CN117595663A - Overcurrent protection control circuit and method suitable for BUCK-BOOST circuit - Google Patents

Overcurrent protection control circuit and method suitable for BUCK-BOOST circuit Download PDF

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Publication number
CN117595663A
CN117595663A CN202311631840.3A CN202311631840A CN117595663A CN 117595663 A CN117595663 A CN 117595663A CN 202311631840 A CN202311631840 A CN 202311631840A CN 117595663 A CN117595663 A CN 117595663A
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China
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circuit
operational amplifier
input end
output
voltage
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CN202311631840.3A
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CN117595663B (en
Inventor
王志宝
白洪超
陈道磐
赵迎辉
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Shandong Ainuo Intelligent Instrument Co ltd
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Shandong Ainuo Intelligent Instrument Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—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
    • H02M3/158—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 including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • 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
    • H02H7/1213—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 DC-DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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

Abstract

The invention belongs to the technical field of bidirectional direct current power supplies, and comprises a current sampling circuit, a control circuit, an overcurrent judging circuit, an overcurrent protection circuit and a main circuit, wherein the control circuit comprises a current inner loop regulating module and a PWM module.

Description

Overcurrent protection control circuit and method suitable for BUCK-BOOST circuit
Technical Field
The invention relates to the technical field of bidirectional direct current power supplies, in particular to an overcurrent protection control method suitable for a BUCK-BOOST circuit.
Background
Along with the rapid development of the current photovoltaic and new energy automobile industry, a direct current power supply with higher power needs to be adapted, and an overcurrent protection circuit needs to be added for the direct current power supply to limit the output of the direct current power supply so as to ensure the safe use of a switch power supply and driving equipment, however, the overcurrent protection circuit in the current heavy current switch power supply has more components and more complicated structures, and is unfavorable for saving the manufacturing cost.
The current overcurrent protection mode generally sets rated current, and when the rated current is exceeded, the power supply automatically stops running, but the power supply suddenly breaks off to influence the use, and damage is caused to circuit components. How to reduce the protection circuit components to ensure the reduction of manufacturing cost, and can realize the accurate protection of current, prolong the service life of the circuit, is a problem to be solved in the field of high-power direct current power supplies.
Disclosure of Invention
The invention aims to provide an overcurrent protection control mode suitable for a BUCK-BOOST circuit, which not only realizes protection of various power devices on the BUCK-BOOST circuit, but also can protect the power supply and equipment in time by temporarily closing an MOS tube without stopping operation when overcurrent occurs and enabling the MOS tube to work again after current drops.
The invention aims to achieve the aim, and the aim is achieved by the following technical scheme:
the overcurrent protection control circuit suitable for the BUCK-BOOST circuit comprises a current sampling circuit, a control circuit, an overcurrent judging circuit, an overcurrent protection circuit and a main circuit, wherein the control circuit comprises a current inner loop regulating module and a PWM module;
the input end of the current sampling circuit is connected with the main circuit, and the output end of the current sampling circuit is respectively connected with the current inner loop regulating module and the overcurrent judging circuit of the control circuit; the output of the overcurrent judgment circuit is connected with the overcurrent protection circuit; the overcurrent protection circuit and the PWM module are connected with the main circuit driving module.
In the control circuit, the output of the current inner loop regulating module is connected with the input end of the PWM module, and the output end of the PWM module is connected with one path of input end of the overcurrent protection circuit;
the output end of the overcurrent judging circuit is connected with one input end of the overcurrent protection circuit;
the output end of the overcurrent protection circuit is connected with the driving module of the main circuit and is used for controlling the current of the main circuit.
Preferably, the current sampling circuit is a differential amplifying circuit and comprises a sampling resistor, a first operational amplifier, an external circuit of the first operational amplifier, a second operational amplifier and an external circuit of the second operational amplifier, wherein two ends of the sampling resistor are respectively connected with a non-inverting input end and an inverting input end of the first operational amplifier, an output end of the first operational amplifier 1 is connected with the inverting input end of the second operational amplifier, and an output end of the second operational amplifier is connected with an input end of the current inner loop regulating module and an input end of the overcurrent judging circuit.
Preferably, the current inner loop regulating module comprises a third operational amplifier and an external circuit thereof, wherein the inverting input end of the third operational amplifier is connected with the output end of the current sampling circuit and the output end of the voltage outer loop, the non-inverting input end of the third operational amplifier is grounded, and the output end of the third operational amplifier is connected with the input end of the PWM module; the PWM module comprises a fourth operational amplifier and an external circuit thereof, wherein the non-inverting input end of the fourth operational amplifier is connected with the output of the current inner loop regulating module, the inverting input end of the fourth operational amplifier is connected with a modulation carrier wave, and the output end of the fourth operational amplifier is connected with one input end of the overcurrent protection circuit.
Preferably, the over-current judging circuit comprises a positive feedback circuit formed by a fifth operational amplifier and an external circuit thereof, a positive feedback circuit formed by a sixth operational amplifier and an external circuit thereof, a first diode, a second diode and a logic circuit, wherein the inverting input end of the fifth operational amplifier and the inverting input end of the sixth operational amplifier are connected with the output end of the current sampling circuit, the output end of the fifth operational amplifier is connected with the anode of the first diode, the output end of the sixth operational amplifier is connected with the input end of the logic circuit, the output end of the logic circuit is connected with the anode of the second diode, and the cathodes of the first diode and the second diode are respectively connected with the two input ends of the over-current protecting circuit.
Preferably, the inverting input end of the fifth operational amplifier is connected with the voltage division of the resistors R14 and R15 at the same time, the other end of the resistor R14 is connected with the output end of the current sampling circuit, the other end of the resistor R15 is connected with the reference voltage, and the reference voltage and the feedback resistor R18 are connected between the non-inverting input end and the output end of the fifth operational amplifier to form a positive feedback circuit; the inverting input end of the sixth operational amplifier is simultaneously connected with the voltage division of the resistors R19 and R20, the other end of the resistor R20 is connected with the output end of the current sampling circuit, the other end of the resistor R19 is connected with the reference voltage, and the reference voltage and the feedback resistor R23 are connected between the non-inverting input end and the output end of the sixth operational amplifier to form a positive feedback circuit.
Preferably, the logic circuit comprises a first NAND gate, two input ends of the first NAND gate are connected with the output end of the sixth operational amplifier, and the output end of the first NAND gate is connected with the anode of the second diode.
Preferably, the overcurrent protection circuit comprises a second NAND gate and a third NAND gate, two paths of input ends of the second NAND gate are respectively connected with the first diode and the cathode of the second diode, the output end of the second NAND gate is connected with one path of input end of the third NAND gate, the other path of input end of the third NAND gate is connected with the output end of the control circuit, and the output end of the third NAND gate is connected with the driving module of the main circuit and is used for outputting driving signals.
The invention also discloses an overcurrent protection control method suitable for the BUCK-BOOST circuit, which comprises the following steps:
the current sampling module is used for outputting a current sampling signal after the voltage at two ends of the resistor is collected and passes through the proportional amplifying circuit;
after the current sampling signal and the determined voltage value on the voltage outer ring output bus are subjected to loop regulation, the output signal is connected into a PWM module, and the PWM module outputs a modulation PWM wave;
the current sampling signal is also monitored by an overcurrent judging circuit, when the current in the main circuit is overlarge, the current sampling signal is increased, the overcurrent judging circuit sets the maximum value for the current sampling signal, and when the maximum value is exceeded, a protection mechanism is triggered to drive a power device MOS tube of the main circuit to stop or work.
Further, the method for judging the overcurrent comprises the following steps:
the over-current judging circuit comprises a positive feedback circuit formed by a fifth operational amplifier and an external circuit thereof, a positive feedback circuit formed by a sixth operational amplifier and an external circuit thereof, a first diode, a second diode and a logic circuit, wherein the inverting input end of the fifth operational amplifier and the inverting input end of the sixth operational amplifier are both connected with the output end of the current sampling circuit, the output end of the fifth operational amplifier is connected with the anode of the first diode, the output end of the sixth operational amplifier is connected with the input end of the first NAND gate, the output end of the first NAND gate is connected with the anode of the second diode, the cathodes of the first diode and the second diode are respectively connected with the two input ends of the over-current protection circuit, the output ends of the first diode and the second diode are simultaneously input into the second NAND gate in the over-current protection circuit, the output end of the second NAND gate and the output PWM modulation wave of the control circuit are simultaneously input into the third NAND gate, and the output of the third NAND gate is connected with the driving module;
when the BUCK-BOOST circuit works in the forward direction, the current sampling signal is positive, the voltage of the inverting input end of the fifth operational amplifier is larger than that of the non-inverting input end, the output voltage is-Vcc, and the first diode is not conducted; when the voltage of the inverting input end of the sixth operational amplifier is larger than the voltage of the non-inverting input end, triggering an overcurrent protection mechanism, changing the output voltage of the sixth operational amplifier from +Vcc to-Vcc, conducting a second diode, and changing the voltage of the input end of the second NAND gate from low level to high level;
when the BUCK-BOOST circuit works reversely, the current sampling signal is negative, the voltage of the inverting input end of the sixth operational amplifier is negative, the output voltage of the sixth operational amplifier is +Vcc, and the second diode is not conducted; when the voltage of the inverting input end of the fifth operational amplifier is smaller than the voltage of the non-inverting input end, triggering an overcurrent protection mechanism, changing the output voltage of the fifth operational amplifier from-Vcc to +Vcc, conducting a first diode, and changing the voltage of the input end of the second NAND gate from low level to high level;
when the voltage of the input end of the second NAND gate is changed from high to low, the output voltage of the third NAND gate is changed to high level, the duty ratio of the PWM signal output by the driving module is changed to 0, the power device MOS tube of the main circuit stops working, and the current is reduced.
The recovery condition after the forward work of the BUCK-BOOST circuit triggers the overcurrent protection is as follows:
when the voltage at the inverting input of the sixth operational amplifier drops below the non-inverting input. The overcurrent protection mechanism is relieved, the output voltage of the sixth operational amplifier is changed from-Vcc to +Vcc, the output voltage of the first NAND gate is changed from high level to low level, the second diode is cut off, the voltage of the input end of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave;
the recovery condition after the reverse work of the BUCK-BOOST circuit triggers the overcurrent protection is as follows:
when the voltage of the inverting input end of the fifth operational amplifier rises to be larger than that of the non-inverting input end, the overcurrent protection mechanism is released, the output voltage of the fifth operational amplifier is changed from +Vcc to-Vcc, the first diode is cut off, the voltage of the input end of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave.
The invention has the advantages that: and comparing the collected current with the upper limit value of the current to judge whether the current in the main circuit exceeds an allowable value, and when an overcurrent condition occurs, temporarily stopping the circuit by turning off the power device to reduce the current in the main circuit. The circuit has the advantages of fewer components, accurate control, increased reliability and reduced cost.
Drawings
FIG. 1 is a schematic diagram of the connection of the BUCK-BOOST overcurrent protection control mode of the invention;
FIG. 2 is a circuit diagram of an over-current protection control circuit suitable for a BUCK-BOOST circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
The embodiment discloses an overcurrent protection control circuit suitable for a BUCK-BOOST circuit, referring to FIG. 1, comprising a current sampling circuit, a control circuit, an overcurrent judging circuit, an overcurrent protection circuit and a main circuit, wherein the control circuit comprises a current inner loop regulating module and a PWM module.
The current sampling circuit is a differential amplifying circuit and comprises a sampling resistor R1, a first operational amplifier 1, an external circuit of the first operational amplifier, a second operational amplifier 2 and an external circuit of the second operational amplifier, wherein two ends of the sampling resistor R1 are respectively connected to a non-inverting input end and an inverting input end of the first operational amplifier 1 through resistors R3 and R2, a resistor R5 and a capacitor C1 which are connected in parallel are connected between the inverting input end and the output end of the first operational amplifier 1, the output end of the first operational amplifier 1 is connected with the inverting input end of the second operational amplifier 2 through a resistor R6, the non-inverting input end of the second operational amplifier 2 is grounded after being divided by resistors R7 and R8, and a resistor R9 and a capacitor C3 which are connected in parallel are connected between the inverting input end and the output end.
The current inner loop regulating module comprises a third operational amplifier 3 and an external circuit thereof, wherein the inverting input end of the third operational amplifier 3 is connected with the output end of the second operational amplifier 2 through a resistor R10, the inverting input end is also connected with the output of the voltage outer loop through a resistor R11, the non-inverting input end is grounded through a resistor R24, a resistor R12 and a capacitor C4 which are connected in series are connected between the output end and the inverting input end, the PWM module is a fourth operational amplifier 4, the non-inverting input end of the PWM module is connected with the input end of the third operational amplifier 3 through a resistor R13, the inverting input end is connected with a modulation carrier, and the output end is connected with one input end of a third NAND gate of the overcurrent protection circuit to input PWM signals.
The over-current judging circuit comprises a positive feedback circuit formed by a fifth operational amplifier 5 and an external circuit thereof, a positive feedback circuit formed by a sixth operational amplifier 6 and an external circuit thereof, a first diode D1, a second diode D2 and a logic circuit, wherein the inverting input end of the fifth operational amplifier 5 is respectively connected with the output end of the second operational amplifier 2 and a reference voltage Vref after being divided by resistors R14 and R15, the non-inverting input end is respectively connected with the reference voltage Vref, a ground wire GND and the output end of the fifth operational amplifier 5 after being divided by resistors R16, R17 and R18, the output end of the fifth operational amplifier 5 is connected with the anode of the first diode,
the inverting input end of the sixth operational amplifier 6 is connected with the ground wire GND and the output end of the second operational amplifier 2 after being divided by the resistors R19 and R20, the non-inverting input end is connected with the reference voltage Vref, the ground wire GND and the output end of the sixth operational amplifier 6 after being divided by the resistors R21, R22 and R23, the output end of the sixth operational amplifier 6 is connected with the two input ends of the first NAND gate, the output end of the first NAND gate is connected with the anode of the second diode D2, and the cathodes of the first diode D1 and the second diode D2 are respectively connected with the two input ends of the second NAND gate in the overcurrent protection circuit.
The output end of the second NAND gate is connected with the other input end of the third NAND gate, and the output end of the third NAND gate is connected with the driving module of the main circuit and used for outputting driving signals to control the MOS tube.
Example 2
The embodiment discloses an overcurrent protection control method applicable to a BUCK-BOOST circuit based on the circuit of the embodiment 1, which comprises the following steps:
the current sampling module is used for collecting voltages at two ends of the resistor and outputting a current sampling signal after passing through the proportional amplifying circuit. The voltage U1 obtained on the sampling resistor R1 is amplified to obtain U2:
u1 is the voltage of the connection point of R1 and R2, and U2 is the voltage of the output end of the first operational amplifier 1.
In order to make the obtained current sampling signal become the voltage signal with the same current direction, a two-stage amplifying circuit consisting of operational amplifier 2 is added, and its output voltage U3 is the current sampling signal
The magnitude of the current in the main circuit can be controlled by monitoring the U3 value. When the current in the main circuit is too large, U3 will become large, the overcurrent judging circuit sets a maximum value for U3, and when U3 exceeds the maximum value, the subsequent protection mechanism will be triggered.
When the BUCK-BOOST circuit works in the forward direction, the current sampling signal is positive, the voltage U4 of the inverting input end of the fifth operational amplifier is larger than the voltage U5 of the non-inverting input end, the output voltage is Vcc, and D1 is not conducted;
when the inverting input terminal voltage U6 of the sixth operational amplifier is larger than the non-inverting input terminal voltage U7, an overcurrent protection mechanism is triggered, the output voltage of the sixth operational amplifier is changed from +Vcc to-Vcc, D2 is conducted, and the input terminal voltage of the second NAND gate is changed from low level to high level.
When the BUCK-BOOST circuit works reversely, the current sampling signal is negative, U6 is less than 0, the output voltage of the sixth operational amplifier is +Vcc, and D2 is not conducted;
when U4 falls to U4< U5, triggering an overcurrent protection mechanism, changing the output voltage of the fifth operational amplifier from-Vcc to +Vcc, turning on D1, and changing the input voltage of the second NAND gate from low level to high level;
when the voltage of the input end of the second NAND gate is high, the output signal driver_stop of the second NAND gate is changed from high to low, the output voltage of the third NAND gate is changed to high level, the duty ratio of the PWM signal output by the driving module is changed to 0, the power device MOS tube of the main circuit stops working, and the current is reduced.
In the main circuit, as the absolute value of current is rapidly reduced due to the fact that the MOS tube stops working, U3 of the current sampling circuit and U4 or U6 of the overcurrent judging circuit are also changed along with the change of U3, overcurrent protection is relieved to a certain moment, and recovery conditions after the overcurrent protection is triggered by forward working of the BUCK-BOOST circuit are as follows:
after triggering the protection, the voltage value of U7 becomes
When U6 drops to U6< U7. The over-current protection mechanism is released, the output voltage of the sixth operational amplifier is changed from-Vcc to +Vcc, the output voltage of the first NAND gate is changed from high level to low level, D2 is cut off, the input end voltage of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave again.
The recovery condition after the reverse work of the BUCK-BOOST circuit triggers the overcurrent protection is as follows:
after triggering the protection, the voltage value of U5 becomes
When U4 rises to U4> U5, the overcurrent protection mechanism is released, the output voltage of the fifth operational amplifier is changed from +Vcc to-Vcc, the first diode is cut off, the voltage of the input end of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave again.
Finally, it should be noted that: the foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. The overcurrent protection control circuit is suitable for the BUCK-BOOST circuit and is characterized by comprising a current sampling circuit, a control circuit, an overcurrent judging circuit, an overcurrent protection circuit and a main circuit, wherein the control circuit comprises a current inner loop regulating module and a PWM module;
the input end of the current sampling circuit is connected with the main circuit, and the output end of the current sampling circuit is respectively connected with the current inner loop regulating module and the overcurrent judging circuit of the control circuit; the output of the overcurrent judgment circuit is connected with the overcurrent protection circuit; the overcurrent protection circuit and the PWM module are connected with the main circuit driving module.
In the control circuit, the output of the current inner loop regulating module is connected with the input end of the PWM module, and the output end of the PWM module is connected with one path of input end of the overcurrent protection circuit;
the output end of the overcurrent judging circuit is connected with one input end of the overcurrent protection circuit;
the output end of the overcurrent protection circuit is connected with the driving module of the main circuit and is used for controlling the current of the main circuit.
2. The overcurrent protection control circuit suitable for the BUCK-BOOST circuit according to claim 1, wherein the current sampling circuit is a differential amplifying circuit and comprises a sampling resistor, a first operational amplifier, an external circuit of the first operational amplifier, a second operational amplifier and an external circuit of the second operational amplifier, two ends of the sampling resistor are respectively connected with a non-inverting input end and an inverting input end of the first operational amplifier, an output end of the first operational amplifier 1 is connected with an inverting input end of the second operational amplifier, and an output end of the second operational amplifier is connected with an input end of a current inner loop adjusting module and an input end of an overcurrent judging circuit.
3. The overcurrent protection control circuit suitable for the BUCK-BOOST circuit according to claim 1, wherein the current inner loop regulating module comprises a third operational amplifier and an external circuit thereof, an inverting input end of the third operational amplifier is connected with an output end of the current sampling circuit and an output end of a voltage outer loop, a non-inverting input end of the third operational amplifier is grounded, and an output end of the third operational amplifier is connected with an input end of the PWM module; the PWM module comprises a fourth operational amplifier and an external circuit thereof, wherein the non-inverting input end of the fourth operational amplifier is connected with the output of the current inner loop regulating module, the inverting input end of the fourth operational amplifier is connected with a modulation carrier wave, and the output end of the fourth operational amplifier is connected with one input end of the overcurrent protection circuit.
4. The overcurrent protection control circuit suitable for the BUCK-BOOST circuit according to claim 1, wherein the overcurrent judging circuit comprises a positive feedback circuit formed by a fifth operational amplifier and an external circuit thereof, a positive feedback circuit formed by a sixth operational amplifier and an external circuit thereof, a first diode, a second diode and a logic circuit, wherein an inverting input end of the fifth operational amplifier and an inverting input end of the sixth operational amplifier are connected with an output end of the current sampling circuit, an output end of the fifth operational amplifier is connected with a first diode anode, an output end of the sixth operational amplifier is connected with an input end of the logic circuit, an output end of the logic circuit is connected with a second diode anode, and cathodes of the first diode and the second diode are respectively connected with two input ends of the overcurrent protection circuit.
5. The overcurrent protection control circuit suitable for the BUCK-BOOST circuit according to claim 4, wherein the inverting input end of the fifth operational amplifier is connected with the voltage division of the resistor R14 and the resistor R15 simultaneously, the other end of the resistor R14 is connected with the output end of the current sampling circuit, the other end of the resistor R15 is connected with the reference voltage, and the reference voltage and the feedback resistor R18 are connected between the non-inverting input end and the output end of the fifth operational amplifier to form a positive feedback circuit; the inverting input end of the sixth operational amplifier is simultaneously connected with the voltage division of the resistors R19 and R20, the other end of the resistor R20 is connected with the output end of the current sampling circuit, the other end of the resistor R19 is connected with the reference voltage, and the reference voltage and the feedback resistor R23 are connected between the non-inverting input end and the output end of the sixth operational amplifier to form a positive feedback circuit.
6. The overcurrent protection control circuit for the BUCK-BOOST circuit according to claim 4, wherein the logic circuit includes a first nand gate, both input terminals of the first nand gate are connected to the output terminal of the sixth operational amplifier, and the output terminal of the first nand gate is connected to the anode of the second diode.
7. The overcurrent protection control circuit for the BUCK-BOOST circuit according to claim 4, wherein the overcurrent protection circuit comprises a second nand gate and a third nand gate, the two input ends of the second nand gate are respectively connected with the first diode and the cathode of the second diode, the output end of the second nand gate is connected with one input end of the third nand gate, the other input end of the third nand gate is connected with the output end of the control circuit, and the output end of the third nand gate is connected with the driving module of the main circuit for outputting driving signals.
8. The overcurrent protection control method suitable for the BUCK-BOOST circuit is characterized by comprising the following steps:
the current sampling module is used for outputting a current sampling signal after the voltage at two ends of the resistor is collected and passes through the proportional amplifying circuit;
after the current sampling signal and the determined voltage value on the voltage outer ring output bus are subjected to loop regulation, the output signal is connected into a PWM module, and the PWM module outputs a modulation PWM wave;
the current sampling signal is also monitored by an overcurrent judging circuit, when the current in the main circuit is overlarge, the current sampling signal is increased, the overcurrent judging circuit sets the maximum value for the current sampling signal, and when the maximum value is exceeded, a protection mechanism is triggered to drive a power device MOS tube of the main circuit to stop or work.
9. The overcurrent protection control method applicable to the BUCK-BOOST circuit according to claim 8, wherein the overcurrent judgment method is as follows:
the over-current judging circuit comprises a positive feedback circuit formed by a fifth operational amplifier and an external circuit thereof, a positive feedback circuit formed by a sixth operational amplifier and an external circuit thereof, a first diode, a second diode and a logic circuit, wherein the inverting input end of the fifth operational amplifier and the inverting input end of the sixth operational amplifier are both connected with the output end of the current sampling circuit, the output end of the fifth operational amplifier is connected with the anode of the first diode, the output end of the sixth operational amplifier is connected with the input end of the first NAND gate, the output end of the first NAND gate is connected with the anode of the second diode, the cathodes of the first diode and the second diode are respectively connected with the two input ends of the over-current protection circuit, the output ends of the first diode and the second diode are simultaneously input into the second NAND gate in the over-current protection circuit, the output end of the second NAND gate and the output PWM modulation wave of the control circuit are simultaneously input into the third NAND gate, and the output of the third NAND gate is connected with the driving module;
when the BUCK-BOOST circuit works in the forward direction, the current sampling signal is positive, the voltage of the inverting input end of the fifth operational amplifier is larger than that of the non-inverting input end, the output voltage is-Vcc, and the first diode is not conducted; when the voltage of the inverting input end of the sixth operational amplifier is larger than the voltage of the non-inverting input end, triggering an overcurrent protection mechanism, changing the output voltage of the sixth operational amplifier from +Vcc to-Vcc, conducting a second diode, and changing the voltage of the input end of the second NAND gate from low level to high level;
when the BUCK-BOOST circuit works reversely, the current sampling signal is negative, the voltage of the inverting input end of the sixth operational amplifier is negative, the output voltage of the sixth operational amplifier is +Vcc, and the second diode is not conducted; when the voltage of the inverting input end of the fifth operational amplifier is smaller than the voltage of the non-inverting input end, triggering an overcurrent protection mechanism, changing the output voltage of the fifth operational amplifier from-Vcc to +Vcc, conducting a first diode, and changing the voltage of the input end of the second NAND gate from low level to high level;
when the voltage of the input end of the second NAND gate is changed from high to low, the output voltage of the third NAND gate is changed to high level, the duty ratio of the PWM signal output by the driving module is changed to 0, the power device MOS tube of the main circuit stops working, and the current is reduced.
10. The overcurrent protection control method applicable to the BUCK-BOOST circuit according to claim 9, wherein the recovery condition after the BUCK-BOOST circuit is triggered to operate in the forward direction is:
when the voltage at the inverting input of the sixth operational amplifier drops below the non-inverting input. The overcurrent protection mechanism is relieved, the output voltage of the sixth operational amplifier is changed from-Vcc to +Vcc, the output voltage of the first NAND gate is changed from high level to low level, the second diode is cut off, the voltage of the input end of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave;
the recovery condition after the reverse work of the BUCK-BOOST circuit triggers the overcurrent protection is as follows:
when the voltage of the inverting input end of the fifth operational amplifier rises to be larger than that of the non-inverting input end, the overcurrent protection mechanism is released, the output voltage of the fifth operational amplifier is changed from +Vcc to-Vcc, the first diode is cut off, the voltage of the input end of the second NAND gate is changed from high level to low level, and the output signal of the third NAND gate is changed into PWM modulation wave.
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