CN111082677B - Switching power supply and control circuit and control method thereof - Google Patents

Switching power supply and control circuit and control method thereof Download PDF

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Publication number
CN111082677B
CN111082677B CN201911399251.0A CN201911399251A CN111082677B CN 111082677 B CN111082677 B CN 111082677B CN 201911399251 A CN201911399251 A CN 201911399251A CN 111082677 B CN111082677 B CN 111082677B
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signal
voltage
control
input current
current
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CN111082677A (en
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王建龙
熊毅
曹立丰
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Hangzhou Silan Microelectronics Co Ltd
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Hangzhou Silan Microelectronics 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
    • 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
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/06—Details with automatic reconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators

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

Abstract

The invention discloses a switching power supply and a control circuit and a control method thereof, wherein the control circuit comprises: an input current sampling unit which samples an input current to obtain a sampling voltage of the input current; a control unit for generating a first control signal; the first protection unit outputs a second control signal according to the sampling voltage of the input current, a first reference voltage and a first control signal; and the driving unit outputs a driving signal for controlling the power switch tube according to the second control signal, wherein when the sampling voltage of the input current is greater than or equal to the first reference voltage, the driving unit turns off the power switch tube according to the second control signal, and in the next control period, the driving unit turns on the power switch tube according to the second control signal. The power switch tube of the main circuit can be quickly conducted, and the output voltage is prevented from being too low.

Description

Switching power supply and control circuit and control method thereof
Technical Field
The invention relates to the technical field of switching power supply control, in particular to a switching power supply and a control circuit and a control method thereof.
Background
A switching power supply is a power supply that maintains an output voltage stable by controlling a time ratio of on and off of a power switching tube using modern power electronic technology, and generally includes a Pulse Width Modulation (PWM) control circuit and a power switching tube (e.g., an IGBT (Insulated Gate Bipolar Transistor)). The conventional switching power supply is implemented in an analog control mode, a digital control mode and a digital-analog hybrid control mode. In recent years, digital control methods have become widely used and accepted because of their advantages such as programmability, design continuity, and a small number of components.
Due to the existence of nonlinear elements and energy storage elements in a large number of electric devices, the waveform of the alternating current input current is seriously distorted, and the input power factor of the power grid side is low. Therefore, a PFC (Power Factor Correction) control system must be added to the electric equipment. In a PFC control system, the on and off of a power switch tube are controlled through a PWM control signal to realize the control of a system power factor and an output voltage, meanwhile, the input current needs to be detected and protected in real time, and if the detected input current is higher than a set protection threshold value, the PWM control signal is closed in time to prevent the failure of the power switch tube and a rear-end device caused by overhigh input current.
The traditional PFC overcurrent protection can be divided into software protection and hardware protection, wherein the software protection comprises the steps of sending sampling voltage representing input current into a digital-analog sampling port of a microcontroller, then carrying out software filtering on a sampling result, and if the value after filtering is higher than a set protection threshold value, closing the output of a PWM control signal. In the hardware protection, a sampling voltage obtained according to the input current is compared with a reference voltage (namely, an overcurrent protection threshold) set by hardware through a hardware comparator, when the sampling voltage is higher than the reference voltage, the comparator is turned over, and the microcontroller closes the output of a PWM control signal.
The traditional PFC overcurrent protection easily causes the false triggering of the overcurrent protection when transient current impact or interference occurs, so that unnecessary shutdown protection is caused. In addition, the overcurrent protection of the PFC software requires filtering processing on signals, so that the protection speed is slow, and the output of the PWM control signal can be closed only when the input current is higher than a protection threshold value. In PFC hardware overcurrent protection, since the protection threshold cannot be adjusted, the set protection threshold is usually higher than the highest target current of the PFC control system. If the target current is greatly different from the protection threshold, the input current may overshoot greatly, and especially in the case of frequent overcurrent, the service life of the power switch tube, the filter capacitor and the load at the rear end are easily affected.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a switching power supply, a control circuit and a control method thereof, which solve the problem of large overshoot amplitude of input current in the circuit when the input voltage jumps due to voltage drop, etc., and the present invention can ensure that the input current is always kept below a set current-limiting protection threshold, thereby avoiding unnecessary frequent shutdown, and can recover the conduction of a power switch tube at the fastest speed after the current overshoot is recovered, thereby maintaining the stability of the output voltage and ensuring the stable operation of the rear-end load.
According to a first aspect of embodiments of the present invention, there is provided a control circuit of a switching power supply, the control circuit including: an input current sampling unit which samples an input current to obtain a sampling voltage of the input current; a control unit for generating a first control signal; the first protection unit is connected with the control unit and outputs a second control signal according to the sampling voltage of the input current, a first reference voltage and the first control signal; and the driving unit is connected with the first protection unit and outputs a driving signal for controlling a power switch tube according to the second control signal, wherein when the sampling voltage of the input current is greater than or equal to the first reference voltage, the driving unit turns off the power switch tube according to the second control signal, and in the next control period, the driving unit turns on the power switch tube according to the second control signal.
Preferably, the first protection unit includes: the comparison module compares the first reference voltage with the sampling voltage of the input current and generates a first indication signal according to a comparison result; the fault management module is connected with the comparison module and generates the second control signal according to the first indication signal, the first control signal and the PWM reset signal; when the sampling voltage of the input current is larger than or equal to the first reference voltage, judging that the input current is over-current, outputting the second control signal by the fault management module to turn off the power switch tube, and outputting the second control signal by the fault management module according to the PWM reset signal to turn on the power switch tube in the next control period.
Preferably, the fault management module comprises: a first latch generating a first fail signal according to the PWM reset signal and the first indication signal; and the AND gate generates the second control signal according to the first control signal and the first fault signal, wherein the first fault signal is valid when the first indication signal is valid, the first fault signal is invalid when the PWM reset signal is valid and the first indication signal is invalid, the state of the second control signal is consistent with the state of the first control signal when the first fault signal is invalid, and the second control signal is invalid when the first fault signal is valid.
Preferably, the control circuit further comprises: an input voltage sampling unit which samples an input voltage of the switching power supply to obtain a sampling voltage of the input voltage; and the control unit generates the first control signal according to the sampling voltage of the input current, the target voltage, the sampling voltage of the input voltage and the sampling voltage of the output voltage.
Preferably, the control unit includes: a duty signal generation unit that generates a duty signal from the sampling voltage of the input current, the sampling voltage of the input voltage, the sampling voltage of the output voltage, and the target voltage; and a PWM generating unit generating the first control signal and a PWM reset signal according to the duty signal, wherein the duty signal generating unit includes: the first adding module is used for obtaining a first error according to the sampling voltage of the output voltage and the target voltage; the first linear control module is used for obtaining an input current effective value according to the first error; the phase calculation module is used for obtaining an input voltage phase value according to the sampling voltage of the input voltage; the multiplication module is used for obtaining a target current signal according to the input current effective value and the input voltage phase value; the second addition module is used for obtaining a second error according to the sampling voltage of the input current and the target current signal; and a second linear control module generating the duty cycle signal according to the second error.
Preferably, the first linear control module and the second linear control module each include a PI controller.
Preferably, the first protection unit is further configured to control the driving unit to turn off the power switch tube when the number of times that the sampled voltage of the input current is greater than or equal to the first reference voltage within a first preset time reaches a preset value and a fault clearing signal is not received.
Preferably, the first protection unit further includes: the second indication signal generation unit is used for counting the first indication signal, obtaining a count value, generating a second indication signal according to the count value, and enabling the second indication signal to be effective when the count value is greater than or equal to a preset value within a first preset time, wherein the second indication signal generation unit comprises: the counting module is used for counting the first indicating signal to obtain a counting value, generating an intermediate indicating signal according to the counting value, and enabling the intermediate indicating signal to be effective when the counting value is larger than or equal to a preset value within first preset time; the latch module is connected with the counting module and used for latching the intermediate indication signal and generating a second indication signal according to the intermediate indication signal; the first timer is used for repeatedly timing, generating a counting reset signal after the first preset time, resetting the counting value according to the counting reset signal by the counting module and restarting counting; and the second timer starts timing when the intermediate indication signal is effective and generates a fault clearing signal after a second preset time, and the latch module generates a second indication signal according to the fault clearing signal and the intermediate indication signal.
Preferably, the fault management module further comprises: and a second latch configured to generate a second fail signal based on the PWM reset signal and the second indication signal, wherein the second fail signal is enabled when the second indication signal is enabled, the second fail signal is disabled when the PWM reset signal is enabled and the second indication signal is disabled, a state of the second control signal is identical to a state of the first control signal when both the first fail signal and the second fail signal are disabled, and the second control signal is disabled when one of the first fail signal and the second fail signal is enabled.
Preferably, the control circuit further comprises: a threshold adjustment unit that adjusts the target current signal to obtain the first reference voltage, wherein the threshold adjustment unit includes: the software adjusting module receives the target current signal and obtains a current-limiting protection threshold according to the target current signal; and the digital-to-analog conversion module is used for receiving the current-limiting protection threshold value and carrying out digital-to-analog conversion on the current-limiting protection threshold value to generate the first reference voltage.
Preferably, the software adjusting module obtains the current-limiting protection threshold according to a maximum value of the target current signal, an amplitude of a current ripple, and a preset protection margin.
Preferably, the control circuit further includes a load state detection unit that detects a load state of the switching power supply to obtain the target voltage, the target voltage varying according to a variation in the load state.
Preferably, the control circuit further includes a hardware protection unit, which receives a sampling voltage of the input current, the hardware protection unit generates a first trigger signal when the sampling voltage of the input current is greater than or equal to a second reference voltage, the driving unit turns off the power switching tube according to the first trigger signal, and the control unit controls the first control signal to be in an invalid state according to the first trigger signal, where the second reference voltage represents a first overcurrent protection threshold, and the second reference voltage is greater than the first reference voltage.
Preferably, the control circuit further includes a software protection unit, which receives a sampling voltage of the input current, the software protection unit generates a second trigger signal when the sampling voltage of the input current is greater than or equal to a third reference voltage, and the control unit controls the first control signal to be in an invalid state according to the first trigger signal, where the third reference voltage represents a second overcurrent protection threshold, and the first reference voltage is greater than the third reference voltage.
According to a second aspect of the embodiments of the present invention, there is provided a switching power supply including the control circuit described above.
Preferably, the switching power supply further includes: a rectifier bridge rectifying an alternating input voltage to obtain the input voltage; the inductor, the diode and the sampling resistor are connected to two ends of the rectifier bridge in series, and the anode of the diode is connected with the power switch tube and the middle node of the inductor; and the output capacitor is connected between the intermediate node and the cathode of the diode and used for stabilizing the output voltage.
According to a third aspect of the embodiments of the present invention, there is provided a control method of a switching power supply, the control method including: sampling the input current to obtain a sampled voltage of the input current; generating a first control signal; generating a second control signal according to the sampling voltage of the input current, a first reference voltage and the first control signal; and generating a driving signal for controlling a power switch tube according to the second control signal, wherein when the sampling voltage of the input current is greater than or equal to the first reference voltage, the power switch tube is turned off according to the second control signal, and in the next control period, the power switch tube is turned on according to the second control signal.
Preferably, the control method further includes: and generating the first control signal according to the sampling voltage of the input current, the target voltage, the sampling voltage of the input voltage and the sampling voltage of the output voltage.
Preferably, the control method further includes: and obtaining a target current signal according to the target voltage, the sampling voltage of the input voltage and the sampling voltage of the output voltage, and obtaining the first reference voltage according to the target current signal.
Preferably, the control method further includes: the target voltage is obtained by detecting a load state of the switching power supply.
Preferably, the step of generating a second control signal according to the sampled voltage of the input current, a first reference voltage and the first control signal comprises: comparing the first reference voltage with the sampling voltage of the input current, and generating a first indication signal according to the comparison result; generating the second control signal according to the first indication signal and the first control signal.
Preferably, the step of generating the second control signal according to the first indication signal and the first control signal comprises: generating a first fault signal according to the PWM reset signal and the first indication signal; and generating the second control signal according to the first control signal and the first fault signal, wherein the first fault signal is valid when the first indication signal is valid, the first fault signal is invalid when the PWM reset signal is valid and the first indication signal is invalid, the state of the second control signal is consistent with the state of the first control signal when the first fault signal is invalid, and the second control signal is invalid when the first fault signal is valid.
Preferably, the control method further includes: and when the times that the sampling voltage of the input current is greater than or equal to the first reference voltage within the first preset time reaches a preset value and a fault clearing signal is not received, the power switch tube is turned off.
Preferably, the step of generating a second control signal according to the sampled voltage of the input current, a first reference voltage and the first control signal further comprises: counting the first indicating signal to obtain a counting value, generating an intermediate indicating signal according to the counting value, and enabling the intermediate indicating signal to be effective when the counting value is larger than or equal to a preset value within first preset time; latching the intermediate indication signal and generating a second indication signal according to the intermediate indication signal; generating a counting reset signal after the first preset time, resetting the counting value according to the counting reset signal, and restarting counting; starting timing when the intermediate indication signal is effective, generating a fault clearing signal after a second preset time, and generating a second indication signal according to the fault clearing signal and the intermediate indication signal; generating the second control signal according to the first indication signal, the second indication signal and the first control signal.
Preferably, the step of generating the second control signal according to the first indication signal, the second indication signal and the first control signal comprises: the PWM reset signal and the second indication signal generate a second fail signal, wherein the second fail signal is active when the second indication signal is active, the second fail signal is inactive when the PWM reset signal is active and the second indication signal is inactive, a state of the second control signal is identical to a state of the first control signal when both the first fail signal and the second fail signal are inactive, and the second control signal is inactive when one of the first fail signal and the second fail signal is active.
Preferably, the step of obtaining the first reference voltage according to the target current signal includes: obtaining the current-limiting protection threshold according to the maximum value of the target current signal, the amplitude of the current ripple and a preset protection margin; performing digital-to-analog conversion on the current-limiting protection threshold to generate the first reference voltage.
Preferably, the step of generating the first control signal according to the sampled voltage of the input current, the target voltage, the sampled voltage of the input voltage, and the sampled voltage of the output voltage includes: obtaining a first error according to the sampling voltage of the output voltage and the target voltage; obtaining an input current effective value according to the first error; obtaining an input voltage phase value according to the sampling voltage of the input voltage; obtaining a target current signal according to the input current effective value and the input voltage phase value; obtaining a second error according to the sampling voltage of the input current and the target current signal; generating a duty cycle signal according to the second error; and generating the first control signal and a PWM reset signal according to the duty ratio signal.
Preferably, the control method further includes: and generating a first trigger signal when the sampling voltage of the input current is greater than or equal to a second reference voltage, turning off the power switch tube according to the first trigger signal, and controlling the first control signal to be in an invalid state, wherein the second reference voltage represents a first overcurrent protection threshold value, and the second reference voltage is greater than the first reference voltage.
Preferably, the control method further includes: and generating a second trigger signal when the sampling voltage of the input current is greater than or equal to a third reference voltage, and controlling the first control signal to be in an invalid state according to the first trigger signal, wherein the third reference voltage represents a second overcurrent protection threshold value, and the first reference voltage is greater than the third reference voltage.
The switching power supply, the control circuit and the control method thereof have the following beneficial effects.
The switching power supply provides two-stage hardware overcurrent protection, when input current is overshot due to external interference, the input current can be ensured to be always below a set current-limiting protection threshold value, the current overshoot amplitude is reduced, frequent overcurrent impact on a filter capacitor, a load and the like at the rear end is avoided to the greatest extent, the stability of a system is improved, and the service life of devices is prolonged. Even though accidental false triggering occurs, the system can turn off the power switch tube in time through the current-limiting protection of the cycle-by-cycle mode, so that the current amplitude is reduced, the power switch tube of the main circuit is quickly turned on in the next PWM control cycle, the normal work of the switching power supply system is prevented from being influenced by too low output voltage, the shutdown protection is not needed, the system can be prevented from being frequently shut down due to overcurrent protection under the condition of frequent and severe fluctuation of a power grid, and the user experience of related products is improved.
In a further embodiment, the switching power supply enters the single-time protection mode when the input current exceeds the current-limiting protection threshold value for a plurality of times within a certain time, and the switching power supply can be restarted only when a fault clearing signal is received. Even under the condition that the power grid fluctuates frequently, the input current can be ensured to be always close to the set current-limiting protection threshold value for small-amplitude fluctuation, devices such as a filter capacitor and a load at the rear end are prevented from being subjected to overcurrent impact to the greatest extent, and the stability of the system and the service life of the devices are improved.
In a further embodiment, the current-limiting protection threshold value can be modified in real time according to the load state, so that the input current of the main circuit can be always controlled within a certain range when the switching power supply works under different load conditions, the input current is prevented from generating large fluctuation, and devices such as a rear-end filter capacitor and a load are protected.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 shows a schematic configuration diagram of a switching power supply according to a first embodiment of the present invention;
FIG. 2 shows a schematic diagram of the control unit of FIG. 1;
FIG. 3 is a schematic structural diagram of the first protection unit of FIG. 1;
FIG. 4 is a schematic diagram showing a structure of a second indication signal generation unit in FIG. 3;
FIG. 5 shows a schematic diagram of the structure of the fault management module of FIG. 3;
fig. 6A and 6B show waveform diagrams of overcurrent protection according to the prior art and the first embodiment of the present invention, respectively;
fig. 7 shows a schematic configuration diagram of a switching power supply according to a second embodiment of the present invention;
FIG. 8 is a schematic diagram showing the structure of the control unit of FIG. 7;
fig. 9 is a schematic diagram showing a structure of the duty signal generating unit in fig. 8;
FIG. 10 is a schematic diagram showing the structure of the threshold adjusting unit in FIG. 7;
fig. 11 illustrates a schematic structural view of the first protection unit in fig. 7;
fig. 12 illustrates a schematic configuration diagram of the second indication signal generation unit in fig. 11;
FIG. 13 shows a schematic diagram of the structure of the fault management module of FIG. 11;
fig. 14 shows an operation timing chart of the switching power supply according to the embodiment of the invention;
fig. 15 shows a waveform diagram of overcurrent protection of a switching power supply according to the prior art and a second embodiment of the invention;
fig. 16 shows a method flowchart of a control method of a switching power supply according to a third embodiment of the present invention;
fig. 17 is a detailed flowchart illustrating a control method according to a third embodiment of the present invention;
fig. 18 is a flowchart showing a cycle-by-cycle protection mode of the control method according to the third embodiment of the invention;
fig. 19 shows a flow chart of a single protection mode of the control method according to the third embodiment of the present invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.
In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of components, are set forth in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.
It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one element or sub-circuit through an electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.
Fig. 1 shows a schematic configuration diagram of a switching power supply according to a first embodiment of the present invention. The switching power supply adopts a Boost topology and works in a floating mode. As shown in fig. 1, the switching power supply includes a rectifier bridge 110, a main circuit 120, an output capacitor Cout, a load 130, and a control circuit 200. Wherein the input terminal of the main circuit 120 is connected to the output terminal of the rectifier bridge 110, and the output terminal is connected to the load 130. The main circuit 120 includes an inductor Lf, a power switch tube T1, a fast recovery diode VD, and a sampling resistor Rsen.
Further, the input end of the rectifier bridge 110 is connected to the AC power source AC, the rectifier bridge 110 is configured to convert an AC input signal into an input voltage Vin, the inductor Lf, the power switch tube T1 and the sampling resistor Rsen are connected in series between the positive output end and the negative output end of the rectifier bridge 110, and obtain an input current Iin according to the input voltage Vin, the fast recovery diode VD is configured to perform isolation, so as to prevent the output capacitor Cout from being short-circuited to ground when the power switch tube T1 is turned on, and the output capacitor Cout is connected in parallel to the load 130, and is configured to stabilize the output voltage Vout. The control terminal of the power switch T1 is connected to the control circuit 200, and the control circuit 200 is used for controlling the power switch T1 to be turned on and off, so that the main circuit 120 obtains the output voltage Vout according to the input voltage Vin. During the on period of the power switch tube T1, the alternating current power supply AC charges the inductor Lf, and during the off period of the power switch tube T1, the inductor Lf supplies power to the load. The control circuit 200 is further configured to detect the input current Iin in real time and perform overcurrent protection on the circuit, and if the detected input current Iin is higher than a set overcurrent protection threshold, turn off the power switch transistor T1 in the main circuit 120 in time to prevent the power switch transistor T and the backend device from failing due to the excessively high input current Iin.
Further, the power switch Transistor T1 in the present embodiment is implemented by, for example, an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The IGBT is a composite voltage-driven power semiconductor device composed of BJT (Bipolar Junction Transistor) and MOSFET, and has the advantages of both high input impedance of MOSFET and low on-state voltage drop of GTR (Transistor), and has low driving power and reduced saturation voltage.
Specifically, the control circuit 200 includes: a control unit 210, a first protection unit 240, and a driving unit 260. The control unit 210 is configured to generate a first control signal PWM1 according to the target voltage. The first protection unit 240 obtains a second control signal PWM2 according to the sampled voltage Iin _ sa of the input current, the first reference voltage Vref representing the current limiting protection threshold, and the first control signal PWM 1. The driving unit 260 provides a driving voltage Vgate to the control terminal of the power switch T1 according to the second control signal PWM2 to drive the power switch T1 in the main circuit 120, so that the main circuit 120 obtains an output voltage Vout according to the input voltage Vin.
Specifically, the first protection unit 240 compares the sampled voltage Iin _ sa of the input current with the first reference voltage Vref, and determines the state of the second control signal PWM2 according to the comparison result. In each PWM control period, when the comparison result indicates that the sampled voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the first protection unit 240 generates an invalid second control signal PWM2, and the driving unit 260 turns off the power switch T1 in the main circuit 120 according to the second control signal PWM 2.
In this embodiment, the first control signal PWM1 is a square wave signal with a certain duty ratio, and the first control signal PWM1 is active at a high level and inactive at a low level; the second control signal PWM2 is active high and inactive low.
Further, the switching power supply further includes an input current sampling unit 251 and an output voltage sampling unit 253, the input current sampling unit 251 obtains a sampling voltage Iin _ sa of the input current by detecting the input current Iin of the main circuit 120, and the output voltage sampling unit 253 samples the output voltage Vout of the switching power supply to obtain a sampling voltage Vout _ sa of the output voltage.
Further, the switching power supply further includes a second protection unit 270, configured to compare the sampled voltage Iin _ sa of the input current with an internal second reference voltage that represents a first overcurrent protection threshold, when the sampled voltage Iin _ sa of the input current is greater than or equal to the internal second reference voltage, the second protection unit 270 generates an effective first trigger signal, the driving unit 260 turns off the power switch T1 in the main circuit 120 according to the effective first trigger signal, and meanwhile, the control unit 210 outputs an ineffective first control signal PWM1 according to the effective first trigger signal. Illustratively, the second protection unit 270 is a hardware overcurrent protection unit, and a standard comparator is used to compare the sampled voltage Iin _ sa of the input current with a fixed internal second reference voltage.
Further, the control circuit 200 further includes a third protection unit 280, the third protection unit 280 compares the sampled voltage Iin _ sa of the input current with an internal third reference voltage representing a second overcurrent protection threshold, when the sampled voltage Iin _ sa of the input current is greater than or equal to the internal third reference voltage, the third protection unit 280 generates an effective second trigger signal according to the comparison result, and the control unit 210 outputs an ineffective first control signal PWM1 according to the effective second trigger signal. In an example, the third protection unit 280 is a software overcurrent protection unit, the AD converter is used to convert the sampled voltage Iin _ sa of the input current into a digital quantity, and a second trigger signal is generated through software filtering and comparison operation.
In this embodiment, the second over-current protection threshold in this embodiment is greater than the current-limiting protection threshold, and the current-limiting protection threshold is greater than the first over-current protection threshold, and the corresponding internal second reference voltage is greater than the first reference voltage, and the first reference voltage is greater than the internal third reference voltage.
Fig. 2 shows a schematic configuration of the control unit in fig. 1. As shown in fig. 2, the control unit 210 includes a duty signal generation unit 211 and a PWM generation unit 212. The duty ratio signal generating unit 211 is configured to calculate a required duty ratio signal according to a target voltage set by software, and conventionally, the duty ratio signal is calculated by using negative feedback control of an output voltage and an input current, and specifically, the duty ratio signal can be realized by PI control. The PWM generating unit 212 is configured to generate the first control signal PWM1 according to the duty ratio signal and the first trigger signal and the second trigger signal. The PWM generating unit 212 outputs the first control signal PWM1 that is active when all of the first and second trigger signals are inactive, and outputs the first control signal PWM1 that is inactive when one of the first and second trigger signals is active. In addition, the PWM generation unit 212 also outputs a PWM reset signal to the first protection unit 240 at the beginning of each PWM control period.
In this embodiment, the first trigger signal and the second trigger signal are active at a high level and inactive at a low level.
Fig. 3 illustrates a schematic structural view of the first protection unit in fig. 1. As shown in fig. 3, the first protection unit 240 includes a comparison module 241, a second indication signal generation unit 242, and a fault management module 243. The comparison module 241 compares the first reference voltage Vref with the sampled voltage Iin _ sa of the input current, and when the sampled voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the comparison module 241 generates an effective first indication signal. The second indication signal generating unit 242 is configured to generate a valid second indication signal when a count value of the first indication signal is greater than or equal to a preset value within a first preset time. The fault management module 243 generates the active or inactive second control signal PWM2 based on the first indication signal, the second indication signal, and the first control signal PWM 1. The power switch tube current limiting protection circuit can ensure that when the input current is increased due to abnormal disturbance, the input current is not higher than the set current limiting protection threshold all the time, and can quickly recover the normal work of the power switch tube, thereby avoiding the situation that the output voltage is too low due to long-time turn-off of the power switch tube.
The fault management module 243 is responsible for output management of the second control signal PWM2, and if the fault management module 243 receives the valid first indication signal and the valid second indication signal, the invalid second control signal PWM2 is output, and at this time, the second control signal PWM2 is maintained in a low level state; if the fault management module 243 does not receive valid first and second indication signals, the second control signal PWM2 is output in accordance with the state of the first control signal PWM 1.
Fig. 4 illustrates a schematic configuration diagram of the second indication signal generation unit in fig. 3. As shown in fig. 4, the second indication signal generating unit 242 includes a counting module 2421, a first timer 2422, a latch module 2423, and a second timer 2424. The counting module 2421 is used for counting the valid first indication signals. When the count value of the first indication signal which is effective in the first preset time is greater than or equal to the preset value, the counting module 2421 generates an effective intermediate indication signal; otherwise, an invalid intermediate indication signal is generated. The latch module 2423 is used for latching the valid intermediate indication signal and generating a valid second indication signal according to the valid intermediate indication signal. The first timer 2422 is configured to repeatedly time and generate an active count reset signal when the first preset time is reached, and the counting module 2421 resets the count value of the first indication signal according to the active count reset signal and restarts counting. The second timer 2424 starts timing when receiving a valid intermediate indication signal and generates a valid fault clearing signal after a second preset time elapses, the latch module 2423 generates an invalid second indication signal according to the valid fault clearing signal, and the second timer 2424 stops working and starts working when receiving the next valid intermediate indication signal.
In this embodiment, the first indicator signal, the intermediate indicator signal, and the second indicator signal are active low and inactive high, and the count reset signal and the fault clear signal are active high and inactive low.
Fig. 5 shows a schematic diagram of the structure of the fault management module in fig. 3. In the present embodiment, the fault management module 243 has two modes, cycle-by-cycle protection and single-time protection. Specifically, as shown in fig. 5, the fault management module 243 includes a first latch 2431, a second latch 2432, and an and gate 2433. The first latch 2431 includes a first set terminal for receiving the first indication signal, a first reset terminal for receiving the PWM reset signal, and a first output terminal. The second latch 2432 includes a second set terminal for receiving the second indication signal, a second reset terminal for receiving the PWM reset signal, and a second output terminal. The and gate 2433 includes first to third input terminals for receiving the first control signal PWM1, a second input terminal connected to the first output terminal of the first latch 2431, a third input terminal connected to the second output terminal of the second latch 2432, and a third output terminal connected to the input terminal of the driving unit 260. The and gate 2433 is used to generate the second control signal PWM2 according to the output signals of the first and second latches 2431 and 2432 and the first control signal PWM 1.
For example, the first latch 2431 generates an active first fault signal when receiving an active first indication signal and sets the cycle-by-cycle protection mode flag bit, and the and gate 2433 generates an inactive second control signal PWM2 based on the active first fault signal. The first latch 2431 generates an inactive first fail signal upon receiving an active PWM reset signal and an inactive first indication signal, and simultaneously resets the cycle-by-cycle protection mode flag bit, and the gate 2433 generates the second control signal PWM2 in accordance with the state of the PWM1 (assuming that the second fail signal output from the second latch 2432 is in an inactive state at this time), and the second control signal PWM2 and the first control signal PWM1 at this time are identical. In the cycle-by-cycle protection, when the input current exceeds the current-limiting protection threshold, software intervention is not required in each PWM control cycle, the power switch tube T1 in the main circuit can be turned off or turned on only by the cycle-by-cycle protection inside the fault management module 243, so as to prevent the input current from flowing through the power switch tube T1 and subsequent devices from being damaged, and the power switch tube T1 in the main circuit can be turned on quickly, so as to prevent the output voltage from being too low.
For another example, the second latch 2432 generates an active second fault signal when receiving an active second indication signal, sets the one-time protection mode flag bit, and the and gate 2433 generates an inactive second control signal PWM2 according to the active second fault signal, and the second control signal PWM2 is always at a low level. The second latch 2432 is further configured to generate an inactive second fault signal when receiving the active PWM reset signal and the inactive second indication signal, and the and gate 2433 generates the second control signal PWM2 in accordance with the state of the first control signal PWM1 according to the inactive second fault signal (assuming that the first fault signal output by the first latch 2431 is in an inactive state at this time). In the single protection mode, the flag bit of the single protection mode needs to be cleared by software to recover the output of the control signal, namely, compared with the cycle-by-cycle protection, once the single protection is effective, the flag bit of the single protection mode can be reset only when an effective fault clearing signal is detected, and the switching power supply recovers the normal working state.
Fig. 6A and 6B show waveform diagrams of overcurrent protection according to the prior art and the first embodiment of the present invention, respectively.
As shown in fig. 6A, in the conventional hardware overcurrent protection technology, current overshoot occurs when voltage fluctuates to trigger hardware overcurrent protection, and since it cannot be determined whether overcurrent protection is caused by an excessive duty ratio of a duty ratio signal or overcurrent protection is caused by other unknown reasons in the current system, the current system can only be selected to be shut down for a period of time and then restarted, otherwise unpredictable risks such as device damage may be caused. If the power grid fluctuates frequently, the system can be shut down frequently in an overcurrent mode.
As shown in fig. 6B, the switching power supply according to the first embodiment of the present invention sets a current-limiting protection threshold lower than the normal hardware overcurrent protection threshold, and if the duty ratio of the duty ratio signal is too large due to voltage fluctuation, the current-limiting protection in the cycle-by-cycle mode is triggered, the system can turn off the power switch tube in time, the current will decrease, and the power switch tube can be automatically turned on again in the next PWM control cycle without shutdown protection. However, if the current rises very fast due to short circuit or the like, the current will directly exceed the current limiting protection threshold, and the current limiting protection and the hardware overcurrent protection are triggered at the same time, so that the system is shut down.
Therefore, as can be seen from fig. 6A and 6B, the current overshoot amplitude caused by the power grid fluctuation of the switching power supply according to the first embodiment of the present invention is significantly smaller than that of the conventional overcurrent protection technology, and the reliability of the back-end power device can be improved.
Fig. 7 shows a schematic configuration diagram of a switching power supply according to a second embodiment of the present invention. Like the first embodiment, the switching power supply of this embodiment also adopts a Boost topology and operates in a floating mode. As shown in fig. 7, the switching power supply includes a rectifier bridge 110, a main circuit 120, an output capacitor Cout, a load 130, and a control circuit 300. Wherein the input terminal of the main circuit 120 is connected to the output terminal of the rectifier bridge 110, and the output terminal is connected to the load 130. The main circuit 120 includes an inductor Lf, a power switch tube T1, a fast recovery diode VD, and a sampling resistor Rsen.
The control circuit 300 is not only used for controlling the on and off of the power switch tube T1, but also used for detecting the input current of the main circuit 120 in real time and performing input current overcurrent protection on the circuit, and if the detected input current is higher than a set current limiting protection threshold, the power switch tube T1 in the main circuit 120 is turned off in time to prevent the input current from being too high to cause the failure of the power switch tube T1 and the backend device.
Specifically, the control circuit 300 includes: a control unit 310, a threshold adjusting unit 320, a first protection unit 340, and a driving unit 360. The control unit 310 is configured to generate the first control signal PWM1 according to the sampled voltage Vin _ sa of the input voltage, the sampled voltage Vout _ sa of the output voltage, the sampled voltage Iin _ sa of the input current, and the target voltage of the main circuit 120, and obtain the target current signal according to the load state of the load 130. The threshold adjusting unit 320 obtains a first reference voltage Vref used for representing a current limiting protection threshold according to the target current signal. The first protection unit 340 obtains the second control signal PWM2 according to the sampled voltage Iin _ sa of the input current, the first reference voltage Vref, and the first control signal PWM 1. The driving unit 360 provides a driving voltage Vgate to the control terminal of the power switch T1 according to the second control signal PWM2 to drive the power switch T1 in the main circuit 120, so that the main circuit 120 obtains an output voltage Vout according to the input voltage Vin.
Specifically, the first protection unit 340 compares the sampled voltage Iin _ sa of the input current with the first reference voltage Vref, and generates the valid or invalid second control signal PWM2 according to the comparison result. In each PWM control period, when the comparison result indicates that the sampled voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the first protection unit 340 generates an invalid second control signal PWM2, and the driving unit 360 turns off the power switch T1 in the main circuit 120 according to the invalid second control signal PWM 2.
In this embodiment, the first control signal PWM1 is a square wave signal with a certain duty ratio, and the first control signal PWM1 is active at a high level and inactive at a low level; the second control signal PWM2 is active high and inactive low.
Further, the switching power supply further includes an input current sampling unit 351, an input voltage sampling unit 352, an output voltage sampling unit 353, and a load state detection unit 354. The input current sampling unit 351, the input voltage sampling unit 352 and the output voltage sampling unit 353 respectively detect the input current Iin, the input voltage Vin and the output voltage Vout of the main circuit 120 to obtain a sampling voltage Iin _ sa of the input current, a sampling voltage Vin _ sa of the input voltage and a sampling voltage Vout _ sa of the output voltage. The load state detection unit 354 is used to detect a load state (for example, obtain load state information by detecting a load current, a load power, and the like) to obtain a target voltage. As a non-limiting example, the load state detection unit 354 is, for example, a PI controller, whose inputs are a characteristic target load state reference value and a characteristic actual load state detection value, respectively, and whose output is a target voltage. The load state detection unit 354 obtains the target voltage signal according to feedback adjustment of the actual load state. The control unit 310 obtains the first control signal PWM1 and the target current signal by calculating according to the sampled voltage Iin _ sa of the input current, the sampled voltage Vin _ sa of the input voltage, the sampled voltage Vout _ sa of the output voltage, and the target voltage.
Further, the switching power supply further includes a second protection unit 370, configured to compare the sampled voltage Iin _ sa of the input current with a second reference voltage representing the first overcurrent protection threshold, and when the sampled voltage Iin _ sa of the input current is greater than or equal to the second reference voltage, the second protection unit 370 generates an effective first trigger signal, the driving unit 360 turns off the power switch T1 in the main circuit 120 according to the effective first trigger signal, and meanwhile, the control unit 310 outputs an ineffective first control signal PWM1 according to the effective first trigger signal. For example, the second protection unit 370 is a hardware overcurrent protection unit, and a standard comparator is used to compare the sampled voltage Iin _ sa of the input current with a fixed second reference voltage.
Further, the control circuit 300 further includes a third protection unit 380, the third protection unit 380 compares the sampled voltage Iin _ sa of the input current with a third reference voltage representing a second overcurrent protection threshold, when the sampled voltage Iin _ sa of the input current is greater than or equal to the third reference voltage, the third protection unit 380 generates an active second trigger signal, and the control unit 310 outputs the inactive first control signal PWM1 according to the active second trigger signal. In an example, the third protection unit 380 is a software overcurrent protection unit, the AD converter is used to convert the sampling voltage Iin _ sa of the input current into a digital quantity, and a second trigger signal is generated through software filtering and comparison operation.
Similarly, the first overcurrent protection threshold in this embodiment is greater than the current limit protection threshold, and the current limit protection threshold is greater than the second overcurrent protection threshold. The corresponding second reference voltage is greater than the first reference voltage, and the first reference voltage is greater than the third reference voltage.
Fig. 8 shows a schematic diagram of the structure of the control unit in fig. 7. As shown in fig. 8, the control unit 310 includes a duty signal generation unit 311 and a PWM generation unit 312. The duty signal generating unit 311 is configured to generate a duty signal according to the received sampling voltage Iin _ sa of the input current, the sampling voltage Vin _ sa of the input voltage, the sampling voltage Vout _ sa of the output voltage, and the target voltage. The PWM generating unit 312 is configured to generate the first control signal PWM1 according to the duty ratio signal and the first trigger signal and the second trigger signal. The PWM generating unit 312 outputs the first control signal PWM1 that is active when all of the first and second trigger signals are inactive, and outputs the first control signal PWM1 that is inactive when one of the first and second trigger signals is active. In addition, the PWM generation unit 312 also outputs a PWM reset signal to the first protection unit 340 at the beginning of each PWM control period.
In this embodiment, the first trigger signal and the second trigger signal are active at a high level and inactive at a low level.
Fig. 9 shows a schematic structural diagram of the duty signal generating unit in fig. 8. As a non-limiting example, as shown in fig. 9, the duty ratio signal generating unit 311 includes an addition module 3111, a linear control module 3112, a multiplication module 3113, a phase calculation module 3114, an addition module 3115, and a linear control module 3116. The adding module 3111 is configured to calculate a first error according to a sampled voltage Vout _ sa of the output voltage and a target voltage, the linear control module 3112 obtains an effective value of the input current according to the first error, the phase calculation module 3114 obtains a phase value of the sampled voltage Vin _ sa of the input voltage according to the sampled voltage Vin _ sa of the input voltage, the multiplication module 3113 obtains a target current signal according to the effective value of the input current and the phase value of the sampled voltage Vin _ sa of the input voltage, the adding module 3115 calculates a second error between the sampled voltage Iin _ sa of the input current and the target current signal, and the linear control module 3116 generates a duty signal according to the second error. The linear control module 3112 and the linear control module 3116 are, for example, PI controllers (Proportional Integral controllers), and the first error and the second error are close to 0 in a steady state by setting a Proportional coefficient, an Integral coefficient, a maximum-minimum limiter, and the like in the linear control module 3112 and the linear control module 3116. The operating principle of the PI controller is common knowledge of those skilled in the art, and is not described herein again.
Fig. 10 shows a schematic structural diagram of the threshold adjusting unit in fig. 7. As shown in fig. 10, the threshold adjusting unit 320 includes a software adjusting module 321 and a digital-to-analog converting module 322.
The software adjusting module 321 receives the target current signal, and obtains a current-limiting protection threshold through software calculation according to the target current signal. Specifically, the software adjusting module 321 adds a preset protection margin on the basis of the summation of the maximum value of the target current signal and the current ripple amplitude, and finally obtains the current-limiting protection threshold.
The digital-to-analog conversion module 322 receives the current-limiting protection threshold, and performs digital-to-analog conversion on the current-limiting protection threshold to generate a first reference voltage Vref, thereby implementing flexible adjustment on the current-limiting protection threshold.
Fig. 11 is a schematic structural view of the first protection unit in fig. 7. As shown in fig. 11, the first protection unit 340 includes a comparison module 341, a second indication signal generation unit 342, and a fault management module 343. The comparison module 341 compares the first reference voltage Vref with the sampled voltage Iin _ sa of the input current, and when the sampled voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the comparison module 341 generates an effective first indication signal. The second indication signal generating unit 342 is configured to generate an effective second indication signal when a count value of the first indication signal is greater than or equal to a preset value within a first preset time. The fault management module 343 generates an active or inactive second control signal PWM2 based on the first indication signal, the second indication signal, and the first control signal PWM 1. The power switch tube current limiting protection circuit can ensure that when the input current is increased due to abnormal disturbance, the input current is not higher than the set current limiting protection threshold all the time, and can quickly recover the normal work of the power switch tube, thereby avoiding the situation that the output voltage is too low due to long-time turn-off of the power switch tube.
The fault management module 343 is responsible for managing the output of the second control signal PWM2, and if the fault management module 343 receives the valid first indication signal and the valid second indication signal, the fault management module outputs the invalid second control signal PWM2, and at this time, the second control signal PWM2 is maintained in a low level state; if the fault management module 343 does not receive valid first and second indication signals, the second control signal PWM2 is output in accordance with the state of the first control signal PWM 1.
Fig. 12 illustrates a schematic configuration diagram of the second indication signal generation unit in fig. 11. As shown in fig. 12, the second indication signal generation unit 342 includes a counting module 3421, a first timer 3422, a latch module 3423, and a second timer 3424. The counting module 3421 is used for counting the valid first indication signals. When the count value of the first indication signal valid within the first preset time is greater than or equal to the preset value, the counting module 3421 generates a valid intermediate indication signal; otherwise, an invalid intermediate indication signal is generated. The latch module 3423 is used for latching the valid intermediate indication signal and generating a valid second indication signal according to the valid intermediate indication signal. The first timer 3422 is configured to repeatedly count time and generate an effective count reset signal when a first preset time is reached, and the counting module 3421 resets the count value of the first indication signal according to the effective count reset signal and restarts counting. The second timer 3424 starts timing when receiving a valid intermediate indication signal and generates a valid fault clearing signal after a second preset time, the latch module 3423 generates an invalid second indication signal according to the valid fault clearing signal, and the second timer 3424 stops working and starts working when receiving the next valid intermediate indication signal.
In this embodiment, the first indicator signal, the intermediate indicator signal, and the second indicator signal are active low and inactive high, and the count reset signal and the fault clear signal are active high and inactive low.
Fig. 13 shows a schematic diagram of the structure of the fault management module in fig. 11. In this embodiment, the fault management module 343 has two modes, cycle-by-cycle protection and single-time protection. Specifically, as shown in fig. 13, the fault management module 343 includes a first latch 3431, a second latch 3432, and an and gate 3433. The first latch 3431 includes a first set terminal for receiving the first indication signal, a first reset terminal for receiving the PWM reset signal, and a first output terminal. The second latch 3432 includes a second set terminal for receiving the second indication signal, a second reset terminal for receiving the PWM reset signal, and a second output terminal. The and gate 3433 includes first to third input terminals for receiving the first control signal PWM1, a second input terminal connected to the first output terminal of the first latch 3431, a third input terminal connected to the second output terminal of the second latch 3432, and a third output terminal connected to the input terminal of the driving unit 360. The and gate 3433 is used to generate the second control signal PWM2 according to the output signals of the first and second latches 3431 and 3432 and the first control signal PWM 1.
For example, the first latch 3431 generates an active first fail signal when receiving an active first indication signal, and sets the cycle-by-cycle protection mode flag bit, and the and gate 3433 generates an inactive second control signal PWM2 according to the active first fail signal. The first latch 3431 generates an invalid first fail signal upon receiving the valid PWM reset signal and the invalid first indication signal, and simultaneously resets the cycle-by-cycle protection mode flag bit, and the gate 3433 generates the second control signal PWM2 in accordance with the state of the PWM1 (assuming that the second fail signal output from the second latch 3432 is in an invalid state at this time), and the second control signal PWM2 and the first control signal PWM1 at this time are identical. In the cycle-by-cycle protection, when the input current exceeds the current-limiting protection threshold, software intervention is not required in each PWM control cycle, the power switch tube T1 in the main circuit can be turned off or turned on only by the cycle-by-cycle protection inside the fault management module 343, so as to prevent the input current from flowing through the power switch tube T1 and subsequent devices from being damaged, and the power switch tube T1 in the main circuit can be turned on quickly, so as to prevent the output voltage from being too low.
For another example, the second latch 3432 generates an active second fail signal when receiving an active second indication signal, sets the one-time protection mode flag bit, and the and gate 3433 generates an inactive second control signal PWM2 according to the active second fail signal, and the second control signal PWM2 is always at a low level. The second latch 3432 is further configured to generate an inactive second fail signal when receiving the active PWM reset signal and the inactive second indication signal, and the and gate 3433 generates the second control signal PWM2 in accordance with the inactive second fail signal and in accordance with the state of the first control signal PWM1 (assuming that the first fail signal output by the first latch 3431 is in an inactive state at this time). In the single protection mode, the flag bit of the single protection mode needs to be cleared by software to recover the output of the control signal, namely, compared with the cycle-by-cycle protection, once the single protection is effective, the flag bit of the single protection mode can be reset only when an effective fault clearing signal is detected, and the switching power supply recovers the normal working state.
Fig. 14 is a timing diagram illustrating the operation of the switching power supply according to the embodiment of the present invention. In the timing diagram of fig. 14, the switching power supply operates in a plurality of successive PWM control periods, and each PWM control period is the period from one active PWM reset signal to the next active PWM reset signal. For example, the first PWM control cycle is a time period between times t0-t 2. In fig. 14, the first control signal PWM1 and the second control signal PWM2 are both active high and inactive low. The fault clearing signal and the PWM reset signal are active at a high level and inactive at a low level. The first indication signal and the second indication signal are both active at low level and inactive at high level.
As described above, the control circuit of the switching power supply of the embodiment of the present invention includes the cycle-by-cycle protection mode and the single-shot protection mode. In the cycle-by-cycle protection mode, when the sampled voltage Iin _ sa of the input current exceeds the first reference voltage Vref, the power switch tube T1 in the main circuit 120 can be turned off or turned on only by the fault management module without software intervention in each PWM control cycle, so as to prevent the input current from overshooting and damaging the power switch tube and subsequent devices, and the power switch tube T1 of the main circuit 120 can also be turned on quickly, so as to prevent the output voltage from being too low. In the single protection mode, when the times that the input current exceeds the current-limiting protection threshold value in a plurality of PWM control periods reach a preset value, the single protection mode is started, and compared with the period-by-period protection mode, once the single protection mode takes effect, the flag bit of the single protection mode can be reset only when an effective fault clearing signal is detected, and the switching power supply recovers the normal working state.
At time t0, the PWM reset signal is active, and the first and second indication signals are inactive, the fault management module generates an active second control signal, and the sampled voltage Iin _ sa of the input current is gradually increased.
At time T1, the sampling voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the output of the comparison module is inverted, the first indication signal is inverted to an active state, the fault management module generates an invalid second control signal, the power switch tube T1 in the main circuit 120 is turned off, and the sampling voltage Iin _ sa of the input current is gradually reduced.
At time t2, the PWM reset signal is again inverted to an active state, and at this time, the first and second indication signals are in an inactive state, so the fault management module generates the second control signal PWM2 in which the active second control signal and the first control signal PWM1 are in a consistent state, and the sampling voltage Iin _ sa of the input current gradually increases. The working processes of the time t0-t1 and the time t1-t2 are repeated at the later time t2-t3, time t4-t5, time t3-t4 and time t5-t6 respectively, and are not described again.
At time T6, the PWM reset signal is inverted to the active state again, when the number of times that the first indication signal is active reaches a preset value, the second indication signal is inverted from the inactive state to the active state, the fault management module generates an inactive second control signal, the power switch T1 in the main circuit 120 is turned off, and the sampling voltage Iin _ sa of the input current is gradually reduced.
At time T7, the PWM reset signal is again toggled to the active state, and the second indication signal is still active, so the fault management module generates an inactive second control signal and the power switch T1 in the main circuit 120 is still in the off state.
At time t8, the fault clear signal is inverted to the active state, and the latch module in the second indication signal generation unit inverts the second indication signal from the active state to the inactive state according to the active fault clear signal.
At time t9, the PWM reset signal is again inverted to an active state, at which time the first and second indication signals are in an inactive state, so the fault management module generates an active second control signal and the sampled voltage Iin _ sa of the input current is gradually increased.
At time T10, the sampling voltage Iin _ sa of the input current is greater than or equal to the first reference voltage Vref, the output of the comparison module is inverted, the first indication signal is inverted to an active state, the fault management module generates an invalid second control signal, the power switch tube T1 in the main circuit 120 is turned off, and the sampling voltage Iin _ sa of the input current is gradually reduced.
Fig. 15 shows a waveform diagram of overcurrent protection of a switching power supply according to the prior art and a second embodiment of the present invention. In fig. 15, the broken line indicates the overcurrent protection threshold and the waveform of the input current of the switching power supply of the related art, and the solid line indicates the current-limiting protection threshold and the waveform of the input current of the switching power supply of the second embodiment of the present invention. As shown in fig. 15, the prior art switching power supply can only set a highest fixed threshold, and if the input current is relatively small when overcurrent occurs, a large overshoot of the input current occurs. The current-limiting protection threshold value of the switching power supply of the embodiment of the invention is changed along with the change of the target current signal obtained according to the load state, so that the input current of the main circuit can be always controlled within a certain range when the switching power supply works under different load conditions, and the larger fluctuation of the input current is prevented.
Fig. 16 shows a method flowchart of a control method of a switching power supply according to a third embodiment of the present invention. The switching power supply of this embodiment may be the switching power supply of the above embodiment, and includes a rectifier bridge 110, a main circuit 120, an output capacitor Cout, a load 130, and a control circuit. The input terminal of the main circuit 120 is connected to the rectifier bridge 110, and the output terminal is connected to the load 130. The main circuit 120 includes an inductor Lf, a power switch tube T1, a fast recovery diode VD, and a sampling resistor Rsen. The control circuit is not only used for controlling the on and off of the power switch tube T1, but also used for detecting the input current of the main circuit 120 in real time and performing input current overcurrent protection on the circuit, and if the detected input current is higher than a set current limiting protection threshold, the power switch tube T1 in the main circuit 120 is turned off in time to prevent the input current from being too high to cause the failure of the power switch tube T1 and rear-end devices. As shown in fig. 16, the control method includes the following steps S110 to S140.
In step S110, sampling the input current to obtain a sampling voltage of the input current;
in step S120, a first control signal is generated.
In a further embodiment, the control method further comprises generating the first control signal and the target current signal from the target voltage, a sampled voltage of the input voltage and a sampled voltage of the input current, and a sampled voltage of the output voltage. Furthermore, the target voltage under different load conditions can be obtained according to load condition signals such as load current, load power and the like.
In step S130, a second control signal is obtained according to the sampled voltage of the input current, the first reference voltage, and the first control signal.
In step S140, a driving signal for controlling the power switch tube is generated according to the second control signal.
The control method comprises the steps of generating an invalid second control signal when the sampling voltage of the input current is greater than or equal to the first reference voltage in each PWM control period, and turning off the power switch tube according to the invalid second control signal, and generating a second control signal PWM2 which is consistent with the state of the first control signal PWM1 at the beginning of the next PWM control period adjacent to the PWM control period, and controlling the switching action of the power switch tube according to the second control signal PWM 2.
Further, the control method further comprises the steps of generating an invalid second control signal when the number of times that the sampling voltage of the input current is greater than or equal to the first reference voltage within the first preset time reaches a preset value, and turning off a power switch tube in the main circuit according to the invalid second control signal.
Further, the control method further includes obtaining the first reference voltage for characterizing the current-limiting protection threshold according to the target current signal. For example, the current-limiting protection threshold may be obtained according to a maximum value of the target current signal, an amplitude of a current ripple, and a preset protection margin, and the first reference voltage may be obtained by performing digital-to-analog conversion according to the current-limiting protection threshold.
Fig. 17 is a detailed flowchart illustrating a control method according to a third embodiment of the present invention. Specifically, the control method of the present embodiment further includes steps S210 to S260.
In step S210, it is determined whether the sampled voltage of the input current is equal to or greater than a first reference voltage. If the sampling voltage of the input current is greater than or equal to the first reference voltage, continuing to step S220; if the sampled voltage of the input current is smaller than the first reference voltage, the step S230 is continued.
In step S220, an effective first indication signal is output, the counting module counts the effective first indication signal, and the count value of the counting module is incremented by 1. In this embodiment, when the sampling voltage of the input current is greater than or equal to the first reference voltage, the comparison module generates an effective first indication signal. And the fault management module generates an invalid second control signal according to the valid first indication signal and sets a cycle-by-cycle protection mode flag bit. And the counting module counts the pulses of the first indicating signal to obtain a count value.
In step S230, it is determined whether a first preset time is reached. If the first preset time is reached, continuing to step S240; if the first preset time is not reached, the control flow is exited, and the process is restarted, and the determination logic of step S210 is continuously executed.
In step S240, it is determined whether the count value of the first indication signal is greater than or equal to a preset value. If the count value of the first indication signal is greater than or equal to the preset value, continuing to step S250; if the count value of the first indication signal is smaller than the preset value, the step S260 is continued.
In step S250, a valid second indication signal is generated. In this embodiment, the counting module counts the first indication signal within a first preset time, and when a count value of the first indication signal within the first preset time is greater than or equal to a preset value, the counting module generates a valid second indication signal. And the fault management module generates an invalid second control signal according to the valid second indication signal, and sets the flag bit of the single-time protection mode, so that the switching power supply enters the single-time protection mode.
In step S260, the count value of the first instruction signal is cleared. In this embodiment, after each first preset time, the count value of the first indication signal is cleared and the count is restarted, and then the control flow exits and is restarted, and the determination logic of step S210 is continuously executed.
Fig. 18 and 19 show flow diagrams of the cycle-by-cycle protection mode and the single-shot protection mode, respectively, of the control method according to the third embodiment of the present invention.
As shown in fig. 18, the cycle-by-cycle protection mode of the control method includes steps S310 to S380.
In step S310, a first control signal is received.
In step S320, it is determined whether a valid PWM reset signal is received. If a valid PWM reset signal is received, continue to step S330; if the valid PWM reset signal is not received, step S340 is continued.
In step S330, the first fault signal is cleared.
In step S340, it is determined whether a valid first indication signal is received. If the valid first indication signal is received, continuing to step S350; if the valid first indication signal is not received, the step S360 is continued.
In step S350, a valid first fault signal is generated. In this embodiment, the fault management module further includes a first latch that generates a first fault signal and sets the cycle-by-cycle protected mode flag bit when receiving a valid first indication signal.
In step S360, it is determined whether a valid first fault signal is received. If a valid first fault signal is received, continue to step S370; if a valid first failure signal is not received, step S380 is continued.
In step S370, an invalid second control signal is output. In this embodiment, the fault management module further includes an and gate, and the and gate generates an invalid second control signal when receiving the valid first fault signal.
In step S380, the second control signal is output in accordance with the state of the first control signal.
In the embodiment, the first latch clears the first fault signal when receiving the valid PWM reset signal and simultaneously receiving the invalid first indication signal, and the and gate outputs the second control signal in accordance with the state of the first control signal.
In the cycle-by-cycle protection mode, when the input current exceeds the current-limiting protection threshold, software intervention is not needed in each PWM control cycle, the power switch tube in the main circuit can be turned off only through the cycle-by-cycle protection in the fault management module, the power switch tube and subsequent devices are prevented from being damaged by input current overshoot, the power switch tube in the main circuit can be rapidly turned on in the next PWM control cycle, and the output voltage is prevented from being too low.
As shown in fig. 19, the single protection mode of the control method includes steps S410 to S480.
In step S410, a first control signal is received.
In step S420, it is determined whether a valid PWM reset signal is received. If a valid PWM reset signal is received, continue to step S430; if the valid PWM reset signal is not received, the process continues to step S440.
In step S430, the second fault signal is cleared.
In step S440, it is determined whether a valid second indication signal is received. If a valid second indication signal is received, continuing to step S450; if a valid second indication signal is not received, the process continues to step S460.
In step S450, a valid second fault signal is generated. In this embodiment, the fault management module further includes a second latch, and the second latch generates a second fault signal and sets the single protection mode flag bit when receiving a valid second indication signal.
In step S460, it is determined whether a valid second failure signal is received. If a valid second failure signal is received, continue to step S470; if a valid second failure signal is not received, step S480 continues.
In step S470, the invalid second control signal is output. In this embodiment, the fault management module further includes an and gate, and the and gate generates an invalid second control signal when receiving the valid second fault signal.
In step S480, the second control signal is output in accordance with the state of the first control signal. In this embodiment, the second latch clears the second fault signal when receiving the valid PWM reset signal and simultaneously receiving the invalid second indication signal, and the and gate outputs the second control signal in accordance with the state of the first control signal.
In the single-shot protection mode, the switching power supply enters the single-shot protection mode when the input current exceeds the current-limiting protection threshold value for a plurality of times within a certain time (including a plurality of PWM control periods), and the switching power supply is required to be restarted until a fault clearing signal is received. Even if the power grid fluctuates frequently to cause the input current to flow over frequently, the input current can be ensured to be always in the vicinity of the set over-current protection threshold value to fluctuate in a small range, devices such as a filter capacitor and a load at the rear end are prevented from being subjected to over-current impact to the greatest extent, and the stability of the system and the service life of the devices are improved.
In summary, the switching power supply of the invention ensures that the overcurrent protection is not triggered when the system is in normal operation, and when the input current or the load has slight jump to cause the input current to exceed the current-limiting protection threshold, the power switching tube can be turned off in time, so as to prevent the input current from generating large overshoot to damage the power switching tube and subsequent devices. And even if accidental false triggering occurs, the power switch tube of the main circuit can be quickly opened in the next PWM control period, so that the situation that the output voltage is too low and the normal operation of a power supply system is not influenced is prevented.
In a further embodiment, when the input current exceeds the current-limiting protection threshold value for multiple times within a certain time, the switching power supply enters a single-time protection mode, and the switching power supply can be restarted only by clearing the flag bit of the protection mode through software, that is, only when a fault clearing signal is received, the power switching tube is turned on again. Even if the power grid fluctuates frequently, the input current can be guaranteed to be always close to the set current-limiting protection threshold value to fluctuate in a small range, devices such as a filter capacitor and a load at the rear end are prevented from being subjected to overcurrent impact to the greatest extent, and the stability of the system and the service life of the devices are improved.
In a further embodiment, the current-limiting protection threshold value can be modified in real time according to the load state, so that the input current of the main circuit can be always controlled within a certain range when the switching power supply works under different load conditions, the input current is prevented from generating large fluctuation, and devices such as a rear-end filter capacitor and a load are protected. Increase the reliability and prolong the service life
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims (27)

1. A control circuit for a switching power supply, the control circuit comprising:
an input current sampling unit which samples an input current to obtain a sampling voltage of the input current;
a control unit for generating a first control signal;
the first protection unit is connected with the control unit and outputs a second control signal according to the sampling voltage of the input current, a first reference voltage and the first control signal; and
the driving unit is connected with the first protection unit and outputs a driving signal for controlling the power switch tube according to the second control signal,
wherein the first protection unit is used for comparing the sampling voltage of the input current with the first reference voltage in each PWM control period, generating a first indication signal according to the comparison result, and triggering cycle-by-cycle protection when the first indication signal is effective so as to turn off the power switch tube in the current PWM control period and turn on the power switch tube according to a PWM reset signal when the next PWM control period starts,
the first protection unit includes a second indication signal generation unit including:
the counting module is used for counting the first indicating signal to obtain a counting value, generating an intermediate indicating signal according to the counting value, and enabling the intermediate indicating signal to be effective when the counting value is larger than or equal to a preset value within first preset time;
the first timer is used for repeatedly timing, generating a counting reset signal after the first preset time, resetting the counting value according to the counting reset signal by the counting module and restarting counting;
the second timer starts timing when the intermediate indication signal is effective and generates a fault clearing signal after a second preset time; and
a latch module connected to the counting module and the second timer for latching the intermediate indication signal and generating a second indication signal according to the fault clearing signal and the intermediate indication signal,
and triggering single protection and starting timing when the second indication signal is effective, and recovering the normal working state when the fault clearing signal is effective.
2. The control circuit according to claim 1, wherein the first protection unit includes:
the comparison module compares the first reference voltage with the sampling voltage of the input current and generates a first indication signal according to a comparison result;
the fault management module is connected with the comparison module and generates the second control signal according to the first indication signal, the first control signal and the PWM reset signal;
when the sampling voltage of the input current is larger than or equal to the first reference voltage, judging that the input current is over-current, outputting the second control signal by the fault management module to turn off the power switch tube, and outputting the second control signal by the fault management module according to the PWM reset signal to turn on the power switch tube in the next PWM control period.
3. The control circuit of claim 2, wherein the fault management module comprises:
a first latch generating a first fail signal according to the PWM reset signal and the first indication signal;
an AND gate that generates the second control signal based on the first control signal and the first fault signal,
wherein the first fault signal is active when the first indication signal is active, and the first fault signal is inactive when the PWM reset signal is active and the first indication signal is inactive,
when the first fault signal is invalid, the state of the second control signal is consistent with the state of the first control signal, and when the first fault signal is valid, the second control signal is invalid.
4. The control circuit of claim 1, further comprising:
an input voltage sampling unit which samples an input voltage of the switching power supply to obtain a sampling voltage of the input voltage;
an output voltage sampling unit sampling an output voltage of the switching power supply to obtain a sampling voltage of the output voltage,
wherein the control unit generates the first control signal according to a sampling voltage of the input current, a target voltage, a sampling voltage of the input voltage, and a sampling voltage of the output voltage.
5. The control circuit of claim 4, wherein the control unit comprises:
a duty signal generation unit that generates a duty signal from the sampling voltage of the input current, the sampling voltage of the input voltage, the sampling voltage of the output voltage, and the target voltage; and
a PWM generating unit generating the first control signal and a PWM reset signal according to the duty ratio signal,
wherein the duty signal generating unit includes:
the first adding module is used for obtaining a first error according to the sampling voltage of the output voltage and the target voltage;
the first linear control module is used for obtaining an input current effective value according to the first error;
the phase calculation module is used for obtaining an input voltage phase value according to the sampling voltage of the input voltage;
the multiplication module is used for obtaining a target current signal according to the input current effective value and the input voltage phase value;
the second addition module is used for obtaining a second error according to the sampling voltage of the input current and the target current signal; and
and the second linear control module generates the duty ratio signal according to the second error.
6. The control circuit of claim 5, wherein the first linear control module and the second linear control module each comprise a PI controller.
7. The control circuit of claim 3, wherein the first protection unit is further configured to control the driving unit to turn off the power switch tube until a fault clearing signal is received when a number of times that the sampling voltage of the input current is greater than or equal to the first reference voltage within a first preset time reaches a preset value.
8. The control circuit of claim 3, wherein the fault management module further comprises:
a second latch to generate a second fail signal according to the PWM reset signal and the second indication signal,
wherein the second fail signal is active when the second indication signal is active, and the second fail signal is inactive when the PWM reset signal is active and the second indication signal is inactive,
when both the first fault signal and the second fault signal are invalid, the state of the second control signal is consistent with the state of the first control signal, and when one of the first fault signal and the second fault signal is valid, the second control signal is invalid.
9. The control circuit of claim 5, further comprising:
a threshold adjusting unit adjusting the target current signal to obtain the first reference voltage,
wherein the threshold adjusting unit includes:
the software adjusting module receives the target current signal and obtains a current-limiting protection threshold according to the target current signal; and
and the digital-to-analog conversion module is used for receiving the current-limiting protection threshold value and carrying out digital-to-analog conversion on the current-limiting protection threshold value to generate the first reference voltage.
10. The control circuit of claim 9, wherein the software adjustment module obtains the current-limiting protection threshold according to a maximum value of the target current signal, a magnitude of a current ripple, and a preset protection margin.
11. The control circuit according to claim 1, further comprising a load state detection unit that obtains a target voltage by detecting a load state of the switching power supply, the target voltage varying in accordance with a change in the load state.
12. The control circuit according to claim 1, further comprising a hardware protection unit receiving the sampled voltage of the input current, wherein the hardware protection unit generates a first trigger signal when the sampled voltage of the input current is greater than or equal to a second reference voltage, the driving unit turns off the power switch tube according to the first trigger signal, and the control unit controls the first control signal to be in an inactive state according to the first trigger signal,
the second reference voltage is used for representing a first overcurrent protection threshold value, and the second reference voltage is larger than the first reference voltage.
13. The control circuit of claim 1, further comprising a software protection unit receiving the sampled voltage of the input current, the software protection unit generating a second trigger signal when the sampled voltage of the input current is greater than or equal to a third reference voltage, the control unit controlling the first control signal to be in an inactive state according to the second trigger signal,
wherein the third reference voltage characterizes a second over-current protection threshold, and the first reference voltage is greater than the third reference voltage.
14. A switching power supply comprising a control circuit as claimed in any one of claims 1 to 13.
15. The switching power supply according to claim 14, further comprising:
a rectifier bridge rectifying an alternating input voltage to obtain the input voltage;
the inductor, the diode and the sampling resistor are connected to two ends of the rectifier bridge in series, and the anode of the diode is connected with the power switch tube and the middle node of the inductor;
and the output capacitor is connected between the middle node of the power switch tube and the sampling resistor and the cathode of the diode and is used for stabilizing output voltage.
16. A control method of a switching power supply, characterized by comprising:
sampling the input current to obtain a sampled voltage of the input current;
generating a first control signal;
generating a second control signal according to the sampling voltage of the input current, a first reference voltage and the first control signal; and
generating a driving signal for controlling the power switch tube according to the second control signal,
wherein the control method further comprises comparing the sampled voltage of the input current with the first reference voltage in each PWM control period, generating a first indication signal according to the comparison result, and triggering cycle-by-cycle protection when the first indication signal is valid, so as to turn off the power switch tube in the current PWM control period and turn on the power switch tube according to a PWM reset signal when the next PWM control period starts,
wherein the step of generating a second control signal according to the sampled voltage of the input current, a first reference voltage and the first control signal further comprises:
counting the first indicating signal to obtain a counting value, generating an intermediate indicating signal according to the counting value, and enabling the intermediate indicating signal to be effective when the counting value is larger than or equal to a preset value within first preset time;
generating a counting reset signal after the first preset time, resetting the counting value according to the counting reset signal, and restarting counting;
starting timing when the intermediate indication signal is effective, and generating a fault clearing signal after a second preset time; and
latching the intermediate indication signal and generating a second indication signal based on the fault clear signal and the intermediate indication signal,
and triggering single protection and starting timing when the second indication signal is effective, and recovering the normal working state when the fault clearing signal is effective.
17. The control method according to claim 16, characterized by further comprising:
and generating the first control signal according to the sampling voltage of the input current, the target voltage, the sampling voltage of the input voltage and the sampling voltage of the output voltage.
18. The control method according to claim 16, characterized by further comprising:
obtaining a target current signal according to the target voltage, the sampling voltage of the input voltage and the sampling voltage of the output voltage; and
and obtaining the first reference voltage according to the target current signal.
19. The control method according to claim 17, characterized by further comprising: the target voltage is obtained by detecting a load state of the switching power supply.
20. The control method of claim 16, wherein the step of generating a second control signal based on the sampled voltage of the input current, a first reference voltage, and the first control signal comprises:
comparing the first reference voltage with the sampling voltage of the input current, and generating a first indication signal according to the comparison result;
generating the second control signal according to the first indication signal and the first control signal.
21. The control method of claim 20, wherein the step of generating the second control signal according to the first indication signal and the first control signal comprises:
generating a first fault signal according to the PWM reset signal and the first indication signal;
generating the second control signal based on the first control signal and the first fault signal,
wherein the first fault signal is active when the first indication signal is active, and the first fault signal is inactive when the PWM reset signal is active and the first indication signal is inactive,
when the first fault signal is invalid, the state of the second control signal is consistent with the state of the first control signal, and when the first fault signal is valid, the second control signal is invalid.
22. The control method according to claim 21, characterized by further comprising: and when the times that the sampling voltage of the input current is greater than or equal to the first reference voltage within the first preset time reaches a preset value and a fault clearing signal is not received, the power switch tube is turned off.
23. The control method of claim 21, wherein the step of generating the second control signal according to the first indication signal and the first control signal further comprises:
generating a second fault signal based on the PWM reset signal and the second indication signal,
wherein the second fail signal is active when the second indication signal is active, and the second fail signal is inactive when the PWM reset signal is active and the second indication signal is inactive,
when both the first fault signal and the second fault signal are invalid, the state of the second control signal is consistent with the state of the first control signal, and when one of the first fault signal and the second fault signal is valid, the second control signal is invalid.
24. The control method of claim 18, wherein the step of deriving the first reference voltage from a target current signal comprises:
obtaining a current-limiting protection threshold according to the maximum value of the target current signal, the amplitude of the current ripple and a preset protection margin;
performing digital-to-analog conversion on the current-limiting protection threshold to generate the first reference voltage.
25. The control method of claim 17, wherein the step of generating the first control signal based on the sampled voltage of the input current, the target voltage, the sampled voltage of the input voltage, and the sampled voltage of the output voltage comprises:
obtaining a first error according to the sampling voltage of the output voltage and the target voltage;
obtaining an input current effective value according to the first error;
obtaining an input voltage phase value according to the sampling voltage of the input voltage;
obtaining a target current signal according to the input current effective value and the input voltage phase value;
obtaining a second error according to the sampling voltage of the input current and the target current signal;
generating a duty cycle signal according to the second error; and
and generating the first control signal and a PWM reset signal according to the duty ratio signal.
26. The control method according to claim 16, characterized by further comprising: generating a first trigger signal when the sampling voltage of the input current is greater than or equal to a second reference voltage, turning off the power switch tube according to the first trigger signal, and controlling the first control signal to be in an invalid state,
the second reference voltage is used for representing a first overcurrent protection threshold value, and the second reference voltage is larger than the first reference voltage.
27. The control method according to claim 16, characterized by further comprising: generating a second trigger signal when the sampling voltage of the input current is greater than or equal to a third reference voltage, controlling the first control signal to be in an invalid state according to the second trigger signal,
wherein the third reference voltage characterizes a second over-current protection threshold, and the first reference voltage is greater than the third reference voltage.
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