CN114977761A - Control circuit for improving load shedding transient response of voltage reduction circuit - Google Patents

Control circuit for improving load shedding transient response of voltage reduction circuit Download PDF

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Publication number
CN114977761A
CN114977761A CN202210726806.3A CN202210726806A CN114977761A CN 114977761 A CN114977761 A CN 114977761A CN 202210726806 A CN202210726806 A CN 202210726806A CN 114977761 A CN114977761 A CN 114977761A
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signal
delay
voltage
conduction
circuit
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CN202210726806.3A
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Chinese (zh)
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吴皓楠
郝军哲
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Junying Semiconductor Shanghai Co ltd
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Junying Semiconductor Shanghai Co ltd
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Priority to CN202210726806.3A priority Critical patent/CN114977761A/en
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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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • 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
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • 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

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

Abstract

The disclosure relates to a control circuit for improving the load shedding transient response of a voltage reduction circuit. The control circuit includes: the upper tube conduction control unit is used for obtaining a delay mode control signal according to the first reference voltage and the feedback voltage of the voltage reduction circuit and obtaining an upper tube conduction signal according to the delay mode control signal and the duty ratio of the voltage reduction circuit so as to control the turn-off time of an upper tube; the lower tube conduction control unit is used for obtaining a lower tube conduction signal according to the feedback voltage, the second reference voltage and the delay mode control signal so as to control the conduction time of the upper tube; and the control signal output unit is connected with the upper tube conduction control unit and the lower tube conduction control unit and is used for controlling the conduction and the cut-off of the upper tube and the lower tube of the voltage reduction circuit according to the upper tube conduction signal and the lower tube conduction signal. By the scheme of the disclosure, transient response of the voltage reduction circuit during load shedding can be improved according to the duty ratio of the voltage reduction circuit.

Description

Control circuit for improving load shedding transient response of voltage reduction circuit
Technical Field
The present disclosure relates generally to the field of power management. More particularly, the present disclosure relates to a control circuit that improves the turn-off transient response of a buck circuit.
Background
With the increasing demand of people on power supplies, the voltage converter is rapidly developed and widely applied to various electronic equipment power supplies, daily lighting power supplies, household appliance power supplies and the like. Among them, the BUCK circuit (voltage-reducing circuit) is one of the most commonly used circuits, and for the BUCK circuit, when the output of the circuit is switched from a light load (e.g., an inductor current of 0A) to a heavy load (e.g., an inductor current of 5A), since the inductor current cannot be increased in time, the average inductor current is smaller than the current required by the load, so that the output voltage is reduced, and the average inductor current takes a longer time to recover, so that the dynamic response is poor.
However, the prior art does not provide good control over the rapid rise back of the inductor current.
Disclosure of Invention
To at least partially solve the technical problems mentioned in the background, the solution of the present disclosure provides a control circuit for improving the off-load transient response of a buck circuit.
The utility model provides a control circuit for improving step-down circuit off-load transient response, step-down circuit includes top tube and low tube, its characterized in that, control circuit includes: the upper tube conduction control unit is used for obtaining a delay mode control signal according to a first reference voltage and the feedback voltage of the voltage reduction circuit and obtaining an upper tube conduction signal according to the delay mode control signal and the duty ratio of the voltage reduction circuit so as to control the turn-off time of the upper tube; the lower tube conduction control unit is connected with the upper tube conduction control unit and used for obtaining a lower tube conduction signal according to the feedback voltage, a second reference voltage and the delay mode control signal so as to control the conduction time of the upper tube; and the control signal output unit is connected with the upper pipe conduction control unit and the lower pipe conduction control unit, is used for receiving the upper pipe conduction signal and the lower pipe conduction signal, and outputs a switch control signal to control the switching-on and switching-off of the upper pipe and the lower pipe of the voltage reduction circuit according to the upper pipe conduction signal and the lower pipe conduction signal.
According to an embodiment of the present disclosure, the upper tube conduction control unit includes a comparator, a delay module and an or gate; wherein a positive phase input terminal of the comparator receives the feedback voltage, a negative phase input terminal of the comparator receives a first reference voltage, and an output terminal of the comparator outputs the delay mode control signal generated according to the feedback voltage and the first reference voltage; the delay module is connected with the output end of the comparator and receives the delay mode control signal, and the delay module selects to enter a normal delay mode or a reduced delay mode according to the delay mode control signal, when the delay module selects to enter the reduced delay mode, a reduced delay signal is obtained according to the duty ratio, and when the delay module selects the normal delay mode, the normal delay signal is obtained according to a first preset delay time; the or gate is connected to the delay module and receives the reduced delay signal and the normal delay signal as inputs, and an output terminal of the or gate outputs the upper tube conducting signal.
According to an embodiment of the present disclosure, the comparator includes a hysteresis comparator.
According to an embodiment of the present disclosure, the first reference voltage includes an upper threshold voltage and a lower threshold voltage, the delay mode control signal is at a high level when the feedback voltage is less than the lower threshold voltage, and the delay mode control signal is at a low level when the feedback voltage is greater than the upper threshold voltage.
According to an embodiment of the present disclosure, when the delay mode control signal is at a low level, the delay module selects to enter the normal delay mode, when the delay mode control signal is at a high level, the delay module selects to enter the reduced delay mode, the reduced delay signal includes a first delay signal and a second delay signal, when the delay module selects to enter the reduced delay mode, if the duty cycle is smaller than a preset value, the first delay signal is obtained according to a second preset delay time, and if the duty cycle is greater than or equal to the preset value, the second delay signal is obtained according to a third preset delay time, where the third preset delay time is smaller than the second preset delay time, and the second preset delay time is smaller than the first preset delay time.
According to the embodiment of the disclosure, the lower tube conduction control unit comprises an error amplifier, a charging module, a reference current generation module and a comparison module; wherein a positive phase input of the error amplifier receives the second reference voltage, a negative phase input of the error amplifier receives the feedback voltage, and an output of the error amplifier outputs a first voltage signal generated from the second reference voltage and the feedback voltage; the charging module is connected with the output end of the comparator of the upper tube conduction control unit and receives the delay mode control signal, and the charging module is connected with the output end of the error amplifier and determines whether to charge the output end of the error amplifier according to the delay mode control signal to form a second voltage signal; the input end of the reference current generation module is connected with the output end of the error amplifier and receives the second voltage signal, and the output end of the reference current generation module outputs a reference current signal generated according to the second voltage signal; the input end of the comparison module is connected with the output end of the reference current generation module and receives the reference current signal, the comparison module receives an inductive current feedback signal of the voltage reduction circuit, and the comparison module obtains a lower tube conduction signal according to the reference current signal and the inductive current feedback signal.
According to an embodiment of the present disclosure, when the delay module control signal corresponds to the reduced delay mode, the charging module charges an output terminal of the error amplifier to form the second voltage signal, and when the delay module control signal corresponds to the normal delay mode, the charging module does not charge the output terminal of the error amplifier, and takes the first voltage signal as the second voltage signal.
According to an embodiment of the present disclosure, the reference current signal is positively correlated with the second voltage signal.
According to the embodiment of the disclosure, when the current value of the inductor current feedback signal is equal to the current value of the reference current signal, the comparison module generates the lower tube conduction signal.
According to the embodiment of the disclosure, the control signal output unit comprises an RS trigger, an S end of the trigger is connected with an output end of an or gate of the upper tube conduction control unit and receives the upper tube conduction signal, an R end of the trigger is connected with an output end of a comparison module of the lower tube conduction control unit and receives the lower tube conduction signal, and a Q end of the trigger outputs the switch control signal.
Through the control circuit for improving the load shedding transient response of the voltage reduction circuit, the delay mode can be reduced by entering, the turn-off time of the upper tube is reduced by utilizing the duty ratio, and the turn-on time is increased, so that the oscillation of the output voltage caused by the overshoot of the current is avoided while the rising of the inductive current is accelerated.
Drawings
The above and other objects, features and advantages of exemplary embodiments of the present disclosure will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar or corresponding parts and in which:
FIG. 1 is a schematic diagram showing an equivalent circuit structure of a BUCK circuit in the prior art;
FIG. 2 is a schematic diagram showing the timing variation of the inductor current and the turn-on signal when the BUCK circuit in the prior art operates in the DCM mode;
FIG. 3 is a schematic diagram showing the timing variation of the inductor current and the turn-on signal when the BUCK circuit in the prior art operates in the CCM mode;
FIG. 4 is a schematic diagram showing a structure of a control circuit for a BUCK circuit in the prior art;
FIG. 5 is a schematic diagram illustrating the structure of a control circuit for improving the off-load transient response of the buck circuit according to one embodiment of the present disclosure;
FIG. 6 is a circuit diagram of a top-tube-conduction control unit of a control circuit for improving the off-load transient response of the buck circuit according to an embodiment of the disclosure;
fig. 7 is a circuit structure diagram illustrating a lower tube conduction control unit of the control circuit for improving the off-load transient response of the buck circuit according to an embodiment of the disclosure;
fig. 8 is a timing diagram illustrating inductor current response under control of a control circuit that improves the turn-off transient response of the buck circuit according to one embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are some, but not all embodiments of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
In order to facilitate understanding of the technical solutions of the present disclosure, embodiments of the prior art are described below with reference to the accompanying drawings.
Fig. 1 is a schematic diagram showing an equivalent circuit structure of a BUCK circuit in the related art. The BUCK circuit, also known as a BUCK converter circuit, is one of the basic DC-DC circuits and is used for DC-to-DC BUCK conversion. As shown in FIG. 1, the BUCK circuit includes an upper tube S for switching on and off modes 1 And a lower pipe S 2 While generating a current I in Power supply V in Inductor L and capacitor C out And a load resistance R out . Along with the upper pipe S 1 And a lower pipe S 2 The two tubes are switched continuously, and the circuit generates an output voltage V out And the inductor current I L . And node SW is also shown in fig. 1.
Fig. 2 is a schematic diagram illustrating the timing variation of the inductor current and the turn-on signal when the BUCK circuit in the prior art operates in the DCM mode. The DCM mode is an intermittent conduction mode. Referring to FIG. 1, as shown in FIG. 2, when the BUCK circuit operates in DCM, the upper tube S 1 And a lower pipe S 2 And discontinuous conduction is realized. Specifically, the upper pipe S 1 The conduction state is firstly entered under the action of an upper tube on-off signal HS, the inductive current IL is gradually increased, and the on-off time TON of the upper tube is endedAt first, the upper pipe S 1 Breaking, lowering the tube S 2 And the inductor is conducted under the action of the lower tube on signal LS, so that the inductive current is gradually reduced. When the inductor current IL is reduced to 0, the tube S is dropped 2 Disconnected but upper pipe S 1 It will not turn on immediately but will wait until the end of the top-tube-off time TOFF to turn on again, causing the inductor current to rise again. Wherein TON is the top tube on time in a switching cycle, and TOFF is the top tube off time in a switching cycle.
Fig. 3 is a schematic diagram showing the timing variation of the inductor current and the turn-on signal when the BUCK circuit in the prior art operates in the CCM mode. The CCM mode refers to a continuous conduction mode. Referring to FIG. 1, as shown in FIG. 3, when the BUCK circuit operates in CCM mode, the upper tube S 1 And a lower pipe S 2 Continuous conduction is realized. Specifically, the upper pipe S 1 The upper tube S is firstly switched into a conducting state under the action of an upper tube switching-on signal HS, the inductive current IL is gradually increased, and the upper tube S is switched on when the upper tube switching-on time TON is over 1 Breaking, lowering the tube S 2 The current is conducted under the action of a lower tube on signal LS, so that the inductive current is gradually reduced, and when the upper tube off time TOFF is over, a lower tube S is arranged 2 Breaking and mounting the pipe S 1 And the upper tube is conducted again under the action of the on signal HS of the upper tube, so that the inductive current is increased again. Wherein TON is the top tube on time in a switching cycle, and TOFF is the top tube off time in a switching cycle.
Fig. 4 is a schematic diagram showing a configuration of a control circuit for a BUCK circuit in the related art. As shown in FIG. 4, the control circuit is used to control the switching on and off of the upper and lower tubes. In particular, the error amplifier may be based on a reference voltage V REF And an error of a feedback voltage FB fed back from an output terminal of the BUCK circuit via the voltage feedback circuit to output a voltage EAO. The voltage EAO positively affects the reference current I REF The reference current and the inductive current I obtained by sampling through the current feedback circuit L And comparing, when the reference current is equal to the inductive current, generating a square wave signal, and forming a switch control signal PWM for controlling the upper tube and the lower tube to be conducted in turn through the square wave signal so as to control the BUCK circuit. Wherein the switchThe circuit includes a BUCK circuit.
With this control circuit, when the BUCK circuit output is switched from a light load (e.g., IL-0A) to a heavy load (e.g., IL-5A), a series of reactions occur in the following order: the output voltage of BUCK circuit is reduced, the feedback voltage FB is reduced, and the reference voltage V is reduced REF The difference of the feedback voltage FB increases, the output voltage EAO of the error amplifier increases, and the reference current I increases REF Rising, peak inductor current I PEAK And increasing (when the inductive current is equal to the reference current, the upper tube is turned off, and then the inductive current is decreased, so that the peak value of the inductive current is increased compared with the original peak value due to the increase of the reference current), so that the output average inductive current is increased, and the originally decreased output voltage VO is finally restored to the rated value through closed-loop feedback.
However, the closed-loop feedback requires time to react, and only the output voltage EAO feedback loop of the error amplifier to recover the output voltage VO causes the peak inductor current I PEAK The increase of the load current cannot be timely kept up with the increase of the load current, the undershoot of the output voltage VO (the difference value of the output voltage VO from a rated value to a drop point) is large, the recovery time is long, and the dynamic response is poor.
In order to rapidly increase the inductor current, the present disclosure provides a control circuit that improves the off-load transient response of a buck circuit. Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.
Fig. 5 is a schematic structural diagram of the control circuit 1 for improving the off-load transient response of the buck circuit according to an embodiment of the disclosure. The BUCK circuit is a BUCK circuit as shown in fig. 1, and includes an upper tube and a lower tube. As shown in fig. 5, the control circuit 1 includes: a top tube on control unit 10, configured to obtain a delay mode control signal according to a first reference voltage and a feedback voltage of the voltage reduction circuit, and obtain a top tube on signal according to the delay mode control signal and a duty ratio of the voltage reduction circuit, so as to control a turn-off time of the top tube; a lower tube conduction control unit 20, connected to the upper tube conduction control unit 10, for obtaining a lower tube conduction signal according to the feedback voltage, a second reference voltage and the delay mode control signal to control the conduction time of the upper tube; and the control signal output unit 30 is connected with the upper tube conduction control unit 10 and the lower tube conduction control unit 20, and is used for receiving the upper tube conduction signal and the lower tube conduction signal and outputting a switch control signal PWM to control the connection and the disconnection of the upper tube and the lower tube of the voltage reduction circuit according to the upper tube conduction signal and the lower tube conduction signal.
Further, referring to fig. 6, fig. 6 is a circuit structure diagram of the top-tube-conduction control unit 10 of the control circuit for improving the off-load transient response of the step-down circuit according to an embodiment of the present disclosure. As shown in fig. 6, the upper pipe conduction control unit 10 includes a comparator 101, a delay block 102 and an or gate 103. A positive phase input terminal of the comparator 101 receives the feedback voltage FB, a negative phase input terminal of the comparator 101 receives a first reference voltage TURBO _ REF, and an output terminal of the comparator 101 outputs the delay mode control signal TURBO generated according to the feedback voltage FB and the first reference voltage TURBO _ REF. The delay module 102 is connected TO an output terminal of the comparator 101 and receives the delay mode control signal TURBO, and the delay module 102 selects TO enter a normal delay mode or a reduced delay mode according TO the delay mode control signal TURBO, obtains a reduced delay signal according TO the duty ratio when the delay module 102 selects TO enter the reduced delay mode, and obtains a normal delay signal TO according TO a first preset delay time when the delay module 102 selects the normal delay mode. The or gate 103 is connected TO the delay module 102 and receives the reduced delay signal and the normal delay signal TO as inputs, and the output terminal of the or gate 103 outputs the top tube on signal S1 ON.
Specifically, the first reference voltage includes an upper threshold voltage TURBO _ REF _ HIGH and a lower threshold voltage TURBO _ REF _ LOW, and the delay mode control signal TURBO is at a HIGH level when the feedback voltage FB is less than the lower threshold voltage TURBO _ REF _ LOW and at a LOW level when the feedback voltage FB is greater than the upper threshold voltage TURBO _ REF _ HIGH. The comparator 101 may be a hysteresis comparator, and thus may prevent an erroneous operation caused by a jitter of the first reference voltage TURBO _ REF. It should be noted that the first reference voltage is a voltage preset by those skilled in the art according to practical situations, that is, the upper threshold voltage TURBO _ REF _ HIGH and the lower threshold voltage TURBO _ REF _ LOW are voltages preset by those skilled in the art according to practical situations.
According to an embodiment of the present disclosure, the delay module 102 selects to enter the normal delay mode when the delay mode control signal TURBO is low, and the delay module 102 selects to enter the reduced delay mode when the delay mode control signal TURBO is high.
The delay-reducing signal comprises a first delay signal TD1 and a second delay signal TD2, when the delay module 102 selects to enter the delay-reducing mode, the first delay signal TD1 is obtained according to a second preset delay time if the duty ratio is smaller than a preset value, and the second delay signal TD2 is obtained according to a third preset delay time if the duty ratio is greater than or equal to the preset value, wherein the third preset delay time is smaller than the second preset delay time, and the second preset delay time is smaller than the first preset delay time.
According to an embodiment of the present disclosure, the first preset delay time is a top tube turn-off time calculated by a loop of the control circuit, corresponding to TOFF shown in fig. 3. After entering the normal-delay mode, the delay module 102 waits for the first predetermined delay time count TO end sending the normal-delay signal TO. After entering the delay mode, the delay module 102 may determine whether the duty ratio of the voltage-reducing circuit is smaller than a preset value, and if the duty ratio is smaller than the preset value, the delay module 102 may wait for the second preset delay time count to end and send the first delay signal TD1, even if the first preset delay time count is not ended yet; if the duty ratio is greater than or equal to the predetermined value, the delay module 102 waits for the third predetermined delay time count to end transmitting the second delay signal TD2, even though the first predetermined delay time count and the second predetermined delay time count have not yet ended. It is noted that, no matter the delay module enters the normal delay mode or the reduced delay mode, the first preset delay time, the second preset delay time and the third preset delay time start to count at the same time. Therefore, as long as one delay time count is over, the or gate will receive the delay signal and send an up pipe conducting signal, turning off the down pipe and turning on the up pipe.
According to an embodiment of the present disclosure, referring to the BUCK circuit shown in fig. 1, the duty ratio of the step-down circuit (system) may be obtained by comparing a proportional relationship between the average value of the voltage at the node SW and the power supply voltage using a current mirror.
By entering the reduced delay mode, the off time of the upper tube is reduced and the on time is increased so that the rise of the inductor current can be accelerated. In addition, two different delay times exist in the delay reducing mode, because when the duty ratio of the system is small, namely smaller than a preset value, the rising speed of the inductive current is high, the falling speed is low, and the second preset delay time is set to be longer, so that current overshoot caused by too short delay time can be avoided, and further oscillation of the output voltage is caused. It is noted that, the preset value can be set by a person skilled in the art according to actual situations.
Further, referring to fig. 7, fig. 7 is a circuit structure schematic diagram illustrating the lower tube conduction control unit 20 of the control circuit for improving the off-load transient response of the buck circuit according to an embodiment of the disclosure. The lower tube conduction control unit 20 includes an error amplifier 201, a charging module 202, a reference current generating module 203, and a comparing module 204. The positive phase input terminal of the error amplifier 201 receives the second reference voltage REF, the negative phase input terminal of the error amplifier 201 receives the feedback voltage FB, and the output terminal of the error amplifier 201 outputs a first voltage signal generated according to the second reference voltage REF and the feedback voltage FB. The charging module 202 is connected to the output terminal of the comparator 101 of the upper tube conduction control unit 10 and receives the delay mode control signal TURBO, and the charging module 202 is connected to the output terminal of the error amplifier 201 and determines whether to charge the output terminal of the error amplifier 201 according to the delay mode control signal TURBO to form a second voltage signal EAO. The reference current generationAn input terminal of the module 203 is connected to an output terminal of the error amplifier 201 and receives the second voltage signal EAO, and an output terminal of the reference current generating module 203 outputs a reference current signal I generated according to the second voltage signal EAO REF . The input end of the comparing module 204 is connected to the output end of the reference current generating module 203 and receives the reference current signal I REF The comparing module 204 receives an inductor current feedback signal of the BUCK circuit (BUCK circuit), and the comparing module 204 is configured to compare the reference current signal I REF And the inductor current feedback signal obtains a lower tube conduction signal S2 ON.
Specifically, when the delay block control signal TURBO corresponds to the reduced delay mode, the charging module 202 charges the output terminal of the error amplifier 201 to form the second voltage signal EAO, and when the delay block control signal TURBO corresponds to the normal delay mode, the charging module 202 does not charge the output terminal of the error amplifier 201 and takes the first voltage signal as the second voltage signal EAO. The reference current signal I REF Positively correlated with the second voltage signal EAO. When the current value of the inductor current feedback signal is equal to the reference current signal I REF At the current value of (2), the comparison module 204 generates the lower tube on signal S2 ON.
According to an embodiment of the disclosure, the charging module 202 may include a current source I generating a constant current CHARGE A charging circuit composed of a capacitor and a resistor, and a switch Smos formed of a MOS tube. When the delay block control signal TURBO is high, corresponding to the reduced delay mode, the switch Smos in the charging block 202 is closed and the current source may charge the output terminal of the error amplifier 201. When the delay block control signal TURBO is at a low level, corresponding to the normal delay mode, the switch Smos in the charging block 202 is turned off, and the current source does not charge the output terminal of the error amplifier 201.
When the charging module 202 charges the output terminal of the error amplifier 201, the voltage of the output terminal increases, so that the reference current generating moduleGenerated reference current I REF And is increased. If the reference current I REF If the comparison result is larger, the inductor current compared with the reference current in the comparison module 204 needs a longer time to be equal to the reference current, so that the comparison module can take a longer time to generate the lower tube on signal to turn off the upper tube and turn on the lower tube, thereby prolonging the on time of the upper tube. Therefore, the peak current of the inductor current can be larger, and the average current of the inductor can be larger, so that the output voltage of the voltage reduction circuit can be restored to the rated value more quickly.
According to the embodiment of the present disclosure, the control signal output unit 30 includes an RS flip-flop, an S terminal of the flip-flop is connected to the output terminal of the or gate 103 of the upper tube conduction control unit 10 and receives the upper tube conduction signal S1ON, an R terminal of the flip-flop is connected to the output terminal of the comparison module 204 of the lower tube conduction control unit 20 and receives the lower tube conduction signal S2ON, and a Q terminal of the flip-flop outputs the switch control signal PWM. Therefore, when the flip-flop receives the upper tube conducting signal S1ON, the generated switch control signal turns off the lower tube and turns on the upper tube, and when the flip-flop receives the lower tube conducting signal S2ON, the generated switch control signal turns off the upper tube and turns on the lower tube.
Referring to fig. 8, fig. 8 is a timing diagram illustrating inductor current response under control of a control circuit that improves the turn-off transient response of the buck circuit, according to one embodiment of the present disclosure. As shown in fig. 8, when the step-down circuit output is switched from a light load to a heavy load, the output voltage Vout of the step-down circuit decreases, and thus the feedback voltage FB decreases. When the feedback voltage FB is less than the lower threshold voltage TURBO _ REF _ LOW, the delay module in the upper tube conduction control unit in the control circuit selects to enter the reduction delay mode, so that the turn-off time of the upper tube is reduced, the upper tube is turned on in advance, and the inductor current IL is timely raised. And the output end of the error amplifier can be charged by a charging module in the lower tube conduction control unit when the delay mode is reduced, so that the output voltage EAO is increased, the conduction time of the upper tube is increased, and the inductive current IL is further and rapidly promoted. And when the feedback voltage FB is greater than the upper threshold voltage TURBO _ REF _ HIGH, the inductor current is sufficiently large to enter the normal delay mode. In addition, due to the utilization of the duty ratio, the delay time in the delay mode can be different, so that the oscillation of the output voltage caused by current overshoot due to the fact that the rising speed of the inductive current is high and the falling speed is low under the condition that the duty ratio is extremely small is avoided.
The embodiments of the present disclosure are described in detail above, and the principles and embodiments of the present disclosure are explained herein by applying specific embodiments, and the descriptions of the embodiments are only used to help understanding the method and the core ideas of the present disclosure; meanwhile, for a person skilled in the art, based on the idea of the present disclosure, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present disclosure should not be construed as a limitation to the present disclosure.
It should be understood that the terms "first" and "second," etc. in the claims, description, and drawings of the present disclosure are used for distinguishing between different objects and not for describing a particular order. The terms "comprises" and "comprising," when used in the specification and claims of this disclosure, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the disclosure herein is for the purpose of describing particular embodiments only, and is not intended to be limiting of the disclosure. As used in the specification and claims of this disclosure, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that the term "and/or" as used in the specification and claims of this disclosure refers to any and all possible combinations of one or more of the associated listed items and includes such combinations.
The foregoing detailed description has been provided for the embodiments of the present disclosure, and specific examples have been applied herein to illustrate the principles and implementations of the present disclosure. Meanwhile, a person skilled in the art should, based on the idea of the present disclosure, change or modify the specific embodiments and application scope of the present disclosure. In view of the above, the description is not intended to limit the present disclosure.

Claims (10)

1. A control circuit for improving the off-load transient response of a buck circuit, the buck circuit comprising an upper tube and a lower tube, the control circuit comprising:
the upper tube conduction control unit is used for obtaining a delay mode control signal according to a first reference voltage and the feedback voltage of the voltage reduction circuit and obtaining an upper tube conduction signal according to the delay mode control signal and the duty ratio of the voltage reduction circuit so as to control the turn-off time of the upper tube;
the lower tube conduction control unit is connected with the upper tube conduction control unit and used for obtaining a lower tube conduction signal according to the feedback voltage, a second reference voltage and the delay mode control signal so as to control the conduction time of the upper tube;
and the control signal output unit is connected with the upper pipe conduction control unit and the lower pipe conduction control unit, is used for receiving the upper pipe conduction signal and the lower pipe conduction signal, and controls the switching on and off of the upper pipe and the lower pipe of the voltage reduction circuit according to the upper pipe conduction signal and the lower pipe conduction signal output switch control signal.
2. The control circuit for improving the off-load transient response of the buck circuit as recited in claim 1, wherein the top-tube-conduction control unit comprises a comparator, a delay block, and an or gate; wherein the content of the first and second substances,
a positive phase input terminal of the comparator receives the feedback voltage, a negative phase input terminal of the comparator receives a first reference voltage, and an output terminal of the comparator outputs the delay mode control signal generated according to the feedback voltage and the first reference voltage;
the delay module is connected with the output end of the comparator and receives the delay mode control signal, and the delay module selects to enter a normal delay mode or a reduced delay mode according to the delay mode control signal, when the delay module selects to enter the reduced delay mode, a reduced delay signal is obtained according to the duty ratio, and when the delay module selects the normal delay mode, the normal delay signal is obtained according to a first preset delay time;
the or gate is connected to the delay module and receives the reduced delay signal and the normal delay signal as inputs, and an output terminal of the or gate outputs the upper tube conducting signal.
3. The control circuit for improving the turn-off transient response of a buck circuit as claimed in claim 2, wherein said comparator comprises a hysteretic comparator.
4. The control circuit of claim 2, wherein the first reference voltage comprises an upper threshold voltage and a lower threshold voltage, wherein the delay mode control signal is high when the feedback voltage is less than the lower threshold voltage, and wherein the delay mode control signal is low when the feedback voltage is greater than the upper threshold voltage.
5. The control circuit for improving the turn-off transient response of a buck circuit as in claim 4,
the delay module selects to enter the normal delay mode when the delay mode control signal is low, selects to enter the reduced delay mode when the delay mode control signal is high,
the delay reducing module is used for obtaining a first delay signal according to a first preset delay time if the duty ratio is smaller than a preset value, and obtaining a second delay signal according to a second preset delay time if the duty ratio is larger than or equal to the preset value, wherein the second delay time is smaller than the first delay time.
6. The control circuit for improving the turn-off transient response of a buck circuit as in claim 5,
the lower tube conduction control unit comprises an error amplifier, a charging module, a reference current generation module and a comparison module; wherein the content of the first and second substances,
a positive phase input terminal of the error amplifier receives the second reference voltage, a negative phase input terminal of the error amplifier receives the feedback voltage, and an output terminal of the error amplifier outputs a first voltage signal generated from the second reference voltage and the feedback voltage;
the charging module is connected with the output end of the comparator of the upper tube conduction control unit and receives the delay mode control signal, and the charging module is connected with the output end of the error amplifier and determines whether to charge the output end of the error amplifier according to the delay mode control signal to form a second voltage signal;
the input end of the reference current generation module is connected with the output end of the error amplifier and receives the second voltage signal, and the output end of the reference current generation module outputs a reference current signal generated according to the second voltage signal;
the input end of the comparison module is connected with the output end of the reference current generation module and receives the reference current signal, the comparison module receives an inductive current feedback signal of the voltage reduction circuit, and the comparison module obtains a lower tube conduction signal according to the reference current signal and the inductive current feedback signal.
7. The control circuit for improving the turn-off transient response of a buck circuit as in claim 6,
the charging module charges an output of the error amplifier to form the second voltage signal when the delay module control signal corresponds to the reduced delay mode,
when the delay module control signal corresponds to the normal delay mode, the charging module does not charge the output end of the error amplifier, and takes the first voltage signal as the second voltage signal.
8. The control circuit for improving the off-load transient response of a buck circuit as recited in claim 7, wherein the reference current signal is positively correlated to the second voltage signal.
9. The control circuit for improving the turn-off transient response of a buck circuit as in claim 8,
and when the current value of the inductive current feedback signal is equal to the current value of the reference current signal, the comparison module generates the lower tube conduction signal.
10. The control circuit for improving the off-load transient response of the buck circuit as claimed in claim 8, wherein the control signal output unit comprises an RS flip-flop, an S terminal of the RS flip-flop is connected to an output terminal of an or gate of the up-tube conduction control unit and receives the up-tube conduction signal, an R terminal of the RS flip-flop is connected to an output terminal of a comparison module of the down-tube conduction control unit and receives the down-tube conduction signal, and a Q terminal of the RS flip-flop outputs the switch control signal.
CN202210726806.3A 2022-06-23 2022-06-23 Control circuit for improving load shedding transient response of voltage reduction circuit Pending CN114977761A (en)

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CN202210726806.3A CN114977761A (en) 2022-06-23 2022-06-23 Control circuit for improving load shedding transient response of voltage reduction circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210726806.3A CN114977761A (en) 2022-06-23 2022-06-23 Control circuit for improving load shedding transient response of voltage reduction circuit

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117595617A (en) * 2024-01-18 2024-02-23 成都利普芯微电子有限公司 Transient response control circuit and switching converter

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117595617A (en) * 2024-01-18 2024-02-23 成都利普芯微电子有限公司 Transient response control circuit and switching converter
CN117595617B (en) * 2024-01-18 2024-04-16 成都利普芯微电子有限公司 Transient response control circuit and switching converter

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