during the period when the signal outputted by the auxiliary winding is high level after passing through the diode D2, the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are turned on, and further the dotted terminal of the primary winding is connected with the ground to form a conductive path, and at this time, the primary winding accumulates energy; when the voltage is low, the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are in an off state, that is, the dotted terminal of the primary coil does not form a conductive path, and at this time, the primary coil of the transformer 4 releases energy and transmits the energy to the secondary coil, and then the voltage stabilizing and filtering module 5 connected to the secondary coil obtains direct current, thereby realizing power supply to the load 2.
Further, the switch unit 3 is configured to control the primary coil to be turned on or off according to a preset frequency, and in order to implement a function of switching according to the preset frequency, referring to fig. 2, the switch unit 3 in the embodiment of the present application includes a MOS transistor MOSFET-N, a soft start circuit 31, an oscillator OSC, and a PWM modulator 32, where a DRAIN of the MOS transistor MOSFET-N is used as a DRAIN terminal DRAIN, a source is used as a source terminal CS, and a base is connected to the soft start circuit 31; the oscillator OSC is configured to generate a sawtooth wave signal, and the PWM modulator 32 includes a positive input terminal, a negative input terminal, and an output terminal, where the positive input terminal is connected to the oscillator OSC and is configured to receive the sawtooth wave signal, the negative input terminal is connected to the feedback terminal FB and is configured to receive a feedback voltage signal, and the output terminal is connected to the soft start circuit 31 and is configured to generate a PWM square wave signal with a preset duty ratio according to a ramp signal and a feedback voltage value signal and output the PWM square wave signal to the soft start circuit 31; the soft start circuit 31 is configured to control the MOS transistor MOSFET-N to be turned on according to a preset frequency corresponding to a preset duty ratio according to the PWM square wave signal of the preset duty ratio.
The sawtooth wave signal generated by the oscillator OSC is a preset signal, when the load 2 changes, the corresponding feedback voltage signal changes according to the change of the load 2, and at the same time, the PWM modulator 32 outputs a high level when the feedback voltage is higher than the sawtooth wave signal, and outputs a low level when the feedback voltage is lower than the sawtooth wave signal, thereby generating a PWM square wave signal with a preset duty ratio. The soft start circuit 31 controls the conduction or the disconnection of the source electrode and the drain electrode of the MOS tube MOSFET-N according to a preset duty ratio, controls the conduction of the source electrode and the drain electrode of the MOS tube MOSFET-N when a PWM square wave signal is in a high level, controls the disconnection of the source electrode and the drain electrode of the MOS tube MOSFET-N when the PWM square wave signal is in a low level, and adjusts the current value supplied to the load 2 by generating a direct current power supply signal by adjusting the conduction time of the source electrode and the drain electrode of the MOS tube MOSFET-N, so that the power supply current supplied to the load 2 is adjusted according to different loads 2, the conduction duration of the MOS tube MOSFET-N is shortened during light load, and the power consumption can be further reduced.
Still further, referring to fig. 2, the soft-start circuit 31 includes a Driver, a Logic follower 311 (shown as a Protect Logic), and an SR flip-flop 312, wherein the Logic follower 311 includes a first input terminal, a second input terminal, and an output terminal; the S terminal of the SR flip-flop 312 is connected to the oscillator OSC, the R terminal of the SR flip-flop 312 is connected to the output terminal of the PWM modulator 32, and the Q terminal of the SR flip-flop 312 is connected to the first input terminal of the logic output 311, and is configured to send the PWM square wave signal with the preset duty ratio to the logic output 311; the second input end of the logic output unit 311 is configured to receive a feedback voltage signal input by the feedback end FB, the output end of the logic output unit 311 is connected to a Driver, the Driver is further connected to a base of the MOS transistor MOSFET-N, and the logic output unit 311 is configured to determine a preset frequency according to the feedback voltage signal, where the logic output unit 311 is configured to drive the Driver to control the MOS transistor MOSFET-N to be turned on at a first preset frequency when the feedback voltage signal meets a preset condition.
Specifically, after receiving a feedback voltage signal fed back by a feedback end FB, the logic output device 311 determines the type of the load 2 carried by the current power supply according to the feedback voltage signal, and when the feedback voltage signal meets a preset condition, it indicates that the load 2 carried by the current switching power supply belongs to a heavy load, wherein when the feedback voltage signal is greater than a first preset voltage threshold, the feedback voltage signal meets the preset condition, and when the load is heavy, the load 2 is driven in a constant current manner, so that the requirement of the load 2 can be better met, and when the load is heavy, the logic output device 311 outputs a mode signal indicating a first preset frequency to a Driver, and the Driver controls the MOSFET-N of the MOS transistor to be turned on at the first preset frequency; when the feedback voltage signal does not meet the preset condition, representing that the load 2 carried by the current power supply belongs to medium load, light load or no load, namely the feedback voltage signal is not greater than a first preset voltage threshold; during medium load, light load or no load, the on-time of the MOSFET-N of the MOS transistor should be reduced, the current flowing to the load 2 is reduced, and the power loss is reduced.
In a possible implementation manner, when the logic output unit 311 determines that the feedback voltage signal does not satisfy the preset condition, the Driver may be controlled to control the MOS transistor MOSFET-N to switch at the preset switching frequency, where a conducting duration corresponding to the second preset frequency is shorter than a conducting duration corresponding to the preset switching frequency, so as to reduce the conducting duration compared with a heavy load condition, so as to reduce a current flowing to the load 2, thereby being beneficial to reducing power loss.
However, when the MOS transistor MOSFET-N is directly driven to be turned on at the preset switching frequency, the load carrying capacity of the medium load becomes weak and is difficult to adapt to the situation of the loaded load 2, and when the current still flows during no load, the MOS transistor MOSFET-N still generates unnecessary power loss due to high-frequency switching, so that in order to reduce the power loss during no load and enhance the load carrying capacity during light load, in another possible implementation manner, when the logic output device 311 determines that the feedback voltage signal does not meet the preset condition, the Driver is controlled to drive the MOS transistor MOSFET-N to be turned on or off according to the PWM square wave signal with the preset duty ratio output by the current PWM modulator 32; the PWM square wave signal with the preset duty ratio is a signal obtained by modulating the PWM modulator 32 according to the feedback voltage signal in real time, when the load 2 is heavier, the higher the voltage value corresponding to the feedback voltage signal is, the longer the time that the square wave in the PWM square wave signal is at a high level is, and further according to the condition of the load 2, the switching frequency of the current MOS transistor MOSFET-N is adjusted, and further the current value flowing into the load 2 is adjusted, and when the load is light, the load capacity can be adjusted according to the condition of the load 2 to adapt to the requirement of the load 2, and when the load is no-load, the current flowing to the load 2 can be effectively reduced, and the power loss is further reduced.
Still further, because there is still current circulation when no load, there is still power loss, so when the logic controller judges that the feedback voltage signal does not satisfy the preset condition, the mode of controlling the MOSFET-N switch of the MOS transistor may also be a third mode, where the third mode is:
when the logic controller judges that the feedback voltage signal does not meet the preset condition (when the feedback voltage signal is not greater than the first preset voltage threshold), the logic controller judges whether the feedback voltage signal is greater than a second preset voltage threshold or not again, if the feedback voltage signal is greater than the second preset voltage threshold, the current load 2 is represented as a medium load, and at the moment, the PWM square wave signal based on the preset duty ratio drives the MOSFET-N to be conducted, so that the medium load has stronger on-load capacity, the current output to the load 2 is automatically adjusted according to the load 2, and the power consumption is further reduced.
When the feedback voltage signal is not greater than the second preset voltage threshold, the light load or no-load state is represented, power supply is still needed when the light load is carried out, and power supply is needed when the no-load state is carried out.
When the feedback voltage signal is not greater than a third preset voltage threshold, it represents that the load 2 is in an idle state at this time, and in order to reduce power consumption during idle, the logic output unit 311 controls the driver to stop working, that is, the driver controls the MOS transistor MOSFET-N to be in a state of continuous disconnection, and continues to judge whether the feedback voltage signal meets the step of the preset condition until the feedback voltage signal is judged to be greater than the first preset voltage threshold, and controls the driver to switch on the MOS transistor MOSFET-N at a first preset frequency; or judging that the feedback voltage signal is smaller than a first preset voltage threshold and larger than a second preset voltage threshold so as to enable the MOS transistor MOSFET-N to drive the MOS transistor MOSFET-N to be conducted based on the PWM square wave signal with the preset duty ratio, or judging that the feedback voltage signal is not larger than the second preset voltage threshold and larger than a third preset voltage threshold so as to enable the MOS transistor MOSFET-N to be switched on and off at a second preset frequency.
When the feedback voltage signal is greater than a first preset voltage threshold, the feedback voltage signal is characterized to be in a heavy load state at the moment, the MOSFET-N of the MOS tube is controlled to be switched at a first preset frequency, when the feedback voltage signal is not greater than the first preset voltage threshold but is greater than a second preset voltage threshold, the feedback voltage signal is characterized to be in a medium load state at the moment, the MOSFET-N of the MOS tube is controlled to be driven to be in a light load state based on a PWM square wave signal with a preset duty ratio, when the feedback voltage signal is not greater than the second preset voltage threshold and is greater than a third preset voltage threshold, and the MOSFET-N of the MOS tube is controlled to be switched at a second preset frequency; and when the feedback voltage signal is not greater than a third preset voltage threshold, keeping the MOSFET-N of the control MOS tube in a disconnected state, and circularly judging whether the feedback voltage signal is greater than the first preset voltage threshold or not until the feedback voltage signal is greater than the first preset voltage threshold, or the feedback voltage signal is not greater than the first preset voltage threshold and is greater than the second preset voltage threshold, or the feedback voltage signal is not greater than the second preset voltage threshold and is greater than the third preset voltage threshold. The first preset voltage threshold is greater than a second preset voltage threshold, and the second preset voltage threshold is greater than a third preset voltage threshold. Therefore, the switching frequency is determined according to the feedback voltage signal when the switching frequency is in a down-conversion mode under the condition of heavy load and fixed switching frequency, namely a first preset frequency, and under the condition of medium load; when the load is light or no-load, the frequency hopping circuit works in a frequency hopping mode, stops switching when the load is no-load, and switches at a second preset frequency when the load is light, so that high efficiency can be kept under the full-load working condition, and the requirement of six-level energy efficiency is met.
Referring to fig. 2, in order to reduce harmonics in the PWM square wave signal, the switching unit 3 further includes a compensator 33, where the compensator 33 includes a first input port, a second input port, and an output port, where the first input port of the compensator 33 is configured to be connected to the source terminal CS and receive a signal collected by the source terminal CS, the second input port of the compensator 33 is connected to the oscillator OSC, and the output port is connected to the PWM modulator 32 and is configured to compensate the sawtooth wave signal generated by the oscillator OSC according to the collected signal, and send the compensated signal to the PWM modulator 32, so that the PWM modulator 32 determines the PWM square wave signal with the preset duty ratio corresponding to the current load 2 according to the compensated signal and the feedback voltage signal. The compensator 33 superimposes the signal collected by the source terminal CS and the sawtooth wave signal generated by the oscillator OSC, superimposes the sawtooth wave signal on the basis of the signal collected by the source terminal CS to compensate, and transmits the compensated signal to the PWM modulator 32, so that the PWM modulator 32 performs PWM square wave modulation, thereby effectively reducing the harmonic generation probability in the high-frequency switching power supply circuit, and further facilitating the stabilization of the system.
Specifically, when the duty ratio of the preset frequency of the switch is greater than 50%, there is an instability problem, and at this time, a sawtooth wave signal generated by the oscillator OSC is superimposed on the waveform of the source terminal CS to realize slope compensation, and then the value is input to the PWM modulation apparatus. The compensation principle is schematically illustrated, as shown in fig. 3:
where-m is the slope of the compensation harmonic, from O Induced current error I 1 Comprises the following steps:
Figure BDA0003802307070000151
if the current loop is stable:
Figure BDA0003802307070000152
and because:
D×m 1 ＝(1-D)m 2
therefore:
Figure BDA0003802307070000153
in Flyback, D max Typically 70-80%, so that m is typically 0.3 × m 2 。
Referring to fig. 2, the switch unit 3 further includes an overvoltage protection unit 34 and a logic or gate 35, where a positive input terminal of the overvoltage protection unit 34 is used as an overvoltage protection terminal OVP and is configured to receive a voltage value collected by the switch unit 3, a negative input terminal of the overvoltage protection unit 34 is configured to receive a reference voltage, the overvoltage protection unit 34 is configured to output a stop signal and output the stop signal by an output terminal of the overvoltage protection unit 34 when the collected voltage value is higher than the reference voltage, one input terminal of the logic or gate 35 is configured to connect an output terminal of the overvoltage protection unit 34, another input terminal of the logic or gate 35 is configured to be connected to the PWM modulator 32, and an output terminal of the logic or gate 35 is connected to the soft start circuit 31 and is configured to control the soft start circuit 31 to stop working when the overvoltage protection unit 34 outputs the stop signal.
Specifically, when the voltage value received by the switch unit 3 is greater than the reference voltage, the voltage value that is currently collected by the switch unit 3 is represented as overvoltage, at this time, the overvoltage protection unit 34 outputs a high-level stop signal to the logical or gate 35, after the logical or gate 35 receives the high-level stop signal, no matter the PWM modulator 32 outputs a high level or a low level at this time, the high-level stop signal is input to the soft start circuit 31, and at this time, the soft start circuit 31 controls the MOS transistor MOSFET-N to stop working.
Further, referring to fig. 2, in order to improve the safety of the switch unit 3, the switch unit 3 further includes an over-current protection unit OCP, wherein one end of the or gate 35 connected to the output end of the overvoltage protection unit 34 is also connected to the output end of the over-current protection unit OCP, a positive input end of the over-current protection unit OCP is used for receiving a current value input by the source terminal CS, a negative input end of the over-current protection unit OCP is connected to a reference current value, when the current is higher than the reference current value, the over-current protection unit will output a turn-off signal with a logic high level to the or gate 35, the or gate 35 will output a stop signal with a high level, and the soft start circuit 31 will stop working, that is, the MOSFET-N of the MOS transistor will keep the turn-off state unchanged. Therefore, when the switching unit 3 detects that the current flowing into the switching unit 3 exceeds the reference current value and/or the voltage value exceeds the reference voltage value, the operation is stopped, the damage of the overvoltage and/or the overcurrent to the switching unit 3 is reduced, and the safety of the switching unit 3 is improved.
Referring to fig. 2, the switch unit 3 further includes a blanker LEB, the blanker LEB is connected between the over-current detection unit and the source terminal CS, since a peak appears at a leading edge of the source terminal CS, and the current detection unit may be turned off in advance when the peak appears at the source terminal CS, the blanker LEB is utilized to enable the current detection unit to perform current detection after delaying for a preset time, and after delaying for the preset time, the peak at the leading edge of the source terminal CS is already ended, so that false detection of the current is reduced.
In a possible implementation manner, referring to fig. 2, the resistor R10 and the resistor R11 are connected to the overvoltage protection terminal OVP of the switch unit 3, wherein one end of the resistor R10 is connected to one end of the resistor R11 and then connected to the overvoltage protection terminal OVP, the other end of the resistor R10 is connected to the dotted end of the auxiliary coil, the other end of the resistor R11 is connected to the non-dotted end of the auxiliary coil, the overvoltage protection unit 34 determines whether the voltage of the auxiliary coil is higher than a reference voltage value according to the collected voltage of the auxiliary coil, and controls the switch unit 3 to stop working when the voltage is higher than the reference voltage value.
In another possible implementation manner, referring to fig. 2, the voltage received by the positive input terminal of the overvoltage protection unit 34 (i.e., the voltage received by the overvoltage protection terminal OVP) can also be indirectly detected by the voltage of the power terminal VDD, where the voltage of the VDD terminal is the voltage of the primary coil, and the ratio of the voltage of the auxiliary coil to the voltage of the primary coil is equal to the ratio of the number of turns of the auxiliary coil to the number of turns of the primary coil, and then the voltage of the auxiliary coil can be indirectly detected by the voltage of the VDD terminal. The relationship between the voltage at the VDD end and the output voltage is approximately as follows:
VDD＝(VOUT×NA)/NS
VDD is VDD voltage, VOUT is voltage received by the positive input terminal, NA is the number of turns of the auxiliary winding, and NS is the number of turns of the primary winding.
Further, referring to fig. 2, a voltage stabilizing diode is further connected to the gate of the MOS transistor MOSFET-N, the cathode of the voltage stabilizing diode is connected to the gate of the MOS transistor MOSFET-N, and the anode of the voltage stabilizing diode is grounded and used for stabilizing the voltage of the gate of the MOS transistor MOSFET-N, so as to reduce the instability problem caused by voltage jitter; still further, a VDD overvoltage protection device is connected between the power supply terminal VDD and the soft start circuit 31, and is configured to cut off the connection with the soft start circuit 31 when the power supply terminal VDD is connected to a voltage higher than a preset voltage threshold, so as to improve the safety of the switch unit 3.
Referring to fig. 2, the switch unit 3 is further provided with a band-gap reference voltage source BandgapIbias and an under-voltage protection device UVLO, and input ends of the band-gap reference voltage source BandgapIbias and the under-voltage protection device UVLO are both connected to the power supply terminal VDD, wherein the under-voltage protection device UVLO is used for protection when a voltage of the power supply terminal VDD is lower than a voltage value of the band-gap reference voltage source BandgapIbias.
Referring to fig. 2, in the embodiment of the present application, the Driver adopts a totem-pole driving structure, so that the EMI characteristic of the system can be better optimized; in addition, in order to prevent thermal damage, the switch unit 3 is further provided with a temperature detection module, which is configured to detect the temperature of the switch unit 3, and send a restart command to the connected soft start circuit 31 when the temperature exceeds a preset temperature threshold, so as to restart the soft start circuit 31. In addition, the switch unit 3 of the embodiment of the present application further adopts a frequency dithering technology, which can effectively improve the electromagnetic interference conduction and simplify the electromagnetic interference design of the system.
For the above embodiments, the present application provides an example to illustrate the process of controlling the MOSFET-N switches under different loads 2, referring to fig. 4, the chip operates under a heavy load mode (e.g. 85KHZ shown in fig. 4) at a fixed switching frequency, operates under a down-frequency mode (e.g. 25KHZ to 85KHZ shown in fig. 4) at a medium load, when the input voltage is fixed, the switching frequency increases with the increase of the load 2, whereas, when the load 2 is fixed, the switching frequency increases with the increase of the input voltage, that is, when the load 2 is fixed, the voltage value corresponding to the feedback voltage signal received by the feedback terminal FB gradually decreases, the switching frequency of the MOS MOSFET-N gradually decreases, operates under a light load, when the voltage value of the feedback voltage signal received by the feedback terminal FB is greater than the frequency hopping voltage, the MOS MOSFET-N switches are controlled according to a second preset frequency, and when the voltage value of the feedback voltage signal is lower than the frequency hopping voltage, the operation is stopped, the control of the MOSFET-N switches is stopped, the loss of the MOS MOSFET-N switches is effectively reduced, and the efficiency of the MOS MOSFET-N switch is maintained under the high frequency hopping efficiency condition.
The embodiment of the present application further provides a switching power supply, and referring to fig. 1 and fig. 2, the switching power supply includes the high-frequency switching power supply circuit in the above embodiment. This switching power supply's high frequency switching power supply circuit utilizes switching control module control primary coil to switch on or shut off according to predetermined frequency, the direct current after earlier the rectification is under the high frequency switch action, change first alternating current signal, later reuse transformer 4 with first alternating current signal step-down to second alternating current signal, utilize filtering voltage stabilization module to convert second alternating current signal into DC power supply signal at last and for load 2 power supply, utilize high frequency switch's mode, realize voltage transformation and steady voltage, wherein transformer 4's loss is little, so be favorable to reducing the consumption, improve power conversion efficiency, the volume of transformer 4 also reduces by a wide margin to linear power supply simultaneously.
An embodiment of the present application further provides a switch unit 3, and specifically, referring to fig. 2, the switch unit 3 includes: the circuit comprises a MOS tube MOSFET-N, a soft start circuit 31, an oscillator OSC and a PWM modulator 32, wherein the DRAIN electrode of the MOS tube MOSFET-N is used as a DRAIN electrode terminal DRAIN, the source electrode is used as a source electrode terminal CS, and the base electrode is connected with the soft start circuit 31; the oscillator OSC is configured to generate a sawtooth wave signal, and the PWM modulator 32 includes a positive input terminal, a negative input terminal, and an output terminal, where the positive input terminal is connected to the oscillator OSC and is configured to receive the sawtooth wave signal, the negative input terminal is connected to the feedback terminal FB and is configured to receive a feedback voltage signal, and the output terminal is connected to the soft start circuit 31 and is configured to generate a PWM square wave signal with a preset duty ratio according to a ramp signal and a feedback voltage value signal, and output the PWM square wave signal to the soft start circuit 31; the soft start circuit 31 is configured to control the MOS transistor MOSFET-N to be turned on according to a preset frequency corresponding to a preset duty ratio according to the PWM square wave signal of the preset duty ratio.
Specifically, the PWM modulator 32 generates a PWM square wave signal with a preset duty ratio, where the sawtooth wave signal is a preset signal, and when the load 2 changes, the corresponding feedback voltage signal changes according to the change of the load 2, so that the preset duty ratio of the PWM square wave signal modulated by the PWM modulator 32 changes along with the change of the load 2, and the soft start circuit 31 controls the source and the drain of the MOS transistor MOSFET-N to be turned on or off according to the preset duty ratio, so as to adjust the supply current supplied to the load 2 according to different loads 2, and further reduce power consumption.
Referring to fig. 2, the soft start circuit 31 includes a Driver, a logic output 311, and an SR flip-flop 312, where the logic output 311 includes a first input terminal, a second input terminal, and an output terminal;
the S end of the SR flip-flop 312 is connected to the oscillator OSC, the R end of the SR flip-flop 312 is connected to the output end of the PWM modulator 32, and the Q end of the SR flip-flop 312 is connected to the first input end of the logic output unit 311, and is configured to send the PWM square wave signal with the preset duty ratio to the logic output unit 311; the second input end of the logic output unit 311 is configured to receive a feedback voltage signal input by the feedback end FB, the output end of the logic output unit is connected to a Driver, and the Driver is further connected to a base of the MOS transistor MOSFET-N, where the logic output unit 311 is configured to drive the Driver to control the switching of the MOS transistor MOSFET-N at a first preset frequency when the feedback voltage signal is greater than a first preset voltage threshold; when the feedback voltage signal is not greater than a first preset voltage threshold and is greater than a second preset voltage threshold, controlling a driver to control an MOS tube MOSFET-N switch according to the frequency corresponding to the PWM square wave signal with the preset duty ratio; when the feedback voltage signal is not greater than a second preset voltage threshold and is greater than a third preset voltage threshold, controlling the driver to control the MOSFET-N switch of the MOS tube according to a second preset frequency; when the feedback voltage signal is not greater than a third preset voltage threshold, the driving driver controls the MOSFET-N of the MOS tube to be in a turn-off state
Referring to fig. 2, the switch unit 3 further includes a compensator 33, where the compensator 33 includes a first input port, a second input port, and an output port, where the first input port of the compensator 33 is used for being connected to the source terminal CS and receiving a signal collected by the source terminal CS, the second input port of the compensator 33 is connected to the oscillator OSC, and the output port is connected to the PWM modulator 32 and is used for compensating a sawtooth wave signal generated by the oscillator OSC according to the collected signal and sending the compensated signal to the PWM modulator 32, so that the PWM modulator 32 determines a PWM square wave signal with a preset duty ratio corresponding to the current load 2 according to the compensated signal and the feedback voltage signal.
Referring to fig. 2, the switch unit 3 further includes an overvoltage protection unit 34 and a logic or gate 35, where a positive input terminal of the overvoltage protection unit 34 is used as an overvoltage protection terminal OVP and is configured to receive a collected voltage value, a negative input terminal of the overvoltage protection unit 34 is configured to receive a reference voltage, the overvoltage protection unit 34 is configured to output a stop signal from an output terminal of the overvoltage protection unit 34 when the collected voltage value is higher than the reference voltage, one input terminal of the logic or gate 35 is configured to be connected to the output terminal of the overvoltage protection unit 34, another input terminal of the logic or gate 35 is configured to be connected to the PWM modulator 32, and an output terminal of the logic or gate 35 is connected to the soft start circuit 31 and is configured to control the soft start circuit 31 to stop working when the overvoltage protection unit 34 outputs the stop signal.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: equivalent changes in structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (10)

1. The high-frequency switching power supply circuit is characterized in that the power supply circuit is connected with an input power supply module (1) and a load (2), the input power supply module (1) is used for converting a municipal power supply into a direct-current signal and outputting the direct-current signal to the power supply circuit, and the power supply circuit comprises: the transformer-based power supply comprises a switch control module, a transformer (4), a voltage stabilizing and filtering module (5) and a feedback module (6), wherein the transformer (4) comprises a primary coil and a secondary coil;
one end of the primary coil is connected with the input power supply module (1), the other end of the primary coil is connected with the switch control module, and the primary coil is used for receiving the direct current signal, conducting or disconnecting the direct current signal according to a preset frequency under the control of the switch control module and generating a first alternating current signal;
the secondary coil is coupled with the primary coil, and is also respectively connected with two ends of the voltage-stabilizing filtering module (5) and used for receiving a second alternating current signal and sending the second alternating current signal to the voltage-stabilizing filtering module (5), wherein the second alternating current signal is a signal which is obtained by voltage-reducing and coupling the first alternating current signal to the secondary coil through a transformer (4);
the voltage stabilizing and filtering module (5) is further connected with the load (2) and is used for stabilizing and filtering the second alternating current electric signal to generate a direct current power supply signal, outputting the direct current power supply signal to the load (2) and supplying power to the load (2);
the feedback module (6) is connected with the load (2) and the switch control module, and is used for collecting the direct current power supply signal and generating a feedback voltage signal to the switch control module so that the switch control module determines the preset frequency according to the feedback voltage signal.
2. A high frequency switching power supply circuit according to claim 1, wherein said transformer (4) further comprises an auxiliary winding coupled to said secondary winding and further connected to said switching control module for supplying power to said switching control module to operate said switching control module.
3. The high frequency switching power supply circuit according to claim 1, further comprising a high voltage start-up module (7), wherein the high voltage start-up module (7) is connected to the input power supply module (1) for receiving the direct current signal; the high-voltage starting module (7) is further connected with the switch control module and used for driving the switch control module to start working after a preset time when the direct-current electric signal is received.
4. The high-frequency switching power supply circuit according to claim 1, wherein the switching control module comprises a switching unit (3), a resistor CSR1 and a resistor CSR2, wherein the switching unit (3) comprises a DRAIN terminal DRAIN, a source terminal CS, a feedback terminal FB and a power terminal VDD, the power terminal VDD is used for connecting a power supply to supply power to the switching unit (3), the feedback module (6) is connected with the feedback terminal FB and is used for feeding back a feedback voltage signal to the switching unit (3) through the feedback terminal FB, so that the switching unit (3) determines a preset frequency corresponding to the current load (2) according to the feedback voltage signal and controls the DRAIN terminal and the source terminal to be conducted according to the preset frequency; one end of the resistor CSR1 is connected with the source terminal CS, the other end is grounded, the resistor CSR2 is connected with the resistor CSR1 in parallel, and the DRAIN terminal DRAIN is connected with the same-name terminal of the primary coil.
5. The high frequency switching power supply circuit according to claim 4, wherein the switching unit (3) comprises a MOS transistor MOSFET-N, a soft start circuit (31), an oscillator OSC and a PWM modulator (32), wherein a DRAIN of the MOS transistor MOSFET-N is used as the DRAIN terminal DRAIN, a source is used as the source terminal CS, and a base is connected with the soft start circuit (31); the oscillator OSC is used for generating a sawtooth wave signal, the PWM modulator (32) comprises a positive input end, a negative input end and an output end, wherein the positive input end is connected with the oscillator OSC and used for receiving the sawtooth wave signal, the negative input end is connected with the feedback end FB and used for receiving a feedback voltage signal, the output end is connected with the soft start circuit (31) and used for generating a PWM square wave signal with a preset duty ratio according to a ramp signal and a feedback voltage value signal and outputting the PWM square wave signal to the soft start circuit (31); the soft start circuit (31) is used for controlling the MOS tube MOSFET-N to be conducted according to a preset frequency corresponding to a preset duty ratio according to a PWM square wave signal of the preset duty ratio.
6. The high frequency switching power supply circuit according to claim 5, wherein the soft start circuit (31) comprises a Driver, a logic output (311) and an SR flip-flop (312), the logic output (311) comprising a first input terminal, a second input terminal and an output terminal;
the S end of the SR trigger (312) is connected with the OSC, the R end of the SR trigger (312) is connected with the output end of the PWM modulator (32), and the Q end of the SR trigger (312) is connected with the first input end of the logic output device (311) and used for sending the PWM square wave signal with the preset duty ratio to the logic output device (311);
the second input end of the logic output device (311) is used for receiving a feedback voltage signal input by the feedback end FB, the output end of the logic output device is connected with a Driver, and the Driver is also connected with the base electrode of the MOS transistor MOSFET-N, wherein the logic output device (311) is used for driving the Driver to control the MOS transistor MOSFET-N switch at a first preset frequency when the feedback voltage signal is greater than a first preset voltage threshold value; when the feedback voltage signal is not greater than a first preset voltage threshold and greater than a second preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to the frequency corresponding to the PWM square wave signal with the preset duty ratio; when the feedback voltage signal is not greater than a second preset voltage threshold and greater than a third preset voltage threshold, controlling the Driver to control the MOSFET-N switch of the MOS tube according to a second preset frequency; and when the feedback voltage signal is not greater than a third preset voltage threshold, driving the Driver to control the MOSFET-N of the MOS tube to be in a turn-off state.
7. The high frequency switching power supply circuit according to claim 6, wherein the switching unit (3) further comprises a compensator (33), the compensator (33) comprises a first input port, a second input port and an output port, wherein the first input port of the compensator (33) is configured to be connected to a source terminal CS and receive a current collection signal collected by the source terminal CS, the second input port of the compensator (33) is connected to an oscillator OSC, and the output port is connected to the PWM modulator (32) and configured to compensate a sawtooth wave signal generated by the oscillator OSC according to the current collection signal and send the compensated signal to the PWM modulator (32) so that the PWM modulator (32) determines a PWM square wave signal with a preset duty ratio corresponding to the present load (2) according to the compensated signal and the feedback voltage signal.
8. A high frequency switching power supply circuit according to claim 3, wherein said high voltage starting module (7) comprises a resistor R2, a resistor R3 and a third polar capacitor EC3, wherein one end of said resistor R2 is connected to said input power supply module (1) for receiving a dc electrical signal, the other end of said resistor R2 is connected to one end of said resistor R3, the other end of said resistor R3 is connected to a positive polarity end of said third polar capacitor EC3, a negative polarity end of said third polar capacitor EC3 is grounded, and said switch control module is connected to a positive polarity end of said third polar capacitor EC 3.
9. A switching power supply comprising the high-frequency switching power supply circuit according to any one of claims 1 to 8.
10. A switch unit, characterized in that said switch unit (3) comprises a MOS transistor MOSFET-N, a soft start circuit (31), an oscillator OSC, and a PWM modulator (32), wherein the DRAIN of said MOS transistor MOSFET-N is used as said DRAIN terminal DRAIN, the source is used as said source terminal CS, and the base is connected to the soft start circuit (31); the oscillator OSC is used for generating sawtooth wave signals, the PWM modulator (32) comprises a positive input end, a negative input end and an output end, wherein the positive input end is connected with the oscillator OSC and used for receiving the sawtooth wave signals, the negative input end is connected with the feedback end FB and used for receiving feedback voltage signals, and the output end is connected with the soft start circuit (31) and used for generating PWM square wave signals with preset duty ratios according to ramp signals and feedback voltage value signals and outputting the PWM square wave signals to the soft start circuit (31); the soft start circuit (31) is used for controlling according to a PWM square wave signal with a preset duty ratio, and the MOS tube MOSFET-N is conducted according to a preset frequency corresponding to the preset duty ratio.
CN202210988061.8A 2022-08-17 2022-08-17 High-frequency switching power supply circuit, switching power supply and switching unit Active CN115276418B (en)

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