CN110391736A - The control circuit of BUCK converter - Google Patents
The control circuit of BUCK converter Download PDFInfo
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- CN110391736A CN110391736A CN201910659739.6A CN201910659739A CN110391736A CN 110391736 A CN110391736 A CN 110391736A CN 201910659739 A CN201910659739 A CN 201910659739A CN 110391736 A CN110391736 A CN 110391736A
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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
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The present invention provides a kind of control circuit of BUCK converter, which includes: voltage comparator circuit and on-off control circuit, and voltage comparator circuit will test voltage and be compared with predeterminated voltage, and comparison result is exported to on-off control circuit.Wherein, the junction capacity voltage of the second switch Q2 of BUCK converter can be charged to the input voltage more than or equal to BUCK converter by the current value of predeterminated voltage.When detecting voltage more than or equal to predeterminated voltage, on-off control circuit controls second switch Q2 shutdown, and inductance L electric current continues to charge to Q2 junction capacity, and Q2 junction capacity voltage is finally made to be equal to the size of input voltage vin.When Q2 junction capacity voltage is equal to input voltage vin, the drain-source voltage of Q1 is zero, and the next cycle for just reaching Q1 at this time is opened the moment, and the tube voltage drop of Q1 is zero, realize zero point press off it is logical reduce turn-on consumption, improve the efficiency of BUCK converter.
Description
Technical field
The present invention relates to switch power technology field more particularly to a kind of control circuits of BUCK converter.
Background technique
Switching mode DC/DC (Direct current-Direct current, abbreviation DC-DC) converter is because of tool
Have the advantages that export burning voltage and high-efficient, be applied more and more widely in fields such as computer, automation or electronic instruments.
BUCK converter is a kind of common DC-DC converter, and BUCK converter is also referred to as buck converter.
Fig. 1 is a kind of schematic diagram of BUCK converter, as shown in Figure 1, the BUCK converter includes first switch tube Q1, the
Two switching tube Q2, inductance L, first capacitor C1 and control circuit.Control circuit is to driving switch pipe Q1 and Q2 with complementary type
Alternate conduction.When Q1 closure Q2 is disconnected, input voltage charges to first capacitor C1 by inductance L；When Q1, which disconnects Q2, to be opened,
Due to the presence of inductance L, so that the electric current of inductance L can maintain in a short time, but gradually become smaller.When Q1 closure, when this
When load current and capacitance current all by inductance L electric current provide；When Q1 is disconnected, load current is the electric current and electricity of inductance L
The sum of capacitance current.
BUCK converter is under light-load mode, it may appear that inductance L electric current, inductance L electric current can be Q2 pairs by second switch
Ground electric discharge causes kwh loss；First switch tube Q1 tube voltage drop in opening process is to be gradually reduced, and load current is gradually increased
, in the process, the voltage and current of switching tube has a crossover region, can produce surplus energy loss.It is whole when underloading
The switching loss of stream switching tube can account for a big chunk of current electric quantity, cause light-load efficiency low.
Summary of the invention
In view of the above problems, the present invention provides a kind of control circuit of BUCK converter, can not only reduce BUCK decompression
The turn-on consumption of first switch tube Q1, can also reduce inductance L electric current when second switch Q2 is opened and discharge over the ground when circuit works
Caused by energy loss.
First aspect present invention provides a kind of BUCK converter control circuit, and the BUCK converter includes first switch tube
Q1, second switch Q2, inductance L and first capacitor C1, the control circuit include: voltage comparator circuit and on-off control electricity
Road；
The voltage comparator circuit will test voltage and be compared with predeterminated voltage, and comparison result is exported to the on-off
Control circuit；The junction capacity voltage of second switch Q2 can be charged to by the inductance L current value that the predeterminated voltage generates to be greater than
Or the input voltage equal to BUCK converter；
The on-off control circuit acquire the second switch Q2 gate drive signal and the first switch tube
The gate drive signal of Q1, when the first switch tube Q1 gate drive signal be low level, the second switch Q2's
Gate drive signal is high level, and the comparison result is that the detection voltage is positive, and the detection voltage is greater than or waits
When the predeterminated voltage, the second switch Q2 shutdown is controlled.
Optionally, the on-off control circuit includes: and door, NOT gate and pulsewidth modulation (Pulse-Width
Modulation, abbreviation PWM) control circuit.
Optionally, the output end of the voltage comparator circuit is connect with described with the first input end of door；
Optionally, the input terminal of the NOT gate is connect with the grid of the first switch tube Q1, the output end of the NOT gate
It is connect with described with the second input terminal of door；
Optionally, described to be connect with the third input terminal of door with the grid of the second switch Q2；
Optionally, described to be connect with the output end of door with the pwm control circuit, when the grid of the first switch tube Q1
Driving signal is low level, and the gate drive signal of the second switch Q2 is high level, the voltage comparator circuit it is defeated
When outlet is high level, the output end with door is high level；
Optionally, the input terminal of the pwm control circuit is connect with described with the output end of door, the pwm control circuit
Output end connect respectively with the first switch tube Q1 grid and the second switch Q2 grid；
Optionally, when the output end with door is high level, the pwm control circuit controls the second switch
Q2 shutdown.
Optionally, voltage comparator circuit includes voltage comparator；The first input end of the voltage comparator inputs detection
Voltage, the second input terminal of the voltage comparator input predeterminated voltage, and the output end and on-off of the voltage comparator control
Circuit connection.
Optionally, the control circuit further include: equivalent detection circuit；The first end of the equivalent detection circuit with it is described
The drain electrode of second switch Q2 connects, and the second end of the equivalent detection circuit is connect with the input terminal of the first capacitor C1.
Optionally, the equivalent detection circuit includes first resistor R1, second resistance R2 and the second capacitor C2；
Optionally, the first resistor R1 is connected between the inductance L and the first capacitor C1；
Optionally, after the second resistance R2 connects with the first capacitor C1, it is connected in parallel on the inductance L and described first
The both ends resistance R1, the first input end of the voltage comparator circuit are connected in parallel on the both ends of the second capacitor C2, wherein described
The voltage of two capacitor C2 is equivalent to the voltage of the inductance L.
Optionally, the voltage-to-ground for the drain electrode that the detection voltage is second switch Q2.
Optionally, the detection voltage is the voltage at the both ends the second capacitor C2.
Optionally, the first switch tube Q1 and second switch Q2 is N-channel MOS field
Effect crystal metal-oxide-semiconductor.
Second aspect of the present invention provides a kind of BUCK inverter control method, and the BUCK converter includes first switch tube
Q1, second switch Q2, inductance L and first capacitor C1, the control method include:
Receiving the voltage comparator circuit will test the comparison result exported after voltage is compared with predeterminated voltage,
In, the junction capacity voltage of second switch Q2 can be charged to by the inductance L current value that the predeterminated voltage generates to be greater than or waits
In the input voltage of BUCK converter；
Acquire the gate drive signal of the second switch Q2 and the gate drive signal of the first switch tube Q1；
When the gate drive signal of the first switch tube Q1 is low level, the gate driving of the second switch Q2 is believed
Number be high level, and the comparison result be the detection voltage be positive, and the detection voltage more than or equal to it is described preset
When voltage, the second switch Q2 shutdown is controlled.
The control circuit of BUCK converter provided by the invention, including BUCK converter and control circuit.The control circuit
It include: voltage comparator circuit and on-off control circuit, voltage comparator circuit will test voltage and be compared with predeterminated voltage, will compare
Relatively result is exported to on-off control circuit.The current value of predeterminated voltage can be by the knot electricity of the second switch Q2 of BUCK converter
Hold voltage and is charged to the input voltage more than or equal to BUCK converter.On-off control circuit acquires the second switch Q2's
The gate drive signal of gate drive signal and the first switch tube Q1, when the gate driving of the first switch tube Q1 is believed
It number is low level, the gate drive signal of the second switch Q2 is high level, and the comparison result is that the detection is electric
Pressure is positive, and when the detection voltage is greater than or equal to the predeterminated voltage, controls second switch Q2 shutdown.The control
After circuit turns off Q2, inductance L electric current continues to charge to Q2 junction capacity, and Q2 junction capacity voltage is finally made to be equal to input voltage
The size of Vin.When Q2 junction capacity voltage is equal to input voltage vin, the drain-source voltage of Q1 is zero, is just reached under Q1 at this time
A cycle is opened the moment, and the tube voltage drop of Q1 is zero, realize zero point press off it is logical reduce turn-on consumption, improve BUCK change
The efficiency of parallel operation.
Detailed description of the invention
To describe the technical solutions in the embodiments of the present invention more clearly, make required in being described below to embodiment
Attached drawing is briefly introduced, it should be apparent that, drawings in the following description are only some embodiments of the invention, for this
For the those of ordinary skill in field, without any creative labor, it can also be obtained according to these attached drawings
His attached drawing.
Fig. 1 is a kind of structural schematic diagram of BUCK converter；
Fig. 2 is that BUCK converter inductance L current diagram occurs under the conditions of underloading；
Fig. 3 is energy loss schematic diagram when BUCK converter first switch tube Q1 is opened；
Fig. 4 is the control circuit structural representation for the BUCK converter that the embodiment of the present invention one provides；
Fig. 5 is the control circuit structural representation of BUCK converter provided by Embodiment 2 of the present invention；
Fig. 6 is the control circuit structural representation for the BUCK converter that the embodiment of the present invention three provides；
Fig. 7 is that BUCK converter takes the current waveform figure of inductance L and first switch tube Q1 leakage after control circuit of the present invention
The waveform diagram of source voltage.
Through the above attached drawings, it has been shown that the specific embodiment of the present invention will be hereinafter described in more detail.These attached drawings
It is not intended to limit the scope of the inventive concept in any manner with verbal description, but is by referring to specific embodiments
Those skilled in the art illustrate idea of the invention.
Specific embodiment
Example embodiments are described in detail here, and the example is illustrated in the accompanying drawings.Following description is related to
When attached drawing, unless otherwise indicated, the same numbers in different drawings indicate the same or similar elements.Following exemplary embodiment
Described in embodiment do not represent all embodiments consistented with the present invention.On the contrary, they be only with it is such as appended
The example of device and method being described in detail in claims, some aspects of the invention are consistent.
The present invention provides a kind of control circuit of BUCK converter, which has the function of decompression conversion in the same direction
Can, i.e., input voltage is identical with the polarity of output voltage, and output voltage is theoretically smaller than or is equal to input voltage.
Fig. 1 be BUCK converter a kind of structural schematic diagram, as shown in Figure 1, BUCK converter include first switch tube Q1,
Second switch Q2, inductance L, first capacitor C1 and pwm control circuit.First switch tube Q1, second switch Q2 and inductance L and
Main topology is collectively formed in first capacitor C1.
Specifically, the drain electrode of the source electrode, Q2 of switching tube Q1 is connected with the first end of inductance L；Q1 drain electrode access input voltage
Vin, Q2 source electrode ground connection；The second end of inductance L is connected with the first end of first capacitor C1, the second end and load of first capacitor C1
It is connected.
The load can be output voltage or load resistance R, and first switch tube Q1 is N-channel metal-oxide semiconductor (MOS)
Field effect transistor metal-oxide-semiconductor (n-channel Metal-Oxide-Semiconductor Field-Effect Transistor,
Abbreviation NMOSFET), second switch Q2 is NMOSFET power switch tube.
Input direct-current voltage is modulated into a system for being modulated to the pulse width of driving signal by pwm control circuit
Column pulse changes the duty ratio of pulse to obtain required output voltage.Pwm control circuit controls first switch in BUCK circuit
The turn-on time of pipe Q1 and second switch Q2 control duty ratio modulation output voltage size.
The grid impulse control signal of first switch tube Q1 and the grid impulse control signal of second switch Q2 are controlled by PWM
Circuit processed provides, and when first switch tube Q1 conducting second switch Q2 shutdown, the electric current of inductance L is gradually increased, first capacitor
C1 charging；When first switch tube Q1 shutdown second switch Q2 conducting, since the electric current of inductance L cannot be mutated, in inductance L two
End generates self-induced e.m.f, continues to discharge by the continuous current circuit that second switch Q2 is formed, and the electric current of inductance L is gradually reduced, the
One capacitor C1 electric discharge.Change the duty ratio of first switch tube Q1 and second switch Q2, control output electricity by adjusting pwm signal
The size of pressure.
Fig. 2 is that BUCK converter the schematic diagram of inductance L electric current, as shown in Figure 1, first switch tube occurs under the conditions of underloading
The grid impulse control signal of Q1 and the grid impulse control signal of second switch Q2 are controlled by pwm control circuit.
First switch tube Q1 is connected in service time, second switch Q2 shutdown；First switch tube Q1 is closed in turn-off time
It is disconnected, second switch Q2 conducting.Input voltage vin charges to inductance L during first switch tube Q1 is opened, the electric current of inductance L
Linear rise reaches peak current in the electric current for opening finish time inductance L；First switch tube Q1 shutdown second switch Q2 is opened
After logical, the current direction of inductance L cannot be mutated, and the electric current forward direction of inductance L is gradually reduced, and drop to trough electricity in shutdown finish time
Stream.
Since semiconductor field effect transistor can be connected in either direction, so working as light load or being reduced to zero
When, second switch Q2 shutdown, the electric current of inductance L will not be mutated, and the electric current of inductance L can gradually decrease to zero and inductance L electricity occurs
Stream drops to trough electric current in shutdown finish time.Inductance L electric current can be discharged over the ground by second switch Q2 causes energy to damage
Consumption.The waveform diagram of the electric current of inductance L indicates that under the conditions of underloading, the trough electric current for turning off the inductance L of finish time just declines
To zero；When load is zero, in second switch Q2 opening process, the electric current of inductance L is reversely gradually increased after gradually decreasing to zero,
Inductance L electric current is discharged over the ground by second switch Q2, reaches maximum value in shutdown finish time inductance L electric current.
Fig. 3 is energy loss schematic diagram when the first switch tube Q1 of BUCK converter is opened.As shown in figure 3, first switch
Pressure drop between the gate source voltage expression transistor gate and source electrode of pipe Q1, cut-in voltage when threshold voltage is transistor turns,
Pressure drop of the drain-source voltage between transistor drain and source electrode.The opening process of first switch tube Q1 are as follows: when the T1 time starts, In
Gate source voltage from zero be raised to threshold voltage during, first switch tube Q1 is in cut-off region off state, first switch tube Q1's
Electric current has the electric current of very little to flow through；The electric current of first switch tube Q1 rises to load maximum current in the T2 time, and drain-source voltage is opened
Begin to decline, gate source voltage increases to threshold voltage；Gate source voltage remains unchanged in the T3 time, and the electric current of first switch tube Q1 is still
For maximum load current, drain-source voltage declines quickly；Drain-source voltage continues to decline in the T4 time, it is finally stable drain-source voltage=
Switch tube current * transistor resistance.
From the point of view of the opening process of entire first switch tube Q1, the T2 time interior electric current with first switch tube Q1 in the T3 time
It is gradually increased to load current from zero, drain-source voltage gradually decreases to first switch tube Q1 static state tube voltage drop size, in this process
In can generate turn-on consumption, therefore turn-on consumption is (drain-source voltage * switchs tube current/2) * (T2+T3).When loading smaller,
The accounting of first switch tube Q1 oneself power consumption will be bigger, and efficiency will be lower.
BUCK converter control circuit provided by the invention, it is intended to solve the technical problem as above of the prior art.
How to be solved with technical solution of the specifically embodiment to technical solution of the present invention and the application below above-mentioned
Technical problem is described in detail.These specific embodiments can be combined with each other below, for the same or similar concept
Or process may repeat no more in certain embodiments.Below in conjunction with attached drawing, the embodiment of the present invention is described.
Fig. 4 is the structural schematic diagram for the BUCK converter control circuit that the embodiment of the present invention one provides., the control circuit packet
Include voltage comparator circuit and on-off control circuit.
Voltage comparator circuit will test voltage and be compared with predeterminated voltage, and comparison result is exported and controls electricity to on-off
Road；The junction capacity voltage of second switch Q2 can be charged to by the inductance L current value that predeterminated voltage generates to be more than or equal to
The input voltage inductance of BUCK converter.
On-off control circuit acquires the gate drive signal and the first switch tube Q1 of the second switch Q2
Gate drive signal, when the gate drive signal of the first switch tube Q1 is low level, the grid of the second switch Q2
Driving signal is high level, and the comparison result is that the detection voltage is positive, and the detection voltage is greater than or equal to institute
When stating predeterminated voltage, the second switch Q2 shutdown is controlled.After controlling second switch Q2 shutdown, inductance L electric current continues
It charges to Q2 junction capacity, Q2 junction capacity voltage is finally made to be equal to the size of input voltage.When Q2 junction capacity voltage is equal to input electricity
When pressure, the drain-source voltage of first switch tube Q1 is zero, just reaches next cycle Q1 at this time and opens the moment, the pipe of switching tube Q1
Pressure drop is zero.
The control circuit of the present embodiment, voltage comparator circuit will test voltage and be compared with predeterminated voltage, on-off control
Circuit acquires the gate drive signal of second switch Q2 and the gate drive signal of first switch tube Q1.When control second is opened
After closing pipe Q2 shutdown, the moment is opened in next cycle Q1, makes the tube voltage drop zero of switching tube Q1, no-voltage is realized and opens drop
Low turn-on consumption, improves the efficiency of BUCK converter.
The structural schematic diagram of Fig. 5 BUCK converter control circuit provided by Embodiment 2 of the present invention.As shown in figure 5, this reality
On the basis of the control circuit control circuit shown in Fig. 4 for applying example offer, which includes: and door, NOT gate and PWM
Control circuit.
Wherein, the first input end of voltage comparator circuit is connect with the drain electrode of second switch Q2, and voltage comparator circuit is adopted
Integrate voltage as the voltage-to-ground of the drain electrode of second switch Q2, the voltage-to-ground of the drain electrode of second switch Q2 also referred to as detects
Voltage, the drain electrode of the source electrode, second switch Q2 of the voltage-to-ground and first switch tube Q1 of the drain electrode of second switch Q2 and electricity
The voltage-to-ground felt at 3 intersections of L is equal.
Second input terminal of voltage comparator circuit and the input terminal of predeterminated voltage connect, the output end ground connection of predeterminated voltage,
The output end of voltage comparator circuit is connect with the first input end with door, and voltage comparator circuit is used for the voltage when first input end
More than or equal to predeterminated voltage voltage when export high level.
The input terminal of NOT gate is connect with the grid of first switch tube Q1, the output end of NOT gate and second input with door
End connection.
It connect with the third input terminal of door with the grid of the second switch Q2, is controlled with the output end of door and the PWM
Circuit connection processed, when the gate drive signal of the first switch tube Q1 is low level, the grid of the second switch Q2 is driven
Dynamic signal is high level, and when the output end of the voltage comparator circuit is high level, the output end with door is high level.
The input terminal of the pwm control circuit is connect with described with the output end of door, the output end of the pwm control circuit
It is connect respectively with the first switch tube Q1 grid and the second switch Q2 grid.
When the output end with door is high level, the pwm control circuit controls the second switch Q2 shutdown.
Optionally, voltage comparator circuit is comparator.
In first switch tube Q1 shutdown, second switch Q2 conducting, if load is particularly lightweight or when not loading, meeting
There is inductance L electric current, with being gradually increased for inductance L electric current, detecting voltage can be also gradually increased；It is preset when detection voltage is greater than
When voltage, voltage comparator circuit exports high level signal, while when the gate drive signal of first switch tube Q1 is low level, the
The gate drive signal of two switching tube Q2 is high level, i.e., when first switch tube Q1 shutdown, second switch Q2 conducting, with door
Output signal is high level signal；Pwm control circuit receives output control signal shutdown after the high level signal sent with door
Second switch Q2, the stopping of inductance L electric current are discharged over the ground, reduce kwh loss.After second switch Q2 shutdown, inductance L electric current
Continue to the junction capacity charging of second switch Q2, when so that the junction capacity voltage of second switch Q2 being charged to input voltage vin,
First switch tube Q1 drain-source tube voltage drop is zero.At this time just into next cycle, reach first switch tube Q1 opens the moment,
It realizes that first switch tube Q1 no-voltage is open-minded, reduces turn-on consumption.
The structural schematic diagram for the BUCK converter control circuit that Fig. 6 embodiment of the present invention three provides.Such as
Shown in Fig. 6, which includes voltage comparator circuit, equivalent detection circuit and on-off control circuit.Voltage ratio
It compared with circuit, is compared for will test voltage with the voltage of predeterminated voltage, comparison result is exported to on-off control circuit, it should
The voltage that voltage is the inductance L detected by equivalent detection circuit is detected, wherein predeterminated voltage is that voltage comparator is reversely defeated
Enter a reference value at end, i.e. the junction capacity voltage of the second switch Q2 can be charged to and be more than or equal to by inductance L current value
The input voltage vin of BUCK converter.
Wherein, the first end of equivalent detection circuit is connect with the drain electrode of second switch Q2, and the second of equivalent detection circuit
End is connect with the input terminal of first capacitor C1.The first input end of voltage comparator circuit be connected in parallel on the both ends of equivalent detection circuit with
The drain electrode of second switch Q2 connects, and the voltage at equivalent detection circuit both ends is the voltage of inductance L.The first of voltage comparator circuit
Second input terminal of input terminal, voltage comparator circuit is connect with predeterminated voltage, the output end of voltage comparator circuit and the with door
The connection of one input terminal, voltage comparator circuit are used to export when the voltage of first input end is greater than or equal to the voltage of predeterminated voltage
High level；
The input terminal of NOT gate is connect with the grid of first switch tube Q1, and the output end of NOT gate connects with the second input terminal of door
It connects；
It is connect with the third input terminal of door with the grid of second switch Q2；
It is connect with the output end of door with pwm control circuit, when the gate drive signal of first switch tube Q1 is low level, the
The gate drive signal of two switching tube Q2 is high level, when the output end of voltage comparator circuit is high level, the output end with door
For high level；
The input terminal of pwm control circuit is connect with the output end with door, and the output end of pwm control circuit is opened with first respectively
Pipe Q1 grid is closed to connect with second switch Q2 grid；
When being high level with the output end of door, pwm control circuit controls second switch Q2 shutdown.
It optionally, include resistance first resistor R1, second resistance R2 and the second capacitor C2 in equivalent circuit.First resistor R1
It is connected between inductance L and first capacitor C1, after second resistance R2 connects with first capacitor C1, is connected in parallel on the electricity of inductance L and first
The both ends R1 are hindered, the first input end of voltage comparator circuit is connected in parallel on the both ends of the second capacitor C2, wherein the voltage of the second capacitor C2
It is equivalent to the voltage of inductance L.
The type selecting of first resistor R1 and the second capacitor C2 follow L/R2=R1*C2, itself electricity that second resistance R2 is inductance L
It hinders, then inductance L voltage=inductance L electric current * second resistance R2=the second capacitor C2 voltage, the i.e. size etc. of the second capacitor C2 voltage
In inductance L both end voltage.
When the output end with door is high level, the pwm control circuit controls the second switch Q2 shutdown.
Optionally, voltage comparator circuit is comparator.
In first switch tube Q1 shutdown, second switch Q2 conducting, if load is particularly lightweight or when not loading, meeting
There is inductance L electric current, with being gradually increased for inductance L electric current, the second capacitor C2 voltage can be also gradually increased in equivalent circuit；When
When the voltage of the second capacitor C2 detected is greater than predeterminated voltage, voltage comparator exports high level signal, while first switch
The gate drive signal of pipe Q1 be low level, second switch Q1 gate drive signal be the i.e. first switch tube Q1 of high level close
It is high level signal with door output signal when disconnected, second switch Q2 is connected；After pwm control circuit receives high level signal
Output control signal turns off second switch Q2, and the stopping of inductance L electric current is discharged over the ground, reduces kwh loss.Second switch Q2
After shutdown, inductance L electric current continues to the junction capacity charging of second switch Q2, so that the junction capacity voltage of second switch Q2 fills
To when being equal to input voltage vin, first switch tube Q1 drain-source tube voltage drop is zero.The open-minded of first switch tube Q1 is just reached at this time
Moment realizes that first switch tube Q1 no-voltage is open-minded, reduces turn-on consumption.
BUCK converter shown in Fig. 7 takes the current waveform figure and first switch tube Q1 of inductance L after control circuit of the present invention
The waveform diagram of drain-source voltage.First switch tube Q1 gate drive signal and second switch Q2 gate drive signal difference in Fig. 7
The conducting situation for controlling first switch tube Q1 and second switch Q2, under the conditions of underloading, when control circuit of the present invention is not used,
Inductance L electric current will appear inductance L electric current, and in the finish time that second switch is opened, inductance L electric current reaches maximum value trough electricity
Stream.
After control circuit of the invention, such as in Fig. 5 circuit, when detection voltage is greater than, on-off control circuit is defeated
Signal turns off second switch Q2 out, and inductance L electric current continues to be charged to second switch Q2 junction capacity equal to input voltage
Vin.Similarly, in Fig. 6 circuit, when the second capacitor C2 voltage is greater than predeterminated voltage in equivalent circuit, on-off control circuit output
Signal turns off second switch Q2, and inductance L electric current continues to be charged to Q2 junction capacity equal to input voltage vin.Ideal control strip
Under part, when Q2 junction capacity voltage is equal to input voltage vin, right up to first switch tube Q1's is opened the moment, and at this time first
The tube voltage drop of switching tube Q1 is zero.First switch tube Q1 is opened under no-voltage, it can be achieved that no-voltage is open-minded, is reduced and is opened damage
Consumption.
Before not using the technology of the present invention, it can be seen that under the conditions of underloading, inductance L negative current is bigger, inductance L electricity
Energy loss caused by stream trough electric current discharges over the ground is larger；By using the on-off control circuit designed in Fig. 5 or Fig. 6,
It may be implemented to reduce the kwh loss and reduce first switch tube Q1 turn-on consumption that inductance L electric current discharges over the ground.
The control circuit of BUCK converter provided by the invention in summary, by detecting second switch Q2 drain voltage
Or the size of the second capacitor C2 voltage and first switch tube Q1 gate drive signal and second switch Q2 in equivalent circuit
Gate drive signal, design NOT gate, voltage comparator, the logic control circuit formed with door and pwm control circuit, reduces light
Kwh loss caused by inductance L electric current discharges over the ground under the conditions of load.Inductance L electric current continues after first switch tube Q2 shutdown to the
When the junction capacity of two switching tube Q2 is charged to equal to input voltage vin, the tube voltage drop of first switch tube Q1 is zero, under reaching at this time
It is logical to realize that first switch tube Q1 zero point presses off, reduces turn-on consumption for a cycle.
Those skilled in the art after considering the specification and implementing the invention disclosed here, will readily occur to of the invention its
Its embodiment.The present invention is directed to cover any variations, uses, or adaptations of the invention, these modifications, purposes or
Person's adaptive change follows general principle of the invention and including the undocumented common knowledge in the art of the present invention
Or conventional techniques.The description and examples are only to be considered as illustrative, and true scope and spirit of the invention are by following
Claims are pointed out.
It should be understood that the present invention is not limited to the precise structure already described above and shown in the accompanying drawings, and
And various modifications and changes may be made without departing from the scope thereof.The scope of the present invention is only limited by appended claims
System.
Claims (9)
1. a kind of control circuit of BUCK converter, the BUCK converter includes first switch tube Q1, second switch Q2, electricity
Feel L and first capacitor C1, which is characterized in that the control circuit includes: voltage comparator circuit and on-off control circuit；
The voltage comparator circuit will test voltage and be compared with predeterminated voltage, and comparison result is exported and is controlled to the on-off
Circuit；The inductance L current value that the predeterminated voltage generates the junction capacity voltage of second switch Q2 can be charged to be greater than or
Equal to the input voltage of BUCK converter；
The on-off control circuit acquires the gate drive signal and the first switch tube Q1 of the second switch Q2
Gate drive signal, when the gate drive signal of the first switch tube Q1 is low level, the grid of the second switch Q2
Driving signal is high level, and the comparison result is that the detection voltage is positive, and the detection voltage is greater than or equal to institute
When stating predeterminated voltage, the second switch Q2 shutdown is controlled.
2. circuit according to claim 1, which is characterized in that the on-off control circuit include: with door, NOT gate and pulsewidth
Modulation (PWM) control circuit；
The output end of the voltage comparator circuit is connect with described with the first input end of door；
The input terminal of the NOT gate is connect with the grid of the first switch tube Q1, the output end of the NOT gate and described with door
The connection of second input terminal；
It is described to be connect with the third input terminal of door with the grid of the second switch Q2；
It is described to be connect with the output end of door with the pwm control circuit, when the gate drive signal of the first switch tube Q1 is
Low level, the gate drive signal of the second switch Q2 are high level, and the output end of the voltage comparator circuit is high electricity
Usually, the output end with door is high level；
The input terminal of the pwm control circuit is connect with described with the output end of door, the output end difference of the pwm control circuit
It is connect with the first switch tube Q1 grid and the second switch Q2 grid；
When the output end with door is high level, the pwm control circuit controls the second switch Q2 shutdown.
3. circuit according to claim 1, which is characterized in that the voltage comparator circuit includes: voltage comparator；
The first input end input detection voltage of the voltage comparator, the second input terminal input of the voltage comparator are default
The output end of voltage, the voltage comparator is connect with on-off control circuit.
4. circuit according to claim 3, which is characterized in that the control circuit further include: equivalent detection circuit；
The first end of the equivalent detection circuit is connect with the drain electrode of the second switch Q2, and the of the equivalent detection circuit
Two ends are connect with the input terminal of the first capacitor C1.
5. circuit according to claim 4, which is characterized in that the equivalent detection circuit includes first resistor R1, second
Resistance R2 and the second capacitor C2；
The first resistor R1 is connected between the inductance L and the first capacitor C1；
After the second resistance R2 connects with the first capacitor C1, it is connected in parallel on the inductance L and the both ends the first resistor R1,
The first input end of the voltage comparator circuit is connected in parallel on the both ends of the second capacitor C2, wherein the second capacitor C2's
Voltage is equivalent to the voltage of the inductance L.
6. circuit according to claim 3, which is characterized in that pair for the drain electrode that the detection voltage is second switch Q2
Ground voltage.
7. circuit according to claim 4, which is characterized in that the detection voltage is the electricity at the both ends the second capacitor C2
Pressure.
8. circuit according to claim 1-6, which is characterized in that the first switch tube Q1 and described second is opened
Closing pipe Q2 is N-channel metal oxide semiconductor field effect transistor metal-oxide-semiconductor.
9. a kind of control method of BUCK converter control circuit, the BUCK converter includes first switch tube Q1, second opens
Close pipe Q2, inductance L and first capacitor C1, which is characterized in that the control method includes:
Receiving the voltage comparator circuit will test the comparison result exported after voltage is compared with predeterminated voltage, wherein institute
The junction capacity voltage of second switch Q2 can be charged to more than or equal to BUCK by the inductance L current value for stating predeterminated voltage generation
The input voltage of converter；
Acquire the gate drive signal of the second switch Q2 and the gate drive signal of the first switch tube Q1；
When the gate drive signal of the first switch tube Q1 is low level, the gate drive signal of the second switch Q2 is
High level, and the comparison result is that the detection voltage is positive, and the detection voltage is greater than or equal to the predeterminated voltage
When, control the second switch Q2 shutdown.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910659739.6A CN110391736A (en) | 2019-07-22 | 2019-07-22 | The control circuit of BUCK converter |
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| CN201910659739.6A CN110391736A (en) | 2019-07-22 | 2019-07-22 | The control circuit of BUCK converter |
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| CN201910659739.6A Pending CN110391736A (en) | 2019-07-22 | 2019-07-22 | The control circuit of BUCK converter |
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