CN108155627B - A kind of auxiliary control circuit for low voltage difference BUCK converter - Google Patents

A kind of auxiliary control circuit for low voltage difference BUCK converter Download PDF

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Publication number
CN108155627B
CN108155627B CN201810093272.9A CN201810093272A CN108155627B CN 108155627 B CN108155627 B CN 108155627B CN 201810093272 A CN201810093272 A CN 201810093272A CN 108155627 B CN108155627 B CN 108155627B
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China
Prior art keywords
comparator
buck converter
input terminal
output
input
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CN201810093272.9A
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Chinese (zh)
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CN108155627A (en
Inventor
周泽坤
李响
石旺
石跃
王卓
张波
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators

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

Abstract

A kind of auxiliary control circuit for low voltage difference BUCK converter, belongs to analog circuit technical field of power management.Including first comparator, the second comparator, RS latch and nor gate, the first input end of first comparator and the second input terminal are separately connected the input terminal and output end of BUCK converter；The first input end of second comparator and the second input terminal are separately connected the input terminal and switching node of BUCK converter, and control signal is the inversion signal of the first comparator output signal；The output end of the S input terminal connection first comparator of RS latch, R input connect the output end of the second comparator；Two input terminals of nor gate are separately connected the S input terminal and Q output of RS latch, output end output control signal BUCK converter.Auxiliary control circuit provided by the invention can prevent BUCK converter from entering failure state in input voltage and smaller output voltage difference, ensure that the stability of BUCK converter output voltage.

Description

A kind of auxiliary control circuit for low voltage difference BUCK converter
Technical field
The invention belongs to analog circuit technical field of power management, and in particular to a kind of for low voltage difference BUCK converter Auxiliary control circuit, for carrying out auxiliary control to it after BUCK loop failure.
Background technique
In electric power management circuit field, BUCK converter is a kind of DC-DC converter being in daily use.It is steady with low pressure difference linearity Depressor (LDO) is compared, and BUCK converter efficiency is higher, there is wide commercial value.BUCK uses inductance as energy-storage travelling wave tube, And use two power tubes that inductance is periodically switched between two different charged states；It is fixed using voltage-second balance Reason, under different duty ratios, BUCK can be by output voltage stabilization in different values.
The control method of BUCK is divided into sluggish mould, voltage-mode, current-mode, COT etc..Working frequency can be wherein completely fixed Be voltage-mode and current-mode.Voltage-mode and current-mode BUCK are the partial pressure and fixation by difference amplifier by output voltage Benchmark compares, to obtain a feedback control loop；BUCK circuit is at work adjusted duty ratio automatically according to feedback control loop, Finally obtain a stable output voltage.In general, it is light to improve all to introduce discontinuous operating mode (DCM) for BUCK circuit Working efficiency under carrying.The working principle of DCM is to simultaneously turn off lower power tube in inductive current zero passage, until the next period Start.
For BUCK, transient state jumps the change for meaning duty ratio.It is jumped when overloaded when loading from underloading, output voltage It can decline.Conversely, output voltage can rise, and this there is the excessively high problem of output voltage when heavy duty is jumped at light load.Letter For list, if the input and output voltage pressure difference of BUCK is smaller, the output voltage of BUCK is possible to during load jump Become higher than input voltage, loop may thus be made to enter runaway condition, conventional control failure.Previous scheme is often It is such case to be avoided from design objective, or punching value on output voltage is reduced by transient state enhancing, but arrive current Until, all do not see the circuit arrangement being modified directly against such case.
Summary of the invention
For above-mentioned BUCK converter in low dropout, loop is out of control at light load leads to output voltage for heavy duty jump The problem of substantially vibrating with inductive current, the present invention propose a kind of auxiliary control circuit, for BUCK converter in input and output Pressure difference hour is detected by the comparison to BUCK converter input voltage and output voltage, judges whether system loop is in different Normal state simultaneously turns off down tube, BUCK converter stops working if output voltage is higher than input voltage；Restoring just There are two types of conditions to judge when often work, to guarantee that the circuit can have preferable performance from the heavily loaded underloading or pole of jumping at light load.
The technical solution of the present invention is as follows:
A kind of auxiliary control circuit for low voltage difference BUCK converter, including
First comparator, first input end and the second input terminal are separately connected the input terminal of the BUCK converter and defeated Outlet；
Second comparator, first input end and the second input terminal are separately connected the input terminal of the BUCK converter and open Artis, control signal are the inversion signal of the first comparator output signal；
RS latch, S input terminal connect the output end of the first comparator, R input connection second ratio Compared with the output end of device；
And nor gate, two input terminal are separately connected the S input terminal and Q output of the RS latch, output end Output control signal connects the BUCK converter.
Specifically, the auxiliary control circuit is used for the BUCK converter of DCR sampling, the BUCK conversion of the DCR sampling Device includes DCR capacitor, is additionally provided with short pulse generation circuit between the output end of second comparator and the RS latch, For generating a short pulse signal, input terminal connects the output end of second comparator, on the one hand output signal is used for The DCR capacitor is controlled, the R input of the RS latch is on the other hand connected.
Specifically, being additionally provided with timing circuit, the timing circuit between the first comparator and the RS latch Including shift register and/or door, the clock signal input terminal of the shift register connects clock signal, enable end connection Under-voltage enable signal, D input terminal connect the output end of the first comparator, the first output end Q1 and second output terminal Q2 Described in connection or two input terminals of door, described or door output end connect the S input terminal of the RS latch.
The invention has the benefit that auxiliary control circuit provided by the invention can prevent BUCK converter in input electricity Enter failure state when pressure and smaller output voltage difference, ensure that the stability of BUCK converter output voltage.
Detailed description of the invention
Fig. 1 is a kind of knot of auxiliary control circuit for low voltage difference BUCK converter provided by the invention in embodiment Structure schematic diagram.
Fig. 2 is the configuration diagram of current-mode BUCK converter.
Fig. 3 is the moment timing diagram out of control of BUCK converter.
Fig. 4 is the timing diagram out of control of BUCK converter.
Fig. 5 is that BUCK converter current flows backward schematic diagram.
Fig. 6 is the timing diagram of the BUCK converter after the auxiliary control circuit proposed through the invention is corrected.
Specific embodiment
The invention will be further elaborated with specific embodiment with reference to the accompanying drawing.
Auxiliary control circuit proposed by the present invention, for BUCK converter in low dropout, heavy duty jump underloading Shi Huanlu is out of control to adjust BUCK converter when output voltage and inductive current being caused substantially to vibrate, so that BUCK converter output electricity Press through high loop it is out of control after BUCK system can be stable return to normal operating conditions.
As shown in Figure 1, the present invention includes first comparator, the second comparator, RS latch and nor gate, in order to enable One comparator input common-mode range is met the requirements generally using source level comparator, the first input end of first comparator and second defeated Enter input terminal and output end that end is separately connected BUCK converter；The first input end of second comparator and the second input terminal difference The input terminal and switching node of BUCK converter are connected, control signal is that the reverse phase of the first comparator output signal is believed Number；The output end of the S input terminal connection first comparator of RS latch, R input connect the output end of the second comparator；Or Two input terminals of NOT gate are separately connected the S input terminal and Q output of RS latch, and output end output control signal BUCK turns Parallel operation.
It is illustrated in figure 2 the configuration diagram of current-mode BUCK converter, wherein VINFor supply voltage, that is, BUCK converter Input voltage, VOFor output voltage, VhsFor upper power tube driving voltage, VlsFor lower power tube driving voltage, VSWFor joint Point voltage.It is worth noting that auxiliary control circuit proposed by the present invention is equally applicable to the BUCK converter of voltage-mode pattern. The present invention is described in detail by taking current-mode BUCK converter is using DCR sampling (sampling of inductance parasitic series resistance) as an example below.
It is illustrated in figure 3 the moment timing diagram out of control of BUCK converter, as seen from Figure 3 the electric current under runaway condition The working condition of mould BUCK converter is jumped to underloading in a flash in load from heavy duty, output voltage VORapid increase, inductance Electric current ILRapid decrease.The loop control mode of BUCK converter can be transformed into interrupted control from continuous control mode (CCM) at this time Molding formula (DCM).Under the control of normal intermittent controlled mode DCM, inductive current I in a certain periodLWhen zero passage, BUCK turns Lower power tube can simultaneously turn off in parallel operation, after power tube shutdown, from output capacitance directly to negative in the remaining time in the period Carry power supply.During output capacitance directly powers to the load, output voltage VOIt can decline, inductive current ILZero can be maintained at Near.But if the work of BUCK converter the input and output voltage difference very little the case where, as shown in figure 4, heavy duty jump extremely During underloading, output voltage VOIt can be more than input voltage VIN0.7V or more.In BUCK system, inductive current ILChange It is related with its both ends pressure difference for changing direction, it may be assumed that
As shown in figure 5, the left end voltage of inductance is node voltage V when lower power tube is all closedSW, right end electricity Pressure is output voltage VO.As output voltage VOExceed input voltage VINWhen, inductive current ILIt can flow backward to switching node, charge is logical The parasitic body diode for crossing power tube is released, so the voltage V at switching nodeSWIt will increase input voltage VINIn addition Power tube parasitic body diode forward conduction voltage (about 0.7V), i.e. (VIN+0.7V).At this point, if output voltage VOCompare VIN+ 0.7V is taller, just will appear that intermittent controlled mode DCM is out of control, because can maintain the inductive current I of zero current originallyLIt can be by It is higher than left end voltage in inductance right end voltage and reinforces flowing backward, and as the time is increasing.Until the electric current of reverse irrigation is excessive, Charge in output capacitance is caused quickly to be taken away, output voltage VODrop to VINUntil+0.7V or less.In output voltage VOIt is lower than VINAfter+0.7V, the inductive current I of reverse irrigationLStart to reduce, but still have certain current value, persistently takes away in output capacitance Charge leads to output voltage VOToo low, BUCK loop starts to draw high output voltage V by feedbackO, but lead to output voltage VO It rebounds excessively high, eventually forms long-term waveform out of control shown in Fig. 4.
The auxiliary control circuit proposed in the present embodiment can effectively eliminate above-mentioned runaway condition.Firstly, auxiliary control Circuit be when BUCK converter works normally it is idle, in addition to for judging BUCK converter output voltage VOWith input electricity Press VINThe first comparator of size, other modules are all in off state, to reduce auxiliary control circuit in BUCK converter Overall power consumption when normal work.
Accidentally auxiliary control circuit is triggered in order to prevent, is increased between first comparator and RS latch in the present embodiment Timing circuit, the timing of periodicity can be made of shift register or other structures, and the timing circuit in the present embodiment includes Shift register and/or door, the clock signal input terminal of shift register connect clock signal OSC_clk, and enable end connection is owed Enable signal UVLO is pressed, D input terminal connects the output end of first comparator, and the first output end Q1 and second output terminal Q2 connect It connects or the output end of two input terminals of door or door connects the S input terminal of the RS latch.
When first comparator determines the output voltage V of BUCK converterOContinuously it is higher than input voltage VINSeveral switch weeks After phase, auxiliary control circuit is started to work.Here carrying out timing will not accidentally be touched to guarantee BUCK system in normal work The auxiliary circuit is sent out, is the stability in order to guarantee system, actually if only needing function, timing electricity can be removed Road.
After auxiliary control circuit starts normal work, auxiliary control circuit output control signal connects BUCK converter, So that the lower power tube of BUCK system simultaneously closes off.It is the control signal by dragging down current-mode BUCK in this example, to protect It is continuously off to demonstrate,prove lower power tube, other methods can be used in practice.
While auxiliary control circuit starts to work normally, the second comparator is also started to work, and the comparator is for sentencing Disconnected current over-zero.So that auxiliary control circuit terminates down tube locking state on BUCK converter, there are two judgment basis: 1. second Comparator judges that electric current has been subjected to zero；2. first comparator judges output voltage VOIt returns and drops to input voltage VINBelow.Namely It says, when auxiliary control circuit works, output signal continuously effective, until one of above-mentioned two criterion is satisfied.
It is satisfied if it is first criterion, while current-mode BUCK circuit uses DCR sampling plan, then changing It needs first to generate a short pulse before becoming auxiliary control circuit output signal, is generated by the short pulse generation circuit in Fig. 1.This Short pulse generation circuit is arranged between the output end of the second comparator and RS latch in embodiment, for generating a short pulse Signal, input terminal connect the output end of the second comparator, and on the one hand output signal is used to control DCR capacitor, on the other hand Connect the R input of RS latch.
The short pulse opens the subsequent charge for switching and releasing on DCR sampling capacitance.DCR sampling capacitance CSENSETwo Polar plate voltage is respectively sampled voltage VISNSWith output voltage VO.The purpose for the arrangement is that guarantee the accuracy of DCR sampling, i.e., it is electric Inducing current ILWhen being zero, voltage is also zero on DCR sampling capacitance.After correcting the voltage on sampling capacitance, then make auxiliary control electricity Road output signal becomes invalid.The present embodiment is illustrated using DCR sampling, if sampled without using DCR, does not need this Step；It is satisfied if it is second criterion, is then directly changed auxiliary control circuit output signal, entire auxiliary control circuit stops Only work.
The scheme works timing diagram that this example proposes is as shown in Figure 6.After load jumps, output voltage VOOn quickly It rises, as output voltage VOMore than input voltage VINWhen, auxiliary control circuit is started to work, and lower power tube is turned off.At this time second Comparator is started to work, and detects node voltage V over timeSWDrop to input voltage VINHereinafter, i.e. inductance is electric Flow ILZero passage, then turn off the work of this module, and output restores signal.In load jump, such as 6A to 2A, underloading at this time is opposite It is heavier, then first comparator will detect output voltage V before the second comparator detects current over-zeroOIt drops to Input voltage VINHereinafter, output restores signal in advance.
Key point in the present invention is through the inspection to signal at BUCK circuit input/output signal and switching node It surveys, that whether there is a situation where output voltages at light load is excessively high in heavy duty jump for decision circuitry, and guarantees output using serial of methods What BUCK system can be stable after overtension loop is out of control returns to normal operating conditions.
Those skilled in the art disclosed the technical disclosures can make various do not depart from originally according to the present invention Various other specific variations and combinations of essence are invented, these variations and combinations are still within the scope of the present invention.

Claims (3)

1. a kind of auxiliary control circuit for low voltage difference BUCK converter, which is characterized in that including
First comparator, first input end and the second input terminal are separately connected input terminal and the output of the BUCK converter End；
Second comparator, first input end and the second input terminal are separately connected the input terminal and joint of the BUCK converter Point, control signal are the inversion signal of the first comparator output signal；
RS latch, S input terminal connect the output end of the first comparator, and R input connects second comparator Output end；
And nor gate, two input terminal be separately connected the RS latch S input terminal and Q output, output end it is defeated Control signal connects the BUCK converter out.
2. the auxiliary control circuit according to claim 1 for low voltage difference BUCK converter, which is characterized in that described auxiliary Help control circuit for the BUCK converter of DCR sampling, the BUCK converter of DCR sampling includes DCR capacitor, and described second It is additionally provided with short pulse generation circuit between the output end of comparator and the RS latch, for generating a short pulse signal, Its input terminal connects the output end of second comparator, on the one hand output signal is used to control the DCR capacitor, another party Face connects the R input of the RS latch.
3. the auxiliary control circuit according to claim 1 or 2 for low voltage difference BUCK converter, which is characterized in that institute State and be additionally provided with timing circuit between first comparator and the RS latch, the timing circuit include shift register and/or Door, the clock signal input terminal of the shift register connect clock signal, and enable end connects under-voltage enable signal, and D is defeated Enter the output end that end connects the first comparator, the first output end Q1 connects two described or door with second output terminal Q2 Input terminal, described or door output end connect the S input terminal of the RS latch.
CN201810093272.9A 2018-01-31 2018-01-31 A kind of auxiliary control circuit for low voltage difference BUCK converter Expired - Fee Related CN108155627B (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109742946B (en) * 2019-01-22 2020-08-28 电子科技大学 DCR sampling circuit applied to wide output voltage range Buck converter
CN110299842B (en) * 2019-07-23 2024-02-13 东莞保力电子有限公司 Boost freewheel low pressure differential Buck type switching power supply device
CN111934550B (en) * 2020-07-29 2022-04-01 深圳硕日新能源科技有限公司 Anti-backflow circuit, control method thereof and photovoltaic charging controller

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CN102695328A (en) * 2011-03-23 2012-09-26 松下电器产业株式会社 Lighting device and illumination apparatus
CN105356734A (en) * 2015-11-18 2016-02-24 浙江大学 COT-control-based ripple-compensation-based buck circuit power management chip
CN105515364A (en) * 2016-01-29 2016-04-20 西安电子科技大学 Near-threshold-voltage automatic starting circuit applied to Boost converter
CN106026032A (en) * 2016-05-27 2016-10-12 电子科技大学 Light-load soft shutdown circuit for Buck converter

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JP2012257444A (en) * 2011-05-13 2012-12-27 Rohm Co Ltd Control circuit of step-up switching regulator, switching regulator using the same and electronic apparatus

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
CN102695328A (en) * 2011-03-23 2012-09-26 松下电器产业株式会社 Lighting device and illumination apparatus
CN105356734A (en) * 2015-11-18 2016-02-24 浙江大学 COT-control-based ripple-compensation-based buck circuit power management chip
CN105515364A (en) * 2016-01-29 2016-04-20 西安电子科技大学 Near-threshold-voltage automatic starting circuit applied to Boost converter
CN106026032A (en) * 2016-05-27 2016-10-12 电子科技大学 Light-load soft shutdown circuit for Buck converter

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