CN115276418B - 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
CN115276418B
CN115276418B CN202210988061.8A CN202210988061A CN115276418B CN 115276418 B CN115276418 B CN 115276418B CN 202210988061 A CN202210988061 A CN 202210988061A CN 115276418 B CN115276418 B CN 115276418B
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signal
power supply
preset
voltage
module
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CN115276418A (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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

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 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; the voltage stabilizing and filtering module is also connected with the load and used for generating a direct current power supply signal after voltage stabilizing and filtering the second alternating current signal and outputting the direct current power supply signal to the load; the feedback module is connected with the load and also connected with the switch control module and is used for collecting the direct current power supply signal and generating a feedback voltage signal so as to enable the switch control module to determine the preset frequency according to the feedback voltage signal.

Description

High-frequency switching power supply circuit, switching power supply and switching unit
Technical Field
The present disclosure 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 technology, electronic devices gradually enter the life of people, and devices such as mobile phones, computers, displays, household appliances, printers and the like have become common devices in daily life of people. For such devices, the components therein are mostly dc power, and the municipal power source is ac power, so for such devices, it is necessary to convert ac power into dc power to supply power to such devices.
The linear power supply is a power supply which is obtained by transforming alternating current through a transformer by utilizing the transformer and then rectifying and filtering the alternating current through a rectifying circuit.
However, the linear power supply has large power consumption, and the transformer used is large and heavy, so that the linear power supply is difficult to adapt to the power supply of computer equipment such as a computer.
Disclosure of Invention
In order to reduce 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, the power supply circuit being connected with an input power supply module and a load, the input power supply module being for converting municipal power supply into a direct current electrical signal and outputting to the power supply circuit, the power supply circuit comprising: the device comprises a switch control module, a transformer, a voltage stabilizing and filtering module and a feedback module, wherein 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 is used for receiving the direct current signal, switching on or switching off the primary coil 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, 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 of the first alternating current signal which is coupled to the secondary coil through voltage reduction of a transformer;
the voltage stabilizing and filtering module is also connected with the load and is used for generating a direct current power supply signal after voltage stabilizing and filtering the second alternating current signal and outputting the direct current power supply signal to the load to supply power to the load;
the feedback module is connected with the load and the switch control module, and is used for collecting the direct current power supply signal, 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.
Through adopting above-mentioned technical scheme, utilize switch control module control primary to turn on or turn off according to preset frequency, firstly with the direct current after the rectification under the high frequency switch action, change first alternating current signal, afterwards utilize the transformer to step down first alternating current signal into second alternating current signal, finally utilize filtering steady voltage module to change second alternating current signal into direct current power supply signal in order to supply power for the load, utilize the mode of high frequency switch, realize voltage transformation and steady voltage, wherein the loss of transformer is little, consequently, be favorable to reducing the consumption, improve power conversion efficiency, the volume of transformer also reduces by a wide margin relative to linear power supply simultaneously.
Further, the transformer is conducted according to a preset frequency under the control of the switch control module, namely the conduction preset time of the transformer is controlled in one period, when the transformer is conducted, the primary coil of the transformer continuously accumulates energy, when the transformer is turned off, the accumulated energy is transmitted to the secondary coil, and then the voltage stabilizing filter module connected with the secondary coil converts an alternating current signal into a direct current power supply signal to supply power for a load, when the preset frequency is larger, namely the conduction preset time of the transformer is smaller, then the current for supplying power for the load is reduced, the preset frequency is adjusted according to the load, so that the power consumption requirements of different loads are met, and the power consumption in light load or no load is reduced; the preset frequency is determined by the switch control module according to feedback voltage signals fed back, the current load condition is determined according to different feedback voltage signals, and the corresponding preset frequency is selected according to the current load condition.
In one possible implementation, the transformer further includes an auxiliary coil coupled to the secondary coil and further connected to the switch control module for powering the switch control module to operate the switch control module.
By adopting the technical scheme, the auxiliary coil of the transformer is used for supplying power to the switch control module, so that the switch control module works.
In another possible implementation manner, the high-frequency switching power supply circuit further comprises a high-voltage starting module, wherein the high-voltage starting module is connected with the input power supply module and is used for receiving the direct-current electric signal; the high-voltage starting module 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 passes when the direct current signal is received.
By adopting the technical scheme, in a preset time period after the high-frequency switching power supply circuit is started, the switch control module has larger power consumption, and in order to reduce the power consumption of the switch control module, the high-voltage starting module is used for supplying power to the switch control module after delaying for a preset time period.
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, where the power terminal VDD is used to connect to a power source to supply power to the switch unit, and the feedback module is connected to the feedback terminal FB and is used to feed back a feedback voltage signal 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 to the source terminal CS, the other end is grounded, the resistor CSR2 is connected in parallel with the resistor CSR1, and the DRAIN terminal DRAIN is connected with the same-name end of the primary coil.
By adopting the technical scheme, the switch unit determines the preset frequency of the current load according to the feedback voltage signal received by the feedback end FB, when the switch unit controls the DRAIN electrode end DRAIN to be conducted with the source electrode end CS, the primary coil of the transformer is in a conducting state, when the switch unit controls the DRAIN electrode end DRAIN to be disconnected with the source electrode end CS, the primary coil of the transformer is in a cutting-off state, and the switch unit controls the DRAIN electrode end DRAIN to be conducted with the source electrode end CS or cut off so as to control the conducting and cutting-off 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 a sawtooth wave signal, 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 is used for receiving the sawtooth wave signal, the negative input end is connected with the feedback end FB and is used for receiving a feedback voltage signal, the output end is connected with the soft start circuit and is used for generating a PWM square wave signal with a preset duty ratio according to the ramp signal and the feedback voltage value signal, and the PWM square wave signal is output to the soft start circuit; the soft start circuit is used for controlling the MOS transistor MOSFET-N to be conducted according to a PWM square wave signal with a preset duty ratio and a preset frequency corresponding to 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 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 on or off of the source electrode and the drain electrode of the MOS tube MOSFET-N according to the preset duty ratio, thereby realizing the adjustment of the power supply current supplied to the load according to different loads and further reducing the power consumption.
In another possible implementation manner, the soft start circuit includes a Driver, a logic output device, and an SR flip-flop, where the logic output device includes a first input terminal, a second input terminal, and an output terminal;
wherein the S end of the SR trigger is connected with the oscillator OSC, the R end of the SR trigger is connected with the output end of the PWM modulator, the Q end of the SR trigger is connected with the first input end of the logic output device and is used for sending PWM square wave signals with 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 is connected with the Driver, the Driver is also connected with the base electrode of the MOS transistor MOSFET-N, and when the feedback voltage signal is larger than a first preset voltage threshold value, the logic output device 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 not greater than a first preset voltage threshold value and is greater than a second preset voltage threshold value, 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 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 Driver is driven to control the MOS transistor MOSFET-N to be in an off state, the feedback voltage signal characterizes the condition of a load, when the feedback voltage signal is greater than the first preset voltage threshold, the load is characterized as heavy load, the Driver is driven to control the MOS transistor MOSFET-N switch at a first preset frequency, namely, when the load is heavy load, the primary coil of the transformer is kept to be controlled to be on or off at a constant first preset frequency; when the load is a medium load, the Driver is controlled to turn on or off the primary coil of the transformer according to the preset duty ratio of the PWM square wave signal modulated by the PWM modulator; when the load is light load, the MOS transistor MOSFET-N is switched at a second preset frequency; when the load is empty, the disconnection state is kept continuously, different power supply modes are determined according to different loads, and further reduction of power consumption is facilitated, so that different load demands are 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, the first input port of the compensator is configured to be connected to the source terminal CS, 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 of the compensator 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 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 carries out superposition compensation on the signal acquired 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 carries out PWM square wave modulation, the harmonic wave generation probability in the high-frequency switching power supply circuit is effectively reduced, and the stable system is further facilitated.
In another possible implementation manner, the switch unit further includes an overvoltage protection unit and a logic or gate, where a positive input end of the overvoltage protection unit is used as an overvoltage protection end OVP and is used for receiving the collected voltage value, a negative input end of the overvoltage protection unit is used for receiving the reference voltage, the overvoltage protection unit is used for outputting an output stop signal by an output end of the overvoltage protection unit when the collected voltage value is higher than the reference voltage, one input end of the logic or gate is used for connecting an output end of the overvoltage protection unit, another input end of the logic or gate is used for connecting with the PWM modulator, and an output end of the logic or gate is connected with the soft start circuit and is used for controlling 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 over-voltage protection end OVP is higher than the reference voltage, the over-voltage protection unit is utilized to control the soft start circuit to stop working, 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, where one end of the resistor R2 is connected to the input power module and is used for receiving a direct current 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 polar end of the third polar capacitor EC3, a negative polar end of the third polar capacitor EC3 is grounded, and the switch control module is connected to a positive polar 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 polar 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 scheme:
A switching power supply, comprising: the high-frequency switching power supply circuit.
In a third aspect, the present application provides a switching unit, which adopts the following technical scheme:
a switching unit comprising: the MOS transistor MOSFET-N, a soft start circuit, an oscillator OSC and a PWM modulator, wherein the DRAIN electrode of the MOS transistor MOSFET-N is used as the DRAIN electrode end DRAIN, the source electrode is used as the source electrode end CS, and the base electrode is connected with the soft start circuit; the oscillator OSC is used for generating a sawtooth wave signal, 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 is used for receiving the sawtooth wave signal, the negative input end is connected with the feedback end FB and is used for receiving a feedback voltage signal, the output end is connected with the soft start circuit and is used for generating a PWM square wave signal with a preset duty ratio according to the ramp signal and the feedback voltage value signal, and the PWM square wave signal is output to the soft start circuit; the soft start circuit is used for controlling the MOS transistor MOSFET-N to be conducted according to a PWM square wave signal with a preset duty ratio and a preset frequency corresponding to 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 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 on or off of the source electrode and the drain electrode of the MOS tube MOSFET-N according to the preset duty ratio, thereby realizing the adjustment of the power supply current supplied to the load according to different loads and further reducing the power consumption.
In one possible implementation, the soft start circuit includes a Driver, a logic output, and an SR flip-flop, the logic output including a first input, a second input, and an output;
wherein the S end of the SR trigger is connected with the oscillator OSC, the R end of the SR trigger is connected with the output end of the PWM modulator, the Q end of the SR trigger is connected with the first input end of the logic output device and is used for sending PWM square wave signals with 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 is connected with the Driver, the Driver is also connected with the base electrode of the MOS transistor MOSFET-N, and when the feedback voltage signal is larger than a first preset voltage threshold value, the logic output device 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 not greater than a first preset voltage threshold value and is greater than a second preset voltage threshold value, 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 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, driving the Driver to control the MOS transistor to be in an off state
In another possible implementation manner, the switching unit further includes a compensator, where the compensator includes a first input port, a second input port and an output port, the first input port of the compensator is configured to be connected to the source terminal CS, 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 of the compensator is connected to a 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 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.
In another possible implementation manner, the switch unit further includes an overvoltage protection unit and a logic or gate, where a positive input end of the overvoltage protection unit is used as an overvoltage protection end OVP and is used for receiving the collected voltage value, a negative input end of the overvoltage protection unit is used for receiving the reference voltage, the overvoltage protection unit is used for outputting an output stop signal by an output end of the overvoltage protection unit when the collected voltage value is higher than the reference voltage, one input end of the logic or gate is used for connecting an output end of the overvoltage protection unit, another input end of the logic or gate is used for connecting with the PWM modulator, and an output end of the logic or gate is connected with the soft start circuit and is used for controlling the soft start circuit to stop working when the overvoltage protection unit outputs the stop signal.
In summary, the present application includes the following beneficial technical effects:
1. the input power supply module is rectified into direct current signals to be output through the municipal power supply, the transformer is conducted according to preset frequency under the control of the switch control module, namely, the conduction preset time of the transformer is controlled in one period, when the transformer is conducted, the primary coil of the transformer continuously accumulates energy, when the transformer is turned off, the accumulated energy is transmitted to the secondary coil, the voltage stabilizing filter module connected with the secondary coil further converts alternating current signals into direct current power supply signals to supply power for a load, when the preset frequency is larger, the preset time for representing the conduction of the transformer is smaller, then the current for supplying power for the load is reduced, the magnitude 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 reduced; the preset frequency is determined by the switch control module according to feedback voltage signals fed back, the current load condition is determined according to different feedback voltage signals, and the corresponding preset frequency is selected according to the current load condition.
2. The feedback voltage signal represents the condition of the load, when the feedback voltage signal is larger than a first preset voltage threshold value, the load is represented as a heavy load at the moment, and the Driver is driven to control the MOSFET-N switch of the MOS tube at a first preset frequency, namely, when the load is a heavy load, the primary coil of the transformer is kept to be controlled to be turned on or off at a constant first preset frequency; when the load is a medium load, the Driver is controlled to turn on or off the primary coil of the transformer according to the preset duty ratio of the PWM square wave signal modulated by the PWM modulator; when the load is light load, the MOS transistor MOSFET-N is switched at a second preset frequency; when the load is empty, the disconnection state is kept continuously, different power supply modes are determined according to different loads, and further reduction of power consumption is facilitated, so that different load demands are met.
Drawings
Fig. 1 is a circuit diagram of a high frequency switching power supply circuit of an embodiment of the present application;
FIG. 2 is a schematic circuit diagram of a switching 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;
reference numerals illustrate: 1. an input power module; 11. a surge protection unit; 12. a rectifying unit; 13. a filtering unit; 2. a load; 3. a switching unit; 31. a soft start circuit; 311. a logic output; 312. an SR trigger; 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. and a buffer unit.
Detailed Description
The present application is described in further detail below in conjunction with figures 1-4.
The embodiment of the application discloses a high-frequency switching power supply circuit, referring to fig. 1, the high-frequency switching power supply circuit is connected with an input power supply module 1 and a load 2, and the input power supply module 1 is used for converting municipal power supply into a direct current signal and outputting the direct current signal to the high-frequency switching power supply circuit.
Specifically, referring to fig. 1, the input power module 1 includes a surge protection unit 11, a rectifying unit 12, and a filtering unit 13. The surge protection unit 11 is used for receiving municipal power, is also connected with the rectification unit 12, is used for outputting the municipal power to the rectification unit 12 when the municipal power is normal, and is also used for being disconnected when the municipal power is surge, so that the rectification unit 12 is disconnected from the municipal power. When the municipal power supply has surge current, the surge protection unit 11 can be used for switching the connection and disconnection between the municipal power supply and the rectifying unit 12, so that the surge current can be reduced from flowing into the high-frequency switching power supply circuit and the load 2, and adverse effects are generated on components of the high-frequency switching power supply circuit and the load 2.
Referring to fig. 1, an input power module 1 is provided with two ports for connecting with a municipal power supply, namely an L port and an N port, a 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, and the municipal power supply receiving 220V ac is rectified and then output; 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 is output into 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 of the rectifying unit 12, and a thermistor NTC having one end connected to the negative input 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 a normal state, and the current flows normally; when the system generates surge current, the fuse F is fused so as to reduce the damage of the surge current to each working element.
Specifically, the rectifying unit 12 may employ a full-bridge rectifying circuit, a half-bridge rectifying circuit, or the like, and may employ a packaged full-bridge rectifying module, such as a bridge rectifying module of the DB 207. The embodiment of the present application is not limited, and is preferably an encapsulated full-bridge rectifier module. The rectifying unit 12 is used for rectifying the municipal power supply into a pulsating direct current signal, but the rectified pulsating direct current signal is easy to have alternating current ripple, 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 polar capacitor EC1, a second polar capacitor EC2, a first resistor R1, a first inductor L1, and a second inductor L2, specifically, a positive output terminal is connected to a positive polarity terminal of the first polar capacitor EC1, a negative output terminal is connected to a negative polarity terminal of the first polar capacitor EC1, one end of the first inductor L1 is connected to the positive polarity terminal of the first polar capacitor EC1, the other end is connected to the positive polarity terminal of the second polar capacitor EC2, and a high-frequency switching power supply circuit for outputting a filtered dc signal, a negative polarity terminal of the second polar capacitor EC2 is grounded, both ends of the first resistor R1 are connected to the negative polarity terminal of the first polar capacitor EC1 and the negative polarity terminal of the second polar capacitor EC2, respectively, and the second inductor L2 is connected between the negative output terminal and ground. The direct current signal is filtered using 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 filter 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 is used for receiving a direct current electric signal, switching on or switching off the primary coil according to a 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 two ends of the secondary coil are respectively connected with two ends of the voltage stabilizing and filtering module 5 and are used for receiving a second alternating current signal and sending the second alternating current signal to the voltage stabilizing and filtering module 5, wherein 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 generate a dc power supply signal after voltage stabilizing and filtering the second ac power signal, and output the dc 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 for 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 reduced by the transformer 4, when the switch control module controls the primary coil to be turned off, the direct current signal received by the primary coil cannot circulate, namely cannot be reduced by the transformer 4, namely the voltage value of the reduced voltage of 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 an electric signal in a pulse form, the high level period of the pulse is the on period of the primary coil, the amplitude is equal to the amplitude of the direct current signal, the low level period of the electric signal in the pulse form is the 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 utilizing the voltage stabilizing filter module 5 connected with the secondary coil and is supplied to the load 2, so that the power supply of the load 2 is realized.
The high-frequency switch is utilized to convert the direct current electric signal into the first alternating current electric signal, then step down the first alternating current electric signal into the second alternating current electric signal, then perform voltage stabilizing filtering on the second alternating current electric signal to generate a direct current power supply signal to supply power to the load 2, and the transformer 4 is small in size and loss, so that the power consumption for supplying power to the load 2 is reduced, the power conversion efficiency is improved, meanwhile, the size of the transformer 4 is greatly reduced relative to that of a linear power supply, and the requirement of computer equipment is met.
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, where the switch unit 3 includes a DRAIN terminal DRAIN, a source terminal CS, and a power terminal VDD, an anode of the diode D2 is connected to a homonymous terminal of the auxiliary coil, 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 terminal VDD of the switch control module, one end of the resistor CSR1 is connected to the source terminal CS, the other end is grounded, the resistor CSR2 is connected in parallel with the resistor CSR1, and the DRAIN terminal DRAIN is connected to the homonymous terminal of the primary coil. The signal output by the auxiliary winding is alternating current, and after passing through the diode D2, the signal is changed into direct current and output to the VDD pin, so as to supply power to the switch unit 3, so that the DRAIN electrode terminal DRAIN of the switch unit 3 is conducted or disconnected with the source electrode terminal CS, for example, during the period that the signal output by the auxiliary winding is high level after passing through the diode D2, the DRAIN electrode terminal DRAIN of the switch unit 3 is conducted with the source electrode terminal CS, so that the homonymous terminal of the primary coil is connected with the ground to form a conducting path, and the primary coil accumulates energy at the moment; when the voltage is low, the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are in an off state, i.e. the same-name terminal of the primary coil does not form a conducting path, at this time, the primary coil of the transformer 4 releases energy and is transmitted to the secondary coil, and then the voltage stabilizing filter module 5 connected with the secondary coil obtains direct current, so as to realize power supply to the load 2.
The voltage stabilizing filter module 5 connected between the secondary coil and the load 2 is used for converting the second ac electric signal into a dc power supply signal to the load 2, specifically, referring to fig. 1, the voltage stabilizing filter 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 polar capacitor EC4, and a voltage stabilizing tube, wherein an anode of the diode D3 is connected to a homonymous terminal of the secondary coil, a cathode is used for being connected to the load 2, one end of the resistor R7 is connected to a cathode of the diode D3, the other end is connected to one end of the resistor R8, the other end of the resistor R8 is connected to a cathode of the voltage stabilizing tube, an anode of the voltage stabilizing tube 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 grounded, a positive end of the fourth polar capacitor EC4 is connected to a cathode of the diode D3, and a negative end of the fourth capacitor EC4 is grounded.
The first alternating current signal output by the primary coil is reduced in voltage by the transformer 4 and then a second alternating current signal is output by the secondary coil, and the reduction ratio is determined according to the number of turns of the primary coil and the number of turns of the secondary coil; and then, the unidirectional conductivity of the diode D3 and the charge maintaining function of the fourth polar capacitor EC4 are utilized to obtain direct current, namely a direct current power supply signal is obtained to the load 2 so as to supply power to the load 2.
Further, when the load 2 is light-load, heavy-load or no-load, the preset frequency of the switch control module can be changed to adjust the magnitude of the direct current power supply signal, that is, when a large current needs to be provided, the duration of the switch control module for controlling the primary coil to be conducted in one period is increased. Referring to fig. 1, the embodiment of the application further includes a feedback module 6, where the feedback module 6 is connected with the load 2 and further connected with the switch control module, and is configured to collect a dc power supply signal, generate a feedback voltage signal to the switch control module, so that the switch control module determines a 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 primary coil to be conducted according to the preset frequency corresponding to the current load 2. The magnitude of the current corresponding to the direct current power supply signal output to the load 2 can be adjusted by adjusting the magnitude of the preset frequency of the primary coil conduction. The feedback module 6 is used for collecting the voltage of the load 2, and transmitting 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 the load 2 is still provided with a large current or a large voltage 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 end FB, wherein an anode end of the optocoupler is connected to one end of the resistor R8 connected to the resistor R7, a cathode end of the optocoupler is connected to the other end of the resistor R8, a collector of the optocoupler is connected to the feedback end FB, an emitter of the optocoupler is grounded, and one end of the capacitor C2 is connected to the collector of the optocoupler while the other end is grounded. The optocoupler is used for generating a feedback voltage signal proportional 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 light load.
In addition, referring to fig. 1, a buffer unit 8 is connected across the same-name end and the non-same-name end of the primary coil, the buffer unit 8 includes a diode D1, a resistor R5, a resistor R4, and a capacitor C1, wherein an anode of the diode D1 is connected to the same-name end of the primary coil, a cathode is connected to one end of the resistor R5, the other end of the resistor R5 is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the non-same-name end of the primary coil, the capacitor C1 is connected to both ends of the resistor R4 in parallel, and the buffer unit 8 plays a role of buffering.
Further, in order to reduce the power consumption of the high-frequency switching power supply circuit during starting and standby, referring to fig. 1, the present application is provided with a high-voltage starting module 7, and 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 the direct current signal is received.
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 dc electrical signal; the other end of the resistor R2 is connected with one end of a third resistor R3, the other end of the third resistor R3 is connected with the positive end of a third polar capacitor EC3, the negative end of the third polar capacitor EC3 is grounded, and the negative end of the third polar capacitor EC3 is connected with a power supply end VDD of the switch control module.
When the high-frequency switching power supply is started, a direct-current electric 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 continuously charged until the voltage of the positive polar end of the third polar capacitor EC3 reaches the preset starting voltage of the switching unit 3, at the moment, the switching unit 3 starts to control the primary coil to be turned on or off according to the preset frequency, then in the process of normally powering on the load 2, the electric signal coupled by the auxiliary coil supplies power for the switching unit 3, namely, after the high-frequency switching power supply is started, the high-voltage starting module 7 supplies power for the switching unit 3, compared with a circuit without the high-voltage starting module 7, in the initial process of starting, the high-voltage starting module 7 needs to be continuously operated, the switching control module needs to be in a working state at the moment of starting, and the power consumption is high, so that the 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, where the switch unit 3 includes a DRAIN terminal DRAIN, a source terminal CS and a power supply terminal VDD, an anode of the diode D2 is connected with a homonymous terminal of an auxiliary coil, a cathode of the diode D2 is connected with one end of the resistor R6, the other end of the resistor R6 is connected with the power supply terminal VDD of the switch control module, 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 a DRAIN terminal DRAIN is connected with the homonymous terminal of the primary coil. The signal output by the auxiliary winding is alternating current, and after passing through the diode D2, the signal is changed into direct current and output to the VDD pin, so as to supply power to the switch unit 3, so that the DRAIN electrode terminal DRAIN of the switch unit 3 is conducted or disconnected with the source electrode terminal CS, for example, during the period that the signal output by the auxiliary winding is high level after passing through the diode D2, the DRAIN electrode terminal DRAIN of the switch unit 3 is conducted with the source electrode terminal CS, so that the homonymous terminal of the primary coil is connected with the ground to form a conducting path, and the primary coil accumulates energy at the moment; when the voltage is low, the DRAIN terminal DRAIN and the source terminal CS of the switch unit 3 are in an off state, i.e. the same-name terminal of the primary coil does not form a conducting path, at this time, the primary coil of the transformer 4 releases energy and is transmitted to the secondary coil, and then the voltage stabilizing filter module 5 connected with the secondary coil obtains direct current, so as to realize power supply to the load 2.
Further, the switching unit 3 is configured to control the primary coil to be turned on or off according to a preset frequency, and referring to fig. 2, in order to implement a function of switching according to the preset frequency, the switching unit 3 according to 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 electrode of the MOS transistor MOSFET-N is used as a DRAIN electrode terminal DRAIN, a source electrode is used as a source electrode terminal CS, and a base electrode is connected to the soft start circuit 31; the oscillator OSC is configured to generate a sawtooth signal, 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 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 the ramp signal and the 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 PWM square wave signal with a preset duty cycle and a preset frequency corresponding to the preset duty cycle.
When the load 2 changes, the corresponding feedback voltage signal will change according to the change of the load 2, and at the same time, the PWM modulator 32 will output a high level when the feedback voltage is higher than the sawtooth signal, and will output a low level when the feedback voltage is lower than the sawtooth signal, thereby generating a PWM square wave signal with a preset duty ratio. The soft start circuit 31 controls the on/off of the source and drain of the MOSFET-N according to a preset duty ratio, when the PWM square wave signal is at a high level, controls the on/off of the source and drain of the MOSFET-N, and when the PWM square wave signal is at a low level, controls the on/off of the source and drain of the MOSFET-N, and further adjusts the current value of the dc power supply signal generated by adjusting the on time of the source and drain of the MOSFET-N, thereby adjusting the power supply current of the load 2 according to different loads 2, and reducing the on duration of the MOSFET-N during light load, so as to reduce power consumption.
Still further, referring to FIG. 2, the soft start circuit 31 includes a Driver, a Logic output 311 (as shown in the figure, a protection Logic), and an SR flip-flop 312, the Logic output 311 including a first input, a second input, and an output; 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 311, for sending the PWM square wave signal with the preset duty ratio to the logic output 311; the second input end of the logic output device 311 is configured to receive a feedback voltage signal input by the feedback end FB, the output end is connected to a Driver, the Driver is further connected to the base of the MOS transistor MOSFET-N, and the logic output device 311 is configured to determine a preset frequency according to the feedback voltage signal, where the logic output device 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 the feedback voltage signal fed back by the 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, the load 2 carried by the current switching power supply is represented as 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 feedback voltage signal is greater than the first preset voltage threshold, the load 2 is driven in a constant current manner, so that the logic output device 311 can be more suitable for the requirement of the load 2, and when the feedback voltage signal is heavy load, the logic output device 311 outputs a mode signal representing the first preset frequency to the 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, the load 2 carried by the current power supply is characterized as being medium-load, light-load or idle, namely the feedback voltage signal is not larger than a first preset voltage threshold value; during medium load, light load or no load, the conduction time of the MOSFET-N of the MOS tube is reduced, the current flowing to the load 2 is reduced, and then the power loss is reduced.
In one possible implementation manner, when the logic output device 311 determines that the feedback voltage signal does not meet the preset condition, the Driver may be controlled to control the MOSFET-N switch of the MOS transistor with the preset switching frequency, where the conducting duration corresponding to the second preset frequency is lower than the conducting duration corresponding to the preset switching frequency, and further, compared with the heavy load case, the conducting duration is reduced, so as to reduce the current flowing to the load 2, thereby being beneficial to reducing the power loss.
However, when the MOS transistor MOSFET-N is directly driven to be turned on at the preset switching frequency, the carrying capacity of the medium load is weakened, and it is difficult to adapt to the situation of the carried load 2, and when the MOS transistor MOSFET-N still has current circulation during no load, the high frequency switch still generates unnecessary power loss, so in order to reduce the power loss during no load and enhance the 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 of 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 in real time according to the feedback voltage signal, when the load 2 is heavier, the voltage value corresponding to the feedback voltage signal is higher, the time that the square wave in the PWM square wave signal is at a high level is longer, so that the switching frequency of the current MOS transistor MOSFET-N is adjusted according to the condition of the load 2, the current value flowing into the load 2 is adjusted, and the load capacity can be adjusted according to the condition of the load 2 when the load 2 is light, so as to adapt to the requirement of the load 2, and the current flowing to the load 2 can be effectively reduced when the load is empty, thereby further reducing the power loss.
Still further, since current still flows during no-load, and power loss still exists, when the logic controller determines that the feedback voltage signal does not meet 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:
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 the second preset voltage threshold, if the feedback voltage signal is greater than the second preset voltage threshold, the current load 2 is represented as a medium load, at the moment, the PWM square wave signal based on the preset duty ratio drives the MOS transistor MOSFET-N to be conducted, so that the medium load has stronger load capacity, and the current output to the load 2 is automatically adjusted according to the load 2, so that the power consumption is further reduced.
When the feedback voltage signal is not greater than the second preset voltage threshold, the logic output device 311 characterizes that the feedback voltage signal is in a light load state or an idle state at the moment, and still needs to be supplied with power when the feedback voltage signal is not greater than the second preset voltage threshold but is greater than a third preset voltage threshold (wherein the third preset voltage threshold is greater than the second preset voltage threshold), and the logic output device 311 characterizes that the feedback voltage signal is in the light load state at the moment, and controls the driver to switch the MOS transistor MOSFET-N at the second preset frequency, wherein the switching period of the MOS transistor MOSFET-N corresponding to the second preset frequency is long, even lower than the frequency of a common power supply, the pulse wave is extremely narrow, the pulse wave interval is extremely long, the switching frequency of the MOS transistor MOSFET-N is low, the switching loss is small, and the loss of a power supply circuit is further reduced.
When the feedback voltage signal is not greater than the third preset voltage threshold, the load 2 is represented as an idle state, and in order to reduce power consumption during idle state, the logic output 311 will control the driver to stop working, i.e. make the driver control the MOS transistor MOSFET-N to be in a continuously disconnected state, and continue the step of judging whether the feedback voltage signal meets the preset condition or not until the feedback voltage signal is greater than the first preset voltage threshold, and control the driver to make the MOS transistor MOSFET-N conduct at the first preset frequency; or, judging that the feedback voltage signal is smaller than the first preset voltage threshold and larger than the 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 the third preset voltage threshold so as to enable the MOS transistor MOSFET-N to be switched on and off at the second preset frequency.
That is, when the feedback voltage signal is greater than a first preset voltage threshold, representing that the feedback voltage signal is in a heavy load state, switching the control MOS transistor MOSFET-N at a first preset frequency, when the feedback voltage signal is not greater than the first preset voltage threshold but greater than a second preset voltage threshold, representing that the feedback voltage signal is in a medium load state, driving the control MOS transistor MOSFET-N to switch on the basis of PWM square wave signals with 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, representing that the feedback voltage signal is in a light load state, and switching the control MOS transistor MOSFET-N at the second preset frequency; and when the feedback voltage signal is not greater than a third preset voltage threshold, maintaining the MOSFET-N of the control MOS tube unchanged, 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 greater than the second preset voltage threshold, or the feedback voltage signal is not greater than the second preset voltage threshold and greater than the third preset voltage threshold. The first preset voltage threshold is larger than the second preset voltage threshold, and the second preset voltage threshold is larger than the third preset voltage threshold. Therefore, the method can work under the heavy load and the fixed switching frequency, namely under the first preset frequency, and work under the frequency-reducing mode when in the medium load, namely under the mode of determining the switching frequency according to the feedback voltage signal; when the device is in light load or no load, the device works in a frequency hopping mode, and stops switching when the device is in no load, and when the device is in light load, the device is switched on and off at a second preset frequency, so that higher efficiency can be kept under the full load working condition, and the six-level energy efficiency requirement is met.
In one possible implementation manner of the present embodiment, referring to fig. 2, in order to reduce the harmonic wave in the PWM square wave signal, 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, the first input port of the compensator 33 is used for being connected with the source terminal CS, receiving the signal collected by the source terminal CS, the second input port of the compensator 33 is connected with the oscillator OSC, the output port is connected with the PWM modulator 32, and is used for compensating the 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 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, and superimposes the sawtooth wave signal on the basis of the signal collected by the source terminal CS to compensate, and the compensated signal is sent to the PWM modulator 32, so that the PWM modulator 32 modulates the PWM square wave, thereby effectively reducing the harmonic generation probability in the high-frequency switching power supply circuit, and further being beneficial to stabilizing 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, the sawtooth wave signal generated by the oscillator OSC is superimposed on the waveform of the source terminal CS to implement slope compensation, and then the value is input to the PWM modulation device. The compensation principle is schematically shown in fig. 3:
wherein, -m is the slope of the compensation harmonic, and is represented by I O Induced current error I 1 The method comprises the following steps:
Figure BDA0003802307070000151
if the current loop is stable, then:
Figure BDA0003802307070000152
again because:
D×m 1 ＝(1-D)m 2
so that:
Figure BDA0003802307070000153
d in FlyBack max Typically 70-80%, so m is typically 0.3 x m 2 。
In one possible implementation manner of this embodiment of the present application, 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 end of the overvoltage protection unit 34 is used as an overvoltage protection end OVP and is used for receiving a voltage value collected by the switch unit 3, a negative input end of the overvoltage protection unit 34 is used for receiving a reference voltage, the overvoltage protection unit 34 is used for outputting a stop signal and is output by an output end of the overvoltage protection unit 34 when the collected voltage value is higher than the reference voltage, one input end of the logic or gate 35 is used for connecting an output end of the overvoltage protection unit 34, another input end of the logic or gate 35 is used for being connected with the PWM modulator 32, and an output end of the logic or gate 35 is connected with the soft start circuit 31 and is used for controlling the soft start circuit 31 to stop working when the overvoltage protection unit 34 outputs a stop signal.
Specifically, when the voltage value received by the switch unit 3 is greater than the reference voltage, the voltage value collected by the current switch unit 3 is represented as overvoltage, at this time, the overvoltage protection unit 34 outputs a high-level stop signal to the logic or gate 35, and after the logic or gate 35 receives the high-level stop signal, no matter when 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, at this time, the soft start circuit 31 will control the MOS 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 logic or gate 35 connected to the output end of the over-voltage protection unit 34 is also connected to the output end of the over-current protection unit OCP, the positive input end of the over-current protection unit OCP is used for receiving the current value input by the source end CS, the negative input end is connected with a reference current value, when the current is higher than the reference current value, the over-current protection unit outputs a turn-off signal with a logic high level to the logic or gate 35, the logic or gate 35 outputs a stop signal with a high level, and the soft start circuit 31 stops working, i.e. the MOS transistor MOSFET-N keeps the turned-off state unchanged. Therefore, when the switch unit 3 detects that the current flowing into the switch unit 3 exceeds the reference current value and/or the voltage value exceeds the reference voltage value, the operation is stopped, so that the damage of overvoltage and/or overcurrent to the switch unit 3 is reduced, and the safety of the switch unit 3 is improved.
In one possible implementation manner of the embodiment of the present application, referring to fig. 2, the switch unit 3 further includes a blanking unit LEB, where the blanking unit LEB is connected between the over-current detecting unit and the source terminal CS, and the current detecting unit may be turned off in advance when the peak occurs at the source terminal CS due to the peak occurring at the front edge of the source terminal CS, so that the current detecting unit delays for a preset time and then performs current detection, and after delaying for the preset time, the peak at the front edge of the source terminal CS is already ended, so that false detection of current is reduced.
In a possible implementation manner, referring to fig. 2, the overvoltage protection terminal OVP of the switch unit 3 is connected with a resistor R10 and a resistor R11, where one end of the resistor R10 is connected with one end of the resistor R11 and then connected with the overvoltage protection terminal OVP, the other end of the resistor R10 is connected with the same name terminal of the auxiliary coil, the other end of the resistor R11 is connected with the non-same name terminal 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 acquired voltage of the auxiliary coil, and when the voltage is higher than the reference voltage value, the switch unit 3 is controlled to stop working.
In another possible implementation, 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) may also be indirectly detected by the voltage of the power supply terminal VDD, wherein the voltage of the VDD terminal is the voltage of the primary winding, the ratio of the voltage of the auxiliary winding to the voltage of the primary winding is equal to the ratio of the number of turns of the auxiliary winding to the number of turns of the primary winding, and then the voltage of the auxiliary winding may be indirectly detected by the voltage of the VDD terminal. Wherein, the relation between the voltage of the VDD terminal and the output voltage is approximately:
VDD＝(VOUT×NA)/NS
Wherein VDD is VDD voltage, VOUT is voltage received by the positive input terminal, NA is the number of turns of the auxiliary coil, and NS is the number of turns of the primary coil.
Further, referring to fig. 2, a voltage stabilizing diode is further connected to the gate of the MOS transistor MOSFET-N, and the cathode of the voltage stabilizing diode is connected to the gate of the MOS transistor MOSFET-N, and the anode is grounded, so as to stabilize 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 further connected between the power terminal VDD and the soft start circuit 31, for cutting off the connection with the soft start circuit 31 when the power terminal VDD is connected to a voltage higher than a preset voltage threshold, thereby improving the safety of the switch unit 3.
Referring to fig. 2, the switching unit 3 is further provided with a bandgap reference voltage source BandgapIbias and an under-voltage protection device UVLO, the input ends of the bandgap reference voltage source BandgapIbias and the under-voltage protection device UVLO are connected to the power supply terminal VDD, wherein the under-voltage protection device UVLO is used for protecting when the voltage of the power supply terminal VDD is lower than the voltage value of the bandgap 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 characteristics 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, where the temperature detection module is configured to detect a 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. Furthermore, the switching unit 3 in the embodiment of the present application further adopts a frequency dithering technology, which can effectively improve electromagnetic interference conduction and simplify the electromagnetic interference design of the system.
For the above embodiment, an example is provided to illustrate a process of controlling the MOSFET-N switch of the MOS transistor under different loads 2, referring to fig. 4, the chip is operated under a fixed switching frequency (for example, 85KHZ shown in fig. 4) in a heavy load mode, and is operated under a down-frequency mode (for example, 25 KHZ-85 KHZ shown in fig. 4) in a medium load mode, when the input voltage is fixed, the switching frequency will increase with the increase of the load 2, otherwise, when the load 2 is fixed, the switching frequency will increase with the increase of the input voltage, that is, when the voltage value corresponding to the feedback voltage signal received by the feedback terminal FB is gradually reduced, the switching frequency of the MOSFET-N is gradually reduced, and is operated under a light load mode, when the voltage value of the feedback voltage signal received by the feedback terminal FB is greater than the frequency hopping voltage, the MOS transistor MOSFET-N switch is controlled according to a second preset frequency, and when the voltage value of the feedback voltage signal is lower than the frequency hopping voltage, that is stopped, that is, when the input voltage is fixed, the load 2 is fixed, the switching frequency will increase with the input voltage, that is increased with the increase of the switching frequency, that is effective loss of the MOSFET-N, and the switching efficiency of the MOS transistor is still can be reduced, and the full-level can be realized, and the high-efficiency is required under the conditions.
The embodiment of the application also provides a switching power supply, and referring to fig. 1 and 2, the switching power supply comprises the high-frequency switching power supply circuit in the embodiment. The high-frequency switching power supply circuit of the switching power supply utilizes the switching control module to control the primary coil to be conducted or cut off according to the preset frequency, firstly, the rectified direct current is converted into a first alternating current signal under the action of the high-frequency switching, then the first alternating current signal is reduced into a second alternating current signal by utilizing the transformer 4, finally, the second alternating current signal is converted into a direct current power supply signal by utilizing the filtering voltage stabilizing module to supply power to the load 2, and the voltage conversion and voltage stabilization are realized by utilizing the high-frequency switching mode, wherein the loss of the transformer 4 is small, so that the power consumption is reduced, the power conversion efficiency is improved, and meanwhile, the volume of the transformer 4 is greatly reduced compared with that of a linear power supply.
The embodiment of the present application further provides a switching unit 3, specifically, referring to fig. 2, a switching unit 3, including: the MOS transistor MOSFET-N, the soft start circuit 31, the oscillator OSC and the PWM modulator 32, wherein the DRAIN electrode of the MOS transistor 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 signal, 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 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 the ramp signal and the 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 PWM square wave signal with a preset duty cycle and a preset frequency corresponding to the preset duty cycle.
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, when the load 2 changes, the corresponding feedback voltage signal will change 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 will change along with the change of the load 2, and the soft start circuit 31 controls the source and 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 to the load 2 according to different loads 2, and further reduce the 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 311, for sending the PWM square wave signal with the preset duty ratio to the logic output 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 is connected with the Driver, 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 to switch 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 the first preset voltage threshold value and is greater than the second preset voltage threshold value, the control driver controls 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 the second preset voltage threshold value and is greater than the third preset voltage threshold value, controlling the driver to control the MOSFET-N switch of the MOS tube according to the second preset frequency; when the feedback voltage signal is not greater than the third preset voltage threshold, the driving driver controls the MOS transistor MOSFET-N to be in an off state
Referring to fig. 2, 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, the first input port of the compensator 33 is configured to be connected with the source terminal CS, receive a signal collected by the source terminal CS, the second input port of the compensator 33 is connected with the oscillator OSC, and the output port is connected with the PWM modulator 32, 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 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 a feedback voltage signal.
In one possible implementation manner of this embodiment of the present application, 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 end of the overvoltage protection unit 34 is used as an overvoltage protection end OVP, and is used for receiving the collected voltage value, a negative input end of the overvoltage protection unit 34 is used for receiving the reference voltage, the overvoltage protection unit 34 is used for outputting an output stop signal from an output end of the overvoltage protection unit 34 when the collected voltage value is higher than the reference voltage, one input end of the logic or gate 35 is used for connecting an output end of the overvoltage protection unit 34, another input end of the logic or gate 35 is used for connecting with the PWM modulator 32, and an output end of the logic or gate 35 is connected with the soft start circuit 31, and is used for controlling the soft start circuit 31 to stop working when the overvoltage protection unit 34 outputs the stop signal.
The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.

Claims (6)

1. The utility model provides a high frequency switching power supply circuit, its characterized in that, power supply circuit is connected with input power supply module (1) and load (2), input power supply module (1) are used for converting municipal power supply into direct current electric signal output to power supply circuit, power supply circuit includes: the device comprises a switch control module, a transformer (4), a voltage stabilizing filter 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), and the other end of the primary coil is connected with the switch control module and is used for receiving the direct current signal, switching on or switching off 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, is also respectively connected with two ends of the voltage stabilizing and filtering module (5) and 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 also connected with the load (2) and is used for generating a direct current power supply signal after voltage stabilizing and filtering the second alternating current signal and outputting the direct current power supply signal to the load (2) to supply power to the load (2);
the feedback module (6) is connected with the load (2) and also connected with 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 as to enable the switch control module to determine the preset frequency according to the feedback voltage signal;
the switch control module comprises a switch unit (3), a resistor CSR1 and a resistor CSR2, wherein the switch unit (3) comprises a DRAIN terminal DRAIN, a source terminal CS, a feedback terminal FB, an overvoltage protection terminal OVP and a power supply terminal VDD, the power supply terminal VDD is used for being connected with a power supply to supply power to the switch unit (3), and the feedback module (6) is connected with the feedback terminal FB and used for feeding back a feedback voltage signal to the switch unit (3) through the feedback terminal FB so that the switch 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 of the resistor CSR2 is grounded, the resistor CSR1 is connected in parallel, and the DRAIN terminal DRAIN is connected with the homonymous terminal of the primary coil;
The switching unit (3) 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 the DRAIN electrode end DRAIN, the source electrode is used as the source electrode end CS, and the base electrode 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 is used for receiving the sawtooth wave signal, the negative input end is connected with the feedback end FB and is used for receiving a feedback voltage signal, the output end is connected with the soft start circuit (31) and is used for generating a PWM square wave signal with a preset duty ratio according to the sawtooth wave signal and the feedback voltage signal, and the PWM square wave signal is output to the soft start circuit (31); the soft start circuit (31) is used for controlling the MOS transistor MOSFET-N to be conducted according to a PWM square wave signal with a preset duty ratio and a preset frequency corresponding to the preset duty ratio;
the switch unit (3) further comprises an overvoltage protection unit (34) and a logic OR gate (35), wherein the positive input end of the overvoltage protection unit (34) is used as an overvoltage protection end OVP and used for receiving the collected voltage value, the negative input end of the overvoltage protection unit (34) is used for receiving the reference voltage, the overvoltage protection unit (34) is used for outputting an output stop signal from the output end of the overvoltage protection unit (34) when the collected voltage value is higher than the reference voltage, one input end of the logic OR gate (35) is used for connecting the output end of the overvoltage protection unit (34), the other input end of the logic OR gate (35) is used for connecting the output end of the PWM modulator (32), and the output end of the logic OR gate (35) is connected with the soft start circuit (31) and used for controlling the soft start circuit (31) to stop working when the overvoltage protection unit (34) outputs the stop signal;
The switch unit (3) further comprises an over-current protection unit (OCP), wherein one end of the logic OR gate (35) connected with the output end of the over-voltage protection unit (34) is also connected with the output end of the over-current protection unit (OCP), the positive input end of the over-current protection unit (OCP) is used for receiving a current value input by the source terminal CS, and the negative input end of the over-current protection unit is connected with a reference current value;
the soft start circuit (31) comprises a Driver, a logic output device (311) and an SR trigger (312), wherein the logic output device (311) comprises a first input end, a second input end and an output end;
the S end of the SR trigger (312) is connected with the oscillator OSC, the R end of the SR trigger (312) is connected with the output end of the logic OR gate (35), the Q end of the SR trigger (312) is connected with the first input end of the logic output device (311) and is used for sending PWM square wave signals with 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 the input end of the Driver, the output end of the Driver is connected with the base electrode of the MOS tube MOSFET-N, the logic output device (311) is used for determining a preset frequency according to the feedback voltage signal, and the logic output device (311) is used for driving the Driver to control the MOS tube MOSFET-N switch at a fixed first preset frequency when the feedback voltage signal is larger than a first preset voltage threshold value; when the feedback voltage signal is not greater than a first preset voltage threshold value and is greater than a second preset voltage threshold value, controlling the Driver to control the MOSFET-N switch of the MOS tube to work in a down-conversion mode 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 value and is greater than a third preset voltage threshold value, controlling the Driver to control the MOSFET-N switch of the MOS tube according to a fixed second preset frequency; and when the feedback voltage signal is not greater than a third preset voltage threshold, driving the Driver to control the MOS transistor MOSFET-N to be in an off state.
2. The high frequency switching power supply circuit according to claim 1, wherein the transformer (4) further comprises an auxiliary coil coupled to the secondary coil and further connected to the switching control module for powering the switching control module for operating the switching control module.
3. The high frequency switching power supply circuit according to claim 1, further comprising a high voltage start-up module (7), the high voltage start-up module (7) being connected to the input power supply module (1) for receiving the direct current 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 passes when the direct current signal is received.
4. The high frequency switching power supply circuit according to claim 1, 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 used for being connected with the source terminal CS, receiving a current collection signal collected by the source terminal CS, the second input port of the compensator (33) is connected with the oscillator OSC, the output port is connected with the PWM modulator (32), compensating a sawtooth wave signal generated by the oscillator OSC according to the current collection signal, and sending the compensated signal to the PWM modulator (32), so that the PWM modulator (32) determines a PWM square wave signal of a preset duty ratio corresponding to the current load (2) according to the compensated signal and a feedback voltage signal.
5. A high frequency switching power supply circuit according to claim 3, wherein the high voltage starting module (7) comprises 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 supply module (1) for receiving a direct current 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 the positive polar end of the third polar capacitor EC3, the negative polar end of the third polar capacitor EC3 is grounded, and the switching control module is connected to the positive polar end of the third polar capacitor EC 3.
6. A switching power supply comprising a high frequency switching power supply circuit as claimed in any one of claims 1 to 5.
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