CN206432895U - A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM - Google Patents
A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM Download PDFInfo
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- CN206432895U CN206432895U CN201621321644.1U CN201621321644U CN206432895U CN 206432895 U CN206432895 U CN 206432895U CN 201621321644 U CN201621321644 U CN 201621321644U CN 206432895 U CN206432895 U CN 206432895U
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Abstract
The utility model discloses a kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM, including change-over circuit and control circuit, circuit is controlled to include output voltage sampling circuit, PWM control modules, control logic module and drive module, the output termination main switch and the control end of continued flow switch pipe of drive module, PWM control modules include error amplifier, comparator, oscillator and sawtooth wave generating circuit, the first input end of error amplifier connects the output end of output voltage sampling circuit, the second termination reference voltage；The first input end of comparator connects the output end of error amplifier, the output end of the second input termination sawtooth wave generating circuit；The first input end of the output termination control logic module of comparator, the second input of the output termination control logic module of oscillator；The input of the output termination drive module of control logic module.In summary, the utility model determines switching point using the delay of comparator, and simple in construction, chip occupying area is small.
Description
[technical field]
The utility model is related to dc-dc, more particularly to a kind of double mode automatic switchovers of PWM/PFM voltage-dropping type
Dc-dc.
[background technology]
Dc-dc is effective electric pressure converter for exporting fixed voltage after transformation input voltage.Dc-dc point
For three classes：Step-up DC/DC converters, voltage-dropping type DC/DC converters and buck-boost type DC/DC converters.According to demand may be used
Controlled using three classes.PWM control types efficiency high simultaneously has good output voltage ripple and noise.Even if PFM control types are long
Between use, especially small load when have the advantages that power consumption is small.PFM controls are carried out during the small load of PWM/PFM conversion hysterias, and in heavy burden
PWM controls are automatically switched to during load.
Southeast China University Du Fei master thesis《PWM/PFM switches the analysis and design of step-down DC-DC converter》It is situated between
Continued the basic circuit structure and its operation principle and pulse width modulation (Pulse Width of buck mode DC-DC converter
Modulation, PWM) and two kinds of control models of pulse frequency modulated (Pulse Frequency Modulation, PFM), so
System modelling is carried out to DC-DC system afterwards and the transient response characteristic of DC-DC system and the stability of system is analyzed, it is proposed that
The control structure that PWM/PFM automatically switches is realized according to load change.
The structure of conventional PWM/PFM dual-mode step-down type dc-dcs is as shown in figure 1, include current detecting at present
Module, PWM/PFM mode detection modules, PWM control modules, PFM control modules, control logic circuit, driving stage and buffer stage
Circuit.Current detection module detects the electric current of inductance, and changes into voltage VsenseWith the threshold value V of designdesireCompare.As Vsense>
Vdesire, i.e., when inductive current is more than the PWM/PFM pattern breakover currents of setting, PWM mode is selected, by VPWMSignal passes through control
The periodically conducting of logic control main switch is with closing；Conversely, selection PFM patterns, by VPFMSignal passes through control logic control
The conducting and closing of main switch.
The mode switching circuit that traditional PWM/PFM dual-mode step-down types dc-dc is used is complicated, generally relates to
And the control circuit and mode selection circuit of complicated current detection circuit, PWM/PFM pattern detection circuits and both of which,
There is circuit complexity height, the big shortcoming of chip occupying area in current PWM/PFM dual-mode step-down type dc-dcs.
[content of the invention]
The technical problems to be solved in the utility model is to provide a kind of small PWM/PFM of simple in construction, chip occupying area
The buck mode DC-DC converter of double mode automatic switchover.
In order to solve the above-mentioned technical problem, the technical solution adopted in the utility model is that a kind of PWM/PFM is double mode automatic
The buck mode DC-DC converter of switching, including change-over circuit and control circuit, change-over circuit include main switch, continued flow switch
Pipe, energy storage inductor and output filter capacitor；Circuit is controlled to include output voltage sampling circuit, PWM control modules, control logic mould
Block and drive module, two output ends of drive module connect the control end of main switch and the control end of continued flow switch pipe respectively,
PWM control modules include error amplifier, comparator, oscillator and sawtooth wave generating circuit, the first input of error amplifier
Terminate the output end of output voltage sampling circuit, the second termination reference voltage；The first input end of comparator connects error amplifier
Output end, second input termination sawtooth wave generating circuit output end；The of the output termination control logic module of comparator
One input, the second input of the output termination control logic module of oscillator；The output termination driving of control logic module
The input of module.
Above-described buck mode DC-DC converter, control logic module include NAND gate basic RS filpflop, with it is non-
Door, nor gate and two NOT gates；The first input end of the output termination NAND gate of oscillator, nor gate is connect by the first NOT gate
First input end, the second input of NAND gate is connect by the second NOT gate；The output of second input termination comparator of nor gate
End, the first input end of the output termination NAND gate basic RS filpflop of nor gate, the output termination NAND gate of NAND gate is basic
Second input of rest-set flip-flop, the output end of NAND gate basic RS filpflop is terminated as the output of control logic module to be driven
The input of module.
Above-described buck mode DC-DC converter, the first termination positive source of main switch, the second termination afterflow are opened
Close the first end of pipe, the second end ground connection of continued flow switch pipe；Second end of the first termination main switch of energy storage inductor, energy storage electricity
The first end of second termination output filter capacitor of sense, the second end ground connection of output filter capacitor；Make at second end of energy storage inductor
Output voltage sampling circuit is connect for the cathode output end of buck mode DC-DC converter.
Buck mode DC-DC converter double mode PWM/PFM of the present utility model utilizes the comparator in PWM control modules
Propagation delay realize the double mode automatic switchovers of PWM/PFM, transferred electricity when inductive current is more than default PWM/PFM patterns
Stream, dc-dc works in PWM mode, on the contrary then work in PFM patterns.With traditional buck mode DC-DC converter phase
Than without circuits such as complicated current detecting, PWM/PFM mode detections, Schema control, model selections, but utilizing comparator
Propagation delay determine PWM/PFM mode switch points, the seamless of PWM/PFM patterns realized by simple control logic circuit
Automatically switch, simple in construction, chip occupying area is small.
[brief description of the drawings]
The utility model is described in further detail with reference to the accompanying drawings and detailed description.
Fig. 1 is the theory diagram of prior art PWM/PFM pattern buck mode DC-DC converters.
Fig. 2 is the principle frame of the buck mode DC-DC converter of the double mode automatic switchovers of the utility model embodiment PWM/PFM
Figure.
Fig. 3 is the theory diagram of the utility model embodiment PWM control modules.
Fig. 4 is the schematic diagram of the control logic circuit of the utility model embodiment.
Fig. 5 is the control signal oscillogram under the heavy duty of the utility model embodiment buck mode DC-DC converter.
Fig. 6 is the control signal oscillogram under the utility model embodiment buck mode DC-DC converter underloading.
Fig. 7 is the utility model embodiment buck mode DC-DC converter I under PFM patternsL、VO、VFBOscillogram.
Fig. 8 is the utility model embodiment buck mode DC-DC converter corresponding inductive current under different loads electric current
The comparison diagram of waveform.
[embodiment]
Structure such as Fig. 2 of the buck mode DC-DC converter of the double mode automatic switchovers of the utility model embodiment PWM/PFM is extremely
Shown in Fig. 4, including change-over circuit and control circuit, change-over circuit include main switch (main metal-oxide-semiconductor) MP, continued flow switch pipe MN, storage
Can inductance L, output filter capacitor C and resistance RESR。
Circuit is controlled to include by resistance R1With resistance R2The output voltage sampling circuit that is composed in series, PWM control modules, control
Logic module and drive module (drive circuit) processed.
Main switch MPThe first termination positive source VIN, the second termination continued flow switch pipe MNFirst end, continued flow switch
Pipe MNThe second end ground connection VSS.Energy storage inductor L the first termination main switch MPThe second end LX, energy storage inductor L the second end
Pass through resistance RESRConnect output filter capacitor C first end, output filter capacitor C the second end ground connection.
Energy storage inductor L the second end meets load resistance R as the cathode output end of buck mode DC-DC converterL, connect simultaneously
The input V of output voltage sampling circuitO。
PWM control modules include band-gap reference, error amplifier, comparator, oscillator and sawtooth wave generating circuit.
The first input end of error amplifier meets the output end V of output voltage sampling circuitFB, the second termination reference voltage
VREF.The first input end of comparator connects the output end of error amplifier, the output of the second input termination sawtooth wave generating circuit
End.The first input end of the output termination control logic module of comparator, the of the output termination control logic module of oscillator
Two inputs.The input of the output termination drive module of control logic module.
Control logic module includes NAND gate basic RS filpflop, NAND gate, nor gate and two NOT gates；Oscillator it is defeated
Go out to terminate the first input end of NAND gate, the first input end of nor gate connect by the first NOT gate, by the second NOT gate connect with it is non-
Second input of door；The output end of second input termination comparator of nor gate, the output termination NAND gate of nor gate is basic
The first input end of rest-set flip-flop, the second input of the output termination NAND gate basic RS filpflop of NAND gate, NAND gate base
The output end of this rest-set flip-flop terminates the input of drive module as the output of control logic module.Wherein, the second NOT gate and
NAND gate constitutes the rising edge detection circuit of oscillator output signal.
Two output ends of drive module meet main switch M respectivelyPControl end and continued flow switch pipe MNControl end.
As shown in figure 4, control logic module set signal S be " 0 " when, set signal effectively, no matter reset signal R why
Value, rest-set flip-flop is all by output signal VDRIVEIt is set to " 1 "；Only when R for " 0 " and also S be " 1 " when, i.e. reset signal is effective, and
During set invalidating signal, rest-set flip-flop could be by output signal VDRIVEIt is reset to " 0 ", it can be seen that be set to signal S priority
Higher than reset signal R.As the output signal V of PWM control modulesPWMFor " 1 " or VOSCDuring for " 0 ", set signal S is " 0 ", set
Signal is effective, the output signal V of control logic moduleDRIVE" 1 " is set to, main PMOS M is closed by drive moduleP.Work as control
The set signal S of logic module is invalid and VOSC rising edges detect electric circuit inspection to VOSCRising edge when, reset signal R is
" 0 ", reset signal is effective, the output signal V of control logic moduleDRIVE" 0 " is set to, main PMOS is opened by drive module
MP。
The master control signal waveform such as Fig. 5 of the utility model embodiment buck mode DC-DC converter under different loads
With shown in Fig. 6.The waveform of master control signal when Fig. 5 gives heavy duty, in Figure 5 sawtooth waveforms VRAMPExported with error amplifier
Signal VCThe intersection point moment be respectively t1、t3, and due to the propagation delay t of comparatordInfluence, the output V of comparatorPWMOccur
It is respectively t at the time of saltus step2、t4, t is compared respectively1、t3Delay time period td。VPWMIn t2The saltus step that " 0 " arrives " 1 " occurs for the moment,
By VDRIVEIt is set to " 1 ", closes main PMOS MP.Due to t4In VOSCRising edge time trBefore, trMoment set signal S is invalid,
Reset signal R is effective, therefore in trMoment VDRIVE" 0 " is set to, main PMOS M is openedP.Now dc-dc works in PWM
Pattern.
The waveform of master control signal when Fig. 6 gives underloading.The load current I exported when dc-dcLOADReduce
When, the output voltage V of error transformerCIt is kept approximately constant, until ILOADDrop to be continuously turned on discontinuous conducting border,
Error transformer output voltage VCJust begin to decline, to adjust MPON time.Work as ILOADIt is decreased to the turnover of PWM/PFM patterns
Below electric current, VCConstantly reduction, causes VDRIVEIt is output as " 1 " in continuous a period of time, closes main PMOS MP。
Because t4In VOSCRising edge time trAfterwards, trMoment reset signal R is effective, but set signal S is also effective simultaneously,
The set priority class of traffic is high, therefore in trMoment VDRIVEIt is set to " 1 ", closes main PMOS MP, enter skip cycle mode.
Once as shown in fig. 7, the output voltage V of converterODrop to setting value VO_SPECUnder when, the output of converter
The detected value V of voltageFBIt is lower than reference voltage VREF, cause the output voltage V of error amplifierCRise, until opening main PMOS
Pipe MP.M is opened every timePThe peak point current I of induction charging is given afterwardsPEAKThe output voltage V of converter can be maintainedOIn several cycles
It is higher than setting value V in timeO_SPEC, cause VCDecline and close main PMOS M in this periodP, now dc-dc work
In PFM patterns.
The control logic circuit of automatic switchover is to allow VOSCUpper jump along being used as main PMOS MPOpen signal, and allow VPWM
The high level period or VOSCThe low level period be used as MPThe closing period.When dc-dc work in heavy load current or
Under conditions of middle load current, although have the propagation delay t of comparatordInfluence, but delay after comparator output VPWM
The high level period be not covered with VOSCUpper jump edge, therefore each cycle can open main PMOS MP, the working frequency of converter
Constant, PWM module adjusts dutycycle according to load current, as shown in Figure 5.When dc-dc works in light load currents bar
Under part, VCConstantly decline, due to the propagation delay t of comparatordInfluence, the output V of the comparator after delayPWMHigh level when
Section can cover VOSCUpper jump edge, as shown in Figure 6 so that main PMOS MPIt is not that can open in each cycle, but passes through several
After cycle closes, VODrop to design load VO_SPECUnder, cause VCRise, VPWMThe high level period be not covered with VOSCIt is upper
Edge is jumped, so as to be again turned on efferent duct MP, as shown in Figure 7.Now the working frequency of converter reduces, into skip cycle mode,
Namely PFM patterns.
In summary, PWM mode is divided into according to load is continuously turned on turning on two kinds of situations with discontinuous, when converter is in
During continuous conduction mode, heavy load current I as shown in Figure 8LOAD1In the case of, the working frequency of converter is constant, simply root
It is adjusted according to output voltage and opens main metal-oxide-semiconductor MPTime, that is, the dutycycle (D) often said, D=VO/VIN, and V hereinO,
VINAll it is definite value, then dutycycle D is constant.If now output current changes, such as load current ILOADIncrease, can cause
VOMoment reduce that (inductance moment provides increased electric current without normal load, and now discharged by electric capacity provides increased to load
Electric current, causes VODecline), then VOVoltage V after being sampled by sampling resistorFBDecline, put by the error in PWM control modules
After big device, V is exportedCVoltage rises, by comparator and VRAMPAfter comparing, make VPWMHigh level time shorten, allow VDRIVE's
Low level time is elongated, that is, power supply VINIt is elongated to the output loading charging interval by inductance, allow on the average current of inductance
Rise, until balancing after stable state, VCValue before returning to, is kept approximately constant, VDRIVEDutycycle recover to VO/VIN, and now
Inductive current average value added., whereas if load current ILOADReduce, then by the adjustment of PWM control modules,
Power supply VINThe output loading charging interval is shortened by inductance, allows the average current of inductance to decline, until balancing after stable state, VCIt is extensive
It is multiple to be worth to former, it is kept approximately constant, VDRIVEDutycycle recover to VO/VIN, and inductive current average value now is reduced.
If load current ILOADContinue to be reduced to discontinuous conduction mode, middle load current I as shown in Figure 8LOAD2's
In the case of, the working frequency of converter is constant, VCIt can begin to decline, make dutycycle with ILOADReduction and reduce, to ensure one
Average inductor current in cycle is equal to load current ILOAD。
Work as ILOADIt is decreased to below PWM/PFM pattern breakover currents, light load currents I as shown in Figure 8LOAD3Situation
Under, VCIt can constantly reduce, cause VDRIVEIt is output as " 1 " in continuous a period of time, closes main metal-oxide-semiconductor MP, cause the work of converter
Working frequency reduces, into skip cycle mode, that is, PFM patterns, and the working frequency and the size of load current of converter
It is directly proportional.
The buck mode DC-DC converter for having PWM/PFM double mode that the utility model above example is proposed utilizes PWM
The propagation delay of comparator in control module realizes the double mode automatic switchovers of PWM/PFM, when inductive current be more than it is default
PWM/PFM pattern breakover currents, dc-dc works in PWM mode, on the contrary then work in PFM patterns, the utility model with
Upper embodiment is compared with traditional buck mode DC-DC converter, without complicated current detecting, PWM/PFM mode detections, pattern
The circuits such as control, model selection, but PWM/PFM mode switch points are determined using the propagation delay of comparator, by simple
Control logic circuit realize the seamless automatic switchovers of PWM/PFM patterns, simple in construction, chip occupying area is small；It can also lead to
The adjustment comparator propagation delay time is spent to control the size of PWM/PFM pattern turning point electric currents.
Claims (3)
1. a kind of buck mode DC-DC converter of the double mode automatic switchovers of PWM/PFM, including change-over circuit and control circuit, turn
Changing circuit includes main switch, continued flow switch pipe, energy storage inductor and output filter capacitor；Circuit is controlled to be sampled including output voltage
Circuit, PWM control modules, control logic module and drive module, two output ends of drive module connect main switch respectively
The control end of control end and continued flow switch pipe, it is characterised in that PWM control modules include error amplifier, comparator, oscillator
And sawtooth wave generating circuit, the first input end of error amplifier connects the output end of output voltage sampling circuit, the second termination base
Quasi- voltage；The first input end of comparator connects the output end of error amplifier, and the second input terminates the defeated of sawtooth wave generating circuit
Go out end；The first input end of the output termination control logic module of comparator, the output termination control logic module of oscillator
Second input；The input of the output termination drive module of control logic module.
2. buck mode DC-DC converter according to claim 1, it is characterised in that control logic module includes NAND gate
Basic RS filpflop, NAND gate, nor gate and two NOT gates；The first input end of the output termination NAND gate of oscillator, passes through
First NOT gate connects the first input end of nor gate, and the second input of NAND gate is connect by the second NOT gate；The second of nor gate is defeated
Enter to terminate the output end of comparator, the first input end of the output termination NAND gate basic RS filpflop of nor gate, NAND gate
Second input of output termination NAND gate basic RS filpflop, the output end of NAND gate basic RS filpflop is used as control logic
The input of the output termination drive module of module.
3. buck mode DC-DC converter according to claim 1, it is characterised in that the first termination power of main switch
The first end of positive pole, the second termination continued flow switch pipe, the second end ground connection of continued flow switch pipe；First termination master of energy storage inductor opens
Close the second end of pipe, the first end of the second termination output filter capacitor of energy storage inductor, the second end ground connection of output filter capacitor；
Second end of energy storage inductor connects output voltage sampling circuit as the cathode output end of buck mode DC-DC converter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201621321644.1U CN206432895U (en) | 2016-12-05 | 2016-12-05 | A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201621321644.1U CN206432895U (en) | 2016-12-05 | 2016-12-05 | A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM |
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| CN206432895U true CN206432895U (en) | 2017-08-22 |
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| CN201621321644.1U Withdrawn - After Issue CN206432895U (en) | 2016-12-05 | 2016-12-05 | A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106787719A (en) * | 2016-12-05 | 2017-05-31 | 深圳信息职业技术学院 | A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM |
| CN109067151A (en) * | 2018-09-26 | 2018-12-21 | 东莞华贝电子科技有限公司 | A kind of driving voltage dynamic regulating circuit and driving voltage dynamic adjusting method |
| CN114094826A (en) * | 2021-09-10 | 2022-02-25 | 珠海智融科技股份有限公司 | Method, system, equipment and medium for improving efficiency of buck-boost controller |
| CN114421765A (en) * | 2022-02-21 | 2022-04-29 | 上海先楫半导体科技有限公司 | Control system and method of DC-DC converter and DC-DC converter |
| TWI796077B (en) * | 2021-05-19 | 2023-03-11 | 瑞鼎科技股份有限公司 | Method and circuit of automatic mode-switching for dc-dc converter |
-
2016
- 2016-12-05 CN CN201621321644.1U patent/CN206432895U/en not_active Withdrawn - After Issue
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106787719A (en) * | 2016-12-05 | 2017-05-31 | 深圳信息职业技术学院 | A kind of voltage-dropping type DC DC converters of the double mode automatic switchovers of PWM/PFM |
| CN106787719B (en) * | 2016-12-05 | 2023-07-04 | 深圳信息职业技术学院 | PWM/PFM dual-mode automatic switching buck DC-DC converter |
| CN109067151A (en) * | 2018-09-26 | 2018-12-21 | 东莞华贝电子科技有限公司 | A kind of driving voltage dynamic regulating circuit and driving voltage dynamic adjusting method |
| TWI796077B (en) * | 2021-05-19 | 2023-03-11 | 瑞鼎科技股份有限公司 | Method and circuit of automatic mode-switching for dc-dc converter |
| CN114094826A (en) * | 2021-09-10 | 2022-02-25 | 珠海智融科技股份有限公司 | Method, system, equipment and medium for improving efficiency of buck-boost controller |
| CN114421765A (en) * | 2022-02-21 | 2022-04-29 | 上海先楫半导体科技有限公司 | Control system and method of DC-DC converter and DC-DC converter |
| CN114421765B (en) * | 2022-02-21 | 2022-11-29 | 上海先楫半导体科技有限公司 | Control system and method of DC-DC converter and DC-DC converter |
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