CN111049382B - BUCK control circuit and control method thereof - Google Patents

BUCK control circuit and control method thereof Download PDF

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Publication number
CN111049382B
CN111049382B CN201911406626.1A CN201911406626A CN111049382B CN 111049382 B CN111049382 B CN 111049382B CN 201911406626 A CN201911406626 A CN 201911406626A CN 111049382 B CN111049382 B CN 111049382B
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terminal
control
tube
driving
unit
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CN111049382A (en
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李湘
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Mornsun Guangzhou Science and Technology Ltd
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Mornsun Guangzhou Science and Technology 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
    • H02M3/1588—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 comprising at least one synchronous rectifier element
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a BUCK control circuit, which comprises a control unit and a main power unit, wherein the control unit comprises a control IC and a capacitor C11, the main power unit is a BUCK synchronous rectification circuit and comprises a main switching tube TR1, a synchronous rectification tube TR2 and an inductor L1, the drain electrode of the main switching tube TR1 is electrically connected with the input end Vin of a power supply, the source electrode of the main switching tube TR1 is electrically connected with the drain electrode of the synchronous rectification tube TR2 and is simultaneously and electrically connected with the first terminal of the inductor L1, the source electrode of the synchronous rectification tube TR2 is grounded, the second terminal of the inductor L1 is led out to be the output end of the BUCK circuit, the BUCK control circuit also comprises a power supply unit and a driving unit, the driving unit comprises a driving IC and a capacitor C21, wherein the input of the power supply unit is electrically coupled to the power input Vin, and the output of the power supply unit is electrically coupled to the first terminal Vin of the control IC in the control unit and simultaneously to the first terminal VDD of the drive IC in the drive unit. The invention realizes a high-voltage input control circuit, and can solve the problem that the input voltage of the BUCK circuit is limited by the maximum input voltage of a control IC.

Description

BUCK control circuit and control method thereof
Technical Field
The present invention relates to a control circuit of a BUCK converter, and more particularly, to a control circuit of a BUCK converter and a control method thereof when an input voltage is high.
Background
The BUCK circuit has the advantages of simple circuit, low cost, high dynamic response speed and the like, and is widely applied to occasions without isolation, particularly voltage and large current occasions. The core device is a BUCK control IC, and the grid electrode of the main switch tube is not grounded, so that the main switch tube is driven in a floating mode. Because the cost performance and the universality of the N-MOS are superior to those of the P-MOS, the BUCK IC on the market is almost designed by matching with the N-MOS. When the main switch tube adopts N-MOS, when the main switch tube is conducted, the grid voltage is about the input voltage, and in order to ensure the normal conduction of the main switch tube, the driving voltage of the main switch tube must be greater than the input voltage. The BUCK circuit generally has a boost module, and the boost circuit is integrated in the BUCK IC. As shown in fig. 1, most of BUCK ICs have a built-in bootstrap circuit for boosting, and only one external bootstrap capacitor is needed, and the bootstrap circuit can generate a voltage higher than an input voltage by about 5V for driving and supplying power to the main switching tube.
Although the stress of the external MOS transistor is not limited, the BUCK IC can also adopt a voltage stabilizing circuit to supply power, but the maximum input voltage of the BUCK circuit in the traditional scheme is limited by the maximum input voltage of the BUCK control IC due to the limitation of the driving voltage.
In the occasion of input voltage less than 60V, there are many general BUCK control ICs on the market, but in the occasion of higher input, for example, when the input voltage is 60-600V, especially the BUCK control ICs with input voltage more than 75V are few, and because the high-voltage input BUCK control ICs are high in cost and difficult to be widely applied, the BUCK topology is limited in the occasion of high-voltage input because it is difficult to select proper control ICs.
Disclosure of Invention
The invention aims to solve the problems of difficult selection, poor universality and high cost of the high-voltage input BUCK circuit, and provides the BUCK control circuit suitable for high-voltage input, which is mainly characterized in that the control IC with conventional input voltage (within 60V) is adopted to control the BUCK circuit with the highest input voltage more than 60V, and the method has a simple and reliable circuit structure and is easy to realize and put into practical use.
The invention aims to realize that the BUCK control circuit comprises a control unit and a main power unit, wherein the control unit comprises a control IC and a capacitor C11, the main power unit is a BUCK synchronous rectification circuit and comprises a main switching tube TR1, a rectification tube and an inductor L1, the rectification tube adopts a synchronous rectification tube TR2, the drain electrode of the main switching tube TR1 is electrically connected with a power supply input end Vin, the source electrode of the main switching tube TR1 is electrically connected with the drain electrode of the synchronous rectification tube TR2 and is simultaneously and electrically connected with a first terminal of the inductor L1, the source electrode of the synchronous rectification tube TR2 is grounded, a second terminal of the inductor L1 is led out to be a BUCK circuit output end, the control unit further comprises a power supply unit and a drive unit, the drive unit comprises a drive IC and a capacitor C21, wherein the power supply unit converts an input voltage into a lower direct current voltage suitable for supplying power to the conventional control IC, the input end of the power supply unit is electrically connected with the power supply input end Vin, and the first terminal of the control IC in the output end control unit is electrically connected with the VIN A first terminal VDD of a driving IC in the driving unit; a control unit for generating a control signal without DC bias, wherein the control signal can be directly input to an input terminal of the driving IC, a first terminal VIN of the control IC is electrically connected with an output terminal of the power supply unit, a second terminal GND of the control IC is grounded, a third terminal BST of the control IC is electrically connected with a first terminal of the capacitor C11, and a fourth terminal SW of the control IC is electrically connected with a second terminal of the capacitor C11 and is also electrically connected with the second terminal GND; the driving unit is used for converting the control signal generated by the control unit into a driving voltage signal capable of directly controlling the switching of the MOS tube, a first terminal VDD of an isolation driving IC is electrically connected with the output end of the power supply circuit, a second terminal HI is electrically connected with a sixth terminal TG of the control IC, a third terminal LI is electrically connected with a fifth terminal BG of the control IC, a fourth terminal VSS is grounded, the fifth terminal LO is electrically connected with a grid electrode of a synchronous rectifier tube TR2, a sixth terminal HB is electrically connected with a first terminal of a capacitor C21, a seventh terminal HS is electrically connected with a second terminal of the C21 and is simultaneously electrically connected with a source electrode of a main switch tube TR1, and an eighth terminal HO is electrically connected with the grid electrode of the main switch tube TR 1.
Preferably, the power supply unit includes a resistor R1, a regulator D1, an NPN transistor Q1 and a capacitor C1, a first terminal of the resistor R1 is electrically coupled to the power input Vin, a second terminal of the resistor R1 is electrically coupled to a base of the transistor Q1 and is also electrically coupled to a cathode of the regulator D1, an anode of the regulator D1 is grounded, a collector of the transistor Q1 is electrically connected to the power input Vin, an emitter of the transistor Q1 is electrically coupled to a first terminal of the capacitor C1 and serves as an output terminal of the power supply unit, and is also electrically coupled to a first terminal Vin of the control IC and a first terminal VDD of the driver ICU2, and a second terminal of the capacitor C1 is grounded.
Preferably, the rectifier tube of the main power unit is a diode D2, the source of the switching tube TR1 is electrically coupled to the cathode of the diode D2 and is also electrically coupled to the first terminal of the inductor L1, and the anode of the diode D2 is grounded; the driving unit further comprises a MOS tube TR3, a fifth terminal LO of the driving IC is electrically connected with a grid electrode of the MOS tube TR3, a drain electrode of the MOS tube TR3 is electrically connected with a seventh terminal HS of the driving IC U2, and a source electrode of the MOS tube TR3 is grounded.
The invention also provides a BUCK control circuit, which comprises a control unit, a driving unit and a main power unit, wherein the control unit comprises a control IC and a capacitor C11 connected between the SW end and the BST end of the control IC, the main power unit comprises a switching tube TR1, an inductor L1 and a rectifying tube, the rectifying tube adopts a synchronous rectifying tube TR2, the drain electrode of the switching tube TR1 is connected with a power input end Vin, the source electrode of the switching tube TR1 is respectively connected with the drain electrode of the synchronous rectifying tube TR2 and the first end of the inductor L1, the source electrode of the synchronous rectifying tube TR2 is grounded, the second end of the inductor L1 is led out as a power output end, the BUCK control circuit further comprises a power supply unit for converting an input voltage into a lower direct current voltage suitable for supplying power to the conventional control IC, and the driving unit comprises a driving IC and a capacitor C21 connected between the seventh terminal HS and the sixth terminal HB of the driving IC; the input end of the power supply unit is connected with the power input end Vin, and the output end of the power supply unit is respectively connected with the first terminal VIN of the control IC and the first terminal VDD of the drive IC; the fourth terminal SW and the second terminal GND of the control IC are grounded, the fifth terminal BG of the control IC is connected with the third terminal LI of the drive IC, and the sixth terminal TG of the control IC is connected with the second terminal HI of the drive IC; the fourth terminal VSS of the driver IC is grounded, the fifth terminal LO of the driver IC is connected to the gate of the synchronous rectifier TR2, the seventh terminal HS of the driver IC is further connected to the source of the switching transistor TR1, and the eighth terminal HO of the driver IC is connected to the gate of the switching transistor TR 1.
Preferably, the power supply unit comprises a resistor R1, a regulator tube D1, an NPN transistor Q1 and a capacitor C1, wherein a first terminal of the resistor R1 is electrically coupled to the power input Vin, a second terminal of the resistor R1 is electrically coupled to a base of the transistor Q1 and is also electrically coupled to a cathode of the regulator tube D1, an anode of the regulator tube D1 is grounded, a collector of the transistor Q1 is electrically connected to the power input Vin, an emitter of the transistor Q1 is electrically coupled to a first terminal of the capacitor C1 and serves as an output terminal of the power supply unit, and is also electrically coupled to a first terminal Vin of the control IC and a first terminal VDD of the driver ICU2, and a second terminal of the capacitor C1 is grounded.
Preferably, the rectifier tube of the main power unit adopts a diode D2, the cathode of the diode D2 is connected with the source of the switching tube TR1, and the anode of the diode D2 is grounded; the driving unit further comprises a MOS tube TR3, the gate of the MOS tube TR3 is connected with the LO end of the driving IC, the drain of the MOS tube TR3 is connected with the source of the switching tube TR1, and the source of the MOS tube TR3 is grounded.
The invention further provides a control method of the BUCK circuit, which comprises the following steps that in the input voltage conversion step, the input voltage is converted into a lower first direct current voltage suitable for the power supply of the conventional control IC through a power supply unit and is output to a power supply end of the control unit; a step of converting a non-floating signal to a floating signal, wherein a first direct current voltage is respectively connected to power supply ends of a control IC and a drive IC, an SW end of the control IC is grounded, and the control IC generates a control signal which is directly connected to the drive IC so as to generate a first control signal of the non-floating through the control IC and directly provide the first control signal to the drive IC; the VSS end of the driving IC is grounded, the HO end of the driving IC outputs a second control signal of floating ground, so that the first control signal which is not floating ground and is generated by the control unit is converted into the second control signal of floating ground through the driving IC, and the driving voltage signal for the grid electrode of the switching tube is directly output.
The high-voltage input voltage is converted into the low voltage suitable for the power supply of the BUCK control IC and the drive IC through the power supply unit, and the fourth terminal SW of the BUCK control IC is grounded, so that a control signal generated by the BUCK control IC is a non-floating signal and can be directly input to the drive IC for control; the withstand voltage of the sixth terminal, the seventh terminal and the eighth terminal of the common isolation drive IC in the market can be more than 600V, and the power supply unit can easily realize high-voltage input, so the control circuit can easily realize the control of the BUCK circuit with high input voltage by adopting the control IC with low cost and good universality.
Compared with the prior art, the invention has the following beneficial effects:
1. the problem that the input voltage of the BUCK circuit is limited by the maximum input voltage of the control IC can be solved;
2. the control IC is easy to select types when high-voltage input is carried out, not only can general materials be adopted, but also the system cost can be reduced, and the normalization of a material platform is facilitated.
Drawings
FIG. 1 is a circuit schematic of a conventional BUCK control scheme;
FIG. 2 is a schematic circuit diagram of a BUCK control circuit according to a first embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of a BUCK control circuit according to a first embodiment of the present invention;
FIG. 4 is a schematic circuit diagram of a BUCK control circuit according to a second embodiment of the present invention.
Detailed Description
First embodiment
FIG. 3 shows a schematic diagram of a BUCK control circuit according to a first embodiment of the present invention, wherein the topology of the power stage is BUCK topology. The BUCK topology comprises a main switching tube TR1, a synchronous rectifying tube TR2 and a main power inductor L1, wherein the drain electrode of the TR1 is electrically connected with a power supply input end, the source electrode of the TR1 is electrically connected with the drain electrode of the TR2 and is simultaneously electrically connected to a first terminal of the main power inductor L1, the source electrode of the TR2 is electrically connected with GND, and the second terminal of the main power inductor L1 is electrically connected with an output end Vo.
The BUCK control circuit comprises a power supply unit, a control unit and a driving unit, wherein the power supply unit converts an input voltage into a lower direct-current voltage suitable for supplying power to a conventional control IC, the power supply unit comprises a resistor R1, a voltage regulator tube D1, an NPN triode Q1 and a filter capacitor C1, a first terminal of the resistor R1 is electrically coupled to a power supply input terminal Vin, a second terminal of the resistor R1 is electrically coupled to a base electrode of a triode Q1 and a first terminal of the voltage regulator tube D1, a second terminal of the D1 is electrically coupled to GND, a collector of a triode Q1 is electrically connected to the input terminal, an emitter of the triode Q1 is electrically coupled to a first terminal of the filter capacitor C1 and is electrically coupled to the first terminal VIN of the U1 and the first terminal VDD of the U2 at the same time, and a second terminal of the C1 is electrically coupled to GND.
The control unit comprises a control IC U1 and a bootstrap capacitor C11, for generating a control signal without dc bias, and the control signal can be directly input to the input terminal of the driving IC, the control IC includes a first terminal VIN, a second terminal GND, a third terminal BST, a fourth terminal SW, a fifth terminal BG, and a sixth terminal TG, the control IC comprises a VIN end, a GND end, a BST end, a switch output pin, a BG end, a TG end, a first terminal of a control IC, a GND end, a second terminal of the control IC, a bootstrap capacitor C11 and a fourth terminal of the control IC, wherein the VIN end is a power supply pin, the GND end is a ground pin, the BST end is a main switching tube grid power supply pin, the SW end is a switch output pin, the BG end is a synchronous rectifying tube driving signal output pin, the TG end is a main switching tube driving signal output pin, the VIN end of the control IC is electrically connected with the output end of a power supply unit, the GND end of the second terminal of the control IC is grounded, the BST end of the control IC is electrically connected with the first terminal of the bootstrap capacitor C11, and the SW end of the fourth terminal of the control IC is electrically connected with the second terminal of the bootstrap capacitor C11 and is electrically connected with the GND end; the drive unit comprises an isolation drive IC U2 and a bootstrap capacitor C21, which are used for converting a control signal generated by the control unit into a drive voltage signal capable of directly controlling the MOS tube switch, an isolation drive IC U2, which comprises a first terminal VDD, a second terminal HI, a third terminal LI, a fourth terminal VSS, a fifth terminal LO, a sixth terminal HB, a seventh terminal HS and an eighth terminal HO, wherein the VDD terminal is a power supply pin, the HI terminal is a logic input pin of a high-voltage side gate drive output, the LI terminal is a logic input pin of the high-voltage side gate drive output, the VSS terminal is a ground reference pin, the LO terminal is a low-voltage side gate drive output pin, the HB terminal is a power supply pin of an isolation driver, the HS is a high-voltage side gate drive signal reference pin, the HO is a high-voltage side gate drive output pin, the first terminal VDD of the isolation drive IC 2 is electrically connected with the output end of the power supply circuit, and the sixth terminal of the second terminal of the control IC, the third terminal LI is electrically connected with a fifth terminal BG of the control IC, the fourth terminal VSS is grounded, the fifth terminal LO is electrically connected with a grid electrode of a synchronous rectifier tube TR2, the sixth terminal HB is electrically connected with a first terminal of a bootstrap capacitor C21, the seventh terminal HS is electrically connected with a second terminal of the C21 and is simultaneously electrically connected with a source electrode of a main switching tube TR1, and the eighth terminal HO is electrically connected with a grid electrode of the main switching tube TR 1. The control circuit can realize the control of the high input voltage BUCK circuit by adopting a more universal and low-cost low input voltage control IC.
The BUCK control circuit is particularly suitable for high-voltage input occasions, a driving signal of a conventional low-voltage control IC main switching tube is converted from a floating signal to a non-floating signal, and the high-voltage input power supply circuit and the driving circuit are combined to realize the high-voltage input control circuit.
Second embodiment
FIG. 4 shows a schematic diagram of a BUCK control circuit according to a second embodiment of the present invention, wherein the topology of the power stage is BUCK topology. Different from the first embodiment are a main power unit and a driving unit.
The main power unit is a diode rectification circuit and comprises a main switching tube TR1, a follow current tube D2 and a main power inductor L1, the drain electrode of the main switching tube TR1 is electrically connected with the power input end Vin, the source electrode of the main switching tube TR1 is electrically connected with the cathode of the D2 and is also electrically connected with the first terminal of the main power inductor L1, the anode of the D2 is electrically connected with the ground GND, and the second terminal of the main power inductor L1 is electrically connected with the output; the driving unit comprises an isolation driving IC U2, a bootstrap capacitor C21 and a MOS tube TR3, and is used for converting a control signal generated by the control unit into a driving voltage signal capable of directly controlling the switching of the MOS tube, a first terminal of the isolation driving IC U2 is electrically connected with the output end of a power supply circuit, a second terminal HI is electrically connected with a sixth terminal TG of the control IC, a third terminal LI is electrically connected with a fifth terminal BG of the control IC, a fourth terminal VSS is grounded, a fifth terminal LO is electrically connected with the grid electrode of the MOS tube TR3, a sixth terminal HB is electrically connected with the first terminal of the bootstrap capacitor C21, a seventh terminal HS is electrically connected with the second terminal of the C21 and is simultaneously electrically connected with the source electrode of the main switching tube TR1, an eighth terminal HO is electrically connected with the grid electrode of the main switching tube TR1, the drain electrode of the MOS tube TR3 is electrically connected with the seventh terminal HS of the U2, and the source electrode of the TR3 is electrically connected with GND; the main function of the MOS transistor TR3 is mainly to provide a charging loop for the bootstrap capacitor C21 of the driving circuit, so as to ensure the normal operation of the bootstrap circuit. The TR3 in this embodiment is implemented by a small current control MOS transistor, and the main power current mainly freewheels from D2.
The above is only a preferred embodiment of the present invention, it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and it will be obvious to those skilled in the art that different power supplies or controls can be added to the circuit of the present invention to obtain similar beneficial effects.

Claims (7)

1. The utility model provides a BUCK control circuit, including the control unit and main power unit, the control unit, including control IC and electric capacity C11, the main power unit, for BUCK synchronous rectification circuit, including main switch TR1, rectifier tube and inductance L1, the rectifier tube adopts synchronous rectifier tube TR2, main switch TR 1's drain electrode electricity coupling power input Vin, the drain electrode of main switch TR 1's source electric connection synchronous rectifier tube TR2 is simultaneously electrically coupled to the first terminal of inductance L1, synchronous rectifier tube TR 2's source ground connection, inductance L1's second terminal is drawn forth and is BUCK circuit output, its characterized in that: further comprising a power supply unit and a drive unit comprising a drive IC and a capacitor C21, wherein,
a power supply unit converting an input voltage into a lower direct current voltage suitable for a conventional control IC to supply power, an input end of the power supply unit being electrically coupled to a power input end Vin, an output end of the power supply unit being electrically coupled to a first terminal Vin of the control IC in the control unit and simultaneously being electrically coupled to a first terminal VDD of the drive IC in the drive unit;
the control unit is used for generating a control signal without direct current bias, the control signal can be directly input to an input end of the drive IC, a first terminal VIN of the control IC is electrically connected with an output end of the power supply unit, a second terminal GND of the control IC is grounded, a third terminal BST of the control IC is electrically connected with a first terminal of the capacitor C11, a fourth terminal SW of the control IC is electrically connected with a second terminal of the capacitor C11 and is also electrically connected with the second terminal GND, and the control IC converts the control signal of the floating ground into a control signal without the floating ground;
the driving unit is used for converting a non-floating ground control signal generated by the control unit into a driving voltage signal capable of directly controlling the MOS tube switch, a first terminal VDD of the isolation driving IC is electrically connected with an output end of the power supply circuit, a second terminal HI is electrically connected with a sixth terminal TG of the control IC, a third terminal LI is electrically connected with a fifth terminal BG of the control IC, a fourth terminal VSS is grounded, a fifth terminal LO is electrically connected with a grid electrode of a synchronous rectifier tube TR2, a sixth terminal HB is electrically connected with a first terminal of a capacitor C21, a seventh terminal HS is electrically connected with a second terminal of the C21 and is simultaneously electrically connected with a source electrode of a main switch tube TR1, an eighth terminal HO is electrically connected with the grid electrode of the main switch tube TR1, and the driving IC converts the non-floating ground control signal generated by the control unit into a floating ground control signal.
2. The BUCK control circuit of claim 1, wherein: the power supply unit comprises a resistor R1, a voltage regulator tube D1, an NPN triode Q1 and a capacitor C1, wherein a first terminal of the resistor R1 is electrically coupled to a power input end Vin, a second terminal of the resistor R1 is electrically coupled to a base electrode of the triode Q1 and a cathode of the voltage regulator tube D1, an anode of the voltage regulator tube D1 is grounded, a collector of the triode Q1 is electrically connected to the power input end Vin, an emitter of the triode Q1 is electrically coupled to a first terminal of the capacitor C1 and serves as an output end of the power supply unit, the first terminal VIN of the control IC and a first terminal VDD of the driving ICU2 are electrically coupled, and a second terminal of the capacitor C1 is grounded.
3. The BUCK control circuit according to claim 1 or 2, wherein: the rectifying tube of the main power unit is a diode D2, the source electrode of the switching tube TR1 is electrically connected with the cathode of a diode D2 and is also electrically connected with the first terminal of an inductor L1, and the anode of a diode D2 is grounded; the driving unit further comprises a MOS tube TR3, a fifth terminal LO of the driving IC is electrically connected with a grid electrode of the MOS tube TR3, a drain electrode of the MOS tube TR3 is electrically connected with a seventh terminal HS of the driving IC U2, and a source electrode of the MOS tube TR3 is grounded.
4. A BUCK control circuit comprises a control unit, a driving unit and a main power unit, wherein the control unit comprises a control IC and a capacitor C11 connected between an SW end and a BST end of the control IC, the main power unit comprises a switch tube TR1, an inductor L1 and a rectifying tube, the rectifying tube adopts a synchronous rectifying tube TR2, a drain electrode of the switch tube TR1 is connected with a power input end Vin, a source electrode of the switch tube TR1 is respectively connected with a drain electrode of the synchronous rectifying tube TR2 and a first end of the inductor L1, a source electrode of the synchronous rectifying tube TR2 is grounded, a second end of the inductor L1 is led out to be a power output end, and the BUCK control circuit is characterized by further comprising a power supply unit for converting input voltage into lower direct-current voltage suitable for supplying power to the conventional control IC,
the driving unit includes a driving IC and a capacitor C21 connected between a seventh terminal HS and a sixth terminal HB of the driving IC;
the input end of the power supply unit is connected with the power input end Vin, and the output end of the power supply unit is respectively connected with the first terminal VIN of the control IC and the first terminal VDD of the drive IC;
the fourth terminal SW and the second terminal GND of the control IC are grounded, the fifth terminal BG of the control IC is connected with the third terminal LI of the drive IC, the sixth terminal TG of the control IC is connected with the second terminal HI of the drive IC, and the control IC converts the control signal of the floating ground into a control signal of the non-floating ground;
the fourth terminal VSS of the driving IC is grounded, the fifth terminal LO of the driving IC is connected with the gate of the synchronous rectifier TR2, the seventh terminal HS of the driving IC is also connected with the source of the switch TR1, the eighth terminal HO of the driving IC is connected with the gate of the switch TR1, and the driving IC converts the non-floating control signal generated by the control unit into a floating control signal.
5. The BUCK control circuit of claim 4, wherein: the power supply unit comprises a resistor R1, a voltage regulator tube D1, an NPN triode Q1 and a capacitor C1, wherein a first terminal of the resistor R1 is electrically coupled to a power input end Vin, a second terminal of the resistor R1 is electrically coupled with a base electrode of the triode Q1 and is also electrically coupled to a cathode of the voltage regulator tube D1, an anode of the voltage regulator tube D1 is grounded, a collector of the triode Q1 is electrically connected to the power input end Vin, an emitter of the triode Q1 is electrically coupled with a first terminal of the capacitor C1 and serves as an output end of the power supply unit, the first terminal VIN of the control IC and a first terminal VDD of the driving ICU2 are both electrically coupled, and a second terminal of the capacitor C1 is grounded.
6. The BUCK control circuit according to claim 4 or 5, wherein: a rectifying tube of the main power unit adopts a diode D2, the cathode of a diode D2 is connected with the source of a switching tube TR1, and the anode of a diode D2 is grounded; the driving unit further comprises a MOS tube TR3, the gate of the MOS tube TR3 is connected with the LO end of the driving IC, the drain of the MOS tube TR3 is connected with the source of the switching tube TR1, and the source of the MOS tube TR3 is grounded.
7. A control method of a BUCK circuit comprises the following steps:
an input voltage conversion step, wherein the input voltage is converted into a lower first direct current voltage suitable for the power supply of a conventional control IC through a power supply unit and is output to a power supply end of a control unit;
a step of converting a non-floating signal to a floating signal, wherein a first direct current voltage is respectively connected to power supply ends of a control IC and a drive IC, an SW end of the control IC is grounded, and the control IC generates a control signal which is directly connected to the drive IC so as to generate a first control signal of the non-floating through the control IC and directly provide the first control signal to the drive IC; the VSS end of the driving IC is grounded, the HO end of the driving IC outputs a second control signal of floating ground, so that the first control signal which is not floating ground and is generated by the control unit is converted into the second control signal of floating ground through the driving IC, and the driving voltage signal for the grid electrode of the switching tube is directly output.
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